Dark Matter Exists. Here's how we know.
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- čas přidán 20. 05. 2024
- Dark matter is 84% of the matter in the universe and it single-handedly explains a lot of stuff: cluster motion, galactic rotation, gravitational lensing, and the CMB. We have piles of irrefutable evidence. Let's go through it, shall we.
Nick Lucid - Host/Writer/Editor/Animator
Vanessa R Bradley - Thumbnail
Eric Aspling - Researcher
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VIDEO ANNOTATIONS/CARDS
Most Galaxies are Moving Faster than Light!
• Most Galaxies are Movi...
The REAL Source of Gravity:
• The REAL source of Gra...
The Oldest Light in the UNIVERSE! (CMB)
• Cosmic Microwave Backg...
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RELATED CZcams VIDEOS
PBS Space Time on Dark Matter:
• Does Dark Matter BREAK...
Crash Course on Dark Matter:
• Dark Matter: Crash Cou...
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LINKS TO COMMENTS
• Current does NOT take ...
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IMAGE CREDITS
Bullet Cluster:
chandra.harvard.edu/photo/200...
Chandra Space Probe:
images.nasa.gov/details-PIA18166
Coma Cluster:
hubblesite.org/contents/media...
Cosmic Microwave Background:
sci.esa.int/s/WLGmGdw
Dark Nebula:
images.nasa.gov/details-GSFC_...
Earth Map (Mollweide):
www.nasa.gov/multimedia/image...
Galatic Rotation:
www.eso.org/public/videos/eso...
Galatic Collision:
hubblesite.org/contents/media...
Gravitational Lensing:
esahubble.org/videos/heic1106a/
Scorpius X-1:
images.nasa.gov/details-PIA18845
Twin Quasar:
esahubble.org/images/potw1403a/
Type 1a Supernova:
svs.gsfc.nasa.gov/13852
People:
digital.archives.caltech.edu/...
photos.aip.org/history-progra...
www.gb.nrao.edu/fgdocs/HI21cm...
photos.aip.org/history-progra...
photos.aip.org/history-progra...
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TIME CODES
00:00 Cold Open
00:35 Fritz Zwicky
01:44 HR Diagrams
02:51 Doppler Redshift
03:58 Virial Theorem
04:29 Zwicky was wrong
05:33 21 cm Hydrogen Line
06:40 X-Ray Astronomy
07:37 Vera Rubin
08:35 Rotation Curves
10:17 Gravitational Lensing
10:48 Bullet Cluster
12:15 Cosmic Micowave Background
13:50 Summary
14:46 Outro
15:08 Featured Comment
While consensus is itself not evidence, it is reached _through_ overwhelming evidence... so consensus represents the existence of that evidence. It's an important indicator of confidence to the general public who doesn't necessarily have the time or energy to learn the evidence. This video presents that evidence (at least some of it) and then states there is consensus based on that evidence. I'm not being unscientific. That's how science works! It's certainly acceptable for an expert in a field to reject consensus based on new evidence and present that evidence to the scientific community for evaluation. But, if you reject consensus outright on principle, then what you're _really_ doing is rejecting science as a whole.
Hi Nick, I really love your teaching style. I don't disagree that consensus is an important part of scientific advancement but I do disagree with the premise that all of the evidence proves that dark matter exists. I would argue that what all this data actually proves is that the standard model is flawed at the most fundamental levels and that consensus in this case is preventing the breakthrough that leads to an actual understanding of the "physics" behind the observations. Cheers
By expanding the definition of Dark Energy to include modified gravity theories, photons have mass below what we can measure folk, micro and or swarms of black hole ideas, and all sorts of minority but serious science camps is how consensus was made. Everyone agrees the effects occur but as the quest to find a particle involved in dark matter keeps failing over decades other approaches although in the minority have gained some steam. Modified Gravity not denying mass is involved it just postulating multipliers of visible mass that we can't measure on earth and this space/time curvature effect does not express in the way we would expect. Maybe not related but serious group is working on ways Back holes can be created without mass in part to solve the fact that galaxies and the size of their supermassive black hole are in a fairly strict ratio which should not be if both only created by matter coming together though gravitational attractions especially when in mergers the combined supermassive black hole loses a decent percentage of it's total mass in Gravity Waves when formed and thus should throw off the ratio of supermassive black hole to mass of combined galaxy but it does not. And Galaxies should run into differing amounts of the great hydrogen clouds of the void.
^ This contains a misconception. That misconception is that dark matter is well defined. I don't blame anyone for thinking so, because even a lot of journals have unreasonably specific definitions as to what it is. But dark matter is not well defined. In terms of intrinsic and extrinsic properties, only 1 extrinsic property about it is known, and that is that it only interacts gravitationally. You can know everything about that one property as much as desired, but that's where all the knowledge is.
It is not known whether dark matter is fundamentally compatible with the standard model, and given how well the standard model applies to pretty much everything else, it seems reasonable to stretch it to its limits before deciding that an entirely new category of science needs to come into existence. It could be something that simply hasn't been found, or it could be something new, no one knows, and the huge gap of knowledge regarding the subject, the logistical challenges of actually being able to find out which, and the amount of technological developments that need to happen before finding out even becomes possible, being able to say whether it should be treated as compatible with the standard model or not isn't something anyone is ready to say
While dark matter seems to exist no one has been able to define what it is. It could be anything, even just an artifact to make calculations work. There's something we call dark matter but we don't know what it is, just what it does to our observations.
Can we at least call it for what it is. Unobserved matter, till we can find sensative enough instruments to correlate the data and maybe even observe something... That might be the antithesis and not the absence of matter.
I love the fact that Nick takes the to explain anything he references. Rather than just throw in terms like 21cm hydrogen with a 'more about that later' caveat (which never arrives), he spends a few minutes explaining. Likewise whenever he refers to any measurement he explains how the measurement was taken. These videos just get better and better. On a sidenote I'd never seen that photo before showing dark matter separated from normal matter and therefore the gravitational lensing. Mind well and truly blown :)
To be clear: the red and blue blobs on the photo of the bullet cluster are an added diagram of the mass distributions; they weren't captured photographically.
@@SimonClarkstone Yes understood thanks. What I meant was knowing that the two matters were separated and being able to see the effect of the dark matter was mindblowing.
Do you have a citation for this comment tho 😂💙
I like taking the to explain too
Great teacher indeed!
Disappointed that the galaxies in the Coma Cluster were only moving "way too fast" and not "fast fast!"
Dang it! Missed opportunity.
I know not the same but there you go
@@rarra Whoa how the heck you write that in?
I thought the exact same thing! Nice to see Nick has declared it a missed opportunity rather than a dead horse because I live for the catch phrases haha.
@@localverse CZcams channel members get special emojis. (At the moment, is the only one I've made. I keep forgetting to make more.)
I love that photo of Zwicky! That fits his description perfectly!
“He is remembered as both a genius and a curmudgeon. One of his favorite insults was to refer to people whom he did not like as "spherical bastards", because, as he explained, they were bastards no matter which way one looked at them.”
That's really good . I may use that myself .
Are you talking about Funtime Fritz Zwickey?
my personal favourite fact about this learned man, that's a sense of humour!
"I'm holding back here because this video is already too long"
No, it's not! Your videos are awesome! They could be half an hour long, and i would be pleased to watch! Keep going with long videos!
Right, I would listen to 16 hours about dark matter
Generally when creators say that, they are referring to the fact that videos longer than about 10 minutes get underpromoted by the algorithm and reach a smaller audience. The longer they get, the less likely they are to get recommended.
@@aroncanapa5796 Random, but can i act on my hobby and recommend you some Science-CZcamsrs?
This is the first time I saw the CMB how it should be shown to non astrophysicist. Very nice!
I didn't realize it was the inside of a sphere projected onto a two dimensional surface until this video and I feel a little sheepish about it, tbh.
@@sadrevolution It's basically the Mollweide projection of the sky sphere. That particular image is from 2012.
So true, that 3d graphical representation really gets the point across
Agree. I figured that it was something like that but this is the first illustration that actually gives the proper perspective and context.
It's like I always knew, but only now I really understand.
What draws me about Nick is that contrary to the traditional approaches, he explains everything from historical contexts.. I don't know I might be alone in this mindset, but I think Historical perspective makes it clear why do we need such considerations in the first place and once one has understood the problem the rest of it is just a piece of cake ..In this approach One thinks through the problem and once they do, nothing seems falling from the sky...
Thanks to Nick and his soulmate
Totally agree with you.
It really makes things more clear.
Agreed, following the macro genesis of knowledge helps the personal micro genesis of it.
Yes
Many textbooks have the historical context included as well! It's just that most students couldn't give a shit about it when learning.
The thing about educational channels like this, is that people have to come here *voluntarily*. So by definition, the consumers of this educational content is biased extremely towards people who *want* to learn, versus the distribution you might get in your standard classroom.
I completely agree too 😀. Otherwise we are just thinking that if Coulumb's Law and Gauss law for Electrostatic are equivalent then why do we study both 😂.
That dark matter separating out from regular matter in the bullet cluster was profound. I don't know yet to what degree but the concept left a strong impression.
I agree that's an elegant idea. Not saying I'm convinced by it but it is beautiful and compelling.
What I don’t get is if dark matter doesn’t interact with the matter of the other galaxy how was it traveling with its galaxy in the first place.
@@DiazJulioMario *⭐MAGIC⭐* (ok probably gravity)
@@DiazJulioMario it doesn't interact with matter, but it does with gravity created by those matter.
The bullet cluster is a statistical outlier and is colliding at relativistic speeds. This should not be considered evidence for dark matter and only evidence of something. Dark matter has major problems. Not least of which is that not a single parameter that follows the inverse Square law actually follows the inverse Square law indefinitely. It's likely that our laws of physics lack the ability to model the truth. Even light emitted from objects in space doesn't follow the inverse Square law indefinitely once you hit 9.6 billion light years light starts to fall off as an inverse proportion instead of an inverse squared proportion. I would bet my life that CERN Collider will not discover a new particle. Scientists claim it will to get more funding and secure their jobs. More likely that the consensus reached among scientists is I want to secure living and want to keep my job. Mond is a simpler model. The only problem with mond is physicists claim anybody can add terms and fine tune the math but the same exact thing has to be done for dark matter. Terms need to be added to the dark matter model that determines the density/distribution of dark matter.
Yes, dark matter exists. But when you ask, "What *is* dark matter?" the only answer anyone can give at this point is, "It's something with mass that we have no other evidence for except that it has to be there for our equations and assumptions about the nature of the universe to match our observations." At this point, we're basically positing, "There exists something and we don't know what it is, but it has this effect which we see." Sort of like inferring the existence of an electrical circuit when you only have the observations that flipping a switch over here causes a light to turn on or off over there, but without being able to see into the wall to know what the circuit actually is.
Currently a lot of research is trying to get a tight enough model so we can test it.
@@brainderp808 how to warp time? i wanna fly
This explanation is also precisely why the video creator is being disingenuous when it comes to the representation of the question does park matter exist, because all of this evidence is only true if our models for gravity are correct. Although it’s a minority opinion, Modified Newtonian gravity is also an answee
Still havent proved it. If its everywhere, you can find it. End of story. And if thats not the end, then you admit a lack of knowledge that prevents dark matter from being taken seriously, BECAUSE YOU CANT FIND IT. Dark matter/ is the biggest scam the scientidic community propogates, all for the FEAR of having to rewrite our knowledge of physics.
@@billjoe5991 perhaps. Modified gravity is another explanation, but it has less predictive power overall than our standard model of gravity so why would we switch to it? Rule number one is never switch to a less powerful predictive model. That's just walking backwards. Not to mention the "modified" part is just kicking the dark matter can down the road.
The break from the bit at 2:00 was cute and made laugh. I love seeing people be happy about silly jokes
It’s okay to be a little early.
Maybe she's into that kinda stuff...
Fast, fast!
@@kevin42
Giggity.
@@thedebatehitman Giggity Giggity
_Alllriiiiiiiiightttttt_
This was like a concise summary of a large part of my astrophysics undergraduate course - and made a lot of definitions and idea so much clearer! Nick, your videos just get better and better...There are so many great moments, but I love the photo you chose for Fritz Zwicky :D) (he was quite a character) and the thumbs up to Vera Rubin...And I am ashamed to say, I don't have a pocket HRD 😄
This video is very convincing in proving that there is a gravitational anomaly resulting in stronger gravitational attraction than currently predicted by general relativity. However I think it's an irrational leap to draw the conclusion and reach a consensus that this inexplicable anomaly is certainly caused by the presence of undiscovered invisible particles.
With that said, the example showing dark matter separating from galaxy matter is somewhat persuasive...
The thing is... that there are galaxies where there is no dark matter and so have no gravitational anomaly.
So somo galaxies, have something with mass, aka matter, that we can't see, aka dark, that is creating a gravitational anomaly that other galaxies do not have, aka dark matter.
Another interesting thing is ... a lot of these discoveries of anomalies were using Newtonian gravitation as their model. Heck, even supercomputer simulations on dark matter to date will only use Newtonian gravitation. So it's a bit of a bold claim saying that these discoveries are all beyond the prediction of general relativity.
@@thenumbernine agreed. Actually it turns out that if you replace the Newtonian model with a GR model in an inhomegenous universe, the back reaction of the gravitational field with itself explains all of these phenomena - including gravitationally bound cluster galaxies. However, our evidence appears to point toward a homogenous universe. So unless that changes, the above wouldn’t be the answer.
Don't know how 16 minutes got passed.
Loved your explanations and how you put the questions in between of the video.
At first glance had thought '16 minutes for dark matter seems long' but learned a lot, was worth it! So glad you went into the history of each step and how we discovered them and decided stuff. Especially how they discovered cold and hot hydrogens then calculated their amounts. One question: How can we measure hydrogen from their emissions of tiny radio waves but not be able to detect exoplanets that way? Is it because the hydrogen clouds are way more massive? Maybe the exposure time would be waaaaaaay too long. Seems we should be able to measure radio waves from large objects in the Oort Cloud that are much closer but I guess even those would dramatically fall off because of inverse square law, so, those might need to be way larger or need crazy long exposure time.
There isn't enough gaseous hydrogen in the atmosphere of an exoplanet for us to notice at interstellar distances. We'd receive a single 21 cm photon very infrequently. The clouds are _huge,_ not only in size but also in mass. There is a lot more hydrogen, so there are a lot more chances for the 21 cm emission.
I had a subject called
"The Nature of Dark Matter" in one semester 😅
@@ScienceAsylum I was thinking about getting a Snickers bar at the convenience store the other day when I changed my mind and bought a Milky Way instead. When I got to the register, I noticed the wrapper said: Milky Way Midnight. I asked the woman behind the counter what that meant and she held up the candy bar and said "The Milky Way is mostly dark chocolate." I didn't think anything of it at the time but later that day I remembered seeing peanut clusters in chocolate and they were moving around kind of fast in the bag, so I looked and wouldn't you know? They were peanut clusters in dark chocolate. I tried to estimate the mass of the chocolate from a distance but it turned out my HR diagram was on the .....Fritz.
@@chriskennedy2846 ?!
The clouds are so huge that, they could be making several thousands(hundreds? Not sure about the order of magnitude here). Stars which could be the size of our sun and larger (smaller).
Planets aren't even comparable at that scale. Some types of cloud are even the size of galaxies
Thank you Nick. Every video is so clear, concise and really helps with grasping all of these concepts. Greatly appreciated.
Once again, the best explanation of a topic on the internet, found right here! Thank you Nick!
This might be the most comprehensive while understandable to non-experts explanation of dark matter I've seen. :)
Thanks. 🙂 It was really important that this video turn out that way.
@@ScienceAsylum If Dark Matter's identity is finally pinpointed, what would be the possible applications if we could collect or produce it in large amounts?
@@_John_P I'm not sure what we could practically do with it. Also, by its very nature, it can't be contained. It just passes right through regular matter.
Let us know when Big-deal-clone starts his own channel! Def supporting that.
It will be a big deal...
@@livedandletdie
One day Nic should deal with it.
Nick, you should be proud of yourself and you should have many more subscribers! Keep doing what you're doing and they will come! Fantastic video with timeline and facts, great visuals. 10/10 teaching material
Nick, you are every time better and better! You summarized inventions that happened during my lifetime, and still I didn't realize their importance until now! Thank you!
I truly hope you realize how comprehensible you have made this subject to the average person. Bravo that is no simple feat. If only more educators had the gift you do.
I love how accessible you make these videos to people who have little or no prior understanding of astrophysics. I have recommended your videos to several HS educators I know. I love your work.
Ur videos are hilarious and so good, plus u explain everything in a nice neat way, u deserve a ton much more subs
Oh wow... that's so cool to know there's so much consensus about it... Also I love the characters you made, like Dark Matter clone, so well represented. Cool video by the way...
Everytime I get a question watching the video, in next second, magically you point out the same question and explains it.
You should know your videos are great.
Dark Matter is like the EA games of the Universe
95% of the content hidden away from the main game and getting a lot of grind and accomplishment to unlock it
Earth is a free user and not purchased any DLCs...once you pay, dark matter unlocks and u can progress on the story line :D
If EA games are dark matter, then World of Tanks is black hole singularity.
Superlative videos and data. I have been teaching/conferences about physics in Belize and Argentina for almost half a century and still learning thanks to you. Cheers from frozen Patagonia!!!
This was super helpful! Thanks for making this intimidating topic of dark matter accessible to curious minds without a background in cosmology or astrophysics ❤
5:28 that graph made me laugh way more than it probably should
😂 I'm glad someone noticed.
@@ScienceAsylum I am sure all the kids noticed it. They have super skills to spot inappropriate stuff even if it is not there sometimes. This one I noticed too, and I am too old for super skills.
The only trouble with this is - Type 1A supernova have recently been proven NOT to be as constant in brightness as we thought... 👍
First off, sources? Second off, we still have other good sources. Due to the Universe expansion we still have a bit of an estimate of distance from how fast stuff is going away from us (we're not seeing true blueshifts for anything farther than some distance)
Yes, but that's a very new discovery. I would be skeptical of any physics announcement that isn't at least a year or two old. It's got to be put through the (scientific) ringer first.
Dear Nick, I've binge-watched during the summer all of your videos and it was a wonderful journey that helped me expand my mind to the wonder that is our cosmos. I really want you to keep it up, so I've just headed over to Patreon to subscribe - the first time I've done this for anyone. But you deserve it! I'm now preparing a list of newbie crazy questions and looking forward to your next videos! Greetings from Greece.
Thanks for your support! 🤓
Late to the show but it's worth the wait! Nick's been the best at simplifying such deep concepts
Thanks! 🤓
Sabine Hossenfelder's youtube channel has a couple of recent videos about problems with the theory of dark matter.
Finally, it was about time you did this vid. Awesome!!
I only found Your channel today, and it’s really entertaining and interesting in the perfect proportions. Subscribed.
This channel just keeps getting better and better. Bravo.
i have been waiting for the BIG DEAL Clone since u posted and was very satisfied with the video too.
Also i like how u have increased the complexity and information in your videos
Thanks. I didn't know I wanted this video from you but I absolutely did. Great ep.
I got interested in the Cosmos because of NDT but Nick helps in breaking it down. You are truly appreciated! Great work!
When the sun would disappear instantly, we wouldn't notice until 8 minutes later. So gravitational fields don't instantly change over larger distances.
When 2 clusters collide, the matter in those clusters slows down. But the gravitational effects of those 2 clusters at larger distances, will continue to move at the same speed, won't they?
So they get ahead of the 2 clusters at large distances. And thus their gravitational lensing effects seem separated from the 2 clusters. At least for a while until they "catch up".
Wouldn't that gravitational delay explain it better than dark matter?
That gravitational delay could explain what we see in rotation speed of galaxies too? Because it seems that all these calculations assume instant gravitational effects at all distances. That doesn't seem correct.
+1
Gravitational waves travel at the speed of light so I would assume that's not the case. At least from my perspective we:
1. Either need to rework our understanding of gravity or at least gravity related to large bodies like galaxies
2. Or we need to see if a low density but very high number of gas particles sprinkled around in galaxies can account for it
3. Or if gravitational influence can create a chain which forms spirals with star systems furthest out traveling faster and farther than the ones inside (as seen in spiral galaxies)
4. Or there are a lot of small black holes inside most galaxies which we cannot see unless other visible masses get attracted toward them which can only happen with large black holes
I don't know if point 3 can hold up with the bullet nebula though
Been a long time follower, and this is my first time commenting. I cannot understate how much I appreciate these videos, Nick’s style of teaching, and his sense of humor. As an electrical engineer, I am definitely part of the target demographic and I am so impressed. I’ve also shared so many Science Asylum videos to others (including my wife). Hands down one of my favorite science channels. Keep up the amazing work!!!❤️🙏👊💥
Thanks! 🤓 Glad you like my work.
Lol, I love the edit cuts in this episode! Also, I think they're a great little micro-break for our learning-brains as we process some humor for a second. Great approach!
Zwicky has always been one of my heros of astronomy/astrophysics and now I have Vera Rubin. Thanks for the enlightenment. Also, I love the t-shirt.
I want to give you props for the Doc Brown imitation/reference! Great job with the video and with your explanations. Whoever is editing deserves some props too. Makes the whole experience very enjoyable
You can't believe how happy it made me to have this notification! I guess I really like your videos ahah!
Fantastic! So well done! Wonderful timeline! Thank you so much!
I could do with a whole series from you just about science history and the timeline. Super interesting stuff!
Thank you! I actually learned something today! I was skeptical about dark matter due to ignorance but this really clarified everything.
Glad I could help! 🤓
Nice video, but I'd make one point: up until now noone's *discovered* dark matter, what they've discovered or observed is *evidence consistent with* a theory of dark matter.
What it actually *is* is as yet unknown.
"Discovered" in this context is basically the same thing, I think. Evidence consistent with a theory of [x] is how most of science operates.
Yep. First they may define dark matter. Yet there are many options of what type of particle it may be....
So if dark matter =?
Then 'dark matter exists" = "? Exists"
? Exists. Its doing a thing very well. Yay for ? we saw what you do...i mean we speculate on what ? is but less what ? kind of does in one large range of a single force
Going beyond 'stuff that could be many things' might stop more critical videos like Sabine's showing their "scientific heresy"
Great video. I've seen the Bullet Cluster used to explain dark matter before, and to me that's the most convincing. We can plainly see with telescopes that there's something there, even when there doesn't appear to be anything at all. It allows us to point to a picture and say "Right here, here it is." It doesn't get more obvious than that.
This channel is so wholesome and informative. Subscribed.
Your simply amazing sir, I wish we had all teachers like who can actually break down these complicated physics concepts to their most basic form in order to edify their immediate audience. And today I feel truly privileged to be part of your audience. Seriously a lot of us only wish to explain these things as well as your do and I'm not saying this to flatter you or anything. And I'm being upfront about this! Your doing a great job, and I sincerely hope that you continue to educate us. Thank you.
Not until this video did I realize that I needed a pocket HR-Diagram for quick reference... Since I don't have one that means I'm not on the main-sequence with astrophysics... and I'll bet they check at the door of astronomy conferences to see if you've got one
Pocket HR-Diagram is handy in Tesco, 20% discount on qualifying items.
In regards to Rubin’s observation and cluster collisions, if dark matter interact through gravity and gravity only, why doesn’t it stack towards the center of galaxies and be bound to them when clusters collision occur?
Because it doesn't interact strongly or weakly even with itself. It's like a neutrino, but worse at interactions other than gravity. Yeah, it's THAT bad.
regular matter would do this _more_ than dark matter because by interacting with other matter, it would slow down so gravity could capture it _more_ easily than it can capture dark matter - akin to how the thin edges of the atmosphere cause the orbits of satellites to decay by slowing them down through drag.
J.F. Fisher I did read recently that Voyager found that the electron density in interstellar medium is higher than predicted (0.13 particule per cubic centimeter as opposed to 0.03). Could we underestimate the amount of matter empty space actually contain between galaxies?
Nick is the Best! What a stupendous "Dark Matter" video! The clearest and most concise I've seen yet. (BTW: Also the most truly comical science videos I've ever seen. "Pur-CELL" and "X-Rays from Space!" had me laugh out loud
Great work as always!
I also like the emphasis on the fact that even though scientists can take part in both, making wild guesses and in carefully deducting conclusions, there is a huge difference between both. Scientists are just as human as everyone else. They like to speculate, too.
Nobody is 100% scientific all of the time. Thats why its important to keep in mind what is what.
I wouldn't be so quick to call it a win for dark matter. Sabine Hossenfelder makes a pretty convincing case for superfluid dark matter--a modification of general relativity.
I have my doubts about that video. For example, she claims that the Bullet Cluster is actually counterevidence for dark matter because “dark matter would cause too much friction” for it to travel so fast - but the entire idea of dark matter is that it doesn’t interact at all besides gravity. Plus it’s clear that the literal placement of mass is ahead of the collision - modified gravity doesn’t explain why the lensing occurs in those specific areas.
One thing that neither Sabine nor ScienceAsylum point out is that we’ve found galaxies that have both “dark matter rotation curves” AND have flat rotation curves. This actually supports dark matter even more - presumably some galaxies have the presence of dark matter while others don’t. Sabine’s final approach, where “a phase transition requires different theories at different scales” actually fails on this point: since galaxies of the same scale can have different rotation curves, modified gravity can’t apply there; it’s best explained as dark matter being present or absent.
That lensing around the bullet galaxy really helped me understand how we know that dark matter really isn't just black holes and unresolvable dust. You can see how the cloud of DM just passed right through, while the regular matter interacted slowing down. If the clusters' grasp on dark matter is so tenuous, how is the dark matter tied to the clusters at all?
I think the greater gravitational effect of the dark matter drags the regular matter along with it. In the case of the bullet cluster, those 2 dark matter globs will eventually recapture all that regular matter that got dragged out.
Cold Dark Matter (the CDM in λ-CDM) in a galaxy does not have enough kinetic energy to reach escape velocity. However, in the case of two galaxies colliding, the dark matter may have enough existing velocity to hit the escape velocity of the new common center of mass, whereas the regular matter gets slowed down by friction and magnetic field lines, and does not (this is also why the regular matter gets superheated enough to shine in X-rays).
EDIT: A bit of clarification, even if the dark matter doesn't hit escape velocity, it isn't slowed down by friction or magnetic fields, so it would overshoot the regular matter even if it will be eventually recaptured by gravity.
There are a few galaxies that don't seem to have any dark matter. It possible that something like the bullet cluster happened in the past for those galaxies and that is why (although we don't know for sure). For instance, NGC 1052-DF2 apparently has no dark matter. Maybe this galaxy (or galaxies in general) after they lose their dark matter eventually get ripped apart by the gravitational or rotational forces that dark matter normally helps counteract. Maybe its somehow related to star formation (this galaxy hasn't formed stars in a long time).
It’s the other way around, I believe. There are vast webs of dark matter, and blobs of ordinary matter at certain nodal points.
The dark matter is shown on my profile pic, 50% more or less of everything appears dark. These are images of photon nucleation. Simply two photons giving birth to a baby one. I went deeper and things are moving so fast it looks chemical or fluidic but there is always matter, dark matter at least the precursors in the fluidic environment it appears to form out of.
I like Vera Rubin's evidence, because I can understand the expectation, that the outer parts of a galaxy spin more slowly (as long as I don't think too hard about it), and I can see that the reality is strange. The Expectation vs Reality animation was excellent, and got me thinking about physics models in general. The temp vs angular size graph around 13:30, as well as some of the equations you showed, while I am grateful, I don't understand these, and so for all I know you could be yanking my chain. Thanks so much for your videos, they are excellent, exceeded only by your character/attitude
To the timeline 😭😭😭 amazing.
And I'm still obsessed with the background music. So amazing 😭😭😭😭😭
Thanks Nick another enjoyable and understandable video. I always enjoy your energy and humour.
The most compelling argument for me (before hearing about that CMB lambda-CDM chart) was the galaxies that do not have dark matter, which just so happened to be missing from this video.
Yeah. that's true.
Now, besides finding DM particles, we must also explain why sometimes, it's just missing !
Yeah this was it for me as well. If the rotational effect was just present everywhere, I would say: "Well, maybe our understanding of gravity is incomplete and there is another factor at work on a galactic scale." But then there ARE galaxies without dark matter, and suddenly all of our equations work as if DM didn't exist in the first place. This, for me, was the strongest hint that DM must exist.
Nick,your videos are getting better and better each
time.
Thanks!
Great video! The way the data fit that power graph made my jaw drop - I don't think I'd seen it before for some reason. Yes, it does seem compelling, although I don't fully understand what the axes meant, so really I ought to be more circumspect :)
I love the fact that your wife is your producer.
Hey Nick, I would be crazy to think that some kind of Lagrangian points resulting from galaxies interactions could account for any of this "missing mass"?
man i love your channel thank you so much
man you explain things so well its unbelievable, you will be a great teacher
Award: This is definitely the physics channel I understand the most content :-D
To me the biggest proof are the few galaxies that have been found with almost no dark matter at all. That shows it’s probably not a faulty measurement , or a gap in the physics…
Agreed. Those galaxies act as perfect controls for the theory of Dark Matter, and it totally holds up.
If they are not found with dark matter it means there is no dark matter?
@@99bits46 No, what it means is that, using our understanding of gravity/relativity/angular momentum/etcetera, we see that galaxies seem to have "hidden matter." One idea is that there's a form of "dark matter" that doesn't absorb or emit light that still has mass, and thus accounts for the weirdness we see.
The other option is that gravity/relativity/angular momentum/etcetera all works differently on these huge scales than what we thought.
So, when we find galaxies that appear to have no dark matter, and then they behave exactly as our current theories of gravity/relativity/yadda yadda predict, that means that all those laws don't actually just function differently on those large scales, but that there is, in fact, invisible matter that permeates most (but not all) galaxies.
Excellent explanation of Dark Matter! You’re great at making complex subjects easier to understand!
Best video yet. First person to successfully explain what the cmb. Really looks like!
i think the most convincing one is the bullet cluster because it shows that it *isnt* simply a case of gravity behaving differently
(though the picture doesnt do it justice, its not very obvious that dark matter is there where you claim it is)
and it also shows that it behaves in a really really really weird way
absolutely amazing. I'm so happy i live in a time that so much work and knowledge is known.
hey where can i get that shirt?
It's a shirt that Wil Wheaton sells occasionally. If you follow him on Instagram, he'll post about it when he does a preorder.
I love the way you explain things in simple terms
First, again a great video! I love your explanations, and often when I had a panic attack and it subsides, I rewatch your content!
A question..I'm interested in buying your physics book, but my math level...I understand calculus fairly well, I just never practice. Would I be able to start understanding stuff? 😍
As long as you have a basic background with Calculus and Intro Physics, you should be fine. The higher-level math stuff is explained within the book 👍
@@ScienceAsylum wow that's a fast fast answer ❤️ thank you 👍
I love this guy. We need his mindset and rigor in every school.
This was so informative! Also, thank you for emphasizing Vera's important contribution in this field as women tend to be greyed out when it comes to science!
This is the best video on this subject I have ever seen: concise, entertaining, and ties together numerous discoveries in an easy-to-understand and memorable fashion. Well done!
Great video! Well-planned and perfectly executed, and I just love your style.
I have questions about how dark matter "doesn't interact" and so kept moving while the regular matter' momentum was slowed... yet its gravity clearly does interact so what interactions am I missing?
Perhaps I need to watch again and ponder.
It's the _electromagnetic_ interaction that dark matter lacks.
How refreshing to hear "there's a consensus with piles of irrefutable evidence" followed by, "let's go through it shall we." You so often get statement 1 on its own so as to stifle debate.
Great work as always.
I think this is the best video already maded for non-scientists about dark matter.
Neil should hired you for the next season of Cosmos.
I love this guy him and his “cameraman” I mean wife lol they do a great job it’s all you want to know about a topic and he doesn’t take himself too seriously. They Makes it entertaining while you learn. I really enjoy your content.
Thank you.
13:47 prediction and measurement matching perfectly is so satisfying....
well, it's a fit to some extent. The ratio was approximate, but the exact percentages are determined from that very observation. But chi2/DoF is nicely near 1, which is all you can ask for.
Indeed
After being confused about the cmb map for a very, long time, you are the first person to show it to me.
Nice video as always Nick!
Btw, I had a question (kinda unrelated to the topic but it's pretty important)
"If gravity is not really a force, then why do we count it in the 4 fundamental forces"?
Because the 4 fundamental forces are not actually forces, at least not in the Newtonian sense. It's better to call them the 4 fundamental _interactions._ Gravity is definitely an interaction.
I love how astronomers become some sort of "archaeologist" with the farther away the things they're studying are
More like "palaeontologist"-archaeology is the study of people in history through analysis of their artefacts.
Great vid Nick. I can’t shake the idea that it’s our knowledge of gravity that is incomplete rather than there needing to be more matter.
As this is a scientific theory with no evidence though, I will have to wait until later in the timeline…
Experimental evidence has made it extremely difficult for MOND (modified Newtonian dynamics) to be reality. The number of hoops you have to jump through to make MOND work is ridiculous. Dark matter is simpler and matches the data better.
@@ScienceAsylum IIRC Sabine Hossenfelder made the case a couple of months ago that that's no longer valid when it comes to simplicity. Certain observations are better predicted with mond and others with DM. I think her argument was that there must be a phase transition between them.
AFAIRC Neil deGrasse Tyson used a term "Dark Gravity'. Covers both - 'Dark Matter' and 'we dont know hell about gravity yet' :)
I LOVE THAT TSHIRT. !!!! thank the powers for this content.. needed. .. respect from far North Queensland, Australia. and thankyou tenfold.
Excellent. Thank you Nick. A good walkthrough and explanation.
Wow... I've heard that galactic rotation speed thing for maybe 10 years, and NEVER knew why it was evidence of dark matter. One good graphic and it popped into my head. Well, two graphics really. I had misunderstood the observation to be like a record player, with the entire disk turning as almost a solid... not "the individual objects moving at the same orbital velocity." So the other graphic of the galactic rotation helped.
I'd like to request an episode on the echo bubbles of the CMB, those are already mainly caused by dark matter as I understood? Can't find much comprehensible material about this topic.
One of the only channels that I don’t skip any parts of the video and watch all the ads! Onwards and upwards Nick 👍♥️
Awesome video. Lot of work on this. Thanks!
The bullet cluster really nails it for me. Once again a great video and fun explanations. If you had a TV show I’d watch it. I am a geochemist not an astrophysicist but the subject fascinates me. Do you have a PhD? What was the subject of your dissertation. I didn’t do astrophysics myself because of the math. Too hard for me, but the concepts you explain are well researched and compelling. Thanks from another crazy 😝😁
No PhD, but I have a masters. I didn't feel the need to specialize anymore after the masters. My thesis was on white dwarf stars 🤓
@@ScienceAsylum My masters thesis was on Oil shales in northern England and the geochemistry of fossilised bio molecules. I originally began a PhD but the department I was working in got closed so I settled for a Masters at the University of Newcastle upon Tyne, UK. 🙂
To me gravitational lensing by dark matter is one of the craziest things out there in the universe.
_Quantum Eraser Double Slit Experiment_ has entered the chat: I'm sorry, what?
Please upload more frequently.
I really love your videos.
I love your uploads and presentations! Whatever happened to Cosmology for now being called astronomy - referring to stars!? I don't get..
Anyways: There is this structure around our solar system called the hydrogen wall and according to NASA it's humongous, but rather faint. Assuming heavier stars or even galaxy having massive H-reservoirs around them.. light from behind should be refracted and bent within that denser medium, so maybe this could be an alternative hypothesis on lensing phenomena. There was also a nuclear physicist named Ari Brynjolffsson who suspected some kind of plasma redshift.
Best wishes