- #1
Charlie313
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Layman question(s), but I hope not too stoopid -- many thanks to anyone with the patience to read and attempt even part of an answer, or share a possibly relevant link! I've got time today to follow and read links...
1) Saw a recent 'popular' article discussing that darn Cat as if still a 'paradox' -- Whaaaa? What about "Decoherence => Cat solved: bam!"?
2) Here at the Forums, I quickly saw that the Cat is (almost always, at least) either alive or dead -- as I thought I remembered. However, I still have a question or 2 that I have not found answered in threads on decoherence, or perhaps answered at a proficiency level above my head (https://www.physicsforums.com/threa...ork-does-it-require-the-second-law-of.474411/ -- "Any proof of the H-theorem contains an assumption that breaks T-symmetry by hand." I just about half-get that ...).
3) Question: quantum-level processes are reversible, '2nd law' or thermodynamic processes (statistically) not so -- are asymmetrical in their evolutions ( btw, the Feynman lectures on this -- still interesting e.g.
or
).
SO what is the current speculation or evidence + reasoning about how (and why) reversible (time-symmetrical) quantum processes *decohere* to 'non-reversible' (time-asymmetrical) thermodynamic processes? And am I just ignorantly leaving something out, or is this still a *mystery*?
4) Sub-Question 1: Lots of 'macro' systems have been superposed, like that beryllium atom -- but has anyone superposed distinct states of a non-reversible (e.g. thermodynamic) system? I was assuming that this *can't* be done ... kind of by definition .. and could we by any reasoning possibly detect (say) a cat both alive and dead, if only very briefly?
5) Sub-Question 2: Is there (whether possibly or 'yep, someone has observed it') a 'level' where both quantum (stuff is reversible) and thermodynamic (not so reversible) constraints are in play -- so that, as someone suggested somewhere, the cat might be alive+dead but only in very (1/10^10^10...almost forever) rare instances; for some reason I visualize this as like a foam or something, with the different 'levels' interacting but not really blended...in time => this might be like an oscillation ... but how would something that has decohered then 'recohere' (revert to time-symmetrical or whatever -- I may have a fundamental misconception in here somewhere, or not)? And could that happen without energy-input/entropy-increase (perhaps in the globally considered thermodynamic system of scientist-experiment-grant proposals)? And what constraints of scale (RNA but not ribosomes, maybe) or other constraints might there be on such a *foam* or *oscillation* or whatever -- and why?
MY CONSTRAINTS: not a physicist, so any jargon above basic will probably elude me or need explaining the first time (like, is t-symmetry = time symmetry?); and my once brilliant math aptitudes have atrophied over the past 40 years to only the most basic algebra.
#sorryforznytupos
BONUS: Discussions of 2nd Law seem to tend toward a 'statistical' interpretation -- 'Well, it might reverse itself, but it's just really, really unlikely!' That works if we're thinking of asymmetry and not absolute irreversibility. But for the egg to unsplatter itself would seem to require some input of energy (i.e. not a straightforward 'reversal'), or a suspension of basic laws like gravity .. mmm? My impression is that the 'anything is possible, some things are just super unlikely' explanation, is ok for things like gases in boxes, but for rebonding glass molecules, or reconstructing an egg? It seems really lame, or requiring two diff. universes to interact, or something ... Mmmm? 'Within THIS universe, no splattered egg will ever spontaneously reassemble itself, without a further (entropy-balancing) input of energy into the egg-floor-room system, so that the 2nd Law asymmetry of a system is never violated in specific cases of generally thermodynamically time-asymmetrical processes' or something -- ??
[Moderator's note: discussion of the bonus question has been moved to a new thread:
https://www.physicsforums.com/threads/non-reversibility-of-2nd-law-processes.889970/
Please respond there to that particular question. The title of this thread has also been edited for clarity.]
Thanks, Charlie
1) Saw a recent 'popular' article discussing that darn Cat as if still a 'paradox' -- Whaaaa? What about "Decoherence => Cat solved: bam!"?
2) Here at the Forums, I quickly saw that the Cat is (almost always, at least) either alive or dead -- as I thought I remembered. However, I still have a question or 2 that I have not found answered in threads on decoherence, or perhaps answered at a proficiency level above my head (https://www.physicsforums.com/threa...ork-does-it-require-the-second-law-of.474411/ -- "Any proof of the H-theorem contains an assumption that breaks T-symmetry by hand." I just about half-get that ...).
3) Question: quantum-level processes are reversible, '2nd law' or thermodynamic processes (statistically) not so -- are asymmetrical in their evolutions ( btw, the Feynman lectures on this -- still interesting e.g.
or
).
SO what is the current speculation or evidence + reasoning about how (and why) reversible (time-symmetrical) quantum processes *decohere* to 'non-reversible' (time-asymmetrical) thermodynamic processes? And am I just ignorantly leaving something out, or is this still a *mystery*?
4) Sub-Question 1: Lots of 'macro' systems have been superposed, like that beryllium atom -- but has anyone superposed distinct states of a non-reversible (e.g. thermodynamic) system? I was assuming that this *can't* be done ... kind of by definition .. and could we by any reasoning possibly detect (say) a cat both alive and dead, if only very briefly?
5) Sub-Question 2: Is there (whether possibly or 'yep, someone has observed it') a 'level' where both quantum (stuff is reversible) and thermodynamic (not so reversible) constraints are in play -- so that, as someone suggested somewhere, the cat might be alive+dead but only in very (1/10^10^10...almost forever) rare instances; for some reason I visualize this as like a foam or something, with the different 'levels' interacting but not really blended...in time => this might be like an oscillation ... but how would something that has decohered then 'recohere' (revert to time-symmetrical or whatever -- I may have a fundamental misconception in here somewhere, or not)? And could that happen without energy-input/entropy-increase (perhaps in the globally considered thermodynamic system of scientist-experiment-grant proposals)? And what constraints of scale (RNA but not ribosomes, maybe) or other constraints might there be on such a *foam* or *oscillation* or whatever -- and why?
MY CONSTRAINTS: not a physicist, so any jargon above basic will probably elude me or need explaining the first time (like, is t-symmetry = time symmetry?); and my once brilliant math aptitudes have atrophied over the past 40 years to only the most basic algebra.
#sorryforznytupos
BONUS: Discussions of 2nd Law seem to tend toward a 'statistical' interpretation -- 'Well, it might reverse itself, but it's just really, really unlikely!' That works if we're thinking of asymmetry and not absolute irreversibility. But for the egg to unsplatter itself would seem to require some input of energy (i.e. not a straightforward 'reversal'), or a suspension of basic laws like gravity .. mmm? My impression is that the 'anything is possible, some things are just super unlikely' explanation, is ok for things like gases in boxes, but for rebonding glass molecules, or reconstructing an egg? It seems really lame, or requiring two diff. universes to interact, or something ... Mmmm? 'Within THIS universe, no splattered egg will ever spontaneously reassemble itself, without a further (entropy-balancing) input of energy into the egg-floor-room system, so that the 2nd Law asymmetry of a system is never violated in specific cases of generally thermodynamically time-asymmetrical processes' or something -- ??
[Moderator's note: discussion of the bonus question has been moved to a new thread:
https://www.physicsforums.com/threads/non-reversibility-of-2nd-law-processes.889970/
Please respond there to that particular question. The title of this thread has also been edited for clarity.]
Thanks, Charlie
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