Thread: Expanding universe

I hear that the universe is still expanding but i would like to know what it is expanding into. What is the space that the universe is filling up?

Originally Posted by zendra

I hear that the universe is still expanding but i would like to know what it is expanding into. What is the space that the universe is filling up?

It isn't expanding into anything. The same way you can walk around the earth and end up back where you started, you could fly in a space ship directly away from earth and eventually end up back where you started. What expansion means, is that the distance you'd have to travel to complete the trip increases over time.

but how/why is it expanding? why only the distance and not the locations(planets)?

Originally Posted by zendra

but how/why is it expanding? why only the distance and not the locations(planets)?

Not sure about how, but the solar system, galaxies, clusters and superclusters aren't expanding because they are gravitationally bound to each other. Its like two stones connected by a string mixed into rising dough.

I know it is hard to imagine but the universe is not expanding into anything. Nothing exists outside the universe - no matter and no time or space either. Try and get your noggin around that!

Everything that exists exists in space time. If there is no space time, there is nothing. The universe expands because space time is expanding. If we envisage something 'outside' the universe, we are thinking of something that has no space time. If it has no space time, it does not exist. Therefore, what the universe is 'expanding into' does not exist.

Of course, there are lots of theories about other universes. A series of different multiverse theories. The origin of our own universe, the Big Bang, may have been related to the intersection of two other universes. However, as far as we know, our universe is not expanding into another universe. If it did, booooom!!

Originally Posted by zendra

but how/why is it expanding? why only the distance and not the locations(planets)?

Hubble found that the further a Galaxy is from us, the faster it is moving away, like dots on a ballon, the more you blow it up, the greater the distance between the dots becomes, and the faster the dots separate. The universe may also be flat, this works in a similar way.

I like that analogy about the bread but i still hate not being able to grasp things like there being nothing,its like grasping the size of the suns bigger than ours.

Originally Posted by zendra

I like that analogy about the bread but i still hate not being able to grasp things like there being nothing,its like grasping the size of the suns bigger than ours.

What is written on the 7th side of a standard die? Think of it like that. It is not worth thinking about, because there is nothing to think about.