Naked Science Forum
Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: Diogo_Afonso_Leitao on 08/12/2016 15:34:57
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Hello! I would like to know if an antiparticle has not only opposite charge, but also opposite spin to regular particles.
Thank you! =)
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particle and antiparticle must have:
- the same mass m
- the same spin state J
- opposite electric charges q and -q.
See: https://en.wikipedia.org/wiki/Antiparticle#Properties
Protons and antiprotons are both spin=1/2 particles (fermions).
- Ignoring antiprotons (which are quite rare in our world), your body has lots of protons in Hydrogen atoms.
- Normally, these proton spins are randomly aligned, but it is possible to align them in an external magnetic field (this is what an MRI scanner does).
- It is possible to measure the state of protons as being "spin up" or "spin down", when measured relative to an external magnetic field.
- So "opposite" spins can occur in normal matter, without needing to invoke antimatter
PS: While checking my answer, I discovered that physicists can't fully account for where the spin of a proton comes from. Surprisingly little (maybe none) comes from the spin of the component quarks. This is called the proton spin crisis (https://en.wikipedia.org/wiki/Proton_spin_crisis), and is one of the major unsolved puzzles in physics (https://en.wikipedia.org/wiki/List_of_unsolved_problems_in_physics).
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I would imagine that as the wiki article suggests at the end that gluons may make up the missing spin. An experiment in a lab traveling at a significant proportion of the speed of light should obtain the same results. Since time dilation applies then spin must be a function of choice of coordinates.