But
though we don't know what it is, scientific men have learned how to
develop and use its energy, and among other things they have harnessed
it in the service of the wireless telephone.
"Take for instance a quiet lake. It may seem absolutely still, but
if you throw a stone in it you start a number of ripples that keep
spreading further and further out until they break on the shore. So
if you hit a drum with a stick, sound waves are stirred up that keep
spreading out very much like the ripples on the lake.
"Now electricity is something like that. It doesn't begin to act until
you do something to it. The impulse to ripple is in the quiet lake all
the time, but it doesn't ripple until you throw the stone in it. The
sound quality is in the drum, but you don't hear it until you hit the
drum with a stick. So you've got to put into the ether something that
disturbs the electricity in it, something that stirs it up, and then
this disturbance makes waves that travel on, just as the waves on the
lake follow one another and just as the sound waves from the drum keep
pushing each other along.
"A man named Hertz discovered a way of stirring up this energy,
snapping it, you might say, as a man snaps a whip. It was found that
these waves could be made long enough and strong enough to go all
the way across the Atlantic Ocean, in fact to go around the world.
Pages:
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39