20
edits
Changes
Jump to navigation
Jump to search
Line 1:
Line 1: − + − These particles have been mysterious for quite some time: although [[physicist]]s knew they existed, they knew very little about them. In [[physics]], you can say you "know" something when, among other proprieties, you can predict and describe the way it behaves. You know that a [[stone]] will fall if it's not held properly. [[Physicist]]s can describe how it falls and predict exactly where it will touch the [[ground]] using mathematical formulas. − But physicists couldn't predict anything about the electron! Until a [[Paul Dirac]] thought about it: he found a very simple way to describe the proprieties and behavior of electrons, but... there was something curious about it. His description would only work if the electron had a "[[twin]]" particle, identical to it but with an opposite electric charge. It would be just like its mirror image! − He called it an [[antielectron]] or [[POSITRON]]. Of course, the same would be true for any existing particle ([[proton]] and [[antiproton]], [[neutron]] and [[antineutron]]). − [[Relativity]] teaches that mass is a very concentrated form of [[energy]]. So if energy and matter are the same thing, you can create matter with energy and you can create energy with matter.+ − Of course, to make matter a lot of it is needed, and very much concentrated in space. Particles and antiparticles are always created together, out of energy. − + − Antiparticles created in a laboratory "live" for a very short time before they crash into normal particles and annihilate. But nevertheless, they do exist.+ − Paul Dirac wondered, if protons, electrons and neutrons stick together to make atoms, and atoms stick together to make everything around us, what we call matter, then what about positrons, antiprotons and antineutrons? Do they stick together to make antiatoms? Are antiatoms the building bricks of antimatter? Modern-day physicists agree with him. But thinking something is possible doesn't mean it's necessarily true. + − Scientists are hard at work on this mystery at a place called [[CERN]] they are trying to build antimatter. If some of the originally-created antiparticles are still around, they certainly can't be nearby some people think those antiparticles could be somewhere far, far away in the Universe. Some people think the antiparticles do not exist anymore. Something may have happened, just after their [[creation]], which destroyed them all, leaving only particles for the hard task of building up the Universe. − When a particle meets its antiparticle, they destroy each other, releasing a burst of energy such as gamma rays. In 1978, gamma ray detectors flown on balloons detected a type of gamma ray emerging from space that is known to be emitted when electrons collide with positrons — meaning there was antimatter in space. − These gamma rays apparently came from a cloud of antimatter roughly 10,000 light-years across surrounding our galaxy's core. This giant cloud shines brightly with gamma rays, with about the energy of 10,000 suns.+ − What exactly generated the antimatter was a mystery for the following decades. Suspects have included everything from exploding stars to dark matter.+ − Now, an international research team looking over four years of data from the European Space Agency's International Gamma Ray Astrophysics Laboratory (INTEGRAL) satellite has pinpointed the apparent culprits. Their new findings suggest these positrons originate mainly from stars getting devoured by black holes and neutron stars. − As a black hole or neutron star destroys a star, tremendous amounts of radiation are released. Just as electrons and positrons emit the tell-tale [[gamma rays]] upon annihilation, so too can gamma rays combine to form electrons and positrons, providing the mechanism for the creation of the antimatter cloud, scientists think. − The researchers calculate that a relatively ordinary star getting torn apart by a black hole or neutron star orbiting around it — a so-called "low mass X-ray binary" — could spew on the order of one hundred thousand billion billion billion billion positrons (a 1 followed by 41 zeros) per second. These could account for a great deal of the antimatter that scientists have inferred, reducing or potentially eliminating the need for exotic explanations such as ones involving dark matter.+ + + +
Overhauled the entire article, improved the style and added more info, cut out the wordiness.
[[Matter]], and therefore everything seen, is made out of fundamental particles of nature. These fundamental particles are hadrons and leptons, the hadrons being 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.
[[Matter]], and therefore everything seen, is made out of fundamental particles of nature. These fundamental particles are hadrons and leptons, the hadrons being 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 [[charge]] and quantum spin 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.
== Discovery ==
The first success was the creation of an "electron-positron" pair, twins that only require a relatively small amount of energy-dough to make them. Later came pairs of protons and antiprotons, then pairs of neutrons and antineutrons.
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 realized his version of the schrödinger wave 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 [[CERN]], 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 hydrogen atoms. In 2003 Antihelium was created. 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 the 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, having no overall magnetic charge, are much harder to contain.
[[Category:Physics]]
[[Category:Physics]]