Has JWST shown that dark matter doesn’t exist?

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We don’t yet understand the early Universe. And that’s not surprising because for a long time we weren’t able to observe the distant Universe, because telescopes couldn’t see that far. That is until the James Webb Space Telescope, which has now allowed us to see galaxies at greater distances than ever before, and those galaxies are confusing us. Which is not surprising since all our models were extrapolated from what we’d seen with the Hubble Space Telescope in the nearby Universe. So because we’re still learning about the early Universe, there’s been lots of discussion in research articles about what could explain what we’ve seen, with lots of ideas raised. One that’s been highlighted this past month is in a research paper from McGaugh and collaborators which focussed on the “over massive” galaxies that JWST has found, that I’ve covered on this channel before including their discovery, and some possible explanations for them. Now McGaugh and collaborators have another possible explanation that these galaxies were predicted by an alternative theory of gravity, known as MOND, that doesn’t need dark matter to explain the Universe...

00:00 Introduction
02:14 AD | Novium Hoverpens
03:57 A recap of JWST's "overmassive" galaxies problem
09:23 What is MOND?
13:22 What are McGaugh and collaborators claiming?
16:59 What are the caveats and implications for this result?
23:42 Bloopers

Video filmed on a Sony ⍺7 IV

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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]

For those who didn't watch until the end: You can’t just take any one of these plots from McGaugh and collaborators out of context and jump to "JWST falsifying dark matter". We don’t have enough evidence to claim that, at least not yet. MOND is actively being researched in universities and institutions around the world; it is not something that is being swept under the rug or ignored. MOND is a hypothesis that needs more work as it currently fails to explain some observations of the universe. Our currently accepted model is λ-CDM (using Einstein's theory of general relativity to explain gravity) because it can explain more of our observations of the Universe than any other model we have.

[slzckboy]

No sweeping, biased over simplified sensationalist conclusion drawn here, just the facts born from observation. Delivered with infectious passion. My thanks.

[taiho]

I'm just very appreciative of Dr. Becky's pedagogical skills. Not just that she teaches with such clarity and ardor; even little things like the way she spells out her outline for the lesson before she begins. Every teacher should do this...

[mikeytrw]

This, ladies and gentlemen is proper science communication.Thank you Dr Becky.

[mattzobian]

Thank you Dr Becky! Instead of sensationalizing the findings and jumping to conclusions, you point out the uncertainties and next questions that are raised. You do us non-scientists a great service!

[MegamanXGold]

Sabine Hossenfelder put out a video (that I likely grossely misinterpreted as) saying MOND is the thing now, and then Dr. Becky saves the day by pointing out the most scientific answer: "We dunno yet." That's a great thing and I'm here for it. I love the perspectives and interpretations of the data and research. Great video!

[n.butyllithium]

Maybe dark matter is just hiding. If i had 85% of the mass of all matter i'd be pretty self conscious of my weight too.

[forghy]

She in a class of her own when it comes to presenting these highly technical papers to the general public.
Truly compelling and captivating.

[danielwoods]

As a data analyst I found this really fascinating, watching you pick apart those very dense charts. It's so easy for a weird chart axis, or a lack of knowledge about where a benchmark comes from, to completely mess up your understanding of what a chart is telling you. I would never have known the context about the TNG models and the fitting of models to Hubble observation. I didn't even notice the change in the cosmic age axis. Also, unrelated but I just love seeing cool scifi-sounding terms like "protogalactic fragments" 😁. Anyway, just wanted to say this is my favourite kind of video that you do - listening to actual expertise from an actual expert.

[njg]

I subscribe to ~200 YouTube channels, most of them lapsed. The time elapsed between my receiving notification of, and clicking on, a newly posted video is the shortest for your channel – almost instantaneous. Keep up the awesome work!

[jacksquiggle]

Great video. Thank you. Also thanks to McGraugh et al.
You have done a great job of showing how complicated and interwoven things get when necessary assumptions are used. No soundbites here (other than 'it's really exciting'). And I particularly like your conclusion: Not 'which theory is correct', but 'which theory supports the observations best.'
Excellent.

[jasongacek]

Sooo grateful to be able to listen to your views. There are so many posts that make extravagant claims about new research with eye catching headlines to draw in viewers (Like ‘JWST proves scientists have been wrong all along’) and similar. THANK YOU:-)

[francretief]

I would love to hear your take on Neil Turok's theory. His theory does not require the definition of new particles to merge quantum mechanics and relativity. Also, dark matter is explained by a flavour of Neutrinos.

[gilson]

wow, this video is probably the best piece of science communication media i've seen all year in terms of clarity and presentation. your work is truly astounding!!

[markhuebner]

Go Dr Becky, go! This is the most amazingly comprehensive collection of all of the current data applied to all of the current models that I have ever seen! Thank you!

[ZoeyZwee]

It is genuinely cool to me the way you talk about research results and interpretations in a way that is
1. Digestible to a non-expert like me
2. Exciting and compelling
3. Deeply imbued with the scientific method

I feel like its such a hard balance to strike, especially getting that excitement aspect while paying full respect to the way evidence-based science actually goes down in practice

[noamchai]

This channel is the best Astro seminar I’ve been in, and I have a phd in physics (in hep). Learning a lot from your videos, thank you for your clear and deep explanations!

[DakotALoopeR]

These are the kinds of videos that i subscribed to you for. Thank you so much for sharing your years of experience and taking the time to explain things. The sensationalism in much of my science feed that I used to love has really discouraged my willingness to watch a lot of science communicators lately.

[echobucket]

The way I understood it, "Dark Matter" was just a placeholder for "There's something we don't understand here".

[timothytaylor]

What a wonderful explanation. I was so frustrated with all the panic and felt that in time we would begin to understand what was really going on in the early universe! Your coverage of the assumptions being made in interpreting the data and the complexity that causes in our interpretations. And your detailing of other factors that could lead us to misinterpret these early galleries as over massive: incorrect distribution of stars, unusual about of massive bright stars, or light from the effects of a growing black hole at the center of the galaxy. All new information to me although I’ve done a lot of reading it this area. Just a marvelous podcast. So very informative. Also love the part about MOD as an alternative answer. Just awesome!❤