Let's reverse engineer the Universe

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Video in TIB AV-Portal: Let's reverse engineer the Universe

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Let's reverse engineer the Universe
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exploring the dark
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2018
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There is four times more dark matter and over fifteen times more dark energy than regular matter in the universe. And we have absolutely no idea what these invisible dark substances might be. This talk will show how we know that dark energy and dark matter exist, although we cannot see them directly. This kind of reverse enigneering of the universe already revealed some interesting features of the dark parts. However, the true nature of dark matter and dark energy are literally in the dark.
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[Music] the next talk is by Zahra Conrad she's a PhD student from Heidelberg University
and she's giving a foundation talk about how the universe works
[Applause] [Music]
yeah hello everybody I'm really amazed how great the interest in this community is for science this is really really awesome and really happy to be here today to talk to you about how to reverse engineer the universe and by that we will see that we have to explore the very very dark sides of the universe so imagine you are on a rock on a very clear night outside you observe the Stars and maybe you wonder what is out there there are all these tiny little
stars maybe you have images from colorful nebulae in your mind and you wonder what else is out there and how far is all that and where does this all come from so how people imagined the
world to work in former times as depicted here and the caption says a missionary of the Middle Ages tell that he had found a point where the sky and the earth touch so people believe that there is this curtain in the sky and stars are pinned on this curtain and
they were so curious and wanted to know the secrets of how the world works and wanted to look behind the curtain and see the machinery what's going on there of course today we know that the sky is not a curtain with stars pinned on them but we know that we live our son lives
in the Milky Way galaxy and today we know that the Sun is a relatively average star among all the other stars we see and in case you lost track where
you are now so you are here yes so at the beginning of the 20th century people indeed believed that the Milky Way galaxy is made the whole universe oh the whole universe consists of our Milky Way galaxy and everything we observed in the sky is within our own galaxy so you see the world view got a little bit larger so we went from only our own little planet to a whole galaxy this is what we observed but people also wanted to know how space-time works so the stuff our Milky Way galaxy is embedded
in and how could we investigate this question without him about Einstein in
1950 he found the general theory of relativity and this theory made the essentials for our current understanding what space-time is and how it works so we'll introduce to you now the most
complicated equation in this whole talk but this is really the essentials the essentials of general relativity is one simple set of equations on the left-hand side they show the dynamics of space-time so the dynamics of space-time is equal to the energy and the momentum
content of our universe what does this
mean in case our universe was empty the dynamics would vanish nothing would happen space-time would just be as it is but as soon as we fill our universe with stuff with matter with radiation the dynamics of space-time will come into play and space-time will not stay as it is the space will expand or contract will curve and matter will begin to flow and to go into movement this sounded really very strange to people at that time a universe that changes its size
and people don't wanted that this was really something people didn't want so but Einstein introduced the further factor in his equations this lambda sexual to cancel out the effect of the matter and the radiation or universe in order to make it static so nice and smooth as everything should be this equation is for the factor was
allowed by the equations but the nature of this factor was really mysterious is it an unknown energy or a property of space-time we will see this is how our
current understanding of space-time developed but what about our understanding of our surrounding as I told you at that time he would believe that the Milky Way was all our universe consists of we were not able to see much further and what we now today other
galaxies just appeared as spiral nebulae in the sky because individual stars could not be of be resolved now Henrietta Swan Leavitt was a was a woman
who worked at the Harvard Observatory and she investigated stars in the large and a small Magellanic Cloud now we know that these clouds are tiny galaxies that accompany our own Milky Way galaxy and at a time she did she she worked there
she found out that we see already individual stars in these clouds and she observed stars that vary in their brightness on a range of days so they pull say they increase in magnitude and decrease in magnitude and what she also saw was that the faster this pulsation works the brighter these stars are and with this it was possible for the first time to search for the Cepheid variable stars measure their pulsation now since we know the relation with - interpolation of stars and their brightness we observed them in the sky we can infer the distance of these stars and this is what Edwin Hubble did so he
found in the Andromeda nebula and the triangle nebula these Cepheid stars and he used this method of inferring the distance and what he found was that his
nebula must be farther away than all the stars that we can see so for the first time it was clear that there are objects outside our own galaxy that are huge and with that even our own galaxy was not a special place anymore just a place like many others in the universe and our view
from the local neighborhood evolved our Milky Way galaxy here so again you were here in case you lost track and the Andromeda galaxy turned out which we previously believed was only another nebula in our own galaxy maybe tiny is
even larger than our own galaxy but the physicist physicist wouldn't be satisfied with only knowing where stuff is physics is also want to know how the stuff moves why it moves and all the machinery behind that and now in order to determine how the stuff around us really works let's make use of another effect you might know from acoustics the
Doppler effect imagine you standing on the street and a fast car is passing by the sound the car makes while it's approaching you is different than the sound it makes when it's driving away from you it's like the first it's high and then low so what you see is that there is a change in frequency due to the relative movement of the car and this leads to a change in pitch now the same is true for light physical
reasons are but different but the effect is the same imagine there is a star that's approaching you it's light will be shifted to higher frequencies if it's approaching you so that you will observe a change in color so the star would appear more blue on the other way if the
star is moving away from you it will appear more red that's why we call this effect redshift or blueshift now in order to determine the relative velocity of a star with respect to you it's not enough only to measure the frequency of the light because you don't know what the real color of your star is so for this we make use of spectral lines spectral lines are fingerprints of individual chemical elements every element has a very special line feature in absorption line feature in the spectrum and when you observe a certain line configuration you know which element this belongs to and in principle this line feature should always be at the same frequencies but when a star moves towards us or away from us also
these lines are blue and red shifted which means by observing spectral lines from stars that moving close to us or further away from us we know the velocity with which they move okay now we learned how to measure distances and how to measure velocities in the universe and this was done by Fritz Viki
he was a swiss astronomer and investigated the velocities of galaxies in galactic galaxy clusters a galaxy cluster is very huge checked it's a gravitationally bound object of individual galaxies and what he did was okay was interested in oh maybe there like a mobile a they're moving around on staying together and he measured the velocities and what he
found was really really strange these galaxies moved with speeds so high such that it was unbelievable that these guys could stick together because the the gravitational potential could not be so higher from the mass we observed we are we observed the brightness of these objects we knew how many stars should be in there and now they are moving with these speeds so this week he concluded that these galaxies clusters must be much much heavier than we actually observe and then we actually think and he first introduced the term dark matter for that he believed that dark matter might be maybe gas or dust or maybe
rocky material we just can't see because it doesn't glow in later times more
detailed analysis was done by Vera Rubin she used the same principle but she measured velocities of stars within certain galaxies so now we have an galaxies certain stars in there and we move we measure the velocity with which the stars circle around the center of the galaxy and by that she measured this profile which you see here's on the x-axis you see the distance from the center of the galaxy on the y-axis to speed and the white curve is the measured speed of these galaxies and as you see at the center it rises and then it gets relatively flat but again from the mass we can observe in these galaxies we would assume that in order
to hold these galaxies together the velocity should be much much smaller and at that time it was already possible to infer the gas and dust content of these galaxies so it couldn't be dust or
gas that's in these galaxies that leads to this excess and mass so again we observe that there must be more mass than we expected so our the hints for something like dark matter got more and more but let's go back to our view of how the universe itself works now we have this series of what's inside but how does it work itself again we go back to our well-known Edwin Hubble and what he measured was okay he looked at the
galaxies in our surrounding and he wanted to know with which movements are our surrounding galaxies moving with respect to us and what he found was done now called hubble law that the father away a galaxy is the faster it moves away from us so galaxies are fleeing from us and this is a linear relationship but what does this mean
today we know that the universe expands
we call this Hubble expansion and Hubble would be really really unhappy about this expansion naming after him because he never believed that space itself expands but ok famous but wanted or not but what does it mean that the universe expand does it mean that we at the center of the galaxies and everything around us expands no the universe expands at every point so let's assume
we are at point a and we observe a
galaxy at point B moving away from us now when we go to galaxy B what would someone in galaxy B see galaxy B would also see that a is moving away but galaxy B would also observe that anything else is also
moving away so the universe expands on around every point there is no center where the universe expands from it expands from every point and the first one who formalized this observation was
Alexander Friedmann who found the
equations that describe this specific movement of our universe he said the universe must be homogeneous and isotropic meaning that it looks the same everywhere and in all directions regardless in which direction of the universe we look it looks the same why should be different at another point but it changes in time it expands which means that if we take large amount of
space today we go back in time this amount of space will shrink and shrink and shrink and become smaller and smaller and by becoming smaller and smaller it becomes matter inside becomes denser and denser and hotter and hotter and if we go back in time up to some point densities and temperatures are so high such that the universe becomes ionized which means that all the matter the atomic nuclei will not hold the
electrons anymore by by them but electrons and atomic nuclei moving freely around not being bound to each other which is depicted here on the
left-hand side but if we are in such a hot dense plasma what's happening with light light here is are these yellow curves and light scatters on three charges which means that in this hot and dense plasma so imagine you are sitting there apart from the fact that you will be cooked you could not see anything because lights getters everywhere and will not
directly reach its aim but at some point where the universe now expands when we go forward in time the universe cools the nuclei catch the electrons and the universe becomes transparent and at that time a huge amount of photons was released and the cool thing is that we have a picture of this time and this was one of the most famous pictures in cosmology we ever saw and I want to
share it with you that it is
thanks to these two guys we have this
picture Penzias and Wilson they were working on the home the laboratory on a radio antenna I wanted to measure something completely different and had always this noisy background in their antenna and they wanted to get rid of it they thought this might be pigeon poo or something else they clean their antenna and anything they couldn't find out until some day they met physicists and they told them him their problem and is that what you measured is the first light from the universe and for this they got the Nobel Prize afterwards and they got a Nobel Prize and physicists got a new toy to play with because once you have a
new measurement you I mean okay this is homogeneous and nice and you laughed because of reasons so physicists want to know okay is this really so homogeneous as we see it and they did computations and computations I mean today we see structures in the universe so they might have been initially also when this radiation was released so do we see reminiscence of these structures of these initial structures in this radiation field and the computer and computed and thought ok how much matter do we have in the universe and they computed ok I guess we so they guess the the fluctuations in this radiation field must be of the order of hundreds Kelvin which is really really tiny they started measuring and they found nothing what was wrong did they do a mistake in the 90s the Kobus satellite
measured for the first time the fluctuations of this radiation field and it turned out that this the fluctuation amplitude was much much less than expected it was a hundred thousand Kelvin and the only reason that these tiny fluctuations are so so tiny is that a large amount of the matter at that time when the Cosmic Microwave Background is this radiation
was released did not interact with light so here we have to prove that dark matter is indeed invisible we will never be able to see it to take a picture directly from it because there's matter in our universe that does not emit photons that does not interact with photons that is so completely different than what we know the Cosmic Microwave
Background nowadays is much more detailed investigated in these tiny fluctuations we see there he measured by the Planck satellite a few years ago serve as seeds for the big structures we see today and if you're interested in how cosmic structures evolve on these fluctuations I strongly recommend you if you don't haven't if you didn't have
seen the talk on day 2 by Philip Bush simulating universes go there have a look and see how structures are formed from these fluctuations today but what do we know now about our own universe you know we still wanted to reconstruct
our own universe at the very very beginning there was the Big Bang so when we go back in time compress anything at some point we reach really the zero point this was a Big Bang then there was a brief period we believe a very very fast expansion called inflation less than 400 years after the birth of the big of the universe we have this release of cosmic radiation the Cosmic Microwave Background I presented to you then the dark ages came where no stars were at the time then stars galaxies formed and then a new epoch started which was confirmed approximately ten years ago which was the accelerated expansion of the universe he remember this cosmological
constant factor our Anglin introduced in his equations in order to make the universe static nowadays we see that it's not there to make it static but the effect of this constant is indeed to make the universe today accelerating so Einstein invented so to say dark energy without knowing it but today we know ok something in our universe is there to
make the universe further and further expanding regular meta cannot do that regular meta contract space but cannot expand space what do we know about the
ingredients of the universe directly at the release of the cosmic radiation we had very much dark matter atoms neutrinos and photons played a big role but with the expansion of the universe their role became less and less important and today we know that the density of the the energy content of atoms make just 5% of our universe today
70 27% is made up of dark matter and the largest amount of energy in our universe
is dark energy what do we know about
dark energy we know that it is there the universe accelerates the other matter and radiation forms cannot be responsible for that so something like dark energy must be here in order to serve for this accelerated expansion we know that the energy density is really very homogeneous in space so it does not form any structures like matter does it may be constant in time we have no hint today that the energy density of dark energy changes in time so maybe it stays constant forever then we have this cosmological constant but physicists of course don't think okay maybe it's constant so yeah let's assume it's constant but let's check that and this will be checked in upcoming studies up to an accuracy of 10 percent so in the next year's we will see dance dark matter dark energy change its density in time or not and anything else about dark energy is highly speculative there are many different models that predict different things but nothing known today so this is all we know about dark energy for sure let's go back to dark matter maybe we get a bit more to know about
that what could that matter be standard
matter let's briefly recap what standard or normal matter is or the matter we understand you know everybody knows what
an atom is I guess so we have a nucleus that's positively charged you have electrons moving around here's this yet of the quantum physicists not here today so but you see what I mean so in in the core of these atoms they have protons and neutrons and every proton and neutron again it's made of quarks what we know today now what are quarks there
are six kinds of known today the uptick work down quark the charm quark the strange quark the top quark and the bottom quark physicists sometime have humor yes protons and neutrons are made up of up and down quarks the other quarks are much heavier and not very stable but they have been seen in the LHC and other colliders for example then we have the leptons electron muon town and for every electron muon town there is a neutrino this is regular matter or radiation in the neutrino case and this
is not dark matter we know that so we
can rule that out one thing at least we know okay but now we know what it is not what might be maybe primordial black holes so I told you that when the cosmic microwave radiation was released the this matter the dark matter could not interact with the photons a black hole does not emit photons so it traps photons so maybe we had at that time many many black holes there but the problem with this theory is although it could lead to the observations we make today that they are very very few and
very exotic cosmologies only that allow the formation of primordial black holes because black holes must have been formed before atoms formed and Astrophysical observations allow only a very tiny range of masses for these primordial black holes so primordial black holes are not excluded today but not the likeliest ones maybe our
particle model is not complete so maybe they are particles you know it's done that are not in the standard model this is why we call this beyond the standard model particle physics that are these dark matter maybe this is particles just like we know but a bit different how could we detect them so there's a
certain class of dark matter particles or model clouds of dark matter particles called weakly interacting massive particles or wimps here just depicted as dark matter particle and in case they go for the weak interactions they could scatter with atomic nuclei and we could see this scattering in large large detectors and this is what is done today so people are looking for possible dark matter particles that are so different from what we know but maybe they interact via the weak interaction and this is the current stages of different
experiments so the the properties we want to know if our dark matter particle if we detect it is what mass does it have and how likely is it to interact with our other particles with our normal particle so let's assume our galaxy is filled with dark matter particles or wimps we know what the density of this guy must be because we know the mass of our galaxy so the heavier these wimps are the fewer are they so the number density is lower if the mass is high this is one number we want to know we want to know the mass and the size of these guys or the probability to interact and this is what these experiments shown here measures so they want to know okay given certain with mass because we don't know what the mass is there's a plethora of models so there's a huge parameter space to investigate dependent on the wimp mass and assuming a given cross-section what we detect this particle now the continuous lines shown here are running experiments or every line shows given a certain mass if the cross-section or the size of our
particle is above the line we would be able to detect it if the size is below meaning the interaction probability is low we would not see it the dotted lines are experiments that under construction and what you see here relatively bad but see in the what do you see here the orange regions why I distinguish the regions we already have so in the lower regions of very very tiny particles if the WIMP would be very very tiny we couldn't distinguish them from neutrinos so we are blind in this region the red area are already running experienced experiments we know that wimps in this range are basically excluded there were certain signals which are under discussion currently which where it is a bit unclear did these experiments so really something or where these signals from other sources and the dotted lines are experiments under construction or in planning and the line the the blue green yellow line is one of the most forwarded experiment
now which would really go down up to the neutrino background so if this experiments will run one day and if there are whims we could possibly sometime detect this experiment we'll see it but currently everything we saw it looked really really bad okay so this is if wimps interact with our own normal
material but maybe there's not a possibility maybe they don't interact with our normal material but they interact with each other so you have to dark metal particles see here they interact we say that they
might anneal late because they maybe vanish and flow apart to different stuff and there are many models that say okay in case we have this kind of model or that kind of model there must been photons or neutrinos produced by that and this smoking gun radiation this indirect detection of dark matter this could possibly be observed here now the problem with this indirect detection is that the photons are not reno's that are produced there are not necessarily very unique so basically what you have to do
is you have to observe the whole sky for all the radiation you have to measure all the photons all the neutrinos know where they are coming from which means that just if you don't know why this photon comes here what the source of this photon is doesn't mean that that matter is the reason for for this for this radiation so [Applause] so identifying all the sources in the sky and really labeling all the stuff we measure here is is a highly high is of high high effort and I wanted really to mention here the talks from yours Megan das on day one going deep under to watch the stars on neutrinos and multi
messengers astronomy the identification of cosmic radiation and neutrinos which was by Annie on day three so there you see more of how this cosmic radiation can be measured can be identified and what might be how we can go on but currently this is really a really really hard problem okay
unknown particles maybe we are about to see what's going on there but we are already relatively far so maybe let's consider a completely different direction what dark matter might be so maybe it's not a particle maybe we will never see a particle that we assigned to be part of not the standard model and being responsible for this dark matter we observe so maybe our theory of gravity is just wrong maybe on large scales on very large scales scales of a galaxy of a galaxy cluster gravity just works differently than we think so maybe Einstein was wrong now in order to test this hypothesis I will introduce you with the further physical
effect which is gravitational lensing so I told you that matter or energy changes the shape of space-time which means that if you have a huge and massive object it will deform space-time through curved space-time such that if you have here's massive object in a shine light to you from behind the light rays will be curved around this massive object and this is what you see here so you see here a photograph of the galaxy cluster Abell two to one eight and these these arcs you see are not mistakes in the picture or in the lens no these are due
to the bending of light of this galaxy cluster so these arcs you see are galaxies behind the Skellig see clusters in their light is Bend around in space-time until it reaches us now the cool thing is with this method that we can by analyzing the shape of these arcs we can infer the mass of this galaxy cluster so we have another independent method to determine the mass of a galaxy cluster apart from the velocities in its its center so you remember that Zwicky who measured the galaxies velocities he inferred masses and now we use gravitational lensing to infer the mass of a cluster so we have two independent techniques and let's see what comes out of that this was applied to the bullet
cluster so the bullet cluster is a very
very massive cluster and what you see here the lines are lines of constant gravitation so to say and you see that there are two centers of gravity implying that this bullet cluster has two components maybe it was first two clusters and they moved to each other and here we see the centers of gravity now in case gravity works different on large scales we would expect that all the luminous mass so or the mass that we know the atoms the gas would also be there because only the strength changes so we can look at the
gas in these galaxy clusters also by an other independent technique not only by measuring the mass but the gas that fills galaxy clusters and the gas that galaxy clusters fills that the mass of
this is much much higher than the galaxies themselves so this is really the massive part of known matter in galaxy clusters is very very hot and it emits x-ray radiation which means we can observe this gas in x-rays we measure the mass of the galaxy cluster with gravitational lensing we measure the location of the gas in the x-rays and what we see is that the gas is not where
the centres of gravity is here you see the the bright regions are denser and hotter regions of gas or the gas is Delocated from the center of gravity implying that gravity is not just scaled the gravity from the gas is not just scaled on on larger scales but they are really different kinds of mass there one the hot gas which you see more in the center and more outside this must be the mass of our dark matter and the reason why the gas and the dark matter are delocalized in this cases because we have here indeed two
galaxy clusters that move through each other the gas held the pressure from each other heat it up you see these wings going to the middle so it Slough through each other but heated up and was slowed down whereas dark matter which does not interact in that sense just flew through each other without really noticing this observation killed a huge amount of modified gravity models which assumed just the different strength of gravity on larger scales so modification of
gravity they are still modified gravity models
left so different kinds of gravitational theories apart from the general theory of relativity which are possible but let me tell you that one further observation also killed a lot of these models was that the neutron star merger in the past
time maybe you you heard about that that since we have this gravitational wave detector there was a neutron star merger detected and for the first time this was really a huge discovery in multi messenger astronomy because this neutron star merger was observed via gravitational waves in and via photons and via neutrinos so the what we saw was that the speed of the gravitation of the gravity of the gravitational waves that reached us and the speed of the light emitted from this neutron star merger was the same and this was also something that was is is not predicted from from certain modified gravity theories so they are there were many many modified gravity theories who predicted that the speed of light is different from the speed of gravity but now we know the speed of gravity is the same as the speed of light which also improved our knowledge about gravity itself and is a further reason for general relativity so these are the most common models or ideas we have what
dark matter might be there maybe it is something completely different something we cannot imagine off but this is hard to detect something we cannot know
what do I want you to take home we saw how the universe our view of the universe evolved especially in the past century we know that today only 5% of the energy content of our universe is known to us these are the atoms which make up the gases the dust the Stars the earth us this is only 5% 5% of the stuff in our universe is something we can possibly ever see the other stuff we will never see in the visual regime 27% of the energy content of our universe must be something like dark matter in excess in in mass we cannot explain currently with different models maybe it is a particle we don't know and the
largest majority of the energy content in our universe is this strange thing called dark energy that stuff that made our universe our universe expanding in an accelerated way and since we have no other reason to believe differently the future of our universe will be the cold death everything will expand father and father it will become colder and colder because it gets less dense and less dense and maybe this goes up to infinity maybe there's something else coming in we don't see yet but we don't know all we know is that these three components are nowadays the most important components and that 95% of the stuff is literally in the dark but we will know better in the future so stay tuned and explore dark thank you [Applause] [Music]
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[Music] what do you think about the yes string theory has a hard time to make predictions that are actually testable and and I guess this is a very at least for me this is really one of the most important things to follow a theory it is absolutely worth developing these theories because we learn a lot from them but now at least now I don't think that they are of much relevance for us now and the next one the rating expansion of the universe thinking about the big words that we observe in the cosmic structure so what effects are you
this was from the internet oh this was from the internet accurately repeated question please yes sir has there been research about effects of inhomogeneities on the accelerating expansion of the universe so there there is definitely research on how inhomogeneities especially voids affect the expansion of the universe itself and it has been shown that only voids cannot be responsible for the accelerated expansion so only with these inhomogeneities you don't arrive at the cosmology we observe Thank You Internet
microphone number two please the picture of baby universe very cute by the way
it doesn't have an elliptic shape and oh yeah thank you good Christian I forgot to mention that so this is a whole world view to say it's like map of the earth but projected to the sky so when you have a map of the earth it's also an elliptic shape so it's a whole world whole sky view so to say thank you so microphone number one please and speak like me directly to the mic because someone else come here you them how likely or unlikely do you think it
is that there's maybe a fault and the measurements we did which which indicate to us that there must be something like
that matter like that rotation of the galaxies how how how sure it is that all those measurements are correct and there must be something we don't know of all of what is correct the measurements which indicate that must there must be dark matter like the rotation of the galaxies they are there nowadays we live so this is a term that is very often used on cosmology conferences we live in an age of high precision cosmology which means that the values we can measure nowadays are really really very very precise yes Mike number three please you said for the dark energy that there is some new information about the temporal structure that we get and you elaborate a bit wonder what experiments or measurements will give information there yes so you clear analysis T's not a large-scale Sky Survey will give at least to up to some accuracy hints so if there is a strong temporal change in the dark energy content density in our universe we will get a hint for that if it's very weak of course we cannot see that then but in the next years we will get more information on that yes we increment to number four yeah hi you said that the measured energy fluctuation in the microwave background was much much smaller than they expected flirtation can you and the factor was around 1,000 so the time smaller can you give me a reason for this latch factor the reason is that we have only a fifth of the
matter that is that could be responsible for this fluctuations does indeed interact directly with the photons which means that the fluctuations you see in the in this radiation background follows the fluctuations of the metro but only of the matter it interacts with and if it interacts only with a tiny fraction of the measure the amplitude of these fluctuations will be much much smaller than if it would interact with the whole amount of matter number two again thank you for a talk it was very interesting one question the ballot cluster and given that the large dark metal masses apparently didn't interact with each other doesn't that rule out The Smoking Gun measurements for dark matter so the probability that dark matter particles interact as I seem to be very very low so you wouldn't see it if - I mean you would have events while two galaxy clusters move through each other but they are so few that you don't see
that directly in the structure so you really have to measure individual events and the photons and the neutrinos then so it's only very very rare events that would appear that because of course otherwise we would see it if we had strongly interacting dark yourself interacting that matter we would see that in the structures we observe so we
have another microphone number five and back hey thanks for including me indeed questions basically it's a kind of an advertisement for my friend visitors we get a tariff of giant premiered elf photons throughout by gravity have you hear about I guess I didn't understand the theory can you repeat that it is like in the beginning of the universe that were created the kind of photos that I'm asked so the Giants actually were trapped by the gravity I don't guess I heard about that but maybe you come by later and we have a chat about that starts on Quora calm is all he said yeah thank you so number one please you showed us the slide with the the experiments for detecting wimps get how far until you might sorry it's set up for someone taller than me how how long do you think it'll be before the the
wimp detecting experiments actually either detect wimps or prove that we're not going to detect them that way and if we don't detect them with those experiments if we gave you a blank check what is the experiment that you would do to help put this one to rest once and for all okay so the question when we already decided decide this so I showed you experiments that are in planning currently that are many political and technical decisions inside it when they
start to run so I cannot comment on that regarding experiments to decide I mean we tried to of course or what is tried I'm not in this kind of experiments what is tried is of course to extend the range in all directions but if we are not able to detect ever this kind of this kind of particles we really have a problem because then we don't know what to look for if it's a particle because maybe it has some exotic kind of interaction so we have to look deeper and deeper and optimal accuracy so what people do now is to investigate heavenly structure formation because depending on your model of the stuff that forms the structure structures might turn out to be a bit different and to measure these subtleties so we can get from a theory driven approach to see okay what comes out if we assume this is this comparable to what we observe or not number three please yeah thank you I have a question to this dark energy and this accelerated expansion I hope I can pick it into the question we observe galaxies at a very far away so the more father always older they are and it is assumed that in each
galaxy we have a supermassive black hole and black holes we can now say we can say nothing about it so one of the effects is set yeah okay one of the exes let's say eat up even light and maybe this this observation we have that we interpret as dark energy say what's the question I try that is the fact we see is that we interpret as dark energy maybe it's a misinterpretation of what we see and that it's an effect of the masses that that masses have on light and that there is no acceleration and we only interpret this this what we see as a Doppler effect yeah let me interpret it as an acceleration but instead it's an effect of mass on light I am very very sure that this is excluded by the observations we can see because our cosmological model we developed would take this effect into consideration if it was responsible for this observation that lead us to the assumption or to the conclusion that the universe expands accelerated so this can be excluded yes thank you and sorry for me being stupid number four no thank you for your talk
it's always state that is expanding
problem how what I understand is that there's new space created would be that dark energy is the energy which is needed to create space itself this is basically the interpretation so the idea is that dark energy has something we call negative pressure in contrast to regular matter and radiation which has a positive pressure and this negative pressure leads to an expansion of the universe oh yes dark energy is responsible for this accelerated expansion number two [Music] indicates that [Music] [Music] so models are models because they are only subsets of what we describe because otherwise they would be called reality so indeed a model is never complete the question is when is a model contradicting something I mean that's the standard model of particle physics contradict that they are other particles I have good problems to the saying they contradict at least they are not complete we know obviously they are not complete because we observe stuff we cannot explain now the point is that to say okay what is likely or less likely depends absolutely on your point of view because you have to to look okay I have to drop an assumption we made a general assumption for example like homogeneity of the universe when I drop that is that less strong than dropping the assumption that there are no other particles for example and this is hard to quantify which models are more likely or less likely but I wouldn't I wouldn't call it a contradiction nowadays I would call it incomplete I'm sorry
the QED I finish this now please a warm hand and a warm applause for Sarah Connor [Music] [Applause] [Music] [Music]
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