Dark matter. Dark matter. Dark matter. My name is Kristy Hopley and I'm interested
answering the biggest questions that physicists today have about our known
universe the best description we currently have of our universe is a
model called lambda CDM lambda was found in
Einstein's equations and is called the cosmological constant it's currently
theorized to represent an entity we call dark energy CDM is the acronym for cold
dark matter as opposed to its theoretical partner hot dark matter cold
dark matter is thought to make up 99% or more of the entity which we call dark
matter dark matter and dark energy the two components of lambda CDM are thought
to make up over ninety five point five percent of our known universe but we
just don't know anything about them I talked to India for is well for a good
perspective on how to think about these two entities as interacting in our
universe but I don't know how you think about dark matter and dark energy but I
like to think of it as - - like evil not - evil twins by two brothers making a
puzzle and so dark matter is trying to build the puzzle bring all the pieces
together and build the structure of the puzzle
whereas dark Energy's like taking the puzzle pieces that I'm running away and
so dark matter has to run get the puzzle piece and put it back and like as time
goes on in the universe automatic he's running them further and further and
further away and that's exactly what's happening in the universe so Dark Matter
provides the gravity for all our structures to form like the clusters the
filaments if you've ever seen maps of the large-scale structure of our
universe it kind of looks like a huge spider's web in 3d and whereas dark
energies is energy providing this kind of outwards expansion and so it's
slowing down this structure formation so dark matter and dark energy make up a
huge proportion of our known universe but where did these ideas come from so
you think is about 1860 so astronomers are looking at the
motions of the stars and they essentially start to see that the stars
didn't obey the laws of Newton as would be expected given the amount of the
number of stars that we could see we're out there making some assumptions about
typical mass of a star so one of the most interesting only contributions seem
to come from the north Kelvin which is a nice link to Scotland up here
essentially it's just a case of looking at the movements of stars and trying to
understand how that fits in with the user stores as we know and love them and
it doesn't quite work so even back in the late 19th century people were
realizing there must be more stuff out there than we can see and we couldn't
see it so it became known as dark matter I guess the reason why this really
starts to be seen as the father of dark matter is partly because of the
character of zucchini which is an outstanding interesting controversial
figure kind of a personal antihero but also because that was the era where
things started to be quantized quantified much better so that it wasn't
just supposition and sort of all things don't work so well it was really these
are the specific numbers that we need to get to work and this is how much this
dark material there might be and then again whose so he was the observation
that led to the hypothesis of there being matter kind of then fell out of
favor until the 50s and then 16 especially where rotation cuts were
being measured by Rubin and came forward and several others as well and again
that then provided even more robust data that suggested there was this extra
stuff out there so the main hypothesis for us is that dark matter is a new type
of particle and again we might be wrong okay that's good let's call that a
working hypothesis now standard model is extremely successful explain in physics
in of elementary particles okay we know for
example that the building blocks of our universe and everything that we're made
of leptons and quarks so electrons for example the quarks that make up protons
neutrons etc with also discovered neutrinos and we also understand forces
the fundamental forces as the interchange of also fundamental
particles we've got a set and a b-bow some some the recently discovered Higgs
boson now known of the known particles none of the particles that we've been
able to discover to discuss within to describe within the standard model can
be the dark matter we're looking for a particle that is neutral that is stable
and cosmological scales that I have some decades yet and therefore that that
means that we have to invent something and we have to put it into the structure
of the standard model so for more than one reason
Dark Matter theoretically needs to exist but how would we go looking for
something that you can't see from from the experimental site we can also ask
you know how do we even think about measuring dark matter if it's dark so
there are different kinds of tests that have are devised and they can be divided
up into things called direct measurements indirect measurements
astronomical and Collider so the idea is that the Dark Matters hypothesized maybe
as some kind of a particle we don't know what but let's suppose it's some kind of
particles that are floating around in the universe I can talk a little bit
about that after this so suppose these particles are wishing through you know
going past the earth or something like that and so one of the ideas of
experiments is that well let's suppose that we put some some other particles
that we can measure like heavy elements right and into it into a big cavity and
let's just let them sit there and if they start jiggling around then
something clearly had to gone through and we know certain things that can
cause this motion I mean like light and radiation and everything like that
so experiment let's try to control all those kinds of backgrounds in other
words they go deep underground where there's going to be less radiation etc
so they try to control all of these parameters and so then if they start
seeing motion it might suggest that some kind of an unknown particle is actually
struck one of these heavy nuclei and that might give us a hint on sort of
the flux of dark matter that's going through and so that's what I do I work
on experiments with a couple hundred other people from around the world lots
in the UK but many more in the US and then also near Russia Portugal in and
South Korea on experiments like luck Zeppelin which is a large liquid xenon
basics detector it's essentially a large bucket of liquids at home and if these
dark matter particles these particles are going through it and one does bounce
off a xenon atom it will produce a big splash of light and some and some
electrons that will try and detect huge experiments like luck Zeppelin or Al's
I'd have a lot of hope of finding dark matter particles in the future if they
do exist but it's not the only approach to looking for them here we had to blow
be mine to find out about a different way of thinking about the problem I'm
looking at experiment called drift and drift stands for directional recoil
information from France drifts a bit unusual in the search for
dark matter it's not like LZ or some of the biggest scale that much accepted out
there it's it uses completely different technology and it's almost a different
approach if tirely to looking for dark matter
drift unlike the majority of Davos incentives is a directional Thomas
detector so simply put that means that when we seen an event inside of drift
well it won't drift detect something it doesn't just find it as like a point
particle it doesn't give it just immediate information it also plates
at track if you were so instead of being a point event you get a couple of
millimeters track depending on being here the possible
and from this track you can infer the direction from which the particle came I
mean origin of the particle if you will and this is really useful when it says
to put dark matter in particular so due to the way we move through our galaxy
through the universe we don't expect moving with the damage
that surrounds us we think that dark matter is done by ambient air it does
have motion but it doesn't really move with us if it's just ambient and we move
through it so relatively speaking if we're moving through something it's
ambien in our reference frame that ambient thing in this piece dark matter
would be relatively moving towards us like a wind so when we call this
phenomena the WIMP wind we suspect that as we're moving through
the universe we should be experiencing this with wind as we Traverse
and this is where the directionality of drift comes in so drift aims to map out
all the particles that it finds while it's running what you can do with that
information is you can plus it those galactic coordinates of each event onto
the night sky so ridge event that you find and you pinpoint it almost to a
picture of the night sky let's say
don't much of us exist and we find the number of damaged your interactions they
should all be coming from the same direction because they were they're all
part of this width we're all moving through them in the same direction and
if you look at the night sky it should be in the direction of the constellation
of Cygnus so no other possible would give us this behavior neutrinos or new
trailers you know the full plethora of backgrounds available they were all in
them quitters or random nothing would act like I matter it's
totally separate due to its characteristics but we suspect that the
case and so if we did see a hot spot in the
sky due to a number of events all fit in the same location we can almost
completely say they it's confirmed that my three faces so that's why we run
rivers there's indirect measurements we can look for annihilation so the dark
matter is a particle and as with as with particles sometimes they can transmute
into other things like if you have an electron and and a positron and they hit
each other then they will turn into light
okay this it's a matter of antimatter type of thing so in general in particle
physics we can have phenomenon like that and it's the similar story with dark
matter and it's possible that through some interactions the dark matter can
turn into other kinds of particles and theorists have done various calculations
and you know there's predictions that Dark Matter in certain kinds of
astronomical Astrophysical phenomenon would produce abundances or higher
levels of antiprotons or positrons and things like that so these are indirect
measurements that we try to do we put up satellites or we do ground-based
measurements of you know the x-ray spectrum and all these other different
spectra and in the universe and try to see these sorts of excesses and once in
a while there's kinds of blips that oh this looks interesting but usually
everything can be explained by standard astronomy by standard symbology the
third way of looking for dark matter through experiment is astronomical
observations here I go to the Royal Observatory of Edinburgh to speak to
Professor Jose ins about how lensing can be used as a technique to find out more
about dark matter so what we we try and do most of all is look at lensing that's
my particular area is looking at gravitational lensing so if you if you
throw a ball in the air it will come down again and it starts off getting a
straight line but then gravity pulls it and bends it down towards the ground
again so we used that here of gravity curving the paths of objects what may be
less obvious is it also curds the path of light so if you shine a laser beam up
into into the sky it will actually bent very very very slightly downwards
towards the earth that's that's far too small to see with the naked eye you
can't see that by eye and it's too small in effect that you can't see it
absolutely an accepted most extreme circumstances so this was first detected
about a hundred years ago and by Arthur Eddington who was this fantastic early
twentieth century astronomer very very interesing mounted lots of really cool
experiments and he went to the island of tomé and príncipe riches of West Africa
during a solar eclipse and the reason he wanted to do this was that the only
thing powerful enough to bend like that we could see it was the Sun that's
anything with enough gravity to actually do this in general votes of bad idea to
point your telescope at the Sun because he will you will melt your eyes so you
have to go there the only time you can do that which is during a solar eclipse
so he found a cellar accepting he looked at stars around the Sun and he saw that
their apparent position was bent and moved by the Sun's gravity chewing
during that period and that was one of the experiments that led to us believing
Einstein's theory of general relativity that's our current and and best theory
of gravity so our whole understanding of gravity is built on this this disagree
this observation which is which is very powerful one so the theory and ideas
behind lensing are actually quite old however they may be in a lot of use
today I spoke to dr. Alexandra Aman and her upcoming projects using a technique
called weak gravitational lensing so I studied at Mozza using a tool called
weak gravitational lensing so as part of a team we observe distant galaxies using
our telescope in Chile and between us and those distant galaxies is the cosmic
web of the universe so the universe has a web-like structure made of dark matter
and the dark matter is is in clumps in the universe the dark matter is massive
so it has gravity and that gravity warps the fabric of the universe which we call
a spacetime so the the space-time gets curved now because of that when we
observe distant galaxies the lights no longer travels in a straight line it
also gets curved due to the presence of the dark matter and the gravity of the
dark matter so that means that when we take pictures of galaxies galaxies that
are far away their light because of the bending of their light path the galaxies
images appear distorted so the galaxies are a little bit more elliptical than
they really are now you can by measuring this distortion
by measuring this in effect we can understand where about
the stuff that the by measuring this distortion effects we can understand
about the stuff that the light passed through so we can understand the
properties of that matter direct observation there's only one way of
looking for a dark matter through the skies another way is to use simulations
to try and replicate what we currently see and then obviously if the
simulations replicate earth and universes like ours then potentially the
emphasis of that simulation in terms of dark matter are potentially correct this
simulation simulates what the universe would have looked like in a very very
early snapshot of time where you can see matter being drawn together into
structures it's important to know however the involvement of dark energy
is not represented in the simulation as the viewpoint sort of zooms out in all
directions at the exact same rate as dark energy would spread the particles
apart as gravity gets to work you'll see not only small tight spherical blobs of
matter congeal but they themselves form line structures so you'll see large
filaments of dark matter and you can see such filaments in that in the
distribution of galaxies today so just visually but also in terms of the
quantitative statistics that you can measure if these simulations really make
a very good match to the universe as we observe it so on the really large scales
hundreds of millions of light years across there's very little doubt that we
know truly how much matter there is and that the structures within it which are
mimicked today by the structures and distribution of galaxies are a result of
gravitational instability so what a lot of people in the field are trying to do
is to go beyond that and say well how can we use this information to tease out
what the physical nature of the dark matter may be
and for that you've got to go to smaller scales because as I said if you go to
the larger scales in the universe even ordinary matter what gas will fall
together in much the same way as the dark matter in fact in the other that
matter and the gas don't really separate until you get down to the sort of scales
of individual galaxies like the Milky Way so the hope is that by trying to
simulate not so much the large-scale structure of the universe but perhaps
the formation of a single galaxy like the Milky Way or even most interestingly
for some applications the smaller dwarf galaxies it's a Milky Way has satellites
the moment that you know the percent of its mass Clarence and so these little
dwarf galaxies and they're the smallest things we know from the universe and
those smallest units could reveal a lot about the nature of dark matter and
finally and maybe the best test of all the acid test I would say would be
Collider which is to actually produce a dark matter particle in Collider
experiments finding a concrete dark matter particle or producing one at a
collider would be a pretty compelling piece of evidence for the lambda-cdm
case so I spoke to Professor crystals theodopolis who works at CERN and in
project like a CLIs about how you might go about creating a dark matter particle
inside a Collider you would be looking for a collision where you have two very
energetic protons that collide and then nothing comes out
or maybe something comes out one direction but there's some imbalance
because you've created something that's invisible in the same way that you would
see in a galaxy dark a dark area and you you see that you think that this is
something that does not give you nice so it becomes invisible so you're looking
for collisions where there is a strongly balanced you have some particles go in
one direction but nothing on the other the detector hood looks very impressive
as an experimental sequencer and you say that okay I need to collect loads of
those to understand if this is something that maybe bass may be explained by the
atomic model or I find some very large number of those asymmetric collisions
that would point to to dark matter for example one of the things that we're
trying to do right now is you have the the experiment you have two proton beams
that collide against each other at a very very high rate so you have 1
billion collisions per second and you don't have the means you don't have the
resources to store every single one of those collisions you have a system which
is called the trigger which is a combination of hardware and software
some advanced algorithms that in real time trying to make an educated guess on
whether a particular collision looks interesting enough and has to be stored
for offline analysis or it looks very normal very boring and should be thrown
away so the output of this process is what we store and it's a very small
fraction so out of a billion collisions per second we restored only a thousand
so it's a highly selective process okay we store what we think is the most
interesting potentially interesting collision events that can contain
evidence for new physics or contain Higgs bosons that we want to study in
more detail you know that at this point it is fair to remind yourself that we
have been looking for years on years for these type events at CERN and we still
haven't find anything on the trigger is ignoring billions and billions of
collisions so what are the odds that your trigger is simply systematically
ignoring something that you would like to record so one of the there's an
ongoing effort and this is something actually we work you know
other people are working on this is to try to deploy a more sophisticated suite
of algorithms including machine learning into the trigger so even if you cannot
afford to increase the output rate of the trigger maybe if you have some
machine learning it will be able to look into the events that you throw out and
look for some anomalies maybe hey you think this is boring but I say something
that does not really make sense why don't we save this or let's try to
collect several of those to see if we find a pattern that your baseline
selection was going to throw away so we have these four different experimental
methods of looking for dark matter where do we go next I speak to phenomenologist
about the process of moving from experimentation to results and theory
the way we understand phenomenology in particle physics is the bridge between
theory and experiment so again is this dialogue of theorists having ideas that
have to be tested finding ways in which your new theories can give observable
phenomena and also reacting to experimental results at the moment the
experiment that I work in super CDMS and another experiments which are based on
liquid xenon I would say that we are the best at not finding dark matter
this is actually very useful information as well because it tells us faces or
theorists that many of the models that we were working with are either not
correct or they have to be revised so we have a results or lack thereof and where
do we go from there we go to the observatory where I speak to astronomer
about what their results and their data have told them about the searcher
dramatic tell so true that what we have seen is that the more data we have
collected in the last 10 20 years what happened there is that we have been
pushing all these potometer particle models to hire higher energies and that
always means that we are in our models too were pushing
antimatter models to routines where the matter behaves closer and closer to a
person fluid sir so that's what's being going on you know the more we work on it
closer the matter behaves well and that's what general relativity assumes
there is no quantum physics in general relativity so everything we've been
finding so far is that generativity this behaves extremely well I mean that
that's a theory it's extremely I don't know what a quantum physics I'm not an
expert in the field I don't know whether they can't say something like that
so after astronomy I look in the opposite direction to particle physics
where there are four possible candidates for what dark matter could be so so let
me just discuss briefly some of the kinds of dark matter particles that
theorists have cooked up so the one dark matter particle that's actually known to
exist is the neutrino okay so the neutrino is a very light particle it
interacts with almost nothing through measurements of beta decay and neutrino
oscillations we can put a bound that the mass of a neutrino is incredibly tiny
smaller than an electron volt so an electron itself electron volt is review
unit of energy or mass so like an electron is 500,000 electron volts so
that gives you an idea of how like the neutrino is the same time a neutrino
interacts with almost nothing so it's an ideal Dark Matter candidate you think
but if you actually understand the the history of the the time history of the
University of the neutrino in the universe and it used to interact to a
degree in the early universe and it was light and therefore it actually was a
form of hot dark matter and I've already mentioned that in simulations etc we see
that hot dark matter really doesn't explain the kinds of astronomical data
that we see so we can put a bound that you know neutrinos can be a part of the
mix but it would be less than 1% of the dark matter that we actually need so so
that's one candidate that we know of but it really doesn't work too well so so
then there's a whole slew of other possible candidates and I should say
from the onset that none of them have been observed but there's a lot of
theory that's been developed for all of so so one of the promising candidates is
the acción that's a another kind of particle so so there are there are
problems in the standard model with the the strong sector of the the for the
strong force that's the force that binds protons and neutrons together okay so
there are certain cemeteries that the acción helps through a stroke called
charge and parody and so that's the theoretical motivation for the acción
but it also turns out that if you follow this route of trying to to you know
ensure some cemeteries in the strong sector it turns out that the particle
that you actually create turns out to be very light and it turns out to be very
weak weakly interacting now although then accion is light it's so weakly
interacting that it never actually interacts with anything even in the
early universe and that's why it actually is not relativistic so it's a
it's a form of cold dark matter so as I mentioned cold dark matter is exactly
the kind of dark matter that we want so in that respect the acción is a very
promising candidate but only in that respect because as I said many attempts
to observe it and there's been nothing so another candidate it's called a
neutrally no so I mentioned that we're trying to build theories beyond the
standard model and so one of the most elegant ideas is an idea called
supersymmetry so supersymmetry in simple terms is an attempt to unify the forces
and the particles okay and and the consequences of trying to build a
supersymmetric theory is that you actually in a sense double the number of
particles in the in in the universe at least that's your prediction and and the
lightest of these particles of the new supersymmetric particles that you create
the theory tells you that this particle will be absolutely stable and now that's
a very important requirement for a Dark Matter candidate because dark matter has
to exist on cosmological scales timescales so the thing called a
lightest supersymmetric particle the neutralino is a very interesting
theoretical candidate for dark matter the other interesting thing is that a
lot about supersymmetry are things that are real predictions that you can test
in colliders and there were a lot of predictions made about supersymmetry for
the LHC and so far nothing has been found
and the neutralino was certainly one of the candidates that was hoped could be
seen in it the LHC or maybe it'll be a in a future Collider at a higher energy
scale so the thing about the neutralino is that it's it's it's fairly heavy it's
about you know there's there's a mass range you know on it I mean we don't
know the exact value but it has to be certainly heavier quite a bit heavier
than a proton maybe a hundred times heavier maybe a thousand times heavier
so it's quite a heavy particle but at the same time it's very weakly
interacting and it's actually part of a class of particles well we weakly
interacting massive particles or wimps as we like to call them so wimps have
other nice qualities if you actually look so if you look at the thermodynamic
history of the universe okay so the so what we understand is the universe is
expanding so that means if you go back in time it would be contracting so all
that matter would get into a higher higher concentrations and therefore the
temperature the universe would rise and if you go back to the very early phases
of the universe the temperature of the universe would be something like the
billion billion billion kelvins are higher okay really high and what happens
is that all of the other men prepar so what happens is that for example Noella
a hydrogen atom right it's it's a bound state of an electron and a proton and
there's a certain binding energy okay but when the temperature gets high
enough what happens is that there's enough energy that the electron can
simply keep getting knocked out okay of its bound state and it can just be free
and so what happens as temperature gets higher for example is that the first
thing that happens is that these these atoms they completely get stripped away
and they become a plasma so the protons run free the electrons run free and then
eventually the energy gets even higher and the proton itself gets ripped apart
and all the Corpse start running free and as you get to higher and higher
energies basically all you have is a is a soup just a plasma of all the
elementary particles okay so whatever is in your your fundamental theory would
just be floating around there and these wimps okay we understand some things
about the way particles that in the early universe they would have
interacted and then and they would have interacted a lot with with the other
particles but when the temperature of the universe became below the mass of
this particle then it would become heavy right because when the temperature
higher that means that basically there's enough energy that the particle to move
around but once the temperature becomes below its mass it becomes heavy and then
it stops interacting and it's kind of abundance then freezes at that point so
we can use the theory such as a super symmetric theory and we can use our
understanding of cosmology and we can actually make estimates of ham what
abundance of wimps we should expect to find today and the interesting thing is
that we do find from this kind of theoretical estimate about a 10%
abundance that would should come about from a wiff candidate and remember that
I said that dark matter is about 20% of the the content so with in order of
magnitude I mean a factor 2 is fantastic for pathologist so within orders of
magnitude we've seen like an intriguing candidate so you know if you put the
theoretical picture together you have cosmology on one side saying oh I can
predict at ten percent twenty percent abundance your particle physics saying
well here's a really elegant extension of the standard model and this dark
matter Kennedy just sits right there available in some sense for free if you
want to accept supersymmetry so you can see the motivation from a theorist point
of view and I emphasize from a theorist point of view that that this would be a
very intriguing candidate so you know a lot of interest has gone into trying to
detect and understand neutrally knows but again nothing's been detected
another super symmetric candidate is the gravity no so the gravity know is the
supersymmetric partner to the graviton the graviton would be the particle
associated with gravity so that is an interesting candidate but the problem is
it's very weakly interacting it's very light there's very few other signatures
we couldn't possibly hope to find it in a Collider but as far as theoretically
you know this could be another candidate for slightly broader perspective on the
theory I speak to one of enemas most famous theorists Professor Peter Hayes
where he thinks the future theory is headed
I mean if somebody with interest in the basic quantum field theory for particle
physics I'm really
an enthusiastic law so far unverified theories like supersymmetry where there
are candidates for dark matter already embedded in the theory but unfortunately
as far as the big machine at CERN is concerned no experimental evidence yet
for it so I mean as a theoretician I don't really see how we we can end up
with a theory which unifies gravity with all the other forces without having
supersymmetry it's the mathematical framework which makes it possible in a
way which was not previously possible so where else do we go if supersymmetry is
not right I don't know if particles such as the ones finding supersymmetry
theories are in fact wrong all hope is not lost for the search of diamond to
some physicists have come up with a very different way of thinking about the
problem and here I have to the observatory did you write it but yeah
there's a whole whole range of theories one theory is maybe maybe we've got the
whole theory of gravity wrong in the first place our our inference that there
is dumb energy out there comes from looking at gravitational system so
looking at the universe and then saying hey we know the lots of cavity so here's
what's happening perhaps we just have those laws of gravity wrong and maybe
it's that we've misinterpreted what we're seeing because we're expecting
them to behave under the gravity that we used to see that could be wrong and
there's lots of theories about how that could be wrong and so if we've
investigated a lot of these things so we've said well what if what if gravity
behaves differently in dense environments compared to empty
environments that might explain something that would be why we can be
here on the earth and all the experiments we do are very consistent
with our theories of gravity because we're in a dense environment with lots
of matter around but maybe out in the empty void regions of space well there's
no matter maybe the laws really change in those situations maybe suddenly it
just switches to a different kind of mode in those environments and that
that's a strong possibility to that we're investigating right now and
perhaps perhaps these these laws changing
from contexts and it's hard to write on a theory that sort of makes sense of
what we do now because we have very very strong measurements of now between a few
specific cases so we know very well on like on the earth and the solar system
how well copper tea works we know exactly how it behaves because we have
incredibly precise measurements so anything we come up with has to has to
reduce to that in some situation but not in others so it's in a very delicate
balancing act when writing down a mathematical theory of this stuff to
something that works with what we know but also explains the weird stuff
suggesting that Newton's fundamental laws of gravitation might be wrong may
seem like an insane thing to do however completely revolutionising the way we
thought is what made these people famous so I spoke to a philosopher Jelena Sami
on the process of completely revolutionize on the way you think what
will happens in specific historical period when the community has to take a
decision and somehow decide whether to embrace Copernicus or not over their
embrace you know lambda-cdm or not and what yeah what are the factors that in a
way explains and justify the formation of scientific consensus around the
theory over open another those raises interesting question I think from a
philosophical point of view because it's a question of looking not just on the
evidence about and how sometimes the evidence can be evidence for alternative
hypotheses and all those different alternative hypotheses can do different
justice to the evidence in terms exactly of explaining versus accommodating
versus evidence from experiment or evidence from computer simulation and I
think those are the questions that philosophers obviously ask so I don't
know I tend to think that obviously it's the job ring of scientist to do the
science and I don't I don't like to think of philosopher system on there
I don't know prescribe or give normative constraints where the scientists should
do but I do think that there are some questions there questions about the
method the models the they roll up the simulation and then the
nature of experimenting there are generally philosophical questions those
are questions that work in scientists that just wouldn't consider as general
scientific questions because they have stemologica questions questions about
human knowledge I will form knowledge of how our knowledge evolved and what
countless reliable knowledge and so in that sense of in philosophy of science
has an important role to play for for science but simply because there are
gaps in there in the normal picture that work in scientists just don't have the
time and don't know if I necessarily did that the skills of the resources to
address and so that's that's the space for philosophers of science I think to
come up chipping and and provide that contribution so we have looked
underground and experiments around the LHC and up into the skies to try and
find out what the nature of dark matter could be the theories that come from
this have ranged from exciting new particles to a perfect fluid just simply
a mistake in our calculations so how we know for sure
well eyes in the future of doctor experiments I speak to dr. Alexandra
Armand to find out what the future of sky surveys holes yes it's a really
exciting time for lensing because there are three ongoing surveys and they're
all in healthy competition but they are really just developmental work for the
upcoming surveys now these upcoming ones will see first light in the next decade
and they will really provide answers for for what dark matter is and where it is
and they'll really deliver high precision astrophysics so there are
three of them and in tandem they'll is where their power lies so there's Euclid
satellites now that will be launched into space and so it will remove our
worry about the effects about atmosphere distorting creating further distortions
in our images and there's also the LSST so the large synoptic survey telescope
now that one is also based in to live and it was Surrey at the night sky every
three nights so it'll just keep cutting around and eventually by stacking all
the images create one of the deepest largest images
of our universe so surveys now will map a size of the sky that's about the size
of a moon for example whereas LSST will do the
entire southern hemisphere so it really will provide groundbreaking things I
think changes for the field and then also in along with there is you have
desease and the dark energy use spectroscopic image and this one this
survey is a bit different so it takes spectroscopic images so instead of it
being optical images of galaxies I think John will talk about this but it will
precisely instead of it being optical images it will take spectroscopic images
and that allows you to see not only exactly where the galaxy is but how fast
it's moving away from us and and when you when you have a combination of
techniques so weak gravitational lensing is super useful for understanding dark
matter but we're at the stage where if you use a combination of techniques and
probes together for our analyses they give a lot of a lot more informative
results so the future of astronomy seems to be looking up but have a direct
detection for dark matter and and have you know potentially an ecosystem of
experiments to borrow a phrase from someone else it's a you know we don't
know what this stuff is Dark Matter candidates span 40 orders of
magnitude in mass so we need to be casting our net you know very wide and
whilst also going deep for those where we think you know we've got the most
chance of finding something at present given technology and given the state of
our knowledge so things like you know a generation 3 Dark Matter detector you
know needs to be built especially if it can open up an inter sort of a rare
event search observatory rather than just being rather than just being wimp
only and expanding to different types of dark matter expand parser as well
neutrino physics and rare event searches and making observatory I think that's a
very that's a compelling case but then at the same time broaden open up look at
all these look at lots of other theories that we can go after but you got a map
that to UK expertise and experience as well you can't just say this is a good
idea let's go try that it'll take time to build up the skills to do that
in many cases but that's fine that's what
we do experimentalist now we go back to Professor Peter Higgs to talk about
where physicists should look in the future for new physics beyond the
standard model neutrinos that we know to me in terms of the experiment
experimental evidence on where theories in particle physics should go neutrinos
are very very important because they I mean they can be accommodated within the
standard model but if you go back to 9 to the 1960s when well say 1960 which
was when Shelly glacier first formulated that an su 2 cross u 1 electroweak
theory it was on the assumption based on what was known at the time that the
neutrinos had no mass now it's clear that clear that that's wrong but but
better so we you know we we can sort of stretch the standard model a bit but it
isn't very natural to have massive neutrinos in it so I think the the
evidence on on the new trainer spectrum and all the parameters of the masses and
the mixing and all all this sort of thing is it's very important but
unfortunately the data come in very slowly so you have to wait many years
before you get the answer well III think that's where the probably where they
present standard bubble is going to be shaken up and and
and there's theoretical directions in particle physics really determined as
the future excites grows so does the need to work together as a scientific
community and collaborate I speak to dr. Shane Reilly who's been working on a
collaborative project luck Zeppelin and they need to work together as a
scientific community and potentially end up doing science as a planet
interestingly right so that's the scale right so ask your Dark Matter particle
gets smaller and smaller your detector has to get much more massive to look for
it and as a result you bring all these people together and you build these
large collaborations and it's actually a beautiful thing right I think I think
there's these physics experiments you know so many Institute's so many
universities from so many countries all working together is a oh in the you know
Oh in the hope of finding something that may or may not exist is a pretty good
moment in human human history things that actually unites countries all right
that's what
you
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