Would lunar cities be visible from the earth?

Seems to me that I’ve scene a photo of the Earth taken from the Moon, and you can’t see the lights of cities - are these only visible from near orbit?

And if so does that mean we would never see the twinkle of lights from cities on the moon, if established at some stage in the future?

This is totally off the cuff, and possibly I haven’t thought about this carefully enough, and certainly haven’t crunched any numbers, but in order for someone on the Moon to see lights on Earth, or vice versa, they have to be looking at the dark side of the object. A quarter or crescent won’t do, I think, because the light from the sunlit side of the object would much, much brighter than the pitiful artificial lights. However, when we are looking at the dark side of the Moon (new moon) the Sun is always in the sky, and the same would be true of people on the Moon looking at the dark side of the Earth (new earth, which is when the moon is full in Earth’s sky.)

The best chance we’d have to see city lights on the Moon from Earth would be a total solar eclipse (and the corona of the Sun might be too bright) or a lunar eclipse (and the light that refracts through the Earth’s atmosphere and gives the eclipsed moon its reddish hue might drown out the lights, also.)

If you were on the Moon, you’d have a chance to observe the dark side of the Earth in all its light-polluted glory during that lunar eclipse, when the Earth passes in front of the Sun from your point of view. However, a red ring would appear around the limb of the planet (the aforementioned refracted light) and I don’t know how easy it would be to see any city lights in contrast to that. During a solar eclipse, you’d be SOL; the Moon’s shadow is very small on the face of the Earth, and the vast majority of the face of the planet would be illuminated by sunlight.


NO AFIK Lunar cities when and if built will be underground constructs to maintain temperature stability. There will be no need for a grid of street lights or something similar.

Perhaps if very large areas were strip mined, or otherwise disturbed, we could see them. Not in any detail, just the albedo difference between the disturbed and pristine areas. (this is a WAG, but the first thing that came to mind)

With a nice, stable atmosphere and a big telescope, the very smallest details that you can make out on the Moon are about 1 km. With the naked eye, it’s more like 100 km.

However, if the strip miners used explosives, you might be able to see them with your telescope:
Movie of meteoroid striking the moon, taken through a 10" scope.

Much of the earth is frequently obscured by clouds when seen from space, even from the fairly close-in space station. You have to be much closer (underneath the clouds) to see city lights.

Heck, even when I’ve flown on airlines, you often can’t see much of the earth’s surface due to clouds.

Hmm. So day side no, dark side possibly. If you can see a candle kilometres away in a desert, then surely you’d make out a pinprick of light representing an above-ground city on the moon (eg. a launch site) on the dark side, ambient conditions being right.

Huh? Why so? I don’t understand…

Simple: the Moon shines by the reflected light of the Sun. Therefore half the Moon’s surface area is illuminated by facing the sun and half is unlit. The face of the Moon which is tide-locked facing Earth is fully illuminated at the Full Moon, when the Moon is on the far side of Earth from the Sun. At New Moon, when the side of the Moon facing Earth is dark, the Moon is on the side of the Earth towards the Sun. Being on the far side of the Earth from the Sun leads to the condition we call “Night” and being on the near side leads to “Daytime.” (This isn’t intended to be supercilious but to spell it out in the sort of detail that leads one to grasp it, with the consequent :smack: reaction – I had exactly the same problem and the same reaction once I got it.) Obviously there is a night sky during nighttime at New Moon, but the Moon is below the horizon during it.