Black holes, arguably the weirdest celestial bodies in the universe, are capable of devouring anything that comes close. But does a black hole really devour objects? How does it actually devour objects?
According to Newton's system of mechanics, the process of a black hole devouring an object is actually the strong gravitational pull of the black hole at work. From this point of view, black holes devouring objects are the same as each of us being "swallowed" by the earth, and each of us is firmly bound to the earth's surface by the earth's gravity.
However, Einstein's general theory of relativity shows that the so-called gravitational force is actually a superficial appearance, and its essence is the curvature of space-time. In other words, gravity does not exist, and gravity is just an external manifestation of the curvature of space-time.
So how exactly does space-time bend?
Imagine a two-dimensional plane, say an elastic membrane with many glass balls rolling back and forth on the membrane. At this time, if an iron ball with a larger mass is placed on the film, the iron ball will press the film out of an obvious depression, and the glass ball on the film will naturally move towards the center of the depression when it feels the existence of the depression.
In fact, this process is the manifestation of gravity, and it can be seen that gravity is only a description of plane bending (space-time bending), and is not a force in itself. Of course, this is only an interpretation of general relativity, and there are other interpretations of the Standard Model of particles, which will not be detailed here.
Some people will disagree with the statement that the curvature of space-time causes gravity: it is not "the curvature of space-time that causes gravity", but precisely "gravity that causes the curvature of space-time", because the reason why the iron ball causes the film to sink is precisely caused by gravity.
This, of course, is contrary to the general theory of relativity's interpretation of gravity. In fact, the schematic description of "space-time bending" on the Internet is not rigorous. Most schematic diagrams describe the bending of space-time as a "downward bend", which makes it easy to give the illusion that why is it bent downward? Isn't it because of gravity?
In fact, space-time bending is not a "downward bending", and the schematic description of space-time bending on the Internet is just convenient for us to understand "what is bending" more popularly, but many times popular often means that it is not rigorous.
In fact, since there is no concept of "up and down" in space, space-time will certainly not "bend downward". So, how exactly does space-time bend?
The answer is: bending towards the center of mass of the object. Any object with mass affects the surrounding space-time, and the object's motion also pulls the surrounding space-time to move with it.
And a black hole is also an object, an object with a supermassive mass. The mass of the black hole is so large that the density can theoretically reach infinity, so it can cause space-time to bend infinitely, and the surrounding space-time points to a point, which is the singularity of the black hole.
Our space-time structure is very hard, but because black holes can infinitely stretch the space-time structure, even space-time itself cannot withstand the infinitely dense black holes, and eventually it is completely torn through, just like a needle piercing a hole in the space-time structure, the black hole singularity can tear apart the space-time structure and "make a hole" in the space-time structure, where will this hole eventually lead?
We don't know, it could be other universes, or it could be higher-dimensional space-time, such as five-dimensional space-time. The famous science fiction movie "Interstellar" has such a storyline description, the male protagonist travels through a black hole and finally reaches the five-dimensional space-time, where he can interact with the four-dimensional space-time we are in through gravity.
In fact, this kind of storyline is not pure science fiction, and there is a certain scientific truth. If you are careful, you must have noticed that although gravity is everywhere around us, gravity is actually very weak, and it is the weakest of the four basic forces in nature. How weak is gravity?
Just give an example to make it clear. We can easily lift a baby, and you may not know that you are "lifting the baby" to fight against the gravitational pull of the whole earth on the baby!
Why is gravity so weak?
Scientists speculate that it is likely that most of the gravitational pull leaks into high-dimensional space-time, which is why the hero of the movie is able to interact with our four-dimensional world through gravity.
Theoretically, as long as the speed is fast enough, it can escape the strong gravitational pull of a black hole. However, due to the speed limit of the four-dimensional space-time we are in, that is, the speed of light, when we get close to the black hole to a certain extent, even if we fly at the speed of light, we cannot escape, and we can only be swallowed by the black hole in the end, and there is no return.
The critical point that is swallowed by the black hole is the event horizon, which is a sphere centered on the singularity and radiated by the Schwarzschild radius. The event horizon can be understood in this way, and this boundary happens to be the critical value of traveling at the speed of light without being swallowed by a black hole. Once the event horizon is crossed, it is theoretically possible to escape from a black hole only by traveling faster than light, but faster than light is not allowed.
In fact, since the nature of gravity is the curvature of space-time, the bending of space-time by any object is equivalent to creating a "gravitational well" in space-time, some deep and some shallow, which is related to the mass of the object.
Just as we are on the earth, we actually live in the "gravitational well" formed by the earth's curved space-time, and if we want to escape the earth's gravitational pull, we need to escape the "gravitational well" created by the earth.
The "gravitational well" created by the black hole in the space-time structure can reach infinite depth, so any object swallowed by the black hole can only keep falling, and there is no turning back.
So, where do objects that fall into the "gravitational well" end up?
As I just said, due to the infinite density of black holes, they can completely tear apart space-time, "make a hole" in the space-time structure, and lead to another world, other universes or high-dimensional space-time.
If the objects swallowed by the black hole really end up in another high-dimensional space-time, does it mean that the universe in which we live will no longer be a closed system, and even the "conservation of mass and energy" that we firmly believe in will no longer be inevitable?
Black holes affect space-time, just like a basin bursting a hole, and the water in the basin is constantly flowing out, of course, the total amount of water cannot be conserved.
Due to the speed of light in our universe, it is impossible to escape from the infinitely deep "gravitational well" at the speed of light after light is swallowed by a black hole. Even if the light can escape the black hole, it will theoretically take an infinite time, and the "infinite time" is meaningless to us in the real world, and in our eyes, it is equivalent to the light being completely swallowed.
The above analysis of black holes and black holes engulfing objects is based on the analysis of "black holes in the two-dimensional world". In fact, in our three-dimensional world, a black hole is also a celestial body, a "black sphere" that we cannot see. Black holes are usually very far away from the Earth, which means that the black holes we see today are actually black holes from thousands of years ago.
The objects that are swallowed by the black hole may reach another dimension from our four-dimensional space-time, such as high-dimensional space-time. This means that our universe is actually losing energy and matter all the time, and black holes are like "holes" in four-dimensional space-time, and objects close to it will fall into it and reach another space-time dimension.
Eventually, when all the energy and matter were lost, the stars were completely extinguished, and the entire universe was completely silent, leaving only a black hole full of holes.
Because the density of the black hole is large enough, the process of constantly devouring objects will make the mass of the black hole continue to increase, and finally the universe can no longer bear it, it will collapse, all the black hole singularities will collide together, and the objects swallowed by the black hole will be sprayed into another dimension at once.
Perhaps, in another dimension, intelligent life will detect this spectacle, and an infinitesimal singularity will suddenly begin to expand, while ejecting nearly infinite matter, thus forming the universe in which they live. This is also what they call the "Big Bang".
And such stories are not uncommon, not just played out once, but countless times, countless parallel universes are constantly circulating back and forth between rebirth and death in this way, transferring energy and matter to each other in the process of circulation.
summary
Part of the above description of black holes and the objects that are engulfed by black holes is my own brainstorm, because no one knows exactly where the objects that are swallowed by black holes go, so we can only guess.
General relativity has long predicted the existence of strange objects such as black holes, and in 2019, astronomers finally took the first photo of a black hole in human history, confirming the existence of black holes.
Of course, since black holes are usually very far away from the Earth, it is unrealistic for humans to "detect" black holes up close. Even if a black hole is indeed discovered near the earth, it is difficult to detect more black hole mysteries with current human technology.
The reason is simple, we can't send a probe to get the information inside the black hole, because even the information will be swallowed by the black hole. We must use more advanced technology to obtain the internal information of black holes, which means that the black hole itself must contain deeper mysteries, and we must use higher laws of physics to unravel the mystery of black holes.
Finish!