Is space really infinite?

Question

I know that people say that space is infinite, but how can we be sure. If scientists were to look one billion lightyears away and still see nothing but space, they cant really say it is because there can always be something farther than what they can see.

Answer 1

no its not.

people say its infinite, scientists do not. it is logically, mathematically, and scientifically impossible for the universe to be infinite.

Answer 2

The visible Universe isn't the whole thing.  However, there is stuff near the edge of our visible Universe that is not reachable, even in principal.  For example, if we shot a laser at it, the light could never reach it.  That's because by the time the light gets to where the object was, the fabric of the Universe will have expanded, and the object will be even farther away then when the light beam started out.  This is an example of a finite Universe in an unbounded space.  The full Universe need not be infinite for this to happen, just really big.

I suspect we'll know for certain if the Universe is infinite in size eventually.

According to Douglas Adams, it has been thought that if people were to figure out exactly how the Universe works, it would instantly disappear, only to be replaced by a more incomprehensible Universe.  And others say that this has already happened.

Answer 3

It is not believed to be infinite.  And there are actually a couple of things which stand as evidence of that.

The Universe is believed to be finite yet unbounded.  That's analogous to the surface of a sphere.  You can move on it and there is no end.  But it is a certain size and not infinite.  It would seem infinite to a tiny two-dimensional being.  The universe, probably curved in a fourth dimension, looks infinite to us three-dimensional beings.

Answer 4

It is said to be both Infinite and Finite simultaneously.

E.g. A Sphere, traveling its entire distance in a straight line, you will only end up in the same place you started.

Nonetheless, it is still a finite space.

An interesting topic to research isn't an infinite universe, but perhaps, other planes and dimensions of the universe

Answer 5

The correct answer is:  we do not know.

The universe could be finite but unbounded.  For example, it could be "wrapped" onto itself around a higher dimension (or 11, who knows).

Or it could really be infinite and flat.

An infinite universe does solve a lot of problems.  No need to think of an outside.  No need to imagine higher dimensions.  The universe does not need to expand into anything else: it expands into itself.

But we do not know.

All we know is that the universe is at least as big as the portion we can see (called the visible universe):  a radius of 14 billion light-years in "proper distance" -- the distance as we actually see it -- which is equivalent to somewhere around 78 billion light-years in "comoving distance" -- if we could see the universe everywhere at it is now.

The only thing that is not solved with the infinite universe is the question of what came "before" the beginning of the expansion.  Because of that, many scientists are working on ideas that involve our universe being "inside" objects with higher dimensions.  This at least moves the problem of "what was before" to another Universe of which we know even less (and, of course, that one would have to be infinite, otherwise we would ask, again, what is that one inside of?)

I belong to the less popular camp of the flat and infinite universe.

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The surface of a sphere can be seen as a 2-dimension object wrapped around a third dimension.  If creatures could inhabit this 2-D universe, they would only be aware of two dimensions (up and down would be unknown concepts).

If, on the surface of a sphere, you start off in a direction, you can travel in that direction forever (giving the impression of an infinite universe);  of course, if the surface is static (not expanding) you might recognize your starting point every time you pass over it.

A "wrapped" 3-D universe could be the same idea, with the wrapping around a dimension that we cannot imagine (a direction we do not know), leaving us the impression that we can travel forever in any direction.

The key difference would be "flatness".  Going back to our 2-D example:

On a flat surface, the inside angles of a triangle always add up to 180 degrees.  Whatever the size of the triangle.

On a sphere, the sum add up to more than 180 degrees.  The difference is called the "spherical excess" and it changes with the size of the triangle relative to the size of the sphere.

On earth, consider the triangle made up of these three lines:

The prime meridian (0, though Greenwich), the equator and the 90 W meridian (through Memphis).  

For the 2-D creatures, this is a triangle:  each line is straight (when you follow a side, you do no turn left nor right, you go straight).

Yet, this triangle has three 90 degree angles.  Total 270.

In 3-D space, we could do the same test with solid figures like a tetrahedron (a.k.a. a 3-sided pyramid).  However, with the size of the universe, we'd need a very, very big tetrahedron.

Answer 6

Maybe, but it would take TRILLIONS of years to find out, but in about 5 billion years the Earth will be engulfed in the Sun.