Aight, here's a deep one. Everyone knows what light is, beams of small particles moving at about 300,000,000 meters per second. Well, we are able so see because light bounces off things we look at and goes into our eyes. For example, when we look in the mirror, the colors of our body bounce off the mirror entirely at this speed and hit our eyes. Well, what if we were moving at the speed of light, riding on a beam of light essentially? The light coming off of our face and going to the mirror would be going the same speed as us, therefore making us invisible. It doesnt seem like much of a question at first, but if you think critically about it, it's interesting. Also, the clothes in our closets for instance. The only reason they're the color they are is because the reflect wavelengths of light a certain way. Well, when the lights are off and the closet door is shut, is your blue shirt still that same blue shirt, or what "color" is it?