Did you know that black holes exist? they suck the light, they distort space and time
Some are small while others are the size of the solar system
Black holes have no hair
And they are not so black, they emit particles and evaporate
And that's what we'll see in today's video, what are black holes?
(Introduction)
Singularity - Helping the dissemination of science in Brazil ''
And cosmologists all right? here who speaks is the Vini of the channel singularity
This is another video from our mini-course on astronomy
today we will talk about a subject that looks like science fiction, what are the black holes
this idea of black holes begins in the years 1915
What is the year that the famous physicist Albert Einstein published his most famous work
What is the theory of general relativity?
This theory, which has already been proven
says that mass distorts space, gravity is a property of the fabric of space
She said that space and time are inseparable
they are interconnected a fabric called space-time
so if we distort space, we also distort time
This theory of Einstein
is the basis of modern astrophysics, it explains very well orbits, gravitational lenses, stars etc.
The idea of black holes appears in the part of how the stars work
gravity is a force that always compresses matter
she wants to leave more matter in an increasingly smaller space
the stars for example, suffer this gravity, but they use the energy of the thermonuclear reactions not to contract
that is not to decrease in size
Our Sun star only does not decrease in size due to thermonuclear fusions
our star the sun is relatively small it is a yellow dwarf star that is lightly dense
if we take a star that is denser like a white dwarf
what prevents it from decreasing in size is the exclusion principle of Pauli
that is, the electromagnetic repulsion of electrons
the electrons are in the outer part of the atom, that is, all matter has electrons
these electrons are negatively charged, this causes them to repel themselves and not get too close
stars denser than white dwarfs such as neutron stars
crush the electrons, they are extremely massive stars
which only decreases in size because of the strength of protons and neutrons
which is the strong nuclear force
Well, as you can see the stars are stable due to a force that prevents gravity
but for example if a star had too much mass
so much mass, that not even a force could prevent the star from compressing
what size and what density would that star achieve?
the physicists who had this idea realized that the equations derived from general relativity
predicted that if a star had so much mass it could tear the tissue out of space
This gravity would be so intense that matter would be compressed to a size zero
It would have an infinite density thus generating a singularity in the fabric of time space
a singularity is a singular thing, that is, there is nothing like it
this singularity generates a black hole
that is, black holes generate from very massive stars that collapsed
These stars tear the fabric of space
And they create singularities that would be like holes in space
this distortion of space is so sharp that not even the light traveling 300,000 kilometers per second
can escape this distortion, so the black holes are black
because even the light can not escape them
and already how space and time are interconnected if we twist the space we also distort the time
so next to a black hole time dilates until it basically stops
the center of a black hole is a singularity is a region so peculiar to space
that our laws of physics stop working
matter that falls into a singularity no one knows for sure where it goes
some physicists say it goes to another universe or another dimension
is a very fundamental question about black holes
What happens inside the singularity?
Unfortunately this paradox has not yet been resolved.
after singularity we have the event horizon which is a place that nothing can escape
once in the event horizon always there, the distortions of space and time make it physically impossible to get out of it
not even the light can escape, that is, no information can get out of there
the time for then is physically impossible to get out of there
we could also use this gravity to create a time machine
as the interstellar film shows very well
a few hours near the event horizon can mean years here on earth
Time, gravity on that planet will slow down our clock dramatically.
However, this scenario is not very realistic
because the closer we get to a black hole
the greater the variation of gravity, that is, the severity of your foot is greater than that of your head
This makes the spaghetti effect
you would basically die turning a spaghetti
After this kind of abyss
We have the accretion disk which is the concentration of matter that begins to fall into a black hole
a black hole creates a lot of gravity
so it is surrounded by matter
If a star orbits a black hole
Your matter is sucked by this accretion disk
When this region is very dense, that is, there is a lot of matter temperatures begin to rise
Because of this the gas begins to expand and begins to release gamma rays in huge jets of energy
These are the black holes of the Quasares type
they emit gamma rays because of the accretion disk
Quasars are much more abundant in ancient times of the universe
formerly the universe was smaller and denser
so the probability of a black hole turning into a quasar was much greater
it is estimated that at the beginning of the universe
there were basically 300 black holes every year cubic light
if we consider that the solar system is all the gravity of the sun
our solar system is one light year in diameter, that is, there used to be 300 black holes in that space
So they were much more abundant in former times things like billions of years
these are the black holes, there are several types such as Interstellar
which has tens of times the mass of the sun
This hole was very well represented in the interstellar film that calls interstellar because of it
there are other so-called supermassives that are extremely large
they are usually at the center of galaxies, for example our Milky Way galaxy
has a supermassive black hole Sagittarius A
That is gigantic
basically all galaxies have a supermassive black hole of this type in their center
because basically this black hole would attract all matter
these are the main types of black holes
the quasars, supermassive, interstellar at last
one very strange thing that astronomers have realized is that black holes are perfectly spherical
how can they be perfectly spherical being that the stars that originated them were flattened?
this was called the baldness paradox
the astronomers after a time solved the paradox and realized that the black holes had no hair
that is, they did not have tufts
they were not very different from each other
the black holes were very similar
They only had some differences between size, mass and rotation
that is, there is a high probability that one black hole is exactly the same as another
they have no hair differences, black holes would be like fundamental particles
which only has some different characteristics
such as mass, rotation and electromagnetic charge
one of the most famous theoretical physicists on the subject black holes
It's Stephen Hawking who is currently 76 years old.
and realized that the black holes are not so black so they emit radiation
there is a physical law called the second law of thermodynamics
she says that entropy always tends to increase
that is, if matter fell into a black hole
the entropy of a black hole should increase
grossly entropy is disorder in a system
the heat is roughly entropy
So if the matter falls into a black hole
and increases its entropy, so its temperature should increase
A black hole should then have a temperature and give off heat
the black holes are extremely cold, they approach very much from absolute zero
however, they emit a small radiation called Hawking radiation
What is a very strange thing, like a black hole sucking all matter could emit something?
the answer is a bit complicated
This radiation comes from the event horizon of a black hole
near this place happen quantum vacuum effects
virtual particles, positive and negative, annihilate generating pure energy
Simply put
a particle of this pair could fall on the event horizon
then to an external observer it would appear that the particle is being emitted
this radiation decreases the area of a black hole
And the smaller the event horizon the higher the radiation rate
That is, the black holes as time goes decreasing in size
however this effect is minimal a black hole that was created now
it would take billions of billions of billions of billions and many billions
to be able to finally reduce its size to zero
that is, black holes can evaporate
but it takes a lot of time
some physicists think that when evaporation occurs, the information that was in the singularity
finally leaves the black hole, that is, the information is conserved
others like Stephen Hawking himself say that it disappears along with the black hole
This is an extremely interesting topic.
however he has some additions and caveats
the first is that astronomers have never taken a definitive picture of a black hole
they have always detected black holes by indirect observations
that is, stars orbiting places that there was nothing
Matter being sucked into a place that has nothing, that kind of observation
Hawking radiation to date has not been detected
because theoretically it is much more very low
the measurement equipment must be very accurate in order to measure this radiation
but even if there are no direct observations
the theory they are based on is one of the most well-proven theories of science
which has already been proven by gravitational waves, for example, the michelson-morley experiment at last.
So this is it, if you liked let your liked it
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and it is because of this that the singularity calls singularity
it's because of that black hole region, so that's it personal until the next video and spoke!
Subtitles: Vinícius Dutra
All: Vinícius Dutra
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