Dark Matter: A Baseless Hypothesis? | Pavel Kroupa, Francesca Chadha-Day, Bjorn Ekeberg

because it opens the pathway towards a Quantum gravitational understanding of nature which the community has been entirely ignoring [Music] can you tell us more about the modified theory of gravity how is it modified and how does it make the theory different from how we've understood it it was already weird bending space time that's already pretty darn weird from from Einstein what else do you need to

account for dark matter well I am the idea with spending space-time is brilliant and that formulation is disciple thesis so it's one way to hopefully understand what gravitation is but it doesn't mean that that theory is correct there are other ideas what gravitation could be and that is where Linda's concept that it's gravitation is an emergent Force because the information content different regions of space is

different another possibility is that you get gravitation because particles have wave nature and gravitation just comes about because of changes in refractive index which their parties themselves because they are oscillating in a vacuum that Medium coated ether and that changes refractive index and that induces gravitational forces so they are very different in the interpretation of what gravitation could be we don't know what is that um

gravity waves which recently have been detected well the gravitational waves um collapse the possibilities of how we understand gravitation so if any gravitational Theory does not accommodate gravitational waves or it doesn't accumulate accommodate them traveling with a speed of light that theory is ruled out yeah and this for example has narrowed the possibilities in mind so the original version of a relativistic formulation of Mont had

gravitational waves propagating with a different speed and that has been now of course falsified but now there are other theories which accommodate it but that's still interpreting gravitation as a geometrical effect which again itself might not be correct I'm very pragmatical what I rather rather than spending much of my time thinking about what gravitation could be in terms of its deepest origin I want to put

into the computer a law of gravitation with which we can study the law of gravitation by looking at what we observe out there and I know now and that is a uh in physics we call that a five Sigma detection threshold that's how the Higgs boson was finally accepted to be uh to be valid to be there is by reaching the five Sigma detection limit as

the dark matter doesn't exist this falsifies the validity of einsteinian gravitation on the scales of gravity of galaxies and Beyond this means that the whole model of the universe is probably not correct and that's where we are at this very moment to investigate which new theories could one develop just to try to help explain how it is ismon something the first time I came across the

description of it it was something that seemed to have with have to do with very distant phenomena in the universe but in fact I've come to understand that Monde is very much closer to home if it's correct yeah right so say something about it so where does Mont kick in you would say right so in the solar system can you encapsulate what Monday if I understand

it's kind of gravity varies yes okay so tell us a little bit about mom so um um as um Francisco said before Einstein and gravity has been tested and verified extremely well in the strong field regime which means around within the solar system and stronger fields around black holes it seems to be working very well it's an excellent mathematical description and that uh so any other

Theory would have to accommodate that but that is always one of the working principles now now Mont originally uh um as a description of um as an acronym for modified internal Dynamics I prefer to call it milgramian Dynamics in equivalence to Newtonian Dynamics so megromian Dynamics comes about because Milgram noticed where the measurements of the this galaxies came in in the early 1980s when for the

first time the velocity field in galaxies were mapped out to distances of thousands of light years that gravity changes and how does it change well he he noticed that there seems to be an acceleration scale which means that in Einstein's view or description when the when the curvature of space becomes very very small that's the milgram's constant which describes this curvature a critical curvature beyond that

once we go to nearly flat space time the um accelerations of objects appear to be larger in 1999 Milgram wrote a very interesting research paper which was more like a conjecture we suggested that this change comes about because of the quantum vacuum the way we under the sustainable of particle physics is today based on Quantum field Theory and in there the ideas the ideas that particles

are as we've heard before excitations in the fields and there are many fields which are constantly fluctuating of quantum mechanical property of the vacuum and so the vacuum is constantly has an energy density which is fluctuating another problem with that is that the what the energy density what the astronomers need is 120 orders of magnitude below what the quantum field theoretists would like the if I'm

if I'm correct then even empty space is full of energy it's full of energy and particles pop out of it so exactly and then disappear exactly perfectly empty space it's still got stuff and this is what's modifying and gravity in this well exactly so the idea of Milgram was that when you move through this vacuum you have a larger pressure because of the bubbling in front

of you being a little more energetic because of the blue shift and be rather than behind and this exerts a force against you and that's basically why acceleration is not quite as big this Pro this effect is more pronounced in a gradient so when the space time is curved so you over here you've got squash space time over the last squash space and then this effect

is simply what we describe as Newtonian gravitation if you're in the regime where you're basically a symmetry so you have the particle which is accelerating and the vacuum here is as unsquatched as over there then you effectively have a large acceleration because the effect largely disappears yeah that's a point and so this paper is a very remarkable research paper because it opens the pathway towards a

Quantum gravitational understanding of nature which the community has been entirely ignoring because everybody knows there is dark matter for effect essentially the colleagues are completely convinced while believing in dark matter and uh and uh where they ignore the falsifications of Dark Matter entirely because it's become a question of belief in the scientific system so we've got two theories now which will account for the same observations

one postulates stuff we can't see and the other one postulates a shift in the way we understand gravity that goes back to Weinstein and says that gravity will change in different parts of space so what do you think how do you think you could distinguish between these two things it's completely simple uh so you have to be pragmatic you have to do your job as a

scientist properly falsification is the key words you test the one Theory Dark Matter exists tested is falsified with more than five Sigma it doesn't exist you drop it you don't even touch it anymore ever in Armada search group group you do not touch dark matter anymore the and then you look at the other hypothesis it has to be then a modification of gravity or not a

modification it's just a different form of gravity I do not like the to modification because nature does not modify it right it's just a different law and then we work with that loan we try to falsify that equally so far every single prediction made in 1983 you look at the three research purposes Milgram has published he puts on a number of predictions what galaxy should behave

like if that formulation of gravitation is through every one of them has been verified to an incredible amount even galaxies which were not known to exist at that time come in and try to explain why we haven't all stopped working on dark matter so the the main kind of disagreement with the the Dark Matter model that Pablo's describing is that there are galaxies that are are

moving faster than we think that they should be when you have two galaxies that merge in particular if they're all full of dark matter the kind of gravity of this dark matter should slow them down and we see galaxies moving faster than some of our modeling suggests that they should be now within the Dark Matter model and indeed also within modify gravity I would say we

don't actually have a theory that predicts exactly how fast all these galaxies should be moving there's a lot of inputs into that so one of them is indeed slowing down through dark matter but you would also need to really know the the cosmological history of all of these galaxies the effect of all of the very complicated physics of the stars and other kind of regular matter

Within These galaxies should come into play so I think within the Dark Matter model the reason we haven't just all said well okay this is just inconsistent we're going to stop working on it is that it's really quite a complicated question how fast Galaxy should be moving and the Dark Matter model has been so successful at explaining other observations that I really think we should just

be working on both well I might interject here because I hear the statement many times that the Dark Matter models of course the cosmological Dark Matter models have been successful in accounting of a large variety of observations it is wrong I don't know any single observation which has actually been successfully reproduced by by the Dark Matter models one case if you look at the count the

number of galaxies within our surroundings you go out to hundreds of millions of light years you can count the number of galaxies per unit space you have right and we see that the density of meta increases out to um about um 1500 million light years so that's already a large distance um and um which means we live in a gigantic under density this is called the

KBC void which was discovered by Keenan bag and koi in 2012 and has been verified by subsequent studies also looking at the number of Galaxy clusters we live in a region of cosmological space which has a lower mass density a smaller number of Galaxy clusters smaller number of galaxies than further out now that huge and void is completely inconsistent with the Lambda CDM model that lumbarcity

model by the Assumption of how does that mean the Dark Matter yeah I don't think that's synonymous so the uh because it assumes homogeneity and isotropy which is reasonable but it cannot allow such large discrepancies in okay so Pavel you're saying that the current data is inconsistent with Dartmouth I I thought that modern Dark Matter were kind of equivalent in that they're arguing for the same

but you're saying no the data out there is currently inconsistent with with dark matter and is consistently modern absolutely because well the remarkable thing about this is you can you can test whether this under density can account occur in the stock meta model it cannot Beyond it can okay can you uh Enlighten us when we've got two a conflicting accounts of where the dark matter is

still a viable Theory or not it's a note in the context here about whether a theory is successful or not or whether there's evidence of it cosmology uh is in a very unique uh position as a science has also develop its own Criterion for evidence so the goal posts for what counts the scientific evidence has also shifted in the 20th century at the same time there

are arguments of course that if you are looking at very large scales or in micro like in physics at the you know theoretical physics Eugene do need sort of other criteria to access things but this is a very this is a very questionable thing I mean uh Lambda CDM model or the standard model is sometimes called a concordance model because this is the principle that was

invented it's something called concordance is considered evidence in cosmology no other Sciences has this and so what it means to for something to be proven in cosmology is if you can infer consistent patterns across multiple data sets that is inferred as evidence that the theory you used to create it is correct okay and that means you can you can claim uh that you have really solid

evidence for dark matter but yet you have no observational evidence for any single parameter so Francesca have you been Shifting the goal posts I think what Beyond saying is basically correct in terms of what is considered evidence within cosmology is to do with often consistency within the current model but there's a very good reason for that which is that in cosmology are the thing we're studying

is the whole universe so all we can do is look at the sky with telescopes we cannot do experiments because we only have one universe and we didn't get to choose the starting conditions if I'm doing an experiment in biology I can you know try design the exact setup that I want in an Laboratory cosmology and astrophysics are more like archeology all we can do is

look at what's happened so in that way we have had to develop different ways of doing things now I would say that there have been you know some things that are predictions in the more normal sense um so for example if Dark Matter exists and Einstein's theory of general relativity is broadly speaking correct even at large scales then we would expect to observe um the bending

of light around dark matter this is called gravitational lensing and then you know indeed we have observed that so there are some things where you can kind of make predictions and see them but with a lot of science these days and particularly a lot of fundamental physics there's so much input that needs to go into every calculation you have to make so many assumptions and everyone

has to do that we have to do it you have to do it if you're calculating and modify gravity you have to do that to calculate anything that it can be quite hard to disentangle exactly what's the prediction and what's just consistency within the theory I think there's no clear-cut line between those two well in fact that leads us to continue watching this video click the

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