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In the vast history, looking up at the stars is definitely the most romantic thing that humans have ever done.
The stars are twinkling all over the sky, the waxing and waning of the moon, and the changing seasons of the star map. In ancient times when technology was not very developed, they were all guidance from gods to humans.
In ancient Babylon, there was the god Anu, the Mayans had special observers of Venus, and the Qintian Supervisor of China was in charge of observing and timing, and had to guide the present and predict the future based on the starry sky. .
Various celestial bodies in Chinese history
Later, Copernicus and Galileo in the West overturned the geocentric theory. Through high-power telescopes, everyone discovered that the things that blingbling at night are actually the same thing as the planets we step on.
Of course, we now know that the changes in the starry sky have nothing to do with us on earth. However, the ancients' obsession with the starry sky is still engraved in our bones from generation to generation.
It was also due to the efforts of Galileo and others that people began to break through the shackles of religion on thought and eagerly explored all the natural sciences around them and in deep space. .
Newton proposed the law of universal gravitation . Two objects with mass attract each other. The greater the mass, the greater the attraction.
Although it is fake that Newton was smashed, it does not stop everyone from taking the apple tree as a symbol of pursuing science.
The reason why the moon revolves around the earth is that the centrifugal force of the moon and the attraction of the earth to it cancel each other out, causing the moon to only stay in orbit. Turn and turn, you can't run away or rush over~
At the same time, Newton also believed that light is a kind of particle, photons have mass, which directly subverts everyone's cognition (in fact, light has particle characteristics and volatility , photons do not have rest mass , but have dynamic mass. Newton was only half right). .
One hundred years later, in 1783, John Michell, a British natural philosopher, wrote in a letter to Henry Cavendish (the awesome scientist who discovered Coulomb's law and Ohm's law), "Is there such a situation where a diameter of 500 A celestial body whose density is not smaller than the sun will not allow any light to leave it due to its gravity; or a celestial body with a large mass but a small volume, we will not be able to see this celestial body. However, we can pass through other celestial bodies. The luminous body revolving around it determines the existence of this celestial body. "
His idea is very simple. Photons have mass (in the moving reference system), and celestial bodies also have mass. So if the mass of the celestial body is large enough, Then even light cannot escape the attraction of this celestial body . .
Any light near it will be attracted and unable to escape, so from our perspective, wouldn’t it be completely dark?
This is almost the oldest theory about black holes recorded by mankind. .
But at that time, people rarely thought of such advanced things, and this discovery was almost completely buried. It was not discovered again until decades ago by people who compiled historical materials. .
The miserable John Michell has been ignored by everyone. .
Although John Michell's little guess is unknown, the wheel of time is still rolling, and people's pursuit of science is still crazy.
At the beginning of the 20th century, Einstein successively published the special theory of relativity and general theory of relativity that shocked the world. .
Through these two theories, people can calculate that objects with non-zero static mass can never reach the speed of light (special theory of relativity), gravitational field will cause the curvature of space and time (general relativity).
The general theory of relativity has a corresponding "Einstein field equation". This formula means that the cause of gravity is caused by the curvature of space and time produced by matter and energy. .
At this time, I have to mention a concept - Schwarzschild radius .
For a spherically symmetric, non-rotating, uncharged object, if it is compressed to within the value of the Schwarzschild radius, there will be no known type of force that can prevent the material's own gravity from compressing itself into a singularity .
translated into human language is that when the radius of a sphere is smaller than its own Schwarzschild radius, then it will be compressed into a point and become a black hole. It is estimated that the Schwarzschild radius of the earth is 9 mm. . .
At the end of its life, because the energy emitted outwards becomes less and it cannot support the action of gravity, it will collapse inward. Once it accidentally collapses to within the Schwarzschild radius, a black hole will be produced. .
Several endings of stars
Then another concept emerged - " event horizon ".
Because light cannot escape a black hole, things inside a black hole can never be observed by us outside the black hole. .
The boundary that defines the inside and outside of a black hole is the "event horizon."
For a long time, everyone has known that the black hole is there, but no one knows how to let everyone observe what it looks like.
In order to allow everyone to truly "see" black holes, humans have established the "Event Horizon Telescope (EHT, Event Horizon Telescope)" organization, which is specifically used to observe supermassive black holes in the centers of galaxies.
Later, people discovered that although light cannot escape the black hole, the black hole will release a large amount of radiation when absorbing the surrounding material. .
If a black hole is observed in the X-ray band, the black hole will be blindingly bright. .
Sagittarius A*
observed in the X-ray band. Therefore, EHT gathered a group of the world's most powerful submillimeter wave observatories to form a super luxury lineup on Earth, specifically to take photos of M87 in the constellation Virgo. .
8 powerful places join forces
Just now, mankind’s first animated black hole photo was released!
In fact, the original photo data collection was completed more than two years ago. However, due to the complexity of the data, many problems were encountered for the first time, so it has been delayed until now. .
Seeing this warm orange light, well, everything is worth it.
you ask me what is the use of this thing?
seems to be of no use. . .
However, this represents a higher level of human science and technology in some aspects, and we don’t know what this will bring.
Just like when people discovered electricity, they never thought that mankind would have such a great electrical age.
Picture sources: negative reviews, Xinhuanet, Weibo @老庄的故事, Quantum School, China Popular Science Expo References: Wikipedia, black holes, John Michell, Schwarzschild Radius Quantum School, "Stop making trouble, one The black hole cannot be clearly seen in the photo" Zhihu, "Can we leave the black hole using low-speed spaceflight? 》
“ Within light cone is destiny ”
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