Speed of light and Moon distance from an occultation of Mars by the Moon

by ColinWright • 11 years ago

47 4 11 years ago

ISL• 11 years ago

An excellent effort; proper execution of experiments is independent of the sensitivity. It's very inexpensive to get good at the science and art of experiment itself. Proper execution is the hardest part; improved sensitivity is in significant part a question of available resources (cleverness is significant, too).

(The precision-metrology part of me feels compelled to point out that any absolute measurement of the speed of light using this method should include an estimation of the covariance of the result (and its uncertainties) with the variation of the assumed value of c used by GPS for timing and position determination).

nathancahill2• 11 years ago

That, and the citizen science movement helps tremendously. It's what I love most about eBird[0]. Thousands of people collecting observations (with varying degrees of accuracy) provide a wider and more accurate picture than any number of scientists could deliver on their own.

[0] http://ebird.org/content/ebird/

asanagi• 11 years ago

What a fascinating paper! Although I know the speed of light is finite and have considered many of the implications of relativity, I never thought of the effects on the apparent occultation of two celestial bodies at significant distances from one another relative to the observer. The moon's transit between Earth and Mars would not appear reciprocally the same to observers on both planets. Obvious in retrospect, but the layman does not tend to consider relativistic effects in this kind of simple geometric reasoning.

There's enough distance between us and the Moon that if you had a flashlight bright enough, you could easily perceive the delay between switching it on and seeing the Moon's surface brighten, as the light made the return trip. Something to think about next time you look up at the Moon and wonder about its scale and distance.

nathancahill2• 11 years ago

Hey asanagi, if you see this, you've been shadowbanned. I feel bad since you've been posting decent comments.

Speed of light and Moon distance from an occultation of Mars by the Moon

Related Stories