The principle that physicists use to describe the loss of energy is called Entropy. It is proof that the universe is NOT eternal for it would of died out from heat death long ago.
But the day of the Lord will come as a thief in the night; in the which the
heavens shall pass away with a great noise, and the elements shall melt with
fervent heat, the earth also and the works that are therein shall be burned up. 2 Peter 3:10