A=A, If the Universe is everything, then it can have no edge. An edge implies something beyond and that's mystics. In fact the 'Big Bang' idea came from a Catholic priest/astronomer. Mystics.

Yeah, interesting analogy but I'm not sure it applies. For one thing, what would the light be reflecting against?

Interesting analogy although perhaps the light would go around the edge of the sphere and hit you in the back of the head.

I got 18 years then before my memory gets creaky :-)

This is manifold theory, is it not?

Think balloon. If you were inside it and went to the edge of the balloon that is where it stops because it goes no further.
Unless you push and stretch the balloon beyond - then you have extended the boundary.
If space does not exist beyond as far as we can see, does it exist? Not until you go look beyond. If you can't look beyond, then anything would have to be reflected back in.

Yeah, the Kahn TV episode and the movie follow-up are Star Trek favorites of mine.
Haven't seen either again for a long time. My age 68 memory gets creaky sometimes.

The universe keeps getting bigger, which means, relatively speaking, we get smaller. How does this affect Einstein's space/time prognostications? I was just finally beginning to mentally get my brain around it. I'll wrap my head in duct tape so that it'll stay together when it explodes.

I don't see how anything could be "infinite" and
never-ending, including the universe. It is what it
is. But it could be that it is round, (either spherical,
or flat-round), and that at some point, there is the
end, and it starts all over again.

There is supposed to be an experiment going on to answer that question. The answer is best explained with reference to the book flatlanders, which is about two dimensional beings living on a 3D sphere. They cannot see that they live on a sphere, but from geometry they know if they live on a plane then the sum of the angles of a triangle will add up to 180 degrees. If they live on a sphere the angles will be greater than 180 degrees..

Yeah, when counting you can't have an infinite number of things - even digits. 1 = .999... is true, but I think the best way to look at is that there is no number that you can name between .999... and 1 and that is why they are equal. They are the same number, represented in different ways.

Would it have to be one of those two things? Why would you see your reflection if you were at the edge? Would photons necessarily have to "bounce" back?

I happen to agree with you but Rand and Aristotle disagreed. They said infinite is never something it is a potential. My counter would be counter would be that if you express 1/3 as a decimal then it is infinite and then if you add 3 of these infinite series you have 1 is equal to .9999bar.

I do not have the background to say more than I like to observe an increase in factual knowledge about the universe and its origins, but I also note that the 'best fit' model for those observations changes quite frequently.

Like Robert Fl, I wonder how one would distinguish between a flat universe and an immense one with a curvature that is beyond our current ability to measure.

Jan

You can go back and edit the title now. It's a producer perk that's fairly recent.

If space is flat, is it still also curved?
What if it is curved (sphere) but we perceive it as flat? How can we trust our observations?

Of course it's infinite. If you could go to the edge of the universe and look out, what would you see?
You'd either see something beyond (so, you weren't at the edge) or, you'd see yourself looking back in.

That was Kahn. I'm pretty it was the Wrath of Kahn.
Now I feel old - thanks.

Hey K!
(Good article - love this stuff! - should have said that. Oh and whatever I "did there" was probably an accident.)

I wrote about the whole infinity thing a little while back so I won't go into at length here.
But the short answer is that I think that concepts of "infinity" are fine - as concepts - but are problematic when applied to the physical world.

I think "infinity" says more about the limits of our understanding than the "limits" of the physical world.

Here's the link if you're interested.
http://www.galtsgulchonline.com/posts...

It wasn't particularly well received but - oh well. Not my problem! Ha!
(So embarrassing - I couldn't figure out how to fix the typo in the title. The TITLE for christ sake! That's probably why they didn't like it. Yeah - that's the ticket! Ha!)

Big G is extremely difficult to measure and the variations over time fall within the statistical error bar. However, there is a theory that G may be related to cosmological space-time curvature. If this is the case G may have been different in the distant past but would not be expected to change over recent time frames.

We "know" the masses of planets by timing the orbits of their moons. But that equation really has two unknowns (the mass of the planet and G), so it can be regarded as "measuring" either one of these values only if the other value were known. What this really means is that we know approximations of both, but are guessing about the exact values since we can't exactly put the planet on a scale and weigh it.

If G (and thus the gravitational pull of each object) were decreasing, the fact could in principle be observed, because all planets and moons would shift into slightly larger orbits. But the assertions I've seen that this is happening posit a very slow increase, taking at least millions of years to be significant.

These theories change every few decades, and I expect them to change many more times before we get enough probes outside the solar system to learn anything useful. We're still almost totally guessing, even though the pros don't want to admit it.

How could it be an accurate map of something if the something being mapped is infinite? :)

I first heard of "three dimensional thinking" by watching a Star Trek episode as a college kid.
Capt. Kirk beat someone in another starship who was thinking "two dimensionally."

why? (yes, I see what you did there)