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Topic: Dark matter found (Read 9476 times)
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ronstew
Zebranky food
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Posts: 1
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I may be a high school physics teacher, but I am no physicist. That said:
A common misconception is that anti-particles are the same as regular particles, but they have opposite charge. But we know there are anti-neutrons, so that doesn't work. A better description is anti-particles are the same as regular particles, but experience time in the other direction. I cannot defend this statement except to say that I got it from a real physicist who makes a living looking for neutrinos and teaching particle physics at a good university.
My last year at that school left me seriously questioning ideas of truth and knowledge - Schroedinger's cat, and all that jazz leave me completely weirded out.
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Death 999
Global Moderator
Enlightened
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Posts: 3874
We did. You did. Yes we can. No.
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I may be a high school physics teacher, but I am no physicist. That said:
A common misconception is that anti-particles are the same as regular particles, but they have opposite charge.
They aren't exactly the same, but they're awfully similar. Another difference beside the one mentioned by meep-eep is that... well, let me back up a little. Neutrinos are peculiar particles in that they only come in one 'handedness', that is, they spin only one way in respect to their direction of motion. Anti-neutrinos have this backward as well.
Also, there are some more subtle asymmetries which are harder to describe, buried in the way that antiparticles mix quark flavors.
A better description is anti-particles are the same as regular particles, but experience time in the other direction.
This is a kind-of-okay description under certain circumstances, like if you're only interested in a momentary look at the mathematics of their interactions. However, once you get into a large enough system that entropy makes sense, it really screws around with the concept of time. Most physicists I know, including myself and also including my quantum field theory professor, think this description is pretty awful. He stressed that the field equations maintain causality, he showed how they do. We had to show how a different set of field equations maintained causality as part a homework assignment.
Now, the time-reversal symmetry, as an abstract tool, is an extremely useful description; but that does not mean that the particles actually are time-reversed.
My last year at that school left me seriously questioning ideas of truth and knowledge - Schroedinger's cat, and all that jazz leave me completely weirded out.
It does that more than it needs to because of the weird interpretations that people have come up with. To a great extent, these interpretations are optional.
Schroedinger's cat is one of them, kind-of. The state of the universe contains some live cat and some dead cat, whether or not we look. But when we look, the parts of us that go with the live or dead cat are no longer similar.
The cat is not saved or killed by our looking at it.
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