System 13

Last night I was pondering about what the ‘end’ of the universe would look like. By ‘end’, I don’t mean the destruction or disappearance of the universe; I mean instead, what the endpoint of it would look like. If you got in an extremely fast spacecraft and went in a straight line, what would you hit eventually? Anything?

This morning I looked into my question briefly. All I’ve done thus far is take a look at the Wikipedia page on the universe. However, just from a cursory read over it, the answer I’ve got thus far, in one sentence is: It’s complicated. The first bit that makes it complicated is this:

There is disagreement over whether the universe is indeed finite or infinite in spatial extent.

Obviously if the universe is spatially infinite, it would be physically impossible to reach an ‘endpoint’, because no endpoint exists. The next bit that could cause problems is that the fact that the universe is expanding:

The most important result of physical cosmology, the understanding that the universe is expanding, is derived from redshift observations and quantified by Hubble’s Law.

So, if the universe is finite, but is expanding constantly, you’d have to have some way of traveling that’s faster than the rate of expansion that the universe is experiencing. But, if the universe is finite and you could find a way of traveling that fast, again, what would you hit at the endpoint, if there’s an endpoint?

The complexity doesn’t end there, though:

Secondly, whether the universe is multiply connected, is unknown. The universe has no spatial boundary according to the standard Big Bang model, but nevertheless may be spatially finite ( compact). This can be understood using a two-dimensional analogy: the surface of a sphere has no edge, but nonetheless has a finite area. It is a two-dimensional surface with constant curvature in a third dimension. The 3-sphere is a three-dimensional equivalent in which all three dimensions are constantly curved in a fourth.

If the universe is indeed spatially finite, as described, then traveling in a “straight” line, in any given direction, would theoretically cause one to eventually arrive back at the starting point.

So, even if the universe is finite in size, and you could get a really, really fast ship… you may still never reach the end, but instead, basically go in a big circle over and over.

Me head hurts, aye…

By the way, before posting this, LearningNerd responded to my first post about this, recommending I check out The Hitchhiker’s Guide to the Galaxy. After reading the little blurb on amazon, I’m wondering whether it will truly answer my questions, but it sounds like a great read regardless.