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Old 2022-11-11, 08:24   #12
xilman's Avatar
May 2003
Down not across

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Originally Posted by LaurV View Post
I think I asked this once, but I don't remember the outcome. Getting older. Sorry...

If I post a picture of the moon, of "infinite" resolution (i.e. one can zoom into it as deep as he likes, in "reasonable" limits, say, a trillion pixels or so), taken from the surface of the earth, then, can a skilled guy pinpoint my location? (and the time the photo was taken, I think they are quite related).
Hmm, nice one. Time to start thinking.

First it is not clear to me that you need to post the time it was taken. In principle the shadows should give local time of day and libration (measured from the shape of the lunar profile) will give a good estimate of the date. I accept there may be some ambiguity but most alternatives can be eliminated by the constraint that you had to take the image (so future times can ignored, as can those too far in the past).

As for the location in space, I need to think much more carefully. It is possible, for instance, that the air pressure and temperature at your position needs to be taken into account because of its effect on the refractive index of the atmosphere.
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Old 2022-11-13, 10:39   #13
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Jun 2011

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This was a sincere question. As well as the fact that I remember asking it here, and we discussing it, but I don't remember the conclusion. I don't know the answer.

And not posting the time, that would be too easy, with some computer simulation (or even web search, haha I assume "how the Moon looks from different regions of Earth, at this specific time?", I did not search, but you got the idea) - I just post a picture of the Moon. No other info.

In theory, the Moon is seen differently from different places of the Earth, I assume, and at different times. Shadows are different, angles are different, that is why I say one may need to zoom in deep enough to see the details he wants to see. The latitude on earth should be easy to get, in that case. The moon looks different from the poles, from the equator, or even from northern/southern hemisphere (personal experience, Romania vs Thailand vs Australia vs China, even naked eye).

Where the things gets murky, it would be the longitude. As the earth rotate, people from equator, for example, see the moon in the same point of the sky at different times, but I assume the moon also "rotates" a bit, and the sun/shadows, etc., will not look the same (yeah, I know about tidal lock).

Of course, this is only assumption, common sense and wild ass guess. In reality, the things may look different, that is why somebody with real astronomy knowledge may weight in.

Last fiddled with by LaurV on 2022-11-13 at 11:04
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