logoalt Hacker News

Lunar Terminator Paradox

19 points • by dima55 • today at 9:06 PM • 4 comments • view on HN

Comments

dvh • today at 9:47 PM

> 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 • today at 9:55 PM

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).

ionwake • today at 9:50 PM

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

➕ show 1 reply