How Do We Know How Far Away Distant Galaxies Are?

A video explains how we gauge the thousands, millions, or even billions of light years that separate us from the glowing objects we see with our most advanced telescopes.

Hubble_ultra_deep_field300.jpg

NASA

Over the past two decades, as the biggest, most powerful telescopes in history have transmitted their starry images down to Earth, we have seen pictures of places in the universe so distant that the light we see from them is billions -- with a "b" -- of years old. How do astronomers know this? How can they tell how far away these distant objects are, and how long their cast-off wavelengths have taken to arrive at our telescopes?

In the video below, astronomer Olivia Johnson of the University of Nottingham explains the different the three techniques (parallax, standard candles, and redshift) that scientists use for taking astronomical measurements. "What's most incredible to me," she says, "is how all these measurements build on each other." And while that may be incredible in its own way, it's got nothing on the vastness of the universe we're measuring -- and the pictures we have of it.



Via @openculture.

Presented by

Rebecca J. Rosen is a senior editor at The Atlantic, where she oversees the Business Channel. She was previously an associate editor at The Wilson Quarterly.

Join the Discussion

After you comment, click Post. If you’re not already logged in you will be asked to log in or register with Disqus.

Please note that The Atlantic's account system is separate from our commenting system. To log in or register with The Atlantic, use the Sign In button at the top of every page.

blog comments powered by Disqus

Video

Does This Child Need Marijuana?

Inside a family's fight to use marijuana oils to treat epilepsy

Video

A Miniature 1950s Utopia

A reclusive artist built this idealized suburb to grapple with his painful childhood memories.

Video

Why Principals Matter

Nadia Lopez didn't think anybody cared about her school. Then the Internet heard her story.

Video

A History of Contraception

In the 16th century, men used linen condoms laced shut with ribbons.

Video

'A Music That Has No End'

In Spain, a flamenco guitarist hustles to make a modest living.

More in Technology

Just In