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Originally Posted by picassoscat
The laser reflector has been used for years. I believe we have an astronomer on site. perhaps he could shed further light on this.
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It works similarly to sonar. We shoot a laser beam at a nearby object (by which I mean inside the solar system) with a frequency that's not commonly generated by natural processes to help cut down interference, and measure how long it takes for it to bounce back. Since all lasers are light and move at the speed of light in a vacuum which is an exact value (299,792,458 meters per second), we multiply this value by the number of seconds it took for the beam to return, and then divide by two since this time would be roundtrip. This is extremely accurate.
Interesting factoid: the reason the speed of light in a vacuum is an exact value is because the meter and, consequently, the foot, yard, and mile are defined by it. One meter is 1/299,792,458 the distance a light beam goes in one second. If the speed of light were measured more accurately and the outcome different from 299,792,458, the length of the meter would actually adjust to compensate and keep the value exactly at this number, as opposed to the number changing.
Quote:
Originally Posted by picassoscat
But, I believe we went. Just am curious as to ehy we did not pursue to moon further and jumped to Mars exploration when there are so many mineral potentials on the moon.
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We stopped working on it in the 70's and NASA's funding got severely cut. The Cold War spawned the Space Race, but it killed it, too.
Quote:
Originally Posted by picassoscat
Laser Ranging Retro-reflector Experiment
"The reflected laser beam is observed with the telescope, providing a measurement of the round-trip distance between Earth and the Moon. Laser beams are used because they remain tightly focused for large distances " -excerpt
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Exactly. Light beams normally fan out, but lasers stay focused. Also, light is normally heterogeneous, meaning it's composed of many different wavelengths of radiation. In lasers, all the photons are identical--the whole beam is one wavelength, so it's far more coherent.