Physics Today, Vol.25, p.28. You may, if you wish, compare mutations to accidental misspellings or misprints which even the most experienced copyist makes from time to time. And there is no way of avoiding this destiny. For the fateful principle known as the second law of thermodynamics, which stands today as the principal pillar of classical physics left intact by the march of science, proclaims that the fundamental processes of nature are irreversible. Nature moves just one way.
Some comets seem to tire out and die.
If galaxies didn't exist, we would have no problem explaining that fact. The problem of explaining the existence of galaxies has proved to be one of the thorniest in cosmology. By all rights, they just shouldn't be there, yet there they sit. Despite what you may read in the press, we still have no answer to the question of why the sky is full of galaxies, although we've succeeded in eliminating many wrong answers. The variations the satellite observed occurred over areas of the sky the width of 14 full moons areas much too large to have been the actual seeds of clusters of galaxies.