#The_entropy_of_the_universe_after_the_big_bang During its li | Ethiopian Space Science Society Hawassa Branch
#The_entropy_of_the_universe_after_the_big_bang
During its life time living beings gain energy in the form of food which is as much as the energy released in the form of heat and waste substances. But these two types of energy differ in the degree of their entropy: heat has a high entropy while the energy accumulated in food (plants) has low entropy. But where does this low entropy in plants come from? Plants use solar energy for photosynthesis and therefore the Sun has even smaller entropy than plants.The Sun was born in a cloud of interstellar gas which must have a smaller entropy than the Sun. The interstellar cloud appeared soon after the Big Bang. Scientists know now that 2 minutes after it the universe was filled with an almost uniform hot gas of hydrogen and helium. But how can a system of gas have small entropy since its molecules are in great disorder? This is only true for a low density gas within which gravity can be neglected.But if the gas has a great density gravity is big enough to come into play and it is the reason for the low entropy of the gas.These arguments reveal that the time arrow could have its explanation in the highly ordered low entropy state of the early universe.
