Why it is dark at night. Stars are producing enought light (fotons) to be alight at night?

Answer 1

This is the famous Olbers Paradox. If the Universe is infinite, and there are an infinite number of stars and galaxies in the Universe, then every line of sight should eventually end up on the surface of a star. So the night sky should be bright.

The reason the sky is dark is because the age of the Universe is not infinite; it is about 13.7 billion years old. That means we cannot see any further than 13.7 billion light-years into space. Objects farther away than that will remain permanently invisible to us, because the speed of light is also finite.

So the number of *observable* galaxies and stars is not infinite. And that's enough to make the sky dark.

Answer 2

The intensity of light diminishes with the square of the distance.
So, a light 16 feet away appears only 1/256 as bright as a light of the same brighness which is only one foot away.

The sun is roughly 93 million miles or 8 light-minutes away from earth, while even the nearest star is more than 4 light years, or over 250,000 times further away. If this star was equal in brightness to the sun, it would appear less than 1/64000000000 as bright as the sun.

The brightest 9100 stars (highest possible number visible to the naked eye on the clearest possible evening, observed from both the north and south hemispheres on the Earth) taken all together add up to only a miniscule fraction of the light intensity of the full moon, and a truly infinitesmal fraction of that of the sun. Even if you add in the combined brightness of the other 20 billion stars in the Palomar Digital Sky Survey, it makes little difference.

Answer 3

Stars are too far away to send significant amount of light our way.