Conceptual Question of the Day

Classes started today. Also, I think I'm going to try to treat this more like a traditional blog, which means more frequent updates with less thought out content. Sweet. Though I'd like to also throw in some good content when I feel I have the time. For now, however, my semester is lookin' hella busy, and I don't think I have the time to write an end-of-the-week recap of my thoughts on science. Instead, I'm just blundering along and pushing out junk, hoping that something sticks to the inner walls of knowledge.


So, of all the questions I raised to myself today, this is the one I remember as the most interesting: Suppose a ball is coming towards you. You do not know the origin of the ball. Before the ball looks like it's going to hit, how do (or can?) you distinguish between a) a ball coming towards you, and b) a 4 dimensional "sphere" entering the familiar 3 dimensions.