Mar 16, 2012

standing airplane

I was on a bus, saw something in the sky. It was not moving, so I felt very strange, after all, you cannot see a star at noon. When I looked closely, it turns out an airplane. Strange thing, because it was not moving but rotating! I suddenly realized that's because I was on a moving bus!

The above graph analyzes the case. And as we can see, we have reference objects, trees and houses,  most probably. The point is, with respect to the static reference objects, the airplane was projected to the same observation point. The reason it looked rotating is the view angle is changing. We know from our daily life, the perpendicular angular speed of view is indeed comparable with that of slowly moving bus. Both take seconds to make a sensible change. That explains why this can happen.

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