with the Large Hadron Collider running out of places to look for clues to a deeper theory of physics we're gonna need a bigger particle accelerator and we have one the galaxies and the particles the galaxy flings at us may have finally revealed particles beyond the standard model physics is currently in a weird place historically no matter how crazy our theories got there were always new ways to test them your theory predicts a new particle built a particle accelerator big enough to see it but once your collider spans entire countries like the Large Hadron Collider in Switzerland there's only so much larger you can go at least on the surface of the earth the LHC has thoroughly tested the standard model of particle physics the last component of that model the Higgs boson was verified in 2013 but the standard model isn't the end of the story there must be a more fundamental theory that explains the origin of this rich family of particles proposals for such grand unified theories proliferate unconstrained by even the tiniest hint of new physics from the LHC one potentially very important ingredient for grand unification theories is supersymmetry this is one that physics had really hoped to nail down with the Large Hadron Collider Susy is a proposed extension to the standard model designed to fix certain issues with the theory the most serious issue being that the standard model can't explain the minuscule weakness of gravity compared to the other three forces this is the hierarchy problem Susy provides a very natural explanation for the discrepancy by introducing a new symmetry between the fermions which comprise matter and the bosons which communicate the fundamental forces as well as fixing the hierarchy problem this connection between fermions and bosons is in general a step towards unifying the particles of the standard model it's a key feature in some grand unified theories as well as modern string theory leveling it up to super string theory supersymmetry predicts that every single standard model particle has a supersymmetric partner particle of the opposite type the partners of fermions are bosons and the partners of bosons are fermions we'll come back to all this in detail another time but the one property that's relevant for today's episode is that these supersymmetric particles are all expected to be way more massive than their known partners in the standard model to solve the hierarchy problem perfectly those particles would need to have masses at around what we call the electro weak energy that's the energy at which the electromagnetic and weak nuclear forces merge into the same force physicists had hoped that by smashing particles together hard enough in the Large Hadron Collider there'd be enough energy in those collisions to produce a supersymmetric particle and in fact there should have been at least four the versions of Susy that most neatly solve the hierarchy problem but the LHC has seen nothing this doesn't necessarily kill supersymmetry it may just be that these new particles are way more massive than expected if so they can still help with the hierarchy problem they're not as neatly as we had hoped to detect more massive supersymmetric particles you need higher energy particle collisions so what build an accelerator the size of the planet the solar system give up and let theorists just tell their stories actually there is a way to probe energies far higher than it's possible with the Large Hadron Collider the universe itself is a pretty good particle accelerator supernova explosions gamma-ray bursts black hole magnetic fields are all expected to blast high-energy particles like electrons and atomic nuclei into the universe these are cosmic rays the highest energy cosmic rays can have energies around a billion times that of the LHC unfortunately for particle physics experiments cosmic rays at these energies are extremely rare so it's not surprising that we haven't seen supersymmetric particles in our cosmic ray observations yeah or have we let's talk about this thing no it's not a downed imperial probe droid your rebel base is safe this is Anita the Antarctic impulsive transient antenna it's a cosmic ray experiment of a very special sword in fact it's a cosmic ray detector disguised as a neutrino detector disguised as a radio antenna disguised as a hot-air balloon probably I should explain that when ultra high-energy cosmic rays travel through space they bump into the photons of the Cosmic Microwave Background that's the leftover heat glow of the very early universe those cosmic rays lose energy to the CMB which is probably why the most energetic cosmic rays are so rare here on earth but in those interactions cosmic rays can create extremely high-energy neutrinos neutrinos are almost ghost-like particles that travel through the CMB unimpeded so detecting the highest energy neutrinos allows us to learn about the cosmic rays that produce them these neutrinos don't just ignore the CMB they can pass through solid matter lower energy neutrinos can flow right through the earth as though it isn't there we detect neutrinos because very very rarely one will interact with an atomic nucleus and produce a shower of particles for example the IceCube Observatory is a one kilometer cube of the Antarctic glacier laced with photon detectors it spots neutrinos when they decay into electrons muons or tau particles which in turn produce visible light as they streak through the ice this is trink of radiation and ice cubes photo detectors track these flashes Anita works in a similar way but it's focused on catching the very highest energy neutrinos the ones that are produced by cosmic ray interactions with the CMB in order to see those extremely rare neutrinos and eater scans not one cubic kilometer of ice but 15 million square kilometres of Antarctic ice sheet that's where the balloon comes in Anita is a cluster of radio antenna that hovers 37 kilometers above Antarctica if an ultra high-energy neutrino decays in the ice anyway within 700 kilometers of Anita the resulting radio frequency Cherenkov can be seen by Anita's and 10a Anita is designed to detect neutrinos that are coming from below passing through the earth into the ice sheet that allows it to sort out neutrino radio flashes from the flashes produced by other cosmic rays coming in from above in fact and if they expect to see it's most interesting most energetic neutrinos coming in at an angle skimming the arc of the earth on a shallow trajectory they should not come from directly below which we require them to pass through the entire planet that's because the most energetic neutrinos actually do lose energy passing through the earth they aren't expected to make it all the way through without slowing down significantly so you can imagine that Anita scientists were a little confused when they spotted two extremely high-energy radio bursts that could only have been produced by a high-energy particle passing all the way through the middle of the planet that's several thousand kilometers of rock magma and iron ignoring the ridiculous distance they traveled these events look like what you'd expect when a particular flavor of neutrino the Tau neutrino interacts with the ice and transforms into a tower lepton that's the heavier cousin to the electron the Tau is cool because it's so short-lived it produces a Trank of bursts when it's created and then a second burst when it decays into a shower of secondary particles but seeing these very high-energy tau events from directly below doesn't make sense based on our understanding of the normal background rate of high-energy neutrinos is estimated that there's around a 1 in 3 trillion chance that two tau neutrinos could have been seen in the amount of time Anita has been looking physicists are having trouble accounting for these event with any known standard model which brings us back to supersymmetry astrophysicists Derek Fox Stein Sigurd CERN and team point out that there is a version of supersymmetry the predicts exactly the right particle to do this job it's the supersymmetric partner of the tower leptin the tower particle yeah you put an S in front to get the susi particle Selectron squarks Tao supersymmetry is super easy here's the scenario a star particle was produced on the opposite side of the planet by an incoming ultra high-energy neutrino plowing into the earth thus Tao is theoretically capable of is it being straight through the earth before decaying into a regular towel lepton on the other side this then causes a high-energy radio flash coming from directly below that's quite a story but it fits the observations pretty well there are of course other possibilities it could be a so-called sterile neutrino now we talked about that before this particle is also not in the standard model but has nothing to do with the supersymmetry hints of its existence have been found in the Fermilab particle accelerator experiments it may also be that there was some gigantic bursts of regular neutrinos at the time of the observed events hit the earth with enough high-energy neutrinos for example from a supernova explosion and at least some of the ultra high-energy ones could make it through in fact one of the two events may have been associated with a distant supernova that was observed around the same time and location the probability of a chance association with a supernova is around 3% so it's unlikely but it does happen on the other hand the supernova in question wasn't nearly bright enough to make even one earth penetrating ultra high-energy neutrino likely and remember there were two events at different times the other event wasn't associated with any supernova or gamma-ray bursts the final possibility is just that we're missing something perhaps our understanding of neutrino propagation through the earth is flawed or perhaps penguins use cell phones now this is going to require more observation and confirmation the first step would be to look at the other big neutrino observatories IceCube is really the only one that could have potentially spotted similar events actually given the amount of time Ice Cube has been in operation it probably should have Foxen team looked back into the IceCube archive and actually did find some possible high energy towel lepton events that may have come from directly below the data is a little ambiguous they may have been boring on muon neutrinos that can easily pass through the planet but you can bet people will be paying a lot more attention to these sorts of events from now on so have we gone beyond the standard model and proved supersymmetry hell no what we have is a tantalizing hint given the painful absence of new particles from the Large Hadron Collider any hint of something new is bound to get physicists excited and easie will keep flying IceCube will start carefully scrutinizing its data and if these mysterious events from below keep arriving you can be sure that physicists will find an ingenious way to confirm their nature perhaps will verify the existence of the star and with it confirm the supersymmetric nature of space-time before we get to comments I just want to let you know about $0.02 the PBS digital series about personal finance financial experts Philip Olson and Julia Lorentz Olsen guide you through the complex world of personal finance from the kitchen table to the New York Stock Exchange you'll get practical knowledge about how to spend save and earn and insight into how your brain is hardwired to react to economic problems if you have any money and might like to have some more check the link in the description below to subscribe to $0.02 last week we talked about why string theory is so compelling to so many physicists now before I get to specific comments let me address a common objection many of you have some interestingly passionate hate for string theory on the grounds that it so far proved unfalsifiable some of you say that means it's not science now I'm not sure I agree with you string theory may be wrong but it's not testable due to the limits of current facilities does that mean it's not science well the universe has no obligation to operate in a way that is currently testable by any particular size particle accelerator nor does it have any obligation to be simple enough to be deduced by even the smartest primates in one generation or in a hundred the thing that makes string theory less sciency is that it's modern version M theory is not particularly well defined but again that doesn't match Rome Wolfgang Pauli's not even wrong might be a better description string theory is not precise enough yet to be confirmed wrong which means it might be right or not Eddy gale take us why you can't get meaningful energy from the Casimir effect well it's the same reason you can't get continuous energy for a ball falling off a roof you get the kinetic energy once but then you have to expend at least as much energy raising the ball back to the top of the roof same with the Casimir effect the Casimir of plates pull together giving you a very tiny amount of energy but to get more energy you have to pull them apart again which takes just as much energy as you got when they fell together dom c asks a good one to quote i thought one of the fundamental properties of the strings was that the maths only works if they are one-dimensional so how can you get world cheats yes it is a pain keeping the number of dimensions straight in string theory while invariants only works for the 2d world sheet which has one dimension of space and one of time this is the shape traced out by a string moving through time a 2d wall sheet has to be traced by a 1d physical object so yeah the math of string theory only works for 1d objects because these trace 2d world sheets some of you recalled a recent episode in which we talked about a study of gravitational waves that appears to refute the idea of extra dimensions good memory actually this study was specifically evidence against the idea of extra extended dimensions one explanation for the unusual weakness of the gravitational force is that there's an extra spatial dimension that is the same scale as the familiar three so a 4d space in which we live on an embedded 3d manifold called a brane gravity then leaks into the extra fourth dimension causing it to weaken but this has no bearing on the compactified extra dimensions of string theory those dimensions are tiny in extent and they're coiled on themselves so there's nowhere for gravity to escape into it may have implications for the single extra extended spatial dimension of M theory but I need to research that more Olivier Wester Hyde asks if we can make an update video about una mujer given the new findings well yes actually in fact we're just about to shoot it after these comment responses to prove it I won't even change this shirt and to end on a funny - to the max points out that string theory is literally like playing a sad song on the world's smallest violin this is so poetic new if it proves wrong in the end at least we have the perfect instrument for a requiem -