Imagine that since the day you were born you are unable to perceive the sound.
You have never heard the laughter of a child,
the song of a bird or a symphony.
In the same way you are forbidden the information of an alarm or my voice.
How different this talk would be.
From the first moment
in which humanity began to contemplate the universe
all the knowledge that we have from him
is through the observation of electromagnetic waves
of which visible light is only a small part.
What we see of the universe is only 2% through electromagnetic waves.
Only during the last two decades
we have begun to contemplate the remaining 98%
of the universe that we can not see.
On the one hand, with the detection of elementary particles
more elusive, the neutrinos.
And since September 14, 2015 with the detection of gravitational waves.
Let me tell you a story, the story of this first detection.
It’s a story that started a long time ago,
1300 million years.
Here on Earth the most evolved form of life were red algae.
Life has just discovered or invented sexual reproduction.
Far, far away, one of the events is about to happen
most energetic in the universe.
Two black holes, each 30 times the mass of our sun,
they are dancing the last 1/4 second of their last waltz,
rotating 100 times per second.
And just at the moment they merge,
that we are seeing now, in an embrace for eternity,
they are moving almost at the speed of light
Black holes moving almost at the speed of light.
This event is so energetic
that transforms the energy of 3 times the mass of our Sun
in an earthquake in the very structure of the universe.
This earthquake spreads in the form of gravitational waves
through the universe, imperturbable.
After 1300 million years reach a small blue planet,
on the outskirts of the secondary arms of a conventional spiral galaxy
illuminated by a common star in the middle of his life.
But this planet is special.
In him the universe has evolved to be conscious of itself,
even understand yourself.
And for the first time, feel yourself.
For the first time humanity has created an instrument that is capable
to feel the space-time.
Let’s listen to the unaltered symphony of the universe.
(Sounds)
These are the signs.
(Alternate sounds)
Do you hear that drop of water?
That is what we call “the song of the bird”.
That’s the signal we detect with our LIGO detectors.
And it is the first time that that signal comes from space-time.
For the first time we are sensitive to spacetime.
That signal, which lasts less than a fraction of a second,
It has constituted a complete revolution in science.
But maybe to understand a little better the depth of this signal,
of this detection, of this small fraction of a second,
that may seem conventional,
Let’s understand a bit about spacetime.
Space and time, by perceiving them independently,
our senses do not provide us with an objective reality.
The Theory of General Relativity says that space or the universe
it is not a space that evolves in time,
but it is a four-dimensional structure.
Without evolution.
Space and time are unified.
The points of this space-time, or of this four-dimensional structure,
we call them events, and we are the geometric line
that unites the event of our birth and death.
Mass, or matter, curves this space-time.
As you can see there, the greater the mass of the sun
makes the space-time curvature greater,
disturbs the distance between events.
The movement of objects, like ourselves, the Earth,
Through this curved space-time, it is what we call gravity.
But what are gravitational waves?
When matter moves, for example the star, the sun,
creates changes in this curvature.
They propagate in the form of waves at the speed of light.
Those waves distort spacetime,
and since gravity is the way we perceive
the distortion of space-time, are waves in gravity.
That’s why they are called gravitational waves.
But realize, it’s a wave, a wave that spreads
in the very structure of the universe.
The effect that the gravitational wave has on a fixed area of space
is that it narrows and shrinks it.
Imagine that a wave comes straight to me.
It would make me in a higher and thinner moment,
but the next shorter and wider.
Another way to see it is to imagine a ring of particles that move freely.
When the gravitational wave crosses it from the front
these particles will move in a combination of these possibilities.
To detect the gravitational wave
just measure the change, the distance between two of these particles
Then why is it so difficult? Why has it taken so long?
And why is the signal shown above so incredible?
Why is it so difficult to detect them?
Because these changes are minuscule, infinitesimal, despicable.
The reason? Spacetime is incredibly rigid.
You will say “I do not believe you”.
I’m going to try it.
For this I will use something that is advised not to do in a chat.
Show an equation
(Laughter)
The reason why I show you is that this equation
is the summary of the Theory of General Relativity.
This equation, as simple as it is on the outside, like a cathedral,
It hides immense complexity inside.
But this equation describes spacetime,
the very structure of the universe.
Something so simple.
In general, for you to believe that spacetime is very rigid,
the left T represents or informs the subject
how to move in a curved space-time.
The part on the right, that G -ignorad the rest-
G informs the subject of how to bend space-time.
The proportionality constant,
that part that is between the T and the G relates movement and matter
with the deformation of space-time.
That is what we call rigidity.
And as you can see there is a huge number,
It is a 5 followed by 42 zeros.
Now you believe that spacetime is very rigid.
That is why the most precise instruments that humanity has ever built,
which are the gravitational wave detectors,
they can only detect the generated gravitational waves
by the most violent cosmic phenomena.
Measure the impossible, as predicted by Einstein,
It has been a very long and very difficult road.
It began a century ago with the prediction of its existence by Einstein himself.
It took 40 years for the scientific community to believe
that existence was physical and that they could be measured.
In the 60s,
the experimental work of Joseph Weber and his resonant cylindrical bars
-that was the detector that used to detect gravitational waves-
It would be decisive to arouse the interest of the international scientific community.
In the late 60’s Joseph Weber announced the first detection.
Unfortunately, the lack of rigor of their scientific methods
and the lack of success in other similar detectors around the world
They discredit their results.
In the 70s and 80s
the theoretical basis of modern interferometric detectors settle.
In the 90’s, the LIGO consortium is created, which you may have heard.
Today this consortium brings together more than a thousand scientists,
among which I am,
in institutions around the world.
16 countries.
During this century this consortium has created, built and operated
two generations of interferometric detectors.
The 1st generation was not successful.
He did not get the detection,
but it was fundamental to develop the technology
that would be implemented in the second generation.
This September 14, 2015 we finally succeeded.
At last we were sensitive to spacetime.
LIGO detectors are interferometers.
They basically use the interference of light waves
to measure changes in the distance between mirrors.
These mirrors are going to be the two particles mentioned above.
We measure the distance between two free particles,
that’s all we need to measure the gravitational wave.
These are the protagonists of the talk, the LIGO detectors in the USA.
This is in Hanford.
And this one, in Louisiana, Livingston, both in the US
The technology has been developed by international scientific collaboration.
These interferometers are L-shaped, as you can see.
Each arm, each side of this L, is 4 km long.
You can see them from an airplane, when you take off or land there.
A fellow LIGO was taking pictures from the window of the plane
and the one who sat next to him said: “I see you interested in that building,
Do you know what they are?”
And my partner was going to respond, but he did not have time.
The one who sat next to him said: “I’m going to tell you.
They are time machines,
that the US Government is developing secretly.
That’s why he has this long platform. “
I imagine that he was thinking about “Back to the future”.
(Laughter)
To follow the game, my partner asked:
“What is the other detector bar for?”
And he says: “Aha! It’s so they can come.”
(Laughter)
Let’s see how an interferometer works in a simple way.
In this animation we see that the mirrors are at the end of those arms of 4 km.
At the intersection there is an optical instrument
which is called beam splitter,
that divides the beam coming from a laser light source
in two beams of equal intensity.
Each one moves through each of the arms,
reflects in the mirrors and returns to the point of intersection.
That light that we see at the end,
just in front of the photodiode that will measure the intensity of this light,
the intensity depends on the interference between these two initial rays.
This interference in turn depends on the change in length of the arms.
A gravitational wave detector works like a microphone:
transforms the physical effect of gravitational waves
in an electrical signal,
when the gravitational wave widens and shrinks each arm alternately.
That sign changed the length of these 4 km of each of the arms
in an amount a thousand times less than the size of a proton.
It is impossible to imagine, sometimes we think it is magic.
The technology of these instruments has been created particularly for them.
That’s why the most precise instrument that has ever existed.
To achieve these incredible levels of precision the mirrors have to move
less than the amount we want to measure.
Four types of fundamental noise limit this sensitivity.
The technology we develop is to minimize these noises.
First we talk about the seismic noise, everyone understands it.
Earthquakes, waves of the sea, human activity …
they move on the ground where the instruments sit.
This movement has to be reduced, so the mirrors are
in a 4-level pendulum structure.
The upper part of that structure, the pink part above,
It is subject to one of the most fixed elements that exist in the world.
In this way we minimize seismic noise by 10,000 million times.
Thermal noise is microscopic motion or vibration
of the atoms that make up the mirrors and the suspension structure.
To minimize it, we use very low mechanical dissipation materials.
Moreover, the yellow element is the last stage of these structures
and the one that holds the mirrors is monolithic, in one piece,
of the purest crystal that exists.
In this way we minimize the microscopic internal friction,
and for being a single piece, the friction between components.
The 40 kg mirrors are subject
by 4 glass fibers of 0.5 mm thickness each.
We also have quantum noise, which I will not enter at the moment,
and the gravitational gradient noise,
which is the change in the gravitational force acting on the mirrors,
due to the change in the density of the earth or air.
With these instruments we have detected for the first time,
observed directly, black holes.
Until now they were fictional,
we have only seen them indirectly.
We have observed the remains of structures or massive stars
that were probably formed just after the Big Bang.
Relics of the first generation of stars.
We have discovered that black holes can be paired
and that can collide.
This discovery is undoubtedly one of the most important achievements
of science in this century,
not only because it has validated a fundamental pillar of physics,
but because it has created a new way of observing the universe.
Providing information until now totally inaccessible
with the potential to discover objects, things that until now we did not imagine.
Every time we have seen the universe with a new form
It has revolutionized the world.
This is one of those new forms.
Going back to the analogy with the one I started.
Imagine now that you can begin to hear sounds around you.
The breathing of who sits next to you.
A smile, my voice.
A new reality opens up before you
and you have to make an effort again to understand it.
Let’s listen, let’s open our minds
for the new sounds that we are going to discover.
Thank you very much.
(Applause)
”
Be First to Comment