Hi Liz,
Great avatar :)
On Sun, Feb 2, 2014 at 10:44 AM, LizR <lizj...@gmail.com> wrote:
> Someone asked how a block universe "comes to exist" and if it comes into
> existence "all at once, or a bit at a time" (or something like that).
>
> I wish I could find the original question, to make sure exactly what it was.
> But I haven't managed to find it, and I can't spend all night trawling the
> forum for it, so I will just put my take on the matter here.
>
> Assuming I've got it right, this seems to me a rather odd question. Asking
> how a block universe comes into existence presupposes that this is a process
> that must happen within a time stream. This would presumably be external to
> the 4D manifold, so it would require a 5D "space-time-time" manifold in
> which to operate. This seems like a crypto-religious viewpoint. The
> assumption is that a universe has to be created, and even created /
> sustained at every moment of its existence - rather as Newton imagined God
> keeping the planets in their orbits (he worked out that they were unstable
> over the long term, I believe). In this view a 4D space-time can't simply
> exist due to some logically prior cause. Yet assuming it has to "come into
> existence" within some external time merely pushes the question back a step
> - the time within which the BU is created can also be viewed as a BU, with
> one more time dimension, so one then has to ask how that BU came into
> existence - and so ad infinitum.
This is a very good point.
> This worked rather nicely in Isaac Asimov's novel "The End of Eternity" (in
> which he posited a multiverse and an external time running across it, so his
> "Eternals" could change history and effectively move across the multiverse
> to a new history in their search for a perfect society). But it seems
> unnecessary from a scientific viewpoint, and of course runs foul of Occam's
> razor.
Couldn't the same be achieved through quantum suicide, even without
and external timeline?
Cheers,
Telmo.
>It's possible, of course, but there is no evidence for it (and I
> can't offhand imagine what such evidence would be). It seems to me more
> sensible to try to explain the existence of space-time by positing something
> simpler, from which space-time emerges. Most current approaches to quantum
> gravity use this approach, I believe.
>
> Otherwise, one is just explaining space-time in a circular manner, by
> requiring the existence of what you're trying to explain - another time
> dimension - and, in fact, an infinite number of them, if one takes this idea
> to its logical conclusion ("It's time-tles all the way down...")
>
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