Uploaded July 2026 | Updated September 2026, 2 weeks ago
Instead they argue that dark energy is changing, and that the Universe is decelerating. These models of the Universe where the accelerated expansion rate is changing have been coming up a lot lately, the DESI survey for example have found evidence for it looking at the large scale structure of the Universe, which I’ve covered on my channel before. But they concluded that the acceleration rate is slowing down, but it's still accelerating. A result Son and collaborators claim is because the supernova data they added had this age-bias.
They claim that the younger galaxy-fainter supernova effect leads to a 0.16 bias in the brightness of the supernova measured, and you end up with a statistically significant difference with what’s predicted by our current best model of the Universe.
So here’s the key plot - on the horizontal axis you’ve got age of the Universe, and on the vertical the rate of acceleration of the Universe - our best current model is shown by the black line, very clearly accelerating today. Then you’ve got three other lines, all of which use the DESI large scale structure data, that’s independent of the supernovae. The green shows the result from the original DESI paper, combining the large scale structure with supernova data uncorrected for age bias, which gives a slower accelerating Universe, the blue line if you don’t include any supernova data at all, and the red line the supernova data corrected for the age-bias by Son and collaborators, both of which give a currently decelerating Universe.
Video filmed on a Sony ⍺7 IV
Video edited by Martino Gasparrini: martino.freelance@gmail.com
Video produced by Marina Hui & Dr Becky Smethurst
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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!
---
👩🏽💻 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.
drbecky.uk.com
Instead they argue that dark energy is changing, and that the Universe is decelerating. These models of the Universe where the accelerated expansion rate is changing have been coming up a lot lately, the DESI survey for example have found evidence for it looking at the large scale structure of the Universe, which I’ve covered on my channel before. But they concluded that the acceleration rate is slowing down, but it's still accelerating. A result Son and collaborators claim is because the supernova data they added had this age-bias.
They claim that the younger galaxy-fainter supernova effect leads to a 0.16 bias in the brightness of the supernova measured, and you end up with a statistically significant difference with what’s predicted by our current best model of the Universe.
So here’s the key plot - on the horizontal axis you’ve got age of the Universe, and on the vertical the rate of acceleration of the Universe - our best current model is shown by the black line, very clearly accelerating today. Then you’ve got three other lines, all of which use the DESI large scale structure data, that’s independent of the supernovae. The green shows the result from the original DESI paper, combining the large scale structure with supernova data uncorrected for age bias, which gives a slower accelerating Universe, the blue line if you don’t include any supernova data at all, and the red line the supernova data corrected for the age-bias by Son and collaborators, both of which give a currently decelerating Universe.
Video filmed on a Sony ⍺7 IV
Video edited by Martino Gasparrini: martino.freelance@gmail.com
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!): 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. 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
