Some scientists now believe that there are anti-matter galaxies
out there, containing anti-matter stars illuminating anti-matter
planets that are perhaps populated with anti-matter beings.
However astronomers using gamma-rays detectors flown on orbiting
astronomical satellites have looked carefully for any indication
of anti-matter universe ...but found nothing!
[ What is anti-matter? ]
Each atom comprises a heavy central nucleus
surrounded by one or more orbiting lightweight elementary
particles called electrons. The nucleus in turn is made up
of heavy elementary particles called protons and neutrons.
The electron has a negative electric charge while the proton
is positively charged. The neutron has no electric charge.
However the proton, as it turns out, weighs 1 800 times as
much as the electron.
So physicists started to pose the question:
If experiments have shown that the charges, though opposite,
are exactly equal in magnitude, why should the masses not
be the same as well? British physicist Paul Dirac came up
in 1929 with a bizarre explanation. He combined the theories
of quantum mechanics and electromagnetism and predicted that
there should be mirror-images twins (identical in mass but
opposite in charge) of the proton and the electron which Dirac
called the antiproton and antielectron. Dirac's theory also
predicted that if a particle and its antiparticle came together,
they would annihilate each other; their electric charge would
cancel and their masses would be converted completely to energy.
But if particles and anti-particles must exist in pairs, where
have all the anti-particles gone?
It maybe that in the first instance of the
big-bang that gave birth to te universe (some 15 to 20 billion
years ago), some subtle interaction among particles gave rise
to an asymetry of matter and antimatter - more matter than
antimatter. Scientists hope that once the properties of particles
and atoms of anti-matter can be compared in detail with those
of normal matter, such speculation can be confirmed or disapproved.
This puzzle of the missing anti-matter is one of the major
unsolved problems in physics.
