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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