Thursday, April 23, 2015

Double rainbow light show

I saw a double rainbow on the evening of April 21.  The stoplight wasn't red long enough for me to frame the picture with both arcs.  Try to imagine a faint secondary rainbow to the right.
The picture has so many layers of meaning.  Rainbows are a light phenomena.  Then there is the traffic light.  And the red light camera.  You can't tell from the picture, but I was driving southbound on Broadway, right outside the Department of Commerce labs in Boulder.  Those labs are famous for their light (laser) experiments.

When I was an undergrad at Berkeley, a professor told me to go to CU Boulder instead of MIT.  He had postdoc'd in Boulder and he extolled the advantages of high altitude for scientific productivity.

Spectroscopists usually make measurements under vacuum (relative to ambient air pressure).  Labs at high altitude get a head start on the ambient air pressure.

OK, that is not that much of an advantage with a good roughing pump.

The real advantage is the dryness of high altitude.  Water is a sticky molecule and it sticks to every surface of your apparatus.  Then it off-gases as the air pressure descends in the vacuum chamber.  Then it keeps off-gassing...  You can speed up the process by "baking" the chamber with a heat blanket as you pump it out.  But, it can take a whole day to get the water vapor level in a chamber low enough not to interfere with your signal to noise.

My former Berkeley professor said that those days add up to a whole lot of productivity when averaged over the years.  He thought that a spectroscopist's publication count should by handicapped like golf for the time spent pumping out water vapor.  ;-)

And you thought that Boulder has 3 national labs (NCAR, NOAA and NIST) because scientists have a high affinity for alpine recreation.  It's the lack of water vapor.  Really.

Did you read the scientific explanation Amanda Curtis' QUADRUPLE  rainbow photo?




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