The Sun and the Moon, just hangin' out

January 5, 2023 7:50 AM

Are there places in the world where the moon being visible during the day is rare, and conversely where it is very common?

So I was scrolling through Netflix and a stand-up promo had a joke (from Chelsea Handler I think) about a friend not realizing the sun and moon were different things because she had never seen them together. It's a joke, we are not dissecting that - it just made me curious if there are places in the world where seeing the sun and moon out at the same time is really rare, as where I am in the central US, it's common for the moon to be visible at midday.

Also conversely, are there places were it is extremely common?

posted by The_Vegetables to Science & Nature (8 answers total)

Best answer: Unless you're talking about cloud cover, no. There is no difference in moon visibility anywhere on Earth.
posted by jdroth at 8:23 AM on January 5, 2023 [3 favorites]

Best answer: In polar regions you don't see the sun at all for half the year, so you won't see both of them in the sky for half the year.

Cloud cover obscures the moon much more than the sun, so anywhere that gets a lot of cloudcover will not see the moon during daytime very much.
posted by BungaDunga at 8:25 AM on January 5, 2023 [1 favorite]

I suppose that in places where much of the sky is obscured by trees or tall buildings, or where looking up at the daytime sky is not something people do very much (for whatever reason, e.g. they are too busy not being run over by cars, or looking at their phones), a person might not have noticed the moon in the daytime sky. Thin cloud cover could have a similar effect.
posted by heatherlogan at 8:27 AM on January 5, 2023

Best answer: Here's a nice little write up about how/when the moon is visible in daylight.

The moon is visible in daylight nearly every day, the exceptions being close to new moon, when the moon is too close to the sun to be visible, and close to full moon when it is only visible at night.

Note the lack of mention of latitude or longitude, though it stops short of explicitly saying they don't matter (but they don't).

I suppose if one lived at the floor of a narrow deep valley so that the sun was not visible much, or if it was almost always cloudy, then it would be very rare to see the sun and moon at the same time.
posted by SaltySalticid at 8:28 AM on January 5, 2023 [1 favorite]

Best answer: I'm going to give you a slightly longer answer than my first one, which was perhaps overly concise.

It seems to me that your question is framed from a geometry perspective. You're not really asking about cloud cover and trees, etc. You're asking about whether it's rare for the sun and the moon to be present in the sky at the same time regardless of obstacles preventing us from viewing them on the ground. The answer is still: No, things are the same everywhere on Earth. And the reason is geometry.

I am not a math guy, nor am I a science guy, so I'm not going to try to explain the details myself. Instead, I'll point you to the book from which I learned most of my astronomy: H.A. Rey's The Stars: A New Way to See Them. Yes, this is a science book from the guy who did Curious George. Doesn't matter. It's fantastic. And its fourth section explains all the geometry/science of viewing celestial objects from a terrestrial vantage point.

You may be interested in the answers to this previous question on AskMe: What part of the Earth gets the most moonlight? Your question might not seem to be related, but it is. They're the exact same question (or exact same answer, anyhow).
posted by jdroth at 8:37 AM on January 5, 2023 [10 favorites]

A surprising number of people think it's rare for the moon to be visible during the day. Here are the basic facts about when the moon rises and sets, which I didn't learn until I was an adult:

The moon rises in the east and sets in the west, just like the sun.

When the moon is full, it rises just as the sun is setting, and sets just as the sun is rising, because it's on the opposite side of the earth from the sun. (That's why it's fully lit, because the sun is directly opposite it.)

The next night it rises a bit later, shortly after the sun sets, and sets shortly after the sun rises. Every day it rises and sets a bit later and looks a bit less full, gradually becoming a half moon and then a crescent moon, until it's the new moon, which is when the sun and moon are at the same place in the sky and essentially none of the moon is lit up. The new moon rises when the sun rises and sets when the sun sets.

And then it keeps on rising later each day and looking a bit more full each day until eventually it's full again and it rises at sunset.

It works the same way no matter where on earth you are. The only thing that's different is how long the days are. If the days are shorter (like in the north in winter), then there is less time when both the sun and the moon can be in the sky.
posted by Redstart at 9:29 AM on January 5, 2023 [13 favorites]

I am not an astronomer by any stretch of the imagination, but since the path of the moon across the sky can be 5 degrees to the north or south of the path of the sun, it seems like the polar regions would have more periods of moonless daylight than at places closer to the equator, e.g. on days when the sun never gets lower than 3 degrees above the horizon, the moon will have periods when it never rises.

Some obliquely relevant info at Astronomy.com.
posted by baseballpajamas at 9:31 AM on January 5, 2023 [1 favorite]

Those periods of moonless daylight would be exactly cancelled out by periods of all-moon-all-the-time daylight six months later; with the moon close to the non-setting sun, it would be even more non-setting.
posted by Hatashran at 10:00 AM on January 5, 2023 [1 favorite]