If light from stars travels outward constantly. Why is the sky not filled with light.?

Answer 1

If the universe spreads out to infinity and it has been from the limitless past, you would see stars in every direction. The universe should be filled with star light. But in reality, it is not. This is known as "Olbers paradox".

Rather than more cut and paste, here's the info:
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Answer 2

Pretty easy answer. The universe is NOT infinite. Therefore there is not an infinite number of stars, so the night time sky is not fully illuminated.

In fact, the accepted opinion of today is that the universe is expanding because virtually all galaxies when viewed from Earth have their light red-shifted--the doppler affect. Think of a car going by blowing it's horn...the pitch changes from high to low pitch as it drives by because the sound waves are compressed in front due to its speed and longer at the rear as it drives away...The same idea happens with the light from galaxies moving...The speed of light is constant, but the frequency and wavelength can change resulting in more red (moving away) or more blue (moving towards).

ANYWAY if the universe is expanding, it can't be infinite...hence the sky is not completely packed with light at night.

Answer 3

Olber's Paradox is only a factor if the universe is infinite. If it is finite, which is more than likely, especially in consideration of the extent of light emitting matter, it is not a factor.

The reason the universe is not light, is that like all radiation, and including mundate Earthly things like sound waves, weakens by the square of the distance.

So, two stars of equal brightness, but one is 10 lt yr and the other 100 lt yr: we receive 100 times more light energy from the nearer one.

Since the nearest star is 250,000 times father than the sun, its power is reduced by 250,000 x 250,000.

Which makes you wonder how we can see any stars. But that's all thanks to our wonderful pupils that open wide in the dark, and sensitive dim light receptors in our retinas that trip in when we are in the dark.

Answer 4

You only see one small part of it because the rest is going in the other directions. Imagine a sphere growing around the star. This is what the light is doing. As the sphere grows, there is less and less light per steradian. By the time the light gets all the way to you, it is a very small fraction of an arc second.

Answer 5

Another way of saying all that, without introducing any paradoxes, is to say that though the stars are very numerous, and in our terms each individual star produces a lot of light, the universe is mostly empty space, and the light is scattered so widely that it is almost dark out there.

A point source of light gives off light in all directions, but we see only the tiny fraction of that light that is coming straight at us. And in quantum terms they are very, very far away.

Answer 6

Simple answer? Because the sky isn't filled with stars.

Go out at night with 3 buddies. Have them stand a half mile down the road, spread out over 200 feet, and shine flashlights right at you. Is the sky filled with light?

Answer 7

tolnalc1 hit the nail on the head, but didn't go far enough. Olber's Paradox is violated due to the presence of gas and dust, which scatters light and prevents it from being viewed, and by the expansion of the universe, which causes the light from very distant stars and their galaxies (universes) to be invisible because of their distance (hence their velocity of recession).

Answer 8

because the intensity of light varies inverse square with the distance