Time in a black hole
I've thought about time a lot. My theory... time is a result of our universe being trapped in an extra dimensional black hole.
I started thinking about this after reading about multiple dimensions referred to in string theory (see "The elegant universe"). I wondered why we don't see these dimensions. String theory suggests that they are very very small circular dimensions. But I wondered why they couldn't be very large. Maybe we don't "see" these dimensions because they are time-like in nature. That is, we move through them in one direction and therefore we do not have a way to measure them... or in fact we measure them as time.
Then I read that when you enter a black hole (assuming you could), you are drawn to the singularity (center). This motion towards the singularity (center) is inevitable. In fact, this motion (dimensional direction) can be thought of as becoming time, since you are always drawn in one direction. Therefore, if you enter a black hole (past the event horizon), we could think of it as entering a 2-dimension universe. Where the normal 3rd dimension (towards the center) is now a one directional time dimension.
Of course, we don't live in a 2-dimensional universe as I described above. But, if the universe does contain more spatial dimensions (as string theory implies), isn't it possible that our entire universe is actually contained within a giant 4 dimensional black hole? In this case (following the thinking above), 3 dimensions would remain available for us to observe, but we would constantly be pulled in the 4th dimension in one direction. This single directional dimension is what we observe as time.
My actual theory is a bit longer then this. It includes explanations for the expanding universe, the speed of light (speed limit), increase in entropy, time-dilation (special/general relativity). It suggests that time really runs backwards, there is no real motion in the universe. It does not explain: our temporal awareness of time and why we have free choice.
...but I'll save myself the embarrassment of going on.