What is a black hole, the 'most extreme being in the universe'?


NASA Hubble Space Telescope

Black holes , which are ultra-dense celestial bodies, are a type of celestial body, but due to the extremely strong gravity, even light cannot escape, making direct observation difficult. Kurzgesagt, a scientific YouTube channel, explains the black hole, which is the 'most extreme existence in the universe,' in a characteristic animation movie.

The Most Extreme Things in the Universe --Ultimate Guide to Black Holes --YouTube

Black holes are the most powerful and extreme in the universe, yet strange and complex.

According to Kurzgesagt, before thinking about black holes, we first need to sort out space and time. The universe exists in space and time, but space and time are not like fixed stages.

Space and time are relative to each other ...

The mass of an object can distort the space, and the distortion of the space can influence the movement of the object.

If the celestial body is in space, the space will be distorted and gravity will be generated.

Black holes aren't distorted, they're like pitfalls.

A black hole is the end of a giant star. When a star cannot withstand its own gravity, it

collapses , and the core compressed at a rate of one-fourth the speed of light becomes a neutron star or a black hole.

Black holes with very large mass and high density compression distort space-time significantly.

Even a black hole, which has 10 times the mass of the sun, is only about 60km in diameter.

A very strong gravitational field is formed inside a certain radius of the black hole, and even light cannot escape. This radius is called the Schwarzschild radius, and the sphere with the

Schwarzschild radius is called the event horizon .

Since even light cannot be emitted from the event horizon, it is black and nothing can be seen from the outside.

However, even if the black hole itself cannot be observed, it is possible to indirectly observe the black hole by observing the celestial body affected by the black hole.

In addition, many black holes have a disk of material called an

accretion disk.

The material contained in the accretion disk of a black hole can accelerate to about half the speed of light, and can reach temperatures as high as 1 billion degrees due to slight friction and collisions between particles.

So while the event horizon is pitch black, the black hole accretion disk seems to be incredibly bright.

When approaching just outside the event horizon, the light returns around the black hole and you can see 'your own figure' right there. This is because gravity causes light to orbit around the black hole.

Gravity distorts not only light but also time. Because the flow of time slows down under strong gravity ...

The surrounding landscape appears to accelerate as you approach the event horizon.

On the other hand, when you look at an object approaching the event horizon from a distance, it seems as if it is moving in slow motion.

It is possible to go to the future by taking advantage of the difference in time flowing near the black hole and elsewhere, but approaching the black hole is extremely dangerous.

If the black hole is small, the gravity on the human head and feet on the event horizon will be imbalanced, resulting in a

spaghetti phenomenon in which the black hole is stretched vertically like noodles.

When attacked by the spaghetti phenomenon, it will eventually become a hot plasma flow.

The spaghetti phenomenon occurs when the black hole is small, and it is thought that a large black hole can pass through the event horizon without being stretched.

When observing a human entering the event horizon from the outside, it looks as if the human has stopped. This is because the force of gravity slows the flow of time.

On the other hand, from the human side entering the event horizon, the surroundings are surrounded by darkness, and the outside can be seen only from a small spot.

Space-time is distorted inside the event horizon, and no matter where you go, you will be drawn to the center of the black hole.

The singularity in the center of the black hole is where the gravitational field is infinite, and everything is compressed infinitely small.

Since a substance compressed to a singularity loses all its properties, there are only three properties that can exist in a black hole: mass, angular momentum, and electric charge.

The difference that exists in each black hole is like the difference

in elementary particles.

Because the singularity where the curvature and density of space and time become infinite cannot be handled by calculation ...

The existing laws of physics, including the

general theory of relativity, no longer hold.

Thinking about what the singularity is is a very difficult problem.

In addition, there are many cases where black holes are rotating because they were born from dead stars, and there are also black holes that are rotating at 90% of the speed of light.

When the black hole is rotating at high speed, it forms a

ring-shaped singularity where the singularity is shaped like a ring.

There is an area called the ergosphere outside the rotating black hole, and it seems that the object is being dragged at a speed higher than the speed of light.

There is a theory based on

Hawking radiation that Dr. Stephen Hawking advocated existence as to what will happen to black holes in the end.

From a quantum mechanical point of view,

pair production of particles and antiparticles occurs near the event horizon of a black hole.

Normally, particles generated by pair production and antiparticles collide immediately and

annihilate .

Dr. Hawking thought that if pair production occurred near the event horizon, one would fall to a singularity and the other would escape to the outside. The particles that escape to the outside are Hawking radiation.

Since the mass of the particles emitted by Hawking radiation is derived from the black hole, it is thought that the black hole eventually emits the mass and disappears.

However, black holes have such a large mass that it is expected that it will take an enormous amount of time to release and extinguish all the mass.

Understanding black holes is very difficult even with modern science, but ...

That's why Kurzgesagt summarizes that there are many unsolved mysteries and it's fun to explore.

in Science,   Video, Posted by log1h_ik