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Edge of the universe

Jacob_Wallace

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I was reading an article about really big numbers and it said that you could fill the entire universe with a googol - 10 billion grains of sand. If you could fill the universe with a number of anything that must mean the universe is finite. So what happens if you took a spaceship and flew the edge of the universe? Do you hit the edge as if it were a wall or something?
 

phantom000

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That, as they say, is the $64000 question that if you can answer will get you a Nobel prize and Tenner at any university in the world no questions asked.

On a more serious note...what is neither matter nor energy? Because if you can answer that then you know what is past the edge of the universe.
 

robjvargas

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Space is curved. They've proven that much. The logical extension would be that the "edge of space" is right where you started from.
 

Ergodic Mage

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blacbird

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I was reading an article about really big numbers and it said that you could fill the entire universe with a googol - 10 billion grains of sand.

A googol is a hell of a lot more than 10 billion.

And the universe we can discern can be no larger than ~14 billion light-years in radius. Because that's its age, as far as we can discern, and . . . that's as big as we can discern. So that volume is indeed calculable.

caw
 

RichardGarfinkle

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Space is curved. They've proven that much. The logical extension would be that the "edge of space" is right where you started from.

Curved doesn't mean closed, nor does it mean bounded.

Spacetime is curved, the curvature varies based on the amount of mass in the area. The higher the mass the greater the curvature. That's the famous rubber sheet model (which is inaccurate but useful).
 

Craig McNeil

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Wouldn't that just be a vacuum, which is what most of space is?

It would have to be a different kind of vacuum otherwise there would be no boundary. The universe can't be infinite as it's expanding from a fixed point at the speed of light. That's my take on it anyway.
 

benbenberi

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The universe is curved, and it contains everything that's part of the universe. THERE IS NO EDGE. Wherever you are, is universe. You keep going and... still in the universe. Go further, as far as you possibly can and, yep, still universe.

Depending on the topography of the curve, you may eventually end up back where you started. Or you may get further and further away forever. But you can NEVER get to the Edge of the Universe because there's no such thing.
 

Jacob_Wallace

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A googol is a hell of a lot more than 10 billion.

I know a googol is more than 10 billion. I meant that the article I read stated you could fill the universe with 10 billion less than a googol particles of sand. Sorry if that was unclear.
 

benbradley

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Before we get into whether the Universe is curved and in what way it might be curved, let's figure out what number the OP is talking about:
I know a googol is more than 10 billion. I meant that the article I read stated you could fill the universe with 10 billion less than a googol particles of sand. Sorry if that was unclear.
Oh, I wondered if that dash meant subtraction, but that interpretation still doesn't look right. A googol is 1 followed by 100 zeros, or this 101 digit number:
10000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000.


Ten billion (at least in the USA) is this 11-digit number:
10000000000.

The difference is this 100 digit number:
9999999999999999999999999999999999999999999999999999999999999999999999999999999999999999990000000000.

This is mathematically different from a googol, but it's so much the same as a googol (it's the same to 1 part in 10^90) that there's no way the difference could be measured.

Perhaps the article meant something like one ten-billionth of a googol. I recall a figure from decades ago (perhaps a George Gamow book) that the known universe has something like 10^88 particles (grains of sand? atoms? subatomic particles? I forget) in it. That would be roughly the same size number (off by only a couple of orders of magnitude).

Or maybe it was that it would take "only" 10^88 particles (again, I don't recall of what particle) to fill the known universe. It's obviously been a while since I read it.
 
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benbradley

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And so on to the OP's question:
...

If you could fill the universe with a number of anything that must mean the universe is finite. So what happens if you took a spaceship and flew the edge of the universe? Do you hit the edge as if it were a wall or something?
Well, as blackbird said, the "known universe" is about 14 billion light-years in radius, because it's been expanding at the speed of light since the Big Bang 14 billion years ago.

If you could "go to the edge" in a reasonable time (meaning within your lifetime - it would involve going billions of times faster than the speed of light) you might see nothing past the edge (because there's nothing to generate light to see), and a bunch of stars and galaxies and stuff (well, the light from the Early Universe, before all those things formed) back the other direction.

As far as anyone knows, space doesn't "stop" at the edge of the universe, but there's nothing there. Actually, if you went "past the edge" you wouldn't see anything, since the light from the Big Bang wouldn't have reached where you are yet.
 

Dryad

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I think the real answer here is that people don't know and all we have are a number of fascinating theories. I've been reading and thinking on this myself as I have a story in mind building on the idea of the expanding and retracting universe.
 

robjvargas

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As far as anyone knows, space doesn't "stop" at the edge of the universe, but there's nothing there. Actually, if you went "past the edge" you wouldn't see anything, since the light from the Big Bang wouldn't have reached where you are yet.

"Do you think that's air you're breathing?"
 

King Neptune

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Then there's something odd someone could do. If the universe is expanding, then there may be a wave crest at or near the limit of expansion.
 

RDArmstrong

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Well the rules that apply in our universe likely apply outside of it too.

If you learn about an atom and the theory we have about it's composition you can probably find a suitable answer. A central nucleus of dense matter an protons keeps electrons swinging around it in an orbit. There is no real defined boundary of an atom but there is an approximation, an orbit. This same orbit exists for moons around planets and planets around solar systems. Patterns upon patterns. I can't imagine it stops at our universe. I think the technology we have is the limitation to viewing beyond, not the universe or whatever it itself is in.
 

Maxx

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Curved doesn't mean closed, nor does it mean bounded.

Spacetime is curved, the curvature varies based on the amount of mass in the area. The higher the mass the greater the curvature. That's the famous rubber sheet model (which is inaccurate but useful).

As I understand it, some observations and the current inflationary model suggest:

1) no measurable overall curvature (ie the "flatness problem")
2) inflation covered an area much larger than the currently observed universe
3) essentially no edge since at the moment of inflation the edge went away at a "speed" far greater than light speed
4) so there could be an edge out there but it is really far away and probably moving away at a speed greater than one can attain