[Applause]
is the universe static and he
perpetual expansion and will it continue
to dilute tirelessly on the contrary
the universe Will he answer and a
big crunch that is to say a collapse
complete on itself in sum what is
our cosmic destiny
it’s finally quite recently that
astrophysicists began to respond
to some of these questions some
partial answers that not far from
repel the unknown call in made to
new questions and raises of
new mysteries we speak today
of a dark sector of the universe a
part of the universe that we know to be
there but whose nature we do not know
to tell you the story of this side
obscure of the universe it actually takes
return 100 years back in 1915
albert einstein postulates his theory of
general relativity that describes the
gravitation gravitation this force
which makes that if I loose an apple the
apple will fall to the ground as your two
feet are well hung on the surface
terrestrial or that the earth turns
around the sun
this force she is described as a
manifestation of the deformation of
the space time what is it
space time is the idea that if one
wants to spotted an event in the world
you have to give 3 spaces coordinates
and a time coordinate for albert
einstein the space and the time are
indissociable and form what we
could call the space weft
time then any massive object is going
distort this space time like a
ball placed on a stretched sheet and all
small distortion of space time is going
put in motion the objects that the
up
returning the example of the apple by
example the earth is very massive
she digs a well in space-time
the apple that I loose will fall to the bottom
of the well and stay there trapped then when
albert einstein publishes his theory of
general relativity
he manages right away to understand
what are the possible fates of
the universe predicts by his theory of
gravitation
in fact there are only two possible
the universe is either expanding or
contraction but expansion contraction
these are two possibilities that do not
absolutely do not like to einstein to his
contemporaries who believe hard as iron
a universe that would be static frozen and
immutable that would not evolve in the
time would always be the same and
would therefore have no beginning or end
so let’s see that his own theory does not
can predict the static universe to which
he believes albert einstein decides to play
accountants and balance the
cosmic accounts
if the universe has too much mass and it’s going
therefore contract under the effect of its
hand we can add a small parameters
a constant in the equations that goes
counterbalance exactly this effect of
gravity and allow the universe not
more to be in contraction but to
to be able to stay at the balanced
this constant is the constant
cosmological einstein
in fact she is not very
satisfactory and this is an observation
in the 20’s that goes completely
upset our perception of the world
this observation is that of beule
and the master who will discover that the
galaxies around us is moving away all
we flees with a speed all the more
great that she is far away then the
verdict is final
if we believe in the principles
copernican ie we
do not occupy a privileged place
in the universe that the universe and the maine
in all points and in all
directions
then necessarily the escape of
galaxies means that the universe is in
expansion to understand what
Cosmic expansion is often used
an image that of a cake nuggets of
chocolate that we would bake then
the cake under the effect of the yeast goes
inflate swollen inflated he is expanding
the little chocolate chips on this
cake that are the galaxies you have it
including his chocolate chips before
everything away from each other
because the frame on which they are
asked ie the cake dough is
itself expanding
so that’s a fact the universe is in
expansion
it’s not static and the constant
cosmological einstein is no longer
necessary he decides to remove it from
these equations and would qualify it said one
of biggest mistake of his life a
mistake maybe but in fact this
constant does not disappear completely
she reappears regularly and ends
even by making a definitive return there
twenty years in the years
90 when a new observation comes
once again upset the deal
we discover that not only the universe
is expanding but it’s actually in
accelerated expansion more and more
quick
this observation she is totally
counter intuitive the gravity of a force
attractive it should slow down
cosmic expansion and yet what
we observe it is good that the universe
is expanding rapidly and
have not slowed down so we have to find
what’s driving this acceleration
cosmic
it could be the constant
cosmological einstein it’s true but
it’s not the only possible scenario
other options are being considered on
think for example
that maybe the universe would be filled
in dark energy fluid that
would have physical properties by
example a negative pressure that him
would give an ultimately repellent effect
the reverse of gravity it would allow
so to the universe to accelerate his
expansion
this is the first option a second
would be that our theory of
gravitation the general relativity which
is so well tested so well known to our
scale may not be the right one
theory of gravitation to greater
scale at the scale of the universe
she might need to be
modified to be amended finally another
possibility for and is that the principle
Copernican may not be verified
that maybe we’re actually doing a
privileged place in the universe this
would be the case for example if we
live in the middle of a big emptiness
cosmic then answer these questions
find and the engine of acceleration
cosmic is really one of the most
big unknowns
if it is perhaps the biggest
unknown to cosmology today and
it’s ultimately exactly the object of
my job I am an astrophysicist and
I participate in the preparation of a
space mission called the
euclid mission that will be launched by the
European Space Agency in three
years and France is also one of the
main contributors to this mission
the cniid
this space telescope will be able to observe
about 2 billion galaxies
over the last ten billion years
of evolution of the universe then clide
it’s already a technological feat
we will send an infrared camera the
largest ever sent into space
we will send an optical camera that has
such precision with 600 million
pixels that imagine if we placed it at
marseille we could detect no less
than a fly on a soccer ball at
Princes Park
euclide is also a feat
computer we’re going to have a quantity of
very important data to be processed on
supercomputers to give you
an idea is about 170
petabytes of data
so if we store all this data
on hard disks we had fun at
stack the hard drives to make a
very big stack this pile she
would reach 2.6 km high ie
about 7 stuffer state building them
on each other
euclide is also a feat
observational a theoretical feat
because we try to observe and model
effects that are very fine and which
poses a number of significant challenges
with this project this space mission
we hope to be able to detect
to study what is the engine of
cosmic acceleration and for that
we will have two tools to our
provision the first tool it will be from
map the galaxies that is to say
to spot how galaxies are
distributed in the universe and how
this galaxy distribution evolved
with time
so we will know if the constant
cosmological is a constant if
maybe it depends on the weather at
contrary and in this case the engine of
cosmic acceleration could be a
dark energy fluid a second
tool that we will use will be no
only to map the galaxies
but also to measure their shape
because the universe is like a giant magnifying glass
the light rays that cross it
will be deflected because of the universe
himself from the whole mass of the universe
this effect is an effect that is purely
gravitational is therefore measuring the
deformations of galaxies ie
measure the effect of cosmic magnifying glass we
lets just test the
gravitation and hopefully of
discover abnormalities of the small
clues that would allow us to say that
maybe the theory of relativity
general needs to be modified at
the scale of the universe then
I give you an appointment in a few
years to discover together the
results of this mission to the cniid
discover what is the engine of
cosmic acceleration
is it a dark energy fluid
who would banish the universe is this a
manifestation of the fact that relativity
general needs to be modified at
the scale of the universe or maybe
is it simply the
cosmological constant this constant
kane stein had initially
introduced by mistake for reasons
which are no longer valid today
answer these questions it’s
understand the history of our universe
understand our origins but also our
cosmic destiny
Thank you
[Applause]
is the universe static and he
perpetual expansion and will it continue
to dilute tirelessly on the contrary
the universe Will he answer and a
big crunch that is to say a collapse
complete on itself in sum what is
our cosmic destiny
it’s finally quite recently that
astrophysicists began to respond
to some of these questions some
partial answers that not far from
repel the unknown call in made to
new questions and raises of
new mysteries we speak today
of a dark sector of the universe a
part of the universe that we know to be
there but whose nature we do not know
to tell you the story of this side
obscure of the universe it actually takes
return 100 years back in 1915
albert einstein postulates his theory of
general relativity that describes the
gravitation gravitation this force
which makes that if I loose an apple the
apple will fall to the ground as your two
feet are well hung on the surface
terrestrial or that the earth turns
around the sun
this force she is described as a
manifestation of the deformation of
the space time what is it
space time is the idea that if one
wants to spotted an event in the world
you have to give 3 spaces coordinates
and a time coordinate for albert
einstein the space and the time are
indissociable and form what we
could call the space weft
time then any massive object is going
distort this space time like a
ball placed on a stretched sheet and all
small distortion of space time is going
put in motion the objects that the
up
returning the example of the apple by
example the earth is very massive
she digs a well in space-time
the apple that I loose will fall to the bottom
of the well and stay there trapped then when
albert einstein publishes his theory of
general relativity
he manages right away to understand
what are the possible fates of
the universe predicts by his theory of
gravitation
in fact there are only two possible
the universe is either expanding or
contraction but expansion contraction
these are two possibilities that do not
absolutely do not like to einstein to his
contemporaries who believe hard as iron
a universe that would be static frozen and
immutable that would not evolve in the
time would always be the same and
would therefore have no beginning or end
so let’s see that his own theory does not
can predict the static universe to which
he believes albert einstein decides to play
accountants and balance the
cosmic accounts
if the universe has too much mass and it’s going
therefore contract under the effect of its
hand we can add a small parameters
a constant in the equations that goes
counterbalance exactly this effect of
gravity and allow the universe not
more to be in contraction but to
to be able to stay at the balanced
this constant is the constant
cosmological einstein
in fact she is not very
satisfactory and this is an observation
in the 20’s that goes completely
upset our perception of the world
this observation is that of beule
and the master who will discover that the
galaxies around us is moving away all
we flees with a speed all the more
great that she is far away then the
verdict is final
if we believe in the principles
copernican ie we
do not occupy a privileged place
in the universe that the universe and the maine
in all points and in all
directions
then necessarily the escape of
galaxies means that the universe is in
expansion to understand what
Cosmic expansion is often used
an image that of a cake nuggets of
chocolate that we would bake then
the cake under the effect of the yeast goes
inflate swollen inflated he is expanding
the little chocolate chips on this
cake that are the galaxies you have it
including his chocolate chips before
everything away from each other
because the frame on which they are
asked ie the cake dough is
itself expanding
so that’s a fact the universe is in
expansion
it’s not static and the constant
cosmological einstein is no longer
necessary he decides to remove it from
these equations and would qualify it said one
of biggest mistake of his life a
mistake maybe but in fact this
constant does not disappear completely
she reappears regularly and ends
even by making a definitive return there
twenty years in the years
90 when a new observation comes
once again upset the deal
we discover that not only the universe
is expanding but it’s actually in
accelerated expansion more and more
quick
this observation she is totally
counter intuitive the gravity of a force
attractive it should slow down
cosmic expansion and yet what
we observe it is good that the universe
is expanding rapidly and
have not slowed down so we have to find
what’s driving this acceleration
cosmic
it could be the constant
cosmological einstein it’s true but
it’s not the only possible scenario
other options are being considered on
think for example
that maybe the universe would be filled
in dark energy fluid that
would have physical properties by
example a negative pressure that him
would give an ultimately repellent effect
the reverse of gravity it would allow
so to the universe to accelerate his
expansion
this is the first option a second
would be that our theory of
gravitation the general relativity which
is so well tested so well known to our
scale may not be the right one
theory of gravitation to greater
scale at the scale of the universe
she might need to be
modified to be amended finally another
possibility for and is that the principle
Copernican may not be verified
that maybe we’re actually doing a
privileged place in the universe this
would be the case for example if we
live in the middle of a big emptiness
cosmic then answer these questions
find and the engine of acceleration
cosmic is really one of the most
big unknowns
if it is perhaps the biggest
unknown to cosmology today and
it’s ultimately exactly the object of
my job I am an astrophysicist and
I participate in the preparation of a
space mission called the
euclid mission that will be launched by the
European Space Agency in three
years and France is also one of the
main contributors to this mission
the cniid
this space telescope will be able to observe
about 2 billion galaxies
over the last ten billion years
of evolution of the universe then clide
it’s already a technological feat
we will send an infrared camera the
largest ever sent into space
we will send an optical camera that has
such precision with 600 million
pixels that imagine if we placed it at
marseille we could detect no less
than a fly on a soccer ball at
Princes Park
euclide is also a feat
computer we’re going to have a quantity of
very important data to be processed on
supercomputers to give you
an idea is about 170
petabytes of data
so if we store all this data
on hard disks we had fun at
stack the hard drives to make a
very big stack this pile she
would reach 2.6 km high ie
about 7 stuffer state building them
on each other
euclide is also a feat
observational a theoretical feat
because we try to observe and model
effects that are very fine and which
poses a number of significant challenges
with this project this space mission
we hope to be able to detect
to study what is the engine of
cosmic acceleration and for that
we will have two tools to our
provision the first tool it will be from
map the galaxies that is to say
to spot how galaxies are
distributed in the universe and how
this galaxy distribution evolved
with time
so we will know if the constant
cosmological is a constant if
maybe it depends on the weather at
contrary and in this case the engine of
cosmic acceleration could be a
dark energy fluid a second
tool that we will use will be no
only to map the galaxies
but also to measure their shape
because the universe is like a giant magnifying glass
the light rays that cross it
will be deflected because of the universe
himself from the whole mass of the universe
this effect is an effect that is purely
gravitational is therefore measuring the
deformations of galaxies ie
measure the effect of cosmic magnifying glass we
lets just test the
gravitation and hopefully of
discover abnormalities of the small
clues that would allow us to say that
maybe the theory of relativity
general needs to be modified at
the scale of the universe then
I give you an appointment in a few
years to discover together the
results of this mission to the cniid
discover what is the engine of
cosmic acceleration
is it a dark energy fluid
who would banish the universe is this a
manifestation of the fact that relativity
general needs to be modified at
the scale of the universe or maybe
is it simply the
cosmological constant this constant
kane stein had initially
introduced by mistake for reasons
which are no longer valid today
answer these questions it’s
understand the history of our universe
understand our origins but also our
cosmic destiny
Thank you
[Applause]
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