> Many years ago I ran into a combined group on Mt. Wilson, our local > broadcast farm in the mountains, from Cal Tech and MIT that was measuring > the movement between Southern California mountains using lazers. While > this was scientifically fascinating, it gave me the willies.
I'm in Silicon Valley. There is a big USGS group here. They used to have a laser setup between Black Mountain and Mt Diablo which are on opposite sides of the fault, roughly 50 miles apart. They used to fly a helicopter along the beam, measuring the temperature so they could get a more accurate answer. Fault motion is ballpark of 1 inch per year, the same as your fingernails grow. So they would want to measure the distance to a (small) fraction of that. I did a quick search, but I didn't find the speed of light as a function of temperature. 50 miles is 3E6 inches so 1 PPM would be a big deal. I think they do it with GPS now. -- These are my opinions, not necessarily my employer's. I hate spam. _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.