What is the speed of propagation of gravity? Does it ‘move’ at the speed of light (as supposed by general relativity), or does the gravitational force propagate instantaneously (as supposed in orbital mechanics)?
I remember a discussion on the topic thirty years ago (when I was much smarter) with a physics professor at good ol’ UGA. Why the subject came up at all is lost to time. We talked about it on and off during the course of two hours of playing handball on the indoor courts at old Stegman Hall (which is long gone, I understand). I don’t much recall what we resolved during the discussion. I mainly remember that, as usual, I got thoroughly clobbered at handball for two straight hours.
Those random memories popped into my head this morning as I sat out on our lanai, staring off into the jungle behind our property with a large cup of strong coffee. The word ‘propagation’ was behind the whole episode because it was one of those mornings that caused me to meditate on one of science’s great imponderable questions. To wit:
What is the speed of propagation of coffee?
There is no easy answer. Obviously, coffee propagates neither instantaneously nor at the speed of light. If either were the case, after drinking the first cup of coffee I wouldn’t have still been sitting there with my thousand-yard stare and my fine motor skills seriously impaired.
[Delaying the morning’s ablutions until full mental functions are achieved is mainly a safety issue, by the way. The razor’s cold steel is not something any man should have to encounter until his mind is alert and his hand is steady. Trust me on this.]
I think there is no ‘absolute’ speed of coffee. There seem to be many variables involved, because on different days it propagates at different rates. Strength of coffee, volume of cup, mass of the consumer, length of sleep, environmental humidity, time of day and day of the week are just a few of the factors that impact the equation.
It’s difficult to study empirically because coffee displays the intermittent ability to camouflage its presence. Sometimes I drink a cup of coffee, it kicks in directly and off I go about the day. At other times, however, one cup will have no apparent effect; neither will a second cup. Then, halfway through the third cup the coffee drops its clever camouflage and I’m bouncing off the ceiling. Damned stuff.
Pondering the universe’s great imponderables rarely produces any sort of solution, and this morning was no different. In truth, I think the main idea behind pondering (which is much like meditation) is to ponder a question until it becomes moot.
“By doing nothing, everything is done” as the Taoists would say.
