Lunar Crater Radio Telescope on the Far-Side of the Moon (2020)

Re:Lunar Crater Radio Telescope on the Far-Side of the Moon ... by Asraelite on Wednesday September 15, 2021 @01:22PM (#28541839)

> 14 days out of 28

Out of 29 and a half actually.

I'm curious where the misconception that a lunar month is 28 days comes from. I believed it too but I can't find any good reason for doing so.

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Re:Lunar Crater Radio Telescope on the Far-Side of the Moon ... by credit_guy on Wednesday September 15, 2021 @02:27PM (#28542552)

You are right, and I was just lazy. 28 is an even number, and it felt nicer to say 14 days out of 28, rather than 14.75 out of 29.5.

Separately though, the misconception comes from the fact that we have 4 phases of the Moon (new, first quarter, full, last quarter), and it's easy to conceptualize that the interval between two is 7 days, or one week, rather than 7.38264725.

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Re:Lunar Crater Radio Telescope on the Far-Side of the Moon ... by dave333 on Wednesday September 15, 2021 @05:14PM (#28544445)

Sidereal month (relative to fixed stars) is 27.32 days. Synodic month relative to Earth is 29.53. There are other months that correct sidereal for motion around the sun, eccentricity of the lunar orbit, and tilt of lunar orbit, but the difference is tiny.

https://en.wikipedia.org/wiki/Lunar_month

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