On Mon, 2006-10-02 at 09:34, Brian Beesley wrote: > [Off topic, but seems to merit a reply]
Ditto. > > > Sorry but I don't understand this. In fact the universe is finite in > > > content and time > > > > Are you sure of that? > > In the sense of a mathematical proof, no. But according to the current > generally accepted standard cosmological models (Big Bang, string theory) the > assertion seems to be true. > > In particular: > > We are unable to track any events prior to the Big Bang (or the local Little > Bang, in the colliding brane model). So the time we are able to use up to the > present is indeed finite. Fair comment, but ... > It follows from this that the content of the universe we see is finite, else > it would have collapsed back to a singularity by now, or at any rate before > the inflationary effect of the cosmological constant began to overcome > gravity in the very early, very dense universe. It does not follow at all. There is nothing whatsoever in the Einstein field equations, whether or not they are augmented by inflation or other considerations, which precludes a spatially or temporally infinite universe from beginning in a singularity. And, anyway, if effective time is measured in terms of interactions per unit proper time, it's possible to get more (or less) activity per unit proper time by performing activities more (or less) rapidly. Perhaps I haven't expressed that well, but the basic idea is that light-travel time between interacting elements is lower in a denser and higher temperature universe and so more computation can be performed per unit proper time. > If - despite the cosmological constant - the Universe does collapse in the > future, the time we are able to influence would also seem to be finite. That's reasonable *if* your premise holds. > If the universe continues to expand (at an exponentially rapid rate, thanks > to > the cosmological constant) then as matter decays to naked baryons & tachyons, > black holes evaporate etc. there will come a point when time effectively > stops as there will be essentially no interactions. (The density of > fundamental particles will "soon" become rather less than one per a volume > equal to the current volume of our universe). This will make computing rather > awkward, combined with the maintenance of any organic life able to use the > results of any computation. In the absence of significant quantum fluctuations or colliding neighboring branes, processing rates diminish. This is the flip side to the hotter-denser universe alluded to above. It is far from obvious to me that computation (and, indeed, life) can't be built from positronium atoms which are light years across. It would be a rather leisurely life style by modern standards, admittedly, but hypothetical lifeforms accustomed to a CBR at 10^10 kelvin may have thought the same about us during their attosecond lifetimes. Paul _______________________________________________ Prime mailing list [email protected] http://hogranch.com/mailman/listinfo/prime
