Why is the Night Sky Dark? | Neil deGrasse Tyson Explains...

Why is the sky dark at night? On this explainer, Neil deGrasse Tyson and Chuck Nice go over Olbers’ Paradox and why the night’s sky is dark. Hint: it’s not just because it’s nighttime. Why isn’t the entire night’s sky ablaze with stars? We travel back to the early 1800s to discover ​​Heinrich Wilhelm Olbers’ confounding question: if the universe is infinite, shouldn’t every sightline land on a star? We discuss physics and equations for star brightness. If you put the sun three times farther away how much area in the sky does it take up? How did discovering the expanding universe finally help confirm this question? Get the NEW Cosmic Queries book (5/5 ⭐s on Amazon!): https://amzn.to/3dYIEQF Support us on Patreon: https://www.patreon.com/startalkradio FOLLOW or SUBSCRIBE to StarTalk: Twitter: http://twitter.com/startalkradio Facebook: https://www.facebook.com/StarTalk Instagram: https://www.instagram.com/startalk About StarTalk: Science meets pop culture on StarTalk! Astrophysicist & Hayden Planetarium director Neil deGrasse Tyson, his comic co-hosts, guest celebrities & scientists discuss astronomy, physics, and everything else about life in the universe. Keep Looking Up! #StarTalk #NeildeGrasseTyson 0:00 - Introduction 0:52 - Surface Brightness 4:12 - Olber’s Paradox 6:16 - Hubble’s Discovery 7:40 - How Light Travels 10:38 - Closing Notes