BURACOS NEGROS, como eles surgem?

Hey Paul, the new Nostalgia Science is on! Really? What is this schnozzle going to be talking about?

Black Holes! Oh, cool Lester. I love astrology!

It isn't called astrology, it's astronomy! Yeah whatever, I love it anyways. Let's watch it!

We're on planet Earth, which means it's obvious to say we are spinning around the Sun. Right, everybody knows that Now, what if I tell you that we are also spinning around a Black Hole? But no need to be scared!

Because we are not going to be swallowed by it This can't happen to Earth, but it can to Jupiter, Mars, Saturn to the Sun and all other stars we see at the night sky. Our whole galaxy is spinning around a Black Hole but in order to understand why this happens we need to stop to take a closer look at Black Holes, so we can try to understand also why they are so scary and I hope you liked Nostalgia Science about the Moon because we're going back to outer space. My name is Felipe Castanhari and welcome to Nostalgia Science.

Hello my dear friends, how are you? Man, it's cool you are enjoying Nostalgia Science truly, I am happy about it because it is the project I'm enjoy most doing here at Nostalgia Channel and it is always good to remember that it is such a hard work to do, that's why I ask you to leave a 'like' here on YouTube and share the video, and also subscribe to the Channel, to support this amazing project! We want to thank specially the guys from 'Trilha do ENEM' that really liked the ida of the project, so they are sponsoring this episode about Black Holes.

The website from 'Trilha do ENEM' is really nice take a look afterwards, because at their page you can study for simulated tests, focusing only in themes that you need to get better at. There are live video classes too. You can even call a friend to watch so you can both study together on their platform The website is really cool and helps a lot people who need to pass the exams (ENEM), and it's a lot o people.

So go check them out at www. trilhadoenem. com.

br because thanks to them, this and two more episodes of Nostalgia Science will be produced, so cool, they payed our bill, thank you! You are awesome! But let's go to our main theme now.

Guys, we are so attached to our reality on Earth that sometimes it's hard to imagine what happens in the Cosmos. We are still looking for our Planet's past's puzzle pieces and present's ones too. Imagine all the rest of the Universe.

If we are still discovering stuff here on Earth, there are still a lot of Stuff to be discovered in the Universe! Actually the Universe is a constant enigma that keeps defying Scientists and that is awesome! Science is not afraid to assume what it does not know and it shouldn't!

If you pretend to have all the answers, you 'close a door'. The investigation door, the research door, and the insatiable will to know the unknown. And one of the biggest enigmas that nourishes this thirst for knowledge are Black Holes.

They are always shown in movies, cartoons. sci fi series as something dangerous, threatening. .

. Everybody knows that if someday they go on an adventure through space a good advice could be: "Stay away from Black Holes! " It's not like you can easily go to space, but if you do, stay away!

But after all, what are Black Holes? Are the Monsters that wander through space devouring all they find on their way? Are they magic objects that paint the Universe black?

No, no, no, no. A Black Hole is nothing more than a ghost of a star. What makes a Black Hole so special, is that it has a gravitational field so strong that nothing can escape it's 'claws'.

Not even the light. And so we can better understand how it works, we need to know one of the biggest lies ever told by the history of science. The tale tells that someday on XVII century, a physicist called Isaac Newton resting underneath the shadow of a tree and saw an apple falling from that tree.

So he started to think why it had fallen, and so he elaborated the Law of Universal Gravitation. Ok, this story never happened, but this apple, Newton's apple even if it never existed, will help us understand one of the most important rules of the universe, the Gravitational Law. Always when two particles are near each other the gravitational force works it so one gets attracted to the other.

This law has two important characteristics. The bigger the mass of one of the objects, the stronger will be the attraction between them. At the same time, the closer these objects are from each other the more intensely will they attract to the other.

In the tale of Newton, the objects were an apple and our planet. Earth is attracting the apple and the apple is attracting Earth too with the same intensity. But how is it possible?

How does an apple attracts Earth the same way it attracts an apple, there is something wrong there, Castanhari! Well, Newton himself answered that riddle, he was one of the brightest minds that lived on Earth. He also created another law that you probably know called: "The Law of Reaction" For each action, there is an equal reaction in the opposite direction.

That is why the apple and Earth attract each other in the same intensity. The apple only loses the game by being pulled by our planet because it's has less mass. And the Gravitation Law works for every object in the Universe.

And when we speak on gravity, we think of satellites, planets. . .

But the Gravitational Law works for a planet and for an atom. It works even with a person. Yes, you have your own gravitational force.

You are not thrown into the outer space because you are attracted by the planet, at the same time the planet is attracted by you. The difference is that Earth's mass is much bigger than your mass. But now let's put Newton's Law in our pocket and go back to space to look at the Black Holes you are waiting for.

Now that we know how the Gravitational Law works it's easier to understand a Black Hole. Because it doesn't stay still in the Universe thinking: "Hmm. .

. I'm so lonely. .

. I'm gonna go swallow some people ". .

. no. The problem with the Black Hole is not loneliness.

. . it's just the contrary.

It is irresistible. And it's all fault of the Gravitational Law. We saw that the mass of something affects directly it's gravitational force.

Well, a Black Hole, is an astronomical object with a high mass concentration in a very small place. Because of that, it's gravitational attraction is absurdly strong Actually we can look at a Black Hole as if it was some kind of drain inside the Universe. Everything that gets close is literally swallowed inside this drain and one of the coolest things about science is that even if the human being couldn't get any close to a Black Hole before yet, we can still know it's existence and also know how is the outside of this drain.

Around the Black Hole, there is a part called 'Accretion disk' full of matter in the form of gas. It's as if it was an enormous cloud of gas. As this material moves, it heats up and liberates ultraviolet radiation, infrared or X-ray, that are other kinds of light that we can't perceive.

And thanks to X-rays that we could detect the first Black Holes. When we look directly to a Black Hole with the right equipment that can detect the x-ray, we can see besides light, we can see temperature. A star, for instance, cannot be detected by those equipments because it's surface is not hot enough.

It burns on around 100. 000ºC. Now, the disk of gas that is being swallowed up by the Black Hole this one is hotter.

It burns intensely on more than 100. 000. 000ºC.

So it is detected by the X-ray and so we know that there is a Black Hole. But let's go back to the drain. Inside the Accretion disk, there is another area called Ergosphere.

That is where the matter that is about to disappear into the Hole is spinning. Always at the same direction. Exactly as the water does around a drain.

The last exit of the Black Hole is the Event Horizon. That is the border between what we can observe and what we can't. Any material from the Ergosphere that passes by the Event Horizon cannot escape the gravity and will be swallowed to the Black Hole and never be seen again.

Some Black Holes show pulses of X-ray that are sent through gas that seem to escape them. But that is just an impression. Scientists believe that these pulses that come from the material of the Accretion disk gained speed to escape gravity before getting too close to the Black Hole.

But the biggest mystery involving the Black Whole is exactly what happens when someone or something ends up in it. The sad part is that until today scientists cannot explain what happens, and they couldn't since not any light or matter cannot escape a Black Hole, how can we se anything? But there are many theories about it and many of them are connected to the way Black Holes appear in the Universe.

When you look at the night sky full of stars shining, you actually are looking to the past. Stars are so far away that their light takes a long while to arrive here on Earth. So the light of these stars that we see maybe some of them aren't even there anymore.

Yes, stars are born and die all the time in the Universe. But don't be sad because this is not necessarily something bad. The death of a star is something linked directly to the birth of a Black Hole.

A star needs to burn out all it's 'fuel' to shine. When the 'fuel' of a very massive star is out it collapses because it can't contain it's own gravitational pressure, so this balance is broken. Ok, but what about our Sun?

Where does it fit in all this? Is it ever going to become a Black Hole? In around 7 billion years, our Sun will consume all its 'fuel' in the nucleus.

Where the temperature is so hot, that there is nuclear fusion, the nucleus of the atoms touch each other. Nuclear fusion, force, explosion. So this 'fuel' will burn out and it will undergo an enormous pressure and will expand, obviously devastating our planet with it.

Until finally it will implode so it can become a beautiful small white star. With all it's original mass concentrated in a space the size of the Earth. But our Sun will not became a Black Hole.

This happens only with stars that are 10x smaller than our Sun. That is when the nucleus of those stars implode, contract so absurdly, giving birth to a Black Hole. Remember what I said that we couldn't see what was inside a Black Hole?

Well, the scientists are sure about one thing: There is a singularity inside it. The Black Hole is as if it was a dark star, and it's that that causes the big gravitational field of the Black Hole. Because it has so much mass in such a small space that it's density is mathematically infinite.

And that is what makes the inside of the Black Hole so mysterious. Well, let's pretend that it is possible to see what happens inside the Black Hole. Now let's be cruel and throw an astronaut in the direction of this Black Hole.

This action would become automatically a horror movie you know why? Because the laws of physics seem to change inside a Black Hole. In the case of super massive Black Holes, if an astronaut is able to move fast enough to balance the gravitational attraction, he could orbit this Black Hole and last a little while before his tragic end.

In smaller Black Holes, like in the star ones, the gravitational force changes so fast as the object gets closer so there wouldn't be any time to get to the perimeter of the Black Hole. The gravitational attraction in his feet would be a million times stronger than on his head, and would stretch the poor astronaut. In astrophysics, this phenomenon is called Spaghettification, so, the poor astronaut would be tared to an atomic level.

And as he got closer to the Black Hole he wouldn't notice, but time would start to stop for him and that would be the effect of Time Dilation. That phenomenon seen in the theory of general relativity from Albert Einstein, and that would become more intense as the astronaut got closer to the Black Hole. That happens because the faster an object moves the slower time passes to it.

Orbiting a Black Hole, the object gets to a point of speed that resembles the speed of light. The only way for the astronaut to perceive that time 'froze', would be indirectly, because he would see everything that had fallen into the Black Hole before he came closer of the Event Horizon. And looking back he would see that he would fall.

The biggest question is: "Where is this astronaut going to land? ' Unfortunately, science still doesn't know the answer but there are some cool theories that we can explore. One of them says Black Holes are actually Wormholes, that are some kinds of spacial tunnels, and everything that falls inside them, lands in another point of the universe.

Besides that, some researchers also believe that our Universe also has White Holes, that were in the other ending of these tunnels, that means, on one side of the Wormhole we have a Black Hole where nothing comes out, and on the other side we have a White Hole, where nothing comes in. But some scientists like to think of the Black Hole as some proof we live in a Multiverse. That means, the multiverse is a theory that says there are many Universes coexisting with our Universe.

And all of these universes could be connected through Black Holes, that would work as some kind of portal, connecting those realities. We still don't have the definite answer for this. But everyday that goes by we get to understand a little bit more about the Black Holes.

In fact, scientists are trying to take the first picture of a Super Massive Black Hole called Sagittarius A* They are using eight radio telescopes around the world to get that picture. Ok, Castanhari, but where is that picture? Actually the processing of those images can take up to a year to be completed.

A few days ago, scientists discovered another Black Hole here in our cosmic 'backyard'. It is 100 thousand times the mass of our Sun and is kind of hidden in a gas cloud. This is the second biggest Black Hole of the Milky Way.

And if you're asking yourself which is the biggest Black Hole in our Galaxy, this takes us to what i said at the beginning of our video. When I said we are spinning around a Black Hole, this Black Hole is that Super Massive called Sagittarius A* that scientists are trying to take a picture of. The Black Hole Sagittarius A* has a mass 4 million times bigger than the Sun and it is right in the center of our Galaxy, Milky Way.

So our Solar System and all of the other solar systems are spinning around this Black Hole that is at the center of our Galaxy. Oh Castanhari. That's pretty unlucky.

Right in our Galaxy, so many Galaxies out there and ours has a Black Hole. . .

No, no, no, no, because scientists say that to each Galaxy in the Universe there is a Super Massive Black Hole inside it. And that is why science believes that Black Holes have a very important role on the formation of the Universe. We still haven't found out what that role is but I'm sure that one day this will happen.

And until that happens I repeat that advice at the beginning of the video. If someday you go to Space stay away from the Black Hole, ok? Tip from Castanhari.

So this was our Nostalgia Science about Black Holes. I hope you liked it. Don't forget to leave a 'like' here in case you liked, share the video, subscribe to the channel, so you can watch our last Nostalgia Science about the extinction of Dinosaurs, and as always.

. . Always be curious!

Thank you!