Lunar Terminator Paradox

dvh•about 1 hour ago

> Now, what happens if the moon is not at the horizon, but higher up at the sky?

Moon follows the sun to the west so to move moon "higher" up in the sky you need to rewind time (15deg/hour). In e.g. 4 hours moon barely moves in it's 28 day cycle so the moon will look exactly the same (you can take a picture and compare). It's the earth rotation that make moon "go down" or up. I've read your article 2 times and I still don't understand what is apparent problem, no wonder AI had trouble. Also it's hard to reason about up and down when moon move along ecliptic which is curve. Down at noon points elsewhere as down at sunset.

Sharlin•about 1 hour ago

The sky is spherical, so straight lines in the sky aren’t straight lines on its 2D projection on the retina. Rather, straight lines are great circles. So if you trace the great circle that connects the sun and the moon, the moon should "point" along that great circle – which can be considerably off of what we think of as a straight line (which is curved in reality).

willrshansen•16 minutes ago

Was expecting time travelling moon robots. :(

ionwake•about 1 hour ago

is this a bad moment to mention how weird it is that the moon is perfectly positioned to create eclipses?

I think its pretty incomprehensible odds if you ask google.

But I could be wrong I know literally nothing about astronomy, it just always surprised me its not common, but it be cool if someone could explain that

bunderbunder•19 minutes ago

It’s more like, if the moon were much farther away then total solar eclipses wouldn’t happen at all. But the opposite is not true. If it were closer than total solar eclipses would be more common.

It is an interesting coincidence. But the statistician in me feels like calculating the probability is a bit spurious. For one, not all combinations of distance and size are equally likely, and running physical simulations to try and get decent Monte Carlo estimates of the odds feels a bit suspect - I imagine a decent chunk of what you’d be measuring is the influence of parameters whose values are empirically unknowable.

But, even more than that, it comes from the same place that requires me, when a cashier sees the total is exactly $50 and asks, “What are the chances of that?” to actively suppress the urge to say, “About the same as for $59.37.”

helterskelter2•23 minutes ago

The moon is 400 times smaller than the sun, but the sun is 400 times farther away, so they appear to be the same size. The solar eclipse we see, with the moon obscuring the sun but just allowing light around the edges the way it does, may be a very uncommon phenomena.

steanne•about 1 hour ago

it was my vague understanding that what is weird is the apparent size matching. since the moon is slowly moving away, eventually we'll no longer have total solar eclipses, just annular and partial.

teamonkey•17 minutes ago

The relative sizes are approximate, not perfect, but close enough that our monkey brains interpret it as more than a coincidence.

JumpCrisscross•9 minutes ago

Idk, one could come up with a hypothesis that eclipses provide the first tangible validation of a system of mathematics.

Lunar Terminator Paradox

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