Why do galaxies spin? #shorts

There are trillions of galaxies out there in the Universe, and almost all of them are spinning. Our galaxy of stars the Milky Way is spinning. Andromeda is spinning. And once a galaxy gets its spin, it keeps it. There’s no friction in space to stop it. So what’s going on here? Well for that we have to go back to the beginning. To the early days of the Universe when all there is a hot, dense soup of matter and energy. But crucially, it's not perfectly smooth. There are tiny differences, where some regions are slightly denser than others. Which makes more matter clump there, and slowly but surely gravity pulls in more material from surrounding regions pulling material in and setting it moving. That's the seed of a galaxy’s spin. And it’s in these denser regions that galaxies first start to form, but they’re incredibly messy. Gas is flooding in from all directions. Massive bursts of star formation are driving huge outflows of gas. Everything is turbulent, everything is disrupted. So the spin is there, but it's turbulent and the shape of a galaxy is very irregular. Going from that to the thin, beautiful, spinning spiral galaxies that we’re used to seeing around us today is a kind of settled rotation that takes time. And a lot of it. Billions of years of relative calm for the gas to settle, for the disc of stars to flatten out, for everything to settle down into the structures we recognise today. Video filmed on a Sony ⍺7 IV Video edited by Martino Gasparrini: [email protected] Video produced by Marina Hui & Dr Becky Smethurst --- 📚 My book, "A Brief History of Black Holes", out NOW in hardback, paperback, e-book and audiobook (which I narrated myself!): http://lnk.to/DrBecky --- 👕 My merch, including JWST designs, are available here (with worldwide shipping!): https://dr-becky.teemill.com/ --- 🎧 Royal Astronomical Society Podcast that I co-host: podfollow.com/supermassive --- 🔔 Don't forget to subscribe and click the little bell icon to be notified when I post a new video! --- 👩🏽‍💻 I'm Dr. Becky Smethurst, an astrophysicist at the University of Oxford. I love making videos about science with an unnatural level of enthusiasm. I like to focus on how we know things, not just what we know. And especially, the things we still don't know. If you've ever wondered about something in space and couldn't find an answer online - you can ask me! My day job is to do research into how supermassive black holes can affect the galaxies that they live in. In particular, I look at whether the energy output from the disk of material orbiting around a growing supermassive black hole can stop a galaxy from forming stars. http://drbecky.uk.com