Universe, boudaries, infinity?

Question

Lets say there is a civilization on the farthest star we can see. What would these aliens see if they looked in the opposite direction of Earth? Would there be more stars? What about a civilization at the edge of these aliens sight. When would it end? If there is no boundary to the universe than there has to be more stars no matter how far you go but if it goes on for infinity than the universe is infinite unless at some point you return to Earth.

Answer 1

let me start by saying i guess alot, i know you could probably figure that out, but i'm tired of being called stupid, made fun of ,...,

what if the universe is the shape of crystal. i think i read that is the most ordered shape. seems it would demand alot of order for it to be as it is.

Answer 2

Wow, that's a few questions there.

1.  Aliens would see their own night sky, with none of our constellations, but they might be able to see our star, the sun.  If they have a huge red sun, we can see it, but our smaller yellow sun might not be visible.

2.  Maybe, it depends on their night skies.

3.  On the edge, they would see blackness.  The universe only extends a certain distance.  After that, it is void.

4.  If there is no boundary, there will be a limited number of stars anyway, since there is a limited amount of matter.

Answer 3

"someone else" is correct.  The aliens see pretty much the same distribution of galaxies that we see.  They would compute the same value for the Hubble constant.  There is no boundary -- everybody sees the same universe, and everybody sees themselves as being at the center.   This goes on for *at least* 156 billion light years before you get back to the general region of our galaxy.

Answer 4

Infinity is one of the hardest things to wrap your head around. Yes, if you went out to the furthsest possible point you could see and then stood there and looked opposite direction, you could go to that point and there would be more, and more, and more - never ending. This is the hard part, because we with our limited brains believe everything is contained, has defined edges. But space doesn't.

Answer 5

The current thinking is the Unverse is 'finite, but unbounded'. Like the surface of the Earth, which is a 2D sphere. You can go left/right or back/forth (or any combination) to go in any direction on the sphere. You never encounter an edge, but can eventually come back to the point you started from, even if you go in a straight line.

The Universe is like this, but in 3D. So you can go left/right, back/forth, and up/down (and again, any combination of these). So eventually you would come back to where you started, even if you go in a straight line (altho you would have to go faster than light, because of the expansion of the Universe. Otherwise it expands faster than you could travel back to your starting point). It sounds odd, but while it's not a shape we normally encounter in daily life, it's the best explanation for the facts as we currently know them.

This is why there is no 'center' or 'edge' to the Universe. Every point is potentially the center, so there is no 'edge'.

Additional Details Edit: No, we can't see individual stars that far away. And galaxies any farther than 13.7 billion light years are so far away, their light can't reach us because the expansion of the Universe means it would take longer for that light to reach us than has already elapsed since the Big Bang. This is known as 'The Horizon Problem'. So any galaxies at this distance would never be seen by us; certainly not from the opposite direction, as you suggest. Also, since we look back in time as we look out, we see a time before there were any sources of light in the sky (13.7 billion years ago). This is why the sky is dark in the first place.

Answer 6

I also agree, Someone Else is correct.

Think like this: You are now watching my words on your monitor. Most probably there is a wall behind your monitor. You see both and you think there is a simultaneity in you vision.

Wrong! You see the wall a tiny little bit later than your monitor because it took light slightly longer to reach you eyes. Okay, for all practical purpose you can say that you see them simultaneously. But when you see the sun as it was 8 minutes ago, a star as it was hundred of years ago and behind it, a galaxy as it was billion of years ago the time is an important factor!

When you see the sky, you see both in space and time. it is unavoidable. The farther you see, the longer in time you see.

And since there is no absolute reference point in the universe ... we all see it as if we were at its center! We, and the aliens 'at the edge' of the universe.

The common metaphore is that you are a fish swimming in the ocean of a planet without continents. You are always in the middle of it and you can swim for all your life, you will never come to the end of it.

Finite but unbounded, yes Sir!

(EDITED) and so is Zi_xin! ... now, if we all agree, where is the fun! :-)

Answer 7

The Universe is finite but unbounded.  What this means is that there is no edge to the Universe.  If you shoot a rocket off from Earth and that rocket goes in a straignt line eventually it would end up where it started.  Samething with star light.  So the civilization on the farthest star we can see will see the same star light that we are seeing except from the oposite direction.  You misconception stems treating the Universe as a 2 dimensional plane whoses endges extends into infinity.  True infinity does not exist in nature.  Everything is finite.  Matter is finite.  Energy is finite.  The Universe is finite.