Christiaan Huygens

I esteem the invention of the pendulum clock as one of the most useful for astronomy.

The laws of collision of bodies are the foundation of all mechanics.

In the impact of hard bodies, the quantity of motion, considered in a given direction, is always the same before and after impact.

The true method of philosophy is to seek the causes of all natural effects from mechanical principles.

The hypothesis that light is a wave motion explains all its properties.

The phenomena of light are, in my opinion, impossible to explain by the emission of particles.

The sensation of light is caused by the agitation of the optic nerve.

The most beautiful discoveries are made not by the men of great ability, but by the careful observers.

The heavens are not so far removed from us as some imagine.

All the planets are, like our Earth, habitable.

The variety of nature is infinite.

To understand the motion of the planets, one must first understand the motion of a pendulum.

The greatest pleasure of life is in discovery.