The Copernican Principle: the foundation of ALL of cosmology

Head to https://squarespace.com/drbecky to save 10% off your first purchase of a website or domain using code DRBECKY - AD | The Copernican principle states that the Earth is not in a special place in the Universe. Us humans are not privileged observers, we’re seeing the same Universe as everyone else; and the observations we make from Earth are representative observations taken from an average, random position in the Universe. It’s named after Copernicus, the mathematician who put the Sun, and not the Earth in the centre of his mathematical model of the Solar System, who was the first to “demote” Earth from a special place in the Universe. It says there is nothing unique about Earth’s position in space, and that the laws of physics are the same here as anywhere else in the Universe. It is the main philosophical and physical assumption that underlies all of cosmology - the branch of astrophysics which deals with the properties and evolution of the entire Universe - so every model and theory we have about the Universe (from the Big Bang to LambdaCDM) all of them have the Copernican Principle at their foundation. And yet, the Copernican Principle has never been fully proven, because it can’t - it’s a philosophical assumption at heart rather than a fully fledged scientific theory. But we can gather observations of the Universe that help support this massive assumption... Hubble (1929) - https://www.pnas.org/doi/full/10.1073/pnas.15.3.168 Hubble (1929) - https://articles.adsabs.harvard.edu/pdf/1929ApJ....69..103H Riess et al. (1998) - https://arxiv.org/pdf/astro-ph/9805201 Fosalba et al. (2003) - https://arxiv.org/pdf/astro-ph/0307249 Scranton et al. (2003) - https://arxiv.org/pdf/astro-ph/0307335 Uzan, Clarkson & Ellis (2008) - https://arxiv.org/pdf/0801.0068 Caldwell & Stebbins (2008) - https://arxiv.org/pdf/0711.3459 Clifton, Ferreira & Land (2008) - https://arxiv.org/pdf/0807.1443 Tomita & Inoue (2009) - https://arxiv.org/pdf/0903.1541 Keenan, Barger & Cowie (2013) - https://arxiv.org/pdf/1304.2884 Kreisch et al. (2022) - https://arxiv.org/pdf/2107.02304 00:00 Introduction 03:48 Why we can't prove the Copernican Principle 04:58 Evidence in support of the Copernican Principle 09:59 Evidence against the Copernican Principle 13:33 Bloopers Video filmed on a Sony ⍺7 IV Video edited by Martino Gasparrini: https://www.fiverr.com/mgs_editing --- 📚 My new 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 new 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 (Christ Church). 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