Curvature of Space (was Re: Some simple cosmology questions)

Hey, I'd like some more info and/or more good web-site references to
mark. I'm looking for an explanation of why space is flat and how we
know it isn't curved positively like a hypersphere or negatively like
a saddle. The fellow below I've been discussing this with makes the
following arguments (off the top of his head, without evidence) why he
thinks space is spherical. What's wrong with the arguments, and in
simple layman's terms, can you explain to me what cosmologists say
today and why? Is there pretty much agreement or not?

Thanks,
Tom


Keynes replies:
<<If space were flat, it would have the qualities we
perceive in local (assumed flat) space. Here an
explosion is an expanding sphere. This is the naive'
picture of a flat expanding universe. It must be spherical.

In that case the original light from the big bang (that
hasn't condensed into matter) would be outward bound
at the speed of light (of course) and attenuating by the
square of distance into virtual depopulation. Spherical
space would have a fuzzy surface fading to nothing.
(more on this later.)

In that case the outer bound of all possible photons
could be calculable according to the age of the universe
(if known) and the speed of light (if it were an 'actual
constant').

But the speed of light is Not actually constant, only
apparently constant. In flat space, light could not be
a constant. Michaelson-Morely experiments tried to
determine the effect of motion on the speed of light.

It was believed that wave-like light needed a medium
to carry the waves, since a wave is not a thing but
simply a pattern of some other thing. (Like waves
on water, or sound waves in the air.)

This immaterial something that carried light waves was
called the aether. This aether was assumed to be an
absolute, (although immaterial), an unmoving fact of life
like Newton's idea of space and time.

Light was assumed to be in and of flat space, so it must
act like sound waves and water waves. In that case,
light would appear faster in the direction of earth's orbit,
and slower in the opposite direction. (According to wavelength.)
The experiment's attempt to measure this 'aether wind'
(by wave interferance) was totally confounded to find that
light speed is the same in any direction regardless of relative
motions. Light appears to have a constant speed.

And this really puzzled scientists. (As did black body
radiation that Planck's constant gave Einstein the clue
to quanta. He scored on rebounds. ha.)

Einstein's solution was to mathematically show that
curved space could account for the apparent constant
speed of light. Einstein's theory made predictions, and
experiments have confirmed them.

If light speed appears constant, it can only be so because
space is not flat but curved. (Relatively compressed or
attenuated by local mass or by accelleration.) This
curvature is not apparent to our vision of space. The
apparent constancy of light speed ('C') makes everything
appear flat in any and all cases. But we know that nothing
can actually be flat, or light speed could not seem to be
a constant.

Einstein combined space and time into space-time to
account for the apparent constant speed of light. We now
know that space and time are not the absolute background
of all being, (as Newton and classical physics believed) and
that they could not have preceeded the big bang which is actually
the beginning of space and time in measurable scientific terms.

Everything happens in (apparently measurable) time which
we calculate by 'motions' of matter in space - the sun, the
moon, and the clock. But motions don't happen in space.
They can only happen in time. (In scientific terms.)

Getting back to the spherical flat expanding universe.
What is it expanding into? We can be certain that it
isn't expanding into space or time. Those are simply
the properties of this universe, and they don't exist
outside of it. Some fluff off the question by saying
that there is no outside of the cosmos. They may say
that it is expanding, but not expanding into anything.

In that case, the cosmos must be finite but unbounded.
What sort of a shape meets those requirements?
Certainly not a conceivable flat-space shape because
all such shapes are bounded - they have a surface,
and something on the other side of that surface
to define it. But what is outside of everything?

The cosmos is expanding, but not at the speed of light
as we might expect. Mass has slowed the expansion.
(Since only massless light can travel at C.)

Hubble first discovered the expansion by the red-shift
in spectroscopy. He virtually discovered the universe,
since previously science presumed our milky way galaxy
was all there was to it.

The expansion is curious. All points are receeding from
all other points. The farther we look into space the
greater the expansion appears. In flat space, there
must be a scene of the crime - THE point of the big
bang birth of everything. In flat space there must be
a privileged position, a center of all expansion, and
if there were, we could find it easily. But we can't.
Every point in space appears equally central.

And every point in space is equally bombarded
constantly from all directions by microwave background
radiation. (Which some scientists have called 'fossil light'
from the big bang itself.) If it isn't that fossil light, what is
it?

So while cosmos apparently expands, the outer boundary
of the big bang rains in on all points in a great contraction.

Space appears to curve in on itself.

This concept isn't really so far out. The surface of
the earth is two dimensional. It is finite but unbounded.
If the two dimensional surface of the earth existed only
in two dimensional space, it would have to be either
infinite or bounded (with an edge, a center, and a shape).
But since that two dimensional surface is bent in three
dimensions, it can be finite and unbounded - without
an edge, a center, or a (two dimensional) shape.
It encloses itself.

Every point on the earth's surface is equally central,
and the farthest distance in any straight line (confined
to the two dimensional surface) returns to it's point
of origin and is of the same length. (discounting
mountains and ocean deeps, and the fatter equator.)>>


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