Dark Matter Night with Katie Mack and Ken Clark

[Applause] hello everyone and welcome to Perimeter Institute I'm Lauren Hayward and I'm a Quantum physicist and teaching faculty member here at Perimeter and I'm the co-host of our podcast conversations at the perimeter and I'm just thrilled to be co-hosting tonight as well it's dark matter night and yeah [Applause] it's not just happening here it's actually in a kind of superposition happening in two places at once and that's because tonight's event is simultaneously taking place at the Arthur B McDonald Canadian astroparticle physics Research Institute in Kingston Ontario and my co-host Mark Richardson is there with a live studio audience Mark how are you and how is the audience doing over there thanks Lauren I think we're doing great it's pretty warm in the room but uh we're having a good night so we're really thrilled to be entangled with you in Sharing tonight's event I'm I'm Mark Richardson everybody I'm the education and Outreach officer at the McDonald Institute we're a collection of scientists universities and research Labs across Canada uncovering some of the biggest mysteries of the universe by looking at some of its smallest things and we are definitely thrilled to be both a virtual and a real pair of venues for tonight's exciting lineup and what a lineup it is uh we are very lucky to have talks from both Katie Mack at Perimeter and Ken Clark here at the McDonald's Institute and we have a special guest uh appearance from the snow lab group they put together some extra content for uh Ken to include in his uh in his presentation and so later in the evening we're also going to have a few more opportunities there's going to be a tour of the observatory people want to head over there it'll be raining but anyway I think there's still lots to see and uh so yeah lots of opportunities after tonight to check out other other activities in these in these spaces and so tonight I'd like to highlight that for me and Queen's University our home is the lands of the Cataract we now Kingston it's the traditional land of the anishinabe and the hot nishani peoples and many indigenous peoples before them I truly I'm truly appreciative that we're all able to learn tonight both from here and from our respective lands for those joining online and those the perimeter and I'm certainly appreciative of the fact that I have the opportunity to hang out with you tonight Lauren thanks Mark for us perimeter is just two decades old but people on this land have been asking big questions about our universe for thousands of years looking at the night sky and understanding our place in the cosmos is a human constant throughout the ages we are thankful to those who preceded us and for those still present today and those who will follow we will strive to act responsibly and collaboratively to carry forward the Quest for knowledge for the betterment of all yeah and to all of you I urge you to think of the connection that you have with the land around you and the gift that we have to learn wherever we are including from the dark skies and longer nights above us made even darker as yesterday was the new moon um and while I encourage you after tonight uh maybe to even Explore the website who's dot land and learn about the past people who have lived where you live and now Lorena back to you thanks Mark before I introduce our first Speaker let me say to those of you watching online around the world please join us on social media on Twitter you can tag at Perimeter or at McDonald inst that's at McDonald inst because scientists from both institutes are online and if you have a question for either speaker you can ask online and those questions will be relayed to me and Mark for the post-talk Q a sessions and now it's my pleasure to introduce to you Dr Katie Mack Katie is a theoretical astrophysicist who holds the Hawking chair in cosmology and science communication here at Perimeter she's the author of the book The End Of Everything astrophysically speaking and has written for a number of popular Publications on Twitter you may already know her as at Astro Katie where her smart and witty commentary on science has attracted hundreds of thousands of followers and tonight she's your first tour guide of the invisible Universe please join me in welcoming Dr Katie Mack thank you thank you so much thank you so much for coming out on this uh dark and spooky evening um we're going to be talking about dark matter and dark matter is very close to my heart because it's one of the main things that I work on as a researcher and I'll also talk about how it connects to our understanding of particle physics and the universe so just to get us oriented here oh hold on we live in the Milky Way galaxy this is a beautiful view you can get in the of the Milky Way in certain places because we are inside the Galaxy we can't see the whole thing if we could it would look something like this this is our nearest neighbor large Galaxy the Andromeda Galaxy so we live in this spiral galaxy with stars and gas and dust and black holes and all of that and when we look out into the cosmos we see galaxies everywhere we see an amazing assortment of galaxies throughout the Universe but when we look at those galaxies when we look at all that structure in the universe that's really just window dressing the majority of the universe is entirely invisible so I'm going to be talking about one aspect of that dark matter and I like to use analogies and metaphors when I talk about dark matter and compare it to things that people have a personal connection to so in this case I will talk about the comparison between dark matter and the force so if you're familiar with Star Wars then you know what uh the the force is what gives the Jedi his power it's an energy field created by all living things it surrounds us and penetrates us it binds the Galaxy together so we can go through each of these characteristics of the force and compare it to what we know about dark matter okay let's start at the beginning what gives a Jedi his power well as far as we know there's no connection between Jedi and dark matter also of course we know that not all Jedi are male so that clearly doesn't work what about the next bit an energy field so dark matter is a kind of matter which means it's something that has mass it has gravity there is a connection between matter and energy from as we know from Einstein so it does have energy so you can think about it in those terms but really it's a kind of matter it's something that has mass like like the other particles that we deal with day to day next part created by all living things no as far as we know there's no connection between dark matter and life um whatever Philip Pullman says in the His Dark Materials series however uh you it is true that without Dark Matter it would be very difficult for living things on earth at least to exist because of its role in how galaxies formed in the very early universe so that's one of the things that I'm studying is the connection between dark matter and galaxies in the early universe but really dark matter is something that helped galaxies deform in the first place in the universe and I'll get it I'll get into that a little bit more later surrounds us yes so dark matter is something that seems to be around us all the time it's something that galaxies are kind of embedded in so you can imagine galaxies sort of inside these giant clouds or or Blobs of dark matter where the Galaxy is just a small piece and the Dark Matter uh cloud or or blob or we call them Dark Matter Halos are kind of uh engulfing the galaxies penetrates us yes so it turns out that dark matter is uh it's invisible as far as we know it's invisible because it doesn't interact with light which means it doesn't interact with the electromagnetic force so something that doesn't interact with light is invisible because light passes through it it doesn't reflect or absorb light it doesn't emit light but if something's invisible it's also Untouchable because when you touch something what's really happening there is the electrons in your hand are pushing against the electrons in that object and that's the force that you're feeling so if you don't have electromagnetism if that if those electrons don't feel anything then you your your hand would pass right through objects and we think that dark matter is something that doesn't experience electromagnetism and so it's something that can pass through other matter so as far as we know there is dark matter passing through this room right now passes through the Earth it's going through us all binds the Galaxy together yes this is one of the ways that we first understood how dark matter works is it's something that that seems to be providing the extra gravity that keeps galaxies from spinning apart and I'll talk about that more in a minute dark matter is something that brings other matter together and holds it together so when you think when you see a Galaxy like this in the sky you should imagine that it's really just a small part embedded in this sort of blob this Halo of dark matter okay so I've just told you it's invisible I've just told you we can't touch it so how do we know it's there how do we see it so the main way that we learn about dark matter is about its existence in the universe is by using the fact that it affects how things that do emit light move around so in this video you might not be able to see very well the person standing in the center waving her arms around and moving the that fire around in circles but you could see that the fire is moving around in circles and that's not something fire usually does and you can see how quickly that fire is moving which tells you something about how strong those arms must be how fast that person must be moving those arms and so you can tell that there's something causing that movement to occur you can see the bright thing moving around and that's one of the ways that we first learned about what about the existence of dark matter so this person here Vera Rubin um there are posters of her I think out in the atrium she was one of one of the people who was studying how spiral galaxies rotate in the 1970s and she was one of the people who gave us some of the the most convincing evidence of dark matter she wasn't the first the only person working on the stuff she wasn't the first person to hypothesize it but she did have play a large role in getting astronomers to understand that dark matter is a real thing that's out there so she was looking at galaxies like this one spiral galaxies and she was looking at how they rotate so a spiral galaxies do rotate not really like this but the stars on the outside the stars in the galaxy rotate around the central region and by looking at how those stars are rotating around the central regions of the Galaxy you can learn something about the gravity that's holding them in what is it what it is that they're orbiting around so for example if you have something like a solar system or asteroid belt you have most of the matter concentrated at the center and the the objects orbiting around go more slowly in the center don't go sorry go more quickly in center and more slowly toward the outside because toward the center they feel the gravity more strongly they're closer in so they can go really quickly without flying away and on the outside they go more slowly um but when when Vera Rubin and others looked at the way that stars moved around in galaxies they saw something more like this where in this uh animation the stars of the center and the stars of the outside are actually moving the same speed the ones on the outside take longer to get around because the farther to go but everything's moving at the same speed which doesn't make sense if all the matter is concentrated in the center or even if you know most of the matter is concentrated right there then you can we can plot this out this was one of the plots from her paper so this is the rotational velocity as a function of the distance from the center of the Galaxy and what they found was that as far out as you could see stars the stars were going about the same speed whereas if if the meta really were concentrated where the light is concentrated in the center then it should be dropping down something like this um and so it's kind of uh kind of analogous to like if you see a merry-go-round and there's a big kid pushing this merry-go around there's this little kid kind of holding on to the edge and that Merry-Go-Round goes really really fast then that kid his arms are not strong enough to hold him in he would just fly off into the dirt right but if it's going really fast and he's still sitting there like he must have a little seat belt or something holding him into that merry-go-round and so dark matter seems to be that invisible force holding the Stars within galaxies as they're moving around really really quickly and our understanding is that it's more concentrated in the center and it gets less concentrated on the outside it's kind of this this spherical distribution ish of matter but you might ask if there's other evidence because there are other ways to explain the orbits of stars around galaxies and there is other evidence there's a lot of other evidence in our other areas of astrophysics and cosmology I don't have time to go into all of them I will tell you something about gravitational lensing though so there's a demo of this out in the atrium earlier this is a sort of cartoon illustration of Einstein's theory of relative general relativity the idea his theory of gravity so the idea there is that massive objects kind of make dense in in space they kind of Bend space around them now this is a 2d representation really we live in three spatial Dimensions so you have to imagine instead of you know making it a dent like that what's really happening is that massive objects are kind of pulling space into the toward them in all directions it's harder to illustrate on that graph but um the idea is that that massive objects curve space and then other objects if they're moving around nearby respond to the curvature of the space they move through the space along its its curvature so if you have a massive object and another object moving past then the path of that object will be curved because the space is curving due to the presence of that Mass and if you instead of having a massive object moving past if you just sort of shine light past something massive then the light also follows the curve of space and so you end up with light curving around in that curved space as well and the the cool thing about gravitational lensing is it doesn't care what the matter is made of if there's matter that's that's bending space then space is bent and everything responds to that even if that matter is invisible even if it doesn't interact with light so there's a cool um animation of this uh made by a a science fiction author I like a lot Greg Egan he writes these extremely nerdy books about science fiction but anyway um he also does a whole lot of sort of physics illustrations and stuff in his free time and he made this illustration of what it looks like if a big invisible object moves past a field of stars so imagine you know an invisible object is kind of moving between you and some background stars or galaxies or whatever um now you won't be able to see the object but you'll know it's there okay so when I start the animation you can see that the background is being warped by the presence of this mass and as this Mass moves along it's distorting the images of those background objects because the space is it's bending the space so much that the light from those background objects is being warped you're getting multiple images of some of these background objects you're getting these Rings If the alignment is just right and that's called gravitational lensing and we actually see that in the sky all the time there's some amazing images of this so for example this is one from jwst that just came out a few weeks ago so this is a cluster of galaxies here and it's bending the space and you can see these arcs of where the background galaxies are distorted by the bending of that space and if you actually counted up how much mass was in all the stuff that's shining it's not enough to create that much bending right so when you look at an image of gravitational lensing it's measuring all of the mass and most of that mass is invisible mass and we have tons of images of these where you have galaxies or clusters of galaxies and they have these really amazing distortions of these background galaxies in multiple images of background galaxies and if the alignment is really good you get these giant arcs and if it's really perfect you can get a whole circle it was called an Einstein ring sometimes you get a happy face and in all of these cases but just by looking at the the placement and distribution of those arcs and those those distortions you can you're really weighing the total amount of matter there and you find that most of it is stuff you cannot see okay so then what is it um we don't know the usual starting point is something called weekly interacting massive particles okay um the what the what we're saying here so weekly means it interacts with other matter either weekly or not at all so weekly being either sort of feebly or um or just via the weak nuclear force there are a couple different ways to interpret that um but we haven't seen any interactions with other matter I'll talk more about that in a bit um massive in the sense just that it has mass not that it's really heavy and particle in the sense that it acts like a collection of particles it acts like a collection of particles that just don't have electromagnetism so we usually abbreviate this to wimp uh the name came about back in the day when the other major alternative was massive compact Halo objects machos so okay so what is what is a wimp well we know we have a bunch of particles in the standard model of particle physics so this is the standard model of particle physics we actually found a new one recently the Higgs boson there so these are the particles these are all the particles we've ever detected in a particle detector in an experiment of any kind okay so the blue here these are the quarks uh they come in six different flavors up down charm strange top bottom they're named in the 60s and 70s um the quarks are the things that make up the protons and the neutrons the particles that sit in the centers of atoms so protons are made of two up quarks and a down Quark neutrons two down quarks and up Quark then the green these are the leptons there's the neutrinos which are these ghostly particles that come from the Sun and other stars then there's the electron and its heavier cousins the muon and the toe the electron is the thing that goes around the atom um you know usually it's depicted as a kind of orbit but when you get into more physics you find that it's not really orbiting it's kind of a cloud of electronness around the center of the atom and then in the red here these are the gauge bosons which are the force carriers the they're the particles that mediate the forces of nature so there's the photon that does the electromagnetism so photons are responsible not just for light but for for electromagnetic electromagnetic interactions there's the glue on that's the thing that kind of holds everything together inside the nucleus it's the mediator of the strong nuclear force and then the W and the Z bosons have to do with the uh the weak nuclear force so they're they're um they have to do with things like radioactive decay weakling nuclear interaction okay so which of these could be the dark matter so we could look at what the properties we need to have for Dark Matter are so we need it to be massive it has to have some Mass so that rules out the massless particles in this model it needs to be long-lived in the sense that it can't be decaying into other particles it needs to be you know something that that holds its own so that gets rid of the ones that have short decayed lifetimes it has to have no electric charge because we already said it does interact with with light and it doesn't interact with electromagnetism so that rules out the electron and the remaining two quarks and the final thing is it has to be slow moving in the sense that if it's just zipping through the universe all the time really fast it doesn't collect into those Halos it doesn't bring matter together so we'd have to it's called cold dark matter is the usual Paradigm it's it has to be slow moving it has to be kind of sluggish and that rules out all of the neutrinos that we know about so we're left with a bit of a quandary which is that we have the standard model particle physics it's everything we've ever seen test should interacted with detected and it's none of those and that means that whatever it is it has to be something that's in addition to the standard model it may be one thing it might be several things but it's something beyond the standard model particle physics which is part of why it's exciting because if we figure out what it is then we've automatically improved our understanding of particle physics okay so how do we find it now there are a number of different things that we can look for and I'll kind of talk through a few of those uh briefly and then um and then Ken Clark will go through in more detail the detection that he and his colleagues are working on so the problem is that you know I said it's sort of Untouchable that means that when dark matter and regular matter kind of go past each other they tend not to interact but there's a chance that every once in a while there will be some interaction between dark matter and regular matter maybe they have some interaction via the weak nuclear force maybe it's really really rare so much that it doesn't show up in our sort of astrophysical observations in which case there's got to be some kind of interaction that could happen between these particles right and so we usually draw interactions kind of like this so if you want to look for a dark matter through direct detection you kind of read the diagram this way and wait for a dark matter particle to bump into a regular matter particle and the regular matter particle comes out so what we'd actually see since we can't see the dark matter is we'd see a regular matter particle bounce off something invisible or be bumped by something invisible that's kind of what they're looking for with direct detection um then you can think of maybe reading this diagram a different way right so if there's some interaction that connects these things maybe it can it connects them in a different way maybe you can have a situation where two dark matter particles come together annihilate with each other and regular matter comes out the other side and this is something that some theories of dark matter have in them that dark matter can annihilate with other dark matter and create regular matter and that gives us the option of direct indirect detection which is where we look into the sky and we look for the sudden appearance of high energy particles from places where we don't expect them to come because what we because when this interaction happens when the Dark Matter turns into regular matter what we would see is just regular matter appearing high energy particles or sometimes gamma ray is because of the uh the conversion of high energy particles into gamma rays but if that can happen then if it can happen this way then you can expect that it should also be able to happen the other way so regular matter particles should be able to come together and create dark matter and that's the idea behind the production method where we're looking for the production of dark matter in particle colliders and so what we would see there is that we would see that we'd smash our particles together and they would seem to disappear that there'd be missing energy in the Collision so let's kind of sum up where we're at with all those things so direct detection it's inconclusive hopefully Ken Clark will tell you a little bit more about this but there have been a few hints but so far was nothing really convincing indirect detection also inconclusive we've seen a few places where there's extra stuff coming from things in the sky we didn't expect extra stuff coming from but there could just be astrophysics we don't understand and then production there's been no signal we haven't seen anything in those uh in those colliders however the astrophysical evidence for dark matter is really very very strong in a lot of different regimes and so where we sit is this we have we can make a pie chart of what the universe is made of okay and we can do this by studying the amount of dark matter we see out there the evolution of the cosmos A lot of different parts of cosmology and it tells us that about 27 of the universe is dark matter tells us that about 68 of the universe is dark energy which I didn't get into it acts kind of very differently from dark matter but it's most of what the universe is made of and then there's this little five percent slice that I've labeled atoms here and that contains the entire sand model particle physics everything we've ever seen touched interacted with detected in an experiment and that means we have this fantastic Opportunity by studying dark matter to massively increase our understanding of the universe and also massively increase our understanding of particle physics so amount of time I will leave it there and I'll take some questions and then we'll move over to Ken's talk thank you thank you so much Katie for that fascinating talk as you said we're gonna have a q a session now and so for those here in person at Perimeter you can find your way to the microphone in the aisle if you'd like to ask a question for those at McDonald Institute you can raise your hand and someone will bring a microphone to you and we're going to start with a question that was sent in online so I really like this one because I think it might have a tie-in with your book Katie the end of everything so the question is what do you think might happen to all the dark matter at the end of the universe oh that's an interesting question what will happen to dark matter at the end of the universe so um I actually worked for a little while with a student thinking about this this question about how would dark matter how dark matter would it sort of evolve into the Far Far Future and what we would see and my under understanding I mean we don't know what dark matter is so we can't be sure about this but if dark matter is something that annihilates then over time that dark matter in Halos would would annihilate and turn into regular particles turn into radiation through a Cascade and eventually sort of spread its energy out through the universe just so that as everything else will so as the universe evolves you know the the Galaxy the Stars will burn out the galaxies will sort of fade black holes will evaporate and dark matter over time the the amount of dark matter will decrease if it is something that annihilates because then it'll turn slowly into a sea of high energy particles and radiation so that's that's our best guess at the moment for what dark matter will do amazing thanks let me just encourage our live audience again if you'd like to ask a question please make your way to the microphone Mark do we have any questions from your audience over there without seeing you okay maybe I'll go to oh we have someone approaching our microphone here in person so please go ahead introduce yourself and ask your question um I'm Justin um earlier you mentioned that there are certain fundamental particles that are short-lived um and decompose what I'm wondering is what do they decompose two into is it just energy or um how are they short-lived in that way yeah that's a great question so it depends on the particle so uh in general what they'll do is they'll they'll Decay into a lighter particle but they have some interaction with um there there are other kinds of interactions that can happen they can Decay into different kinds of channels so for example when the Higgs boson was detected at the Large Hadron Collider it wasn't the Higgs boson that they saw it was the Decay products of the Higgs boson that they saw and they saw different kinds of Decay products so they saw you know gamma rays they saw um uh some uh quirks and and things like that um in the same case the quirks the quarks themselves were also not really stable they saw other things that came out of that so so it depends on the particle and sort of what its interactions are with with the other particles um Supreme what you're saying is that it will keep on decaying until it reaches a more stable State um yeah so it'll Decay until it gets to something that doesn't Decay so um so generally so we don't think that protons Decay at any very long uh for a very long time at least um and so a lot of part so like um if you leave a neutron alone long enough it'll Decay into a proton um but uh there there's um yeah so so it'll it'll just kind of it'll Decay into to whatever the sort of most stable part of of that part of the standard model is thank you sure hi my name's Brenna um I have three questions number one you were talking about the lifespan of a dark matter approximately how long is it uh so so the lifespan of dark matter so it depends on the kind so it depends on the kind of dark matter um so because we don't know what it is we don't know how long uh it'll last um if it's a kind of if it's if it's a kind of dark matter that annihilates with with itself because so some kinds of particles theoretically can be their own anti-particle which is kind of weird but that's apparently something that dark matter might be able to do if that's the case then when the two dark matter particles come together they would annihilate but otherwise they're stable so when I mentioned that the Dark Matter would you know annihilate eventually in the distant you know distant future of the universe and and Decay away then what's happening there is it's because there's concentrations of dark matter where you can have that Annihilation happening um there are other models of dark matter where it does legitimately Decay into something else so some models of dark matter have it decaying into like X-rays and um through some process and so it varies by what the dark matter is my second question is um if there are different types of dark matter I know you were talking about there being kind of roughly two but would that have anything to do with how they bounce off of each other as well um so we don't know if dark matter is one kind of thing or a whole bunch of different kinds of things um in in the diagrams I was kind of trying to depict a kind of dark matter where it's it's its own antiparticle so it sort of can annihilate with itself but there are other ideas where you have a whole range of different kinds of dark matter that are kind of at different densities throughout the Universe there are some kinds of Dark Matter theories where you have two different types of dark matter that interact with each other in certain ways so it really varies and we don't know if it's more unreasonable to hypothesize a single kind of particle that we can't see or a whole Zoom of particles that we can't see like these those are depending on who you ask those are sort of equally extravagant hypotheses and my uh my last question is if the universe can grow uh will the amount of Dark Matter also slowly get larger um so the as far as we know um the the universe the growth of the University expansion of the universe is really just the sort of empty space getting bigger and all of the stuff in the universe um it's the same amount of stuff so it's just distributed over a much larger space in that scenario so probably not the the probably the the dark matter is just diffusing just like everything else okay thanks great and next okay do you have a question on Iran as well yes we have a question from the McDonald Institute so Mark over to you uh is there a relationship between black holes and dark matter that's a great question too um so there are somewhere it's made of tiny black holes um the uh the idea is that it's there's some scenarios in which tiny black holes are formed in the very early Universe these are called primordial black holes and um and if they're not so tiny that they would evaporate completely by now then they might be around and if they're around then depending on their Mass they might act a lot like the kind of dark matter we usually think of just particles that don't interact that much with other things if they're too big then they can mess up galaxies they're too small they evaporate there's but there's a middle ground where they don't do a whole lot dynamically they don't mess up galaxies too much and they also don't evaporate and they don't pull in a lot of matter because they're just little and in that scenario in that sort of little Mass range kind of somewhere around an earth Mass where the the size of the black hole would be like this big um they uh we wouldn't be able to necessarily tell them apart from other kinds of other ideas about Dark Matter so it's it's possible it's not the favorite idea for what dark matter is made of but but we don't know for sure okay thanks Katie I think we're going to take one more question so let's take one more from our live studio audience here uh hi I'm Madeline hi um is there any particular quantum mechanical aspects of Dark Matter that's special for example symmetries any hidden symmetries or something like that um yeah it's a great question um it's another one I have to answer with because we don't know what it's made of we don't we don't really know what the particle properties are but there are some really interesting possibilities for dark matter where the quantum mechanical uh behavior of dark matter is really important so for example some of my colleagues here work on an idea called fuzzy dark matter or ultra light dark matter which is a kind of dark matter particle that's so small so light it's like the mass is so so small that the wavelength of it so every every particle has kind of a wavelength depending on its mass where it can't be really localized in one spot um and if it's if it's a small enough mass then the wavelength is so long that it can't fit into a Galaxy and so there's a kind of um there's a kind of this these ultra light Dark Matter models the quantum mechanical aspect of that particle is is really important how it interacts really important to how it deals with galaxies and so it can create things like interference fringes within galaxies where you get sort of um variations in the mass little little speckles in the galaxy in the in the Galaxy because of the interference of the dark matter with itself which is very cool thank you so much thank you okay thank you so much for all of those great questions I want to thank our audience here at Perimeter in Waterloo our audience in Kingston and our online audience for some really great questions thank you Katie for your amazing talk and for all of those insights that you've shared let's all thank Katie again thank you and now let's hand things over to our colleagues at the McDonald Institute over to you mark thanks Lauren it is my honor now to introduce the next tour guide for our dark evening on heavy matters uh Professor Ken Clark is an associate professor at the McDonald Institute located here at Queen's University and a research scientist at Triumph Ken works with the Pacific Ocean neutrino experiment off the coast of British Columbia the Pico collaboration mostly at snow lab in Sudbury and he is the Canadian spokesperson for the scintillating bubble chamber and tonight he's going to tell us a little bit more about how we might go about looking for this elusive dark matter gotta say I'm in a pretty good position here having had such a such a great intro to how this is a the whole situation it's going to make it uh much easier to give this talk okay so the talk that I've been uh you know that I'm giving is how we're looking uh by that I mean I just replied but I mean dark matter how we're looking for it not like we're looking good to Dark Matter that's not what I meant by that title but uh so how we're actually searching for it and what we're going to do and the reason for that being I am an experimentalist I have spent quite a bit of time looking for Dark Matter maybe more than I want to admit uh and we just had this really great introduction by uh uh by Professor Mack at uh at Perimeter about what it is or what it what we think it might be and why we think it exists and so it was a lot of you know there are we don't know a whole lot about it so we need to find more and it's obviously challenging we heard a lot about how challenging it's going to be uh but instead of just kind of giving up and and crying we're going to try to start by making things looking for different ways in way that we can detect it so we don't know very much about dark matter we don't really know how we don't know what it is as we heard we don't know how it's going to interact so we're going to search widely we're going to open our field and use a number of different methods to try and find out what it is so in doing that uh the kind of the um a colloquial way of thinking of it there's basically three kind of categories we're going to use so those are we can make it so that's one of the things that we can do uh we could break it uh and obviously you know this is going to be another one that rhymes we can shake it uh also side note this is the high quality of Animation that's going to occur throughout my slides so uh buckle up I'll expect Pixar to be calling but these are the three three kind of General methods that we're going to use we can make we can break and we can shake and I'm going to go through those one by one uh and try and give an example and talk about how we're going to use it to find each one of them so the first one is made this is kind of the one that everybody thinks of when they think particle physicists what we're going to do is going to take something that we know uh particles that we know electrons protons neutrons maybe some light atoms things like that we're going to get them going real real fast and we're going to smash them together and we're just going to see what comes out of that there is some you know this is more than just and a fun idea there is some logic behind this what we can do is we're providing kind of all the building blocks in terms of the energy that we need and so if we provide all of this energy in a limited space then essentially anything that can be produced eventually be produced uh in terms of you know if we keep running this long enough we should have all the possibilities for things that could come out and that includes dark matter so what we can do from my uh high quality slides here we take these particles we know we smash them together and we control Where They smash together where they smashed together we have a detector that is incredibly sensitive and Incredibly complicated and is there to kind of find out what is coming out of that that Collision so I just want to take a brief second to talk about this plot so essentially with this plot what you're doing is this is uh one of the events from the atlas detector at CERN so what you're seeing is you're essentially looking down the Collision point so the two particles that we just saw expertly animated going around are coming into the screen and out of the screen and they've met at the screen and what we're doing is we're seeing the spray of particles that's all coming out so you can see there's different layers of detectors and they detect different qualities about the particles but we're using those to detect all the particles so this is the kind of thing that we're doing so it has advantages and disadvantages one of the disadvantages obviously it's kind of difficult to produce the energies that we need if you have a few billion dollars lying around you can start building one of these accelerators and trying to figure out uh if you can do it on your own and the other disadvantage is that the analysis is really challenging I'm going to get into a little bit of that in in the next slide but there is pressure accident for doing things this way I mean this is how you know the Higgs was recently found we just kept smashing things together and looking at what came out and then eventually you can identify that there's something that there excuse me so I wanted to talk just a little bit about what we're doing because all of you just heard this great talk about how rare it is that these particles interact and you're thinking to yourself okay fine Professor clerk I kind of believe you you can snack things together and make them but how could you possibly detect them that is the trick to the whole thing so you can't detect them all you can do is realize that something is missing from your collision and that's what's shown in this here you can see that on the on the picture going off to the right there's a couple of events there's things going on it's hard to read these plots but they gave the nice cones showing what's happening so there's something happening that's going on there but there's nothing coming off to the left and if this was truly a system that had no left or right balance coming in it has to come out there are all sorts of conservation laws that say this has to be balanced so there has to be something coming out along this dotted line and so that's the way that they actually look for these events is to say we can put together piece together everything that happened from the shrapnel there should have been something over here and that's missing and is there some way that we can you know get a bunch of events that are missing and collect them and then identify that there's Dark Matter so that's the kind of make it strategy that's there the break strategy we just heard actually in the really good previous talk about self-annihilating Dark Matter so there is some chance that we kind of do the opposite of the of the make strategy we take particles we don't know they collide together we don't cause they collide together and they turn into something that we do know so in my great animation here we have our two dark matter particles come together they annihilate they go away and they turn into something that we understand so this is pretty convenient in that now we have something that we can actually detect potentially uh that's come out of this and that we can do that but to need to do that of course we need a detector so I am showing here uh one example of a detector that could be used to do to something like this a biased example as all of my examples are in the stock uh by a project that I actually worked on I'm showing the The Ice Cube detector so in the little model of planet Earth here in the South Pole we have a detector that looks for neutrinos so if there is some chance that all of these dark matter particles they come together and they annihilate and then they produce neutrinos we can then detect those and we can use those to go backwards and figure out if there was dark matter there so this is good in that we don't we no longer need the billions of dollars to make all these accelerators that's taken care of for us but identifying these things is not simple because there's coming in from everywhere all the time and so what we really want to do is be able to have uh have some way of saying that that yeah that looks like dark matter and that was touched on as well what we'll do is we'll look for places where we think there would be a collection of dark matter so since we know Dark Matter interacts gravitationally all the big heavy stuff we saw in the in the previous talk the really nice uh illustration of the curvature of uh space-time and then you know there's a heavy thing in the middle the dark matter can actually get trapped down there so you can think of all the kind of heavy stuff that's around uh you can have this kind of puddle of dark matter in the middle of it and that gives a really nice place for dark matter to annihilate and then turn into something that we can see and the Sun is pretty heavy so we could use the sun we can see if we saw a whole lot of events coming directly from the Sun that we didn't understand then we would be able to say hey maybe there's something going on maybe dark matter is annihilating but do you need to be able to point back to do that so I just wanted to give a brief illustration because Ice Cube has some great illustrations this is a cartoon of the Ice Cube detector just showing that at the in the ice at the South Pole there's all these light sensors installed that you can actually see uh the light I see from the interactions so what we expect to see is a particle coming in a neutrino it hits something and turns into a different particle that we know but that particle is going faster than the speed of light in ice so it's producing light along its path and we use that light to be able to trace backwards to where it came from so you can see in this event particularly uh you trace back along that line and say yeah we know exactly where that neutrino was coming from and that would give us to say uh you know hey all of these neutrinos are coming from the Sun there's something going on there maybe we should look at it maybe it's dark matter so that covers the make and break strategies so the final one is the shake strategy which is to be quite honest kind of the weakest one in the rhyming triplet here what we're going to do there is we're going to have the Dark Matter particle come in and hit something that we understand usually a nucleus so the Dark Matter part matter particle comes in hits a nucleus that nucleus bounces back just a little bit so this is just balls on a pool table essentially and when that nucleus bounces backwards a bit we're going to be able to use that to find out that dark matter is happening so illustration Time Boom Dark Matter particle goes away nucleus bounce backwards just a tiny bit this gives us the signal that we can look for so that's the the Shake strategy so again the Signal's happening all the time as we heard Dark Matter streaming through us and all of that all the time uh so that's good but interactions are really rare by definition so we can kind of get over that if we put a lot of Targets in its way then we're increasing the odds of this happening obviously well increasing the odds but increasing the odds we actually see one of these events so that's okay but there's very little energy there you can imagine when you're just thinking of energy and thinking of things to detect the movement of a nucleus is not something that's easy to find so I was trying to think desperately of analogies for this um what I kind of came up with was comparing it to earthquakes I mean you know not my best analogy probably not my worst though you can talk to my students so what we're trying to detect in an earthquake you're trying to detect the movement of tectonic plates right these big things sliding against each other for Dark Matter trying to detect this nucleus going backwards and that's it so you know the the most simple the most basic um way to detect them with earthquakes we've all seen this rolling sheet of paper and the pen on it so when the when the the pen shapes you actually get this recorded with dark matter it's a little more complicated you might have to have some you know superconducting things operating down at minus 270 C it's a little bit harder but here's the really big problem the energy so I had to look this up but a magnitude zero earthquake I learned a lot about earthquakes past few days gives off 63 000 joules of energy now magnitude zero is not something you will ever feel it's defined as being an earthquake at which 100 kilometers away a particle moves one micron so it's not very much but it still gives you 63 000 joules when we're looking for this nucleus recoiling that gives you point zero zero zero zero zero zero zero zero zero zero zero zero zero zero zero zero one joules 10 to the minus 16 joules uh to try to detect this is not very much and then of course I had to put in this last uh row just you know earthquakes definitely exist I don't want to give people the impression that I don't think earthquakes exist dark matter you know the jury's out on that one so what is that quantity of energy what does it mean again trying to find some analogies this one I like slightly more uh if you take an average bacterium no such a thing existed but apparently an average bacterium weighs this 10 to the minus 10 grams so convert that to kilograms you get into here if you figure out kinetic energy you know half MV squared all the students here you know following along wonderfully uh so how fast would this thing have to be moving in order to deposit the energy that we're looking for from that dark matter signal turns out you go through the math it works out to .02 meters per second or roughly 0.1 kilometer per hour um that's pretty slow I have a two-year-old who likes to go on walks around neighborhoods I know slow and this is very slow so there is not much energy that's being deposited here what we're going to need is going to need really fancy detection schemes to be able to figure if we can find this amount of energy so I'm going to talk about three examples again completely biased by my experience but the first example is we could use Noble elements now Noble elements have this great property that when there's deposits the energy small deposits of energy there they produce light they scintillate so we can use that we can say that we can't really detect this nucleus moving backwards very well but we can really detect light very well so as long as this is producing light then we can do this we can use that to try to find out what's going on so here's our animation he comes in produces light and that's that's the signal that we're looking for uh the example that I'm going to use here is the the LZ detector or the LZ detector I guess since they're not based in Canada or the UK so this is their their version of that detector inside this nice clean white uh Teflon sheet it's just basically a bucket of xenon Xenon is one of the noble elements it makes a great Target for a lot of reasons now all along the bottom here uh oh I do them that's nice along the bottom here these are what we call what are called photo multiplier tubes so they take in like even just single photons and turn into into an electrical signal that we can detect so you take your bucket of xenon you put all these photomultiplier cubes on the bottom and also on the top for a slightly different reason you do that and then you can detect the light so by doing so we've changed this little nuclear recoil into light we know how to detect light everything's good and then LZ can go on and and do their detections another thing we could do is we could use really really cold detectors and I mean very cold as I said earlier operating at basically almost minus 273 uh Celsius so extremely cold detectors what we're looking for there is that same particle to come in and cut that nucleus to recoil but then two things will happen one is that as the nucleus recoils some of the electrons or some of the electron cloud is going to be left behind so it's going to be separated from the nucleus and we know how to detect electrons or electron clouds we know how to do that very well so we can use that the other thing that we can do is because this is so cold and because you have a really nice lattice of of particles in here that little recoil is going to cause a vibration in the lattice and that vibration to change the temperature of this very slightly so if you have an extremely sensitive device that measures temperature you'll be able to see not only that there's been electrons produced but but also that the temperature went up just a little tiny bit so that's that the signal that we're looking for here so your particle comes in produces electrons you pull those down you make those go to your electron sensor and it causes this vibration which you would detect on the on the detector as well the example here again my experience bias is the cdms the cryogenic Dark Matter search so this is an ex this is a picture of what their detectors it's like hockey puck size maybe two hockey pucks on top of each other of solid germanium so a very clean pure material and that's going to be able to give us this reaction the instrument one side with these electron collectors and the instrument the other side with extremely sensitive temperature detectors and doing that you're able to see the signal that's come from the Dark Matter coming in the last example I'm going to give is you can use superheated liquids so if you have and you manage to have it in a container and take it above its boiling point that means that any small deposit of energy can actually cause that to boil so this is a this is a great way of kind of amplifying what's going on so your dark matter particle comes in causes this little boiling and then the boiling expands as your detector boils we watch the detector we look for these interactions we see what's going on we can also listen to it and so this gives us another way that that little deposit that tiny recoil has been changed into something we know what to do with so example here is the the Pico detector which which I also work on this is a the most recent generation of the Pico detector Pico 40. you keep your superheated liquid in the center part here between two very clean very expensive fused silica jars and those are so smooth and so clean that you're able to raise the temperature of your liquid up above its boiling point and it will just sit there and wait for one of these particles to come in and give you a nice deposit of energy uh not shown here although they will be shown in a little bit later are the cameras that we use to watch it the microphones that we use to listen to it all of the things to do the detection itself this is just the internal guts and I just use it because it's just a really pretty picture we still have kind of a big problem I told you that this situation that we have going on right super simple nucleus goes backwards tough to detect but maybe we know how to do that I might have convinced you but what we really have is something that looks more like this there's stuff going on all the time and you have to sort out what's happening to try to figure out what's going on with this and to do to distinguish all of the other things happening in your detector from the one recoil that you want the one nucleus movement that you want that was caused by dark matter collaborations do this in very different ways they work very hard in order to do this I've shown three examples that correspond to the three examples that I gave earlier uh in the in the top left here is what you get if you have like a noble detector basically what you do is you look for the scintillation that happens when you first have an interaction and then you take those electrons that got forgotten you force them to come up and make them scintillate too and you look at the amount of light produced by each of those reactions and the the different ways of causing an energy posit produce different ratios of that so that gives you a way to distinguish between what you want and what you don't want which is a lot of stuff for cryogenic detectors you already have two seeing things you have the electrons you have the heat balance those two and say that the way that we want if we have a real nucleus moving backwards it looks different in those two ratios and then if you have a superheated droplet detector like the Pico detector or secreted liquid detector like fecal detector is back to about 15 years ago there and mistakenly um you can actually listen to it and it turns out the different ways of generating this sound actually cause they are generating this nucleus movement sound different and so you can actually you can separate out that way and this this is the part that really kind of blows my mind yes it's hard to detect things yes you know looking for a nucleus moving just as seems like it should be science fiction and not possible but being able to separate out why that's happening is pretty incredible to me so collaborations spend a lot of time trying to do this so we would say if only somewhere that we could go that we could put our experiments that we wouldn't have to deal with some of those backgrounds so clearly I'm leading into the next part of the the talk here which is snow lab so snow lab is a facility that is deep underground science facility uh it's somewhere that I'm familiar with having worked there for a long time and actually having you know been worked at the snow lab facility for a year and a half in my career so where is it it's just a short four hour beautiful drive north of Toronto uh you go up just just outside of Sudbury there's the snow snow lab is housed you can see that in this uh this expanded picture here this is the actual snow lab building itself where the scientists hang out and do science I guess uh while they're while they're there uh the only thing you can really see of the mind is this green kind of tower here that's the head frame so that's the top of the mine shaft that takes you the two kilometers underground uh that you have to get um I will say this this picture does not show the best side of Sudbury I think it really is beautiful up there um this great kind of Canadian Shield area and lots of lakes and and not just this uh so snow lab is it's a big thing there's a thousand users a bunch of Institutions across many countries which is good and we go underground we do all of this work to get down there for this reason I told you you know we have to distinguish all of these events well if we could not have some of these other events even better so what happens is all the time we're being bombarded by Cosmic radiation there's you know cosmic rays coming in they interact in the atmosphere they produce muons and they produce electrons and neutrinos and they produce a whole bunch of things those are streaming down and streaming through us all the time that's not a big deal for us as people for our experiments it is fatal you could not run any of these experiments on on the surface so by going two kilometers under the Canadian Shield you get this this great Shield uh not to be too repetitive and you lose a factor of 50 million on all these events so you have a dramatic reduction in the background but going underground itself is not super simple uh snow lab provided a video here which is really dark and mostly black of people going underground so this is people on the cage which is what it's called Uh when we all cram together with the miners and go underground you can see everybody in there we can see everybody in their mind gear pack together in this little room going down it takes about five minutes or so if you get a direct shot down to the two kilometer level so here you can see the levels that are going by that happen about every 200 feet or so there's another drift that has been mined out by the mine this is all still an active Mind by the way so there's lots of minors and it's super fun to be able to go there so our team has arrived at the two kilometer level and now they have to walk through the drift which which has been mined out previously so just the tunnel underground and you can see them walking through with their headlamps on and all their safety gear through the actual mine itself they finally get to snow lab which this is just outside of the facility and they come into the facility so that's where this video ends we were walking into the facility itself so that's kind of the the process of getting down and going into snow lab uh and so one of the other things in addition to just the shielding I I went and you know on a little rant about bacterium at some point uh which you probably stayed awake for but this is saying that any little thing that's around any dirt that's around anything like that can really cause serious problems with our detectors so the way the seal lab was constructed the entire facility is a class 2000 clean room you can see it looks really clean but what exactly does class 2000 mean so these are the illustrations that the snow lab uses in the mind when you're walking through the mine underground if you take one cubic foot of air there are about 10 million particles that are above half a micron in size so if you were to count up all the particles bigger than half a micron we'd get to 10 million in a cubic foot I know the mixture of units bothers me too but there's nothing we can do that's just the way these things are judged so that's the if you're just walking through the mine in your home I think this is a little bit High to be quite honest but in your home or in your office it's closer to about a million particles per cubic foot of that size so it's about times better than when you're going walking through the mine once you get into snow lab it is actually 2 000 particles uh bigger than half a micron in a cubic foot of air so all of this work has to go into keeping all of the dirt and dust and everything from the mine outside because it would ruin all of the experiments happening down there so this is the the kind of effort that snow lab goes through so we got to the door in the last video the first thing that you do when you get down there you take off all your gear and you have a shower so it is pretty convenient that you get to go to work and have a shower in the morning particularly because the age is usually at about 6 a.m so not a lot of time for you know a lot of hygiene before that but then you come out of the shower and you get into special clean room gear all of your clothes are down there provided for you and you're into a real clean room gear that you're going to be in for the rest of the day and of course in in the evening it's the opposite well you don't have a shower but you get rid of all your clean room gear it gets washed underground and it's ready for you the next time or the next the next time and you put your mind gear back on and you go back out through the mine so not only do you have to wash yourself all of the things everything that you bring into snow that has to be clean so this is another video just with some bolts that are in What's called the car wash area but in addition to those having to be cleaned when they get in the car wash area also always has to be clean right through those doors at the end is the mine so those 10 million particle cubic foot are fighting to come in through that door and there's a bunch of really good staff at snow lab that are fighting to keep them out and it's just a constant battle between those two but it is another thing that when I used to give tours at snow lab it would really stress because it blows my mind that just picks something pick the the nut at the end of the bolt holding on that roll that had to come underground and then be cleaned and then be installed everything has to come and be cleaned first before it's installed so it's an it's a huge effort that goes into this stuff so I'll just talk for a little bit about the experiments at snow lab this is a shot down the the drift on the tunnel where one of the experiments is um there are dark matter experiments at snow lab obviously uh I've mentioned some of them the these are the Pico experiment here and the future site of the super cdms experiment here you may have seen the news G model outside in the foyer the news G experiment is here so there's a number of dark matter experiments that are going on but it's not all that snow lab does so lab clearly has neutrino experiments uh anybody at Queens I think it's in the in your written code that you have to know about neutrino oscillations and things like that that happened down here with the snow experiment which is now the snow plus experiment there's other neutral experiments there's also technology experiments just people doing things that would be better to be done underground and another one I think is pretty cool is the biology experiments there's a couple of different things that are going on with Biology we can talk about later if you're interested but snow lab is more than just dark matter I guess is what I'm stressing at here so I've got a few more videos that they provided this is a video of the Pico detector these ports that are on the side are actually the cameras that I talked about earlier the neat pretty picture is inside there and this is all contained inside a water tank uh not full obviously we don't fill them while the students are in them usually but the these water tanks are there because although we've gotten rid of all of the backgrounds that came from the sky and all that stuff we still have other backgrounds that come from the walls and all that we have to get rid of those as well so putting your experiment in a water tank does a world of good in terms of trying to get rid of those it's a Pico experiments uh there's another one here this is the cute experiment it's one of the technology experiments where they're testing cryogenic visitors uh it's kind of a nice test facility inside its own water tank and then as we kind of come around the corner from cute this uh platform the future site of the super cdms experiment so this is what exists of it so far and it's just there ready and waiting for super cdms to come in and and be installed on top of it and again you can see all of these all of this stuff that's around and just remember that everything had to come through that car wash and be cleaned by someone as it went in so it's another thing that blows my mind um the final thing there's a place called The Cube Hall which is what we're looking at here it's a very large room several stories tall we're going to kind of look over the edge and see a couple of different again some water tanks this water tank is where the mini clean experiment used to be and is where the next generation of the Pico experiment is going as we pan to the side we'll see the Deep experiment this is just the top of it obviously you can't see the water tank even because it's all covered up and installed and if we could see over the edge and down about another story or so you'd see the news G experiment which is installed just on the on the floor at the bottom there so I think that's it yeah they just asked me to put up their coordinates and then uh yeah that's all I had so thank you very much listening thank you Ken that was a really really fascinating talk and thank you to snow lab for providing a number of materials I just want to grab my access to the online world so I can see any questions coming in that way but I'm wondering I think I will start there but if anybody has a question here and by all means raise your hand and then I'll keep an eye out to see if there's anybody standing at the uh the podium can we maybe stop sharing those so we can see the podium and for our perimeter audience you can make your way to the microphone again if you have questions so let me just see so Ken there's a question for you from YouTube which is how might you discern a dark matter particle from a neutrino interaction for instance or yeah good question so actually that's a very pertinent question one of the big uh issues that experiments are coming on is that as we as experiments get bigger and more sensitive we're actually starting to be able to see some special kind of neutrino interactions so it's true that it makes it very that's one of the difficult things to tell apart in fact if we get down to the area where we're seeing a lot of these neutrino interactions it's going to be problematic for trying to distinguish if there is a dark matter signal on top of it there are things that people have proposed one of the really neat ideas that has fallen maybe a tiny bit out of favor but is that if you could actually instead of just seeing that energy deposit if you could find out where it's going then you could do something like Ice Cube did you could track backwards and see if they're all coming from the same direction if that direction shifts throughout the year as we move around there's a lot of different things you could do if we would be able to have the detection now there are experiments that can do this so far they're very small so maybe the next thing to do is to think about sizing up those experiments or finding a different way for existing experiments to be able to figure out which way that nucleus is actually moving oh yeah yes we have another question in this room go ahead oh I have a question about the interaction of the dark master with the matter indices in this case you're considering that when in a dark matter interactive moment I wouldn't have a kind of a scattering and this is scattering would provide a energy that should be found by this insulator oh this is Catherine utica's like the phone on the special that would give this signal to the scintillator so essentially what happens is that the what we're expecting to see is that the Dark Matter particle comes in in this in this scenario let's say that it happened the Dark Matter particle comes in it deposits that energy and then some really complicated chemistry happens but it's really the movement of the nucleus and the energy deposited from that scattering that causes the scintillation so the Dark Matter particle itself has has nothing to do other than causing that first recoil the first movement of the nucleus I think that was that was a question you're asking yeah and another question because you are considering that the nucleus it moving but in the sense that normally the other nucleus in the material is moving and they have like this kind of uh particle known as phonon that is the collective excitations of the particles inside of material how did that this dark matter could interactive if these funnels in the sense that would be not uh interact with the nucleus but if this movements of the particles so it's true that I have talked strictly about nuclear recoils that's not necessarily the only way that we can detect well we could potentially detect Dark Matter it could be other things recoiling it could be for example electron recoils it could be a lot of things but interacting with the kind of excitation in the atom itself is not generally one of the ways you can create uh kind of virtual phonons through the vibrations that I talked about with the super cdms detectors that kind of thing but that's the kind of the major way that you'll be able to detect them that way I hope that answers your question but if not I'm happy to talk to you again later I want to ask if there's any questions over at Perimeter we do anybody lined up ahead I'm Brenna and I have two questions so the first one was about um your shake method of discovering dark matter um you mentioned that you were going to be using a new a nucleus what were the reasons other than just that you could detect it that you picked it could there be other materials that you could use so we look particularly for nuclear recoil so for the movement of a nucleus for a number of different reasons some of them being that since we don't know exactly how the Dark Matter interacts how it couple how it actually you know how it exchanges the energy the nucleus gives us a really good situation in which there's a number of different ways it could exchange the energy so in this I'm kind of talking my way around the using the spin of the nucleus versus the mass of the nucleus if the Dark Matter kind of interacts with the mass of the nucleus we want something big so a nucleus is is a coherent entity that is fairly big has a lot of mass so that gives us a big Target but a nucleus can also have an effective spin which then if it interacts with spin then we could actually use that instead so there are a number of different ways but as I said to the to this other question uh looking for just the nucleus is not the only way there are other ways it just happens to be in the methods that I talked about the way that we're doing it foreign a little bit later on or my second question is when you were talking about the cold sensor that you were using for detecting uh dark matter how much would it vibrate when Dark Matter passes through it oh yeah great question and it also gives me the chance to kind of wax not so poetic about these detectors the way that these things work is absolutely amazing essentially what you have is you have this you set you have a piece of metal on the top of it which at this temperature is superconducting and any small temperature change we're talking into the kind of you know millikelvin range will actually cause that to transition from superconducting to non-superconducting so in doing so you're able to say that you had this very small temperature change so A Milli Kelvin is a thousandth of a degree celsius that you can detect that kind of level of change for this thing which is another amazing thing about these detectors that I'm really glad you gave me the chance to rant about briefly thank you so much hello um thanks Dr Clark and Dr Mack for the talks my name is also Katie and I have a question in a couple of Parts but the main question is how much dark matter is there one in this room two on this planet and three inner solar system wow okay this is uh this is some pretty good question you're gonna try to make me do some math uh and remember some numbers right in front of you so the number is 0.3 gev per meter cubed meter cubed meter cube I think uh so in this room there is some energy now how many Dark Matter particles are in this room of course depends on what each one of the mass of each one of them so we might know the kind of energy density of the particles in this room and the same thing goes unfortunately for all scales I'm going to pop out of all of them the same way but we know the kind of energy density that's going on there but what we don't know is how many particles that makes up because we need well there are a number of different ways we could do it but we need some other way of being able to figure out just the mass of each particle individually to be able to say how many are here um yeah of course as uh Professor Mack said in in her talk earlier there are ways that we can tell how much dark matter is in galaxies right we can see the you know spinning of these kind of things and and that sort of thing and uh I don't know the number for for hours particularly I I apologize there's a question online I'd like to ask which is underground at snow lab what happens if someone has to like sneeze or cough they have a special coughing area it would be pretty great if there was a special room that you had to go to every time you had to sneeze their cough no uh you know people go down there and you're able to you know work normally breathe normally do all of that kind of thing and you can still sneeze and do all of that stuff essentially the reason that it's able to stay so clean is that there's a lot of air changes we've all perhaps learned a little too much recently about circulation of air in rooms and that kind of thing snow lab is particularly good in that the room in the entire or the air in the entire lab is turned over very frequently and passed through filters so if you come in and you sneeze the product the products of your sneeze will be filtered out of the air quickly and I apologize for having said that I feel the gross about it maybe it is time for one last question over at Perimeter so one of the things you mentioned that we're trying to detect here is um if dark matter is bonking into a nucleus right and making that nucleus move a tiny little bit that's Dark Matter interacting with regular matter which from what I had before I wouldn't have thought that was possible because dark matter doesn't have an electrical charge so how does that work right so that's absolutely true and it was I I think described very well by Professor Mack and her talk so it does not have an electrical charge we know it doesn't interact electromagnetically so in the same way that we think of things bonking into each other like I said something about pool table and balls it doesn't work that way but in the same uh In The Same Spirit there are other ways to exchange energy and so one of these is through the weak interactions so instead of being something that you know exchanges photons that we're essentially doing every time we we knock on things you're going to exchange things like a w particle or a zed or something like that so it's not the same it's not the same way that we that we think of things interacting in kind of the macro world in the you know in the atomic scale world you can have different exchanges that aren't ruled out and in fact that weak interaction is the W in the weekly interacting massive particle that was mentioned earlier so that's the interaction that we're looking for to happen not the kind of usual electromagnetic interaction but a weak interaction that happens there thank you all right I think is there one last question there I think we do have time for just one more if you wanted to ask your question um so my question was has any success came out of any of the experiments so far oh boy the last question is the knife through my heart of my of my entire career spent doing this no that's a really good question uh no there has been no success so far uh there have been maybe a few cases that thought that they some might have seen something but nothing has ever been backed up so we can always look forward to the future when there will be success in these things and we will be talking maybe in the future Dark Matter days we'll be talking about what it is rather than how we're trying to find it but good question even if slightly painful laughs all right I uh I really do want to thank both that I can and I want to thank Katie and I want to thank the snow lab crew just for sharing all of their fascinating work here in the field of dark matter um before we kind of announce a few other opportunities here in house I do want to basically sign off McDonald Institute from the feed and hand it back to our partners at Perimeter thank you thanks Mark foreign I want to thank Mark Ken and everyone who joined us in Kingston of course we're also thankful to Katie here and to our audience in Waterloo and to everyone who has joined us online it's been a pleasure to finally welcome back a live audience to Perimeter after such a long Hiatus and we hope to see all of you again soon

Channel: Perimeter Institute for Theoretical Physics

Views: 26,760

Keywords: physics, perimeter, canada, ontario, science, stem, dark matter, cosmology, astrophysics, mcdonald institute, perimeter institute, public lecture, science lecture, dark energy, SNOLAB, universe, Katie Mack, Ken Clark, Dark Matter Day, theoretical physics, outreach, theory, experiment, webcast

Id: kjdqJIS80mM

Length: 79min 8sec (4748 seconds)

Published: Thu Oct 27 2022