Re: Anti-matter

Hi!

Yes, antimatter does factually exist. Your "less credible" site is indeed less credible; neurons are nerve cells, and the stuff at the center of a black hole is the same stuff that fell into the black hole, and may include both matter and antimatter.

So, what is antimatter, anyway? As physicists began the serious study of elementary particles earlier in this century, their theories predicted that every particle should have an "antiparticle", with identical mass but opposite electrical charge (and other "quantum numbers" also opposite, such as lepton and baryon number - we won't need to worry about those, though). These particles were soon discovered - the antiparticle of the electron is called the positron, and the antiparticles of the proton and neutron are called the antiproton and antineutron. (The positron is the only antiparticle that has its own name). Particles other than those that make up ordinary matter (electrons, protons, and neutrons) are short-lived, and produced in accelerators and cosmic rays; these other particles are also observed to exist as both particles and antiparticles. (Indeed, in the process of satisfying conservation laws, the particles and their antiparticles are often produced simultaneously). You can find a review of the physics involved (at a reasonably basic level) by going to The ABC's of Nuclear Science and then clicking on "Antimatter".

Three years ago, scientists at CERN, the European high energy physics laboratory, succeded in creating a few atoms of antihydrogen; you can read a press release about it here:
http://pressold.web.cern.ch/PressOld/Releases96/AntiHydrogen/Anti-HydrogenF.html

Now, having said that antimatter exists, and that it has even been produced in the laboratory, I must tell you that it doesn't, as far as we know, exist in large quantities anywhere. Cosmic rays, which come from throughout our galaxy, consist mostly of matter - the antimatter that is found can be explained by the expected rate at which particle-antiparticle pairs are created. When ordinary matter and antimatter meet, they annihilate, producing gamma rays of a characteristic energy. These gamma rays have been searched for and not found; their absence means that not only is there not a substantial amount of antimatter in our own galaxy, but that other galaxies do not seem to be made of antimatter either. Unlike the distances between stars, which are very large compared to the sizes of the stars, the distances between galaxies are not that large compared to the sizes of the galaxies. This means that galaxies often collide or approach each other closely; if one galaxy were matter while the other was antimatter, we would expect to see lots of gamma rays coming from the place where they meet. This has not been seen, leading us to conclude that other galaxies are made of the same stuff as our galaxy - matter. More information on the presence, or absence, of antimatter elsewhere in the universe can be found at:
http://www.earthsky.com/1996/es960904.html
http://bric.postech.ac.kr/science/97now/97_10now/971007a.html

On the other hand :-) - science marches on, and apparent clouds of antimatter have indeed been discovered within our own galaxy - you can read about it at HEASARC

This doesn't alter the statement that our galaxy has a vast preponderance of matter over antimatter, but it does make the whole situation much more interesting! Here is an article about where these clouds of antimatter could have come from in Time magazine

Have fun!