Changes

All of special relativity derives for these two principles, plus assumptions of exact conservation of momentum and energy in all cases.

All of special relativity derives for these two principles, plus assumptions of exact conservation of momentum and energy in all cases.

*At the end of Einstein's original 1905 paper on the subject<ref>http://www.fourmilab.ch/etexts/einstein/E_mc2/www/ "Does the Inertia of a Body Depend its Energy Content?"</ref>, he speculates on the possibility that the equation <math>E = m c^2</math>, which would normally be very hard to verify, could be verified with the extremely high energies of the newly discovered phenomenon of radioactivity.<ref>This equation is not related to [[quantum mechanics]].</ref> In the 1910s, with the invention of the mass spectrometer, it became possible to measure masses of nuclei accurately.  This led to the clearing up of the mystery of atomic masses not being exact integers,and strongly suggested the existence of a "mass defect" (or "packing fraction") consistent with the mass-energy equivalence.  In the 1930s, experiments with known nuclear reactions showed a very accurate correlation between the masses of the nuclei involved and the energy released.  See [[Quantitative Analysis of Alpha Decay]].

There are hundreds of experiments or observations that, to varying extents, "prove", "validate", or "are consistent with" special and general relativity.  A good survey may be found at [http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html this site].  Some experiments can be as simple as a spinning [[Alnico]] magnet<ref>modern magnets are even more powerful and can show the effect more easily.</ref> and a voltmeter, that can be performed on a tabletop in a science classroom.  Just a few of the more important ones will be described here.

*Another prediction of special relativity was time dilation in rapidly moving objects.  This effect was most famously verified in the anomalously slow decay of relativistic cosmic muons.<ref>Some have suggested that other explanations are possible for this effect.  We are trying to track this down.</ref>  Time dilation has since been verified many times, and is routinely taken into account in all high-energy nuclear physics experiments, as in Hadron collision experiments.<ref>Experiments specifically designed to check dilation are rarely conducted any more.</ref>

This is the most famous experiment, and is often taken as the experiment establishing the correctness of special relativity. It is described elsewhere.

Predictions of general relativity turn out to be obscure and difficult to test.  The two most famous predictions were the bending of light in a gravitational field and the precession of the perihelia of orbiting planets.

Predictions of general relativity turn out to be obscure and difficult to test.  The two most famous predictions were the bending of light in a gravitational field and the precession of the perihelia of orbiting planets.

*The first of these was famously tested during a total eclipse in 1919.  That test was somewhat muddled by an incorrect initial calculation, by several people including Einstein himself, of what the effect would be, and some "cherry picking" of the data to be used.<ref>''Einstein's Luck'', John Waller, Oxford University Press, ISBN 0-19-860719-9</ref>  The data selection could be considered "manipulation" or "fudging", by a person (Arthur Eddington) who had a personal stake in the outcome.  His analysis techniques would not pass muster today.  The announcement of this test, flawed though it was, made Einstein world-famous.<ref>[http://einstein.stanford.edu/Library/images/lightsAllAskewBig.jpg The New York Times, Nov. 10, 1919]</ref><ref>[https://www.worldbooklearning.com/how-did-an-eclipse-help-make-albert-einstein-famous/ How did an eclipse help make Albert Einstein famous]</ref><ref>[https://blog.supplysideliberal.com/post/44934715350/how-albert-einstein-became-a-celebrity How Albert Einstein became a celebrity]</ref><ref>[https://www.sciencealert.com/general-relativity-experiment-confirms-accuracy-for-galaxies "The public's mind was blown by the results, effectively turning Albert Einstein into a household name and cementing the concept of general relativity into physics books."]</ref>

The first of these was famously tested during a total eclipse in 1919.  That test was somewhat muddled by an incorrect initial calculation, by several people including Einstein himself, of what the effect would be, and some "cherry picking" of the data to be used.<ref>''Einstein's Luck'', John Waller, Oxford University Press, ISBN 0-19-860719-9</ref>  The data selection could be considered "manipulation" or "fudging", by a person (Arthur Eddington) who had a personal stake in the outcome.  His analysis techniques would not pass muster today.  The announcement of this test, flawed though it was, made Einstein world-famous.<ref>[http://einstein.stanford.edu/Library/images/lightsAllAskewBig.jpg The New York Times, Nov. 10, 1919]</ref><ref>[https://www.worldbooklearning.com/how-did-an-eclipse-help-make-albert-einstein-famous/ How did an eclipse help make Albert Einstein famous]</ref><ref>[https://blog.supplysideliberal.com/post/44934715350/how-albert-einstein-became-a-celebrity How Albert Einstein became a celebrity]</ref><ref>[https://www.sciencealert.com/general-relativity-experiment-confirms-accuracy-for-galaxies "The public's mind was blown by the results, effectively turning Albert Einstein into a household name and cementing the concept of general relativity into physics books."]</ref>

:It should be noted that pre-relativistic (Newtonian) physics may also predict a bending, of half the observed value, depending on whether one uses the 17th century "corpuscular" formulation or the 19th century "wave" formulation.

:It should be noted that pre-relativistic (Newtonian) physics may also predict a bending, of half the observed value, depending on whether one uses the 17th century "corpuscular" formulation or the 19th century "wave" formulation.

:No [[Nobel Prize]] was was awarded for this.  A few years later Einstein won the Nobel Prize for the (unrelated) [[Photoelectric effect]].

:No [[Nobel Prize]] was was awarded for this.  A few years later Einstein won the Nobel Prize for the (unrelated) [[Photoelectric effect]].

*The second "classical" test of general relativity was the advance of the perihelion of the orbit of Mercury.  There are many complex effects contributing to this, including gravitational perturbations from other planets and the effect of the oblateness of the Sun.  These are hard to calculate accurately, but, by 1900 it was known quite accurately that there was an "anomalous" precession, that is, a precession beyond all other known effects, of 43 arc seconds per century.  This is a very tiny effect, but astronomical measurements were sufficiently accurate by that time to show it clearly.

The second "classical" test of general relativity was the advance of the perihelion of the orbit of Mercury.  There are many complex effects contributing to this, including gravitational perturbations from other planets and the effect of the oblateness of the Sun.  These are hard to calculate accurately, but, by 1900 it was known quite accurately that there was an "anomalous" precession, that is, a precession beyond all other known effects, of 43 arc seconds per century.  This is a very tiny effect, but astronomical measurements were sufficiently accurate by that time to show it clearly.

:No Nobel Prize was was awarded for this.

:No Nobel Prize was was awarded for this.

*[[Quantitative Analysis of Alpha Decay]]

*[[Quantitative Analysis of Alpha Decay]]

*[[Gravitational waves]]

*[[Gravitational waves]]

== References ==

== References ==