Re: Richard Dawkins - the God Delusion - Chapter 1.1 - A Deeply

Eric Potts wrote:

[Peter Ashby:]
No Ken, they said that because time started at the big bang there cannot
have been a before.

[Eric:]
Leaving Ken aside for the moment, I am fascinated by this concept. I
would not pretend to have a lot of understanding of it. But it raises
huge questions.

If I have it right, the idea is that, at a finite point, the universe
existed in a state of infinite density and temperature. (The phrase
is, I admit, borrowed from Wikipedia!) How anything describable as
infinite can exist at a finite point is a paradox, (a singularity).

I don't think anyone claims to know that. Just as plausibly
(so far as my understanding goes), our current understanding
of physics fails to apply in one way or another when densities
and temperatures and suchlike get very very large. (For instance,
it's useful to think of space and time as being "continuous" --
between any two points you can squeeze infinitely many more, etc.
But quite possibly this is wrong, and at *really* small scales
spacetime is discrete, or something of the sort. The continuous
stuff would then come out as an approximation, very accurate in
normal situations but badly wrong when you consider very small
distances or times. Like those relevant at the "Big Bang".)

But if it existed at a finite point, however brief that point, and
then went "Kapow", we presumably have some kind of critical mass; we
have a state that could not possibly exist for more than the very
briefest of moments without going Bang. Do I have that right?

Again, I don't think anyone claims to know, but let's suppose
for the sake of argument that the state of the very early
universe would inevitably produce a Bang.

And if time did not exist at that finite point (another paradox, or
perhaps the same one differently expressed),

No, wait, I think you may be confused. It's not a matter of
time not existing at the start. It's a matter of time not
existing *further back than* the start, because there's no
such thing as further-back-than-the-start. In particular,
if your "finite point" is supposed to be *before* the Big Bang
then I think you have the wrong end of the stick.

The idea is that time might be like "northernness" on the
surface of the earth. You can go south, and further south,
and further south; as you approach the south pole the
corresponding lines of latitude get smaller and smaller,
and eventually you reach the south pole where their
size reaches zero. But there isn't anything further
south than that.

(Well, as it happens, the surface of the earth is just
part of a larger three-dimensional space, and you can
think of "northernness" as a direction in *that* space
and then it's perfectly reasonable to ask what's south
of the south pole; the answer is "atmosphere, and then
empty space". But *on the earth's surface* there's nothing
south of the south pole, and the idea is that the whole
of spacetime might be like the earth's surface. It needn't
be embedded in anything larger that would give meaning
to "before the Big Bang".)

and if that point really
was finite, there must have been a point (I can't say "time") when
that critical mass did not exist. Right?

Wrong (see above). Sorry. :-)

--
Gareth McCaughan
..sig under construc
.

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