Uploaded April 2026 | Updated September 2026, 2 weeks ago
AD - To try everything Brilliant has to offer for free for 30 days visit brilliant.org/DrBecky and you'll also get 20% off an annual premium subscription which gives you unlimited daily access to Brilliant. | Nothing can travel faster than the speed of light. That is one of the most fundamental laws of all of physics. And yet… right now, the Universe appears to be expanding faster than that. Because space itself is expanding, when we look out at distant galaxies they appear to be moving away from us at faster than the speed of light, what’s known as “superluminal” motion. But Einstein famously showed that nothing can travel faster than light at 300,000km/s in his theory of relativity. It is a speed limit that applies across the entire Universe.
At first, this seems like a paradox with a fundamental law of physics somehow getting broken here, but rather counter-intuitively it’s not. Because the key to this isn’t about things moving through space…it’s about what space itself is doing. And even asking this question “of is the universe expanding faster than the speed of light” is a bit of a moot point, because the expansion technically doesn’t have a traditional “speed” either, it’s like asking am I heavier than I am tall? So in this video we're going to dive into this cosmic loophole that allows the expansion of the Universe to appear to outrun light itself…
Hubble (1929) - pnas.org/doi/full/10.1073/pnas.15.3.168
Bunker et al. (2023; JWST observations of GN-z11) - arxiv.org/pdf/2302.07256
Every most distant galaxy known | Record Breakers - youtube.com/watch?v=nkYeHYDneHU
Why can’t anything go faster than the speed of light? - youtube.com/watch?v=jRLNVvsxfFo
If the Universe is expanding where is the centre? - youtube.com/watch?v=IEtPy0o8i0M
00:00 Introduction
01:42 Why the galaxies themselves aren’t breaking the speed of light
05:15 Why the expansion of space doesn’t have a “speed limit”
10:43 Bloopers
Video filmed on a Sony ⍺7 IV
Video edited by Martino Gasparrini: fiverr.com/mgs_editing
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📚 My 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 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
AD - To try everything Brilliant has to offer for free for 30 days visit brilliant.org/DrBecky and you'll also get 20% off an annual premium subscription which gives you unlimited daily access to Brilliant. | Nothing can travel faster than the speed of light. That is one of the most fundamental laws of all of physics. And yet… right now, the Universe appears to be expanding faster than that. Because space itself is expanding, when we look out at distant galaxies they appear to be moving away from us at faster than the speed of light, what’s known as “superluminal” motion. But Einstein famously showed that nothing can travel faster than light at 300,000km/s in his theory of relativity. It is a speed limit that applies across the entire Universe.
At first, this seems like a paradox with a fundamental law of physics somehow getting broken here, but rather counter-intuitively it’s not. Because the key to this isn’t about things moving through space…it’s about what space itself is doing. And even asking this question “of is the universe expanding faster than the speed of light” is a bit of a moot point, because the expansion technically doesn’t have a traditional “speed” either, it’s like asking am I heavier than I am tall? So in this video we're going to dive into this cosmic loophole that allows the expansion of the Universe to appear to outrun light itself…
Hubble (1929) - pnas.org/doi/full/10.1073/pnas.15.3.168
Bunker et al. (2023; JWST observations of GN-z11) - arxiv.org/pdf/2302.07256
Every most distant galaxy known | Record Breakers - youtube.com/watch?v=nkYeHYDneHU
Why can’t anything go faster than the speed of light? - youtube.com/watch?v=jRLNVvsxfFo
If the Universe is expanding where is the centre? - youtube.com/watch?v=IEtPy0o8i0M
00:00 Introduction
01:42 Why the galaxies themselves aren’t breaking the speed of light
05:15 Why the expansion of space doesn’t have a “speed limit”
10:43 Bloopers
Video filmed on a Sony ⍺7 IV
Video edited by Martino Gasparrini: fiverr.com/mgs_editing
---
📚 My book, "A Brief History of Black Holes", out NOW in hardback, paperback, e-book and audiobook (which I narrated myself!): lnk.to/DrBecky
---
👕 My 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
