why is space so "black"?


Charles Wang, I took an astrophysics class in college. If memory serves, had mediocre marks.

User avatar for Charles Wang

The relative sparsity of light might have something to do with it.

You may be surrounded by stars, but very little of the light energy is reaching any given point at any given time because they are extremely distant. See the inverse square law.


(For the purposes of this explanation assume a finite universe. It could get tricky if the universe is, in fact, infinite, as you'll need to factor in red-shift, the expansion rate of the universe, the age of its parts, etc. But clearly space isn't one giant whitescreen completely saturated with photons.)

Now, the atmosphere is not black during the day because it is (cosmically speaking) very densely packed with gas particles that refract the sunlight. If you were to exit the atmosphere during the day (while your part of the world is turned toward the sun), the sky would eventually thin into blackness as well.

adam, I think this is true.

User avatar for adam

I think another way to think about this is: why is daytime earth /not/ so black. When you look around you in the day, you see an earth covered in atmosphere, which has a lot more particles in it than space. When light hits air and dirt particles floating around you, it is scattered a bit, so that light that would have passed right on by can now bounce onto other objects and to your eyes. Space doesn't have an atmosphere like earth does, so you won't see the dull diffuse illumination you see on Earth.

Renush, set clock alarm

User avatar for Renush

Of course, what else would start a productive day than waking up on time and if you’re finding it hard doing this everyday update clock windows 10 even if you use your smartphone’s alarm clock or even a real alarm clock then you can try a different one and you can choose the built-in alarm clock in your Windows 10 machine.

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