um
theoretical physicist and I’m here
tonight to tell all of you how
successful physicists are in describing
everything ranging from the size of
elementary particle up to the size of
the entire universe or maybe I’m gonna
tell you what we just don’t understand
ok let’s start tonight I’m gonna tell
you about just two of the most beautiful
theories physicists have created the
last one is the standard model it
describe the interaction of every single
elementary particle and their
interactions is it electromagnetics like
Latrese it you’re the light that comes
from the Sun weak the force responsible
for radioactive decay or force that is
strong the force that keeps together
nuclear matter or in the other case I
will tell you about the masterpiece of
Albert Einstein general relativity the
theory that tells our energy and matter
act on space and time banding them to
give rise to gravity these two are two
terrible predictive theories they are
capable of making prediction out of
measurement as precise as ten million of
millions in precision imagine you make a
measurement and then you can predict
this measurement for 13 digits of
precision is impressive yet I’m a
physicist and as such and as my
community dollars we go around to look
for pitfalls in our theories so we’ll be
thus paramount and in order to study the
first of these theories we built the LHC
is the most gigantic experiment ever
built on earth it’s a ring just a ring
27 kilometers
buried hundred-meter under the ground
LHC is in Geneva and what it does it
just accelerate a bunch of protons up to
a speed at ISA 99.999999 1% speed of
light and he makes it collide against
another bunch of proton that is rotating
in the opposite direction like this and
we just look for the outcome of this
collision you may think of this as
taking two car as much in time together
and then going around and looking for
the outcome
oh this is a wheel ok walks more relaxed
like oh it doesn’t work too well there
is something strange of particle physics
we know very well that when we collide
two particles it may happen that you end
up with a third particle that is
actually heavier than the two original
particles and no one here hopes that you
takes two voxel car you smash them
together and you get two Ferrari ok it
works like that for particle physics so
we switch on the LHC and we start one
out of the other to find all known
particles up to the last one and the
entire physics community is super
excited yeah every time we find a
particle we are super excited knowing
this one is special is the Higgs boson
you may have heard of it as when he was
discovered in 2012 it had a great huge
really media coverage the special
property of the Higgs is that it emits a
field
what’s a field we all have an experience
of a field whenever you take a magnet
and a piece of metal you will feel that
the magnet and piece of metal are
attracting each other this is the result
of the magnetic field
well the Higgs field is something
similar with major difference is that
the Higgs field
percolates the entire universe and it’s
just by mean of the interaction with the
higgs field that every single elementary
particle get mass hard to imagine no
wait it’s easy think of the higgs field
as a gigantic pond of trickle the more
you interact with the trickle the
heavier you are the less you interact
with a trickle the lighter you are so
you may understand that as this Higgs
field is at the basis of the mass of the
entire set of elementary particle we
really need it is the cornerstone of our
building at the standard model it was
predicted and we needed it to build the
standard model so in the end when we
found it we were very excited but as
soon as we found it in our mathematical
understanding we already knew that there
was something wrong indeed the Higgs
field in our opinion is either on or off
and when I mean off I mean zero nothing
now no way and when I mean on is
terribly on and instead we measured it
what we discovered that the Higgs field
is an either or nor off it’s actually
you know this switch that cannot switch
off properly it’s a bit broken sweetie
honest with you this is a what luck
since should the Higgs field ever had
the value that is in any way different
from its actual value all the known
matter would collapse in point-like
objects hmm not too bad for someone who
started saying we do understand
everything okay maybe I should have been
more humble and say we’re very good in
particle physics and but we don’t know
where the mass come from and the energy
of the particle and their origin mmm
wait that’s just the first of the open
question of tonight maybe it’s gonna get
worse I spoke about two theories and the
second theory is the theory of
relativity Albert Einstein and when I
speak about relativity I think about the
gravity saw interaction of planets stars
galaxies clusters
and what do you do as aspera meant is
just you take a picture of the sky in
all the possible different
electromagnetic ranges but it’s just the
picture of the sky this is for example
the gaia telescope and what we do is we
just take this picture and we classify
our findings this is a galaxy this is a
star and you may end up finding
something like this beautiful isn’t it
it’s a rotating galaxy it’s an object
that contains something between 1
million and 1 billion of stars and that
is a scale you cannot distinguish what
the solar system is and what is
interesting of this object is that it
rotates around its axis and out of
everyday experience we would expect that
as the vast majority of mass is in the
middle the speed of rotation of the
middle should be higher than the speed
of rotation of the object that are
further out let me give you as usual an
example think of a cappuccino ok you
look at the foam and you start to stir
it with your teaspoon the foam in the
middle we spin faster than the foam
closer to the border okay it has to work
like that more or less so we went there
and we measure it and what we found was
a surprise yeah what we found was that
the speed of rotation is the same in the
middle and out no wait this is wrong we
can’t understand it it is so wrong that
we have to imagine that there is
something hidden in that picture that
I’m not seeing there must be something
else in this picture but I can’t see it
so I call it the dark weight whenever a
physicist tells you dark it mostly mean
we don’t understand it
ok so dark no we don’t understand it
good anyway let’s assume that there is
something dark and is interacting
gravitationally so
Dark Matter let’s count how much that
matter do I need in order for the galaxy
to spin to rotate properly okay very
good I can do the calculation and scale
it up to the size of the entire universe
is that oh my god
bright matter the matter that we know
that they have described it so far with
my beautiful theories is just 15 percent
of the balance of mass of the entire
universe I need a chance to explain the
rotating structure and 85% of dark
matter not too bad
we do understand everything I said the
three open question okay
a third point that I want to tell you
about is that what we believe and what
we have actually measured very precisely
is that our universe is expanding if I
measure and if I look at every other
point and object that is around me I
will see it going away how do I
understand that well in our opinion what
it happen is that more or less 14
billions of years ago everything all the
structure was collapse in a single point
in space and time and then a fluctuation
an explosion gave rise to all the known
structure starting from a small blob of
very energetic hot and dense plasma that
then eventually fly out of the explosion
very good it makes sense out of an
explosion you are sitting on a piece of
debris call it earth and you’re looking
around you and everything is going away
fine it works good wait what aspect
should that be the case is that all
these bits and pieces are interacting
only gravitationally good but I would
respect that the relative speed with
respect to every other object I see
around should decrease let me give an
example consider for a moment a stone a
pebble from the beach the earth interact
okay they attract each other
gravitationally and let’s see
imagine an explosion myself taking the
stone and throwing it India okay what
will happen is as soon as the stone
leaves my hand the speed of the stone
with respect to the hurt wind decrease
will get slower and slower and
eventually we stop and fall to the
ground but this is only due to the fact
that I’m not strong enough to throw the
stone out of the influence of the
gravitational field of the earth should
have been strong enough the stone the
earth yet I would expect that the
relative speed of the stone with earth
should decrease with time okay this is
our expectation and then we can go and
measure it and we can measure the speed
of the expansion of the universe one
billion of years ago and the speed of an
expansion of the universe today and what
we discover is that the speed of this
function of the universe one be smaller
than today wait smaller the universe is
accelerating what’s going on I mean in
order for something to be accelerating
in an Ongina
a propellor something that pulls out you
from the interaction with the other
bodies now it can be I don’t understand
it okay I call it dark and that’s it but
is a fueling this explosion so I call it
dark energy very good
terrible so he can go back to the
drawing board I’m a physicist and they
can evaluate how much dark energy do I
need in such a way that the universe
could expand the rate at which is
responding and then I need to compare it
with something and thanks again to
Albert Einstein using the famous
relation e equal MC square I can compare
energy with mass so let me compare
energy with let’s say the mass of the
universe something comparable
okay and what I discover is that in the
balance of mass and energy of the entire
universe what we know nowadays is the
bright matter just 5% the dark matter
the object that I need for the universe
to rotate properly is 27% and what I
need to let the universe accelerate
properly dark energy is 68% now my talk
and here as I clearly don’t have any
answer for these three open question the
origin of mass for the particles the
nature of dark matter and the possible
explanation for dark energy there are
candidates theory candidates that could
explain the origin of the mass there are
possible matter candidates for the dark
matter and there are possible
explanation for the structure of dark
energy but these are just theories that
needs to be validated and maybe that’s
the reason why it’s great to be a
physicist today thank you very much
[Applause] you