No, we know the room is curved by mass, and that causes gravity. We know that although we can't look from the "outside in the 4th dimension" or something. One of the effects of a curved space is that the angles of a triangle don't add up to 180° (like if you take a triangle from the North pole, to the euqator, to an other point on the quator, 90 degrees of longitude away, and back to the north pole. That's 3*90°=270°>180°.). In that Youtube video that physicist said that this can be measured by observing some stars, and the sum of the angles is 180°, which means space is flat on larger scales. This means, the universe is either infinite, or must have some "end" somewhere and the latter case sounds pretty unlikely.

Why would an end be so unlikely? I think it's more a 50/50 kind of thing actually.

As Stephen Hawking proved the universe pretty much most certainly had a start (his reversed blackhole theory) and has been expanding ever since the Big Bang.

I think infiniteness here is a somewhat semantical thing. Does 'ever expanding' mean 'infinite' also? Or does it have to be 'without boundaries'? What if it has a boundary that's expanding too fast to ever catch up with? I'd say that would qualify as 'infinite' from our perspective as well.

I'm guessing the bottom-line of the question itself whether it's finite or infinite has got more to do with the potential of being a reoccurring event on the largest scale.

I have no idea what Hawking and co. think of that though.

"No, we know the room is curved by mass, and that causes gravity."
Where's the context? (btw the room is curved by mass, energy and pressure, AFAIK)

As we only see the stars as a projection without curve, the sum of angles has to be 180° which does not prove anything.

Btw the accelerating expansion of the universe is something that could (!) be a result of a finite, bend universe.

"Where's the context?"
The context is that the universe could be finite but endless if it was curved, like a "4D-Sphere" (or 5D if time is also curved that way). But if it's flat, it's rather infinite. That's why I started talking about curved space.

If you walk on the triangle I told you about in my last post, you would also "just walk on the projection" and still measure 270°. Same for the universe. Trust me, we can measure that space is curved, or Einstein would have never found that out in the first place.

Expansion has nothing to do with an infinite or finit universe.


@PHeMoX:
"Why would an end be so unlikely? I think it's more a 50/50 kind of thing actually."
That would prompt many questions, like how do things behave near the end. What if you try to go beyond that end? Should there be an undestructable end? That somehow sounds... unlikely. But maybe possible.

"I think infiniteness here is a somewhat semantical thing. Does 'ever expanding' mean 'infinite' also? Or does it have to be 'without boundaries'? What if it has a boundary that's expanding too fast to ever catch up with? I'd say that would qualify as 'infinite' from our perspective as well."
I guess that would be no real infinity, although we couldn't distinguish it. But we can't look further than 14 billion lightyears anyway, if there is some boundary behind it, we would never find out.

"Trust me, we can measure that space is curved, or Einstein would have never found that out in the first place."
Hm ok...

"Expansion has nothing to do with an infinite or finit universe."
I talked about the fact that the expansion of the universe gets faster and faster, this could be caused by a finite universe.

"I talked about the fact that the expansion of the universe gets faster and faster, this could be caused by a finite universe."
But why would a finite universe rather expanse faster than an infinite one? Don't think an infinite universe would tend to contract because of its infinite amount of mass. It's the density that is important, not the total amount of mass.

I'm not a physicist but if the universe has the topological shape of a surface of a sphere or of an ellipsoid (what speaks against this possibility?) and if there happens to be a big bang on one spot and the expansion is fast enough so it does not collapse, the gravitational force should accelerate the expansion "on the other side of the sphere", doesn't it?

lol.
That sounds weird. And I think it wouldn't work. Gravity works by curving space, so it won't work through uh... non-space. And you gravity doesn't "pull space" anyway.

The expansion of the universe has other reasons, I think it has something to do with dark matter or dark energy...

Guys... Fighting on the internet is like running the special olympics: Even if you win, you're still retarded!

I love you, lets make out sometime.