I heard that the universe has a horizon? The limit were the light has reached or "gone to" but that means...

[Cardiumsea1419]

that the horizon is spherical, right!? I mean, light goes in every direction and where ever we look in deep space with our telescopes we would see that limit? I can't see this as my astronomy Dr. represented the expanding universe as the surface of an expanding balloon? He said the horizon would be like the same like here on Earth but all the galaxies were on the level of balloon?? Do you have any way to help me visualize this, cause how is that??? Thanks!

[BlackOwnage007]

I have no idea.

[lindajune2149]

The "horizon" is the edge of the observable universe - the extent we could see (based on the expansion of the universe in the time since the Big Bang).This horizon, from our perspective, is spherical.Think of it as the outer envelope of an expanding balloon.But the galaxies and other objects in the universe are not on the surface of the balloon - the galaxies are at all different places inside that spherical space. The "expanding balloon" metaphor is actually misleading.A better metaphor is a rising loaf of raisin bread, where the "raisins" are the galaxies scattered throughout the "loaf".

[someoneelse7960]

The Horizon this refers to is imaginary; it's not a real horizon. You couldn't travel to it and see it out in space somewhere. It refers to parts of the Universe that are so far away, light hasn't had time to reach us yet. This would mean anyplace farther than 13.7 billion light years, more or less. We could never see something that's 14 billion light years away. And since the Universe is expanding, that means anything farther away than the horizon will never be seen by us, since the distance between us and that point is moving apart faster than the light can travel (remember, while Einstein forbade any object accelerating to the speed of light, space itself can expand faster than light without causing a paradox). So we will always live in a bubble bounded by how far we can see, even though there may be more (much more) than that. We'll never see it. It's roughly like the horizon on the beach - does the ocean extend farther out than we can see?

[SAN3451]

Lindajune has a good answer, except I think the balloon analogy is more accurate in one respect. The expanding space-time manifold has no edge, any more than the surface of a balloon does. A load of bread does, so a raisin near the edge would see a different universe. All spots on a balloon surface see the same environment, which we believe is true for our universe as well.Regarding the size of the observable universe, we are actually seeing much further than a 13.7 billion ly radius, since the departure site of a photon traveling that long is now much further away due to the expansion of space. Believe its 5-6x larger, so the radius is more like 80 billion ly.

[IrvS5385]

We do have a horizon.You must think in four dimensions here.The universe has a certain age, (since 'transparency',but let's leave that for now).In that time, light has traveled a limited distance.The CBR light we see now has traveled the age of the universe to reach our eyes.We can see no farther. (That range expands at the speed of light as we, and the universe, age.)