Conservapedia - User contributions [en]

E=mc²

2016-09-10T18:03:07Z

Harryk: Added another link to see Also section

'''E=mc²''' asserts that the energy ('''E''') which makes up the [[matter]] in an unmoving object is equal to the square of the [[speed of light]] ('''c²''') times the [[mass]] ('''m''') of that body.<ref>"Energy and mass are linked in the most famous relationship in physics: E = mc². (The energy content of a body is equal to the mass of the body times the speed of light squared.)" [http://www.pbs.org/wgbh/nova/physics/einstein-genius-among-geniuses.html Einstein: Genius Among Geniuses] - PBS's NOVA</ref> The complete form, when applied to moving objects, is '''E²=(mc²)²+(pc)²''', where '''p''' represents momentum,<ref>http://www.youtube.com/watch?v=NnMIhxWRGNw</ref> It is a statement that purports to relate all [[matter]] to [[energy]]. In fact, no [[theory]] has successfully unified the [[law]]s governing [[mass]] (''i.e.'', [[gravity]]) with the laws governing light (''i.e.'', [[electromagnetism]]), and numerous attempts to derive '''E=mc²''' from first principles have failed.<ref name="wvarticles">Five lectures at Wikiversity. The 4th one derives the formula, using the assumptions in the "What the Equation Means" section.
*[http://en.wikiversity.org/wiki/Special_relativity/space,_time,_and_the_Lorentz_transform Lecture 1]
*[http://en.wikiversity.org/wiki/Special_relativity/momentum Lecture 2]
*[http://en.wikiversity.org/wiki/Special_relativity/energy Lecture 3]
*[http://en.wikiversity.org/wiki/Special_relativity/E_%3D_mc%C2%B2 Lecture 4]
*[http://en.wikiversity.org/wiki/Special_relativity/spacetime_diagrams_and_vectors Lecture 5]</ref> [[Politics|Political]] pressure, however, has since made it impossible for anyone pursuing an academic career in [[science]] to even question the validity of this nonsensical [[equation]]. '''''Simply put, E=mc² is [[liberal claptrap]]'''''.

The formula asserts that the mass of an object, at constant energy, magically varies precisely in inverse proportion to the square of a change in the speed of light over time,<ref>http://www.livescience.com/29111-speed-of-light-not-constant.html</ref> which violates [[conservation of mass]] and disagrees with commonsense.<ref>The formula asserts that the mass of an object has energy associated with it, even when it is not moving (p=0). The formula asserts a relationship between the rest mass of an object, its energy and the speed of light. According to the formula, the apparent mass of an object depends on its energy and so [[conservation of mass]] is not satisfied. Instead, relativity proposes that the total energy of a [[closed system]] is conserved, when we "convert" the masses into energies using this formula.</ref>

Physicists have never been able to unify light with matter<ref>Quantum Electrodynamics describes how matter interacts with matter, the standard model of particle physics describes how matter (fermions) interact with bosons (force carriers) for the electromagnetic, strong and weak forces. To date, no theory has been proven to unify gravity with electromagnetism.</ref>despite more than a billion-dollars-worth of attempts, and it is likely impossible to ever do so.<ref>Much of 20th century physics has centered around the interactions between photons (light) and fermionic matter, and much more than a billion dollars has been spent on this. But that doesn't imply that they have been "unified".</ref> [[Biblical Scientific Foreknowledge]] predicts that there is no unified theory of light and matter because they were created at different times, in different ways, as described in the [[Book of Genesis]].

[[Mass]] is a measure of an object's inertia, in other words its resistance to acceleration. In contrast, the intrinsic [[energy]] of an object (such as an [[atom]]) is a function of electrostatic charge and other non-inertial forces, having nothing to do with gravity. Declaring the object's energy to be a function of inertia rather than electrostatics is an absurd and impossible attempt to unify the forces of nature, contrary to the accepted view (as predicted by [[Biblical Scientific Foreknowledge]]) that the forces of nature have not been unified. Liberal scientists assert the formula E=mc² is not limited to nuclear reactions; it applies to chemical reactions and even to the energy stored in a compressed spring.<ref>http://www.newton.dep.anl.gov/askasci/phy99/phy99140.htm</ref>

The claim that '''E=mc²''' has never yielded anything of value and it has often been used as a redefinition of "[[energy]]" for pseudo-scientific purposes by non-scientific journals. Claims can be found not only on liberal, second-tier college websites but at those of [[Baylor]] and the [[MIT]] that the equation is used in [[nuclear power]] generation and [[nuclear weapon]]s ([[nuclear fusion]] and [[nuclear fission]]) and about [[antimatter]].<ref>[http://www.pitt.edu/~jdnorton/teaching/HPS_0410/chapters/E=mcsquared/index.html John D. Norton ''Einstein for everyone - E=mc²''], Department of History and Philosophy of Science University of Pittsburgh</ref><ref>[http://hyperphysics.phy-astr.gsu.edu/hbase/relativ/releng.html Rod Nave ''HpyerPhysics - Relativistic Energy''], Georgia State University</ref><ref>[http://www.pbs.org/wgbh/nova/physics/legacy-of-e-equals-mc2.html Peter Tyson ''The Legacy of E=mc²''] October 11, 2005. PBS ''NOVA''.</ref>

The [[Theory of Relativity]] has never been able to mathematically derive '''E=mc²''' from first principles,<ref name="wvarticles"/> and a physicist observed in a peer-reviewed paper published in 2011 that "Leaving aside that it continues to be affirmed experimentally, a rigorous proof of the mass-energy equivalence is probably beyond the purview of the special theory."<ref>[http://adsabs.harvard.edu/abs/2011AmJPh..79..591H Eugene Hecht: ''How Einstein confirmed E0=mc²'', American Journal of Physics, Volume 79, Issue 6, pp. 591-600 (2011)]</ref> Nevertheless, Robert Dicke - one of the most accomplished American-born physicists and experimental physicists in history - found it unlikely that the equivalence was wrong.<ref>R. H. Dicke "The Theoretical Significance of Experimental Relativity", Gordon and Breach, 1964</ref>

It has been known for a long time that radiation has a mass equivalence, which was correctly derived by [[Henri Poincaré]] in 1904,<ref>[http://www.opticsinfobase.org/josa/abstract.cfm?uri=josa-42-8-540 Herbert E. Ives ''Derivation of the Mass-Energy Relation'', JOSA, Vol. 42, Issue 8, pp. 540-543 (1952)]</ref> but the equation '''E=mc²''' makes a claim far beyond that limited circumstance:

{{cquote|The equality of the mass equivalent of radiation to the mass lost by a radiating body is derivable from Poincaré’s momentum of radiation (1900) and his principle of relativity (1904).|||[[Herbert Ives]], 1952}}


== Description for the layman ==

The equation is extremely famous, and just as extremely misunderstood, in popular culture. Among the more outlandish claims are statements to the effect that "E=mc² holds the secret of the atomic bomb."<ref>Not so. The energy of the atomic bomb comes not from E=mc², but from the tension between the electrostatic force and the strong nuclear force. E=mc² simply meant that the fission products from the [[Little Boy|Hiroshima]] bomb weighed 0.7 grams less than the original Uranium.</ref>
[[Image:600px-Albert Einstein Head.jpg|thumbnail|right|200px|
*"I do not share the crusading spirit of the professional [[Atheism|atheist]] whose fervor is mostly due to a painful act of liberation from the fetters of religious indoctrination received in youth. I prefer an attitude of humility corresponding to the weakness of our intellectual understanding of nature and of our own being." - [[Albert Einstein]]<ref name="Isaacson390">Isaacson, Walter (2008). [http://books.google.com/books?id=cdxWNE7NY6QC&pg=PT390 ''Einstein: His Life and Universe''] (New York: Simon and Schuster), p. 390. Retrieved from GoogleBooks archive on February 19, 2015.</ref>]]
The equation has acquired something of a "cult" status. In the USA, the popular ''[[Twilight Zone]]'' series featured '''E=mc²''' prominently, giving the equation greater currency with the public. The song ''[[Albert Einstein|Einstein]] A Go-Go'' by the band Landscape had a similar effect in the UK in the 1980s. The equation was the title of a single by ''Big Audio Dynamite'' in 1985, and an album by Mariah Carey in 2008. Some movies have been themed on this equation.<ref>http://www.imdb.com/title/tt0322120/?ref_=fn_tt_tt_2, http://www.imdb.com/title/tt0116160/?ref_=fn_tt_tt_1</ref> The equation, along with a picture of a mushroom cloud and a picture of [[Albert Einstein]], were featured on the front cover of an issue of ''Time'' magazine in 1946. All of this is disappointing when one considers how few people actually understand what the equation is saying.

A number of science writers—both serious scientists and science popularizers—have at various times written their own explanation of the equation. Some of these are helpful; many are not. One of the better ones, though not without its share of nonsense, is a NOVA series by the [[Public Broadcasting Service]]<ref>[http://www.pbs.org/wgbh/nova/physics/ancestors-einstein.html David Bodanis ''Ancestors of E=mc²''], Nov 10, 2005, NOVA</ref>

In 2005 The PBS NOVA series also asked 10 physicists to describe the equation in layman's terms.<ref>[http://www.pbs.org/wgbh/nova/einstein/experts.html Lexi Krock, David Levin (editors) ''E=mc² explained'', June, 2005. PBS ''NOVA'']</ref> Here is a sample of five of the statements:
{{cquote|''It's something that doesn't happen in your kitchen or in everyday life.''|||[[Neil deGrasse Tyson]], Astrophysicist, American Museum of Natural History}}{{cquote|''When an object emits light, say, a flashlight, it gets lighter.''|||Sheldon Glashow, Theoretical Physicist and Nobel Laureate, Boston University}}{{cquote|''Things that seem incredibly different can really be manifestations of the same underlying phenomena.''|||Nima Arkani-Hamed, Theoretical Physicist, Harvard University}}{{cquote|''You can get access to parts of nature you have never been able to get access to before.''|||Lene Hau, Experimental Physicist, Harvard University}}{{
cquote|''It certainly is not an equation that reveals all its subtlety in the few symbols that it takes to write down.''|||Brian Greene Theoretical Physicist Columbia University}}

Of these, only the Sheldon Glashow quote makes a specific and meaningful statement about what the equation means.

== What the Equation Means ==
The equation is about energy, both kinetic energy and potential energy.

Kinetic energy is actual visible energy, that is, energy of things that are in motion. It's the energy of a thrown baseball. Radiation (for example, light) also counts as kinetic energy—it's the motion of photons. Light carries energy, force, and momentum. The force carried by light is not as obvious as the force of a thrown baseball, but it is there. The force of sunlight has been proposed for long-term space travel. It is also the force that causes the [[Pioneer anomaly]] and the force that makes a comet's tail stream away from the Sun.

Potential energy is the other kind—"hidden" energy. It can become kinetic energy, or vice-versa. A wound up spring, a charged battery, a stretched rubber band, a mixture of gasoline and air, an explosive, and a radioactive atom, all have potential energy. It's what is needed to make the principle of conservation of energy work. That is, when kinetic energy comes into existence, it's because potential energy was converted into kinetic energy. The wound-up spring of a clock has potential energy, that runs down over time, being converted into the kinetic energy of the ticking sound. A battery has potential energy that runs down when it provides electricity to make things move. Various chemical substances have characteristic amounts of potential energy, that may be converted to or from kinetic energy when chemical reactions occur. For example, Sodium and Chlorine have more potential energy than Sodium Chloride. Explosives have more potential energy than their constituent atoms. Radioactive atoms have more potential energy than their "daughter" atoms.

The principle of ''conservation of energy'', universally accepted for well over 100 years, says

::Total energy (kinetic + potential) is always conserved.

Hundreds of years of research by chemists (and, before that, the alchemists) worked out the potential energies that are characteristic of various substances, and that the potential and kinetic energies are accurately converted from one to the other, leading to the principle of conservation of total energy.

An interesting fact is that, normally, one considers only ''changes'' in potential energy; one doesn't need an absolute scale. A rock at the top of a hill has more potential energy than after it rolls to the bottom of the hill, but the energy at the bottom isn't necessarily zero. We could dig a hole and let it roll down farther, with its energy going negative. Only changes matter. Now it turns out that, once one accepts the implications of E=mc², one ''could'' assign an absolute potential energy to something—its mass times c², and changes in potential emergy would work out correctly because of the mass changes. But that isn't necessary, and, in any case, it would require accepting E=mc² and would therefore be getting ahead of the story.

With those preliminaries out of the way, it is possible to give a concise explanation of what the equation means:

::'''Potential energy has mass.'''

That is, it weighs something. Whenever anything has potential energy of any kind in it, improbable as this may sound, it weighs more. The proportionality constant is 1/c2, or 1.11 x 10−17 kilograms per joule. A fresh battery weighs more than a spent one, a wound-up alarm clock weighs more than a run-down one, etc.

Now that's way too small to measure for anything other than nuclear reactions, which is why it escaped everyone's notice for so long. But it has been measured and experimentally verified for nuclear transformations all across the periodic table.

:There's an interesting parallel with heat. Before the rise of thermodynamics, it was believed that heat was a "substance". That substance was called "caloric". When heat travels from one body to another, what was really happening was presumed to be a transfer of caloric. Much effort was put into measuring the mass of this mysterious "substance". It was always found to be zero, and we now know that what is actually being transferred is thermal energy. So it is not unheard-of to assign mass to intangible properties.

The nonzero mass of potential energy, and the equation E=mc², were determined on theoretical grounds, before any experimental observations were made. The logic of this follows from these assumptions:

#Galilean and Newtonian mechanics.
#Galilean relativity, that is, the notion that there is no absolute frame of reference.
#Conservation of energy.
#Conservation of momentum. (So far this is just classical physics.)
#The universality of the speed of light. (That is, special relativity.)

Keep in mind that, under special relativity, it's not just space and time that need to be redefined. The definitions of momentum and energy need to change also. This is necessary so that the '''conservation of energy and of momentum will be absolutely precise in all circumstances.'''

Under classical Newtonian mechanics, the momentum and kinetic energy of a moving mass are
:<math>p = mv\,</math>
and
:<math>E = \frac{1}{2}mv^2\,</math>
respectively. But under special relativity they are
:<math>p = \frac{mv}{\sqrt{1 - v^2/c^2}}\,</math>
and
:<math>E = mc^2\left(\frac{1}{1 - v^2/c^2} - 1\right)\,</math>
One can verify that, in the non-relativistic limit, the relativistic values converge to the classical ones.

It is this requirement, and some "gedanken experiments" involving conversion between potential and kinetic energy, that lead to E=mc².<ref name="wvarticles"/> These experiments involve some kind of object that isn't moving (though there might be internal motion that doesn't figure in the experiment) and therefore has no kinetic energy and only potential energy, turning into some things that have kinetic energy. The requirements of strict conservation of total momentum and total energy prove the equation.

Einstein's famous derivation<ref name="einstein1905b">[http://www.fourmilab.ch/etexts/einstein/E_mc2/www/ "Does the Inertia of a Body Depend its Energy Content?" Albert Einstein, Sept 1905]</ref> involved light instead of tangible objects, but the result is the same.

==History of Experimental Verification==
Because the change in mass arising from a given release of energy is so small (<math>1/c^2</math>, which 1.11 x 10−17 kilograms per joule), it is essentially impossible to check this equation for normal processes. For example, a flashlight battery loses about 1 picogram of mass when it discharges, and the resultant atoms from the detonation of 1 kilogram of TNT weigh 47 nanograms less than the TNT. Even if all the particles of smoke and gas could be collected reliably, the difference couldn't be detected.

Measuring the effect requires process that release vastly more energy than ordinary chemical processes. The discovery of Radium and Polonium around 1898 gave a tantalizing hint that there were processes that released far more energy than chemical processes could account for. These elements continuously released measurable heat, and also glowed in the dark.

Einstein touched on this possibility in his original 1905 paper.<ref name=einstein1905b/>
{{cquote|''It is not impossible that with bodies whose energy content is variable to a high degree (e.g. with radium salts) the theory may be successfully put to the test.''}}It would take more than a decade to develop an understanding of the nuclear process involved. The first thing that was required was accurate knowledge of atomic weights.

Atomic weights of the various elements were first measured, with accuracy of a few decimal places, by J. J. Berzelius in the late 1820s. This required extremely painstaking (for the time) measurements. The figures were refined to even more accuracy by J. A. R. Newlands in the 1860s. The values were accurate enough to clearly show the rather interesting property that the atomic weights were nearly integers, but not exactly so. The reason for this would turn out to be partly because of different isotopes (discovered by Frederick Soddy in 1913) and partly because of E=mc2.

In 1907 Rutherford determined that the "alpha" radiation from Radium was Helium. In 1911 he formulated the theory of the nucleus. In 1919 he demonstrated that nuclear transmutations could take place, such as

::<math>{}_7^{14}\mathrm{N}\, +\, {}_2^4\mathrm{He}\,\rightarrow\, {}_8^{17}\mathrm{O}\, +\, {}_1^1\mathrm{H}</math>

The discovery of Radon, and much further investigation, revealed that the behavior of Radium was

::<math>{}_{88}^{226}\mathrm{Ra}\,\rightarrow\, {}_{86}^{222}\mathrm{Rn}\, +\, {}_2^4\mathrm{He}</math>
and
::<math>{}_{86}^{222}\mathrm{Rn}\,\rightarrow\, {}_{84}^{218}\mathrm{Po}\, +\, {}_2^4\mathrm{He}</math>

Accurate ways of measuring speed of a charged particle, by deflecting it in a magnetic field, had been developed by then, so that, by very painstaking observation and measurement, it was determined that the first alpha particle (Helium nucleus) had an energy of 4.78 MeV and the second an energy of 5.49 Mev. This confirmed E=mc2 up to the accuracy of the measurements. The equation, along with knowledge of isotope mixes, now explained why the atomic weights appearing in the periodic table were nearly integers, but not exactly so.

Around 1925, the development of the mass spectrograph, by Francis Aston, made it possible to measure atomic weights to extreme precision.

The 1932 Cockcroft-Walton experiment, described in more detail below, started to make the equation famous by confirming it, with reasonable accuracy, for an artificially induced nuclear reaction. (Confirming E=mc2 was not a goal of the experiment; it was an incidental consequence. The equation had already been known and understood for many years.)

In the decades since, nuclear transmutations have been performed, in particle accelerators, all over the periodic table, observing in detail the properties of various isotopes. These have confirmed E=mc2 with great precision. Perhaps the most precise test, by Rainville ''et. al.'',<ref name="rainville">[http://www.nature.com/nature/journal/v438/n7071/full/4381096a.html Nature 438, 1096-1097 (22 December 2005)] doi:10.1038/4381096a; Published online 21 December 2005</ref> confirmed the equation to an accuracy of a few parts per million.

==Alleged Experimental verification--the Cockcroft-Walton experiment==
In 1932 English physicist John Cockcroft and Irish physicist Ernest Walton performed the first artificial nuclear transmutation of nuclei, for which they were awarded the 1951 [[Nobel Prize]] in physics -- '''''but not for any verification of E=mc²'''''.<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/cockcroft-lecture.pdf John D. Cockroft ''Experiments on the interaction of high-speed nucleons with atomic nuclei''], Nobel Lecture, Dec 11, 1951</ref> The award was for ''"their pioneer work on the transmutation of atomic nuclei by artificially accelerated atomic particles."''<ref>[http://www.nobelprize.org/nobel_prizes/physics/laureates/1951/# Nobel Prize Organization]</ref>

Verifying E=mc² was not the goal of the experiment, and the Nobel prize was awarded for the transmutation itself, not any verification of the equation. But analysis of the experiment does in fact verify the equation for the transmutation involved.

They bombarded [[Lithium]] atoms with [[protons]] having a [[kinetic energy]] less than 1 [[Electron-Volts|MeV]]. The result were two (slightly less heavy) [[alpha particle]]s, for which the [[kinetic energy]] was measured as 17.3 MeV

:::::<math>{}_3^7\mathrm{Li}\, +\, {}_1^1\mathrm{H}\,\rightarrow\,2\, {}_2^4\mathrm{He}</math>

The mass of the particles on the left hand side is 8.0263 [[atomic mass units|amu]], the mass on the right hand side ''only'' 8.0077 amu.<ref>Gerard Piel ''The age of science: what scientists learned in the 20th century'', Basic Books, 2001, p. 144-145</ref> The difference between this masses is .00186 amu, which results in the following back-of-an-envelope calculation:

::::<math>0.00186\,\mathrm{amu} \cdot c^2 = 0.0186 \cdot 1.66 \cdot 10^{-27}\,\mathrm{kg}\cdot\left(3\cdot10^8\,\mathrm{\frac{m}{s}}\right)^2</math>
::::<math>\approx\,2.79\cdot 10^{-12} \,\mathrm{kg}\mathrm{\frac{m^2}{s^2}}</math>
::::<math>\approx \,17.3\,\mathrm{MeV}</math>

Accurate measurements and detailed calculations allowed for verifying the theoretical values with an accuracy of ±0.5%. This was the first time a nucleus was artificially split, and thereby the first transmutation of elements using accelerated particles:

Perhaps best empirical verification of '''E=mc2''' was done in 2005 by Simon Rainville et al., as published in ''[[Nature (journal)|Nature]]'' (which is not a leading physics journal).<ref name="rainville"/> The article states that "Einstein's relationship is separately confirmed in two tests, which yield a combined result of 1−Δmc²/E=(−1.4±4.4)×10−7, indicating that it holds to a level of at least 0.00004%. To our knowledge, this is the most precise direct test of the famous equation yet described."

==A Famous Example -- Nuclear Fission of Uranium==

For most types of physical interactions, the masses of the initial reactants and of the final products match so closely that it is essentially impossible to measure any difference. But for nuclear reactions, the difference is measurable. That difference is related to the energy absorbed or released, described by the equation E=mc². (The equation applies to '''all''' interactions; the fact that nuclear interactions are the only ones for which the mass difference is measurable has led people to believe, wrongly, that E=mc² applies only to nuclear interactions.)

The [[Theory of Relativity]] played no role in this work, but proponents later tried to retrofit the theory to the data in order to explain the explain the observed mass changes.<ref>Actually, the formula E=mc2 was published in 1905, and has not changed since then. Fission of Uranium was discovered in 1938. It is not possible that the equation was retrofitted to explain this discovery.</ref> Here is the most famous example of the mass change.

Nuclear fission, which is the basis for nuclear energy, was discovered in experiments by [[Otto Hahn]] and [[Fritz Strassman]], and analyzed by [[Lise Meitner]], in 1938.

There are a great number of decay paths of [[Uranium]] fission that figured in this experiment. The result element that most caught their attention was [[Barium]], because it was chemically related to the Radium that they were expecting. One of the fission paths may have been this:

:235U → 140Xe + 91Sr + 4n

(The [[Xenon]] decayed within about a minute to 140Ba. They were searching for the chemical signature of Barium.)

The masses of the particles are:

{| class="wikitable" border="1" cellpadding="8" cellspacing="0"
! Substance
! 235U
! 140Xe
! 91Sr
! 4 neutrons
|-
| Number of protons
| 92
| 54
| 38
| 0
|-
| Number of neutrons
| 235
| 140
| 91
| 4
|-
| Number of electrons
| 92
| 54
| 38
| 0
|-
| Mass
| 235.04393
| 139.92164
| 90.910203
| 4.03466
|}

The mass of the Uranium atom is 235.04393, and the sum of the masses of the products is 234.866503. The difference is .177427 amu, or, using the E=mc² equation, 165 million electron volts. (The generally accepted value for the total energy released by Uranium fission, including secondary decays, is about 200 million electron volts.)

The insight that the conversion from Uranium to Barium was caused by complete fission of the atom was made by Lise Meitner in December, 1938. She had the approximate "mass defect" quantities memorized, and so she worked out in her head, using the E=mc² equation, that there would be this enormous release of energy. This release was observed shortly thereafter, and the result is nuclear power and nuclear weapons.

==A Topical Example: Speed of Extremely Energetic Neutrinos==
Here is another example of the use of this formula in physics calculations. In 2011 there were [http://www.theguardian.com/science/2011/sep/22/faster-than-light-particles-neutrinos?newsfeed=true reports] that high-energy neutrinos had been observed traveling at a speed faster than the speed of light in an experiment at the Gran Sasso laboratory in Italy. Specifically, they seemed to have arrived at the detector 60 nanoseconds faster than light would have. Relativity doesn't allow that, and, since neutrinos have nonzero (but incredibly tiny) mass, they aren't even supposed to travel ''at'' the speed of light.

The mass of a neutrino is about 0.44x10−36kilograms. (Normally all of these things are measured in more convenient units such as Giga-electron-Volts, but that makes implicit use of E=mc2. If we don't accept that, we have to do the calculations under classical physics, using SI (meter/kilogram/second) units.) The neutrinos were accelerated to an energy of about 17GeV, or .27x10−8Joules. If one did not accept relativity and had to use classical physics and the classical formula <math>\mathrm{E} = \frac{1}{2}mv^2</math>, one would get v=110x1012 meters per second. This is about 370,000 times the speed of light, something that scientists would certainly have noticed. In fact, with special relativity, the speed is just under the speed of light, such that the neutrinos should be received at the detector about .26x10−24 seconds (.26 yoctoseconds) later than the speed of light itself. This is far too small to measure—15 orders of magnitude smaller than the resolution of the GPS signals in the experiment.

Later [http://news.sciencemag.org/2012/02/official-word-superluminal-neutrinos-leaves-warp-drive-fans-shred-hope%E2%80%94barely?ref=hp reports] started to resolve the mystery, and it is now accepted that the neutrinos behaved properly. But a BBC reporter made the incorrect statement that [http://www.bbc.co.uk/news/science-environment-17364682 the neutrinos travelled at precisely light speed]. This was a simple misstatement, by .26 yoctoseconds.

The issue was discussed at length at Conservapedia.<ref>http://www.conservapedia.com/Talk:Main_Page/Archive_index/102#Faster_than_light_neutrinos</ref><ref>http://www.conservapedia.com/Talk:Main_Page/Archive_index/102#The_final_nail_in_the_coffin_of_relativity.3F</ref><ref>http://www.conservapedia.com/Talk:Main_Page/Archive_index/102#Another_Blow_to_Relativity</ref><ref>http://www.conservapedia.com/Talk:Main_Page/Archive_index/109#Neutrinos_now_obey_speed_limit</ref><ref>http://www.conservapedia.com/Talk:Main_Page/Archive_index/111#Neutrinos</ref>

==Deducing the Equation From Empirical Observation==

While the equation was historically developed on theoretical grounds as an inevitable consequence of special relativity, it is possible to deduce it purely from empirical observation.

So, for the purposes of this section, imagine that one is in the era of "classical physics"; prior to 1900 or so. Relativity has not been invented, but, inexplicably, nuclear physics has. Imagine that the phenomena of radioactivity and nuclear fission have been observed, without any knowledge of relativity.

A well-accepted physical law of classical physics was the law of conservation of mass. This was not easy to deduce. It required careful analysis of such phenomena as combustion, in the 1700s, to eliminate the various confounding sub-phenomena that made the law difficult to see. But, by 1900, the law was well established:

:::*'''In all interactions, mass is precisely conserved.'''

For example, the mass of a TNT molecule is 227.1311 Daltons, or 227.1311 g/mol, which is, for all practical purposes, the same as the mass of its constituent Carbon, Hydrogen, Nitrogen, and Oxygen atoms. It is essentially impossible to measure the difference. The principle of conservation of mass is upheld.

But when nuclear phenomena are discovered, we notice something different. The masses of the result particles after an event (e.g. alpha decay, nuclear fission, or artificial transmutation) is measurably less than the masses of the original particle(s). With the invention of the mass spectrometer around 1920, it became possible to measure atomic weights of various isotopes with great precision.

Radium-226 decays into Radon-222 by emission of an alpha particle with an energy of 4.78 MeV.

1 kg of Radium-226 = <math>\frac{6.022 \times 10^{23}}{226.0254}</math> atoms. (The numerator is [[Avogadro's number]], and the denominator is the atomic weight of Radium-226.) This is 2.6643647 * 1024 atoms.

That number of Radon-222 atoms has mass .98226836 kg. That number of alpha particles has mass .01770863 kg.
The mass lost is .00002301 kg.

Each emitted alpha particle has energy of 4.78 MeV, or 4.78 * .1602 * 10−18 Joules. The total alpha energy from the decay of 1 kg of radium is 2.04 * 1012 Joules.

Also, Radon-222 decays into Polonium-218 by emission of an alpha particle with an energy of 5.49 MeV.

1 kg of Radon-222 = <math>\frac{6.022 \times 10^{23}}{222.0176}</math> atoms. This is 2.7124611 * 1024 atoms.

That number of Polonium-218 atoms has mass .98194467 kg. That number of alpha particles has mass .01802830 kg.

The mass lost is .00002703 kg.

Each emitted alpha particle has energy of 5.49 MeV. The total alpha energy from the decay of 1 kg of polonium is 2.39 * 1012 Joules.

It looks as thought we have to rewrite the law of conservation of mass:

:::*'''In all "ordinary" interactions, mass is precisely conserved.'''
:::*'''In nuclear interactions, there is a small but measurable loss of mass.'''

:By the way, we can clearly see that atomic weights of pure isotopes are not integers, and that it has something to do with the energy released by nuclear disintegration. In retrospect, the formula E=mc² explains the non-integer character of atomic weights.

Making special cases like this is unsatisfactory, of course.

We do this for a few other interactions, including the explosion of TNT. This would include the Lithium-plus-Hydrogen and Uranium fission phenomena described above. We won't bother with the details. As observational scientists, we look for patterns in the behavior of nature. We make a table:

{| class="wikitable" border="1" cellpadding="8" cellspacing="0"
! interaction
! energy released per kg, Joules
! mass lost per kg of original substance, kg
|-
| explosion of TNT
| 4.184 * 106
| seems to be zero
|-
| alpha decay of Ra-226
| 2.04 * 1012
| .00002301 kg
|-
| alpha decay of Rn-222
| 2.39 * 1012
| .00002703 kg
|}

We plot these, and a few others, not shown, on graph paper, and find to our amazement that the relationship is linear.

For Ra, m/E = .112794118 E-16
For Po, m/E = .113096234 E-16

If this is linear, the mass defect for TNT would have been .47 * 10−10. We couldn't possibly have measured this.

So we can rewrite the rule for conservation of mass in a more satisfactory way:

:::*'''In all interactions, there is a loss of mass, equal to about .113 * 10-16 kg per Joule of energy released.'''

What we thought was exact conservation is just very nearly exact, and we hadn't been able to measure it before.

But maybe there's more. This constant has dimensions of kilograms per Joule. From high-school physics, we know that that is seconds squared divided by meters squared. That is, it is the reciprocal of the square of a velocity. We calculate that velocity. It is about 2.97 * 108 meters per second. Very close to the speed of light! Very interesting! (The calculations above were not extremely precise. The formula has been verified with great precision, but not here.)

We don't understand why (that will have to wait for the invention of relativity), but we can formulate a hypothesis:

:::*'''In all interactions, there is a loss of mass, equal to <math>\frac{1}{c^2}</math> times the amount of energy released.'''

We don't have to give the units any more, since everything is now dimensionally correct.

::There is a very interesting analogy with the discovery of [[Maxwell's Equations]]. Maxwell found an interesting relationship involving the fundamental constants <math>\epsilon\,</math> and <math>\mu\,</math> appearing in his equations. Specifically, <math>\epsilon\mu\,</math> has the dimensions of seconds squared divided by meters squared, and that:

:::::<math>\frac{1}{\epsilon\mu} = c^2</math>

::where "c" was the known velocity of light. He also showed that his equations predict electromagnetic waves, propagating at that speed.

==See also==
*[[Attempts to prove E=mc²]]
*[[Counterexamples to Relativity]]
*[[Essay:Rebuttal to Counterexamples to Relativity]]
*[[Logical Flaws in E=mc²]]
*[[Essay:Rebuttal to Logical Flaws in E=mc²]]
*[[E^2=(mc^2)^2+(pc)^2]]

== References ==
<references />
[[Category:Relativity]]
[[Category:Physics]]
[[Category:Science]]
[[Category:Bible]]

E^2=(mc^2)^2+(pc)^2

2016-09-10T18:01:09Z

Harryk: Added some relations to other formulae

'''<math> E^2=(m_0 c^2)^2+(pc)^2 </math>''' is a formula in [[relativity|special relativity]] that relates the relativistic energy, E, [[rest mass]], <math>m_0</math>, and [[momentum]], p, of a particle. From it the momentum of a [[photon]] can be derived and so to the famous equation [[e=mc^2|E=mc2]].

== Derivation ==

The relativistic equation for [[momentum]] is:

<math>p = \gamma m_0 v</math>

The equation for relativistic energy is:

<math>E = \gamma m_0 c^2</math>

These can be rearranged into the forms:
<math>( \frac{E}{m_0 c^2} )^2 = \gamma ^2 </math>
 
<math>(\frac{p}{m_0 c} )^2 = (\frac{\gamma v}{c} )^2 </math>

Subtracting the momentum equation from the energy equation an rearranging gives:
<math> E^2=(m_0 c^2)^2+(pc)^2 </math>

== Other Formulae ==

The energy of a photon can be derived by setting the [[rest mass]], <math>m_0</math>, equal to zero, so:
<math>E=pc</math>

Mass energy equivalence can be derived by setting the momentum, <math>p</math>, to zero. This gives us one of the most famous equations in physics, <math>E=m_0 c^2</math>

[[Category:Physics]]
[[Category:Relativity]]

Rest mass

2016-09-10T17:49:09Z

Harryk: Couple of corrections

The '''rest mass''' of a particle is a term used in [[relativity]] to denote the mass that a particle has at rest. More specifically, it is the mass an observer would measure a particle to have if the observer is in the same [[inertial frame of reference]] as the particle in question. The term is used to draw a distinction with the other term "relativistic mass". Rest mass is also sometimes called "invariant mass".

The rest mass of a particle (the terms are almost always used in the context of [[atom]]s or [[subatomic particle]]s) is what it would weigh if you put it on a scale. It includes any contribution from the particle's potential energy. So, for example, the mass of a Radium-226 atom is 226.0254098 amu. This includes the .0052288 amu for the potential energy that would be released if the atom undergoes an alpha decay, as well as the 226.020181 amu that are latent in the results of the alpha decay. If you could put a radium atom on a scale, it would register 226.0254098 amu.

It happens that, under relativity, the momentum of a particle in motion is given by
:<math>p = \frac{1}{\sqrt{1-v^2/c^2}}\ m\ v</math>
instead of the "classical" formula
:<math>p = m v\,</math>
where '''v''' is the particle's speed. This definition is required in order to get precise conservation of momentum in all frames of reference.

As can be seen, the difference is only significant for particles travelling at speeds comparable to the speed of light, that is, "relativistic" speeds.

Some people have gotten around this issue by using a subscript zero to denote the particle's rest mass, and defining something called the "relativistic mass", denoted '''m''', as
:<math>m = \frac{m_0}{\sqrt{1-v^2/c^2}}\,</math>
so that the momentum formula will look more natural in terms of this "relativistic mass" '''m'''.
:<math>p = m v\,</math>

This usage is obsolete and should be avoided. It's best to think of momentum as something that grows faster than just <math>p=mv\,</math> would suggest.

The factor
:<math>\frac{1}{\sqrt{1-v^2/c^2}}</math>
shows up in a number of places in relativity, and is called the ''[[Lorentz factor]]'', commonly denoted with the Greek letter <math>\gamma\,</math>. This means that the formula for momentum is
:<math>p = \gamma m v\,</math>

==See also==

*[[E=mc²]]
*[[E^2=(mc^2)^2+(pc)^2]]

[[Category:Physics]]
[[Category:Relativity]]

United Kingdom

2016-09-10T16:11:48Z

Harryk: Few changes, formatting etc.

{{Country
|name =''The United Kingdom of Great Britain and Northern Ireland''
|map =United kingdom rel87.jpg
|map2 =UK location.png
|flag =Union_jack.jpg
|arms =UK Royal Coat of Arms.png
|capital =London
|capital-raw =
|government =Constitutional monarchy
|government-raw =
|language =English
|king =
|queen =
|monarch-raw =HM Queen [[Elizabeth II]]
|president =
|president-raw =
|chancellor =
|chancellor-raw =
|pm =David Cameron
|pm-raw =
|area =94,526 sq mi
|pop =62,698,000
|pop-basis =2011
|gdp =$2.006 trillion
|gdp-year =2006
|gdp-pc =$35,051 (2006)
|currency =Pound Sterling
|idd =
|tld =
}}
'''The United Kingdom of Great Britain and Northern Ireland''' ('''UK''') is a sovereign [[state]] north-west of mainland [[Europe]]. It comprises [[England]], [[Scotland]] and [[Wales]], which occupy the island of [[Great Britain]], and [[Northern Ireland]] on the island of [[Ireland]]. It attained its current identity in 1922 after most of Ireland was granted independence.

The United Kingdom is a constitutional monarchy. Its [[head of state]] is Queen [[Elizabeth II]], and its [[head of government]] is Prime Minister [[Theresa May]].

The United Kingdom has lost the preeminence in the world that it enjoyed 100 years ago, due to its decline into [[socialism]], [[Darwinism]] and godlessnes/[[atheism]].<ref>
*[http://www.people.fas.harvard.edu/~nfergus/publications/Economics%20Religion%20and%20the%20End%20of%20Europe%20as%20published%20in%20Ec%20Aff.pdf ECONOMICS, RELIGION AND THE DECLINE OF EUROPE] by the [[Harvard University]] historian Niall Ferguson
*[http://creation.com/why-is-england-burning Why is England Burning?]
*[http://www.jpost.com/Opinion/Columnists/Godlessness-has-doomed-Britain Godlessness has doomed Britain], [[Shmuley Boteach]],'' Jerusalem Post''
*[http://creation.com/christianity-as-progress A review of The Victory of Reason: How Christianity Led to Freedom, Capitalism, and Western Success by Rodney Stark, Random House, New York, 2005], reviewed by Lael Weinberger
*[http://www.heraldscotland.com/comment/columnists/scotland-still-has-a-job-on-its-hands-to-reverse-decline.21330686 Scotland still has a job on its hands to reverse decline], The Herald, Thursday 13 June 2013
*[http://www.heraldscotland.com/news/home-news/census-reveals-huge-rise-in-number-of-non-religious-scots.22270874 Census reveals huge rise in number of non-religious Scots].'' The Herald'', Friday 27 September 2013
*[http://www.telegraph.co.uk/news/uknews/scotland/9594221/Scotlands-vitality-was-the-envy-of-the-world.html Scotland’s vitality was the envy of the world], ''The Telegraph'', By Allan Massie, 8:06PM BST 08 Oct 2012
*[http://blog.tifwe.org/the-protestant-work-ethic-alive-well-in-china/ The Protestant Work Ethic: Alive & Well…In China] By Hugh Whelchel on September 24, 2012
*The prominent investor Jim Rogers declared: "If you were smart at the start of the 19th century, you made your way to [[London]]. If you were smart at the start of the 20th century, you moved to New York. And if you are smart at the start of the 21st century, you will find your way to Asia."[http://www.asiancenturyinstitute.com/international/198-jim-rogers-on-asia-singapore-and-life]
</ref> It has fallen from having by far the world's strongest economy to a distant fifth place.

The United Kingdom is a member of the [[European Union]], [[NATO]] and the [[United Nations]].

British values, culture and institutions were spread throughout many parts of the world during the period of the [[British Empire]], 1600-1960, and British contributions to world culture include the English language, the [[parliament]]ary form of government, the [[Church of England|Anglican]] Church ("Church of England"), a tradition of personal liberty, and the [[common law]] legal system. Note, however, that the United Kingdom does not have the constitutional [[free speech]] protections or an energetic [[Christian]] culture that exist in the [[United States]] as it does not have a written constitution. However various acts mean there is free speech, similar to that in the [[United States]].

In 2015, the UK was ranked 12th on the World Democracy index, above countries such as the US and France, and below those like Germany and Canada.<ref>[http://democracyranking.org/wordpress/rank/democracy-ranking-2015/ World's Democracy Index]</ref>

==Name==
[[File:London Thames Sunset panorama 2008.jpg|thumb|left|London - Thames panorama.]]
The official name of the nation (since 1927) is ''The United Kingdom of Great Britain and Northern Ireland''.<ref>From 1801 to 1927 the official name was ''The United Kingdom of Great Britain and Ireland''.</ref> The full official name is seldom used except in very formal or legal documents. The short version for historical topics is either "Britain" or "Great Britain." The short version for recent events (since the 1970s) is "United Kingdom" or "UK" The adjective is always '''"British"'''.

Britain was part of the [[British Empire]], which has become the "British Commonwealth", and is mostly a discussion club. Britain has a few scattered minor possessions, such as [[Gibraltar]], but gave up its last important colony--[[Hong Kong]]—in 1997.
[[File:Westminster in the evening.jpg|thumb|280px|Westminster in the evening.]]
* '''England''' is the largest of the four components of the United Kingdom. "England" was often used to stand for the nation in older literature published before 1970. However use of "England" to refer to the entire country is now sometimes considered offensive by many citizens of the other three member countries and is thus discouraged.
* The standard language of the UK is English; [[Welsh]] has parity in Wales, and [[Gaelic]] is widely used on official documents, roadsigns, etc. in remote Gaelic-speaking areas of western Scotland.

MacColl (2008) explores the use of the term 'Britain' in English, French, and Latin texts from the 12th century to the 16th. The term was flexible, used in a variety of ways (geographically, politically, and ethnically), and not always indicative of any specific meaning. The English at first tended to conflate 'Britain' with England or the southern portion of the island of Great Britain, though the term 'Greater Britain' was applied starting in the 14th century to refer to the entire island. The Scottish, beginning in the 15th century, used the term in the modern sense - as reflective of the entire island of Great Britain and the 'polity' of England, Wales, and Scotland. This latter usage paved the way for the relatively smooth ideological transition after the 1707 Acts of Union.<ref>Alan MacColl, "The Meaning of 'Britain' in Medieval and Early Modern England." ''Journal of British Studies'' 2006 45(2): 248-269</ref>

===Anthem===

The national anthem of the UK is currently ''[[God Save the Queen]]''. Should a male heir accede to the throne, the anthem will become "God Save the King".<ref>This same melody is also sung by American schoolchildren (with different words) as "[[My Country, 'Tis of Thee]]".</ref>

The constituent nations have their own unofficial anthems. In the case of Wales, this is ''Hen Wlad Fy Nhadau'' (''Land of My Fathers''), and for Scotland it is ''Flower of Scotland''. England does not have its own distinctive anthem in the same way, but at sporting events in which England is competing as a separate nation, [[Edward Elgar]]'s patriotic song ''Land of Hope and Glory'' is sometimes used (although ''God Save the Queen'' is more commonly used). Additionally the hymn "Jerusalem" has a large number of supporters in England as an alternative to, or replacement for, the national anthem. In Northern Ireland, the Protestant and Catholic communities respectively use ''God Save the Queen'' and ''Amhran na bhFiann'', the Irish national anthem. ''Londonderry Air'' is often used as the anthem for Northern Ireland competitors in sporting events.

==People==
[[Image:Tower Bridge London.jpg|thumb|340px|Tower Bridge, London.]]
The United Kingdom's population in 2004 surpassed 60 million—the third-largest in the European Union. Its overall population density is one of the highest in the world. Almost one-third of the population lives in England's prosperous and fertile southeast and is predominantly urban and suburban—with about 7.2 million in the capital of London, which remains the largest city in Europe.

A net total of 408,000 people were added to the UK population in 2008, the largest numerical increase since 1972. This was partly due to the highest fertility rate in more than three decades. More than half of the increase in births last year was due to non-UK born mothers.

There is also an ever-increasing aging population with the number of people over 85 now at a record 1.3 million, the equivalent of one in every 50 people.

===Education===
[[File:Royal College of Music 2007.jpg|thumb|left|Royal College of Music.]]
The United Kingdom's high literacy rate (99%) is attributable to universal public education introduced for the primary level in 1870 and secondary level in 1900. Education is mandatory from ages 5 through 16, although this is in the process of being raised to 18 for England and Wales. "Public" schools are elite private prep schools, such as [[Eton]] and [[Rugby School|Rugby]], attended by youth whose families can afford to pay high tuition rates.

All state-funded schools in the UK are required to start the day with a collective assembly that is 'wholly or mainly of a broadly Christian character',<ref>[http://www.tes.co.uk/article.aspx?storycode=387464 Times Educational Supplement]</ref> although this is not always ahered too and there are small numbers of state-funded [[Muslim]], [[Jew]]ish and [[Hindu]] schools.

About thirty six percent of British students go on to post-secondary education.

Higher education has been a speciality for over 500 years at Oxbridge ([[Oxford University|Oxford]] and [[Cambridge University|Cambridge]]), with new "red brick" universities added in the 19th century and many others in the late 20th century. Universities contribute £33 billion a year to the economy. Britain has a strong attraction for international students, with 342,000 attending in 2007 (compared to 672,000 in the U.S. and 183,000 in Australia). They spend £1.5 billion in tuition in Britain annually, plus another £0.4 billion off campus.

===Demographics===
[[File:Youth UK.JPG|thumb|British youth.]]
A group of islands close to continental Europe, the British Isles have been subject to many invasions and migrations, especially from Scandinavia and the continent, including Roman occupation for several centuries. Contemporary Britons are descended mainly from the varied ethnic stocks that settled there before the 11th century. The pre-Celtic, Celtic, Roman, Anglo-Saxon, and Norse influences were blended in Britain under the Normans, Scandinavian Vikings who had lived in Northern France. Although Celtic languages persist in Wales, Scotland, and Northern Ireland, as well as Cornwall in south-west England, the predominant language is English, which is primarily a blend of Anglo-Saxon and Norman French.
*Population (2007 est.): 60.8 million.
*Annual population growth rate (2007 est.): 0.275%.
*Major ethnic groups: British 91%, Irish 2%, West Indian and African 3%, South Asian 3%, others 1%.
*Major religions: Church of England (Anglican), Roman Catholic, Church of Scotland (Presbyterian), Muslim.
*Major languages: English
*Minority languages: Welsh, Gaelic, Lowland Scots (including Ulster Scots), Cornish.
*Education: Years compulsory—12. Attendance—nearly 100%. Literacy—99%.
*Health: Infant mortality rate (2007 est.)--5.01/1,000. Life expectancy (2007 est.)--males 76.23 yrs.; females 81.3 yrs.; total 78.7 years
*Work force (2007, 31.1 million): Services—80.4%; industry—18.2%; agriculture—1.4%.

===Ethnic tensions===

Britain is home to 2.4 million Muslims from numerous ethnicities. This population is growing 10 times faster than the national average. Regarded as one of the most tolerant countries in Europe, Britain struggles with questions of Islamic integration, as well as the psychological aftermath of the July 2005 suicide bombings on London’s public transport system carried out by young Britons of Pakistani descent, which left 52 people dead and over 700 injured.

===Religion===

[[File:Canterbury Cathedral.jpg|thumb|left|350px|Canterbury Cathedral (photographed during 1890-1900).]]
Religious faith, according to a 2011 survey, has declined sharply in Britain over the last two decades. Now only 42% of people describe themselves as Christian, as opposed to 66% in 1990. Most of the decline is due to a drift away from the Church of England, it is claimed, with only 20% claiming allegiance, down from 40%.

In 2003 the Office of National Statistics estimated 29% of the population identified with Anglicanism, 10% with the Catholic Church, and 14% with other Protestant churches. A 2007 survey reported that the number of Catholics (mostly Irish) attending Sunday services has overtaken the number of Anglicans doing so. A September 2006 English Church Census reported that Methodists were decreasing as a percentage of the population, while members of the Church of Jesus Christ Latter-day Saints (Mormons), Pentecostal churches, many churches from Africa, and the Eastern Orthodox Church, almost entirely immigrants, were increasing.<ref>According to [http://www.state.gov/g/drl/rls/irf/2008/108478.htm U.S. State Department Report, 2008]</ref>

Individuals with no religious belief comprised 21% of the population in 2009. Muslims comprise 3% of the population. The Muslim community is predominantly South Asian in origin, but other groups from the Arabian Peninsula, Africa, Southeast Asia, and the Levant are represented. In addition, there is a growing number of indigenous converts. Although estimates vary, the Government places the number of mosques in the whole country at one thousand. Groups comprising 1% or less of the population include Hindus, Sikhs, Jews, and Buddhists. Individuals from Jewish, Hindu, Buddhist, Muslim, and Sikh backgrounds are concentrated in London and other large urban areas, primarily in England.

Attendance at religious services was significantly different from the number of adherents. According to a report released on May 8, 2008, by Religious Trends, only 4 million Christians attend services on a regular basis (defined as at least once a month) in the country. These figures do not include Northern Ireland, where higher%ages reportedly attend both Catholic (more than 60%) and Protestant (more than 35%) services. The Religious Trends report stated that more than 50% of Muslims regularly worship at mosques. Figures for Jews and other religious groups were unavailable.

Religious affiliation was not evenly distributed among ethnicities. According to the 2001 census, approximately 70% of the white population described themselves as Christians. Nearly 75% of black Caribbean respondents stated that they were Christians, as did 70% of black Africans. Meanwhile, 45% of Indians were Hindus and 29% were Sikhs. Approximately 92% of Pakistanis and Bangladeshis were Muslims.

In Northern Ireland, where divisions between nationalists and unionists evolved largely along religious lines, the 2001 census showed that 53.1% were Protestants and 43.8% were Catholics. Many Catholics and Protestants continued to live in segregated communities in Northern Ireland, although many middle-class neighborhoods were mixed communities. The policy of the Government remained one of promotion of religious tolerance.

There are two established (or state) churches—The [[Church of England]] (Anglican) and the [[Church of Scotland]] (Presbyterian). The Act of Settlement, enacted in 1688, states that no Catholic, or person married to a Catholic, may ascend the throne.

====Religion in schools====

The Government provides financial support—up to 90% of the total capital costs of the buildings and 100% of running costs, including teachers' salaries - to sectarian educational institutions that are commonly referred to as "faith schools".
[[File:Matthew Boulton College.jpg|thumb|Matthew Boulton College.]]
The Government also helps fund the repair and maintenance of all listed places of worship for religious groups nationwide and contributes to the budget of the Church Conservation Trust, which preserves "redundant" Church of England buildings of architectural or historic significance.

The Government has not classified the Church of Scientology as a religious institution and therefore has not granted the organization recognition for charitable status.

More than 30% of state schools had a religious character. Nearly all of the 6,949 "faith schools" are associated with Christian denominations, although there are 31 Jewish, 7 Islamic, and 2 Sikh schools. An additional two Jewish, three Islamic, and two Sikh schools have also been tentatively approved by the Government to open. In addition, several hundred independent schools of a religious nature receive no state support but must meet government quality standards. Controversy arose in 2006 over 100 Islamic schools when an Office of Standards in Education (Ofsted) evaluation of these schools showed many were "little more than places where the Koran was recited." The schools were given time to correct their deficiencies. A review is due in 2010. Some Christian faith schools also faced controversy. Some were accused of not following the national curriculum in science, teaching creationism instead. During the reporting period, a further controversy erupted when it was learned that some faith schools were not following an "open" admission policy as required by law, denying admission to both special needs children and those outside the faith of the school administrators. The Catholic Church and the Church of England have an agreement to voluntarily accept up to 25% of places for pupils from another religious group or no religious group.

Almost all schools in Northern Ireland receive state support. More than 90% of students attended schools that were either predominantly Catholic or Protestant. Integrated schools served approximately 5% of school-age children whose families voluntarily chose this option, often after overcoming significant obstacles to provide the resources to start a new school and demonstrate its sustainability for 3 years before government funding begins. Demand for places in integrated schools outweighed the limited number of places available. The May 8, 2007, devolution, or granting of power, authorized the Northern Ireland Assembly to decide on academic selection. Now there are more than 50 integrated schools, and the new Government permits existing schools to petition to change from sectarian to integrated. More petition for that status than are granted it. Some have accused the Government of a go-slow approach to avoid sectarian animus.

The law requires religious education for all children, ages 3 to 19, in publicly maintained schools. In England and Wales it forms part of the core curriculum in accordance with the Education Reform Act of 1988. In Scotland, religious education of some sort is mandated by the Education Act of 1980. However, the shape and content of religious instruction throughout the country is decided on a local basis. Locally agreed syllabi are required to reflect the predominant place of Christianity while taking into account the teachings and practices of other principal religions in the country. Syllabuses must be nondenominational and refrain from attempting to convert pupils. Schools with a religious designation follow a syllabus drawn up by the school governors according to the trust deed of the school. All parents have the legal right to request that their children not participate in religious education, but the school must approve this request.

Daily collective prayer or worship of "a wholly or mainly of a broadly Christian character" is practiced in schools in England and Wales, a requirement that may be waived for students who obtain permission of the school authorities. The Education and Inspections Act 2006 permits sixth form students (generally 16-19-year-olds) to withdraw themselves from worship without their parents' permission or action. This new law does not exempt sixth form students from religious education classes. Non-Christian worship is permitted with approval of the authorities. Teachers have the right not to participate in collective worship, without prejudice, unless they work for a faith school.

After several controversial court decisions prohibiting full-face veils in school (but not head scarves) and the wearing of a Christian chastity ring, the Department of Education provided guidance that advises schools to "… act reasonably in accommodating religious requirements," under human rights legislation. Some Muslim groups, including the Islamic Human Rights Commission, said it was inappropriate for the Government to provide guidance that regulated Muslim communities in matters concerning the expression of their religious beliefs. But it is also legally possible under the act, according to the guidance, to have a school uniform policy that "restricts the freedom of pupils to manifest their religion" on the grounds of health and safety and the "protection of the rights and freedoms of others." The Government's guidance is meant to remind "head teachers" to act with a degree of sensitivity when considering decisions that will impact the cultural complexion of their communities.

====Census====

According to the 2011 Census the religious make-up of the UK at that time was:

{| border="1" cellspacing=0 cellpadding=3
|+'''Religions in United Kingdom'''
!Belief
!Thousands
!Proportion
|-
|Christian ||29,000 ||51.6
|-
|No Religion ||9104 ||15.5
|-
|Muslim ||1591 ||2.7
|-
|Hindu ||559 ||1.0
|-
|Sikh ||336 ||0.6
|-
|Jewish ||267 ||0.5
|-
|Other ||179 ||0.3
|-
|Buddhist ||152 ||0.3
|-
|Pagan & Wicca ||40 ||0.1
|-
|Total religious ||45,163 ||76.8
|-
|No answer ||4289 ||7.3
|}

The answers were distorted by an internet campaign just prior to the census, encouraging people to actually question religion that claimed that if at least 50,000 people stated their religion as 'Jedi Knight' it would be officially classified as a religion. This was not true, though the Office of National Statistics does aggregate very small religions into the 'Other' category whereas a religion of 50,000 would be itemised separately. This separate listing does not constitute any form of official recognition.

It should be noted that non-practising Christians and the non-religious group are growing in the UK and Europe. At the same time, there is growth in the Islamic group due to immigration.

Two of the four states of the United Kingdom, England and Scotland, have official state religions. The [[Church of England]] is the official religion of England and the (Presbyterian) Church of Scotland is the official religion of Scotland. The (Anglican) Church of Ireland was [[disestablished]] in 1871 and the (Anglican) Church of Wales was disestablished in 1920, whereupon it was renamed the [[Church ''in'' Wales]].

===Crown Dependencies===

A number of the smaller [[British Isles]], most importantly [[Jersey]], [[Guernsey]] and the [[Isle of Man]] are '[[Crown dependencies|British Crown Dependencies]]' and not members of the UK. Their governments are independent of that of the UK other than foreign and defense policy (the UK government retains the legal power to overrule the governments of the Dependencies, but this power has not been exercised since 1967), and they are not members of the [[European Union]].

==Sports and Pastimes==

[[File:Wembley Stadium.jpg|thumb|230px|Wembley Stadium.]]
Many of the most popular [[sport]]s in the world today were developed or codified in the UK. These include [[soccer|football]] (which is called ''soccer'' in North America), [[cricket]], [[Rugby (Sport)|rugby]], [[tennis]], [[hockey]], [[baseball]] and [[golf]]. The UK is represented in international competitions by the individual nations (such as in football, the one-day form of cricket and rugby) and by the whole of the UK in other sports (such as [[athletics]], golf and tennis). The Test cricket team is that of 'England & Wales' (colloquially, just 'England') but from time to time has had Scottish and Irish players.

The UK remains a major sporting force both in competition and the administration of sport. It is dominant in several Olympic sports, notably cycling, rowing and sailing and a leading force in cricket, rugby union, and golf.

Certain venues have their own distinct and historical recognition and host a number of international competitions. These include Wimbledon for tennis, Silverstone for motor racing, and St Andrews for golf. There are several major venues for football, rugby and cricket.

Domestic sport is dominated by football with one of the strongest and most popular leagues in the world - the Premier League. This league is sponsored by Barclays Bank, so has the official name "Barclays Premier League". Many of the Premier League's teams are well known outside the United Kingdom, especially the "big four" (Manchester United, Arsenal, Chelsea and Liverpool) and maintain followings around the world. Cricket and both codes of rugby also have strong and popular domestic leagues. Other popular sports include snooker, rowing, golf, tennis, athletics, cycling, darts, horse racing, and motor racing. These most popular sports are well covered by both the print press and television.

Some sports which are more popular in other countries such as volleyball, handball, American football and basketball have small but dedicated followings.

The [[U.K.]] is also renowned for its music, and is the home of bands like [[The Beatles]], [[Rolling Stones]], [[Pink Floyd]], [[The Who]], [[Oasis]], [[Coldplay]] and [[Radiohead]], as well as festivals such as [[Creamfields]], [[Isle of White]] Festival and [[Glastonbury]].

==Government==

''See also [[British politics]]''
[[File:Jewel House guard in the Tower of London.JPG|thumb|200px|Jewel House guard in the Tower of London.]]
Nationalist movements exist in Scotland, Wales and Northern Ireland, seeking (in the case of Scottish and Welsh nationalists) to dissolve the United Kingdom and to win independence for their respective territories, and in the case of Northern Ireland nationalists and republicans to create a sovereign united Ireland. At the present time, Scotland, Wales and Northern Ireland have their own legislatures.

The United Kingdom does not have a written constitution. The equivalent body of law is based on statute, common law, and "traditional rights". Changes may come about formally through new acts of Parliament, informally through the acceptance of new practices and usage, or by judicial precedents. Although Parliament has the theoretical power to make or repeal any law, in actual practice the weight of 700 years of tradition restrains arbitrary actions.

Executive power rests nominally with the monarch but actually is exercised by a committee of ministers (cabinet) selected from among the members of the House of Commons and, less frequently, the House of Lords. The prime minister is normally the leader of the largest party in the House of Commons, and can remain in office for so long as he or she has the support of a majority in that body.

==Parliament==

[[File:Westminster palace Charles Barry.jpg|left|380px]]
Parliament was authorized in the [[Magna Carta]] (1215), and first summoned by King Edward I in 1296, making it one of the oldest governing bodies in the world. Parliament represents the entire country, and can legislate for the whole or for any constituent part or combination of parts. Elections are called by the Prime Minister, but the maximum length of a parliament is usually 5 years (except in wartime). The focus of legislative power is the 646 member [[House of Commons]], which has sole jurisdiction over finance. Normally the government—the Prime Minister and cabinet with their supporting MPs—have full control of the House. If they lose control an new general election may be held. The House of Lords, although shorn of most of its powers, can still review, amend, or delay temporarily any bills except those relating to the budget. In 1999, the government removed the automatic right of hereditary peers to hold seats in the House of Lords. The current house consists of appointed life peers who hold their seats for life and 92 hereditary peers who will hold their seats only until final reforms have been agreed upon and implemented. The judiciary is independent of the legislative and executive branches, but cannot review the constitutionality of legislation.

Members of the House of Commons are elected to represent specific geographic constituencies. Members are elected on a "First past the post" system as opposed to proportional representation or other electoral systems. In effect this means that a third party with less than 25% of the vote typically obtains very few seats.

==Constituent countries==

[[File:Scottish Eilean Donan castle.jpg|thumb|300px|Scottish Eilean Donan castle.]]
The separate identities of each of the United Kingdom's constituent parts are also reflected in their respective governmental structures. Up until the recent devolution of power to Scotland and Wales, a cabinet minister (the Secretary of State for Wales) handled Welsh affairs at the national level with the advice of a broadly representative council for Wales. Scotland maintains, as it did before union with England, different systems of law (Roman-French), education, local government, judiciary, and national church (the Church of Scotland instead of the Church of England). In addition, separate departments grouped under a Secretary of State for Scotland, who also is a cabinet member, handled most domestic matters. In late 1997, however, following approval of referenda by Scottish and Welsh voters (though only narrowly in Wales), the British Government introduced legislation to establish a Scottish Parliament and a Welsh Assembly. The first elections for the two bodies were held May 6, 1999. The Welsh Assembly opened on May 26, and the Scottish Parliament opened on July 1, 1999. The devolved legislatures have largely taken over most of the functions previously performed by the Scottish and Welsh offices.

Northern Ireland had its own Parliament and prime minister from 1921 to 1973, when the British Government imposed direct rule in order to deal with the deteriorating political and security situation. From 1973, the Secretary of State for Northern Ireland, based in London, was responsible for the region, including efforts to resolve the issues that lay behind the "the troubles."

By the mid-1990s, gestures toward peace encouraged by successive British governments and by President Clinton began to open the door for restored local government in Northern Ireland. An Irish Republican Army (IRA) cease-fire and nearly 2 years of multiparty negotiations, led by former U.S. Senator George Mitchell, resulted in the Good Friday Agreement of 10 April 1998, which was subsequently approved by majorities in both Northern Ireland and the Republic of Ireland. Key elements of the agreement include devolved government, a commitment of the parties to work toward "total disarmament of all paramilitary organisations," police reform, and enhanced mechanisms to guarantee human rights and equal opportunity. The Good Friday Agreement also called for formal cooperation between the Northern Ireland institutions and the Government of the Republic of Ireland, and it established the British-Irish Council, which includes representatives of the British and Irish Governments as well as the devolved Governments of Northern Ireland, Scotland, and Wales. Devolved government was reestablished in Northern Ireland in December 1999.

The Agreement (more commonly known as the "Good Friday Agreement", and more rarely as the Belfast Agreement<ref>http://www.nio.gov.uk/index/key-issues/the-agreement.htm</ref>) was reached on Friday, April 10, 1998 in Belfast and provides for a 108-member elected Assembly, overseen by a 12-minister Executive Committee (cabinet) in which unionists and nationalists share leadership responsibility. Northern Ireland elects 18 representatives to the Westminster Parliament in London. However, the five Sinn Féin Members of Parliament (MPs), who won seats in the 2004 election, have refused to claim their seats.

===Political conditions===

[[David Cameron]] became Prime Minister on May 11, 2010, after [[Gordon Brown]] resigned, and led a [[Conservative Party|Con]]-[[Liberal Democrats|Dem]] coalition in 2010.<ref>[http://news.bbc.co.uk/1/hi/8676607.stm "David Cameron and Nick Clegg pledge 'united' coalition"] ''BBC News'', Election 2010.</ref> In 2015, a general election was called<ref>Under the provisions of the Fixed-term Parliaments Act 2011 (c. 14), parliamentary elections in the UK must be held every five years, beginning in 2015. The Act received Royal Assent on 15 September 2011. Fixed-term Parliaments, where general elections ordinarily take place in accordance with a schedule set far in advance, were part of the Conservative–Liberal Democrat coalition agreement which was produced after the 2010 general election.</ref> and Cameron's Conservative Party won a majority of seats, against all odds.<ref>[http://www.telegraph.co.uk/news/politics/conservative/11599600/How-did-the-Conservatives-win-the-general-election.html "How did the Conservatives win the general election?"] ''The Daily Telegraph''</ref>

===Membership in the European Union===

The [[Conservative Party|Conservative]] government of [[Edward Heath|Sir Edward Heath]] took the UK into the [[European Union]] in 1973. The [[Labour Party]] under [[Harold Wilson]] won the 1974 general elections and due to splits within the party, called the only national [[referendum]] asking the people if they wanted to stay in the Union. The "yes" vote won by a margin of approximately two to one. The Labour and Conservative parties have since had deep divisions over Union membership. Labour's 1983 manifesto promised to leave the Union, and whilst the Conservative party have never pledged to leave the Union, a growing band of "Eurosceptics" threatened to tear the party apart in the 1990s. The Labour, Conservative and Scottish National parties wish to stay in the Union although disagree over the level of integration, but smaller parties such as the [[UK Independence Party]] and the Referendum Party campaigned on the single issue of sovereignty being lost to the Union.

The United Kingdom European Union membership referendum, is scheduled to take place in the United Kingdom and [[Gibraltar]] on 23 June 2016.<ref>{{cite web|url=http://www.publications.parliament.uk/pa/bills/cbill/2015-2016/0002/cbill_2015-20160002_en_2.htm#pb1-l1g5 |title=European Union Referendum Bill (HC Bill 2) |publisher=Publications.parliament.uk |date=2015-05-28 |accessdate=2015-06-12}}</ref><ref>{{cite web|author=Rowena Mason , Nicholas Watt, Ian Traynor, Jennifer Rankin |url=http://www.theguardian.com/politics/2016/feb/20/cameron-set-to-name-eu-referendum-date-after-cabinet-meeting |title=EU referendum to take place on 23 June, David Cameron confirms | Politics |publisher=The Guardian |date=20 February 2016 |accessdate=2 February 2016}}</ref> In accordance with a [[Conservative Party]] manifesto commitment, the legal basis for a referendum was established by the passage of the European Union Referendum Act 2015 by the British Parliament. It will be the third plebiscite to be held throughout the United Kingdom, and the second time the British electorate has been asked to vote on the issue of European Union membership: the first was held in 1975, when it was known as the EEC. Membership was approved in that referendum by 67% of voters – but the nature of the EU has changed dramatically since then and the result of this referendum is expected to be significantly closer.<ref>Adrian Williamson, [http://www.historyandpolicy.org/policy-papers/papers/the-case-for-brexit-lessons-from-1960s-and-1970s The Case for Brexit: Lessons from the 1960s and 1970s], History and Policy (2015).</ref>

==Defense and Foreign Relations==

[[File:11943452 115b299206.jpg|right|240px]]
The United Kingdom is a founding member of the [[North Atlantic Treaty Organization]] (NATO) and is one of NATO's major European maritime, air, and land powers; it ranks third among NATO countries in total defence expenditure. The United Kingdom has been a member of the European Community (now European Union) since 1973. In the United Nations, the United Kingdom is a permanent member of the Security Council. The U.K. held the Presidency of the G-8 during 2005; it held the EU Presidency from July to December 2005.

The British Armed Forces are charged with protecting the United Kingdom and its overseas territories, promoting Britain's wider security interests, and supporting international peacekeeping efforts. The 37,000-member Royal Navy, which includes 6,000 Royal Marine commandos, is in charge of the United Kingdom's independent strategic nuclear arm, which consists of four Trident missile submarines. The British Army, consisting of approximately 99,200 personnel, the Royal Air Force, with 42,000 personnel, along with the Royal Navy and Royal Marines, are active and regular participants in NATO and other coalition operations. Approximately 9% of the British Armed Forces is female, and 4% of British forces represent ethnic minorities.
[[File:Royal Naval college UK.jpg|thumb|center|380px|Royal Naval College.]]

===Iraq===

The U.K. was the United States' main coalition partner under the designation Operation TELIC. Under UN Security Council Resolution 1483, the U.K. also shared with the United States responsibility for civil administration in Iraq and was an active participant in the Coalition Provisional Authority before the handover of Iraqi sovereignty on June 28, 2004. Britain's participation in the Iraq war and its aftermath remains a domestically controversial issue.

<blockquote>
Iraqi oil supply was considered to be 'vital' to British interests. The British Government saw Iraqi oil as "vital" to the UK's long-term energy security, and the effective privatisation of its oil industry was central to the post-invasion plan for the country, according to previously unseen Whitehall documents. [http://www.independent.co.uk/news/uk/politics/iraqi-oil-supply-was-considered-to-be-vital-to-british-interests-2270072.html] ''The Independent.''
</blockquote>

The Iraq Inquiry is conducted to identify lessons that can be learned from the Iraq conflict; the inquiry is concerned over Mr. Blair's evidence on the legal advice he received before agreeing to join the invasion, and the timing of the decision to go to war. [http://www.independent.co.uk/news/uk/home-news/chilcot-to-grill-blair-on-how-he-misled-iraq-war-inquiry-2185725.html] The Chair of the Inquiry, Sir John Chilcot (1939) was Staff Counsellor to the Security and Intelligence Agencies (1999-2004) and the National Criminal Intelligence Service (2002–06).

===Afghanistan===

Britain stood shoulder to shoulder with the United States following the September 11, 2001 terrorist attacks in the U.S., and its military forces are part of the coalition force in Afghanistan. The British force in [[Afghanistan War|Afghanistan]] is at 9,000 in late 2009 and will rise by an extra 500 troops in 2010. British forces are primarily based in the Helmand region, where they are on the front line in the war against continued Taliban operations. In addition, Britain has contributed more than £500 million to Afghan reconstruction—the second-largest donor after the U.S.

===Israel===

Britain has shown a greater willingness than the United States to criticize the Israelis over settlements and what some call the disproportionate responses to provocations from Gaza and southern Lebanon. (Jewish Labour MP Gerald Kaufman is among the most vocal.) Like his predecessors, both Labour and Conservative, former Foreign Secretary Milliband has been unequivocal: "Settlements are illegal under international law," he told Parliament in 2008; "They are a major blockage to peace in the Middle East on the basis of a two-state solution." His successor William Hague, on 20 March 2011, "expressed our serious concern over the recent announcement of 400 new housing units in the West Bank. Continued settlements run contrary to peace.” A BBC poll in March 2011 found that 14% of British subjects have a generally positive opinion of Israel while 66% have a generally negative opinion.

===Relations with the United States===

[[File:Send_a_gun_to_a_British_home.jpg|thumb|right|[[Second Amendment]]-supporting [[American]] [[citizen]]s gifted their [[firearm]]s to [[gun free zone]]-[[gun control]] supporting British citizens during [[World War II]] via [[The American Committee for the Defense of British Homes]]]]

The United Kingdom is one of the United States' closest allies, and British foreign policy emphasises close coordination with the United States. Bilateral cooperation reflects the common language, ideals, and democratic practices of the two nations. Relations were strengthened by the countries' alliances during both World Wars, and its role as a founding member of NATO, in the Korean conflict, in the Persian Gulf War, and in the 2003 invasion of Iraq. The United Kingdom and the United States continually consult on foreign policy issues and global problems and share major foreign and security policy objectives.

The United Kingdom is the fifth-largest market for U.S. goods exports after Canada, Mexico, Japan, and China, and the sixth-largest supplier of U.S. imports after Canada, China, Mexico, Japan, and Germany. U.S. exports of goods and services to the United Kingdom in 2006 totaled $92 billion, while U.S. imports from the U.K. totaled $93 billion. The United States has had a trade deficit with the United Kingdom since 1998. The United Kingdom is a large source of foreign tourists in the United States. In 2005, 3.4 million U.S. residents visited the United Kingdom, while 4.2 million U.K. residents visited the United States.

The United States and the United Kingdom share the world's largest foreign direct investment partnership. U.S. investment in the United Kingdom reached $324 billion in 2005, while U.K. direct investment in the U.S. totaled $282 billion. This investment sustains more than 1 million American jobs.

==Economy==

[[File:London.jpg|thumb|left|280px|London's financial center.]]
Britain has been hard hit by the [[Recession of 2008]], with its major banks taken over or subsidized by the government. Real gross domestic product declined by 4.6% in 2009, and is expected to rise by 0.6% before 2010 and probably will continue to increase by 1% in 2011.

Britain has the fifth-largest economy in the world, is the second-largest economy in the European Union, and is a major international trading power. A highly developed, diversified, market-based economy with extensive social welfare services provides most residents with a high standard of living. Unemployment and inflation levels are amongst the lowest within the European Union.

Since 1979, the British Government has privatised most state-owned companies, including British Steel, British Airways, British Telecom, British Coal, British Aerospace, and British Gas, although in some cases the government retains a "golden share" in these companies. The previous Labour government continued the privatisation policy of its Conservative predecessor, particularly by encouraging "public-private partnerships" (partial privatisation) in such areas as the London Underground. The economy of the United Kingdom is now primarily based on private enterprise, accounting for approximately four-fifths of employment and output.
[[File:Bluewater Shopping Centre, Kent, England Crop 2009.jpg|thumb|440px|Bluewater Shopping Centre, Kent, 2009.]]
London ranks alongside New York as a leading international financial centre. London's financial exports contribute greatly to the United Kingdom's balance of payments. Ratings agencies rank the United Kingdom's banking sector as one of the strongest in the world and its banks are amongst the most profitable in the G-8. It is a global leader in emissions trading and is home to the Alternative Investment Market (AIM). It is also a government priority to make London the leading center of Islamic finance.

Britain is the European Union's only significant energy exporter. It is also one of the world's largest energy consumers, and most analysts predict a shift in U.K. status from net exporter to net importer of energy by 2020, possibly sooner. Oil production in the U.K. is levelling off. While North Sea natural gas production continues to rise, gains may be offset by ever-increasing consumption. North Sea oil and gas exploration activities are shifting to smaller fields and to increments of larger, developed fields, presenting opportunities for smaller, independent energy operators to become active in North Sea production.
*GDP (at current market prices, 2007 est.): US$1.93 trillion.
*Annual growth rate (2009 est.): -4.6%
*Per capita GDP (2006 est.): US$31,800.
*Natural resources: Coal, oil, natural gas.
*Agriculture (1.1% of GDP): Products—cereals, oilseed, potatoes, vegetables, cattle, sheep, poultry, fish.
*Industry: Types—steel, heavy engineering and metal manufacturing, textiles, motor vehicles and aircraft, construction (5.2% of GDP), electronics, chemicals.
*Trade (2006 est.): Exports of goods and services—US$468.8 billion: manufactured goods, fuels, chemicals; food, beverages, tobacco. Major markets—U.S., European Union. Imports of goods and services—US$603 billion: manufactured goods, machinery, fuels, foodstuffs. Major suppliers—U.S., European Union, Japan.

===Currency===

The currency of the United Kingdom is the [[Pound|Pound Sterling]], commonly called Pound and written £ or GBP, divided into 100 New Pence (now commonly just called pence or 'p'). Traditionally the UK had a complicated triple currency structure of 20 [[shilling]]s to the Pound and 12 "old pence" (represented by a "d" from the Roman ''denarius'') to the shilling, making a total of 240 pence to the Pound. This system was abandoned in 1971 due to difficulties with computerised accounting systems, in favour of the current [[decimal]] system.

The UK has never joined the [[Euro]] zone.

==History==

[[File:Stonehenge.jpg|thumb|left|Stonehenge.]]
The Roman invasion of Britain in 43AD and most of Britain's subsequent incorporation into the Roman Empire stimulated development and brought more active contacts with the rest of Europe. However, there was no permanent Roman imprint apart from roads and locations for cities. As Rome's strength declined, the country again was exposed to invasion—including the pivotal incursions of the Angles, Saxons, and Jutes in the fifth and sixth centuries AD—up to the Norman conquest in 1066. Norman rule effectively ensured Britain's safety from further intrusions; certain institutions, which remain characteristic of Britain, could develop. Among these are a political, administrative, cultural, and economic centre in London; a separate but established church and distinctive and distinguished university education.

====Union====

Both Wales and Scotland were independent kingdoms that resisted English rule. The English conquest of Wales succeeded in 1282 under Edward I, and the Statute of Rhuddlan established English rule 2 years later. To appease the Welsh, Edward's son (later Edward II), who had been born in Wales, was made Prince of Wales in 1301. The tradition of bestowing this title on the eldest son of the British Monarch continues today. An act of 1536 completed the political and administrative union of England and Wales.

While maintaining separate parliaments, England and Scotland were ruled by the same king beginning in 1603, when James VI of Scotland succeeded his cousin Elizabeth I as James I of England. In the ensuing 100 years, strong religious and political differences divided the kingdoms. Finally, in 1707, England and Scotland were unified as Great Britain, sharing a single Parliament at Westminster.

Ireland's invasion by the Anglo-Normans in 1170 led to centuries of strife. Successive English kings sought to conquer Ireland. In the early 17th century, large-scale settlement of the north from Scotland and England began. After its defeat, Ireland was subjected, with varying degrees of success, to control and regulation by Britain.

The legislative union of Great Britain and Ireland was completed on January 1, 1801, under the name of the United Kingdom of Great Britain and Ireland (normally shortened to "Great Britain" or "Britain"). However, armed struggle for independence continued sporadically into the 20th century. The Anglo-Irish Treaty of 1921 established the Irish Free State, which subsequently left the Commonwealth and became a republic after World War II. Six northern, predominantly [[Protestant]], Irish counties have remained part of the United Kingdom.

====British Expansion and Empire====

[[Image:Sir Francis Grant's Portrait of Queen Victoria.jpg|right|200px|thumb|''Queen Victoria'', by [[Sir Francis Grant]].]]
The '''British Empire''' was the [[List of largest empires|largest empire]] in history and, for over a century, was the foremost [[Great power|global power]]. It was a product of the [[Age of Discovery]], which began with the maritime explorations of the 15th century, that sparked the era of the European [[Colonialism|colonial]] empires. By 1921, the British Empire held sway over a population of about 458 million people, approximately one-quarter of the world's population.<ref>Angus Maddison. ''The World Economy: A Millennial Perspective'' (p. 98, 242). [[Organisation for Economic Co-operation and Development|OECD]], Paris, 2001.</ref> It covered about 36.7 million km² (14.2 million square miles),<ref>Bruce R. Gordon. [http://www.hostkingdom.net/earthrul.html ''To Rule the Earth...''] (See [http://www.hostkingdom.net/Bibliography.html Bibliography] for sources used.)</ref> about a quarter of Earth's total land area. As a result, its political, linguistic and cultural legacy is widespread. At the peak of its power, it was often said that "[[The empire on which the sun never sets|the sun never sets on the British Empire]]" because its span across the globe ensured that the sun was always shining on at least one of its numerous [[colonies]] or subject nations.<ref>This phrase had already been used a few centuries before by the king [[Charles I of Spain]], referring to the [[Spanish Empire]].</ref>

Begun initially to support William the Conqueror's (c. 1029-1087) holdings in France, Britain's policy of active involvement in continental European affairs endured for several hundred years. By the end of the 14th century, foreign trade, originally based on wool exports to Europe, had emerged as a cornerstone of national policy.

During the five decades following [[World War II]], most of the territories of the Empire became independent. Many went on to join the [[Commonwealth of Nations]], a free association of independent states.<ref>T. O. Lloyd, ''The British Empire, 1558-1995. 2nd ed. (1996).</ref> Some have retained the [[British monarch]] as their [[head of state]] to become independent [[Commonwealth realm]]s.

====Sea Power====

The foundations of sea power were gradually laid to protect English trade and open up new routes. Defeat of the Spanish Armada in 1588 firmly established England as a major sea power. Thereafter, its interests outside Europe grew steadily. Attracted by the spice trade, English mercantile interests spread first to the Far East. In search of an alternate route to the Spice Islands, John Cabot reached the North American continent in 1498. Sir Walter Raleigh organized the first, short-lived colony in Virginia in 1584, and permanent English settlement began in 1607 at Jamestown, Virginia. During the next two centuries, Britain extended its influence abroad and consolidated its political development at home, as the Royal Navy dominated the seas.

====Industrial Revolution====

[[File:Bradford Industrial Museum.jpg|thumb|left|Bradford Industrial Museum.]]
Britain's [[industrial revolution]] greatly strengthened its ability to oppose Napoleonic France. By the end of the Napoleonic Wars in 1815, Britain was the foremost European power, and its navy ruled the seas. Peace in Europe allowed the British to focus their interests on more remote parts of the world, and, during this period, the British Empire reached its zenith. British colonial expansion reached its height largely during the reign of [[Queen Victoria]] (1837-1901). [[Victorian era|Queen Victoria's]] reign witnessed the spread of British technology, commerce, language, and government throughout the British Empire, which, at its greatest extent, encompassed roughly one-fifth to one-quarter of the world's area and population. It is controversial whether British colonies accelerated or slowed Britain's economic growth, for its growth rate fell below nations without empires, especially the U.S. and [[Germany]]. Democracy came in fits and starts in a series of reforms that finally, by the 1920s, allowed all adults to vote.

 

====End of Empire====

By the time of Queen Victoria's death in 1901, other nations, including the United States and Germany, had developed their own industries; Britain lost its comparative economic advantage, and the ambitions of its rivals had grown. The UK joined world war I because of the invasion of [[Belgium]], and subsequently began [[World War II]] after the invasion of [[Poland]]. The losses and destruction of [[World War I|The First World War]], the [[Great Depression]] of the 1930s, the independence of the Dominions, and decades of relatively slow growth eroded the Britain's preeminent international position of the previous century.

Nationalism became stronger in other parts of the empire, particularly in India and Egypt.

In 1926, Britain granted Australia, Canada, and New Zealand almost complete autonomy as "dominions"; beginning with the independence of India and Pakistan in 1947, the remainder of the British Empire was almost completely dismantled by the 1960s.

== See also ==

*[[English Painting]]
*[[British politics]]
*[[June 2007 UK terror attacks]]
*[[List of political parties in the United Kingdom]]
*[[Mystery:Why is England More Liberal than the United States?]]
*[[Flags of the United Kingdom]]
* [[Piers Morgan]]
*[[Victorian era]]

== External links ==

*[http://www.guardian.co.uk/world/2009/nov/15/sir-john-chilcot-wrong-man Sir John Chilcot 'wrong man to head Iraq invasion inquiry'.]
*[http://www.independent.co.uk/news/uk/politics/iraqi-oil-supply-was-considered-to-be-vital-to-british-interests-2270072.html Iraqi oil supply was considered to be 'vital' to British interests.]

== Notes ==
<references/>

{{European Union}}

[[Category:United Kingdom|United Kingdom]]
[[Category:European Countries]]
[[Category:NATO Members]]
[[Category:Christian-Majority Countries]]
[[Category:British Empire]]
[[Category:European History]]
[[Category:Liberalism]]
[[Category:Socialism]]
[[Category:Welfare State]]
[[Category:Gun Control]]
[[Category:Nuclear Target Structures]]

Cosmic microwave background

2016-09-09T19:45:48Z

Harryk: Rephrasing

'''Cosmic microwave background''' (CMB) radiation describes the [[electromagnetic wave]]s that propagate through our entire universe.

=="Scientific" explanation==

The usual explanation of the CMB radiation trotted out by [[atheistic]] scientists is that it is left-over radiation from the [[Big Bang]], namely the radiation scattering off of the opaque, dense plasma of the early universe just before the transition to the transparent universe we observe today. This transition, called "last scattering", is believed to have occurred approximately 380,000 years after the big bang.

==Biblical explanation==

The scientific version of events doesn't agree with [[creation science]], as it requires the universe be ''at least'' 380,000 years old for the transition to have occurred. However, scholarly analysis of the [[Bible]] indicates that the universe is around 6000 years old, which is backed up by many observations in many fields from geology to astronomy.

A possible explanation for the CMB is that it is the light (Genesis 1:2) from the moment of the [[Creation]] around the universe. If the [[Lord]] had suddenly created the universe and flooded it with perfectly uniform light (electromagnetic waves), we would indeed see the remnants to this day, except for minuscule variations introduced by a fraction of the light being blocked by the Earth (which of course preceded the light, Genesis 1:1).

==Characteristics==

One interesting feature of the CMB is that it provides a rest frame against which one can measure the motion of galaxies and other astronomical objects. Since the cosmic microwave background is made of electromagnetic waves, a moving observer will observe a [[Doppler shift]] of the cosmic microwave background, whereas a stationary observer will not. Since the frequency of the cosmic microwave background is known (160.2 GHz <ref name="physorg">http://www.physorg.com/tags/cosmic+microwave+background/</ref>), the velocity of the observer can easily be calculated. Our very Earth sees a Doppler shift in the cosmic microwave background, a shift that must be subtracted from measurements of the CMB to obtain its true temperature distribution.

The thermal black-body spectrum of the cosmic microwave background is 2.725 K.<ref name="physorg"/>

==See also==
*[[Gravitational lensing]]

==Notes==
<references/>

[[Category:Physics]]
[[Category:Astronomy]]
[[Category:Cosmology]]

Positron

2016-09-09T19:13:51Z

Harryk: Created the page

A '''positron''' is the [[antimatter]] version of an [[electron]]. As such, it has the same mass, but opposite charge.

Star

2016-09-09T19:01:05Z

Harryk:

[[Image:Moooghj.jpg|300px|right]]'''Stars''' are extremely large, luminous bodies of gas. They are the most obvious features found in the [[universe]]. They are principally composed of [[hydrogen]] that is undergoing nuclear [[fusion]] to become [[helium]]. Our sun, ([[Sol]]), is the nearest star to Earth, at a distance averaging 93 million miles. The Earth orbits the sun in a period of approximately 365.25 days, and this defines the [[year]]. The diameter of the sun, which is a typical star, is about 870,000 miles and its power output is about 1026 watts. The temperature inside the sun is estimated to be in excess of ten million degrees, and this is hot enough for [[nuclear reactions]] to occur.

In Genesis, the stars were made in the fourth day,<ref>[Genesis 1-8 (Translated)|Gen 1:14]</ref> and their number is compared to the number of descendants of Abraham.<ref>[Genesis 9-16 (Translated)|Gen 15:5]; an earlier count of the number of descendants of Abraham was the number of grains of dust of the Earth (Gen 13:16)</ref>

The [[Bible]] implies that the number of stars is virtually countless,<ref>[Jeremiah 27-34 (Translated)|Jeremiah 33:22]; similarly to Genesis, the number of descendants of David is compared to the number of stars and the number of grains of sand</ref> but for many years this was not accepted. [[Hipparchus]] in 128 B.C. stated there were 1,026 stars in the sky. [[Kepler]] in 1600 A.D. did his own count and found the number to be 1,005. Today, thanks to telescopes (especially the [[Hubble Telescope]]) showing many stars previously too dim to be seen, we are now aware of some 70,000,000,000,000,000,000,000,000 (7*1025) stars.<ref>[http://www.cnn.com/2003/TECH/space/07/22/stars.survey Star survey reaches 70 sextillion]</ref>

==Measuring stellar positions==
=== Distances ===
The oldest method of measuring the distance from our solar system to a distant star is the parallax method. To use this method, astronomers measure the right ascension on the sky of the star at two times of the year, half a year apart. The two measurements will differ by a small angle with respect to the most distant stars in that region of the sky. Exactly half this angle is the ''parallax angle'', having symbol ''p''. This is the angle that the star makes with the [[sun]] and the position of the [[earth]] at a right angle with that star.<ref name=Britannica3>"[http://www.britannica.com/eb/article-52809/star Star: Determining stellar distances]." ''Encyclopædia Britannica''. 2008. Encyclopædia Britannica Online. Accessed 21 Apr. 2008</ref> The distance s of the star, in astronomical units (AU), is:

<math>\,\!s = \cot p</math>

In the range of the very small angles typically encountered, the cotangent of the angle measure (in radians) is very nearly equal to the reciprocal, and thus:

<math>\,\!s \approx \frac {180 \times 3600}{p \times \pi}</math>

where p is measured in seconds of arc.

The cotangent of one second (1/3600 of a degree) of arc is approximately 206,264.81. No parallax angle for any star will be larger than one second. Therefore, astronomers initially defined a unit of stellar distance, the ''parsec'' (symbol pc), from this relationship. One parsec is the distance corresponding to a parallax angle of one second of arc. Hence:

<math>1 pc \approx 206,264.81 AU</math>

However, the error of measurement of parallax angle is 0.005 arc seconds, and beyond a distance of 100 parsecs, this error becomes significant. 700 stars are near enough to measure their distances directly by using parallax.<ref name=Britannica3/> To measure distances further out than this, astronomers typically use absolute and relative magnitudes, or they apply [[Hubble Law|Hubble's Law]] to the star's estimated [[redshift]].

=== Positions in sky ===
The most common system for describing the position of a star in the sky is the equatorial system. This system uses two coordinates:
# Right ascension on the sky, or the number of hours required for the earth to rotate before an observer can see the star at its highest point in the sky. The zero for right ascension is midnight on the day of the vernal equinox.<ref name=WeissteinRA>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/RightAscension.html Right Ascension]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>
# Declination, or the north-south angle between the star and the celestial equator.<ref name=WeissteinD>Weisstein, Eric W. "[http://scienceworld.wolfram.com/astronomy/Declination.html Declination]." ''Eric Weisstein's World of Astronomy'', 2007. Accessed April 21, 2008.</ref>

===Proper motion===
All stars move, but the most distant stars are considered "fixed" because their motion would be undetectable. The ''proper motion'' (symbol m) of any star is the angular velocity of its position across the sky. This describes the motion at right angles to the line of sight of the observer. To convert this to actual ''tangential velocity'', multiply the tangent of this angular velocity by the star's distance.

The motion ''in'' line of sight, or ''radial velocity'', is currently determined from spectral shift.

== Measuring stellar magnitudes ==
The visual magnitude system is defined as follows: a star of any given magnitude is about 2.512 times as bright as is a star of the next magnitude. [[Hipparchus]] devised the magnitude system, and [[Ptolemy]] refined it further. By convention, an arbitrary sample of the twenty brightest stars that they could observe were assigned to the first magnitude, and the stars that they could barely observe were assigned to the sixth. Sixth-magnitude stars are actually 100 times less bright than first-magnitude stars. Magnitude levels between these extremes are assigned on a logarithmic scale. Thus, given two stars of brightness l1 and l2, their magnitude difference (V2 - V1) relates to their respective brightnesses in this way:<ref name=Haworth>Haworth, David. "[http://www.stargazing.net/david/constel/magnitude.html Star Magnitudes]." ''[http://www.stargazing.net/david/index.html Observational Astronomy]'', 2003. Accessed April 21, 2008.</ref>

<math>\,\!V_2 - V_1 = 2.5 \times \log \frac{l_1}{l_2}</math>

The ''absolute'' magnitude of any star is the visual magnitude that it would have if it were ten parsecs distant. To convert apparent magnitude V to actual magnitude M, use this formula:

<math>\,\!M = V + 5 \times \log \frac{s_0}{s}</math>

where s0 is the standard distance. This distance is ten parsecs, or about 2,062,650 AU.

Brightness declines with the square of distance, and squares correspond to doubling of logarithms. One must then multiply that result by 2.5 to stay within the magnitude scale.

== Stellar colors and spectra ==
The ''color'' of a star is objectively quantifiable. To determine color, astronomers view the star through a variety of colored filters and compute ''color indices'' as the differences in apparent magnitudes through the various filters. Stellar colors vary, in order from the coolest to the hottest, from red to yellow to white to blue-white to blue or violet. This is the same gamut of colors that a black body shows as its temperature rises.

In addition, each star has a unique ''spectrum'', which depends on the gases and other elements that it contains, and their distribution. A spectrum can serve two purposes:
# It can serve as a unique signature for the star, to distinguish it from other stars.
# It can provide information on the star's radial velocity vis-à-vis the earth.

To accomplish the latter, astronomers note the placement of various lines in the spectrum and then determine the star's likely constituent elements from the spacing of those lines. Lines that are out of ''place'' are shifted, either toward the blue or toward the red. Nearly all stellar spectra are shifted toward the red; this [[redshift]] indicates a recession, either of the star or of the part of space where the star resides.<ref>Some [[cosmology|cosmological]] models call for an expansion of space itself, not merely the matter in it. According to these models, a redshifted star is in a part of space that was still expanding as the incident light was generated.</ref>

=== Spectral Type ===
[[Image:Hertzsprung-Russell.jpg|thumb|300px|right|Hertzsprung-Russell Diagram]]
In the late nineteenth century, astronomers at the [[Harvard University]] observatory developed the first classification scheme for stellar spectra that would become known as the '''Harvard spectral classification'''. In 1924, Annie Jump Cannon<ref name=Cannon>"[http://imagine.gsfc.nasa.gov/docs/teachers/lifecycles/LC_main_p8.html Life Cycles of Stars]." ''Goddard Space Flight Center'', November 21, 2002. Accessed April 22, 2008.</ref> refined the classification from the original A-Q gamut to the familiar "OBAFGKM" gamut. Astronomers have since added classes to this range at the high end and the low.<ref name=Swinburne>"[http://astronomy.swin.edu.au/cosmos/H/Harvard+Spectral+Classification Harvard Spectral Classification]." ''Study Astronomy Online at Swinburne University''. Accessed April 22, 2008.</ref><ref name=Seattle>Irizarry, David. "[http://www.seattleastro.org/webfoot/feb00/pg2.htm The Secrets of the Harvard Classification Revealed]." ''The Webfooted Astronomer'', Seattle Astronomical Society, February 2000. Accessed April 22, 2008.</ref>

The classic Harvard spectral classes are O, B, A, F, G, K, and M. Each of these has ten subclasses, varying from 0 to 9 in order of decreasing stellar temperature. Thus, for example, the next class after an F9 star is a G0 star. Recently astronomers recognized one class of stars hotter than the O stars (the very hot Wolf-Rayet stars) and three classes of stars (the N, R, and S stars) cooler than the M stars. (Some astronomers include the N and R stars in one class, the C stars, for the carbon compounds that their spectra exhibit). There is an additional spectral class for the smallest and dimmest stars (Class L), that still fuse hydrogen, although warmer [[brown dwarf]]s also fall into this class (but referred to as L dwarfs instead of L stars). Cooler still methane dwarfs are classified as [[Brown dwarf#Spectral class T|T dwarfs]].<ref>http://adsabs.harvard.edu/abs/2007arXiv0704.1522K</ref> A proposed spectral class Y has been suggested for the coolest brown dwarfs, which also have a different spectra from T class dwarfs.<ref>http://xxx.lanl.gov/abs/astro-ph/0607305</ref>

{| class="wikitable"
|-
! Class
! [[Temperature]]
! Color
! [[Element]]s
! Notes
|-
| W
| 106,000 K
| Violet
| Ionized [[helium]], [[carbon]], [[oxygen]], [[nitrogen]]
| Wolf-Rayet stars. Additional subclasses include WC (overabundant carbon and oxygen) and WN (overabundant nitrogen)
|-
| O
| 30,000 K
| Blue
| Ionized [[Helium]], [[nitrogen]], [[oxygen]]
| Weak Balmer lines ([[hydrogen]]) at higher subclasses.
|-
| B
| 13,000 K to 20,000 K
| Blue
| Neutral helium; ionized [[silicon]], oxygen and [[magnesium]].
| [[Hydrogen]] (Balmer lines) appear in strength
|-
| A
| 75,00 to 10,000 K
| Blue-white
| [[Hydrogen]], [[calcium]], [[helium]]
| Balmer lines dominant. K lines (calcium) now appearing.
|-
| F
| 7,000K to 9,000K
| White-yellow
| [[Hydrogen]], [[calcium]], [[iron]], [[manganese]], [[sodium]]
| Balmer lines weakening. K lines stronger.
|-
| G
| 5,200 to 6,000K
| Yellow
| [[Calcium]], [[hydrogen]], other [[metal]]s
| Balmer lines weaker still. K lines dominant. Metals now appearing. Contains the sun.<ref>http://www.astrometry.org/starclassification.php

</ref>
|-
| K
| 4000K to 5100K
| Orange
| [[Calcium]], neutral metals, [[titanium oxide]]
|
|-
| M
| 3000K
| Red
| [[Titanium oxide]], [[iron iodide]]
| Strong molecular bands
|-
| N,R
| 2300K to 2600K
| Red
| [[Carbon]] compounds
|
|-
| S
| 2300K to 2600K
| Red
| [[Hydrogen]], [[zirconium oxide]]
|
|}

In the early twentieth century, astronomers Ejnar Hertzsprung and Henry Norris Russell prepared the first plot of stellar temperature as a function of luminosity, or brightness. Other astronomers have since prepared versions of the diagram showing absolute magnitude as a function of color. This diagram shows a "main sequence" of stars for which brightness declines as temperature increases, but also shows a "white dwarf" population of very hot but dim stars, and the population of giants and supergiants that are far brighter than their temperatures would indicate.<ref name=HR>"[http://astronomy.swin.edu.au/cosmos/H/Hertzsprung-Russell+Diagram Hertzsprung-Russell Diagram]." ''Study Astronomy Online at Swinburne University''. Accessed April 22, 2008.</ref>

===Luminosity Class===

In addition to the spectral type, astronomers today add a ''luminosity class'', which varies from 0 to VII in order of decreasing brightness. This is known as the '''Yerkes spectral classification'''. This classification was first developed by astronomers William Wilson Morgan, Phillip C. Keenan and Edith Kellman at the [[Yerkes Observatory]] in 1943.<ref>Morgan, William Wilson; Keenan, Philip Childs; Kellman, Edith (1943), "An atlas of stellar spectra, with an outline of spectral classification", Chicago, Ill., The University of Chicago press</ref> Adding a luminosity classification added a second dimension to the single dimensional [[Harvard University|Harvard]] spectral sequence. Today the two classifications of temperature and luminosity is used to give the spectral sequence for a star.<ref>http://cdsads.u-strasbg.fr/cgi-bin/nph-bib_query?bibcode=1973ARA%26A..11...29M&db_key=AST&data_type=HTML&format=&high=449aa1cc7c02014</ref> For example, the [[sun]]'s spectral type is G2 and its luminosity class is V (five).

{| class="wikitable"
|-
! Luminosity Class
! Star Type
|-
| 0 - 0Ia - Ia0
| hypergiants
|-
| Ia - Iab - Ib
| [[supergiant]]s
|-
| IIa - IIab - IIb
| bright giants
|-
| IIIa - IIIab - IIIb
| giants
|-
| IVa - IVab - IVb
| subgiants
|-
| Va - Vab - Vb
| main sequence stars (dwarfs)
|-
| VI
| subdwarfs
|-
| VII
| [[white dwarf]]s
|}

==Variable stars==

Some stars vary in brightness and are known as variable stars. The star [[Algol]] in the constellation of Perseus can drop from its normal magnitude of 2.3 to magnitude 3.5. This is now known to be caused by a dim companion star orbiting Algol, which occasionally passes between Algol and the Earth, blocking some of the light. Other variable stars vary in brightness due to actual variations in the luminosity of the star itself. The time taken from one maximum brightness to the next one is called the '''period'''. The most famous of the variable stars is delta Cepheus, the first-found member of the [[Cepheid]] group of variable stars. In 1908 [[Henrietta Swan Leavitt]] noticed that the variable stars in the [[Magellenic Clouds]] (two nearby galaxies in the [[Local Group]]) had a relationship between their period and their apparent brightness. At that time galaxies outside our own (the [[Milky Way]]) had been discovered, but it was not possible to measure the distances to them. It was soon realized that the variable stars in the Magellenic Cloud were of the Cepheid type. Since Cepheid variables also occur in our [[galaxy]] it was possible measure their distances and thus convert (using the inverse square law) Leavitt's relationship between apparent brightness and period to one of actual brightness and period. Once this formula was discovered, it became possible to apply to Cepheids of unknown distance. By observing their periods, their actual brightness can be calculated and, by the inverse square law, their distance. Through observations of Cepheids in [[globular cluster]]s (compact bunches of stars) in our galaxy it was shown that our galaxy is about 300,000 light-years in diameter.

== Energy production ==
[[Image:CNO_Cycle.png|300px|thumb|CNO cycle]]The [[Sun]], and stars as massive as the Sun or less massive, commonly use a [[nuclear fusion]] process called the '''proton-proton chain reaction''' to produce [[energy]]. A full description of that process appears [[Sun#Energy production and transport|here]].

In 1938 and 1989, two physicists, Carl F. von Weizsäcker<ref name=Weiz>Von Weizsäcker, Carl F. ''Physik. Zeitsch.'' 39:633, 1938.</ref> and Hans Bethe<ref name=Bethe>Bethe, Hans A. "[http://prola.aps.org/abstract/PR/v55/i5/p434_1 Energy Production in Stars]." ''Physics Review'' 55(5):434-456, 1939. {{doi|10.1103/PhysRev.55.434}} Accessed June 27, 2008.</ref> independently proposed a [[nuclear fusion]] process, the '''Carbon-Nitrogen-Oxygen cycle''', by which stars more massive than the [[sun]] produce energy. In this process, stars convert [[hydrogen]] to [[helium]] using [[carbon]], [[nitrogen]], and [[oxygen]] as catalysts. The reaction also produces two [[positron]]s and two [[neutrino|electron neutrino]]s.<ref name=Krane>Krane, Kenneth S. ''Introductory Nuclear Physics''. New York: John Wiley and Sons, 1988, p. 537. ISBN 9780471805533</ref>

The equations for the cycle are as follows:

<math>{}^{12}_6\!\mbox{C} + {}^1_1\!\mbox{H} \to {}^{13}_7\!\mbox{N} + \gamma + \mbox{1.95 MeV}</math>

<math>{}^{13}_7\!\mbox{N} \to {}^{13}_6\!\mbox{C} + {}^0_1\!e^+ + {}^0_0\!\nu_e + \mbox{2.22 MeV}</math>

<math>{}^{13}_6\!\mbox{C} + {}^1_1\!\mbox{H} \to {}^{14}_7\!\mbox{N} + \gamma + \mbox{7.54 MeV}</math>

<math>{}^{14}_7\!\mbox{N} + {}^1_1\!\mbox{H} \to {}^{15}_8\!\mbox{O} + \gamma + \mbox{7.35 MeV}</math>

<math>{}^{15}_8\!\mbox{O} \to {}^{15}_7\!\mbox{N} + {}^0_1\!e^+ + {}^0_0\!\nu_e + \mbox{2.75 MeV}</math>

<math>{}^{15}_7\!\mbox{N} + {}^1_1\!\mbox{H} \to {}^{12}_6\!\mbox{C} + {}^4_2\!\mbox{He} + \mbox{4.96 MeV}</math>

The last reaction reproduces the <math>{}^{12}_6\!\mbox{C}</math> nucleus that the first reaction consumes. The end result of this process is:

<math>\mbox{4} {}^1_1\!\mbox{H} \to {}^4_2\!\mbox{He} + \mbox{2} {}^0_1\!e^+ + \mbox{2} {}^0_0\!\nu_e + \mbox{3} \gamma + \mbox{26.8 MeV}</math>

Rarely, this cycle branches into a somewhat different cycle involving [[fluorine]], and that second cycle is thought to branch again in some of the most massive stars.

==Origins==
Christian scientists assert that [[materialism|materialistic]] explanations of the origin of stars are errant and contra-evidence and reports of stars forming are invalid.<ref>http://www.icr.org/article/403/</ref><ref>http://www.answersingenesis.org/creation/v18/i2/stars.asp</ref><ref>http://www.creationscience.com/onlinebook/AstroPhysicalSciences21.html</ref><ref>http://www.answersingenesis.org/Docs/399.asp#55</ref><ref>http://www.answersingenesis.org/creation/v19/i1/feedback.asp</ref> In addition, creationists cite the secular scientific literature in order to make the case that materialist explanations of star formation are inadequate:

“We don’t understand how a single star forms, yet we want to understand how 10 billion stars form.” Carlos Frenk, as quoted by Robert Irion, “Surveys Scour the Cosmic Deep,” Science, Vol. 303, 19 March 2004, p. 1750.<ref>http://www.sciencemag.org/cgi/content/summary/303/5665/1750</ref>

“Nobody really understands how star formation proceeds. It’s really remarkable.” Rogier A. Windhorst, as quoted by Corey S. Powell, “A Matter of Timing,” Scientific American, Vol. 267, October 1992, p. 30.<ref>http://adsabs.harvard.edu/abs/1992SciAm.267Q..26P</ref>

==Habitable zone==
A star's habitable zone is the region in which a [[terrestrial planet]] of the right size could have a surface temperature that might allow for liquid water and potentially life.<ref>Bennet, Jeffrey, et al. "Life Around Stars." The Essential Cosmic Perspective. 4th ed. San Francisco: Pearson Education, Inc., 2008. 508-13.</ref>

For example, if a star much similar our [[Sun]] has a lifetime of one million years and temperature of 6094K. Its habitable zone lies within 1.02AU and 1.49AU.<ref>"Exploring the Habitable Zone and Central Star", CADRE design Pty. Ltd.</ref>

==See also==
*[[61 Virginis]]

==References==
<references/>

==Other References==
The ''Observer's Book of Astronomy'', by Patrick Moore. Published by Frederick Warne and Co. 1967.

The ''Cosmological Distance Ladder'', by Michael Rowan-Robinson. Published by Freeman. 1985.

[[Category:Astronomy]]

Inertial frame of reference

2016-09-09T18:56:58Z

Harryk: Redirected page to Inertial reference frame

#REDIRECT [[Inertial reference frame]]

Gas

2016-09-07T17:35:44Z

Harryk:

'''Gas''' is one of the states of [[matter]], in which the [[molecule]]s move about unconstrained by each other and will expand into any available space. Any such fluid used as an anesthetic, as nitrous oxide; any such combustible fluid used as fuel. [http://dictionary.reference.com/browse/gas]

Gas is also short for [[gasoline]]; a volatile, flammable liquid mixture of hydrocarbons, obtained from petroleum, and used as fuel for internal-combustion engines, as a solvent, etc. [http://dictionary.reference.com/browse/gasoline]

Our [[atmosphere]] is mostly composed of gases.

Many gases are colorless, however, some are not. For instance, [[chlorine]] gas is greenish-yellow, and N2O4 is reddish-brown.

<center>
[[File:Volcanic gas.jpg]]

Sulfur dioxide and other volcanic gases rise from the Pu`u `O`o vent on Kilauea Volcano, [[Hawaii]].
</center>

[[Category:Physics]]
[[Category:Chemistry]]

Baryon

2016-09-07T17:23:04Z

Harryk: Minor correction

Baryons are a group of composite particles that contain three quarks (or anti-quarks) that are held together by the strong nuclear force (mediated by [[gluons]]) and exemplify the theory of confinement. The most notable examples of baryons are the nucleons (protons and neutrons).

[[Category:Physics]]

Strong force

2016-09-07T17:21:28Z

Harryk: Created the page

The '''strong force''' (also known as the strong nuclear force) is one of the four [[fundamental interactions|fundamental forces]] of nature. Strong force interactions are mediated fundamentally by the [[gluon]]. The strong force is responsible for binding quarks into [[meson]]s and [[baryon]]s. The strong force is also responsible for binding [[proton]]s and [[neutron]]s together in the nuclei of atom, overcoming the electrostatic repulsion of the protons. However in this case, the strong force is mediated by [[meson]]s.

Standard Model

2016-09-07T17:12:25Z

Harryk:

[[Image:Mioss.jpg|thumb|400px|right|The Standard Model of Fundamental Particles and Interactions]]
The '''Standard Model''' of [[particle]] physics is a [[quantum field theory]] that explains [[electromagnetism]], [[Strong force|strong]] and [[Weak force|weak]] [[nuclear]] interactions in a unified framework. It is a non-[[abelian]] gauge theory with the gauge [[Group (mathematics)|group]] [[Unitary group|SU(3)×SU(2)×U(1)]].

It was formulated in the 1970s and has withstood all experimental tests. It has only been modified by adding mass to the electron neutrino. Physicists have just announced the discovery of its most enigmatic prediction, the [[Higgs boson]].

[[Category:Physics]]

Standard Model

2016-09-07T17:11:34Z

Harryk: Fixed broken link

[[Image:Mioss.jpg|thumb|400px|right|The Standard Model of Fundamental Particles and Interactions]]
The '''Standard Model''' of [[particle]] physics is a [[quantum field theory]] that explains [[electromagnetism]], [[Strong nuclear force|strong]] and [[Weak force|weak]] [[nuclear]] interactions in a unified framework. It is a non-[[abelian]] gauge theory with the gauge [[Group (mathematics)|group]] [[Unitary group|SU(3)×SU(2)×U(1)]].

It was formulated in the 1970s and has withstood all experimental tests. It has only been modified by adding mass to the electron neutrino. Physicists have just announced the discovery of its most enigmatic prediction, the [[Higgs boson]].

[[Category:Physics]]

Gluon

2016-09-07T17:08:11Z

Harryk: Fixed broken links

A '''gluon''' is an [[fundamental particles|fundamental particle]] responsible for the binding of [[proton]]s and [[neutron]]s and the [[fundamental interactions|interaction]] of [[quark]]s. Gluons mediate the strong nuclear force, according to the Standard Model. Gluons carry color charge and have spin 1.

[[Category:Physics]]

Atom

2016-09-07T17:03:29Z

Harryk: Couple of correctionss

[[Image:Atoms1.jpg|thumb|right|Subatomic resolution of atoms by AFM]]
An '''atom''' is
a [[particle]] of [[matter]] indivisible by [[chemical]] means <ref>[http://www.lbl.gov/abc/Glossary.html Glossary of Nuclear Terms]</ref> which form the building blocks of molecules.
Although the word "atom" comes from the Greek term for indivisible, ''átomos'', atoms are actually made up of three different kinds of subatomic particles; some of these are composed of yet smaller particles.

In the atomic [[nucleus]] there are positively charged [[proton]]s and electrically neutral [[neutron]]s. Surrounding the nucleus are negatively charged [[electron]]s. [[Hydrogen]], in its most common [[isotope]], has only one proton and no neutrons.

Protons and neutrons are comprised of [[quark]]s and are contained closely together in the center of an atom, forming the [[nucleus]]. Electrons move in the space around the nucleus, and are arranged around it in a series of layers, known as [[electron shell|shells]] or energy levels. Since protons and neutrons are approximately 2000 times as heavy as electrons, the vast majority of an atom's mass is found in the nucleus. Currently quarks and electrons are considered truly elementary particles. Atoms are mostly empty space, as the relative size of the nucleus compared to the area of the lowest electron shell is about that of a pea in a stadium. Another common analogy for the atom along the same lines is the "fly in the cathedral", where the cathedral is the whole atom and the fly is the nucleus.

Those who understand electrical theory might notice that positively charged particles packed closely together would repel one another. The nucleus stays together because of what is known as the ''strong nuclear force''. The quantization of this force is a particle called a "[[gluon]]".

==Atomic Number==
[[Image:Isotopes.jpg|right|thumb|Isotopes]]
Chemical elements are made up of atoms with certain properties. The number of protons in the nucleus of an atom (known as the [[atomic number]]) determine the properties of the atom, and the element it constitutes. For example, [[Hydrogen]] has one proton, and therefore an atomic number of 1. [[Oxygen]] has 8 protons in its nucleus and has an atomic number of 8. Under normal conditions, atoms contain an equal number of protons and electrons.

==Ions==

Atoms are normally electrically neutral; they have no charge. However, electrons in the [[valence shell]] can be gained or lost (depending on the element and the conditions) to form an [[ion]]. An atom that loses electrons becomes positively charged and is known as a cation. An atom that gains electrons electrons becomes negatively charged and is known as an anion. Anions of the common elements fluorine, chlorine, bromine and iodine are known as fluoride, chloride, bromide and iodide (replacing -ine with -ide), respectively.

Many common substances are made up of ions. For example, [[sodium chloride]] (NaCl), otherwise known as table salt, is made up of [[sodium cations]] (Na+) and [[chlorine]] anions (chloride, Cl-) in equal proportions. The negatively charged chloride ions are attracted to the positively charged sodium ions, forming an [[ionic bond]]. This results in a lattice structure, which is responsible for sodium chloride being crystalline in its solid state.

==Isotopes==

Atoms of the same element that have different numbers of neutrons are known as [[isotope]]s. Some isotopes are more stable than others, and occur more often in nature, but there is no "standard" number of neutrons in a given element. The atomic weight of an element is a weighted average of the number of neutrons and protons (number of protons remains constant in a given element) in all naturally occurring isotopes. Many isotopes are [[radioactive]] and [[radioactive decay|decay]] over time.

==See also==
*[[Geiger–Marsden experiment]]

[[Category:Chemistry]]
[[Category:Physics]]

==References==
<references />

Proton

2016-09-07T16:59:23Z

Harryk: Fixed broken link

'''Protons''' are one of the two types of [[sub-atomic particles]] that form in the [[nucleus]] of an [[atom]] (together with [[neutron]]s).<ref>Serway, Beichner: ''Physics for Scientists and Engineers'', 5th edition</ref>

A proton is made up of two up [[quark]]s and one down quark. According to the [[Standard Model]] of particle physics, quarks are [[fundamental particles]], meaning that they cannot be split into smaller particles.<ref>Krane: ''Modern Physics'', 2nd edition</ref>

==Properties==
*Mass: 1.6726231*10−27 [[kilogram|kg]]
*Charge: 1.60218925*10−19 [[Coulomb|C]]

==References==
<references/>

==See also==

*[[Atom]]
*[[Neutron]]
*[[Electron]]
*[[Periodic table of the elements]]
*[[Quark]]

[[Category:Chemistry]]
[[Category:Physics]]

Element

2016-09-07T16:53:35Z

Harryk: Minor correction

An '''element''' is a single type of [[atom]] as defined by its [[atomic number]], which is the number of [[protons]] in its [[nucleus]].<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> In contrast, a single element may have varying [[mass number]]s, relating to the number of neutrons in its nucleus.

The element [[hydrogen]] has only one proton whereas the element [[uranium]] has 92, and there are elements with even more protons than that. However, uranium is the largest naturally occurring element in nature.

All known elements are listed on the [[periodic table]], with the ones with more protons than uranium produced in a laboratory. Joining atoms of the same or different elements produces chemical [[compound]]s. The elements and their compounds make up all matter on the earth and quite possibly all matter outside of the earth as well.

==See also==
*[[Native element]]
*[[Periodic table of the elements]]

==References==
<references/>

[[Category:Elements| ]]

Electricity

2016-09-07T16:51:13Z

Harryk: Correction

[[Image:Htryt5.jpg|right|thumb|200px|Lightning strikes during a night-time thunderstorm. Energy is radiated as light when powerful electric currents flow through the Earth's atmosphere.]]
'''Electricity''' is [[energy]] that can be converted to heat, light, motion and many other physical effects through the force produced in the attraction or repulsion between charged particles. It is measured in terms of [[electric charge]], [[current]], [[voltage]], and [[resistance]]. A basic element of electricity is the electric circuit. A circuit is a closed path that allows for movement of charges. Current is the name given to the movement of charges. The study of electricity involves the behavior of charges, current and voltage with the components that make up the electrical circuit. Electrical engineering has allowed many practical advances to be made, such as replacing [[steam power]]ed trains with more efficient electric trains.

==Polarity==

All materials that are known contain two basic components of electric charge: the [[proton]] and the [[electron]]. The proton is a particle with a single positive charge, and the electron has a single negative charge.

It is the arrangement of electrons and protons as basic particles of electricity that determines the electrical characteristics of substances. Although all matter has protons and electrons, most materials do not exhibit any evidence of electrical activity, because the protons and electrons arranged in balanced ways. In order to use electricity to do work, the material must contain electrons that are free to move from atom to atom. A battery can do electrical work because a chemical process takes place when it is part of a completed circuit moves electrons towards its negative terminal and conversely, creates a lack of them at its positive terminal. Electrons then flow through the circuit to keep balancing out this chemical process.

Some molecules are said to be "polarized" because their atomic arrangement and electron sharing causes a net charge to develop on opposite sides. Water is a classic example of this, with the electrons from the [[hydrogen]] atoms "spending more time" in proximity to the [[oxygen]] atoms. Since the hydrogen atoms are "attached" to the oxygen asymmetrically (instead of being at opposite sides of the oxygen, the angle between their "attachment points" is 108 degrees), one end of the water molecule carries a positive charge and the other a negative one. This polarization results in water's ability to dissolve [[salt]]s, and display acidic or basic characteristics.

==The Structure of an Atom Determines its Electrical Characteristics==

Although there are many possible ways protons and electrons could group themselves, they assemble in specific combinations that usually result in stable arrangement. An arrangement of protons, electrons, and often [[neutron]]s creates an atom of an [[element]]. Electrons orbit the nucleus of protons and neutrons at specific intervals, called "shells" or "energy levels." Each shell has a maximum number of electrons for stability.
It is the structure of the outermost shell of electrons in an element that determines how well it conducts electricity and its magnetic properties. If an element has fewer than the maximum number of electrons in its outermost shell (typically eight), for example [[silicon]] which has only four electrons, then it can conduct electricity to some degree; the elements that have one electron in their outermost shell conduct electricity best. [[Gold]], [[silver]], and [[copper]] are the best conductors of electricity because their outermost electron shell has only one electron, and this allows the freest flow of electrical current because the opposition of an atom of these elements from taking on or loosing electrons is low.
Materials with electrons that tend to stay in their own orbits are called insulators, because they do not conduct electricity very well. However, these materials (except for the inert gases) can also take up extra electrons to complete their outer shells, and become negatively charged; they hold on to and store electrical charge, unlike conductors. Insulating materials like glass, plastic, rubber, paper, air, and mica are called dielectrics, meaning that they can take on and hold electrical charge. Insulators are useful when it is necessary to prevent current flow. They are also used in applications for storing electrical charge, as in [[capacitor]]s, since a good conductor of electricity can only store charge on its surface, limiting the amount.
Materials that can conduct more electrical charge than insulators, but less than conductors are called semiconductors. [[Carbon]], [[silicon]], and [[germanium]] are commonly used for [[transistor]]s, [[diode]]s and other semiconductor components, with silicon being the most widely used.

==Electrical Power==
In physics, electrical power is the product of current and voltage (''P'' = ''IV''), and is commonly measured in [[Watt]]s. Current can be [[alternating current|alternating]] or [[direct current|direct]]. The electrical power generation market, which provides useful power for residential, commercial, and industrial use, is commonly divided into three segments: generation, transmission, and distribution. Electrical power can be generated in large scale [[power plant]]s or on a smaller scale for distributed power applications.

==Resources==
Grob, Bertand ''Basic Electronics'' Fifth edition, 1984

[[Category:Physics]]
[[Category:Electricity]]

Antimatter

2016-09-07T16:11:28Z

Harryk: Corrections

'''Antimatter''' is composed of fundamental particles that have the same magnitude but opposite sign of [[electric charge]] as those of [[matter]].

[[Matter]], and therefore everything seen, is made out of particles of nature. These particles can be divided into fermions (matter) and bosons (responsible for forces such as electromagnetism and strong nuclear force). Fermions can be further subdivided into baryons and mesons. Hadrons include the proton and neutron and leptons include the [[electron]], [[muon]] and tau as well as the corresponding neutrinos. For simplicity, the overwhelming majority of matter in the universe is comprised of protons, neutrons and electrons. Antimatter is matter formed from antiparticles, which have the same mass but opposite sign of [[charge]] to their corresponding particles. When antimatter is brought into contact with normal matter, both particles are destroyed, resulting in an explosion that is, in terms of mass to explosive power, the most powerful known to mankind. This is because the mass of the particles is totally annihilated. Such an annihilation (e.g. an [[electron]] and a [[positron]]), produces two photons. Two are required by the need to satisfy conservation of both energy and momentum. The total mass of the particles is converted into energy, as described by [[E=mc^2]].

== Discovery ==

In the late 19 and early 20th century antimatter had been the cause of much speculation within the scientific community, With William Hicks, Karl Pearson and Arthur Schuster discussing the idea. The current theory of antimatter was set down in a paper by [[Paul Dirac]] in 1928, when he created his version of the Schrödinger wave equation, designed to be compatible with the [[Theory of relativity]]. This equation for electrons also raised the possibility for the existence of anti-electrons, electrons that had the same mass but opposite charge and spin. Naturally all the other particles of matter would also have their opposites.

The anti-electron was first observed by Dmitri Skobeltsyn in 1929, using a Wilson cloud chamber, and again by Chung-Yao Chao in the same year. But they were first discovered (meaning in this case observed and ''labeled'') by Carl Anderson when he separated the electrons from other types of high energy particles present in cosmic rays based on there mass-to-charge ratio. He found some particles with the same ratio as electrons that moved in the opposite direction when under the influence of a magnet. He had found the anti-electron, which he called the positron.

The anti-proton was first discovered in 1955, by physicists Emilio Segrè and Owen Chamberlain. The first anti-neutron was discovered shortly thereafter in 1956, by Bruce Cork.

== Artificial Antimatter ==

Antimatter is made in supercolliders such as the [[Large Hadron Collider]] by smashing beams of highly charged particles together. This results in pair production, the creation of a particle and its antiparticle. One of the aims of modern physics is the creation of larger and more complex forms of antimatter. In 1995 CERN announced that it had produced 9 antihydrogen atoms. Antihelium was created in 2003. Physicists are now working on the creation of 'cooler' antiatoms, as the ones produced so far are more energetic than atoms on the surface of the sun, and this makes them extremely hard to study. Another issue being studied is that of containment: since antimatter explodes on contact with normal matter, it is difficult to hold it for study. Smaller particles are held in place by carefully managed magnetic fields, but the larger antiatoms, being magnetically neutral, are much harder to contain.

== Natural Antimatter ==

Antimatter is naturally produced by both (β+) decay and by high energy collisions between particles. Antimatter makes up a very small percentage of [[cosmic ray]]s, and is occasionally produced when those rays collide with the earth's atmosphere. Antimatter has also been spotted in the [[Van Allen radiation belt]]s and forming above thunderstorms.

[[Potassium]] 40 will (very) occasionally undergo beta decay, producing an antielectron. As such, the average banana (rich in potassium) will produce a small particle of antimatter every 75 minutes.<ref>http://tertiarysource.net/ts.cgi/anti-banana</ref>

== References ==
<references/>

[[Category:Physics]]

Fundamental interactions

2016-09-07T16:02:39Z

Harryk: Created the page

There are four '''fundamental interactions''' or fundamental forces in nature. They are:
*[[Gravity]]
*[[Electromagnetism]]
*Strong nuclear force
*[[Weak force|Weak nuclear force]]

Quark

2016-09-07T16:00:11Z

Harryk: Fixed broken links

'''Quarks''' are [[fundamental particles]] that are one of the two types of [[fermion]]s, the other being [[lepton]]s. Quarks are the only elementary particles that interact in all four [[fundamental interactions]] of physics. There are six flavors of quarks: up, down, strange, charm, bottom, and top quarks. The [[antimatter|antiparticle]]s of quarks are called antiquarks. Quarks have spin 1/2, baryon number 1/3, and electric charge 1/3 or −2/3. Properties and [[quantum number]]s usually can be found by direct experimenting but confinement of quarks stops any chance of precise measurement.

The word ''quark'' originates from the passage "Three quarks for Muster Mark!/Sure he hasn't got much of a bark/And sure any he has it's all beside the mark." from ''[[Finnegans Wake]]'' by [[James Joyce]].

[[Category:Quantum Mechanics]]

Electricity

2016-09-07T15:11:16Z

Harryk: Small correction

[[Image:Htryt5.jpg|right|thumb|200px|Lightning strikes during a night-time thunderstorm. Energy is radiated as light when powerful electric currents flow through the Earth's atmosphere.]]
'''Electricity''' is [[energy]] that can be converted to heat, light, motion and many other physical effects through the force produced in the attraction or repulsion between charged particles. It is measured in terms of [[electric charge]], [[current]], [[voltage]], and [[resistance]]. A basic element of electricity is the electric circuit. A circuit is a closed path that allows for movement of charges. Current is the name given to the movement of charges. The study of electricity involves the behavior of charges, current and voltage with the components that make up the electrical circuit. Electrical engineering has allowed many practical advances to be made, such as replacing [[steam power]]ed trains with more efficient electric trains.

==Polarity==

All materials that are known contain two basic components of electric charge: the [[proton]] and the [[electron]]. The proton is a particle with a single positive charge, and the electron has a single negative charge.

It is the arrangement of electrons and protons as basic particles of electricity that determines the electrical characteristics of substances. Although all matter has protons and electrons, most materials do not exhibit any evidence of electrical activity, because the protons and electrons arranged in balanced ways. In order to use electricity to do work, the material must contain electrons that are free to move from atom to atom. A battery can do electrical work because a chemical process takes place when it is part of a completed circuit moves electrons towards its negative terminal and conversely, creates a lack of them at its positive terminal. Electrons then flow through the circuit to keep balancing out this chemical process.

Some molecules are said to be "polarized" because their atomic arrangement and electron sharing causes a net charge to develop on opposite sides. Water is a classic example of this, with the electrons from the [[hydrogen]] atoms "spending more time" in proximity to the [[oxygen]] atoms. Since the hydrogen atoms are "attached" to the oxygen asymmetrically (instead of being at opposite sides of the oxygen, the angle between their "attachment points" is 108 degrees), one end of the water molecule carries a positive charge and the other a negative one. This polarization results in water's ability to dissolve [[salt]]s, and display acidic or basic characteristics.

==The Structure of an Atom Determines its Electrical Characteristics==

Although there are many possible ways protons and electrons could group themselves, they assemble in specific combinations that usually result in stable arrangement. Each stable arrangement of protons, electrons, and often [[neutron]]s makes one particular kind of atom, an [[element]]. Electrons orbit the nucleus of protons and neutrons at specific intervals, called "shells" or "energy levels." Each shell has a maximum number of electrons for stability.
It is the structure of the outermost shell of electrons in an element that determines how well it conducts electricity and its magnetic properties. If an element has fewer than the maximum number of electrons in its outermost shell (typically eight), for example [[silicon]] which has only four electrons, then it can conduct electricity to some degree; the elements that have one electron in their outermost shell conduct electricity best. [[Gold]], [[silver]], and [[copper]] are the best conductors of electricity because their outermost electron shell has only one electron, and this allows the freest flow of electrical current because the opposition of an atom of these elements from taking on or loosing electrons is low.
Materials with electrons that tend to stay in their own orbits are called insulators, because they do not conduct electricity very well. However, these materials (except for the inert gases) can also take up extra electrons to complete their outer shells, and become negatively charged; they hold on to and store electrical charge, unlike conductors. Insulating materials like glass, plastic, rubber, paper, air, and mica are called dielectrics, meaning that they can take on and hold electrical charge. Insulators are useful when it is necessary to prevent current flow. They are also used in applications for storing electrical charge, as in [[capacitor]]s, since a good conductor of electricity can only store charge on its surface, limiting the amount.
Materials that can conduct more electrical charge than insulators, but less than conductors are called semiconductors. [[Carbon]], [[silicon]], and [[germanium]] are commonly used for [[transistor]]s, [[diode]]s and other semiconductor components, with silicon being the most widely used.

==Electrical Power==
In physics, electrical power is the product of current and voltage (''P'' = ''IV''), and is commonly measured in [[Watt]]s. Current can be [[alternating current|alternating]] or [[direct current|direct]]. The electrical power generation market, which provides useful power for residential, commercial, and industrial use, is commonly divided into three segments: generation, transmission, and distribution. Electrical power can be generated in large scale [[power plant]]s or on a smaller scale for distributed power applications.

==Resources==
Grob, Bertand ''Basic Electronics'' Fifth edition, 1984

[[Category:Physics]]
[[Category:Electricity]]

Neutrino

2016-09-07T15:08:03Z

Harryk: Bit more detail

The '''neutrino''' is "an [[Subatomic particle|elementary particle]] which holds no [[Electricity|electrical]] charge, travels at nearly the [[speed of light]], and passes through ordinary matter with virtually no interaction."<ref>[http://physics.about.com/od/glossary/g/neutrino.htm About.com Physics: Neutrino]</ref> Since it has no electrical charge, nor color charge, it only interacts via the [[weak force]] or [[gravity]].

==References==
<references/>

[[Category:Physics]]

Lepton

2016-09-07T15:04:47Z

Harryk: Corrected some details and added some

A '''lepton''' is a [[fermion]], meaning that it is an elementary particle with half-integer spin. Leptons consist of several types of electron-like particles and [[neutrino|neutrinos]]. There are three known electron-like particles; the [[electron]], [[muon]] and the tau. The neutrinos include the electron-neutrino, the muon-neutrino and the tau-neutrino. Along with [[quark]]s, leptons form the [[fundamental particles]] of [[matter]].

[[Category:Quantum Mechanics]]

Nuclear fusion

2016-09-07T14:38:59Z

Harryk: Formatting

'''Nuclear fusion''' is the process by which two or more nuclei fuse to make a larger nucleus.<ref>Wile, Dr. Jay L. ''Exploring Creation With Physical Science''. Apologia Educational Ministries, Inc. 1999, 2000</ref> The successful fusion of two light (lighter than iron) nuclei releases large amounts of [[energy]], but to start the reactions large amounts of energy must be input to overcome the repulsive electrostatic forces. The energy is released from the mass in accordance with [[e=mc^2|E=mc2]]. To conserve energy, the mass of the products is less than the reactants.

In the center of most stars, hydrogen fuses together to form helium. Fusion in stars releases so much heat that the process alone keeps their mass from collapsing in on itself due to [[gravity]]. It is the reason that stars are so stable as well. If the core of a star starts to collapse, more fusion reactions occur and it expands again from the heat. If the core expands too far, less fusion reactions occur and it collapses back down. This can repeat until iron 56 is reached, at which point it becomes energetically unfavorable to continue. It requires [[energy]] to advance further rather than energy being released.

Scientists here on earth are trying to make nuclear fusion in the laboratory a useful energy source. One example is the European Toroidal Reactor near Cambridge in England. If successful fusion would supply a vast amount of clean energy, as the fuel would be derived from seawater and the by-product would be helium. Uncontrolled fusion causes thermonuclear explosions, which are used in the [[hydrogen bomb]].

==See also ==
[[Nuclear fission]]

==References==
<references/>
*[http://apod.nasa.gov/apod/lib/glossary.html#fusion APOD Glossary]

[[Category:Physics]]