Carl Sagan

Let's go back to the solar nebula... with the temperature declining the farther we get from the Sun. ...at different distances from the Sun, different materials will condense out, because they have different vapor pressures or different melting points. ...water condenses out roughly at the vicinity of the Earth, whereas silicates condense out closer to the Sun... you have to go out to somewhere near the present distance of Saturn before methane condenses.

Once upon a time, the best minds of the human species believed that the planets were attached to crystal spheres. ...Both in classic and in medieval times, it was prominently speculated that gods or angels propelled them, gave them a twirl every now and then. The Newtonian gravitational superstructure replaced angels with GMm/r2... as science advances, there seems to be less and less for God to do.

When you look more generally at life on Earth, you find that it is all the same kind of life. ...It uses about fifty fundamental biological building blocks, organic molecules. ...with trivial exceptions, all organisms on Earth use... an enzyme, to control the rate and direction of the chemistry of life. ...a nucleic acid to encode the hereditary information ...the identical code book for translating nucleic acid language into protein language. ...At the molecular level, we are all virtually identical.

I worry that, especially as the Millennium edges nearer, pseudo-science and superstition will seem year by year more tempting, the siren song of unreason more sonorous and attractive. Where have we heard it before? Whenever our ethnic or national prejudices are aroused, in times of scarcity, during challenges to national self-esteem or nerve, when we agonize about our diminished cosmic place and purpose, or when fanaticism is bubbling up around us-then, habits of thought familiar from ages past reach for the controls. The candle flame gutters. Its little pool of light trembles. Darkness gathers. The demons begin to stir.

Anything you don't understand, Mr. Rankin, you attribute to God. God for you is where you sweep away all the mysteries of the world, all the challenges to our intelligence. You simply turn your mind off and say God did it.

Those who are skeptical about carbon dioxide greenhouse warming might profitably note the massive greenhouse effect on Venus. No one proposes that Venus's greenhouse effect derives from imprudent Venusians who burned too much coal, drove fuel-inefficient autos, and cut down their forests. My point is different. The climatological history of our planetary neighbor, an otherwise Earthlike planet on which the surface became hot enough to melt tin or lead, is worth considering — especially by those who say that the increasing greenhouse effect on Earth will be self-correcting, that we don't really have to worry about it, or (you can see this in the publications of some groups that call themselves conservative) that the greenhouse effect is a "hoax".

The major religions on the Earth contradict each other left and right. You can't all be correct. And what if all of you are wrong? It's a possibility, you know. You must care about the truth, right? Well, the way to winnow through all the differing contentions is to be skeptical. I'm not any more skeptical about your religious beliefs than I am about every new scientific idea I hear about. But in my line of work, they're called hypotheses, not inspiration and not revelation.

Modern science has been a voyage into the unknown, with a lesson in humility waiting at every stop. Many passengers would rather have stayed home.

Do we, holding that the gods exist,

deceive ourselves with insubstantial dreams

and lies, while random careless chance and

change alone control the world?

In Mozambique, the story goes, monkeys do not talk, because they know if they utter even a single word some man will come and put them to work.

Ann Druyan suggests an experiment: Look back again at the pale blue dot of the preceding chapter. Take a good long look at it. Stare at the dot for any length of time and then try to convince yourself that God created the whole Universe for one of the 10 million or so species of life that inhabit that speck of dust. Now take it a step further: Imagine that everything was made just for a single shade of that species, or gender, or ethnic or religious subdivision. If this doesn't strike you as unlikely, pick another dot. Imagine it to be inhabited by a different form of intelligent life. They, too, cherish the notion of a God who has created everything for their benefit. How seriously do you take their claim?

Imagine we could accelerate continuously at 1 g — what we're comfortable with on good old terra firma — to the midpoint of our voyage, and decelerate continuously at 1 g until we arrive at our destination. It would take a day to get to Mars, a week and a half to Pluto, a year to the Oort Cloud, and a few years to the nearest stars.