Why are we crashing a spacecraft into an asteroid? On this explainer, Neil deGrasse Tyson and Chuck Nice learn about the NASA DART mission and testing Earth’s defense against asteroids with NASA’s first Planetary Defense Officer, Lindley Johnson. How do we stop what happened to the dinosaurs from happening to us? We learn about near-Earth asteroids, their moonlets, and the DART mission’s plan to change an asteroid’s orbit. Discover the asteroid Didymos and it’s moonlet Dimorphos. What is going to happen when the spacecraft makes impact? How do we use physics and orbital ballistics to get the DART spacecraft to the asteroid? Are we prepared for an asteroid headed towards us? Tune in on September 26th at 7:00 pm ET to see the DART spacecraft complete it’s mission at nasa.gov. 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 0:45 - Planetary Defense 2:16 - DART 3:30 - Didymos’s Orbit5:32 - What Could Go Wrong? 7:07 - Didymos’s Moonlet 9:49 - Areas of Uncertainty 11:11 - Impactor Instruments 12:01 - Hitting the Target 13:54 - Lindley Johnson’s Background 14:42 - Asteroid Detection 17:45 - Nemesis 18:56 - Early Deflection 19:50 - Orbital Models 21:15 - Shoemaker-Levy 9 Comet 21:54 - CCD Technology 23:01 - Targeting Earth with Asteroids 24:31 - Time of Impact 24:39 - DART Website 25:21 - Closing Notes