tj@juno.ll.mit.edu (Thomas E. Jones) (07/14/90)
I thought it was obvious why the human body follows a 25 hour (or over 24 hours) cycle when isolated from external stimulus (the sun.) What's wrong with the following simple explanation: All physical systems that have a periodic behavior (swaying of a tree, swinging of a pendulum, vibration of a tuning fork, bouncing of an automobile) have one resonant frequency, when they are relaxed and allowed to oscillate. For example, letting go of a pendulum to let it oscillate, or pushing the bumper of an automobile down and then letting go of it, produces a frequency (or period) which I call the "rest" resonant frequency. However, if we want to continously excite one of these systems to make it continously oscillate, or get the maximum amplitude we excite it at a slightly higher frequency, which we can call the "driving" resonant frequency. All physical systems I know of contain these two different resonant frequencies: If a car hits a pot-hole, it may bounce up a down a few times at a certain frequency, but if we want to push up and down a bumper to get the thing bouncing as far as possible, we excite it with a slightly faster frequency. Similarly, a child on a swing without moving gives one frequency (which dampens out eventually) but when a child "pumps" the swing to drive it, he/she drives it at a slightly higher frequency. A last example, a peizo-electric crystal ultrasonic transducer may be most sensitive to receiving a frequency around 37 KHz, but puts out most sound at around 40.0 KHz. The easiest and most profound illustration of this effect is to find a sign on a pole sticking out of the pavement (a no-parking sign or a basketball-hoop works well for this.) Excite the system by pressing and pulling gently until you bring up a high amplitude oscillation. While exciting this system, measure the frequency. Then let go of it so you're not exciting it any more (the "sun" is gone.) Without waiting for the amplitude to go down, measure the frequency when it's not excited, and it will be measureably lower. So obviously, the human bodies "rest" period (when not being excited by the sun) may be around 25 hours so that when it is excited by a 24 hour signal (slightly lower "sun" exciter period) the amplitude (daily hormonal cycles) is maximized. Isn't this obvious? I thought this was a well-understood and generally accepted idea. - Thomas E. Jones tj@xn.ll.mit.edu -- tj@xn.ll.mit.edu or tj@ll-xn.arpa (one of these should work) Thomas E. Jones, home (617) 924-8326 work (617) 981-5093