= 27d567bc2d48d9f40e9ccc20ea370b15)
timtyler comments on Quantum Physics, CERN and Hawking radiation - Less Wrong
You are viewing a comment permalink. View the original post to see all comments and the full post content.
= 783df68a0f980790206b9ea87794c5b6)
Loading…= b715d02e85f7b3b4ae65ca3d3e450868)
Subscribe to RSS Feed
Powered by Reddit
= f037147d6e6c911a85753b9abdedda8d)
You are viewing a comment permalink. View the original post to see all comments and the full post content.
Comments (66)
Well, I don't have a watertight argument for the first point. I think it is more likely than not, but if your intuition is the other way around, I won't argue too much. What I object to is the idea that T-symmetry is wrong. In fact, T-symmetry is pretty plausible, IMO.
From your second point, (from my perspective) you still don't get the logic of the whole idea - and you have exhausted most of my resources on the subject, so I am not sure what more to do with you.
Assuming that charge and parity quanta involve moving parts internally, then they would both reverse automatically if time is reversed - producing what appears to be CPT symmetry as a result. That would be consistent with all known experiments, and physics would then by time symmetric.
You said: "Because the system is not symmetric under CP, it exhibits different behaviour." No, because you have also reversed time, (you just said so yourself) - and if C,P and T are all reversed, then symmetry is restored. So, then there is no measurement you can make that tells you which way time is flowing.
No. Start with a left-handed neutrino. Reverse T under your assumption. It is now a right-handed antineutrino going the other way; reverse space as well to restore the original direction, if you like, although the argument does not depend on this. Because CP is broken, right-handed antineutrinos do not behave exactly as left-handed neutrinos do. Therefore you can tell how many times T has been reversed. You don't get the full symmetry back except by applying CP another time.
Yes.
A parity flip, I presume you mean.
That is indeed true.
Well you only said you reversed it once - and then you flipped P, but not C, leaving things in a bit of a mess - and then you tried to make out the mess was something to do with me.
Reversing T an odd number of times changes everything. Reversing it an even number of times changes nothing. You can't distinguish between reversing T different numbers of times beyond that - under the hypothesis that reversing T automatically reverses C and P.
Ok, leave the parity flip out of it. If this is true:
then you do not have T symmetry. Done.
It makes time run backwards. Those in charge may not think that this is such a null-op.
If you pressed the "rewind" button, you would normally expect to see some changes!
Ok, there's your problem: You don't understand what is meant by 'symmetry'.
At this stage, I don't really see why you are continuing to comment :-(
To convince you that you are wrong about CPT violation and T violation. Why are you posting?
Once more. Start with a left-handed antineutrino. T-reverse under your assumption that this also reverses CP. You now have a right-handed neutrino. Because of CP violation, it does not have the same physical properties that it started with. Therefore, T symmetry is broken. Which part of this argument do you disagree with?
The "Therefore". Reverse the universe, and a left-handed antineutrino turns into a right-handed neutrino travelling in the opposite direction. Everyone agrees about that. Its different properties don't prevent the universe from retracing its steps - rather they are essential for that to happen correctly.
No; wrong. Its different properties will, precisely, cause the universe not to retrace its steps exactly. The rate for X\to e^+ \nue is different from that for e^- \bar\nue \to X; this is what CP violation means. Therefore, when you have reversed time, the antineutrino will not precisely retrace the steps the neutrino took.