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22 Subatomic Stories: Why dark matter seems likely 

Fermilab
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30 окт 2024

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Комментарии : 739   
@ilkoderez601
@ilkoderez601 4 года назад
"Get me started talking about physics and I'll go all day" ... Yep... TRUTH
@scrymglin
@scrymglin 4 года назад
I'd happily watch an all day video by Doctor Don
@juzoli
@juzoli 4 года назад
“I could spend hours telling you all the ways...” We are looking forward to that hours long video!
@diamondisgood4u
@diamondisgood4u 4 года назад
That's exactly why i listen to sean carols podcasts, I just want accessible smart people discussions, the internet exists now and all the great mind should be able to contribute to the world amazingly and teach/influence others with it! I think we need as much of that as possible in these times honestly.
@qzbnyv
@qzbnyv 4 года назад
@@diamondisgood4u I definitely appreciate the episodes (both of Sean's podcast and others) where they assume that you're already a motivated listener on the topic and the entire episode is not spent rehashing the basics. Like, please, I've binged the entire PBS Space Time episode catalogue (...watching some of the earlier fundamental episodes several times over)!
@jimjones4702
@jimjones4702 4 года назад
A little off subject but if into physics Latest Time Machine paper With a time travel test fixture design included 9-3-2020 Minimum math but must understand algebra. Totally free and free download to use creative commons. www.academia.edu/44012722/The_Second_Dimension_a_Time_Travel_Universe_Dual_Slit_Experiment_Universe_Creation_Solutions Below is same paper at Cern zenodo.org/record/4014246#.X1UekYt7lhF
@patrickaycock3655
@patrickaycock3655 4 года назад
Yes please
@TelB
@TelB 4 года назад
What a marvellous educator. We are so lucky to live in these times where we ‘know’ more than previous generations. I share your curiosity and thirst for knowledge but unfortunately do not have your understanding. That is where your videos are so valuable. You present these concepts that have been laboured over by far greater intellects than mine in a way that I can understand at least some of those concepts. Thank you.
@perrymnazjurgens
@perrymnazjurgens 3 года назад
I so love your teaching style; from your cleverness, gentle voice, honesty and clarity for the complex - THANKS!!!
@JP-sw5ho
@JP-sw5ho 4 года назад
I would watch longer episodes. You always seem so time conscious
@jamesepperson5940
@jamesepperson5940 2 года назад
Yea I wish he would do like 20 minute episodes on each topic. I always want more
@zikomo8913
@zikomo8913 4 года назад
Few years ago, I used to comment here that how Fermilab deserves way more subs, it had around 15k at the time, and now I'm so glad it has more than 400K subs.
@drdon5205
@drdon5205 4 года назад
Help them out. They're aiming for 1M
@esperancaemisterio
@esperancaemisterio 4 года назад
Great video dr. Don! Thanks for sharing!
@shellderp
@shellderp 4 года назад
I took several physics courses in university but didn't learn 10% of what I learned from this channel. Thanks for what you do!
@geeteshlashkari8260
@geeteshlashkari8260 4 года назад
Thank you for considering my comment...!!!
@RingxWorld
@RingxWorld 4 года назад
Sending noticed me
@لالهوةإلالهوتي
@لالهوةإلالهوتي 4 года назад
If space is always expanding and space-time go hand in hand what sort of time adjustment is happening? Is more time being "induced" purely by this expansion? Is this why time goes forward? That must mean the age of the universe itself is a slippery beast!
@KasiusKlej
@KasiusKlej 4 года назад
No time adjustment is happening. Expanding of space does not affect the flow of time. This is because a second is defined as a vibration of Cesium atom. Space within protons may be expanding, protons themselves are not, the expansion just makes them bigger than they otherwise would be. So a Cesium atom will behave the same as the space around and within the atom expands. It is some other mechanism that make time move forward. It is not very well known, but it has to do with when a thing like photon or anything else changes it's position in space. All that is known is that some time has to pass when this happens.
@Turnip420
@Turnip420 4 года назад
That's a good question. Now please don't take my answer as granted but I think since space and time are entangled we can compare it to the expansion of space. If it was like the building unit of space stretched over time we could not quantize the rate of expansion, i.e. hubble rate. Because meter itself would change. So I think as the space stretches new space is born, i.e. the Planck length does not change. So the same can be said about time.
@101starting
@101starting 4 года назад
Depends on speed of the increase if near the speed of light time should slow down or stop
@Turnip420
@Turnip420 4 года назад
@@101starting yes and no. Time would slow down from the standpoint of an external referee, in an implicit way. The correct way to put this is time speeding up for the referee while going casual for the reference. Also if the reference is not massless they can never reach the limit velocity of light. So they would experience local flow of time just like a static referee does. But their local time passes by way slower compared to the referee. Ps. This means time cannot stop unless you are massless, like a photon, and if so you are already traveling at speed of light and not experiencing time.
@paulfrancis8836
@paulfrancis8836 4 года назад
The Question is Easy, but the Answer has got me. Good question though.
@jameammarijr.2248
@jameammarijr.2248 4 года назад
Even at home, physics is everything
@scudder991
@scudder991 4 года назад
Fascinating episode, Dr. Don. Thank you!
@KonekoEalain
@KonekoEalain 4 года назад
Still loving this series, thank you!
@jeroenw9853
@jeroenw9853 4 года назад
It would be interesting to learn how scientists know this much about the galaxies far far away, like what it contains, that it is spinning etc.
@MuttFitness
@MuttFitness 4 года назад
If they weren't spinning, they'd collapse into the middle. Not a complete answer, I know.
@SkorjOlafsen
@SkorjOlafsen 4 года назад
It's red- and blue-shift mostly. We can tell the relative motion of different parts of a galaxy by the shift in the spectral lines of the stars. if a spiral galaxy is edge-on, or mostly so, then it's motion is fairly clear even when it's too far away to tell much about its shape. If we're seeing its flat side we know a lot less, but you can still tell a flat galaxy from an elliptical one by how thr brightness changes from the center to the edge.
@evanpowers1226
@evanpowers1226 3 года назад
If you performed poorly in high school do not give up hope! I earned terrible grades in high school, before I discovered my passion for physics & astronomy. I spent 2 years at community college, transferred to a 4-year university and have earned high marks all 4 years, in addition to gaining multiple research experiences. Genuine passion and determination will prevail!
@alanboro
@alanboro 4 года назад
Thank you very much Dr Lincoln for your answer!
@Kousha
@Kousha 4 года назад
Hi, Dr. Lincoln! One thing that I would like to ask (even though in pretty unrelated to this video's theme itself) is: how did you started the Fermilab RU-vid channel? I would love to do some Scientific Outreach channel of our lab but, even though we already have the shooting and editing expertise, I have a hard time figuring out how to start. Love the channel, can't wait for the next Subatomic Stories videos!
@kfitch42
@kfitch42 4 года назад
Let's start a personal crackpot theories thread. Here are mine: There are an infinite number of fundamental forces. Each force stronger than the previous. The pattern follows from the observation that gravity has only one kind of "charge"(all mass attracts). Electroweek has two kinds of "charge" (positive and negative). The strong nuclear force has three kinds of "charge". The next force will have four ... This would remove the singularity in black holes because these stronger (as yet undiscovered) forces would kick in. Where is all the missing antimatter? It formed the supermassive black holes we don't yet understand the origin of. I am expecting great things from alphag/gbar to confirm my theoretical brilliance. I'll be patiently waiting for my calls from Stockholm :).
@revalaghate9254
@revalaghate9254 4 года назад
Is this a theory or an approaching novel
@chuckphilpot7756
@chuckphilpot7756 4 года назад
Is it not possible that the black hole at the center has much more reach than we thought and thus its spin could be effectively pulling everything around faster than we think it should? Or if the black holes are way more massive than we thought they were?
@LordOfNihil
@LordOfNihil 4 года назад
dark matter is cats! they tend to move when observed and can hide practically anywhere so there might be a lot more cats in the universe than we think there are.
@OnTheRiver66
@OnTheRiver66 3 года назад
And they are responsible for CATastrophes and CATaiclisims. I think of them as grey, white, black, and tabby matter.
@GiacomodellaSvezia
@GiacomodellaSvezia 4 года назад
As a 'lay person' but physics enthousiast, I like to turn it around and say "even at work, physics is everything". Stay safe everyone, for the SARS-COV-2 virus raises more urgent questions than neutrinos do, at least for now.
@cloudpoint0
@cloudpoint0 4 года назад
Don’t be so negative toward viruses. They are beneficial to our planet. Viruses exist for a reason. They cleanse the planet of its most destructive and unwanted lifeforms.
@Novarcharesk
@Novarcharesk 4 года назад
Given that the virus kills less than half of 1% of those who have contracted it, and of that number, the vast, VAST majority of victims are very old people, I'm pretty sure staying safe is an easy prospect.
@barryomahony4983
@barryomahony4983 4 года назад
@@Novarcharesk A majority but not vast. 42% of fatalities are under 75
@GiacomodellaSvezia
@GiacomodellaSvezia 4 года назад
@@Novarcharesk It's not pretty when you catch the disease and get ill: Many people have long lasting symptoms of variable severity and possibly some won't ever completely recover. It's also a problem to catch the disease without getting ill: You might infect a lot of people without knowing it.
@GiacomodellaSvezia
@GiacomodellaSvezia 4 года назад
@@cloudpoint0 The role of viruses in evolution is complicated, even more complicated than immunology.
@cdgt1
@cdgt1 4 года назад
Presently the electromagnetic scale shows that energy and angular frequency increase in the same direction. Simply invert the energy ( while keeping true to Kgm^2/s^2 ) so that it increases in the direction of lower frequency and dark energy and the accompanying dark matter disappear.
@101starting
@101starting 4 года назад
Doc Don thank you so so so much for your videos keep them coming Please ;) greatly appreciated
@jonathanhacker8225
@jonathanhacker8225 4 года назад
I recall hearing of gravitational lensing around clouds of dark matter in intergalactic space? How much evidence is there actually for dark matter lensing? Is there any?
@tonywells6990
@tonywells6990 4 года назад
When astronomers try to measure the mass of galactic clusters causing the gravitational lensing they come up short by quite a bit, which is evidence for dark matter.
@IntraFinesse
@IntraFinesse 4 года назад
Dark matter doesn't clump, so there won't be concentrated clouds of dark matter, it will be more spread out. Thus it won't really provide gravitational lensing.
@tonywells6990
@tonywells6990 4 года назад
@@IntraFinesse Dark matter causes most of the lensing in galactic clusters.
@IntraFinesse
@IntraFinesse 4 года назад
@@tonywells6990 Dark matter does not cause gravitational lensing in intergalactic space, which is the question the OP asked and I answered.
@tonywells6990
@tonywells6990 4 года назад
@@IntraFinesse In clusters can you really distinguish intergalactic space? It makes up most of the volume.
@artistart8566
@artistart8566 4 года назад
Love to connect with you. Much respect 🙏
@richtalk34
@richtalk34 4 года назад
Excellent, thought-provoking video as always. Thank you. Do you feel that that the solution to the dark matter conundrum, assuming it is found at some point, will ultimately result from a particle-physics or an astro-physics breakthrough?
@Mosern1977
@Mosern1977 4 года назад
Few things to note on Dark Matter. 1. Our observations of the cosmos and most distances/velocities are indirect - hence they can be wrong. 2. Dark Matter may not be one thing. These different "proofs" of Dark Matter (or lack of such) can be caused by different things. 3. Other things than gravity alone might be at play at galactic scales.
@Juanma4033
@Juanma4033 4 года назад
What a impressive video today. Extraordinarily explained
@jasonmcintosh2632
@jasonmcintosh2632 3 года назад
Best treatment of dark matter i’ve watched. This is good science. Present the facts, the postulates that govern them, and the strengths and weaknesses of each postulate. I only wish this was longer. I’ll be looking for your other videos on this topic.
@perryp6191
@perryp6191 4 года назад
Bloody Legend
@majorbones251
@majorbones251 4 года назад
What’s your take on Mike McCulloch’s theory of Quantized Inertia? Can it explain the gravitational lensing we see from large galaxies if dark matter doesn’t exist?
@harshildeora1001
@harshildeora1001 4 года назад
It can explain the great velocities of stars at the edges of galaxies, but it cannot explain the gravitational lensing effect we see due to dark matter.
@BobJones-dq9mx
@BobJones-dq9mx 4 года назад
ANOTHER GREAT tutorial! Thanks!
@SamB-gn7fw
@SamB-gn7fw 4 года назад
This series is amazing
@grahamrankin4725
@grahamrankin4725 4 года назад
Still wanting to know where you get your shirts.
@ChargeOfGlory
@ChargeOfGlory 4 года назад
@fermilab What do you mean by " if dark matter is real then it should stay with the galaxies, if dark matter isn't real then *it* should stay with the gas." if dark matter isn't real then what should stay with gas? I don't understand the sentence. Sorry English isn't my first language.
@video99couk
@video99couk 4 года назад
Can I make a humble suggestion? If you place the camera and auto-cue screen further away, then zoom in with the camera, the "reading a script" affect will be much less, as your eyes will stay looking more centrally at the camera. I know, I used to have the same problem.
@drdon5205
@drdon5205 4 года назад
Just out of curiosity, where do you imagine the auto-cue screen to be?
@video99couk
@video99couk 4 года назад
@@drdon5205 Right in front of the camera lens. Generally you can make the text large enough to read from a good distance. See Technology Connections channel for an example of a good setup.
@donlincoln1961
@donlincoln1961 4 года назад
Nope. It looks to me like it is off to the left, but that's not true either. In any event, thank you for your suggestion.
@wayneyadams
@wayneyadams 4 года назад
I miss teaching since I retired so this is one of the few places I can still teach, albeit only occasionally and not with the depth of having an actual class. In addition, there is no way to include diagrams. So today you will learn about centripetal force, and centripetal acceleration. If you read Dr. Lincoln’s paper in The Physics Teacher, you would have encountered an equation with Newton’s famous gravity equation on the right side of the equality and another equation on the left. The left side is the equation for centripetal force. The word centripetal is the combination of “centri” from centrum meaning center, and petal from “petere” meaning seek, or go to. It is sometimes confused with centrifugal. “Fugal” means to fly off as in the word fugitive. One is a force pushing the body toward the center of the circle, the other is pushing it away from the center. Huh? What the heck am I talking about? Centripetal force is the force that actually forces the body to move with circular motion. There is a force, such as a string, friction of tires on a road, or gravity that moves the body around the circle. You can actually identify the source of the force. Centrifugal force is what we call a virtual force. It is the result of inertia. Here is an example. The car you are riding in goes around a curve, the seat pushes on you (centripetal force) causing you to go around the curve with the car. But we know that your body like all mass tries to continue traveling in a straight line (inertia), so you experience what seems to be a force pushing outward as your body tries to move straight forward. Just as you seem to experience a force pushing you backward into the seat when the car accelerates as your body resists the change in motion. There is no source pushing you outward as with the inward centripetal force. Now, on to the equation for centripetal force. I will try to explain it in an intuitive way so you understand why it is written the way it is. Most of you have seen it in your high school physics class, where the teacher just presented it to you and explained how to use it, but never explained why it looks the way it does. Bear with me, and you will understand, I hope. A word on notation. Since I cannot use exponents, I will use v^2 to mean v to the second power (squared), the “^2” being the exponent. The equation is: F = mv^2/r F = centripetal force, m = mass, v = velocity, r = radius of the circle. To simplify, we know that F = ma, so we can eliminate the mass, m, and concentrate on the centripetal acceleration, a = v^2/r Let’s address the v^2 in the numerator first. Why is it v^2? Why not v or some other term? Acceleration is the change of velocity of a body divided by the time it takes for the acceleration to occur. a = dv/dt Since I cannot use the Greek letter delta, I will use d in its place, which incidentally for you math savvy types, is the differential equation. Let’s look at two identical bodies with the same mass traveling around circles with radius r. Body A travels at velocity v. while body B travels twice as fast at 2v. We will examine the motion as they travel half way around the circle (180 degrees) . Body A starts with velocity v, and on the opposite side of the circle has velocity -v (opposite direction). So dv = v - (-v) = -2v. To simplify. I am going to ignore the signs and focus on the magnitude of the change which is 2v. Also, dt = t. Its acceleration is: a(A) = 2v/t Body B starts with velocity 2v and ends with velocity -2v, so dv = 2v - (-2v) = -4v, simply dv = 4v. But since it is traveling twice as fast, it takes half the time to make the trip so dt = 1/2t. a(B) = 4v/(1/2t) = 8v/t. Notice body B has four time the acceleration of body A. The change of velocity is doubled, while the time is halved, resulting in a fourfold difference. Changing the velocity results in a change in both the numerator and denominator. The numerator is multiplied by some factor, let's call it n, while the denominator is the reciprocal (1/n) of the factor. The result is n/(1/n) = n^2 It works for any multiple of v. You try it with 3v. I’ll wait here. (Jeopardy music plays, “Do do do do, do do do, ….) . . . . . . . . Times up. Here’s the answer. dv = 3v - (-3v) = -6v, or simply 6v dt = (1/3)t a = 6v/(1/3)t = 18v/t Which is 9 times, 3^2 or with symbols, v^2. The radius term is much easier to understand. It is linear and located in the denominator because increasing the radius increases the distance traveled and thus the time. So, tripling the radius requires three times the time so the acceleration is one-third. a = v/3t There you have it, the reason the equation looks the way it does. This is where we would go into the lab and do the spinning mass experiment, and hopefully not put anyone's eye out ("You'll shoot your eye out!", A Christmas Story, 1983) Everyone was having a good time learning physics and then someone lost an eye. Wayne Adams B.S, Chemistry (ACS Certified) M.S. Physics R&D Chemist (9 yrs.) Physics Instructor (33 yrs.)
@Unknowngfyjoh
@Unknowngfyjoh 4 года назад
What is the escape velocity of a theoretical quark star? Strange matter? Electroweak matter? Is it >c?
@sluxi
@sluxi 4 года назад
By far the best explanation I have seen for why the current science favors dark matter over MOND.
@tresajessygeorge210
@tresajessygeorge210 2 года назад
THANK YOU PROFESSOR LINCOLN...!!!
@richardpepe9615
@richardpepe9615 4 года назад
I really enjoyed this episode! Wondering if you can talk more about the expected properties of dark matter.
@tinywillis
@tinywillis 4 года назад
I'm compelled to respond to your assertion At 5:25 MOND could certainly be "switched on or off in a galaxy" when we consider the increase in gravitational force observed as excess mass, as a variable that is dependent on the motion of that galaxy. Galactic rotation speeds, and linear movement of Galactic Nuclei would be variables in need of consideration when calculating the effect (if any) of MOND on the perceived mass of a particular galaxy or group of objects. So to say that The Bullet Cluster and "Galaxies without dark matter", are proof of dark matter or evidence against MOND seems rather presumptive.
@Bassotronics
@Bassotronics 4 года назад
I wonder also if dark matter is matter which has a “non-normal” charge parity which violates symmetries but conserves energy in a certain way thus by causing normal matter to “misbehave”. I don’t know. There are so many things that can be Dark Matter as in anything that does not follow the current laws or physics or probably a entirely “new” type of matter we still don’t understand.
@JxH
@JxH 4 года назад
*"No electromagnetism means no clumping"* I think that many of us are thinking in terms of *GRAVITATIONALLY* bound clumping. If Dark Matter exerts gravity, then wouldn't it attract itself into large "clumps", bound together with *GRAVITY* ? This is the 2nd episode running where you mentioned the same thing, but missed that we're asking about *GRAVITY* bound "clumps". I'm sure that there's an explanation... Thank you !!
@MasterBunnyFu
@MasterBunnyFu 4 года назад
"Clumping", or reducing the overall orbital radius, requires shedding kinetic energy or converting it into another form. This generally can't be done via gravity alone; gravitational waves only come into play with extreme masses, and "gravitational assist" type interactions only apply between bodies with significantly different masses. So you need some other way to interact or radiate away energy, and electromagnetism is the only other long range force.
@bjarnivalur6330
@bjarnivalur6330 4 года назад
Hi, I'm a bit curious about the model that is often shown of how dark-matter surrounds galaxies, it's usually shown as a sort of halo or a sphere around the galaxy, why not a disk like most spinning things, is it just because it doesn't feel EM-force so it doesn't clump together?
@KasiusKlej
@KasiusKlej 4 года назад
Because it is not spinning. Space dust around galaxies is not spinning, it is rather orbiting the galaxy in all possible orbits, making thus a sphere like shape. It is like space dust has some weather where the is not much wind, and then within galaxy there it becomes windy, and stars are spinning like in a tornado, most famous for it's shape probably being planet Saturn.
@drdon5205
@drdon5205 4 года назад
Yes.
@adriang.cornejo4800
@adriang.cornejo4800 3 года назад
Dears. As reference, the paper where is described a solution of the rotational velocities observed in spiral galaxies, without using dark matter (but adding the Coriolis force in the rotating system, from the General Theory of Relativity), is the following (from 2020): article.sapub.org/10.5923.j.astronomy.20200902.01.html
@justinmueller2825
@justinmueller2825 4 года назад
It seems that the most accepted model for dark matter is WIMPS. But do we have a good reason to assume that dark matter interacts via the weak force? What if it only interacts via gravity? In that case would it ever be possible to learn what it is?
@drdon5205
@drdon5205 4 года назад
Maybe not. That's where we are now.
@JereckNET
@JereckNET 4 года назад
Dark matter does not interact with normal matter through electromagnetism but it does through gravity. Could it interact through other forces like the Strong Force ? ( I.e. particules with no electric charge, but with color charge ?)
@JulianOnions
@JulianOnions 4 года назад
I think the strong force is ruled out, as we would see it. Most detection experiments rely on it interacting by the weak force, which is, well, weak, but that said, there is no compelling reason it has to undergo weak interactions, depending what it turns out to be.
@ilkoderez601
@ilkoderez601 4 года назад
Do any of the string theories give possible insight into dark matter?
@Anaesify
@Anaesify 4 года назад
ilko derez Some string theorists believe that some of their candidates for SUSY particles exist as dark matter particles, so yes there’s some data out there about it
@yoavboaz1078
@yoavboaz1078 4 года назад
what is your favorite particle?
@iam_anand
@iam_anand 4 года назад
Why there is different laws for partical physics and physics for massive objets ?
@SkorjOlafsen
@SkorjOlafsen 4 года назад
It's the same laws, but different forces have different ranges. Gravity and electromagnetism go on forever, but the strong and weak nuclear forces just don't. They only have a range of a large atomic nucleus. Beyond that, they just have no effect. Also, all the complexity of quantum mechanics usually stops mattering for large objects made of many particles. When you average out the effects of quantum mechanics over a lot of particles, you get the older laws of physics. They're the same laws, really, just considered at different scales. You can make statistical assumptions about a trillion particles that you can't make about one particle.
@SimonJackson13
@SimonJackson13 4 года назад
A differential equation I wrote and bosons are looked at as a relativistic correction as the observer is not as still as the lab paper view imagines. The number of light bosons stems from the cyclotomic of 18 (divisors 1, 2, 3, 6, 9, 18 and new roots 1, 1, 2, 2, 6, 6) for 18 normal bosons (6 free ones as 18-12 [not fermion bound], sounds like some regular “found bosons”) and if the equality of the mass-independent free space view to zero is just an approximation to the reciprocal of a small oscillation then a differential equation for such is just scaled by units of Hz2 and having which would place the cyclotomy at 20 (divisors 1, 2, 4, 5, 10, 20 and new roots 1, 1, 2, 4, 4, 8) for 20 dark bosons perhaps? Or maybe it works inversely for reducing the cyclotomy to 16 (divisors 1, 2, 4, 8, 16 and new roots 1, 1, 2, 4, 8) or 16 dark bosons? Or “free dark bosons” at a tally of 2 (or -2)? I think I used η with a floating ~ (tilde) to indicate this secondary oscillation. Fermi exclusion unique factor domain expansion? Non-unique compaction “gravity”? What tickles my mind is the idea of 2 "ultra free dark bosons" as an idea. Put another way
@dwightk.schrute8696
@dwightk.schrute8696 4 года назад
Hi Don, thanks for the video, what do you think about the recently published data from the XENON1T experiment?
@Nostradamus_Order33
@Nostradamus_Order33 4 года назад
Office
@dwightk.schrute8696
@dwightk.schrute8696 4 года назад
@@Nostradamus_Order33 you the troll Halpert right?
@csabanagy8071
@csabanagy8071 4 года назад
I still think dark matter is not particle like. I would think there is something to do with gravity and with field theory. It seems for me that in huge scales the space itself gets momentum and distorting a bit the local reallity. What in big scales summes up and become a wierd fenomenon. This is still a question how fotons and virtual particles can be responsible for the observed behavior.
@bennymarshall1320
@bennymarshall1320 4 года назад
Dr Don is assuming that artcamp's finger is not as massive as a star.
@ryan-cole
@ryan-cole 4 года назад
Is it possible that dark matter and MOND are equivalent theories? A quantized version of MOND should have particles, so couldn't we identify those with dark matter particles?
@mjm3091
@mjm3091 4 года назад
9:55 I mean there are those first few "milliseconds" from the Big Bang when we arent sure about physics. There isn't a lot possibilities that those changed qualities may be brought back somehow, but still - there is always a chance. And there is also always a possibility that dark mater could somehow decay at some point into matter - after all we don't know a lot about it. For all we know it could have decay time that exceeds our times.
@dontknow2371
@dontknow2371 4 года назад
Is dark matter distributed in the universe independent of normal matter? Or does it tend to be in galaxies and galaxy clusters? Maybe a galaxy without dark matter is really a region of the universe without dark matter. That could mean dark matter is not particles but a property of space/the universe itself and "static".
@michaelsommers2356
@michaelsommers2356 4 года назад
Roughly speaking, dark matter and ordinary matter are found together. They do, after all, attract each other gravitationally.
@huepix
@huepix 4 года назад
Maybe mass doesn't cause gravity and instead, gravity (warped/moving space) causes mass/baryonic matter. I postulate that spheres of empty space between galaxies are expanding. As they collide, the relative velocities result in a 'warped' area, that manifests as tiny, spinning, fields. As the field spins, any observer (who is also moving relative to the field) will only be able to inteact with a part of the field that is moving, relative to the observer. I.e. as the field spins, the bottom moves opposite to the top, so, depending on the observers movement, only a part of the field is in phase, and only that 'point' can be observed. That's why particles move as waves; because they are part of a spinning field. This is also why the double slit experiment works the way it does. So yeah, the idea is that dark matter is actually voids of empty space expanding (you can see them in every deep space image exactly as the postulate predicts), and where they collide, as the colliding velocities approach specific percentages of the SOL, they form, tiny areas of spinning space that interact to form matter, subatomic particles etc resulting in galaxies where space collapses into the black hole. This means reality is eternal because bubbles of space are expanding into areas of collapsing space, black holes, which 'reseed' then bubbles via hawking radiation, neutrinos etc. Hope that makes sense.
@teejayevans
@teejayevans 4 года назад
How sure are we that the gravitational constant is constant every where? Could massive black holes be effecting space changing the gravitational constant? Galaxies without a massive black hole would rotate as expected.
@JulianOnions
@JulianOnions 4 года назад
1) We're not 100% sure, but all the evidence seems to point that way, hell we are not even sure what the value of G is to more than a small number of digits. 2) There is no way we know to change the gravitational constant, so probably not. 3) The massive black hole, for all its mass, is a tiny component of the overall mass of the galaxy (maybe 1/1000000th of it). So galaxies would work fine with or without a super massive black hole, it's just that they all seem to have one.
@pamelaberkman3864
@pamelaberkman3864 4 года назад
These videos totally make my Wednesdays.
@martijnvangorp
@martijnvangorp 4 года назад
Ok. Well balanced explanation for DM.
@Franciscasieri
@Franciscasieri 4 года назад
7:50 example...why do you assume his parallel universe contains gravity? Why couldn’t his parallel universe consist of matter and forces there upon that we don’t yet know?
@dwightk.schrute8696
@dwightk.schrute8696 4 года назад
what if each "clump" of dark matter in our universe is a separate universe bleeding it's gravity to us via mechanism unique to our universe (that's why they don't interact with each other)
@DavidBeaumont
@DavidBeaumont 4 года назад
@@dwightk.schrute8696 "what if" is a great question. Then you do lots and lots of math and modelling to see what it implies. Almost always this sort of very specialised/custom hypothesis ends up having some pretty obvious implications that just don't match reality though, and are quickly discarded.
@dwightk.schrute8696
@dwightk.schrute8696 4 года назад
@@DavidBeaumont honestly I'm too dumb and lazy to learn the level of math needed to do this. I can tell my "what if" scenario is flawed because it needs parallel universes to exist (extremely hard or impossible to prove), as well as it just shifts the problem to a different domain (how is our universe this special). Thanks for the comment!
@DavidBeaumont
@DavidBeaumont 4 года назад
@@dwightk.schrute8696 Right, it's always tempting to make a hypothesis that neatly fills the current gaps, but it almost always leads to other (often far worse) issues to be solved.
@dwightk.schrute8696
@dwightk.schrute8696 4 года назад
@@DavidBeaumont Yeah, the model needs to have sufficient predictive power to be useful. I think the bigger question is when to keep refining a particular theory and when to try something else -- imagine encountering the Cosmological constant problem early in the development of QM. How many important people would have jumped the boat?
@mati94z6
@mati94z6 4 года назад
Assuming that atoms can’t be transferred by ‘white holes’ because when entering black hole they are disassembled, can the gravitational influence of dark matter be explained by the existence of those supposed ‘white holes’ which instead of emitting regular matter, only cause gravity disturbance, by changing matter into some kind of gravitational energy? Or maybe the gravity is emitted by high-velocity subatomic material leaving them because nothing else can? For the purpose of this question we need to assume that black hole and white hole form a connection between them like wormhole etc.
@marcobinda
@marcobinda 4 года назад
Hello Don. About episode 22 of Subatomic Stories, is it possible that dark matter is just ordinary matter, but in the form of small particles sparsely distributed throughout the universe and we just cannot see with our current technology, given the astronomical distances (or we already started, as in the case of Hubble's "lost light")? Love the show!
@JulianOnions
@JulianOnions 4 года назад
That is generally what we call dust, and it makes up a small fraction of the galaxy, is well understood and charted! We can see it because it blots out light, or at least makes it fainter.
@lankydog2130
@lankydog2130 4 года назад
I heard a theory that dark matter/energy could be explained if gravitons had mass, has this been tested (if possible) or is it generally ignored as it contradicts other theories?
@Teatime4Tom
@Teatime4Tom 4 года назад
Do not listen to that person's theories anymore. You got a link or a name? I'm not willing to give the algorithm an aneurysm by putting "what if gravitrons have mass" in my search history.
@_siya.393
@_siya.393 4 года назад
ya it had already been tested why LHC that yet there is no such graviton particle
@maxryan5989
@maxryan5989 4 года назад
Is a degree in theoretical physics a good choice for becoming a theoretical physicist?
@MuttFitness
@MuttFitness 4 года назад
It's almost 100% necessary. I mean a doctorate of course. Undergrad is just physics.
@dw8931
@dw8931 4 года назад
Hi Don, I'd like to ask two questions. You have been talking about gravitational waves and what enormous amounts of energy they set free. Considering the law of energy conservation, I wonder what happens with this energy, when the wave hits some matter. Does the matter get warmer, does it emit some radiation, is it accelerated into some direction, does this collision create dark matter/energy, ...? My second question is if there is a quantum of temperature. What happens if the temperature of a matter gets close to 0 K? Can its temperature get any close to absolute zero, or will there be some point where temperature jumps discretely from something to 0 K? (I am asking, as an ever expanding universe will get colder and colder, and that way its temperature will (maybe asymptotically) get closer to 0. In the first case the universe will never cease to exist, in the second it very well might.) Your answers are welcome! ;-)
@Lantalia
@Lantalia 4 года назад
With regards to the 'normal matter in parallel dimension', while it doesn't _explain_ everything, if there are precisely two then it is just an equivalent (as the term parallel dimension is used in common parlance) way of saying that there is a dark sector with a full copy of the standard model. We would still need a primary form of dark matter that has the diffuse properties observed. It would be kind of awesome if we definitively discovered an interaction window to such a sector, and then _still_ needed something else to explain the issues that started us looking for it
@danielobrien9502
@danielobrien9502 4 года назад
Do you have a recommended resource for explaining the mathematics involved in our equations for gravitational lensing?
@Steaphany
@Steaphany 4 года назад
What are the titles of the books on the shelf behind you ? Which ones would you recommend for various levels of physics backgrounds ?
@nayaraamaraldesouza4966
@nayaraamaraldesouza4966 4 года назад
Are particles of ordinary matter or particles of dark matter more likely to fall into a black hole? Can dark matter under conditions of high energy and acceleration, as in the event horizon of a black hole, collide with other particles, or emit some kind of cosmic ray?
@chriszachtian
@chriszachtian 4 года назад
As far as I know, there is no possibility to cool for dark matter. So it can not loose energy, so it takes longer to spiral down to the black hole. That is also the reason for it to be situated in a halo around galaxies, people think.
@drdon5205
@drdon5205 4 года назад
@@chriszachtian Correct.
@piratk
@piratk 4 года назад
Do we consider the time factor for gravity on large scales? I mean, even slowish objects will not perceive each other in "symmetrically" opposite places, and thus will not tug on each other in a straight line, same way or even with the same force.
@x_abyss
@x_abyss 4 года назад
Hi Don, you mentioned that the absence of dark matter in some galaxies that are yet to be discovered could explain the orbital mechanics of stars in the outskirts. Is galaxy formation even possible without a dark matter halo?
@drdon5205
@drdon5205 4 года назад
Yes.
@jsykes1942
@jsykes1942 4 года назад
I would like to add some suggestions for the graph and commentary presented at 7:41 in this video. I think it would be better if the yellow line were presented upside down and then flipped left-to-right, plus if the yellow line could be shown below the X-axis and to the left of the Y-axis - which is not shown on the graph in this video. Right now, the yellow line is shown at the top right of the graph and I contend it would make better sense if it were shown below, and to the left, of the zero point in the graph. I also contend that the parallel dimension is not in a separate universe, but rather it exists in a parallel space, at the same time, in the same universe as ours because a complete universe should require a “plus”, a “minus”, and a “zero” in between. To properly represent this we will need a master, absolute zero vector, represented by the zero point in this graph. Then all other vectors would become subsets of this master vector. This also means that a complete equation of gravity would not fit well among the Lagrangian equations. An equation for gravity would only make meaningful sense if it were shown as a master equation and all of the Lagrangian equations shown as subsets. Of course, all of the Lagrangian equations will also have to be duplicated and “inverted” to represent the parallel dimension. Remember we are not dealing with quantum mechanics here. We are dealing with extremes - with zero, positive infinity, and negative infinity - where the difference between zero and infinity may only be a matter of one's perspective. If we can adjust our thinking in these terms, then I am very confidant that very soon we will be able to re-evaluate previous observations to prove beyond doubt the existence of a parallel dimension, and then we will be able to quickly resolve the problem where Newton's equations fail to explain orbits of stars at the outer edges galaxies. We will also be able to use a parallel dimension to describe black hole singularities in much more detail than we can now, which we can then use to complete a final equation of gravity.
@solarslingshot3611
@solarslingshot3611 4 года назад
Could the galactic rotation problem be explained by frame dragging, or does the math rule that out?
@Dl1836
@Dl1836 4 года назад
If dark matter doesn't clump, why is it 'in' galaxies as opposed to just equally distributed throughout intergalactic space?
@psuzzi
@psuzzi 4 года назад
Amazing video, you're a Rockstar in the Physics scene. I'm looking fwd to learn more also about Dark Energy. If you plan a video about it, I have a question on that - Q: Could it be that Dark Energy is the energy released by past Gravitational Wave events? If this is possible, how can we measure the energy released as "ripples" in spacetime?
@nHans
@nHans 4 года назад
Dr. Lincoln, this is the second episode wherein you mentioned that electromagnetic interaction is required for matter to clump together. I actually didn't know that before-I believed it was gravity alone that brought matter together to form asteroids, planets, stars, and black holes. Now, however, I can see how ordinary (fermionic) matter in rocks, asteroids, and solid planets like the earth are held together by electromagnetism (chemical bonds) rather than gravity alone. It's clear that gravity would be too weak to keep the smaller asteroids together; it couldn't even hold on to the atmosphere on the Moon and Mars. But then, you also said that dark matter can form black holes by interacting through gravity alone. A little confused, I did google for answers. It seems that the role of electromagnetic interaction is to _dissipate_ energy so that the particles can condense under gravity. I'm not sure I understand what that means; I'd love it if you would clarify it in your simple and straightforward style. Does this explain how gas giants like Jupiter are formed? What about neutron stars? The neutrons should be electrically neutral, so electromagnetism shouldn't play a role.
@Bodyknock
@Bodyknock 4 года назад
Basically I think what he's getting at is that you need electromagnetism to induce what is essentially friction between objects, converting kinetic energy into heat for instance and slowing the objects down. Without dissipating kinetic energy as heat or a similar mechanism to slow them down gravity simply wouldn't be able to coalesce a large cloud of fast moving dark matter particles into the equivalent of a dark matter planet or star let alone into a black hole. It's not that you couldn't in principle have enough dark matter of massive density forming a black hole, it's that in practice it never happens because there's no mechanism to make the dark matter slow down enough in large enough quantities to form anything more than a massive gas like cloud. Gas giants are essentially stars that didn't quite get large enough to ignite. They're like a local almost-star that forms near a larger actual star while their system is young. For the most part what makes a star form is also what makes a gas giant form, except that a gas giant is probably so relatively close to its parent star that most of the mass it could have gathered instead got pulled in by the larger mass of the parent star. Hypothetically though with a large enough cloud of initial material you could have two stars form orbiting each other, and indeed many stars are in binary pairs and it's not unreasonable to think a lot of those pairs formed from the same local gas clouds. Neutrons are quantum particles so don't exactly behave like you might expect a classical object to. Even though they have a weaker reaction with the electromagnetic force they do still have a magnetic moment so they do interact with each other like you might expect two magnets to interact. And they are made of quarks held together by the strong force so hypothetically two neutrons that are extremely close might interact through that as well. Finally even though a black hole would basically never form from dark matter without some really insane artificial process driving it, existing black holes probably do devour dark matter particles all the time and their mass would increase the mass of the black hole. So while you won't ever find a black hole made entirely of dark matter it is entirely possible that dark matter does have a tiny role in increasing the mass of a black hole passing through it.
@lunatyk1976
@lunatyk1976 4 года назад
Hello. Is it possible to map dark matter in the universe or a cluster just by mapping galaxies with or without phenomena of extra speed? Having those it is possible to Focus on most dense regions and internal interactions between galaxies. More over having the full map we might have calculate how much of the dark matter is really present.
@sachin6789
@sachin6789 4 года назад
Namste sir is there any experiment done which established the existence of ether ? I think in us army laboratory conducted by *silvertooth* pls clarify it sir.....🙏
@ChrisWalshZX
@ChrisWalshZX 4 года назад
Regarding question 1.. Are scientists thinking that if Dark Matter is real (i.e massive particles) then would it be bosonic like photons or fermionic like electrons and protons? Bosons don't bump into each other and so wouldn't clump together to make a black hole.
@polwayirbla
@polwayirbla 4 года назад
Lately I've been watching Sabine Hossenfelder's videos about DM and MOND and I feel that the case for classic DM isn't as compelling as you have presented. She explains why the Coma Cluster does not refute MOND. Also I think the galaxy without DM is not confirmed. It could just be a mismeasurement in the distance between the galaxy and us.
@Dragrath1
@Dragrath1 4 года назад
yes and no there is more nuance that is glossed over. For example while the initial possible galaxy without dark matter has been challenged other examples of diffuse galaxies that appear to lack substantial dark matter have been identified. MOND can be tweaked to account for the Bullet Cluster but I don't think those tweaked models can yet account for all of MOND's issues and MOND itself lacks an actual mechanism itself drawing from empirical data. One of the most interesting things regarding MOND was a hypothesis discussed by Sabine in one of her videos about why both MOND and dark matter may be needed which is based off the similar formulation between the correction terms for gravity in MOND's equations and the equations of motion in a superfluid /Bose Einstein condensate. So the strengths and weaknesses of CDM and MOND may actually be evidence for a phase transition as cold dark matter cools off into a superfluid. This also has the advantage of not requiring gravitational waves to travel slower than light and thus makes it consistent with observations of the Neutron Star Merger I like this idea because with sufficient resolution it should be possible to test it by looking at the rotation curves of isolated galaxies over cosmic time even if this dark matter can't be explicitly identified. It also offers an explanation for why our efforts to find cold Dark matter may have came up short since the dark matter in the Local group should be cool enough to become a Bose Einstein condensate instead of discrete particles
@polwayirbla
@polwayirbla 4 года назад
@@Dragrath1 Thanks for the very nice reply. Yes, this idea of the DM phase transition is very interesting. I would love to see more videos about it. I don't find very interesting anymore these"classic" dark matter videos where all you see is the flat rotation curve, the Coma Cluseter, the gravitational lensing and the simulation for large structures; but with no presentation of the results that are hard to explain with DM
@Dragrath1
@Dragrath1 4 года назад
@@polwayirbla Yeah videos rarely get into the in depth nuances around the subject since it seems a lot of scientists when discussing this sort of thing to the general public prefer to focus on the simplified models of the "standard explanation" Which it seems is often a decade behind the forefront research unless something breaks into the major media. Unless of course it is health or psychology where every single study gets blown up into an exaggerated claim well beyond the scope of the actual work which turns out to be statistically unsound anyway.... >_>
@jjusticenm
@jjusticenm 4 года назад
Please forgive if this isn't exactly on topic. But, thinking of the similarity of ocean waves and particle waves, is it possible for there to be particle currents and eddies in space similar to ocean currents and eddies?
@_siya.393
@_siya.393 4 года назад
Q.1 are we feel the gravity of dark matter or does light feel the gravity of dark matter , because there is change in frequecy of light as light escapes a gravitional field and gravitional red shift happen . Q.2 is dark matter consist of dark particle ,like that ordinary matter consist of atoms and blah blah or dark matter is just a field or wave that exibit gravity Q.3 how we came to know that there is only 5 % of ordinary matter in this whole universe sir please take this question in our next video . 😁😁and you are awesome man
@xennojeremy
@xennojeremy 4 года назад
So, it's aether folks. Easy to prove: M/M experiment was to test "static" aether wind, but the same "shield" that prevents solar winds and accounts for the aurora borealis, will also prevent testing aether wind; like measuring wind pressure on a car, with the sensor behind rolled up windows (no pressure). The theory still stands and has no other proven counter theory (look it up). The theory also explains dark matter and gravity; a weak electromagnetic force, like massive spheres spinning in water, mass attracting.
@meteor09
@meteor09 4 года назад
Could you tell us all the ways that physicists have searched for dark matter of various sizes in another video?
@yoavboaz1078
@yoavboaz1078 4 года назад
if electric charge is the charge of the electromagnetic force and color charge is the charge of the strong nuclear force what is the charge of gravity? mass?
@mohitsoni3275
@mohitsoni3275 4 года назад
Dr Don, how does measurement of time change over the last 14 billion years.. We were a dense state till 380K years, meaning higher effect of gravity and slower time, and gradually fastening as we expanded.. Come to think of it, is that a possible factor in the speed of expansion? Even if time is relative to observer, how will the photon traveling from early galaxies experience time?
@Mckeycee
@Mckeycee 4 года назад
Does dark matter interact with back holes the way “ordinary” matter does?
@JulianOnions
@JulianOnions 4 года назад
Yes and no. If it falls into a black hole, it stays there. However regular matter tends to spiral into the holes, giving off radiation on the way, which means a lot of regular matter can fall into a black hole as it is funnelled in, whilst only dark matter on a collision course will fall into a black hole.
@epzapp
@epzapp 4 года назад
Couldn't another branch be that our observations are bad or don't mean what we think they do?
@sunsparkda
@sunsparkda 4 года назад
I thought that the galaxies without dark matter observation is in dispute?
@pansepot1490
@pansepot1490 4 года назад
I heard the same.
@pilliozoltan6918
@pilliozoltan6918 4 года назад
To the answer to "Could dark matter actually be ordinary matter that exists in a different universe?" Assuming not one but more other universes their cumulated effect could be diffuse even if they are clumped separately. Also there are theories about gravity might travel across extra dimensions to explain why gravity is so weak.
@jaxzinremy4141
@jaxzinremy4141 4 года назад
Does the momentum of an object change the spacetime curvature of the object? If so, could kinetic information be transferred through spacetime geometry without the presence of matter?
@StratBlackFishRa
@StratBlackFishRa 4 года назад
"Do well in high school".. welp there goes my career plan. Ah well it's more of a fun thing to study on the side
@MuttFitness
@MuttFitness 4 года назад
Not sure if joking, but don't let the past limit you
@Saki630
@Saki630 4 года назад
Git gud
@nias2631
@nias2631 4 года назад
Meh, keep at it if it burns in you. My grades were not the best in HS. There are other issues involved too, yet I returned to school late in life. Today I am working on my PhD and enjoy mentally hammering away at mathematics while working on interesting questions. Sometimes its just a question of how hard are you willing to go.
@JotaFaD
@JotaFaD 4 года назад
Why do you need eletromagnetism for masses to clump together? Wouldn't gravitational attraction be enough?
@erikawanner7355
@erikawanner7355 4 года назад
Electromagnetism is A LOT stronger than gravity so not quite
@Vagolololo
@Vagolololo 4 года назад
This may be a basic question. But how did the universe end up with scalar and vector quantities, instead of being all one or the other? Or is it just an artifact of our ways of representing reality? Best regards!
@tensaisenshi
@tensaisenshi 4 года назад
Hi. I have a question that has been on my mind for years. Are the mass of the particles created by the vacuum oscillation considered on the galaxies mass/rotation calculation? Can they be the dark matter?
@Neos0en
@Neos0en 4 года назад
Could you recommend some good books about astrophysics and particle physics?
@isaach1447
@isaach1447 3 года назад
After publishing’s of Jan of 2021 Does it still seem likely?
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