[time-nuts] Steve's new QTH...
hmurray at megapathdsl.net
Tue Sep 7 18:57:07 UTC 2010
> 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
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.
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