Astronomers estimate that the universe has about 100 billions of galaxies, each of which has about 100 billions stars. Given there are so many stars in the Universe, why isn't our night sky completely filled with starlight?

Ican determine the molar mass of an element by looking on the under the atomic mass for the element. for example the molar mass of phosphorus is 30.974 grams/mole. avogadro’s number tells me the amount of representative particles in 1 mole of any substance. this means 12.011 gram sample of carbon and a 32.0 gram sample of sulfur have the same number of atoms.