MORE evidence AGAINST dark matter? | What does the GAIA data actually show?

A new research study was published this month claiming to have found smoking-gun evidence for an alternate theory of gravity, called MOND, that doesn’t need dark matter to explain our observations of the Universe. They did the same test that three other research studies have done in the last couple of years, using the same data from the GAIA mission, and somehow all 4 papers have found different results. Some in favour of MOND, and some in favour of our typical theory of gravity: Einstein’s theory of General Relativity. So what is going on here?

00:00 - Introduction
01:10 - What is this alternate theory of gravity, MOND?
03:58 - How do you use binary stars in GAIA data to test MOND?
07:29 - What results have been found doing this test?
10:29 - Same test, different results - what next? Bayesian statistics
11:42 - Some insider gossip
13:01 - Outro
13:34 - 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]

A HUGE thank you to my colleague Harry Desmond (Senior Research Fellow, ICG), who has become my go-to for chats about this field of modified gravity and who helped me understand the context of this new research paper in the field.

[Scott-.]

I saw this paper pop up in science news and thought to myself "I'll wait for Dr. Becky to do a video on this, I bet the headlines is sensational and there's probably some issue with the paper"

My trust in you was rewarded, thanks dor the breakdown Dr. Becky!

[junkerzn]

It absolutely cannot be 10 sigma with so few data points shown on that graph. Not only because the scatter indicates massive issues with data integrity (too many unknowns), but also because there are simply not enough data points on the plot to make up for the massive scatter in the data. Obviously what has to happen to resolve this issue is to come up with a way to measure the unknowns so the data can be tightened up. Until that happens, no amount of statistical analysis is going to right this ship. These papers are showcasing a classic, classic mistake made by researchers trying way too hard to squeeze something definitive out of spaghetti.

[jasnarmstrng]

Science commentary done right for the masses; much appreciated, Dr. B!

[PopeGoliath]

With data that messy it's no wonder at all that statisticians were able to massage it to fit four different theories.

[derekwood]

Thank you Dr Becky and I totally agree with your skepticism. The trouble with saying "you can just average the data" to get a result.. is that you might have more of one angle of inclination or eccentricity that will bias the results. You might also have "split lots" (production engineering term).. That's when you have two seperate statistical sets (with different averages and spreads) sitting on top of one another, depending on the ratio of type A/B your average will shift.. it's why I'm extremely dubious about pushing data substantially beyond the accuracy of the initial data in a scenario like this, only when you know you've got just one class of data can you start pushing averages. I don't buy it yet.

[john-orcf]

Looking at your scatter graphs reminded me of the analysis we did with Pageous satellite date back in the mid-60’s. The principal investigator on the project took the raw data, threw out the data points he “considered” wrong, drew a straight line through the rest and voila, we had a nice linear answer! We recorded the noisy photomultiplier data on a strip chart along with timing pulses from WWV and since I was the only one on the team who knew Morse code, I got to interpret the PMT timing data. Ah, the good olde days!

[MichaelSiegel]

I remain skeptical. MOND has always been a bit ad hoc, especially after the Bullet Cluster results made it impossible for even MOND to function without some amount of dark matter.

[goalieben]

I suck at math, so a lot of the deep dive into these topics goes over my head, but even as a layperson, the idea of dark matter has always rubbed me the wrong way. It feels to me like we're probably just wrong about something.

Bottom line: I love listening to you explain things.

[Andrey-ilrh]

I just discovered your channel through this video and instantly subscribed. Your way of presenting the information is very engaging. I wish physics and mathematic fields had more people like you who could not only understand the complexity but also docompose it into highly digestible form for those not so deep in the field. Well done ❤

[steve]

Dr Becky! Thank you so much for your videos, you have inspired so many people including myself to realize that their interest in Space and Astrophysics can be more than just that. I recently accepted a job working on a Telescope network at a university while also participating in research as an undergraduate at my university. Your channel has shown to so many people that fundamental questions that we have about Space and Time that strike out at us so intrinsically can be more than just a hobby, and I want to thank you for that and I look forward to more of your videos.

[timothyodonnell]

Dr. Becky- thank you for taking the time to explain the paper and the context in easy to understand, plain English. You are a credit to your profession!

[Retinetin]

Hi Dr. Becky! I actually just read an article that sounded very similar but had yet of course ANOTHER theory, but it's a bit different than the other papers. They actually specifically call out and compare MONDian models with theirs because their model fits even better than MOND-like models. Their model uses fractional calculus because they believe that the effects of gravity can have a non local effect. One of the only ways we can model this mathematically is with fractional calculus, because unlike normal calculus, a change in the graph somewhere actually has an effect on the rest of the graph with fractional calculus. It's extremely intriguing and hope to get your thoughts on it!
DOI: 10.3847/1538-4357/acc8ca

[TacticusPrime]

Hey Dr. Becky, what's the most distant object that GAIA has been able to resolve the direct distance to using parallax? I heard that it was able to view much further than ever before. I haven't seen it posted anywhere.

[Brainfryde]

Should be interesting, but Dark matter theory is also equally extraordinary in terms of its claims. I would never suggest the Newtonian / Einsteinian models are not superior to all other models today, but this is more due to a net value of zero when it comes to high accuracy data. I will wait and see what exactly these two hypothesis end up creating for potential theories where none of the proposed elements are 100% theoretical! Until then, popcorn doesn't hurt anyone :) Thanks for the brilliant translation as always!!

[Jezee]

I'm one of the "Dark matter isn't real" camp. Either way though if it's real, amazing! If not, amazing. Just to have a definitive answer would be game changing! I think it's something missing in the laws or measurements.

[liftpenguin]

I did my bachelor thesis on mond and Zhao was my supervisor! Shoutout H.S

[chrismaggio]

Thanks, Becky. It remains one of the main mysteries that I hope gets solved in my lifetime! Great update.

[alerigali]

Thank you for speaking about MOND. I agree with Sagan about that exceptional claims require extraordinary evidence. Now, for some reason most astrophysicists jumped to believe in matter and energy we cannot measure without ANY evidence other than stronger gravity in most parts of the universe, no small portion of it (+-95% actually )… Looking for it for almost hundred years without anything at this point. I would give MOND and their derivatives more attention now, to put it politely

[SpeakerWiggin]

I'm excited to see that Bayesian Statistics analysis of the data. If it is going to take that long to publish, I have high hopes for the quality of the paper.