Why is the sky black?

Question

If the universe is infinite, then where ever you look, you'd be looking at the surface of some star. Therefore, it should be bright all over.

Answer 1

  It's only black where there is no light emission or reflections..

Answer 2

I actually asked that question in school when I was little, and had my less-than-competent science teacher mumble something incomprehensible enough about the sun and clouds and gravity and Einstein to make me regret showing independent thought and leave him alone. I first found a good answer to my question  in Hawking's clever, clever book, "A Brief History of Time". It turns out that if the Universe was infinitely large and infinitely old, then we would expect the night sky to be bright from the light of all those stars. Every direction you looked in space you would be looking at a star. Yet we know from experience that space is black! This paradox is known as Olbers' Paradox. It is a paradox because of the apparent contradiction between our expectation that the night sky be bright and our experience that it is black.

Many different explanations have been put forward to resolve Olbers' Paradox. The best solution at present is that the Universe is not infinitely old; it is somewhere around 15 billion years old. That means we can only see objects as far away as the distance light can travel in 15 billion years. The light from stars farther away than that has not yet had time to reach us and so can't contribute to making the sky bright.

Another reason that the sky may not be bright with the visible light of all the stars is because when a source of light is moving away from you, the wavelength of that light is made longer (which for light means more red.) This means that the light from stars that are moving away from us will become shifted towards red, and may shift so far that it is no longer visible at all.

Hope that was helpful.

Answer 3

Scientists worked out that the universe was expanding, that the stars were all rushing away from one another after the Big Bang, and the further the stars were away from us the faster they were moving, some of them nearly as fast as the speed of light, which was why their light never reached us.

Answer 4

This is because the universe is finite in age, and it obviously started off as a point.  Plus the universe expands faster than the speed of light, therefore, you cannot see light coming at more than a certain distance.  The black in the sky means that you are looking before the beginning of time.  

Answer 5

Congratulations!  You have discovered Olbers Paradox all on your own.  The blackness of space is reason to believe it is not infinite.  Others have mentioned this but I just had to respond to Britney M's answer

Britney M, actually we know the answer to why both of those are black.  Cool, huh?

Comethunter, if they lit enough candles, evenly distributed across the length and width of their country such that it appeared as a continuous wall of flame from one end of it, you *would* be able to see it from this far away.  That's the proper analogy.

Vesper, good answer.

Answer 6

its infintancy is the reason for irs darkness  

Answer 7

What you are talking about is Olbers' Paradox - it was described by the German astronomer Heinrich Wilhelm Olbers in 1823 (but not published until 1826 by Bode) and earlier by Johannes Kepler in 1610 and Halley and Cheseaux in the 18th century.

You would be right if the universe was static (meaning it isn't expanding).  In fact, the fact that the night sky is dark was one of the "proofs" that the universe must be expanding.

Answer 8

wow, that's awsomely twisted logic that makes complete sense! I always thought the sky is black because not enough light reaches us, of course some stars might be so far away that their light doesn't reach us.

Answer 9

the universe is basically all empty space. the furthest stars are so far away that we can't see them.

Answer 10

Yes, space is infinite as far as we know. But that does not mean there are stars in every spot you look at. Many are too far for you to see, but there is more empty space then there is of stars (light for you to see). You should do some reading on Dark Matter if you really want to understand this better. I wont go into depth...  :)

Answer 11

You are part correct.  If the universe was infinite in size then it would also be infinitly bright.  BUT....the universe is not infinite, so it appears black.  Black is the absence of light.

Answer 12

This is one of the proofs that the Universe is NOT infinite.

"Limitless" and "Infinite" are not quite the same.

Answer 13

most stellar objects are too far away for their light to travel all the way to earth.

that is why on  a clear night, if you take a telescope an point it at an area with only a few stars, you will see dozens more- more magnification, more stars--

that is why you only see the "few" stars you do

Answer 14

why are people black?its something the world will never know

Answer 15

Yeah, but if you standing in Texas and the Earth was flat could you see a lit candle in China if it was nighttime? No, you couldn't. You might have said yes  but the fact is You most probably could not.  Its the same thing when you look up into space. Most areas that look like they are dark actually have stars in your direct line of sight even if you can not see them. They are just too far away and too dim to see with the unaided eye. If you lit a candle a billion times bigger in China then you might be able to see it because its bigger and brighter. The same goes with stars. There are stars of all kinds of different sizes and brightnesses, some are closer and some are further. Just because there are stars that probably cover almost every area of sky doesnt mean that they are bright enough to light the Earth. Only one does....The Sun. The others are simply too far away to provide any light to us.