Physics Help
Antimatter
Antimatter
Antimatter is
matter that is composed of the
antiparticles of those that constitute normal matter. An atom of
anti-hydrogen, for instance, is composed of a negatively-charged
antiproton being orbited by a positively-charged
positron. If a particle/antiparticle pair comes in contact with each other,
the two
annihilate in a burst of
electromagnetic radiation.
With antimatter, the entire possible
energy of the matter could be harnessed, instead of the very small chemical
energies or nuclear energies that can be extracted today. The reaction of 1
kg of antimatter with 1 kg of matter would produce 1.8×1017
J
of energy (by the equation E=mc2). In contrast,
burning a kilogram of
petrol produces 4.2×107 J, and
nuclear fusion of a kilogram of hydrogen would produce 2.6×1015
J.
Since the energy density is vastly higher than these other
forms, the thrust to weight equation used in
antimatter rocketry and
spacecraft would be very different. In fact, the energy in a few grams of
antimatter is enough to transport a small ship to the
moon.
It is hoped that antimatter could be used as
fuel
for
interplanetary travel or possibly
interstellar travel, but it is also feared that if humanity ever gets the
capabilities to do so, there could be the construction of antimatter
weapons.
Scientists succeeded in
1995
to produce anti-atoms of hydrogen, and also anti-deuteron nuclei, made out of an
anti-proton plus an anti-neutron, but not yet more complex antimatter. Also,
they exist for a very short time, they can not be stored. As far as we know
there are no antimatter atoms in existence in this universe outside of our
particle physics labs. This is a great mystery since one would expect matter and
antimatter to have been generated in equal amounts after the
Big Bang. The scarcity of antimatter has given us a stable universe,
however, without which life could not have evolved.
The scarcity of antimatter means that it is not readily
available to be used as fuel. Generating a single atom of antimatter is
immensely difficult and requires particle accelerators and vast amounts of
energy - millions of times more than is released after it is annihilated with
ordinary matter, due to inefficiencies in the process. No more than a handful of
antimatter atoms have ever been made. Therefore, unless substantial quantities
from some as-yet unimagined natural source of antimatter are found, or ways to
generate antimatter more efficiently are determined, antimatter will remain a
curiosity rather than a viable propulsion system.
The symbol used to denote an antiparticle is the same symbol
used to denote its normal matter counterpart, but with an overstrike. For
example, a proton is denoted with a "p", and an antiproton is denoted by a "p"
with a line over its top ( ).
Home | Up | Antimatter | Elementary Particles | Bosons | Fermions
Physics Help, made by MultiMedia | Free content and software
This guide is licensed under the GNU
Free Documentation License. It uses material from the Wikipedia. | 
