nichomachus
Tue, 22 Apr 2008 12:45:07 -0700
On Apr 20, 6:10 pm, Russell Standish <[EMAIL PROTECTED]> wrote: > On Sun, Apr 20, 2008 at 01:20:21PM -0700, Tom Caylor wrote: > > > Except that the evidence seems to support that our past is also > > recorded in a reality "out there" that seems independent of our > > brains. For example when we are reminded of something from our past, > > from looking at old photos, or from someone from our past telling a > > story about us, which as far as we can tell we would have never > > remembered without that reminder from outside of our possible streams > > of consciousness without the reminder. > > You have to distinguish between "being reminded of something" - here > an external event triggers our brain to recall a memory that is really > there, and "finding out about our past" by performing a > measurement. The latter entails completely new knowledge. It is no > different in principle to finding out about the present by performing > a normal measurement. > > I would argue that this implies our past (that which is beyond our > memories) is a superposition of those histories prior to any > measurement that might distinguish them, just as it might be in an > experimental apparatus measure circular polarisation. > > The independent "out there" feeling is just the self consistency of > all our observations - one that is nevertheless quite remarkable, but > not entailing the existence of something that is out there. I find this to be a fascinating idea, to relate mutiple possible histories to quantum superpositions. How does this notion relate to the idea that mutiple possible histories may degenerate to single "now"? Information about the past states of the universe being lost is equivalent to a gain in entropy, such that the state of the universe at time = t may not uniquely identify the state of the universe at time < t. Superficially this appears to be symmetrical with the notion of many possible worlds at time > t springing from a single state at t, another example of time invariance. However, it would be impossible, even in principle, to determine which one of these possible histories is the real one, since it would be meaningless to claim that only one led to the current state. If more than one history degenerate in to a particular state, then they are all correct in this scenario since irreversible steps make recovering one unique history impossible. But the meaning of the notion that the outcome an experiment performed in the past exists in a superposition of outcomes until the moment of an observation probably does depend greatly on whether one considers the existence of the world to be observer-dependent or independent. Is the ensemble merely the set of all possible observer experiences? Or are there ensembles that are at least as valid that take reality to be external and observer independent? I intuitively suspect that there is nothing special about what we call consciousness, and that an observation is any physical measurement, be it a photon impinging on a retina or a photodetector or whatever. It does not seem as sensical to me to claim that a measurement made with instruments does not constitute an observation until looked at by a conscious observer. However, I am trying to understand the differences in these two views -- not the easiest task to do since I am invested in one of them already. I hate to tax the patience of those who read this list with yet another thought experiment, but I think it may be useful to illustrate this with an example. Suppose that there is a distant galaxy that has never been observed from Earth, but only because no one has yet looked it with a sufficiently powered telescope. When we do decide to point the Hubble at it, we either will or will not observe the aftermath of a particularly dramatic supernova whose light would have been visible from earth centuries ago, assuming that it in fact happened, and someone had looked at it. If I look at it with the Hubble tomorrow and I see the results of a powerful supernova, I can safely assume that the version of me observing it exists within the same reality as one that experienced that supernova. If I do not see the results of the supernova (which would have been evident if it had taken place) then that means that the 'I' who sees the galaxy exists in a branch that did not experience that supernova. The superposition would be resolved into actualities by my observation. Here is the problem: the light from that supernova would have first reached earth centuries before I made that observation. Hence, I would not be the first earthbound entity to observe that event. Perhaps the first conscious entity, but inanimate objects on the Earth also "saw" the light from that supernova. It would seem that in this case the superpostion was not one of genuine quantum superposition but only uncertainty about history from our own ignorance. Suppose that I do see that a supernova occurred, but unbeknownst to me, an ancient astronomer had already observed the supernova. Would my observation that a supernova had occurred still constitute a resolution of a superposition? or would I simply learn something of which I had previously been ignorant? It seems that questions such as what consitutes an observer and the role of consiousness in observation go directly to the heart of the meaning of quantum mechanics and how it may be understood/interpreted. In order to make the schrodinger cat experiment work, an unphysical object had to be invented, the isolation box in which the cat was placed. It has been claimed that in fact such a macroscopic level superposition would be impossible to realize in actuality since it is impossible to avoid "observations" in the form of the environmental interactions causing the system to decohere. Of course, preserving such superpositions in QM systems is a problem that is very technologically relevant as it is one that must be solved in order to develop quantum computers. --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Everything List" group. To post to this group, send email to [EMAIL PROTECTED] To unsubscribe from this group, send email to [EMAIL PROTECTED] For more options, visit this group at http://groups.google.com/group/everything-list?hl=en -~----------~----~----~----~------~----~------~--~---