The World Is An Amazing Place


Continued from: Which One Are You?

If we are in a pool of water and there is a floating (object) very close by, we can move it “directly” by pushing the water with another (object). If you looked only at the two (objects), all you would see would be that one moved immediately in response to the motion of the other—there is some kind of “interaction” between them. Of course, what we really do is to disturb the water; the water then disturbs the other (object).  We could make up a “law” that if you pushed the water a little bit, an object close by in the water would move. If it were farther away, of course, the second (object) would scarcely move, for we move the water locally. On the other hand, if we jiggle the (object) a new phenomenon is involved, in which the motion of the water moves the water there, etc., and waves travel away, so that by jiggling, there is an influence very much farther out, an oscillatory influence, that cannot be understood from the direct interaction. 

Therefore the idea of direct interaction must be replaced with the existence of the water, or in the electrical case, with what we call the electromagnetic field. The electromagnetic field can carry waves; some of these waves are light, others are used in radio broadcasts, but the general name is electromagnetic waves.

credit: http://feynmanlectures.caltech.edu/I_02.html#Ch1-S1

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