Buraco Negro | Nerdologia

Welcome to Nerdologia, I'm Atila - biologist and researcher, and I'll finally be answering all the comments asking for this episode. Today we're going to learn about black holes. From which not even Flash or Quicksilver would be able to run from.

To do this, we'll be using Neil DeGrasse Tyson's 'Death by Black Hole' as an authorized source material. Using this fantastic representation of XKCD, let's imagine the attraction which every celestial body is able to exert gravity is portrayed here like a well in space which objects fall into. One of the greatest and most influential scientists, Sir Isaac Newton, deduced within the universe's gravitational laws, that the force of attraction exerted by an object - gravity - depends directly on its mass and inversely on its distance.

So, on Earth, if we want to throw a stone at a speed where it would never return to the ground, ignoring friction with air, we would need an escape velocity of around 44,000 km/h. A stone thrown at this speed would never come back down - if the Flash or Quicksilver ran slightly faster than the speed calculated by Hitch Alan in the scene from 'Days of future past', they would have a sufficient speed to be able jump from a ramp and leave the Earth's orbit. Now observe the wells that Randall designed for Jupiter, this is because it has a much larger mass and therefore exerts a higher gravitational force/pull.

If you weigh 70kg here on Earth, you would way more than 165kg there. For the Flash to escape from Jupiter, he would need to run and jump almost 6 times faster than he would here on Earth. On the Sun, someone weighing 70kg on Earth would weigh almost 1900kg.

This is because the star is more than 330 thousand times more massive than Earth. So its force of gravity is much greater and its escape velocity is more than 600 km/s. all this gravity pulls the atoms of hydrogen together with great force, this causes fusion, creating the light and heat that we receive on Earth.

Bigger stars than the sun are able to form celestial bodies with a much larger gravitational pull, when they use up all their fuel they no longer produce the heat which keeps their atoms energized and apart from one another. Because of this, the outer layers explode resulting in one of the universe's craziest phenomena. The Supernova, the remaining nucleus shrinks under the force of gravity, until it reaches such a dense point that the atoms crumble, the electrons collapse into the protons and form neutrons.

Vsauce3 elaborated on the idea that Neil Tyson previously explained: if Thor's hammer was made from a piece of neutron star, (which it isn't), the hammer alone would generate a sufficient amount of gravity to attract anybody towards it at the speed of sound. Such a gravitational force exists here, that the escape velocity from a neutron star would be almost 1/3 of the speed of light. Black holes have this name, because they no longer have gravity, they are a point which is so dense that that the escape speed is actually greater than the speed of light So not even light can escape them.

What makes black holes so special is this concentrated gravitational force at one unique point. If an alien race wanted to transform the Sun into a black hole, since it is too small to do this on its own, they would need to crush it into a more concentrated form, to comply with the Schwarzschild radius. A radius of three kilometers would be enough to create a density within the Sun that was so large it would cause the necessary conditions for a black hole, but it wouldn't swallow the earth, since with the same mass, the sun would exert the same gravity on the distance on the distance we are away from it and our orbit would continue, the same as it was But it would be 'slightly' colder.

Now let's look at what would happen if you got close to it, the atoms of a star or nebula being swallowed by a black hole enter into orbit, and form a spiral. It is called an Accretion Disk, within it the rotations are so fast that it generates enough friction to heat the material to millions of degrees, and emits X rays and Gamma rays. In some extreme cases, this forms the most energetic object in the known universe - Quasars which emit more Gamma and light rays than entire galaxies, in most cases most of the black hole absorbed is thereby expelled.

If you want to know how this looked, check out at this great video from Vsauce. If you weren't ejected, you would be able to cross the event horizon, a point where even light itself cannot escape. To start, it distorts space and time so much that it acts as a lens that diverts light from behind it.

and since time is relative to gravity, minutes in the event horizon are equal to thousands of years outside of it. On Earth, because gravity gets weaker with distance, its affects your foot which is closer to its center than your head, this is equates to the weight of a drop of water on your foot this difference in acceleration by gravity between two points is called the Tidal Force. Now, passing through the event horizon of a black hole, things would be very different.

According to general relativity, in small holes the difference in gravity when crossing the event horizon is so large that if you fell in feet first, the tidal force would be strong enough to pull your feet with more force than that which holds your body together, therefore separating your body into two pieces, it would then separate each piece in two again, and again, and again until only molecules remained, broken into atoms and then broken even more, this process has the rather illustrative name of Spaghettification, it would be a cruel death, but at least with a lot of style and special effects. Don't forget to like and share the video, subscribe to the channel for more episodes asked for in the comments which I always delay in doing, and see you next Thursday. Another thank-you to our physicist, Caio Gomes.

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