4850 Feet Below: The Hunt for Dark Matter

we do hope to be able to destroy some of the really interesting secrets that the University all has to teach us a lot of the things that we're looking for just very rare and very unlikely to be see it is a treasure hunt we're looking for the treasure we don't know exactly where it is but we're going to keep looking because it's valuable I think we're closing in it's in there somewhere in trying to understand dark matter we literally explain the formation history of our own universe we're on the surface in weight South Dakota at the Sanford underground research facility this site was actually the deepest gold mine in the US and operated deep underground laboratory that supports a LOX experiment it's operating right now as we speak collecting data Lux is an extremely sensitive instrument it's a device that's designed to look for dark matter interactions with ordinary matter and it's located mile underground to get away from cosmic rays these are some of the most sensitive detectors that have never been built you might have one or two events per year that mile of rock provides additional shielding to help shield these experiments from the cosmic radiation primarily coming from the Sun and so that lowers that noise by about a factor of 10 million the first time I came here it was very much a WoW moment for me I never thought I would end up in a mineshaft a mile under the earth we were 48 50 feet below the surface so almost a mile we make that journey because on the surface more than one cosmic ray is going through my hand every second here on the 4850 level less than one cosmic ray is going through my hand every three months so Lux it's been designed to be the quietest place in the world and through such an instrument we hope to be able to study dark matter but the reality is we're in competition with other scientific groups who are every bit as capable as we are as long as we attempt to carry out the best matter experiment of course that puts us in a very strong position to be the first set of scientists that you look at it and say yes that's it we know that dark matter is out there we know that it's here with us right now you know it's like the wind you don't see the wind directly because air is basically transparent and the dark matter is basically transparent but you can see its effect billions of dark matter particles are traveling through you every second we can't see them that's why I call it dark matter but nonetheless they're over 90% of the matter in our galaxy we don't know it's basic nature we don't know much of anything other than its gravitational effects which we can see in telescopes you can look at how stars are moving around the galaxy and you plot out what the velocities of those stars should be what you see is the velocities go up and they stay constant that can only happen if there's a lot more gravitational stuff holding it all together allowing you to have these high velocities you didn't have that dark matter holding things together the stars would go flying out to a larger radius you can also look at how light is bent around galaxy clusters see how objects in the background are deformed by the gravity in between and you can use that to map out a lot of some extra stuff that's invisible that we can't see but it's gravitationally profound from what we understand about the Big Bang the dark matter would be produced in just about the right amount that we would need to map these Astrophysical observations dark matter particles don't like to interact they go through the earth pretty much like it's transparent go through you annihilate or transparent wimp is a weakly interacting massive particle we have very good reason to believe that dark matter is wimps or a large fraction of the dark matter is wimps the weakly interacting massive particle is simple humble wimps still right now remains probably our best guess given what we know to date about particle physics it's a little embarrassing that here we are 21st century and we still don't know what most of the universes made off you know there's a pretty small slice of reality that we can actually see or touch in physics you can go well beyond these things we can't feel or touch radio waves or infrared or ultraviolet or x-rays gamma rays neutrons but those things are all around us all the time and with the right instruments you can detect them so this is Lux right here this is the the water tank Lux is deep inside of this guy over here the water axes are neutron and gamma ray shield from all the radiation in the lab space deluxe detector in it sort of based basic form is is simply a bucket of xenon liquid xenon or xenon the noble element is very pure it has very few radioactive isotopes in it which means in its natural form it's incredibly quiet we're able then to use the feature of xenon which is that when particles interact in it it will generate a small amount of light in order to detect dark matter events we need to study or watch the xenon incredibly closely we've designed a system of photomultiplier tubes that are watching the xenon from below and above in our experiment we have 122 photomultiplier tubes they're single photon sensitive devices the average 60 watt light bulb produces 1 billion billion photons per second and we see one photon we expect that dark matter particle is going to fly into our detector it will almost billiard ball style interact directly with a xenon nucleus associated with that there is the mission of light and we can pick up the individual photons that are being emitted from the xenon when that happens you have our s1 signal electrons themselves sometimes actually get removed from the atom when that happens you now have free electrons individual electrons coming out of the xenon liquid generate these incredible bursts of light and light up like Christmas trees so we get a second scintillation signal we call it s2 so we see like little blips that lasts about 30 nanoseconds when we see light hit in a certain pattern then we can use that information to then reconstruct where it happened having such a detailed understanding of the detector is absolutely vital to be confident that what you have is a dark matter signal are not simply some other form of radioactivity to be able to finally directly detect the particle or the particles that make up this matter that we know very little about except that exists would be extraordinary Wow dark matter particles that will be fantastic right to feel that you were one of the people that got this first view of the dominant matter in the universe would be an extremely strong euphoric experience but every time you see something that you think might be a signal you're probably wrong I joined the Dark Matter field really right at its inception as far as direct detection was concerned that was about 27 years ago people were telling me it would take us five years the time I joined and within those five years we were likely to already be detecting signal and the rest as they say was going to be jammed you know nature doesn't have to play by our rules it doesn't want to necessarily deliver scientific challenge that is literally solved in a year or even five some challenges may take an entire scientific lifetime to solve the thing about science is that it's true whether or not you believe it and we have to pare it out that true you're not really having fun unless you're out to discover something new that's at least that's true for me and the fun is in the chase I think I'd be fine if we discovered it there's a lot of fun in the chase Lux runs day and night and the project is absolutely worth the effort our first Lux run underground was for about 90 days when we looked in that data we found complete absence of any Dark Matter signal but that was still extremely exciting there are many theories through what the dark matter could be we eliminated a number of those possibilities and so we've made great progress we're looking for very very occasional events like a single snowflake in a blizzard neutrons gamma rays and beta decays create backgrounds the more there are background events the harder it is to see those individual or dark matter particles we're looking for events per year and to put that in perspective if I just take a typical radiation detector you're going to get thousands of events per second just turning it on this from gamma rays and neutrons all around us all the time and so we knocked that down by trillions factors of trillions Lux is really trying to pass the hundreds we're really trying to be the quietest place to be the experiment that is most sensitive to dark matter it's like the most radio quiet place on earth right now the beauty of Lux if you like it's not only have we created the quietest place on earth but we're able to actually watch it which is obviously the critical aspect that we need for a dark matter expert our next run is for 300 days 300 live days that should bring us around the end of 2016 we prepare to be patient we wait not just days but weeks and months for single interactions that puts us in a very strong position to get direct evidence for this dark matter but clearly you don't know what the future holds after searching for 27 years there have been highs and lows if the model that nature happens to have chosen is not one of the ones we're able to test with Lux then we're going to have to get smarter and figure out other ways to look for it obviously we would all love it if we you know see Dark Matter interactions but even if we don't we're on the trail of one of the most important scientific questions of our age Dark Matter researches have to have a certain amount of a thin what they're doing it's a huge mystery it's one of the most important questions in physics today and it's a solvable mystery anything in physics I think is is solvable so now that I've started this experiment I think I would really love to find Dark Matter I'm pretty invested in it so we'll see Dark Matter is so fundamental to forming the structure in our universe all those things that we find interesting you know the stars the galaxy's if you wonder understand anything about our universe it means you have to try to understand what the nature of dark matter is you

Channel: SciFri

Views: 54,766

Rating: 4.8939929 out of 5

Keywords: science, friday, dark matter, Particle Physics (Field Of Study), xenon, detector, LUX, Luke Groskin, Astrophysics (Field Of Study), south dakota, Sanford Underground Laboratory (Location), gaitskell, daniel mckinsey, science short film, WIMPS, weakly interacting massive particles, particle fever

Id: YxMGWQMoR10

Length: 17min 20sec (1040 seconds)

Published: Mon Oct 05 2015