the sound you just heard
repeated several times is the sound of a
signal produced more than a billion
years ago by a system of two black holes
more than a billion from us
light years
these two objects have orbited for
millions of years
one around the other they approached
more and more at the end of them
life merged to form a single
object a still massive black hole
greater
this generated signal has traveled
in the universe and September 14th has
reached the land where it was
detected for the first time as a wave
gravitational
so I’ll talk to you about this today
discovery of gravitational waves
it means talking about time space of
gravitation of celestial bodies
of the universe and of those instruments that
over the centuries they have been
perfected more and more to be able to
to investigate
what you see here is a step
fundamental in understanding
of the universe when in 1609 Galilean
with his telescope for the first
Once you look at the sky, what you see
it is the observation of Jupiter and his
satellites
well this new window
on the universe this new way of
observe the universe represents one
epochal turning point not only
scientific but also social heritage
of galilei was collected by isaac newton
that
the first formula is the mathematical laws
that describe how the planets move
around the sun
not only but also that they say as i
bodies on earth fall attracted towards
the bass from the gravitational force
terrestrial
however the decisive turning point in the
understanding of the universe arrival a
a few centuries later in 1904 albert
einstein published his own in 1915
general theory of relativity
this was some time later considered
like the new theory of the universe
a revolution in science that
the concept definitely exceeds
Newtonian of space of time and of
gravitation and see the cover here
of the time magazine that somehow
seals the weight that this man who
this scientist had in life and
in the twentieth century culture
according to newton, space is something of
rigid and the bodies move to his
interior attracted by that force
gravitational that brings them one
towards others
according to einstein crane space is not
a rigid entity but under the action of
a mass is deformed can be
imagined then as a membrane
this deformation is elastic
this curvature causes movement
of the celestial bodies imagined to take
a smaller mass by stamping them one
some speed this naturally yes
will rotate around the mass
bigger
so you see is the new geometry
geometry of space that tells the bodies
how to move and are the bodies that say
to space as curving, however, not
it is only space that is influenced
from the mass distribution also it
time passing and clocks placed in
stronger gravitational fields are beating
the seconds more slowly
then you create a new entity the
time space time is no longer
something absolute but its flow
its flow depends on
matter distribution and this fact
it is very present in our life
daily makes general relativity
something close to ours
everyday we all have a
cell phone in every cellphone
There is the GPS global positioning
system you know that it works through
a communication of the object a
earth with satellites and time
it flows differently in the satellites and here
on earth and if they were not applied
the corrections of general relativity
we will not observe the great precision
that instead this system can give us
in positioning objects here
on earth
the degree of curvature of the structure
time space depends on the
mass concentration if instead of
consider the sun we took to
example a neutron star which is a
object that has a mass of about one
half past that of the sun but
enclosed in a volume much more
a small radius is about 10 km
therefore a great concentration of
mass of training in this
temporal space membrane will be
clearly much deeper and still
more happens in the case of a black hole
a mass concentration even more
great
the gravitational field around one
black hole is so strong that whatever
object approaching sufficiently
surpassing what is called the horizon
of events would no longer be able
to escape the very strong gravity
not even the light once entered
within the event horizon
they may have managed to get out of it there have been
many predictions of relativity
general black holes are one of those
another was made by einstein in 1916
the year after the publication of the
general relativity
and it is the prediction of the existence of the
gravitational waves
now the membrane we have seen before
with the mass
imagine you swing this mass
top down to speed it up
this way waves will be generated in
this temporal space structure of the
waves that propagate when traveling to
light speed
if instead of considering a single
mass we consider two celestial bodies that
orbit one around the other also
these will produce waves of
gravity of the deformations of the
ripples in the space time that is
they will move away from the source by traveling
through the universe
it is these small ripples of the
space structure in and to that
last September we managed to
measure how we can measure these
effects to understand it we must understand how
the gravitational wave interacts with the
matter what is the effect it causes
now imagine and consider this
distribution of masses along the
rings
a gravitational wave that travels
perpendicular to the plane
see the moves are ribbed in
swing their distance changes
they are stretched and compressed and then
the effect reverses and so on
here are just these oscillations
that we have measured oscillations
of time and all space
objects that are contained in it
these oscillations are very small and
very advanced tools are needed
precise to be able to measure the proposal
initial measurement of waves
gravitational with light arrives in the
seventies dari vice was very two
young people at that time and the proposal yes
turned into the proposal for a true e
the observatory is an observatory
lay together with vice kit back laundry
they took her on this side
ocean
adalberto giazotto and bridle
they proposed the construction of a
analog detector detector virgo that
currently it is installed at the
european gravitational observatory a
farmhouse near Pisa
here I want to describe how they work
the gravitational wave detector
tool we use is called
mike elson interferometer is made of
a laser of some mirrors and a
object a photo detector that measures the
amount of light you win above
then the laser beam reaches one
mirror that separates the beam into two
components that travel along two
arms perpendicular to each other
they reach mirrors at the end of
these of these arms come back
they recombine and overlap
the arrival of a gravity wave
change as we have seen the distance
among the objects then change the
length of the arms and in consequence of
these length variations us
we see on the detector fact
an alternation of light and dark this
it is the sign is possible of
an interaction with
from gravitational these effects are
very small, however, the signal that
we have measured and been one
moving one of these mirrors of
10 at least 18 meters a number
very small to understand how much it is
small imagine we display a
meter imagine to divide it by
10,000 we get to the diameter of one
human hair we still share it for
one hundred we get to the size of one
bacterium still for 10,000
and we get to the size of a but a
this is not enough
you see we are ten at least 10
eight orders of magnitude are missing
we have to go on stairs again
small means entering inside
of the atom reach the dimensions of
a core but still not enough because the
vibrations we have measured are
one thousandth of the size of a
atomic core something really
hard to imagine
these tools were built and
currently there is a worldwide network of
interferometric detectors here you see
the virgo detector near pisa ce ne
they are two in the United States 1 in the state
of Washington Northwest 1 in Louisiana
south east the lake detectors are objects
very large with long arms and some
km 34 kilometers because the length
of the arms increases the effect of the wave
gravitational stretch 10 times
means to increase tenfold
the effect we want to measure i
laic and virgo detectors operate as one
unique observatory is a great one
collaboration consisting of more than
one thousand physical persons technical engineers and
students
everyone works together with passion with
dedication with the aim of improving
more and more these tools
here you see some pictures this is one
of the mirrors that have measured this
oscillation so small and they are gods
mirrors of about 40 centimeters of
very pure quartz diameter you see how
you work in extremely environments
clean for us
disturb the extreme in any way
optical quality of these objects that
they must obviously be isolated from
all suspended disorders with systems of
very sophisticated filters to prevent that
earthquake seismic disorders
they completely hide the very small one
vibration we want to measure systems
very complex opticians and this that
see here for example is the tube in the
which the laser beam travels this
tube represents the vacuum system
largest in Europe
there is emptiness in there because it is not
we can allow ourselves that propagation
of the acer is disturbed by impacts with
the molecules of the null area can be
left to chance
so these tools were
brought to levels of sophistication and of
truly remarkable precision and thanks to
this work carried out in the course of
decades on September 14th last
year
the two detectors of this network
international the two wide detectors
after starting from a few days
this run data recovery have measured
a signal from the universe
see here the detector output
the interferometer output from this
quite confusing trend has taken
instead at a certain point to follow one
well defined shape a sinusoid that
it grows in amplitude and grows in frequency
until you reach a maximum that you then
it is understood from the simulations
that this waveform was
produced by two black holes that orbit
one around the other in this
movement lasted or hundreds of millions
years
they approached each other more and more
putting gravitational waves lost
energy to their orbit has contracted
in getting closer they always bought
more speed you think than at the moment
of the merger
these two objects with a mass of
tens of times the mass of the sun is
they were moving at a speed equal to
half the speed of light and 150 thousand
kilometers per second
something really huge in this
moment at the time of the merger are
states has been generated a very large
surge of gravitational waves that like
see then it has propagated in the
space-time structure has traveled
in the universe and has reached the earth
this is a beautiful simulation
here in the calculation of the masses yes
can see that from the initial masses
up to the mass of the formed object
at the end there were 3 solar masses
missing these three solar masses are
converted to energy type energy
gravitational according to the famous one
equation is the same as written form
from the same einstein and in these few
very few tenths of a second that we
we have measured and been issued
an enormous amount of energy 50 times
the light energy emitted from all the
stars of the universe
the distance we said was
great over a billion years
light
and this is very important for the waves
gravitational and cross the universe
almost undisturbed and do not interact
with the matter the sun the planets are
practically transparent this does yes
that can come from far away
up to us and look far into the
space means looking back into the
time
we know a universe until now
by means of the radiation light
electromagnetic and cosmic radiation
background allowed us to take
an image of the universe after 300 thousand
years later the big bang is well we hope
that in the coming years thanks to
further improvement of these
instruments
it will be possible to measure a similar one
gravitational radiation that there
will unveil the mysteries of the universe
going back in time up to
very few moments after the big bang
initial the signal we have seen is
was the first of many systems exist
tracks formed as well as holes
blacks also from neutron stars too
singles that rotate like headlights
emit electromagnetic radiation e
gravitational radiation the stars to the
the end of their lives are exploded
supernovae and during this explosion
waves of gravitational waves are emitted
electromagnetic neutrinos are gods
incredible phenomena then
the observation of the universe that is
begun in 1600 with Galilean is
then continued through the study
of electromagnetic radiation in
visible in the radio waves in the
microwaves in ics rays in gamma rays
that is, buy the missing box
the observation of the universe by means
of electromagnetic radiation
in September last year
we started filling this
box will surely be the beginning is
a new window on the universe why
this type of radiation allows
know the characteristics of the
sources that are inaccessible to
any other type of messenger that
be of electro magnetic or neutrini e
so stay tuned because the
indeed, the past will reserve us
surely many other emotions
[Applause]
”
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