The first law of thermodynamics: What is it?

The first law of thermodynamics tells us the amount of energy in the universe is constant and can neither be destroyed nor created.

The evolution of the universe is therefore about a constant transformation of energy from one form to another. But no matter how many stars and planets the universe creates, how many civilizations spring up into existence on these planets, there will always be the same amount of energy as there was a second after the Big Bang.