# Re: SPACE EXPANSION(another space question)

J. R. Molloy (jr@shasta.com)
Fri, 8 May 1998 12:04:05 -0700

From: Hal Finney <hal@rain.org>

>One problem with simplistic space
expansion models is that space may be
>infinite.

Yes, it "may be." The task for
extropians comes down to this: grow up
and find out. Space may also exist as a
finite, yet unbounded quality, as
Einstein suggested. Then again, space
may succumb to the manipulative designs
of super-intelligent transhumans. We
might have the capability to know these
things if we expand our cognitive
skills.

>In the simplest models from general
relativity, if the density
>of the universe is so small that it
will expand forever and not contract,
>that also implies that the universe,
although curved, does not "close"
>and so goes on forever.

If it doesn't go on forever, then
something else does. Whatever goes on
forever, I choose to call "the
universe." Accept no substitutes.

>
>You can still have an expanding
universe even if it is spatially
infinite.

"Expanding infinity"... that deserves a
special prize awarded by the drop-outs
of high school math. Just kidding. No
alacrity intended.

>It just means that distant objects move
apart, slowly at first, and then
>faster and faster.

Oh, it means that does it? Gosh, let's

>
>Suppose space were not expanding. It
is three dimensional, obviously
>(ignoring the "time dimension"). Would
you demand that there exist a
>four dimensional space in which the
three dimensional one was embedded,
>in order to give it reality? And would
that four dimensional space have
>to be part of a larger five dimensional
space, which is itself part of
>a six dimensional one, and so on?

Suppose your dreams expand in a
direction opposite to that of reality.
Yes! We've done it! Now, how many
dimensions will you assign to your
snoring?
>
>All this is conceivable, but is it
really necessary?

In your dreams ("suppose space were not
expanding"), it remains not only
necessary, it remains definitive.

>I don't think we need
>to assume there are higher dimensional
spaces in order to give ours
>reality.

Oh? Who died and put you in charge of
assigning realities? The dimensions of
space have their own way of defining
their numbers. They don't require
intervention on the part of carbon-based
gods.

>
>Even though our space is said to be
"curved", and expanding, those
>properties do not require higher
dimensional spaces, either. Curvature
is
>like a gradual internal warping of
space, so that large enough triangles
>don't have angles that add to exactly
180 degrees. It can be fully
>described without reference to any
larger embedding space.

I take back everything I've said. This
clears it all up, and I'll never try to
divulge this information to anyone else,
because it suddenly occurs to me that
all my attempts to convey any idea about
how reality actually works probably
appear to those who really do understand
these matters as silly ego trips into
the arena of spewing personal
viewpoints. Sorry.

>
>Likewise the expansion of space can be
expressed soley in terms of the
>relations between objects within our
universe. There is no need to
>postulate a higher dimensional universe
which ours is part of.
>

"soley"? Do you mean /solely/?

Cheers,

J R