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Question
If there is anti-matter, couldn't there be anti-energy?
Asked by: Renji Thomas
Answer
When people speak of anti-matter, it's important to recognize that anti-matter isn't some
sort of 'negative' matter. An anti-particle is just as real as any other particle. If you
use Einstein's famous E=mc2 relation you find that an anti-particle has positive energy,
since it has a mass which is identical to the mass of its partner 'particle.' The 'anti-'
part of the name just signifies the fact that the quantum numbers that the particle
has are opposite of those of the corresponding particle. Most people have heard that
anti-matter annihilates with matter and gives rise to energy. This is a result of the two
particles having exactly opposite quantum numbers -- but 'particles' in our everyday world
annihilate into new particles all the time too.
Energy, by contrast, is a relative concept. The important physical quantity is the
difference in energy between any two states of a system. We thus always speak of positive
energy values and typically eliminate solutions which give rise to negative energies as
unphysical. In short, then, the existence of anti-matter does not imply the existence of
some sort of anti-energy.
Answered by: Brent Nelson, M.A. Physics, Ph.D. Student, UC Berkeley
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