Uploaded January 2025 | Updated September 2026, 2 weeks ago
Try out Surfshark today by heading to surfshark.com/drbecky and you’ll get 4 additional months free on your subscription - 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) - 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) - arxiv.org/pdf/astro-ph/9805201
Fosalba et al. (2003) - arxiv.org/pdf/astro-ph/0307249
Scranton et al. (2003) - arxiv.org/pdf/astro-ph/0307335
Uzan, Clarkson & Ellis (2008) - arxiv.org/pdf/0801.0068
Caldwell & Stebbins (2008) - arxiv.org/pdf/0711.3459
Clifton, Ferreira & Land (2008) - arxiv.org/pdf/0807.1443
Tomita & Inoue (2009) - arxiv.org/pdf/0903.1541
Keenan, Barger & Cowie (2013) - arxiv.org/pdf/1304.2884
Kreisch et al. (2022) - 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: fiverr.com/mgs_editing
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📚 My new book, "A Brief History of Black Holes", out NOW in hardback, paperback, e-book and audiobook (which I narrated myself!): lnk.to/DrBecky
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👕 My new merch, including JWST designs, are available here (with worldwide shipping!): dr-becky.teemill.com
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🎧 Royal Astronomical Society Podcast that I co-host: podfollow.com/supermassive
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🔔 Don't forget to subscribe and click the little bell icon to be notified when I post a new video!
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👩🏽💻 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.
drbecky.uk.com
Try out Surfshark today by heading to surfshark.com/drbecky and you’ll get 4 additional months free on your subscription - 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) - 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) - arxiv.org/pdf/astro-ph/9805201
Fosalba et al. (2003) - arxiv.org/pdf/astro-ph/0307249
Scranton et al. (2003) - arxiv.org/pdf/astro-ph/0307335
Uzan, Clarkson & Ellis (2008) - arxiv.org/pdf/0801.0068
Caldwell & Stebbins (2008) - arxiv.org/pdf/0711.3459
Clifton, Ferreira & Land (2008) - arxiv.org/pdf/0807.1443
Tomita & Inoue (2009) - arxiv.org/pdf/0903.1541
Keenan, Barger & Cowie (2013) - arxiv.org/pdf/1304.2884
Kreisch et al. (2022) - 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: 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!): lnk.to/DrBecky
---
👕 My new merch, including JWST designs, are available here (with worldwide shipping!): 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.
drbecky.uk.com
