Why doesn’t dark matter collapse into black holes? @DrBecky

Uploaded March 2026 | Updated September 2026, 2 weeks ago

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Why doesn’t dark matter collapse? Think about it, gravity pulls on it. There’s a huge amount of it; outweighing all the normal matter in the Universe. So why doesn’t it form dark stars? Dark black holes? Or entire dark galaxies? Instead, it just sits there… in enormous, fuzzy clouds around galaxies. And that’s weird. Because normal matter doesn’t stay fuzzy, it collapses under its own gravity. It makes planets. It makes stars. It makes black holes. And it was after my last video about whether the Milky Way’s centre could be a dark matter cloud instead of a supermassive black hole, many of you asked: "if the dark matter cloud has the same mass, why doesn’t it just collapse?" So what is dark matter doing differently to normal matter...

Similar questions but different:
Is dark matter made of lots of little black holes? (Instead of a particle) - youtube.com/watch?v=d0wV5frSb6s
Once a black hole forms from normal matter, can dark matter then fall in? - youtube.com/watch?v=9Qis5VDOd18
The first evidence for a black hole containing some dark matter - youtube.com/watch?v=QeNspAwdgRY

00:00 Introduction
02:40 Why normal matter collapses under gravity in the first place
06:56 The crucial reason why dark matter can't
10:01 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

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Why doesn’t dark matter collapse into black holes?

$Did we find LIFE on Mars 50 years ago? | The Viking Controversy AD | Go to https://ground.news/drbecky to stay fully informed with the latest Space and Science news. Save 40% off the Vantage plan through my link for unlimited access. It would take a near miracle for there not to be life on Mars. Mars and Earth have been “swapping spit” for billions of years; anytime either planet is hit by comets or asteroids, some material gets ejected into space, with a tiny fraction of that material eventually landing on the other planet. If any of Earth’s microbes happen to have been hitch-hiking in that material, then you’ve got potential life on Mars. And we know that life is capable of surviving both the vacuum of space, and a simulated Martian environment in a lab. And we know that Mars didn’t used to be the dry, arid world it is today. Water once flowed on Mars back before it lost its atmosphere to space. And yet we still haven’t found any direct evidence for life on Mars. Or have we? Because 50 years ago this month, one of the experiments on NASA’s Viking lander that was designed to search for signs of life returned a positive result. It’s just that other experiments on Viking returned a negative result. The next few years saw arguments go back and forth in the scientific research papers, could the results be explained by biology or just chemistry, all asking the same question: is there life on Mars? In this video, we are going to dive into this question! Papers mentioned: Biemann et al. (1976) - Paywall - https://www.science.org/doi/10.1126/science.194.4260.72 Horowitz, Hobby & Hubbard (1977) - Paywall - https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/JS082i028p04659 Klein et al. (1976) - Paywall - https://www.science.org/doi/10.1126/science.194.4260.99 Levin & Straat (1976a) - https://link.springer.com/article/10.1007/BF00926948 Levin & Straat (1976b) - Paywall - https://www.science.org/doi/10.1126/science.194.4271.1322 Levin & Straat (1981) - Paywall - https://ntrs.nasa.gov/citations/19810053555 Levin & Straat (2016) - https://pmc.ncbi.nlm.nih.gov/articles/PMC6445182/ Oyama & Berdaahl (1977) - Paywall - https://agupubs.onlinelibrary.wiley.com/doi/epdf/10.1029/JS082i028p04669 00:00 - Introduction 03:49 - I - What were the Viking landers? 07:06 - II - Did Viking find evidence for life on Mars in the 1970s? 13:34 - III - Why the interpretation of the results was so controversial 15:45 - IV - Have we found any evidence for life on Mars since Viking? 20:02 - Bloopers 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!): 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 🔔 Dont forget to subscribe and click the little bell icon to be notified when I post a new video! 👩🏽‍💻 Im 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 dont know. If youve ever wondered about something in space and couldnt 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$

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$Why is equilux not on equinox? #shorts We did it we made it through the dark, cold winter and equinox is right around the corner. The day with equal daytime and nighttime, except that’s not quite true. Equal day and night is known as equilux, not equinox, and usually we don’t quite have equal day and night on the equinox. So what actually is the difference? The equinox marks the switch between which hemisphere is pointing towards the Sun, when the Earth’s axis is at 90 degrees to its orbit around the Sun. So technically that should give us equal day and night if everything is perfectly aligned like that, equilux should be on the same day as the equinox. The reason it’s not is because Earth has an atmosphere, that changes the path of Sunlight through refraction. So much that when you watch the sunset, the sun is technically already below the horizon. But you can still see it because the light is bent round the atmosphere, making it appear like the Sun is higher than it is. What that means is that equilux, with a 12 hour day happens a few days earlier than the equinox when the sun crosses the celestial equator. So while the equinox is on the 20th March this year, here in Oxford, our equilux happens around the 17th and 18th March. 👩🏽‍💻 Im Dr. Becky Smethurst, an astrophysicist at the University of Oxford (Christ Church). I love making videos about black holes, cosmology, dark matter, the early universe, the James Webb Space Telescope, and the biggest unsolved mysteries in astrophysics. I like to focus on how we know things, not just what we know. And especially, the things we still dont know. If youve ever wondered about something in space and couldnt 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$

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