The earth’s moon is one of the least reflective astronomical objects in our solar system, and if you were to float in front of the sun as an astronaut (not really recommended) and see the moon aligned with the earth, you would see that the earth is far brighter than the moon, even when the two of them receive the same amount of sunlight.
The way that the human eye sees things is heavily reliant on light entering them directly. The reason that we can see things in the world is because they themselves are reflecting that same light into our eyes.
Or they can also produce their own light which is, again, directed into our eyes. So, an object will either reflect borrowed light or create its own in order for our eyes to see it.
The objects that create their own light will tend to be the brightest object nearby in relation to the objects that do not create and give off their own light. examples of this on earth are light bulbs, fires and screens. Examples of this in space and on an astronomical scale are stars.
These are the main producers of their own light, hence why the sun is the main producer of most of the light that we see and use to see other things on earth.
Stars are obviously some of the brightest things in the universe. And it just so happens that we have a star in our solar system. It would not, in fact, be called a solar system if we did not have a star.
And we would not be alive to make that statement if we did not have a star. Our sun is the reason for life on earth, we are orbiting the sweet spot where life can be sustained thanks to the sun. Not only because of its warmth but also because of its light.
The sun produces most of the light that we encounter on earth, it allows us to see most things on earth’s surface in the daytime, so what happens at night?
Well, planets and moons, including earth and its moon, do not produce their own light (obviously not including the unnatural light pollution that us humans produce). If they suddenly started glowing, it would mean that they were probably large enough to carry out nuclear fusion, something that stars do, thus it would make them a star and no longer a planet or moon.
So, how does the moon light up some of earth at night? Well, they reflect light, or borrow it from other astronomical bodies. In this case, the moon reflects the sun’s light when half of the earth is in darkness and facing away from the sun.
The moon is not the only astronomical object that reflects the sun’s light causing us to be able to see it. Sometimes we are able to see other planets in our solar system, simply because they are lined up in such a way on their orbits around the sun that they can reflect the sun’s light to earth and allow us to see them.
The reason we associate this light reflection more with the moon is because we can see it every night, the moon is constantly reflecting the sun’s light.
The brightness, or amount of light that these planets and moons reflect, depends on a lot of factors. It depends where the planet is in orbit around the sun, where it is in its own axis spin, and what the planet or moon is made of.
Earth appears bright because the light is reflected by the clouds in our atmosphere, as well as the shiny surface of the water on our planet. Planets that are covered in ice will have a similar effect, but planets or moons with an exclusively rocky or dusty surface will not be as reflective.
Therefore, the moon that orbits our earth, is not very bright in comparison to, say, Venus. So, the reason that we can see the moon is because it reflects the sun’s light, just like every other astronomical body in the solar system.