I often say that when you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meagre and unsatisfactory kind.

When you cannot measure, your knowledge is meager and unsatisfactory.

If you can not measure it, you can not improve it.

Radio has no future." "X-rays are clearly a hoax". "The aeroplane is scientifically impossible.

In science there is only physics; all the rest is stamp collecting.

When you are face to face with a difficulty, you are up against a discovery.

When you can measure what you are speaking about, and express it in numbers, you know something about it.