Originally Posted by Richard J. Hanak

The idea of falsification in science is attributed to philosopher Sir Karl Raimund Popper. He accepted that unrestricted generalizations could not be verified. However, he called to our attention that they could be falsified.

Scientific theories make claims about expected observations. For example, suppose someone claims that at distances beyond 5 billion light-years all galaxies are red shifted. Although no amount of observation of such galaxies can verify that claim, one properly authenticated observation of a blue shifted galaxy in that distance range would falsify the claim.

According to Popper, falsifiability is the hallmark of science. No scientific theory is ever conclusively verified, no matter how often its predictions come true. And as most of us know, scientific theories are very prone to revision.