Observation and theory get on best when they are mixed together, both helping one another in the pursuit of truth. It is a good rule not to put overmuch confidence in a theory until it has been confirmed by observation. I hope I shall not shock the experimental physicists too much if I add that it is also a good rule not to put overmuch confidence in the observational results that are put forward until they have been confirmed by theory.

Every body continues in its state of rest or uniform motion in a straight line, except insofar as it doesn't.

Electrical force is defined as something which causes motion of electrical charge; an electrical charge is something which exerts electric force.

What is possible in the Cavendish Laboratory may not be too difficult in the sun.

For the truth of the conclusions of physical science, observation is the supreme Court of Appeal.

Probably the simplest hypothesis... is that there may be a slow process of annihilation of matter.

When an investigator has developed a formula which gives a complete representation of the phenomena within a certain range, he may be prone to satisfaction. Would it not be wiser if he should say 'Foiled again! I can find out no more about Nature along this line.'