This is CBS Eye on the World.

Here's John Batchelor.

I welcome dark matter, what we know and what we want to know.

A new book, The Elephant in the Universe, 100 years search for dark matter.

Guvert Schilling is the author, and we begin 100 years before this moment.

Jacobus Cornelius Coppin, born 1851, writes a paper in May of 1822 that is revelatory.

It's entitled First Attempt at a Theory of the Arrangement and Motion of the Ciderial System.

That paper has in it this sentence, the amount of dark matter from its gravitational effect.

Govard, a very good evening to you. Thank you.

Introduce us to Mr. Kaptan.

What was it that brought him to make that speculation that we now spend so much time puzzling over?

Good evening to you.

Yeah, hello.

Very nice to meet you.

And thanks for having me.

Jacobus's captain was a Dutch astronomer. And as you said, his paper in 1922 was a groundbreaking paper because one century

ago, astronomers hardly knew about the universe that we know of. We now have this wonderful

James Webb Space Telescope

that is discovering galaxies out to billions of light years away,

but a hundred years ago, no one was even sure whether or not our Milky Way was alone.

And Capthain was one of the few who thought that the Milky Way galaxy was the only thing in the universe. It was later called the Captain Universe, because he thought that was all there was to it.

And he thought that other spiral galaxies, spiral nebulae, as they called them back then, were actually objects in the Milky Way.

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