Page 58 - The Creation Of The Universe

56 THE CREATION OF THE UNIVERSE

Resonance and Double Resonance
Resonance is defined as the harmony of frequencies (vibrations) of two
different materials.
A simple example from ordinary experience will give us an idea of what
physicists mean by "atomic resonance". Imagine yourself and a child at a
playground where there are swings. The child sits on the swing and you
give him a push to get him started. To keep the swing moving, you have
to keep pushing it from behind. But the timing of these pushes is impor-
tant. Each time the swing approaches you, you have to apply the force of
the push just at the right moment: when the swing is at the highest point
of its motion towards you. If you push too soon, the result is a collision
that disturbs the rhythmic momentum of the swing; if you push too late,
the effort is wasted because the swing is already moving away from you.
In other words, the frequency of your pushes must be in harmony with the
frequency of the swing's approaches to you.
Physicists refer to such a "harmony of frequencies" as "resonance". The
swing has a frequency: for example it reaches you every 1.7 seconds. Using
your arms you push it every 1.7 seconds. Of course if you want, you can
change the frequency of the swing's motion, but if you do, you have to
change the frequency of the pushes as well, otherwise the swing will not
swing right. 33
Just as two or more moving bodies can resonate, resonance can also oc-
cur when one moving body causes motion in another. This type of reso-
nance is often seen in musical instruments and is called "acoustic reso-
nance". It can occur, for example, among two finely-tuned violins. If one
of these violins is played in the same room as the other, the strings of the
second will vibrate and produce a sound even though nobody is touching
it. Because both instruments have been precisely tuned to the same fre-
quency, a vibration in one causes a vibration in the other. 34
The resonances in these two examples are simple ones and are easy to
keep the track of. There are other resonances in physics that are not sim-
ple at all and in the case of atomic nuclei, the resonances can be quite com-
plex and sensitive.