This is a summer rebroadcast of an episode of Tumble from a few years ago.

How big is the universe? And how do we know? It's a question that puzzled astronomers for centuries. They had no way to measure distance in space - until Henrietta Leavitt showed them how. Henrietta Leavitt was a "computer" in the 19th century, before there were computers, and she made an incredible discovery that would help change the way people thought about the universe - forever. Modern-day astronomer Karen Masters helps us tell her remarkable story.

If you like this episode, you'll love our free audio course, "Cataloging the Universe" where you'll learn much more about how Henrietta Leavitt's discovery made a big difference in astronomy - plus, you'll become a skywatcher yourself! "Cataloging the Universe" is more than a podcast. It’s interactive! Each episode - or lesson - in the series contains activities to complete while you listen. Plus, you’ll get discussion questions, graphic organizers, and a star journal to keep your observations in. Check out the series and download all the resources at ⁠our website⁠!

Hear more from Karen Masters in the bonus interview episode available to Patrons, when you pledge just $1 a month or more on our ⁠Patreon⁠ to support the show!

We have free resources available on ⁠our blog⁠ to learn more about the episode.

Also... psssssst.... here's that top secret crossword puzzle!