Question

There are numerous stars even 100 times bigger than the sun in the universe, then why still the univerese is dark?

Answer 1

Dear Student,

In day time,our sky is blue because the light from the sun hits the molecule in earth atmosphere and it gets scattered in all direction.The blue colour is due to scattering process.In night time,it is dark because part of our earth is facing away from sun and there no nearby source of bright light to get scattered.

If we are in moon, which has no atmosphere if will be dark both day and night.

If universe is full of stars,we expect the night sky to be bright from those stars.Yet the space is dark.This paradox is called as Olbers Paradox.It is a paradox because of contradiction between night sky should be bright but in reality its dark.
Our universe is 15 billion years old,this means we can see objects as far away as the distance of light can travel in 15 billion years.The light from stars farther away from us has no time to reach us.

The sky may not be bright from all the visible light from stars because as the light moves away from you, the wavelength of light is made longer ie towards red color. This means when light from stars are moving away from us, it will be shifted more towards us or even futher so that its not visible.

Regards.