How can a camera tell if an object is in motion?

Ok if you have a stationary camera the camera would obviously just take lots of pictures, see if there were differences in the pictures, and then know motion occured. But, if a camera was in motion, maybe on a car, is it possible for it to tell if other objects are in motion??How can a camera tell if an object is in motion?A "camera" - really a complex electronics device - absolutely can tell. There are radar devices that can measure the speed of another car accurately even if the car it is in is moving - at any speed. It can detect the area around the other car, and compare the speeds of both, and based on some fairly complex mathematics, it can 'decide' which is the stationary field, and which is the moving object.