View Full Version : What is natural light like on the Moon?

07-31-2015, 07:00 PM
I'm writing a YA SF that has a bunch of scenes set on the Moon. It's a really brief question, which makes me feel like I'm being kind of blunt/rude, but I don't think it needs too much elucidation: what's natural light like on the Moon? In movies, it always looks kind of dark--would they always need artificial forms of light to go about their day, or would there be periods in which the sunlight was in any way comparable to that on Earth?

Thank you so much in advance for any insight or speculation you guys might be able to give me.

Dennis E. Taylor
07-31-2015, 07:57 PM
It would be harsh, with sharp shadows. No atmosphere to scatter the sunlight. shaded areas would only be illuminated by reflection from nearby objects. OTOH, out in the sunlight it would be very bright. Again, no atmosphere to filter the sunlight.

King Neptune
07-31-2015, 10:03 PM
It would also be bluer than Earthly sunlight is, and the UV index would be high.

08-01-2015, 05:45 AM
what's natural light like on the Moon?

Ever been in direct sunlight? Same thing. :)


08-01-2015, 06:00 AM
In movies, it always looks kind of dark--would they always need artificial forms of light to go about their day, or would there be periods in which the sunlight was in any way comparable to that on Earth?

Do a Google search for Apollo mission photographs. It's plenty bright on the moon. You may get the perception that it's dark because their is no atmosphere, and so the light strikes the surface and goes off into black space.

08-03-2015, 03:25 PM
Thank you, guys. :) I wasn't sure if Apollo photographs would be accurate, or if Moon sunlight wouldn't translate across camera lens' well (I know, I know, I'm silly). The descriptions and the nudge towards those photographs is super helpful and, of course, now off to find a patch of direct sunlight to stand in, thank you, WeaselFire ;)

The novel, naturally, involves what is essentially a bubble city, with an atmosphere not dissimilar to Earth's inside, and straight up Moon outside. Kind of excited that there would be a dramatic lighting shift between the two.

Again, thank you. :) :)

Max Vaehling
08-05-2015, 04:34 PM
The Apollo images are a little bit inaccurate in that they didn't capture the starlight. I've been looking around for cnfirmation on this because I'm working on a comic set on the moon, but I seem to remember (and it would only make sense) that you'd get a great view of the stars. Well, maybe not when the sun's up because it might blot some of them out - this is what I've yet to find anything about.

Apart from that, it's pretty much what you see in the footage. Stark contrasts, really light on the surface, but with a dark sky.

Thanks to King Neptune for pointing out the bluer light. Forgot about that. Also, this notion of the sun being yellow that we often see in space movies? Not a bit. Sunight is white. I'm assuming it's even clearer from the moon.

Then again, there's no reason to assume that within an artificial atmosphere bubble, it'll be pretty much like Earth. If they can build it one way, they can build it another.

08-05-2015, 05:17 PM
The light cycles on the moon are different than on Earth. You'll get a couple weeks of sunlight, then a couple weeks of no sunlight (unless the city is positioned just so on one of the poles or something). This article (https://en.wikipedia.org/wiki/Far_side_of_the_Moon) may be a helpful starting point to understand this cycle.

Beyond that, I concur with the previous statements. Inside the atmosphere bubble city, sunlight would behave much as it does here. Outside, expect white light, stark shadows, and quicker-than-Earth sunburns on any skin without UV protection. And like Max alluded to, I expect at night the view of the stars would be phenomenal.

Dave Williams
08-07-2015, 09:47 PM
Angry Guy's comment on scatter is very important. On Earth the atmosphere diffuses light; you get light from 360 degrees even when the sun is slightly below the horizon.

On the Moon, sunlight is like a flashlight in a dark room. If you look down a shallow hole, it's just black. If something is in shadow, it's almost invisible. (you get some light bouncing from the ground and surrounding objects, so they're not *quite* invisible)

If you look at the Lunar exploration pictures on on NASA everything looks "off"; the shadows are all too dark and too sharp, and things not in direct light are oddly dim.

Several of the astronauts commented about the effect, which greatly complicated some of their activities; they had a lot of trouble seeing things not in direct light. At least one recommended they bring flashlights or reflectors on later trips.

09-05-2015, 02:00 AM
Regarding being able to see stars, if you're looking at something bright then your eye's pupil will contract and it'll be harder to make out the stars. But if you faced away from the sun and looked up at the sky long enough for your eyes to adjust, you'd be able to see the stars perfectly. Also: they wouldn't twinkle, since that's caused by the Earth's atmosphere.

Robert Dawson
09-05-2015, 04:16 AM
The part of the Moon that faces the Earth is, when not illuminated by sunlight, often illuminated by earthlight. The Earth has 4 times the radius and 2.5 times the albedo, so earthlight is on the average about 40 times brighter than moonlight in the same phase. I think this would probbaly be bright enough for color vision, and (depending what part of the Earth was visible) strongly blue-tinted. So it might be like a stage illuminated by a dim blue spotlight.

09-05-2015, 09:36 PM
I was about to mention Earthlight! It looks beautiful from the Earth. The New Moon in the arms of the Old.....

09-06-2015, 07:01 AM
It would also be bluer than Earthly sunlight is, and the UV index would be high.

Not. The "blue" of the Earthly sky is due to absorption of longer (redder) wavelengths of sunlight by atmospheric gases. The surface of the moon gets unadulterated full-spectrum sunlight, very bright, which would, to a human eye, simply be bright white.


09-06-2015, 07:29 AM
And remember that from any stationary point on the Moon's surface, the Earth will always be in the same part of the lunar sky, because the moon is locked to it, rotating on its axis only once per trip around the Earth. So while the day/night cycle is 28 days or thereabouts, whether you can see the Earth (and where it is in the sky) will always depend on where you are on the moon's surface. The phase of the Earth will depend on the angle the sun is shining on it from (and it will be new when the moon is full to us and vice versa). The "full" Earth will be seen when the sun is behind the moon and it's dark on the part that faces the Earth. The Earth's phases as seen from the moon are "offset" to the moon's phases as seen from Earth.

And you will never see an "Earthrise" or "Earthset" from a stationary point on the surface of the moon (of course, you could if you yourself are moving over the moon's surface to where the Earth comes above or goes below the horizon).