Can Light Escape the Boundaries of the Universe?

[madphysics]

If light can travel through a vacuum, what's to keep it from traveling out of the "boundaries" of the universe?

If it can, Why doesn't it?

If it can't, what is out their must be something other than a vacuum, or the light can't travel in a vacuum.




Right?

 

[mathman]

According to present theory, the universe has no boundaries.

 

[Astronuc]

We don't really know about the boundaries of the universe, or if there are or are not boundaries, or if the physical laws as we understand them even apply at the boundaries.

 

[Integral]

If light travels there, it is in our universe.

 

[madphysics]

But still, what keeps light from "escaping" our universe? Is it the fact that their is no true vacuum in which we can prove light does travel?

 

[madphysics]

According to present theory, the universe has no boundaries.

Really?

I was under the immpresion that for something to grow in size, it had to have prevu=iuos boundaries to grow past.

 

[mathman]

Really?

I was under the immpresion that for something to grow in size, it had to have prevu=iuos boundaries to grow past.

The usual picture is the two dimensional analog, the surface of a balloon, which can get bigger with no boundary.

 

[madphysics]

Wouldn't that still imply something to grow into?

 

[DaveC426913]

It likely would, yes. One example is a fourth dimension. But that doesn't mean light can travel through it.


The easiest way to think about a finite boundaryless universe is to think of it curving back on itself in 3D, like the balloon does in 2D. If a light beam heads in a straight line long enough, it simply arrives back at its starting point. It has not left our universe, nor has it encountered any sort of boundary.