Dark Matter Has a Problem. So Does MOND.

For 50 years I taught my students that dark matter surrounds the Milky Way in a giant halo, or that Newton’s laws break down at low accelerations. The Gaia satellite just measured something that makes both of those answers uncomfortable. Subscribe if you want science with evidence, not speculation. Gaia has measured over a billion stars. What its third data release shows is that the outer rotation curve of our own galaxy appears to decline in a Keplerian fashion. That should not happen if a dark matter halo is doing what we think it does. It also should not happen if MOND is right, because MOND produces flat curves for isolated galaxies. Both camps predicted something flatter. Neither got it. I walk you through the physics from Kepler to Vera Rubin to Gaia DR3, show you why systematic errors from asymmetric drift, the Large Magellanic Cloud, and the Sagittarius dwarf galaxy matter enormously before anyone draws a conclusion, and lay out the three scenarios that still survive. The most interesting question here is not which side lost. It is why both sides were expecting the wrong curve from our own galaxy. What you’ll hear: -Why the neutrino technically counts as dark matter and why that still leaves most of the problem unsolved -What Kepler’s first law of fatherhood has to do with galactic dynamics -Why Stacy McGaugh and Mordehai Milgrom might be celebrating too soon -What Cepheids, stellar streams, and globular clusters could tell us that Gaia cannot -Whether the Milky Way is too messy to ever give us a clean answer “The question is not which camp won, but why we were both expecting the wrong curve.” — Brian Keating CHAPTERS 00:00 Two solutions. One problem. Neither wins. 02:12 What Vera Rubin actually found 03:18 We're inside the galaxy. That's the problem. 04:24 The asymmetric drift problem 05:04 What Gaia DR3 actually shows 06:34 Why the mass estimate is model-dependent 08:04 MOND: no radius, no problem. Until now. 08:56 Gaia may be saying both sides are wrong 09:24 Flaws lead to new laws 10:22 LMC, Sagittarius, and the galactic warp 12:28 Three viable explanations 12:42 Dark matter adjusts. MOND adjusts. But is that enough? 13:14 What could settle this 14:04 Are we expecting the wrong curve? Get the transcript, fascinating bonus content, and my Monday M.A.G.I.C. Message: https://briankeating.com/yt Have a .edu email and live in the USA? You automatically win a meteorite: https://BrianKeating.com/edu Subscribe: https://www.youtube.com/DrBrianKeating?sub_confirmation=1 Support Into the Impossible on Patreon, get my weekly M.A.G.I.C. Message, unfiltered bonus content, and live monthly Office Hours with me: https://www.patreon.com/drbriankeating Join this channel for perks, monthly Office Hours, and your name in the Member Roster at the end of every episode: https://www.youtube.com/channel/UCmXH_moPhfkqCk6S3b9RWuw/join Related episodes: Stacy McGaugh episode: https://www.youtube.com/watch?v=NnpyFk2WlME My books: Losing the Nobel Prize (memoir): http://amzn.to/2sa5UpA Think Like a Nobel Prize Winner: https://a.co/d/03ezQFu Focus Like a Nobel Prize Winner: https://a.co/d/hi50U9U Galileo’s Dialogue (first-ever audiobook): https://a.co/d/iZPi9Un Twitter/X: https://x.com/BrianKeating Substack: https://briankeating.substack.com Blog: https://briankeating.com/blog Audio-only: https://briankeating.com/podcast #darkmatter #MOND #MilkyWay #cosmology #briankeating #intotheimpossible #physics Learn more about your ad choices. Visit megaphone.fm/adchoices