True or falsification?

Science can never say never. That's why it's such a dynamic and exciting field. Theories have to fit the existing evidence, but the ideas change as new evidence comes to light. New discoveries change the world and the people in it. There are also sociologists and philosophers who study the way that science works on a personal level. After all science is done by people and scientists have all the usual human characteristics. One philosopher of science, Karl Popper, argued that good scientific theories need to be able to be proved wrong. For example, my theory is 'all cats are grey'. Someone can falsify this by showing me Eddy a lovely tabby cat, cute but certainly not grey! Until a non-grey cat turns up though (if ever) the theory is fine.