---
title: 'Physicists Rethink Dark Matter. But...'
source: 'https://youtube.com/watch?v=Wdf5_vad9gM'
video_id: 'Wdf5_vad9gM'
date: 2026-08-04
duration_sec: 380
---

# Physicists Rethink Dark Matter. But...

> Source: [Physicists Rethink Dark Matter. But...](https://youtube.com/watch?v=Wdf5_vad9gM)

## Summary

The video discusses the current state of dark matter research, highlighting that despite decades of effort, physicists have not confirmed the existence of dark matter particles. The simple dark matter model has failed to match observations, leading to a proliferation of increasingly complex and speculative theories. The speaker criticizes this trend as unscientific and calls for a systematic search for the simplest explanation.

### Key Points

- **Dark Matter's Unconfirmed Existence** [00:00] — Physicists believe 80% of the universe's matter is dark matter, but they have not been able to measure a single particle, leaving its existence unconfirmed.
- **Dark Matter as a Scientific Idea** [00:25] — Dark matter is criticized as unscientific because it involves making up invisible stuff to fit observations, but it can be justified if the explanation is simple and yields many observable consequences.
- **Original Dark Matter Model** [01:10] — Originally, dark matter was defined as something that doesn't interact with light and is described only by its energy density without pressure, with just one parameter.
- **Observations Contradict Predictions** [01:36] — The simple dark matter model fails to predict galaxy formation: big galaxies have fewer small satellites, cores are less dense, galaxies form too fast, and size correlates with brightness unexpectedly.
- **Proliferation of Complex Models** [02:21] — In response, astrophysicists have made models more complicated, leading to weekly headlines about new dark matter ideas, such as dark sectors, self-interacting dark matter, and exotic particles.
- **Recent Arxiv Listings** [03:17] — The speaker lists recent arxiv papers with 'dark sector' keyword, including primordial black holes, massive vector sectors, dark photons, and spin-3/2 dark matter, calling them 'bullshit' and not proper science.
- **Comparison to Particle Physics** [04:09] — The speaker compares this to the nonsense theory-production in high-energy particle physics two decades ago, noting that people moved to astrophysics but didn't learn from past mistakes.
- **Call for Systematic Approach** [04:35] — The speaker advises astrophysicists to collect all data and look for the simplest explanation, which will likely be a combination of cold dark matter and modified gravity, but no one wants to pursue that path.

### Conclusion

The video concludes that while astrophysicists are rethinking dark matter, the result is that it makes even less sense, and science needs problem solvers to systematically find the simplest explanation.

## Transcript

Physicists believe that 80% of the matter in  the universe is ‘dark matter’ that we can’t   see. But despite decades of trying to measure  even a single one of the dark matter particles,  
they haven’t been able to confirm that this  matter really exists. In the past years,   physicists have been rethinking the dark matter  idea… but not in the way you might expect.
Dark matter has made physics a laughingstock  because it doesn’t seem like a scientific idea.   Hey, we have these observations that we don’t  understand, let’s just make up some invisible   stuff so that the maths works out! In every-day  circumstances making up invisible stuff to  
explain observations you don’t understand  is a fast track to psychiatry. However,   in science it can be justified provided that  the explanation is simple. Because if you can   calculate a lot of observable consequences  from a few assumptions that is good science.
And dark matter used to be such a simple,  good scientific explanation. That’s because   for astrophysicists “dark matter” doesn’t just  mean invisible stuff, it means very specifically  
something that doesn’t interact with light and  that is fully described by its energy density,   without pressure. Dark matter in its original form  really only had this one parameter, the initial  
energy density, and then all the rest should  have followed from that by the laws of gravity. Problem is that this didn’t work.  The observations just didn’t comply,   and the more observations astrophysicists  gathered the less it was working. You see,  
if you stick with the simple dark matter model,  that tells you what galaxies should look like   and how they form as matter in the universe  clumps. This is because there is so much more   dark matter than normal matter, that the dark  matter totally dominates what is happening.
But the predictions from the simple dark matter  just don’t fit to observations. Big galaxies seem   to have fewer small galaxies around them than  predicted, the density in galactic cores isn’t  
as high as predicted, galaxies form faster than  expected, and their size is correlated with the   brightness which really shouldn’t be the case.  There are new problems popping up each month,   like this case that just doesn’t want  to fit into the simple dark matter mode.
So what have astrophysicists done in response to  these observations? They have made the models more   complicated, and they have made many, many  of these models. This is why there are now  
several headlines each week about some new dark  matter ideas. “A New Theory of Dark Matter Could   Solve Three Cosmic Mysteries,” or “Could dark  matter be made of black holes from a different   universe?” or “Scientists Are Pretty Sure They  Found a Portal to the Fifth Dimension” , that  
portal being dark matter. Or “We still can't  see dark matter. But what if we can hear it?”   These are all headlines about increasingly  obscure and complicated dark matter models. The one big trend has been to go from  one dark matter particle to an entire  
“dark sector” of multiple particles, sometimes  these are literally hundreds. The other trend   has been to give the dark matter interactions,  this is known as self-interacting dark matter.
Just have a look at these recent arxiv  posts with the keyword “dark sector”.   Primordial black holes coupled to a dark sector,  a massive vector sector, dark sector antibaryons,  
a massive dark photon and dark matter particles of  spin up to 1, Higgs portal, heavy neutral leptons,   and heavy QCD axion models, Decaying spin-3/2  dark matter, two scalar fields, an anisotropic  
spinor field, a sequestered dark sector. And  those are just the listings FROM THE PAST WEEK! These papers are all a 10 out of 10 on  the bullshit meter. Oh, you might say,  
that’s unkind. Maybe it is. But this is not proper  science. These are people producing papers with   bullshit theories that they fumbled together so  that they fit observations and can’t be ruled out.
It’s no coincidence that this is the same nonsense  theory-production which happened two decades ago   in high energy particle physics, because people  left particle physics and now do astrophysics,  
but it’s the same damn thing. They  have not learned anything. Instead,   they complain about me when I point out  they get paid for producing bullshit papers.
Why am I telling you about this? It’s so that  you know why I don’t talk about the papers that   these headlines are about. They have nothing to  do with reality. There’s nothing interesting to   find there. What astrophysicists should do is  to collect all data and look for the SIMPLEST  
explanation that explains it, systematically. We  already know that this will be a combination of   cold dark matter and modified gravity. But  that’s the path no one wants to go down.
So, yes, astrophysicists  are rethinking dark matter,   but the result is that now  it makes even less sense. Science needs problem solvers, people like  you. If you want to turn your talent into  
hands-on practical knowledge, I recommend that you  check out Brilliant. Brilliant offers interactive   courses on topics in science, computer science,  and mathematics. Let you build up your knowledge  
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explains how computers really work. They also have  super useful courses on artificial intelligence   and probability and chance. The courses on  Brilliant are so well done. They really click  
into my brain. Sounds good. I hope it does. You  can try Brilliant for free for a full 30 days.   And if you use my link, brilliant.org/sabine  or scan the QR code, you'll get 20% off the  
annual premium subscription with unlimited  access. Thanks for watching. See you tomorrow.