What would happen if you fired a gun on a train moving as fast as a bullet?
This is a good question because it involves the concept of reference frames. The quick answer is that relative to you, the bullet will always travel at the same speed. In other reference frames, however, unexpected things can happen! Gun Image Gallery You may have heard of Newton’s first law: “Every body persists in its state of rest or of uniform motion in a straight line unless it is compelled to change that state by forces impressed on it.” We could rephrase this a little and say that a body in motion tends to stay in motion and a body at rest tends to stay at rest unless acted on by an external force. Imagine you are on a perfectly smooth speeding train, moving at a uniform speed (not accelerating or turning), in a
