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
