[time-nuts] LIGO detects gravitational waves

[Poul-Henning Kamp]

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In message <1E75A9592178425ABD11390EB725D060 at pc52>, "Tom Van Baak" writes:

>Yes, the interferometer is 4 km in length but they bounce the beam back 
>and forth 400 times so the effective length is more like 1600 km. They 
>keep the mirrors stationary to "picometers". They use hundreds of clever 
>tricks to pull this off.

It's actually more amazing than that, each arm is a resonant cavity,
so while the actual laser is only about 10W, they have about 20 kW of
photons inflight at any one time.

With 20 kiloWatt of light safety-glasses are not _that_ important any more.

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