In general we look for a new law by the following process. First we guess it. Then we…Now don’t laugh. That’s really true.
Then we compute the consequences of the guess to see what…if this is right…if this law that we guessed is right we see what it would imply.
And then we compare those computation results to Nature. Or we say compare to experiment or experience; compared directly with observation to see if it works.
If it disagrees with experiment, it’s wrong. In that simple statement is the key to Science. It doesn’t make a difference how beautiful your guess is; it doesn’t make a difference how smart you are who made the guess, or what his name is. If it disagrees with experiment, it’s wrong. That’s all there is to it.
— Richard Feynman