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[Music]
the next talk is by Zara Conrad she's a
PhD student from heidleberg University
and she's giving a foundation talk about
how the Universe
works thank
[Music]
you yeah hello everybody I'm really
amazed how great the interest in this
community is for science this is really
really awesome and I'm really happy to
be here today to talk to you about how
to reverse engineer the universe and by
that we will see that we have to explore
the very very dark sides of the
universe so imagine you are on a on a
very clear night outside You observe the
stars and maybe you wonder what is out
there there are all these tiny little
stars maybe you have images from
colorful nebula in your mind and you
wonder what else is out there and how
far is all that and where does this all
come
from so how people imagined the world to
work in former times is depicted here
and the caption says a missionary of the
Middle Ages tell that he had found the
point where the sky and the Earth touch
so people believe that there is this
curtain in the sky and stars are pinned
on this curtain and they were so curious
and wanted to know the secrets of how
the world works and wanted to look
behind the curtain and see the Machinery
what's going on there of course today we
know that the sky is not a curtain with
stars pinned on them but we know that we
live our sun lives in the Milky Way
galaxy and today we know that the sun is
a relatively average star among all the
other stars we see and in case you lost
track where you are now so you are
here
um yes
so at the beginning of the 20th century
people indeed believe that the Milky Way
galaxy is made the whole universe so the
whole universe consists of our Milky Way
galaxy and everything we observe in the
sky is within our own
Galaxy so you see the world view got a
little bit larger so we went from only
our own little planet to a whole galaxy
this is what we observed but people also
wanted to know how SpaceTime works so
the stuff our Milky Way galaxy is
embedded
in
and how could we investigate this
question without him Albert Einstein in
1950 he found the general theory of
relativity and this Theory made the
essentials for our c
understanding what SpaceTime is and how
it works so I will introduce to you now
the most complicated equation in this
whole talk but this is really the
essentials the essentials of general
relativity is one simple set of
equations on the left hand side they
show the
Dynamics of
SpaceTime so the Dynamics of SpaceTime
is equal to the energy and the momentum
content of our universe what does this
mean in case our universe was empty the
Dynamics would vanish nothing would
happen SpaceTime would just be as it is
but as soon as we fill our universe with
stuff with matter with radiation the
Dynamics of SpaceTime will come into
play and SpaceTime will not stay as it
is the space will expand or contract
will curve and matter will begin to flow
and to go into
movement this sounded really very
strange to people at that time a
universe that changes its
size and people don't wanted that this
was really something people didn't want
so Bett Einstein introduced a further
factor in his equation s
um this Lambda factor to cancel out the
effect of the matter and the radiation
in our universe in order to make it
static so nice and smooth as everything
should
be this equ this further Factor was
allowed by the equations but the nature
of this Factor was really
mysterious is it an unknown energy or a
property of SpaceTime
we will
see this is how our current
understanding of SpaceTime developed but
what about our understanding of our
surrounding as I told you at that time
people believed that the Milky Way was
all our universe consisted of we were
not able to see much further and what we
know today are um other galaxies just a
appeared as spiral nebula in the sky
because individual Stars could not be be
resolved
now Henrietta one levit was a was a
woman who worked at the Harvard
Observatory and she investigated stars
in the large and the small melanic Cloud
now we know that these clouds
are tiny galaxies that accompany our own
MCU Galaxy and at a time she did she she
she worked there she found out that um
we see already individual stars in these
clouds and she observed stars that vary
in their brightness on a range of days
so they pulsate they increase in
magnitude and decrease in magnitude and
what she also saw was that the faster
this pulsation work works the brighter
these stars
are and with this it was possible for
the first time to search for the seate
variable Stars measure their
pulsation now since we know the relation
between the pulsation of stars and their
brightness we observe them in the sky we
can infer the distance of these
stars and this is what Edwin Hubble did
so he found in the
Andromeda uh nebula and the triangle
nebula these seate stars and he used
this method of inferring the
distance and what he found was that
these nebula must be farther away than
all the stars that we can see so for the
first time it was clear that there are
objects outside our own
Galaxy that are are
huge and with that even our own Galaxy
was not a special place anymore just a
place like many others in the universe
and our view from the local neighborhood
evolved our Miku Galaxy here so again
you are here in case you lost track
and the Andromeda galaxy turned out
which we previously believed was only
another nebula in our own Galaxy maybe
tiny is even larger than our own
Galaxy but the
physicist physicist wouldn't be
satisfied with only knowing where stuff
is physicists also want to know how the
stuff move why it moves and all the
Machinery behind that and now in order
to determine how the stuff around us
really works let's make use of another
effect you might know from Acoustics the
Doppler effect imagine you standing on
the street and a fast car is passing by
the sound the car makes while it's
approaching you is different than the
sound it makes when it's driving away
from you it's
like so first it's high and then low so
what you see is that there's a change in
frequency due to the relative movement
of the car and this leads to a change in
pitch now the same is true for light the
physical reasons are a bit different but
the the effect is the same imagine
there's a star that's approaching you
its light will be shifted to higher
frequencies if it's approaching you so
the you will observe a change in color
so the star would appear more blue on
the other way if the star is moving away
from you it will appear more red so why
we call this effect red shift or blue
shift now in order to determine the
relative velocity of a star um with
respect to you it's not enough only to
measure the frequency of the light
because you don't know what the real
color of your star is so for this we
make use of spectral lines spectral
lines are Fingerprints of individual
chemical elements
every element has a
very special line
feature in absorption line feature in
the Spectrum and when you observe a
certain line configuration you know
which element this belongs to and in
principle this line feature should
always be at the same frequencies but
when a star moves towards us or away
from us also these lines are blue and
red shifted which means by observing
spectral lines from from stars that
moving close to us or farther away from
us we know the velocity with which they
move okay now we learned how to measure
distances and how to measure velocities
in the
universe and this was done by Fritz tii
he was a Swiss astronomer and
investigated the velocities of galaxies
in Galactic Galaxy clusters a Galaxy
cluster is very very huge object it's a
gravitationally bound object of
individual
galaxies and what he did was okay he was
interested oh maybe they're like a
mobile they're moving around staying
together and he measured the
velocities and what he found was really
really strange these galaxies moved with
speeds so high such that it was
unbelievable that these guys could stick
together because the the gravitational
potential could not be so high from the
mass we observed we we observed the
brightness of these object we we we knew
how many stars should be in there and
now they are moving with these
speeds Fritz swii concluded that these
Galaxy clusters must be much much
heavier than we actually
observe and then we actually think and
he first introduced the term dark met
for that he believed that dark matter
might be maybe gas or dust or maybe
Rocky material we just can't see because
it doesn't
glow in later times a more detailed
analysis was done by Vera Rubin she used
the same principle but she measured
velocities of stars within certain
galaxies so now we have a Galaxy certain
stars in there and we move we measure
the velocity with which the Stars circle
around the center of the
Galaxy and by that she measured this
profile which you see here is on the
x-axis you see the distance from the
center of the Galaxy on the Y AIS the
speed and the white curve is the
measured speed of these galaxies and as
you see at the center it rises and then
it gets relatively
flat but again from the us we can
observe in these
galaxies we would assume that in order
to hold these galaxies together the
velocity should be much much
smaller and at that time it was already
possible to infer the gas and dust
content of these galaxies so it couldn't
be dust or gas that's in these galaxies
that leads to this excess in Mass so
again we observe that there must be more
mass than we
[Applause]
expected so
our the hints for something like dark
matter got more and
more but let's go back to our view of
how the universe itself works now we
have this mysterious of what's inside
but how does it work
itself again we go back to well-known
edin Hubble and what he measured was
okay um he looked at the galaxies in our
surrounding and he wanted to know with
which um movements are our surrounding
galaxies moving with respect to us and
what he found was the now called Hubble
law that the farther away a galaxy is
the faster it moves away from us so
galaxies are fleeing from us and this is
a linear relationship
but what does this mean today we know
that the Universe expands we call this
Hubble expansion and Hubble would be
really really unhappy about this
expansion naming after him because he
never believed that space itself
expands but okay famous but want it or
not but what does it mean that the
universe expand does it mean that we at
the center of the Galaxy and everything
around us expands no the universe
expands at every point so let's assume
we are at Point
a and we observe a Galaxy at point B
moving away from
us now when we go to Galaxy B what would
someone in Galaxy B see Galaxy B would
also see that a is moving away but
Galaxy B would also observe that
anything else is also moving away
so the universe expands on around every
Point there's no Center where the
universe expands from it expands from
every point and the first one who
formalized this observation was
Alexander Friedman who found the
equations that describe
these specific movement of our universe
he said the universe must be homogeneous
and isotropic meaning
that it looks the same everywhere and in
all directions regardless in which
direction of the universe we look it
looks the same why should it be
different at another point but it
changes in time it expands which means
that if we take a large amount of space
today we go back in time this amount of
space will shrink and shrink and shrink
and become smaller and smaller and by
becoming smaller and smaller it becomes
the matter inside becomes denser and
denser and hotter and hotter and if we
go back in time up to some point
densities and temperatures are so high
such that the Universe becomes
ironized which means that all the
matter the atomic nucle will not hold
the electrons anymore by by them but
electrons and atomic nucle are moving
freely around not being bound to each
other which is depicted here on the left
hand
side but if we are in such a hot dense
plasma what's happening with light light
here is are these yellow curves and
light scatters on free charges which
means that in this hot and dense plasma
so imagine you are sitting there apart
from the fact that you will be cooked um
you could not see anything because the
light skes everywhere and will not
directly reach its aim but at some point
where the universe now expands now we go
forward in time the universe cools the
nuclei catch the electrons and the
universe becomes transparent and at that
time a huge amount of photons was
released and the cool thing is that we
have a picture of this time and this was
one of the most famous pictures in
cosmology we ever saw and I want to
share it with you that it
is thanks to these two guys we have this
picture penas and Wilson they were
working on the hor the Laboratory um on
a radio antenna um I wanted to measure
something completely different and had
always this noisy background in their
antenna and they wanted to get rid of it
they thought this might be pigeon pool
or something else they cleaned their
antenna and anything they couldn't find
out until someday they met a physicist
and they told them him their their
problem and he said what you measured
is the first light from the
universe and for this they got the Nobel
Prize afterwards and they got a Nobel
Prize and physicist got a new toy to
play with because once you have a new
measurement you I mean okay this is
homogeneous and nice and you laughed
because of reasons um so physicists
wanted to know okay is this really so
homogeneous as we see
it and they did computations and comput
mutations I mean today we see structures
in the universe so they might have been
initially also when this uh radiation
was released so do we see reminiscence
of these structures of these initial
structures in this radiation
field and they computed and computed and
thought okay how much matter do we have
in the universe and they computed okay
um I guess we so so they guess the the
fluctuations in this radiation field
must be of the order of 100 Kelvin which
is really really tiny they started
measuring and they found
nothing what was wrong did they do a
mistake in the '90s the cobba satellite
measured For the First Time The
fluctuations of this radiation field and
it turned out that this the fluctuation
amplitude was much much less than
expected it was 100,000
Kelvin and the only
reason that these tiny fluctuations are
so so tiny is that a large amount of the
matter at that time when the cosmic
microwave background this this radiation
was released did not interact with
light so here we have the proof that
dark matter is indeed invisible we will
never be able to see it to take a
picture directly from it because there's
matter in our universe that does not
emit photons that does not interact with
photons that is so completely different
than what we
know the cosmic microwave background
nowadays is much more detailed
investigated and these tiny fluctuations
we see there um here measured by the
plankk satellite a few years ago
um serve as seeds for the big structures
we see today and if you're interested in
how Cosmic structures evolve on these
fluctuations I strongly recommend you if
you don't haven't uh if you didn't have
seen the talk uh on day two by Philip
Bush simulating universes go there have
a look and see how structures are formed
from these fluctuations
today but what do we know now about our
own
universe
you know we still wanted to reconstruct
our own
Universe At the very very beginning
there was the Big Bang so when we go
back in time compress anything at some
point we reach really the zero point
this was a big bang then there was a
brief period we we believe uh of very
very fast expansion called
inflation less than 400 years after the
birth of the big of the
universe we have this release of cosmic
radiation the cosmic microwave
background I presented to you then the
Dark Ages came where no stars were at
that
time then Stars galaxies
formed and then a new Epoch started
which was
confirmed approximately 10 years ago um
which was the accelerated expansion of
the
universe you remember this cosm iCal
constant Factor Einstein introduced in
his equations in order to make the
universe static nowadays we see that
it's not there to make it static but the
effect of this constant is indeed to
make the universe today
accelerating so Einstein invented so to
say dark energy without knowing it but
today we know okay something in our
universe is there to make the universe
further and further expanding regular
mattera cannot do that regular mattera
contracts space but cannot expand
space what do we know about the
ingredients of the universe directly at
the release of the cosmic radiation we
had very much dark matter atoms neutral
and photons played a big role but with
the expansion of the universe their role
became less and less important and today
we know that the density of the the
energy content of atoms make just 5% of
our universe um
today 7 27% is made up of dark matter
and the largest amount of energy in our
universe is dark
energy what do we know about Dark
Energy we know that it is there the
universe
accelerates the other matter and
radiation forms cannot be responsible
for that so something like dark energy
must be here in order to serve for this
accelerated expansion we know that the
energy density is really very
homogeneous in space so it does not form
any structures like meta
does it may be constant in time we have
no hint today that the energy density of
dark energy changes in time so maybe it
stays constant forever then we have this
cosmological constant but physicists of
course don't think okay maybe it's
constant so yeah let's assume it's
constant but let's check that and this
will be checked in upcoming studies up
to an accuracy of 10% so in the next
years we will see does dark meta dark
energy change its density in time or
not and anything else about Doug energy
is highly speculative there are many
different models that predict different
things but nothing known
today so this is all we know about dark
energy for
sure let's go back to Dark Matter maybe
we get a bit more to know about that
what could dark matter be standard
matter that's briefly recap what
standard or normal matter is or the
matter we understand you everybody knows
what an atom is I guess so we have a
nucleus that's positively charged you
have electrons moving around here's this
um yeah the the quantum physic is are
not here today um so but you see what I
mean so in in the core of these atoms um
they are protons and neutrons and every
proton and neutron again is made of
quarks what we know today now what are
quarks there are six kinds of known
today the up Quark down Quark the charm
Quark the strange Quark the top quark
and the bottom Quark physicists
sometimes have humor
[Music]
yes protons and neutrons are made up of
up and down quarks the other quarks are
much heavier and not very stable but
they have been seen in the L C and other
colliders for example then we have the
lepom electron mu toon and for every
electron M Town there is a
nutrino this is regular meta or
radiation in the nutrino case and this
is not dark matter we know that so we
can rule that out one thing at least we
know okay but now we know what it is not
what what might it be maybe primordial
black holes so I told you that when the
cosmic microwave uh radiation was
released the this matter the Dark Matter
could not interact with the photons a
black hole does not emit Photon so it
traps photons so maybe we had at that
time many many black holes
there but the problem with this theory
is all though it could lead to the
observations we we make today that there
are very very few and very exotic
cosmologies only that allow the
formation of primordial black holes
because black holes must have been
formed before atoms
formed and astrophysical observations
allow only a very tiny range of masses
for these primordial black holes so
primordial black holes are not excluded
today but not the likeliest
ones maybe our particle model is not
complete so maybe there are particles in
our St that are not in the standard
model this is why we call this beyond
the standard model particle
physics that are this dark matter maybe
this is particles just like we know but
a bit different how could we detect
them
so there's a certain class of dark meta
particles or model class of dark metap
particles called weekly interacting
massive particles or wimps here just
depicted as dark meta particle and in
case they go for the weak interactions
they could scatter with atomic nuclei
and we could see this scattering in
large large detectors and this is what
is done today so people are looking for
possible dark meta particles that are so
different from what we know but maybe
they interact via the weak
interaction and this is the current
stages of different experiments so the
um the properties we want to know of our
dark meta particle if we detect it um
is what mass does it have and How likely
is it to interact with our other
particles with our normal particles so
let's assume our galaxy is filled with
dark meta particles or wimps we know
what the density of this guy must be
because we know the mass of our galaxy
so the heavier these wimps are the fewer
are they so the number density is lower
if the mass is higher this is one number
we want to know we want to know the mass
and the the size of these guys or the
probability to
interact and this is what these uh
experiments shown here measure so they
want to know okay given a certain Wim
Mass because we don't know what the mass
is there's a plora of models so there's
huge parameter based to investigate um
dependent on the wiim
mass and assuming a given cross-section
would we detect this
particle now the continuous lines shown
here are running experiment so every
line shows given a certain Mass if the
cross-section or the size of our
particle is above the line we would be
able to detect it if the size is below
meaning the interaction probability is
low we would not see
it the dotted lines are experimented
under
construction and what you see here
relatively bad but see in the what you
see here the orange regions so i i i
distinguish the regions um we already
have so in the lower regions of very
very tiny particles if the wimp would be
very very tiny we couldn't distinguish
them from nitrinos so we are blind in
this
region the red area are already running
exper experiments we know that whims in
this range are basically excluded there
were certain um signals which are under
discussion currently which where it is a
bit
unclear did these experiments saw really
something or were these signals from
other
sources and the
dotted um lines are experiments under
construction or in planning and the line
um the the blue green yellow line is one
of the most um forwarded experiment now
which would really go down up to the
nutrino background so if this
experiments will run one day and if
there are whims we could possibly
sometime detect this experiment we'll
see it but
currently everything we saw it looked
really really
bad okay so this is if wimps interact
with our oh normal
material but
maybe there's not a possibility maybe
they don't interact with our normal
material but they interact with each
other so you have two dark meta
particles seeing
here they
interact we say that they might
anihilate because they maybe vanish and
um flow apart to different stuff and
there are many models that say okay in
case we have this kind of model or that
kind of model there must be photons on
neutrinos produced by that and this
Smoking Gun radiation this indirect
detection of Dark Matter this could
possibly be observed here now the
problem with this indirect detection is
that the photons or neutrinos that are
produced there are not
necessarily very um unique so basically
what you have to do is you have to
observe the whole sky for all the
radiation you have to measure all the
photons all the neutrinos know where
they are coming from which means that
um just if you don't know why this
Photon comes here what the source of
this photon is doesn't mean that dark
matter is the reason for for this um for
this
radiation so
[Applause]
so identifying all
the sources in the sky and really
labeling all the stuff we measure here
is is a highly high is of high high
effort and um I wanted really to mention
here um the talks from y mendas on day
one going deep under to watch the Stars
on neutrinos and multimessenger
astronomy the identification of cosmic
radiation and ninos which was by Ani on
day three um so there you see more of
how this Cosmic radiation can be
measured can be
identified and what might be how we can
go on but currently this is really a
really really hard
problem okay unknown party particles
maybe we are about to see what's going
on there but we are already relatively
far so maybe let's consider a completely
different direction what dark meta might
be so maybe it's not a particle maybe we
will never see a particle that we assign
to be um part of not the standard model
and being responsible for the St meta we
observe
so maybe our theory of gravity is just
wrong maybe on large scales or very
large scales the scales of a galaxy of a
galaxy cluster gravity just works
differently than we think so maybe
Einstein was
wrong
now in order to test this hypothesis I
will introduce you with a further
physical effect which is gravitational
lensing so I told you that matter or
energy changes the shape of
SpaceTime which means that if you have a
huge and massive object it will deform
space time will curve space time such
that if you have here massive object and
a shine light to you from behind the
light rays will be curved around this
massive object and this is what you see
here so you see here a photograph of the
Galaxy cluster Abel
2218 and these these arcs you see are
not mistakes in the picture or in the
lens no these are due to the bending of
light of this galaxy cluster so these
arcs you see are galaxies behind this
galaxy clusters and their light is bent
around in SpaceTime until it reaches up
us now the cool thing is with this
method that we
can
by
analyzing the shape of these arcs we can
infer the mass of this galaxy cluster so
we have another independent method to
determine the mass of a galaxy cluster
apart from the velocities in its its
Center so you remember Fritz swii who
measured the G FY velocities he inferred
masses and now we use gravitational
lensing to infer the mass of a cluster
so we have two independent techniques
and let's see what comes out of that
this was applied to the bullet cluster
so the Bullet cluster is a very very
massive cluster and what you see here
the lines are lines of constant
gravitation so to say and you see that
there are two centers of gravity
implying that this bullet cluster
has two components so maybe it was first
two clusters and they moveed to each
other and here we see the centers of
gravity
now in case
gravity Works different
on large scales we would expect that all
the Luminous Mass so or the mass that um
we know the atoms the gas um would also
be there because only the strength
changes so we can look at the gas in
these Galaxy clusters also via another
independent technique not only by
measuring the mass but the gas that
fills Galaxy clusters and the gas that
Galaxy clusters fills the the mass of
this is much much higher than the
galaxies themselves so this is really
the massive part of known matter in
Galaxy clusters is very very hot and it
emits x-ray
radiation which means we can observe
this gas in
x-rays we
measure the mass of the Galaxy cluster
with gravitational lensing we measure
the location of the gas in the x-rays
and what we see is
that the gas is not where the centers of
gravity is here you see the the bright
um regions are denser and hotter regions
of gas so the gas is delocated from the
center of
gravity implying that gravity is not
just scaled the the Gravity from the gas
is not just scaled on on uh larger
scales but there are really different
kinds of mass there one the hot gas
which you see more in the center and
more outside this must be the mass of
our dark matter and the reason why the
gas and the dark matter are delocalized
in this case is because we have here
indeed two Galaxy clusters that moved
through each other the gas felt the
pressure from each other heated up you
see these um Wings going to the middle
so it flew through each other but
heated up and was slowed down whereas
dark matter which does not interact in
that sense just flew through each other
without really
noticing this observation killed a huge
amount of modified gravity models which
assumed just the different strength of
gravity on larger
scales
so modification of gravity there are
still modified gravity models left so
different kinds of gravitational
theories apart from uh the general
theory of relativity which are
possible but let me tell you that one
further observation also killed a lot uh
of these models was that um the neutron
star merger uh in the past time maybe
you um
uh you heard about that that uh since we
have this gravitational wave detector
there was a neutron star merger detected
and for the first time this was really a
huge Discovery in multimessenger
astronomy because this neutron star
merger was observed via gravitational
waves in and Via photons and Via
neutrinos so the what we saw was that
the speed of the gravitation
of the the gravity of the gravitational
waves that reached us and the speed of
the light emitted from this neutron star
merger was the same and this was also
something that was is is not predicted
from from certain modified gravity
theories so there are there were many
many modified gravity theories who
predicted that the speed of light is
different from the speed of gravity but
now we know the speed of gravity is the
same as the speed of light
which
also improved our knowledge about
gravity itself and is a further reason
for general
relativity so these are the most common
models or ideas we have what dark
mattera might
be there maybe it is something
completely different something we cannot
imagine of but
this is hard to detect something we
cannot
know what do I want you to take
home
we saw How the Universe our our view of
the universe evolved especially in the
past
Century we know that today only 5% of
the energy content of our un iers is
known to us these are the atoms which
make up the gases the dust the Stars the
Earth us this is only
5% 5% of the stuff in our universe is
something we can possibly ever see the
other stuff we will never
see in the visual
regime
27% of the energy content of our
universe must be something like dark
matter and excess in in
Mass we cannot explain currently with
different
models maybe it is a
particle we don't
know and the largest majority of the
energy conted in our universe is this
strange thing called dark energy that
stuff that made our univer makes our
universe EXP expanding in an accelerated
way and since we have no other reason to
believe differently the future of our
universe will be the cold death
everything will expand farther and
farther it will become colder and colder
because it gets less dense and less
dense and maybe this goes up to
Infinity
maybe there's something else coming in
we don't see yet but we don't know all
we know is that these three components
are nowadays the most important
components and that 95% of the stuff is
literally in the dark but we will know
better in the future so stay tuned and
explore the dark thank
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you
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let come time for Q&A as far as I know
there are some questions from the
internet if you have some questions to
stand up to the microphones that are
over there and this I think too but
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first thank you what do you think about
the theory of higher Dimensions like Str
Theory forms such as B brain or PR brain
yeah so string theory has a hard time to
make predictions that are actually
testable
and and I guess this is a very at least
for me this is really one of the most
important things to follow a theory it
is absolutely worth developing these
theories because we learn a lot from
them but now at at least now I don't
think that they are of much relevance
for us
now and the next
one um has there been research about
effect of inhomogeneities on the
accelerating expansion of the universe
thinking about the big voids that we
observe in the cosmic
structure so um what effect sorry where
are
you this was from the internet oh this
was from the internet could you repeat
the question question please yes sure
has there been research about effects of
inhomogeneities on the accelerating
expansion of the universe so there there
is um definitely research on how in
homogeneities especially voids affect
the expansion of the universe itself and
it has been shown that only voids cannot
be responsible for the accelerated
expansion so only with these
inhomogeneities you don't arrive at the
cosmology we
observe thank you internet uh microphone
number two please when you show the
picture of baby Universe very cute by
the way thank uh why it does it have an
elliptic shape um oh yeah thank you good
question I forgot to mention that so
this is a whole world view so to say
it's like a map of the Earth but
projected to the sky so when you have a
map of the Earth it's also an elliptic
shape so it's a whole um world whole Sky
View so to
say Thank you so uh microphone number
one please and speak like me directly to
the mic because someone else can hear
you then um How likely or unlikely do
you think it is that there's maybe a
fault in the measurements we did which
which indicate to us that there must be
something like dark metal like that
rotation of the
galaxies how how how sure it is that all
those measurements are correct and there
must be something we don't know of all
all of what is
correct measurements which indicate that
must there must be dark matter like the
rotation of the
Galaxy they are they are nowadays we
live so this is a term that is very
often used on cosmological conferences
we live in an age of high Precision
cosmology which means that the values we
we can measure nowadays are really
really very very
precise
yes Mike number three please is said for
the dark energy that there is some new
information about the temporal structure
that we get can you elaborate a bit on
that experiments or measurements uh will
give information there yes uh so um uid
and lsst so the large scale Sky survey
will uh give at least up to some
accuracy hints so if there is a strong
temporal change in the dark energy
content H density in our universe we
will get a hint for that if it's very
weak of course we cannot see that then
but in the next years we will get more
information on that
yes we increment to number
four uh yeah hi uh you said that a
measured energy fluctuation in the
cosmic microwave background was much
much smaller than the expected uh
flation yes uh can you uh and the factor
was around 1,000 times smaller can you
give the meere reason for this uh large
Factor yes so the reason is that um we
have only a fifth of the matter that is
that could be responsible for this
fluctuations does indeed interact
directly with the photons um which means
that the fluctuations you see in the um
in this radiation background
follows the fluctuations of the matter
but only of the matter it interacts with
and if it interacts only with a tiny
fraction of the matter the amplitude of
these fluctuations will be much much
smaller than if it would interact with
the whole amount of
matter number two
again thank you for your talk it was
very interesting uh one question the
ballet cluster and given that the large
uh dark metal masses apparently didn't
interact with each other doesn't that
rule out the uh Smoking Gun uh
measurements for dark
mattera um so the probability that dark
meta particles interact is assumed to be
very very low so you wouldn't see it if
to or I mean you would have
events while two Galaxy clusters move
through each other but they are so few
that you don't see that directly in the
structure so you really have to measure
individual events and the photons and
the neutrinos then so it's only very
very rare events that would appear there
because of course otherwise we would see
it if we had strongly interacting duck
self- interacting duck matter we would
see that in the structures we
observe so we have another microphone
number five in the
back hey thanks for including me in the
questions um basically basically it's a
kind of ad adver for my friend physicist
which get a theory of um giant
primordial photons dropped by gravity
have you heard of
that H I guess I didn't understand the
theory can you repeat that it is like in
the beginning of the univers that were
created the kind of photos that mass so
giant actually were trapped by the
gravity I don't guess I heard about that
but maybe you come by later and we have
a chat about that sure you can find his
talks on quora.com
his call his thank you so number one
please you you showed us the slide with
the the experiments for detecting wimps
how far into the mic into the mic thank
you sorry it's set up for someone taller
than me um how how long do you think it
will be before the the wimp uh detecting
experiments actually either detect wimps
or prove that we're not going to detect
them that way and if we don't detect
them with those experiments if we gave
you a blank check what is the experiment
that you would do to help put this one
to rest once and for
all okay so the question when we already
decided decide this so I showed you
experiments that are in planning
currently that there are many political
and Technical decisions inside it when
they start to run so I cannot comment on
that regarding experiments to decide I
mean we try to of course what is tried
I'm not in this kind of experiments uh
what is tried is of course to extend the
range in all directions but if we are
not able to
detect ever this kind of
um this kind of um particles we really
have a problem because then we don't
know what to look for if it's a particle
because maybe it has some exotic kind of
interaction so we have to look deeper
and deeper and up to more accuracy um so
what people do now is to investigate
heavily um structure formation because
the depending on your model of the stuff
that forms the structure structures
might turn out to be a bit different and
to measure these subtleties so we then
get from a theory driven approach to see
okay what comes out if we assume this is
this comparable to what we observe or
not uh number three
please yeah thank you um I have a
question uh to this dark energy and this
accelerated expansion I hope I can pick
it into a question
um we observe galaxies that are very far
away so the the more far they are away
the older they are and it is assumed
that in each Galaxy we have a super
massive black hole and black holes um we
can nothing we can say nothing about it
so one of the effects is that yeah okay
um one of the effects is that they eat
up even light and um maybe this this
observation we have that we interpret as
dark energy Sor what's the question um
it's coming okay I I
try um that the effect we see that we
interpret as dark energy maybe it's a
misinterpretation of what we see and
that it's an effect of the masses that
uh that masses have uh on light and that
there is no acceleration and we only
interpret this this what we see as a
douer effect um yeah that that we
interpreted as an acceleration but
instead it's an effect of Mass on light
I am very very sure that um this is
excluded by the observations we can see
because our cosmological model we
developed um would take this effect into
consideration if it was uh responsible
for this observation that lead us to the
Assumption or to the conclusion that the
Universe expands
accelerated so this can be excluded yes
thank you and sorry for me being stupid
number four hello thank you for your
talk um it's always stated that the
universe is expanding from how what I
understand is that there's new space
created could it be that dark energy is
the energy which is needed to create
space face itself um this is basically
the interpretation so the the idea is
that dark energy has something we call
negative pressure in contrast to um
Regular metal and radiation which has a
positive pressure and this negative
pressure leads to an expansion of the
universe so yes dark energy is
responsible for this accelerated
expansion number
two have you considered that the
inability to answer some questions about
energy indicat that we reach the
boundaries of our current uh physical
models or rather um have you consider
that that is a different completely
different contradicting model of physics
and or mathematics um that would be
required to ask these
questions so um models are models
because they are only subsets of what we
describe because otherwise they would be
called reality so indeed a model is
never complete um the question is when
is a model contradicting something I
mean does the standard model of particle
physics contradict that they are other
particles I have a bit problems to
saying they contradict at least they are
not complete we know obviously they are
not complete because we observe stuff we
cannot explain now the point is that
to say okay what is um likely or less
likely depends absolutely on your point
of view because you have to to to look
okay I I have to drop an assumption we
made a general assumption for example
like homogeneity of the universe when I
drop that is that less strong than
dropping the assumption that
um there are no other particles for
example and this is hard hard to
quantify Which models are more likely or
less likely but I wouldn't I wouldn't
call it a contradiction nowadays I would
call it
incomplete I'm sorry the Q&A finishes
now please a warm hand and a warm
Applause for Sarah Conrad thank
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you
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oh