Episode Four of Cosmos is called Heaven and Hell. For me the two most memorable moments are when Sagan takes the Spaceship of the Imagination down to the surface of Venus and when he speaks so eloquently of the discoveries that let us explore that surface without even going there.

One of the incredible and thrilling things about science is that there’s a way we know everything we know. No divine revelation, no obvious truths, nothing but that which comes from rigorous logic and experimental evidence.

How do we know what stars and other bodies are made of? We can’t go there; most are much too far away. Even if we could, we couldn’t very well scoop up a bucketful of star and take it home to examine it. We need another way.

That other way is to look at the light from the stars. By sending that light through a diffraction grating we can spread the light out, and we find that the light of stars is made of all the colors of the rainbow. Amid all the rainbow colors are black lines. These are fingerprints, showing what atoms are present in the atmospheres of the stars. By examining the patterns of the black lines, we learn what the universe is made of.

This is one of the most profoundly beautiful and amazing findings of science. By examining closely a rainbow of starlight we discover the composition of the universe itself. And what do we find? We find that the universe is made of the same stuff as we are. We and the universe are one.

Not bad for a little stripe of colored light.

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