Spacetime Explained

It can be tricky to think about where something is in not only space, but time too. Physicists picture the location of objects in space and time using a concept called spacetime. They generally think about this in regard to physical objects, and that's a good place to get an introduction to the concept. As an example, check out this bowling ball rolling in this gif I found.

The ball is more or less traveling in a straight line down the alley so at any point in time we can describe its position along the single spatial dimension of the length of the alley. We can view the position along that dimension of space at multiple time points by looking at still frames from the movie next to each other.

Now if we were to narrow the slices and take more of them, the path of the ball would become filled in along that single dimension. We can draw this out as a filled in tube in a 2D plane.

This is two dimensions of the spacetime that the bowling ball occupies (one spatial dimension and one time dimension). If you think beyond the timeframe in the video, you can imagine the bowling ball going on to be used over and over again. The full spacetime location of the bowling ball is the path traced out by it through its entire existence.