How is light used to study space?

Question

sreekar369 · Answer

Well... 
We use the speed of light to calculate how far apart the stars are, and to estimate the size and age of the universe. Speed-of-light calculations are what confirmed that the universe is expanding. And because light takes a certain amount of time to get here, when we look at the stars, we're literally looking back in time, to what the universe was like millions of years ago:

anonymous · Answer

Light quantity in space is calculated through photons, because light can't really be measured, rather it is merely a quantity.

sreekar369 · Answer

i m nt saying tht light is calculated by light we calculate how far are the stars