There is light in space. Light only really “shows up” when it makes contact with something. Like shining a flashlight in the dark. When you have dust, you can see the beam of light. But, if it’s perfectly clear, you only really see the part the light hits.
Same thing in space. There just isn’t anything for the light to hit.
Everything we see is because of reflected light. This is why when you turn a light on in the room the light bounces off of objects and hit our eyes in a specific way. This is why the moon and asteroids and anything else that’s big enough for us to see has light reflected off of it for us to see it, but in the general emptiness of space there’s nothing large enough for us to see so it is dark. This is why you can look up in the sky during the daytime with no clouds and all you see is light reflecting off of the atmosphere.
If you throw a ball as hard as you can into nothing, why doesn’t it hit you in the face?
Well, because it doesn’t have anything to bounce off of. Light works the same way, you can only see light that hits your eye, and light travels in straight lines (ignoring that gravity can bend light because that’s irrelevant to this answer). So if light *isn’t* traveling towards your eyes, you can’t see it. Most of the light the sun gives off never hits anything that bounces it back to your eyes, so you never see that light.
So get a powerful flashlight and go outside at night. Turn it on, point it at something and you will see the light. On the house. On your car. On the ground.
Now, point it up into the air. Unless the air is dusty or very humid, you won’t see anything. That’s because we see light as it is reflected off of things. If there’s not a thing, the light doesn’t reflect back to us and just… goes.
It’s the same way in space, and space is incredibly empty.
You see light on earth (day) because the atmosphere scatters that light, and it is bright enough that it will block out the stars (in most cases). But at night the absence of light is more akin to the natural look of space.
If you live near a city you will be able to see the light pollution of that city at night, and not be able to see stars.
In fact, in LA, an earthquake caused a total blackout of SW CA and 911 was inundated with calls asking if the giant ‘gash’ in the sky caused the earthquake. The truth of it was most people were seeing the milky way for the first time in their lives because all the surrounding light pollution was blocking it out.
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