Carl Sagan

Imagination will often carry us to worlds that never were. But without it we go nowhere.

There are many hypotheses in science which are wrong. That's perfectly all right; they're the aperture to finding out what's right. Science is a self-correcting process. To be accepted, new ideas must survive the most rigorous standards of evidence and scrutiny.

We are a way for the cosmos to know itself.

We are star-stuff.

The use of our intelligence quite properly gives us pleasure. In this respect the brain is like a muscle. When we think well, we feel good. Understanding is a kind of ecstasy.

We are like butterflies who flutter for a day and think its forever.

We are the product of 4.5 billion years of fortuitous, slow biological evolution. There is no reason to think that the evolutionary process has stopped. Man is a transitional animal. He is not the climax of creation.

Absence of evidence is not evidence of absence.

You have to know the past to understand the present.

Each of us is a tiny being, permitted to ride on the outermost skin of one of the smaller planets for a few dozen trips around the local star.