CitationsAdd new citationList by: CiterankMap Link[2] Is quantum mechanics messing with your memory?
Author: Slezak, Michael Cited by: Peter Baldwin 7:39 AM 20 July 2011 GMT Citerank: (1) 113851Assumes same time orientationPhilosopher Huw Price has responded to Maccone's quantum argument by pointing out that it explains one asymmetry by assuming another. It assumes all observers have the same orientation in time. Without this, some observers would remember the past and others the future.13EF597B URL:
| Excerpt / Summary In a paper published last week in Physical Review Letters, he attempts to provide a solution to what has been called the mystery of "the arrow-of-time".
Briefly, the problem is that while our laws of physics are all symmetrical or "time-reversal invariant" – they apply equally well if time runs forwards or backwards – most of the everyday phenomena we observe, like the cooling of hot coffee, are not. They never seem to happen in reverse.
We have a statistical law that describes these everyday phenomena called the Second Law of Thermodynamics. This law tells us that the "entropy" or degree of disorder of a closed system never decreases. Roughly speaking, a process in which entropy increases is one where the system becomes increasingly disordered. Windows break, thereby increasing disorder, but they will not spontaneously unbreak. Gases will disperse but not spontaneously compress.
However, entropy describes what happens with large numbers of particles. We presume that it must arise from what happens with individual particles, but all the laws that govern the behaviour of individual particles are time-reversal invariant. This means that any process they allow in one direction of time, they also allow in the other.
So why will your coffee spontaneously cool down, but not heat up?
Maccone's solution is to suggest that in fact entropy-decreasing events occur all the time – so there is no asymmetry and no associated mystery about the arrow of time.
He argues that quantum mechanics dictates that if anyone does observe an entropy-decreasing event, their memories of the event "will have been erased by necessity".
Maccone doesn't mean that your memories will never form in the first place. "What I'm pointing out is that memories are formed and then are subsequently erased," he tells me.
When you observe any system, according to Maccone, you enter into a "quantum entanglement" with it. That is, you and the system are entangled and cannot properly be described separately.
The entanglement, Maccone says, is between your memory and the system. When you disentangle, "the disentangling operation will erase this entanglement, namely the observer's memory". His paper derives this conclusion mathematically.
While we cannot remember our cups of coffee re-heating, and hence cannot study them, Maccone thinks that entropy-decreasing events like that must happen.
"If transformations that increase the entropy do occur – and we know that they do – by symmetry we should expect also transformations that decrease the entropy – but we cannot see them."
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