I have heard that a positron is like an electron moving backward through time. Can someone elucidate this statement for me. I would like to hear a deeper explanation of what we believe anti-matter to be, why it annihilates with matter and how this relates to relativity.
Answer
I would like to hear a deeper explanation of what we believe anti-matter to be, why it annihilates with matter and how this relates to relativity.
This is the table of elementary particles deduced from innumerable measurements:
Each particle has a characteristic mass and several characteristic quantum numbers.
To each particle there corresponds an antiparticle which means : the antiparticle has the same mass as the particle but opposite in sign quantum numbers. Thus when particle meets antiparticle the quantum numbers become zero and the available energy ( minimum 2*m) can turn into other particles with quantum numbers that in total will add up to zero. Thus e+e- can annihilate to neutrino antineutrino, quark antiquark etc as long as the sum of the quantum numbers is zero.
The relationship to relativity comes from the famous equivalence of mass to energy .
The fanciful expression the positron is an electron moving backwards in time comes from the mathematics of calculating crossections, and particularly with Feynman diagrams. Just mathematics.
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