What is 'Space' expanding into?

It's been a while since I've used Reddit. I was shocked by the insightful answers and this subreddit's rules (no anecdotes, speculation, memes, jokes, things which I hate about Reddit, etc.)<p>Here's one particularly intriguing reply:<p>[–]xieish 32 points 1 hour ago There isn't any [space outside of the universe], and this comes from a fundamental misunderstanding of an expanding universe. The universe isn't blowing up like a balloon - space itself is getting larger, as everything moves farther and farther away from everything else. The actual distance between points is increasing, not the size of the container.

Same question with much much much better answers/discussions:<p><a href="http://www.reddit.com/r/askscience/comments/eru42/so_if_the_universe_is_constantly_expanding_what/" rel="nofollow">http://www.reddit.com/r/askscience/comments/eru42/so_if_the_...</a>

This exact question would literally keep me up at night when I was a child. Now I just avoid thinking about it.<p>However, this response from the thread apparently sums it up nicely:<p>Just as on a sphere where latitude needs to be taken into account when determining distance between two points because as latitude increases (up to 90) the distance between those points increase, in our universe time needs to be taken into account when measuring the distance between two points because as time increases (or moves forward) the distance between two points also increases? As in, "the universe is expanding" is not saying that a balloon is necessarily expanding, but rather by moving forward in time, the distance between two points simply increases?

I'm afraid none of these explanations work for me. All of these analogies have the same fatal flaw, regardless of what you try to use to describe how distance between points expands you still have a material in a container. With a balloon, the container is the air around it. If you inflate a balloon, sure the two points you've drawn onto the balloon get further apart, but dammit the VOLUME of the balloon is increasing too. If space is like a balloon, what does it's "volume" consist of? When it expands (a balloon), it is displacing something (air), what does space displace as it expands?<p>Now we're right back at the "fundamental misunderstanding of the space expansion theorem" again...<p>So what about if I pose the same question in a different thought experiment.<p>Go back to the origin, the big bang. Everything is in this super condensed super hot state (from wikipedia). Lets say you are this tiny rebellious particle and you decide you've had enough, you're not gonna wait around for this "inflation" event to occur that every one is all excited and talking about. You take off, at an infinite speed away from wherever you currently are.<p><pre><code> PBBU TRP (#) . </code></pre> So, if the Pre-Big Bang Universe is on the left, and the Theoretical Rebellious Particle is on the right, what is TRP in NOW?

To infinity <i>... and beyond!</i><p>Sorry, I couldn't resist. However, this synopsis is consistent with some of the comments in that thread and may be as good a tl;dr as any other.