The absence of evidence is not the evidence of absence.

In science it often happens that scientists say, 'You know that's a really good argument; my position is mistaken,' and then they would actually change their minds and you never hear that old view from them again. They really do it. It doesn't happen as often as it should, because scientists are human and change is sometimes painful. But it happens every day. I cannot recall the last time something like that happened in politics or religion.

By looking far out into space we are also looking far back into time, back toward the horizon of the universe, back toward the epoch of the Big Bang.

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.

My parents were not scientists. They knew almost nothing about science. But in introducing me simultaneously to skepticism and to wonder, they taught me the two uneasily cohabiting modes of thought that are central to the scientific method.

How lucky we are to live in this time / the first moment in human history / when we are in fact visiting other worlds

Who will speak for Planet Earth?