Dark Matter's Not Enough Q&A

Why 'invent' dark matter rather than just adjust our understanding of the laws of gravity? Are there dark matter particles in orbit?
Following his lecture, Andrew Pontzen hosts a Q&A on the fantastically weird Universe.
The Universe seems to be governed by rules that we can, with some effort, understand. Andrew Pontzen introduces the stranger side of the cosmos - dark matter and dark energy - but then argues that these things are not so weird or unexpected after all. The strangest thing is that our rule-laden cosmos should be so predictable.
Andrew Pontzen is a lecturer and Royal Society University Research Fellow at University College London, as well as a musician and science communicator. His work focuses on galaxy formation and computational cosmology, as well as some early-Universe physics. Previously, he has held fellowships at Oxford Astrophysics and at the Kavli Institute for Cosmology in Cambridge. And now, he finds the time to go around the country presenting shows at science festivals.
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[@placeborick]

I love that he takes every question seriously even when from the young members of the audience. What a great guy

[@FreedomRoseStein]

You'd be insane to not add children to the mix when discussing scientific "Things" Because they very rarely are bogged down by "Things that make sense". So when they ask a question that wouldn't "make sense" and you can't explain how your "Scientific thing" agrees with it. It's not the child's fault it's the scientific things fault. "What happens if you freeze fire" is a good example. Depending on your level of knowledge you have quite a few answers to that question but then you have to explain how it works and if (Not in this case) You can't come up with a real answer that should be explainable maybe there's something new to research or discover. or your scientific thing might be incorrect or needing adjustment. TL:DR Kids ask the best questions because they challenge you to think about things a lot of people don't.

[@theshrubberer]

Agree, he has a great presence. He is clearly doing what he loves

[@user-jv6gi5fp2m]

@@theshrubberer I would say that children ask the most difficult questions , but not the best ones.

[@afrog2666]

I`m actually liking this Q&A more than the actualk lecture :p Very fascinating to see what the kids are asking, and I caught myself wondering if some of these questions were actually from "Dad" or if I was just not very scientifically "tuned" at that age, to put it that way. Long story short, sometimes i just feel dumb, and gladly so, it`s very nice to see children so young being interested in science at this level. It makes me think the future may not be as bleak as I and others imagine :)

[@jomen112]

I had the same feeling, on the other hand these kids might already have a basic interest in the subject to start with. The scientific debate on dark matter is not new and has been around for some decays among physicist. What changes is that more and more physicist become convinced by the evidence. The consensus among physicist today is that dark matter most likely exists, or at the very least, it is the best model (read: guess) they got right now. Now, recall how all the kids shouted 'yes' on the question if dark matter exists, this tells me these kids been exposed to these ideas since before. Point being, if these kids, out of interest, tried to absorb as much they can on the subject, they might have been exposed for these ideas for years already. Assuming this is the case, the question some of the kids had may not have been from dad at all. ;)

[@afrog2666]

Good point, besides, dark matter was not really a subject when I was a kid :p More people should take up an interest in science. There HAS been kind of a revolution in the field of science, regarding public interest. At least so it seems, that more and more people have greater knowledge and discuss things like particle physics, astronomy, electronics is also very much on the agenda these days, with laptops, smartphones, tablets, watches, and all sorts of gizmo`s and doodads so to speak. I guess there is generally more reason for the average Joe to have a keen eye for these things as it affects us more and more? Regardless it`s nice to see young kids interested in the world around us and actually showing up at lectures and so on. :)

[@tedl7538]

Hey Jan.....It sounds like these kids are already deeply immersed in a love of science, hence, I don't think they're just regurgitating their parents' questions as you suggest might be the case. More likely, they're potentially the Hawkings, Tegmarks, Greenes and Krausses of our future.

[@rationalmartian]

Let's not also forget that it is much MUCH easier to gain access to such subjects and information now with the internet being virtually ubiquitous. Going back roughly 20 years, one's only road was going to the library or buying books, except for the odd TV doc here and there, of varying quality and depth. For a child, it would be impossible to gain a basic knowledge and therefore any interest and then enthusiasm for a subject initially, unless an adult they knew was already interested. The internet has given us the most incredible gift and tool in this regard. Now one can simply dip into all manner of things, and follow what may be of interest, and at no charge, with no buggering about and with no delay even. It is great to see those young 'uns interested though, it really is. Though I sadly fear they may be in something of a minority. These RI lectures have really always been pretty top notch. And required viewing at Christmas for sure.

[@davidtrindle6473]

A Frog “future” is just an idea.

[@carlhudson83]

Wonderfully patient and attentive Q&A from Dr Andrew Pontzen.. Brilliant sir.

[@tedl7538]

Love these smart, charismatic kids, they give me hope for our future!

[@alanmclemore3927]

What impresses me is how smart these kids are--wow what good questions

[@wafikiri_]

It has nothing to do with age. In my country, there is no demeaning of children's intelligence just because they are children. And they are considered more sincere than adults, contrary to what is common in anglo-saxon countries.

[@anhedonianepiphany5588]

​@@wafikiri_ It appears that you're hindered by ignorance, and a significant lack of experience! This term you've created - "anglo-saxon[sic] countries" - is meaningless, and hence, requires definition. All we can reasonably glean from your comment, is that adults in _your_ country are intellectually impaired liars (and that you personally harbour a great deal of intolerance and resentment towards fair-skinned people, along with negative misconceptions and/or fantasies with regard to how they relate to their children). How ironic and shameful that you chose the space beneath content which helps educate and advance _all_ humans, to spill forth your divisive hatred.

[@briangalloway4193]

The kids are asking some very good questions. Great discussion, and good example of how we explore things we really don't understand. Better than burning people at the stake for asking inconvenient questions.

[@briangalloway4193]

***** Be completely humble and gentle; be patient, bearing with one another in love. Make every effort to keep the unity of the Spirit through the bond of peace.

[@David-tp7sr]

When you improve your computer simulations of the Universe to test your theories, how long before your simulation becomes so good that there are humans inside thinking they are real?

[@lorenzo42p]

forty-two

[@SoulmongerV2]

You took the red pill, didn't you?

[@alexojideagu]

Some hypothesis are that that's exactly what this universe is. Some even think there are more likely to be more simulations than real universes.

[@themadengineer1050]

anybody see that rick and morty about ricks microverse car battery? XD

[@TheAmethyz]

to be able to simulate something so precise it would require infinite amount of energy?

[@vespuzzi]

Clever kids in the audience

[@adithyaparupudi1336]

really worth looking this guy talk. Cleared all my questions. The audience were completely into it. I would absolutely love to hear more

[@nimim.markomikkila1673]

Referring to Dan Brown (w/Vatican) around 18:00:)

[@BofhJohn]

Have you tried turning the universe off and then back on again?

[@davidtrindle6473]

BofhJohn Funny!

[@hephaestus1956]

Thanks for the lecture, enjoyed every minute of it.

[@CrazyKraut20]

gotta love the audience member in the background @ 17:58 and onward with his "oh my god ?! " expression

[@kanchanatpheetankulratanap5474]

I really like him. He carefully answer the questions and explian with details.

[@rolandrick]

Brilliant presentation. 👍👏 Main feature and q & a

[@stewartcaldwell5299]

Dr. Pontzen, Regarding the unexplained expansion of the universe, could it not be that our area of the universe is shrinking and slowing down, thus creating the illusion of expansion ??

[@sheikmohamedamanulaa3898]

The redshift of the stars that were taken into consideration for the detection of accelerated universal expansion are almost 3 billion light years away over a period of 2 centuries...so considering the length of observable universe which is 13 billion light years, it's quite gud we say MORE THAN A LOT AROUND US is expanding faster every second

[@lemont2005]

Great job!!

[@newsboosters4902]

how does the continuous increase of dark energy - and empty space, square with the conservation of energy law ?

[@polkad3v]

Andrew Pontzen must have been so happy after this knowing that those kids are the next generation :)

[@danievdw]

Neutron stars are a good example of a lot of stuff taking up small amount of space.

[@mdansson]

Could dark energy be the energy released from dark matter annihilating with its anti-matter self? ~21:00 made me ponder this idea

[@dfaulk2660]

Have they considered that dark matter may have antigravity as a quality to it. If it was present from the big bang, It would spread out evenly between the stars except for the dark matter that would be accelerated out of the universe as the universe expanded, which would be moving faster than normal matter, initially it would have carried along a shell of normal matter. Since it wouldn't be found in the center of stars, it would consist primarily of hydrogen. The antigravity (-gluon) would accelerate the normal matter out of the universe since it would be denser the closer you got to the big bang since it would be confined by the shell of matter around it, and then dark matter in front of the matter in the universe would be less dense than the dark in front of it, causing the universe to expand? There's no reason it couldn't form normal covalent bonds, but it would, by definition, be excluded in the area where normal gravity is the strongest. it could also be output from black holes. if it formed in free space. this would eliminate the need to explain dark energy, and explain the difference in quantity of dark matter to normal matter.

[@souldancersbyjennifer]

I wished your question is seen by more..

[@freetrailer4poor]

The quality of the questions these kids are asking is good. Internet is amazing you get a 100x increase in audience by posting on youtube.

[@alexbowman7582]

What if complex gravity fields bend space outwards do that things fall apart.

[@damn_right_man8606]

Current (very fresh and new ) measurements revealed a much higher mass of neutrinos. Would this be enough to entitle them as the missing mass in the universe, and therefore get rid of dark matter ?

[@maxdecphoenix]

It's amazing how what makes the universe interesting is how some things don't respond to everything. Like if nothing obeyed gravity, we'd never be here. But if everything obeyed gravity, we wouldn't be here either. Like photons. Photons have no mass, so do not respond to gravity. They operate in space time, which can be manipulated by gravity, but not to gravity itself. If they did, light would have a finite distance. Our apparent horizon would be small, and the universe would only appear to be as old as the maximal distance covered by light emitted from the oldest star nearby. Dark matter, obeys gravity, but doesn't respond to electromagnetism. Spacetime compresses in the presence of gravity, but not the EM field, but expands exponentially in low gravitational regions. Like an inflating balloon with tape on it. The tape prevents certain regions from expanding, while the rest of the surface expands.

[@joppadoni]

ive always thought that we can simply say the mass of a black hole at the centre of a galaxy can be calculated by:- mass of the galaxy based on angular velocity - mass of the galaxy based on the light emitted.

[@daledelatte9607]

The problem is that the black hole at the center of most galaxies is way to small to explain the holding together of said galaxies from our observations

[@puedojoe]

Could dark matter be perhaps made of phlogiston, and dark energy be composed of aether?

[@herojig]

I would have asked, are black holes (that are theorized to be at the center of most galaxies) being taken into consideration into any of this math. And how does one count for the excretion that we don't understand, and where any of this matter is going as it circles down the drain?

[@tarekrahman1]

Those kids are our hope. We need to attract our child into science in order to continue science.

[@KoaBosk]

what if dark matter is not a three dimensional particle but a fourth-dimensional particle and the reason why we can't, see, catch or contain them is because they're traveling through 4th Dimension

[@stefanhensel8611]

It should still react to electromagnetical, weak and strong forces -- unless these three only work in our known 3 dimensions (an idea I got from Brian Greene, iirc). It has been speculated that dark matter is "normal" matter from another, but very close universe, and that the two universes influence each other gravitationally (so that our normal stuff would be dark matter over there).

[@chezeus1672]

doesn't really matter which dimension you call time. i think the theory stefan hensel mentioned can be explained with a lower dimensional analogy: think of our universe as a (very thin) sheet of paper, and gravity is (wet) ink, particles etc. are the change of shape in the paper when you put on the ink. now, you bind those sheets together in a book. the ink spills over to the other other sheet, while the change in shape in undetectable as long as you only see one sheet. this can also explain why a way bigger chunk of gravity originates from dark matter; it just comes from many parallel spaces tightly packed together. in mathematics, more dimensions than 4 are quite trivial, first semester stuff. there's nothing magical about the 4 dimensions of spacetime other than the fact that we experience them directly.

[@alangarland8571]

Well of course you can say 'what if?' about anything. That doesn't make it either true or false until you some evidence of it.

[@ashutoshadukia9117]

Well first thing u do realise that 4th dimension is spacetime so any motion in spacetime can be detected in your normal world...actually there is nothing new we are talking about motion in fourth dimension is the motion which u perceive in day to day life, things which move because of gravity actually move in straight paths in 4 dimension which is a curved path in 3 dimensions and that is what u see .....so this even if dark matter was moving in fourth dimension u could still see it moving in 3 dimension known space it just would have a different trajectory.... And if u are trying to invoke like another space dimension rather than the spacetime which Einstein discussed then we don't know

[@johnbrown6347]

The 4th dimension (time/space) could explain both dark matter and dark energy. We know the one and as far as we know only thing that affects time is gravity. The more gravity the slower time ticks, a tick can be thought of as how quickly time goes by. The speed of light is 1 tick and nothing can travel fast er than the speed of light. However if I am in a gravity intense region of space and I look out to a less gravity intense region of space it would appear that light is traveling at 2 ticks rather than 1 tick. This would in a effect (if not accounted for) appear as space was growing at faster than the speed of light, i. e. dark energy! Dark matter would be a side effect where it appears that within a gravity cluster things on the inside is moving slower than things on the outside. Kinda like a top spinning with little dots painted on it, the stars on the outside edges of a galaxy would appear to be moving so fast that they should fly away. Where in a equal time frame they are actually moving slower than the stars on the inside nearer to the gravity center. The appearance of speed is due to the difference between the time frames. While those on the inside is moving at 1 click thoes in the middle are moving at 2 clicks and the ones on the outside is moving at 3 clicks. As an observer it would appear that the stars on the outside could not be moving that fast and not fly away unless there was a greater concentration of matter that could not be seen i. e. dark matter. In short time dilation explain both dark energy and dark matter due to the speed at which time ticks for a given amount of gravity. This time dilation should not be confused with time distance such as the light year which affects observations at a distance. Time distance explains how much time it takes to see an event at a distance, time dilation affects how many events can happen from the observers time reference compared to the events time reference. Both should be accounted for when observing non local things.

[@fanculo619]

is it possible that dark matter does not exist within our dimension physically but influences and is influenced by our own dimension and if so would it even be possible to get a physical reaction from an extra-dimensional source?

[@kimsland999]

He answered this question, he said we would also see influences on standard models which we don't, therefore it must be its own particle.

[@curofbadenoch4301]

I haven't finished it, so I don't know whether it's been answered, but what if dark matter is nothing more than us being lighter on the galaxy side and most galaxies being made out of heavier elements?

[@chezeus1672]

not very likely. look up astronomical spectroscopy. we can determine what other galaxies consist of. and even if that method was somehow flawed, it takes a while until the light from distant galaxies reaches earth. to get more heavy elements, you need more time to fuse them together; we know the elements in far away galaxies are, on average, lighter than in ours, simply because the matter is younger.

[@themadengineer1050]

furthermore could such things of random probability shown in quantum physics and dark matter explain human x factors in any mathematical equation and even the paranormal? seems like effects of dimensions we might not yet understand but are beginning to grasp at just as a fish does not know what the tide is but yet moves with it. does the fish question how? probably not, but it is still a conscious being that continually makes "unpredictable" movements becoming more unpredictable and varied the further time goes on from the original model of the prediction

[@seanjoseph8637]

Also, the expansion of our Universe is accelerating, could this not just be due to inertia/momentum from the "big bang"? (I've since learnt that the expansion slowed down for a bit then started speeding up so this is wrong and irrelevant) Or our Universe is surrounded by other Universes and is being influenced by the gravity from those other Universes...and vice versa!

[@littledockens]

I haven't read up too much on the subject of dark matter, but it has been invented to explain the accelerating expansion of the universe. What if, outside our universe, there is an all encompassing attractive force, would that explain it?

[@tbirdtadhg]

Just when you think its great that a 10 year old is asking questions, a 4 year old pops up

[@Nehmo]

+tbirdtadhg Do they all have to have that silly pretentious accent?

[@awuma]

"Invisible matter"... Dark Matter used to be called "missing mass" from the 1930's until the 1980's. Our terms get more precise ...

[@steve25782]

I wish someone would comment on how much of dark matter could be in black holes. They could be in places where there's not stuff falling into them, which would make them visible.

[@69ElChistoso]

Why can't it be that this dark matter is just a bunch of primordial black holes floating around in the galaxies?

[@georgeyoussef9906]

Need to watch the actual lecture but the Q&A have some cute audience questions.

[@landonsmithers8553]

Could dark matter, and separately but similarly dark energy, be a directional wave, instead of a particle (sphere)?

[@anhedonianepiphany5588]

All waves are "directional", did you mean a longitudinal wave?!? Regardless, the stuff we consider to be waves is energy, which lacks mass and thus can't be dark matter (which was discovered/labelled due to gravitational effects). Neither dark matter, nor dark energy, have been physically detected, only their effects have been observed, so they certainly aren't any kind of wave, or particle, as we understand them.

[@PongoXBongo]

Could dark energy be like a reverse gravity? Like a bump in space-time instead of a well.

[@kimsland999]

This would go against the laws of gravity, therefore no.

[@maxdecphoenix]

No. At least as is been explained by Lawrence krauss. Dark energy doesn't have any appreciable effect on gravitationally bound entities. Like two planets bound gravitationally, are not expanding or accelerating away from the other. The solar systems with in a galaxy are neither expanding nor accelerating. And even tidal locked, multiple galactic super clusters which are so dense they lense light itself are not expanding nor accelerating. Dark energy is only appreciable between objects which are so far apart they are not bound to one another. And the space itself is expanding, its not just a repulse force like magnets, it's the actual space itself growing, and faster. This implies that force delivered by dark energy is a much weaker than gravity. It's like two boats on an expanding ocean. The molecules of each boat are bound, they will not accelerate. You can throw a rope from one boat to the other, and the molecules of the rope will not accelerate. But the ocean around the boats grows. If you have a third boat on the horizon, not tethered, eventually the ocean will be expanding at such a rate that the third boat could never generate a speed fast enough to ever reach the other boats.

[@ElektrykFlaaj]

@@highgamer4957 because the further an object is from the Earth, the faster it is moving away from us, and the relation is proportional. 2 stars opposite to each other from the Earth, when are at the same distance away, will move away from us with the same speed. It would appear just like we were exactly in the middle of the Universe, but we're obviously not. This can be explained by the fact that space just grows out of nothing with the same rate everywhere where the gravity force is almost non-existent. Stars and everything apart from constantly moving away from us, also constantly accelerate away. It's because the more time passes, the more space there is between objects. And the more space there is, the more space grows with the same rate, but the sum of the growths is increasing, because the amount of space is increasing. Hope I explained it somehow, I'm always having problems with speaking my thoughts in an understandable way

[@alexbowman7582]

So why can't the effects of accumulated gravity bend space outwards and cause objects to fall away from each other?

[@rationalmartian]

Would that not merely be anti gravity? As far as we are aware no such force can be created. What would it be? How would it become repulsive? The closest thing we have to such an idea is the proposed Dark Energy. That is a "repulsive" force. But it doesn't work like gravity. Gravity is more effective at close proximity, with the "strength" of the force falling off with the inverse square law. Dark Energy does not seem to follow the same law.

[@luisfelipe7351]

Like só massless that is negative like the graviton?scarse down here abundant elsewhere?

[@axiongoblininterests1280]

if black holes don't get hit often whats the chance of dark matter hitting xenón predictably?

[@boonchongpp]

There mirror image for normal matter called antimatter ,then will there be a mirror image of dark matter (i mean will 'anti' dark matter?)?

[@pekkoh75]

He answered it, said that they thought (not sure based on what) that dark matter might be its own antiparticle (so two dark matter particles would annihilate each other if they collide)

[@andreasfehlau4965]

I find it a bit peculiar that my five-dimensional physics has been around for over 30 years and no one is allowed to talk about it.

[@erikziak1249]

I am thinking now about, and this is related to dimensions, do we have any evidence that dark matter actually forms "flat" spinning "discs" around (and inside) galaxies. If we assume that the conservation of momentun applies to dark matter too, then in three dimensions, this woudl be the case. But what if dark matter has actually four spacial dimensions to move around? Coould it even interact with our three diemensional space? If somebody can write this down mathematically, is there an equation giving four "macroscopic" (not just on subatomic scales like string theory) spacial dimensions to dark matter "particles" (?) that would actually yield the same results that would explain what we observe? I guess I have a very hard time to write my thoughts down in a way that is understandable... Well...

[@tonyspilotro2598]

Flat galactic discs are created by collisions between normal matter, the 2 dimensions of the disc being roughly the plane of the average angular momentum of the matter. Dark matter would form an approximately spherical halo around a galaxy as it does not collide with itself or normal matter. It is not thought that there is another extensive dimension of space. String theory predicts other dimensions, but all these extra dimensions must be smaller than a millimetre.

[@erikziak1249]

+Tony Spilotro Yes, I agree, that is exactly my point the "spherical halo of dark matter" as you wrote. From our "3D" framework, would we even be able to comprehend a "4D" structure? Imagine if you were "flat" 2D, how would you think about 3D. I am not a great fan of string theory and the reason why I wrote it is just pure speculation. Please excuse any weirdness, I have zero formal education and am guided only by my intuition and reasoning (which might be a fallacy as well). The reason why I wrote the original idea is that it might (or not) explain the why we cannot see dark matter (in our 3D framework) and why it interacts the way it does.

[@tonyspilotro2598]

Erik Žiak Don't worry, a lot of physicists have wackier ideas than you! Nothing wrong with thinking outside the box, or in higher dimensions.

[@erikziak1249]

Tony Spilotro Maybe, but they can at least write some mathematical expressions which forms the fundaments they can build on... Too bad that my knowledge of maths is so poor. Well...

[@ReplicateReality]

but what if theirs a special proporty to light that is afffected by something other than the gravity adding to the lensing effect and the idea of more gravity, what if its just another force like gravity that is bending the light

[@giljorge7479]

That joke about blowimg up the vatican was on point

[@boonchongpp]

Black hole had a tremendous strong gravity force,so it also had a lot of dark matter around it?

[@Giraf1964]

Dark matter, Dark energy = God of the gaps arguments.

[@geeta172]

If there is so much stuff in space...how do you draw your boundaries? How do you know where one galaxy ends and another one begins? Is that random too?

[@DaddyThePro]

Id say you cant know for sure but you can have pretty good aproximation, we can calculate how much dark matter is in the galaxy and how it should be distributed in the galaxy using galaxy spinning speed, thats one of the reasons dark matter was invented for, to acount for extra speed that galaxy's are spinning at.

[@chrisofnottingham]

They tend to be well separated but the word galaxy is like any other word, if you probe at it's limits it will have difficulties - how much of a car do you have to remove before it isn't a car?

[@robertbrandywine]

There isn't that much stuff in space, actually. If you spread matter out evenly it amounts to only a few atoms per cubic meter. My understanding is that galaxies are separated by significant amounts of almost empty space.

[@faarsight]

I wish it was easier to hear the questions

[@totakuraanil2921]

if dark matter comes close a black hole will it be setteled around the black hole as the black hole has infinete gravitatinal pull.if it does then is it possible that the black hole is made up of dark matter?

[@StephenPaulKing]

Could dark matter be composed of planck mass black holes?

[@David-wc8ze]

Second viewing - this is interesting.

[@shortcutDJ]

shit, i wish i could ask this question (humer me it's not very scientific) What if you were able to scoop up a hole bunch of dark-matter particles, could you squeeze/manipulate them so that they would form 'regular' matter particles?

[@stefanhensel8611]

If you taught them to interact via electromagnetical force, maybe.

[@chezeus1672]

for all we know, after scooping up a whole bunch of dark matter particles you can put them into a lamp and rub on that lamp to call a djinn. in other words, since it's unknown what dark matter really is, nobody knows what you can do with it.

[@stefanhensel8611]

We should definitely try that ;)

[@percih70]

Is it not that the dark matter in the current model doesn't clump like normal matter, hence why there is no talk of dark galaxy's , or perhaps more correctly we need our dark matter not to clump together for the model to work.

[@themadengineer1050]

is it possible dark matter particles are tiny singularities leaving them with infinite mass in comparison to their space like black holes of the atomic world? or perhaps even tiny quasars that emit particles so small we can not track them yet? is it push or pull that expands the universe at an accelerated rate and is this what is affecting our exponetial progress as a species? also that guy in the blue shirt has looked shocked through out most of this information XD he is probably thinking the same as us all....there are a lot of smart kids out there

[@kimsland999]

Science has moved from a singularity theory to an eternal past universe or multiverse. Therefore I don't think they are multiple singularities!

[@seanjoseph8637]

Maybe I'm being simple and/or the lecture was kept simple, but, if to begin with the stuff in galaxies was calculated by the light it emitted then later by the calculation of stuff was made more accurate by observing the rate of spin of the galaxy showing more stuff. How was the amount of stuff that doesn't give off light, like planets, asteroids, comets etc. taken into account using the light measuring method?

[@SoulmongerV2]

The non-luminous stuff is accounted for in the measurement of the rate of spin. Also, the non-luminous stuff is comparably insignificant to stellar masses. For example, the Sun makes up over 99.8% of Solar system's mass.

[@seanjoseph8637]

I understand that, but the non luminous stuff was not accounted for when the original calculations were based on light emissions, that is why the spin rate calculations found that there was more stuff. I understand the Sun makes up most of the mass of our Solar system, but is that typical of other systems? And the stuff that isn't our Sun, is still a sizeable amount of mass. If all systems have similar or more non luminous stuff then could that account for the missing mass that is called dark matter?

[@SoulmongerV2]

Sean Joseph No, there's simply too little of it. For example the mass of our own galaxy is estimated to be over 90% dark matter.

[@seanjoseph8637]

How is the estimation done? I believe in simplicity. If the calculations show there is more mass than we can observe, then there is more mass and we just aren't capable (yet) of observing that mass, I don't think it will turn out to be a mysterious "dark matter", I think it will turn out to be everyday stuff that hasn't been accounted for because of our inability to observe anything at distance that is not luminous.

[@SoulmongerV2]

Sean Joseph physics.stackexchange.com/questions/1008/why-isnt-dark-matter-just-matter Literally the first link from Google search.

[@JoelMurphy77]

Even though he'll probably never read this, I'm answering that young man who said, "they're both dark!" There's a bright lad who carries a bright torch. Are the lad and torch related, or are they just in the same place?

[@chriswilson296]

drrrrrrrrrrr! how long does it take to boil an egg using only strong acohol! my dad was a coal miner so i can use a spade! but i haven't done the maths on that subject, also i think some of these uber kids are going to have problems later similar to there forebears . .

[@boonchongpp]

Dark matter doesn't feel the normal force ,does this force differ from the for we knew (gravity force, electromagnetism , strong force and weak force) ?

[@anhedonianepiphany5588]

Dark matter is only known to interact gravitationally, and seems unaffected by other known forces.

[@10limmathgen69]

If dark matter particles are unaffected by electromagnetic forces and only react to a gravitational field then it stands to reason that dark matter energy could very well be a field much like the Higgs field. If the universe displays a significant continuity of the symmetry with respect to forces, then a Dark Matter field would act inversely to the Higgs field; instead, the earth would pull upon the dark matter particle and the dark matter particle would fight the gravity of earth. It would then stand to reason that early in the life of the universe dark matter may have been accelerated or slowed due to the high concentration of mass or the concentration of dark matter. Currently the velocity of the average galactic amount of dark matter attained from the start of the universe may still remain dependent upon what the actual affect gravity has upon it. The greater the reaction that the gravitational field has upon the dark matter field the greater the velocity of whatever mass is related to the dark field. It just may be that the 5x difference in mass you calculated by rotational velocity is related to the strength that the Higgs Field and a Dark field exhibit. So, it may be that the galaxy you're measuring isn't really 5x more massive but only appears to be due to the acceleration affect dark matter has as inverse gravity against normal gravity.

[@justthefacts1910]

+CARL SNYDER However dark matter by its very definition is affected by the Higgs field. Also there isn't a concept called dark matter energy - I think you mean just "dark energy" which is a completely different concept to dark matter. Dark energy is repulsive not dark matter which is attractive. As the lecturer describes, dark energy doesn't seem to have particle like properties to it.

[@dfaulk2660]

There's also the possibility that dark matter is composed, not only of an anti-gluon, but also antimatter. the Earth would be protected from it by the massive gravitational field of the sun,

[@anhedonianepiphany5588]

I wonder whether you liked your own comment, or if it was somebody who mistakenly thought you sounded like you knew what you were talking about?!? There's so much fundamentally wrong with your comment that I'm thinking it's either a joke, or the Dunning-Kruger effect!

[@kestutisnikolajevas9870]

so, if dark matter is not interacting with matter or is visible how does it have 5 times more mass then matter

[@hephaestus1956]

Because it only interacts with gravity, thats why we know it's there.

[@XYsk8ter4lifeYX]

couldnt the extra mass of galaxies be explained with a black hole in the centre of the galaxy ? Or is the mass of the black hole just not big enough (if we even are able to be sure of that mass)?

[@12345DJay]

the moment you realise some 12 year olds are smarter than you . not sure if i that should make me proud or sad....

[@maxdecphoenix]

12345DJay it should make you cautiously optimistic. They could be more knowledgeable, but less intelligent. If they're more intelligent, they could solve problems you couldn't and make your life easier. The problem arises when people are too intelligent for their own knowledge. Like sometimes intelligent people create things that are supposed to make your life easier, but end up making it worse. Nuclear weapons, for instance. But it's actually any weapon. Weapons are great when you're the only one who has them, its when other intelligent people see and copy them that it stops being good. Intelligence is creating weapons, knowledge is knowing you probably shouldn't.

[@siddhusiddhartha4692]

Just a quote "knowledge is knowing that a tomato is a fruit wisdom is not putting it in a fruit salad " By miles kington

[@RoyFultun]

Comparisons are odious. Especially when one over 30 compares oneself with a 12 year old.

[@Capiert]

Siddhu Siddhartha That's a great idea! I will have to try a single_fruit salad & see what fruit, a tomato goes well with, & why it does not go well with most (other) fruits. Great Ph.D thesis! (Double blind study). I remember a high_school teacher's party, she had (creatively) put oranges (mandarines) into the lettuce (salad) & I was surprised how good it tasted. (Maybe it works with tomatoes, too?) I would never have dreamed of doing that myself. Maybe that's it? Would cherry tomatoes work? (I guess it depends on their tree (sap).?)

[@larslrs7234]

The answer "Modified gravity answers not everything that dark matter answers" is ridiculous. It doesn't have to. What it can't explain, has to be explained with something else. It's like saying "The lord makes the light and the lord makes the apple fall to the ground." Then I say "The sun makes light" Then you say "Well, we could use the sun as an explanation for the light, but the sun doesn't explain why the apple falls to the ground. So we better stick with the lord for both". Also, modified gravity isn't even required, just another perspective. Just consider the amount of expansion of space on a galactic scale. It's not zero.

[@curiositygene]

Instead of Dark Energy to explain the fact the universe is expanding at an accelerating rate, why not prior big bangs creating prior universes that now have matter further away (potentially all dark) that pull via gravity the "known" universe from afar, hence accelerating our universes' expansion?

[@codeincomplete]

+Curiosity Gene Think of the raisin bread analogy. The bread is expanding where the distance between the raisins is increasing (at an accelerating rate). If you superimpose a second universe (what you call a prior big bang), that is able to interact gravitationally with our universe it would not cause even expansion as the raisins would be in a different locations. See also common objections to the many worlds interpretation (MWI).

[@luisfelipe7351]

I posted gere before can not ser my comments...but anyhow...If someone proposes a different speed for gravity And nothing changes it wouldn't be wrong...but If It is wrong what would change?

[@luisfelipe7351]

Darkmatter isn't negative mass ?

[@natielgavi]

Does he do birthday parties?

[@TehJumpingJawa]

What is the relationship between dark matter and (normal) energy? If dark dark matter interacts with black holes in the same way as regular matter, doesn't that mean black holes are actively converting dark matter into (normal) energy through hawking radiation? That feels like it'd have serious consequences for the evolution of the universe over long periods of time.

[@kimsland999]

Yes the evolution of the universe states that black holes eat everything and are therefore at the top of the food chain and therefore will be the last thing standing until even they dissipate. If there were a reason why everything is here it would be because of black holes :D

[@luisfelipe7351]

Couldnt darkmatter bem the imaginary counter part of matter?

[@ThatGuyKappa]

Quantum physics is the observation of equal trade of information btwn dimensions...........The theory, or (FACT) of everything is basically "Dimensions of Information" what do i mean by that i mean due to the law of conservation energy and information we are energy, our dimension we live in have energy, and matter is energy, and due to quantum mechanics and physics of it, it all points to one thing only and that is .....(information) for matter,energy, and life would be without structure, and what is structure but fundamentally information of how it's constructed via quarks, then the numbers of protons and electrons................quantum entanglement is basically equal trade of opposite values due to the law of information conservation, and energy conservation.......now about the two slit experiment creates an interference pattern without observation, but with observation we as living human beings are basically a form of energy, and energy/matter form that also has information like in the form of (DNA), and DNA is what makes us beyond just matter and makes us living, and since we and the world we know around us is all still basically structure of information we by observing it involve and add ourselves or rather add probability of information into our dimensional structure of our world conform it into predictable fact our information structure and the laws that follow our structure of information.....so in essence it's like this equation: (information probability) is the variable (IP)+Structured frame of Information=(ID) Information Defined, and thus to you all creationists and people who believe there is a creator you are wrong, but alas and i digress different strokes for different folks, you choose to believe whatever you want that pleases or eases your mind. I await the noble prize, for the facts we observe of quantum physics mechanics is fundamentally the glaring proof in front our very eyes, i understand it. Any fact given to someone can be useless unless it can be understood and then believed......i really hope someone can understand what im talking about cause it is the only way for one to truly appreciate there own grasp of it.?

[@Duongy94]

undetectable matter?

[@19markz67]

What if dark matter particles are incredibly large? We are looking for the micro but instead should be looking at the macro level.

[@akronymus]

19MarkZ Large particles would interact, would be seen, at least their shadow. No. I rather thing, DM is not a particle but some strange energy field we do not know of. Think of Higgs field, very strange, as well.

[@19markz67]

I am not a scientist. This is a layman's fascination with the topic. However, think much larger. My hypothesis is that dark matter and energy is at a scale we cannot yet detect. It is like the difference between the subatomic world of physics and the scale of the the known universe. Scale up the known universe by the same factor or more and it pervades everything. Are dark matter particles/energy actually passing through the entire universe and if so what direction are they traveling? Or is it all encompassing? Literally, think outside the box. Food for thought.

[@19markz67]

akronymus See my reply in the comments. Thanks for the response.

[@whitenight941]

As usual ;That's one less Thing" we have to figure out .Soon Another and another !

[@anhedonianepiphany5588]

Uh, yeah, there used to be a lot more! The point you're attempting to make is ... ???

[@AbhilashKS91]

Talk says that the Dark matter can be present on the earth as well ; but then why the gravity of the earth remain constant.. Why the dark matter on the earth doesn't affect the physical parameters that we measure on the earth.

[@michaelzito3170]

Abhilash K S If dark matter exists as they are postulating, then there is a large 'cloud' of it permeating our entire galaxy, with the constituent particles of dark matter constantly moving through everything in the galaxy, stars, planets, you and me. That means here on earth, we are existing within this enormous 'cloud' of dark matter. The dark matter is like a ghost in that it can penetrate into things. Thus, here on earth, we are surrounded in every direction by dark matter. It is all around the earth penetrating into the earth and everything on the earth. There actually would be a pull from the dark matter on us. However, since it is all around us in every direction, the pull from the dark matter above us is cancelled out by an equal pull from the dark matter below us. Similarly, the pull from the dark matter in front of us is cancelled out by the pull from the dark matter behind us. In any direction you can think of, the pull from dark matter that we would feel is cancelled out by an equal but opposite pull from dark matter in the opposite direction. Hence, here on earth, these pulls cancel out and we feel no net gravitational efffect.

[@factsheet4930]

But if dark matter can go through small spaces and dodge everything, I would assume it could get really arbitrarily close to other particles, and the force of gravity could get really strong, trapping the dark matter particles, perhaps even creating mini black holes..?

[@12345DJay]

+marco polo well the force of gravity is ridiculously weak. it's the weakest force there is. in fact, it's 100000(i think, maybe 1 million or even more ) times weaker than the electromagnetic force, in addition to that atoms for example are not held together by gravity in the first place because it plays such a miniscule role on such a small scale we only expierience gravity on this scale because earth is so huge. so if even earth does not have enough gravitation to trap dark matter particles, particles certainly can't. Since -as far as he said and as far aas we know- dark matter , if it exists in this theorecital way in the first place, is only affected by gravity it makes it really hard to measure interactions with particles we know. also dark matter particles are supposed to be really really small but incredibly massive for their size so even if gravity would play a major role on a subatomic level if anything, dark matter would affect particles, not the other way round. on another note, if dark matter would create mini black holes if it interacted with regular particles everything around that interaction would be vaporized basically. even if the tiniest of black holes would appear next to you, you would die. and probably earth with you but i'm not sure about that.

[@factsheet4930]

12345DJay I know that, I only say that because gravity is the only force that could effect dark matter, I was talking about really close encounters, and technically, the mass energy of that black-hole if it would be created would be less than that of a black hole with Planck length as its radius, so either that is by definition not possible or perhaps naked singularities do exist :p

[@SoulmongerV2]

The difference between electromagnetic force and gravity is actually somewhere around 10^40 (for electrons at least).

[@jeffreystroman2811]

How seriously have astrophysicists considered space time is on a gradient from the perspective of either the observer or bodies being affected? Perhaps a step back and a cat alive or dead scenario.

[@oneindelijk]

If mass is not a property of matter, why are we speaking of the mass of dark matter ? Could dark energy be created from the stretching of space, like a vacuum transforms into dark matter, much like matter is transformed into energy ? This could be an avalanche effect, with the newly created dark energy increasing the expansion of space ?

[@kimsland999]

Although Dark matter may now NOT be particles (just new research om this) Dark matter that is commonly stated as a particle IS made up of tiny mass. Dark matter and Dark energy are 2 TOTALLY different things that each describe the reality of what observations we see. So having both Dark energy AND matter in your question makes it too difficult to answer. The avalanche effect is NOT picking up unknown free energy out of nowhere. It is picking up more real energy of real matter and through the calculation of momentum can get really big BUT it MUST dissipate over time once that energy either reaches too much friction or the consumed energy runs out.

[@ujjwalsingh6945]

If dark matter is that tiny and has a lot of mass then, why doesn't they stick up together by their own gravitational pull and become black hole??

[@jarirepo1172]

Even if there were a black hole made by dark matter, why would it be / act any different from normal black hole?

[@adsjar]

i just wish i was there with my kids.

[@Azarothpng]

What if the universe ain't expanding at an accelerating rate but that the speed of light is increasing and everything just appears too expand faster since later light reaches us earlier than expected? Like speeding up the movie.

[@justthefacts1910]

+Azarothpng No...basically you would be saying that special relativity is completely wrong and that GPS doesn't work. The speed of light is actually not about light - it is the speed of causality and it is the speed of all mass-less particles including photons. Changing the value ends up being a Lorentz violation. A lot of the laws of physics use this constant so it would not be just speeding up a movie. The change in the speed of light in the past would be something that was VERY observable in the sky.

[@moking1761]

Sorry but correction coming. Photons are affected by gravity and the direction is bent therefore ERGO photons have mass. This effect can be seen in 'Gravity Lensing'. Good article on Wikipedia.regards MoK

[@maxdecphoenix]

Mo King no, photons operate in space time, gravity effects space time, but the photons inside it are not. It's like paper, rock, scissors. Gravity beats space time, space time beats photons, photons ignore gravity. If gravity had any effect on photons, they would slow. Even the most infinitesimal amount of mass would present over the massive time and distances. Eventually they would slow to the point a significant body bound them up and accreted them. Since space is infinitely large, and stars are at very far distances, then we could expect earth to be at the extant range of light from those far stars and observe far light slowing, and farther light stopping. This is not the case. This is not observed. We do not see light slowing, nor stopping. Light from the most distant galaxies still travels at the same speed, otherwise we would not see it, because it would have ceased to be light.

[@earlofdoncaster5018]

Could dark matter be virtual particles?

[@kimsland999]

No they must exist as we have observed their reality in galaxies.

[@earlofdoncaster5018]

Virtual particles have real mass.

[@energyshandrew2854]

Light screen

[@Ninjahat]

WHAT IF dark matter is so tiny and is travelling at such an immense speed (faster than light) that it cannot enter the center of a galaxy (where normal mass is) and the only way to detect it is by travelling to the far edge of the galaxy? WHAT IF this immense speed of dark matter combined with it's enormous mass is actually carving such a huge "hole" in space-time that it itself is pushing space-time apart and thus creating the phenomena you think is dark energy? WHAT IF the super-massive black hole at the center of a galaxy is creating dark matter when "eating up" normal matter and spewing it out into the bubble around the galaxy via the super-massive black hole's polar jet-streams? PLEASE do these thought experiments with you vast knowledge of physics in mind. PLEASE try and combine these three postulates and do the thought experiment. @The Royal Institution

[@theeddorian]

Modified Newtonian Dynamics

[@Xxoax]

Quantised inertia.

[@kwanarchive]

You may as well ask "what are birds?". What ARE birds? We just don't know.

[@kimsland999]

Evolved dinosaurs. Evolution of life is NOT under any question whatsoever.

[@anhedonianepiphany5588]

@@kimsland999 Yeah, not exactly, but close enough! It's a good "I've seen Jurassic Park" answer, though.

[@timsloanihi]

Did it occur to you that this question can never be answered on earth?

[@dfaulk2660]

That would also explain why interstellar travel is so difficult!

[@TheKrazyLobster]

OKay, found it

[@donhillsr1466]

dark energy = Planck size particles surrounded by energy causing it to vibrate at 10^35 Hz filling the universe with billions per cubic centimeter in seconds. The density changes depending on the matter or "empty" space they are always in contact with each other. The vibrations are converted to energy by fission and fusion universe is expanding at an increasing rate, pulled apart by the vacuum of farfarfar far outer space as the pull of gravity of the residue of the big bang's black hole lessens as the distance increases it may never be seen it is attracted by the masses nearby and follows the gravity field of the galaxy, all the matter passes through the field and is modulated by energy and demodulated by solid matter. Passing through the black hole it reemerges completely demodulated. through the sun or other energy sources it is again modulated PLUS

[@justthefacts1910]

+DON HILL sr Congratulations on your Noble prize!

[@dfaulk2660]

I meant anti-graviton not anti-gluon.

[@Censtudios]

Anti-dark matter doesnt make sense because dark matter has no electrical charge, no?

[@joppadoni]

+Censtudios surely you're correct, sort of.. if it doesn't interact electrically it cannot have charge. However if we assume dark matter has properties, anti-dark matter would simply have whatever the opposite of these properties are.

[@Censtudios]

joppadoni I thought it would mean that anti-dark matter would have the *same* properties, just with the opposite charge. But dark matter has no charge.

[@Oz1888]

+Censtudios neutrons have no electric charge, however antineutrons exists. I guess that answer your question. If there is indeed a particle of "dark matter" they would be an opposite particle.

[@joppadoni]

Oz1888 indeed, antineutrons are made up of antiquarks, rather than a simple opposite charge.

[@Oz1888]

+joppadoni antineutrons aren't elementary particles indeed, but since we don't know what "dark matter particle" is you can't rule anything out. But any elementary particle with no charge such as photon, gluon, higgs boson are their own antiparticle.

[@ursiny33]

Dark matter is the parts you need to construct a proton for a hydrogen atom, space is an environment of dark matter particles, our hydrogen atom based atom universe is traveling thru this environment in its expansion with trillions of objects with rotating magnetic fields which means we have trillions of magnetic induction environments traveling thru this dark matter field of space, dark matter is a nuetral conductive particle,this rotating magnetic fields bathe these dark matter particles with charged particles called electrons, the stick to dark matter ,this turns them into sub atomic magnetic energized dark matter particles with a magnetic field ,they are then attracted to another charged dark matter particle in this induction environment to bond with each other making an electromagnetic bond of charged particles and dark matter producing a new proton thru induction at the point of this bonding it captures an electron to orbit it that makes a magnetic field bubble that envelops and seals that protons inducted electromagnetic bond to create a self sustaining hydrogen atom, this is the electromagnetic mechanics that constructs them, when these atoms become stars, the star collects this dark matter in its core everytime it takes an atom apart, the dark matter can't escape the core, when a star is young and doesn't have a large supply of heavy element atoms around the core the lighter atoms are taken apart in the core a d that makes the charged particles. Coming out of these atoms from the heat and pressure in core breaking the structural limits of these atoms into super hot radioactive charged particles,they are so hot ,they can't join the magnetic field lines in the stars field they are trapped in the core as a super hot plasma field of particles ,the dark matter that held the charge in the protons can't escape either its blasted on the plasma chamber wall, and over time it piles up into a separating dark matter containment wall between the plasma field and its atoms of fuel,this is needed when the star is older and produces heavy atoms that are far more volatile to plasma field heat, but overtime when the star starts producing those heavy atoms and taking those atoms apart units core this produces more heat and the star starts a process of expansion,this happens from the heavy fuel and the amount of dark matter piling up on the core walls is more with heavy atoms making the dark matter containment wall thicker, this chokes the core of fuel atoms and builds more heat that is not radiating out as good the star expands to thin the core walls and feed the plasma engine, but eventually this expansion destroys the star by making the plasma field bigger and hotter and the the dark matter containment core streched out and thin and a breach occurs which lets the plasma field direct access to those volatile heavy atoms and it kites them off to nova the star, it blows off the Nichol and iron layers and lighter layers of atoms Into space and this compresses the dark matter containment core into a super hot radioactive ball of dark matter, the gravity of this mass attracts all the hot particles in its area and they orbit this mass of dark matter making a super hot radioactive charged particle plasma in orbit around this dark mass ball,, ( it becomes an inverted star core fission plasma engine) a d it constructs a super magnetic field orbiting its mass and plasma field of cooler charged particles held their by gravity and the strong attraction force of charged particles they love to join up and field train into magnetic lines if force, this is what exists at the center of the milkey way a dark matter mass, (black holes are imaginary) they are all dark matter masses that's what star cores produce, and 200 billion years from now when are galaxy is far far away by itself that super hot radioactive dark matter mass will cool off the radioactive particles will decay and the heat will evaporate in old space, and then the super magnetic field rotating that dark matter mass will induct that mass into hydrogen gas atoms making a big bang expansion that releases the outer perimiter galactic orbiting stars and planets, and mini dark matter masses into an expanding ring with all those hydrogen atoms and charged particles and dark matter from the galactic core following them to reseed an environment with the parts and processes to construct the new universe from the old

[@jomen112]

Source?

[@RaymondJerome]

what kind of kids go to a lecture like this?

[@TheRoyalInstitution]

Smart ones! We have a really diverse audience of children and adults who come to our talks.