Have you ever occasionally had the thought: What would happen if you fell into a black hole?

You might think you might be crushed, or torn into pieces. But reality may be weirder than you think. The moment you fall into a black hole, reality will be split in two. In one scenario, you're instantly reduced to ash, in the other, you're left mostly unscathed, and both scenarios are likely to be true.

What is a black hole?

Black holes are weird places where the laws of physics as we know them no longer apply. Einstein pointed out that the gravity of a black hole bends space-time, causing space-time itself to distort. Therefore, if there is an object with a high enough density, space-time will be severely distorted, so that a depression-like area will be formed in the real space-time around the object. This is a black hole. When a massive star expends its fuel and then explodes and collapses, this process will be enough to create such a strange, super-dense object. As the dead core of a supermassive star shrinks under its own mass, the space-time around it becomes distorted. Its gravity became so strong that light could not escape its grasp: a new black hole appeared where the star once stood.

The outermost layer of a black hole is its event boundary, which is the boundary of the gravitational range where light begins to be unable to escape. Beyond this area, light can escape, but once beyond this boundary, any efforts to escape are in vain. Event boundaries contain tremendous power. The quantum effect here produces a powerful stream of high-temperature particles that radiates outward, which is the so-called "Hawking radiation." This is named after the famous British astrophysicist Professor Hawking, because he was the first to predict the existence of this radiation effect. Given enough time, this Hawking radiation will eventually consume all of the black hole's mass and lead to the black hole's ultimate demise.

As you get deeper into the black hole, space-time becomes more distorted until you reach the core of the black hole - where the distortion of space-time reaches an infinite degree, which is the "singularity". Space and time will no longer make sense here, and all the laws of physics based on the concepts of time and space as we know them will be invalid.

Sina Technology Answer:

Have you ever had this thought occasionally: What would happen if you fell into a black hole?

You may think that you will probably be crushed or torn into pieces. But reality may be weirder than you think. The moment you fall into a black hole, reality will be split in two. In one scenario, you're instantly reduced to ash, in the other, you're left mostly unscathed, and both scenarios are likely to be true.

What is a black hole?

Black holes are weird places where the laws of physics as we know them no longer apply. Einstein pointed out that the gravity of a black hole bends space-time, causing space-time itself to distort. Therefore, if there is an object with a high enough density, space-time will be severely distorted, so that a depression-like area will be formed in the real space-time around the object. This is a black hole. When a massive star exhausts its fuel and then explodes and collapses, this process will be enough to create such a strange super-dense object. As the dead core of a supermassive star shrinks under its own mass, the space-time around it becomes distorted. Its gravity became so strong that light could not escape its grasp: a new black hole appeared where the star once stood.

The outermost layer of a black hole is its event boundary, which is the boundary of the gravitational range where light begins to be unable to escape. Beyond this area, light can escape, but once beyond this boundary, any efforts to escape will be in vain. Event boundaries contain tremendous power. The quantum effect here produces a powerful stream of high-temperature particles that radiates outward, which is the so-called "Hawking radiation." This is named after the famous British astrophysicist Professor Hawking, because he was the first to predict the existence of this radiation effect. Given enough time, this Hawking radiation will eventually consume all of the black hole's mass and lead to the black hole's ultimate demise.

As you get deeper into the black hole, space-time becomes more distorted until you reach the core of the black hole - where the distortion of space-time reaches an infinite degree, which is the "singularity". Space and time will no longer make sense here, and all the laws of physics based on the concepts of time and space as we know them will be invalid.

Massive celestial bodies will cause the distortion of space and time. Massive celestial bodies will cause the distortion of space and time.

In a black hole, the degree of distortion of space and time reaches the extreme. In a black hole, the degree of distortion of space and time reaches the extreme.

Black holes cause great distortion of the light propagation path, forming a "lens"-like effect. Black holes cause great distortion of the light propagation path, forming a "lens"-like effect.

Centaur Radio source A (Centaurus A) may be a large black hole located at the center of our galaxy. Centaurus A (Centaurus A) may be a large black hole located at the center of our galaxy

So what exactly will happen here? ? Another universe? chaos? Or to the back of your childhood bookshelf? No one knows the answer.

What happens when you fall into a black hole - you die, but at the same time you live

So what will happen if one day you are really unfortunate enough to fall into one of these black holes? What? First let's imagine that you have a companion named "Anne". You were falling into the black hole, and she was still observing the scene in horror from a safe distance. From now on, she will witness a series of strange phenomena.

As you continue to accelerate towards the black hole's event boundary. Anne will watch your body gradually become stretched and twisted, as if you were looking through a magnifying glass. And as you get closer and closer to the event boundary, Annie will notice that your movement speed seems to become slower and slower, as if you are watching a slow-motion lens.

You can't shout to her because there is no air in the space, but you think of using your iPhone to send a Morse code to Annie by flashing (there is really such an app). However, the speed of the signal you send out is also very slow. The wavelength of the light has been severely stretched in the strong gravitational field, and the frequency has become very low: "I am fine... I am fine... Me. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . She will see you still there, motionless, your stretched body beginning to be engulfed in flames.

In Annie's view, you have been reduced to ashes before you have even crossed the event boundary due to the stretching of space, the stasis of time and the high heat generated by Hawking radiation.

However, before we prepare for your funeral, let us forget about Anne's report and look at what you actually experienced during this period from your own perspective. Okay, now something even weirder happens: you feel like nothing is happening.

As you fall, you won't feel any stretching, slowing down, or terrible radiation. That's because you're in free fall, so you don't feel gravity - something Einstein called his "most delightful thought."

After all, the event boundary is not a brick wall, but an invisible boundary in space. An outside observer cannot witness events inside this boundary, but that is not a problem for you—to you, there is no boundary.

Of course, if you were falling into a smaller black hole, you would have big problems. You'll feel a strong pull of gravity: your legs will feel a much stronger pull than your head, and you'll be stretched like a piece of spaghetti. But luckily you're falling into a large black hole, millions of times more massive than the sun, so the gravitational difference that would tear you apart would be so small that it's almost negligible.

Theoretically, in a large enough black hole, you can live the rest of your life "normally" until you finally fall to the singularity in the center of the black hole and die.

“Normal” – How normal is it? You may have this question, because at this time you are falling into a gap in the space-time continuum, completely independent of your own will, and there is no way to turn back - there must be no one who can understand your feelings.

But the strange thing is that from a certain perspective, we can actually feel what you feel - not from space, but from time - the river of time moves forward forever The flow is not affected by our will. We can only move forward with time and there is no way to look back.

This is not just a metaphor. Black holes distort space and time to such an extreme degree that, inside the black hole, time and space have reversed roles. In a sense, it is time that pushes you to the final singularity. You can't go back and escape from a black hole, just like we can't go back to the past.

Quantum physics points out that there may be a "wall of fire" at the boundary of a black hole. Quantum physics points out that there may be a "wall of fire" at the boundary of a black hole.

The event boundary of a black hole is not A real wall The event boundary of a black hole is not a real wall

"Black hole information paradox"

At this point, you may be thinking: Wait a minute. What happened to that Annie? Obviously nothing happened to me, there was nothing around me, just empty space, so why did she insist that she saw me burned to ashes outside the boundary of the event? Was she hallucinating?

The fact is that Anne was not hallucinating. From her perspective, you were indeed burned to ashes near the event boundary. This is not an illusion. If possible, she may even collect your ashes and bring them back to earth for your family to bury.

In fact, the laws of nature require that from Anne's perspective, you must never be able to enter the interior of a black hole. This is because the principles of quantum physics require that information cannot be lost - any information describing your existence must remain outside the black hole, otherwise the laws of physics in Annie's space will break down.

On the other hand, the laws of physics also require that you must be able to cross the event boundary without encountering a flow of super-hot particles or anything else unusual. Otherwise you will violate Einstein's "most pleasant idea" and the principles of general relativity.

So, simply put, the laws of physics require you to exist in two states at the same time - a pile of ash outside the black hole, and an intact life inside the black hole. There is a third law of physics, however, which states that information is not allowed to be cloned—you must be in two places at the same time, but you can only have one at the same time.

Somehow, the laws of physics lead us to a conclusion that seems to defy common sense. Physicists call this contradictory conclusion the "Black Hole Information Paradox." Fortunately, in the 1990s, they finally found a way to reconcile this contradiction.

Physicist Leonard Susskind realized that this paradox doesn't actually exist because no one can see another you. Annie can only see you who have turned to ashes, and you can only see yourself alive. You and Annie can never compare the two "yous," and there is no way a third observer can see both the inside and the outside of the black hole. Therefore, in such a case, the laws of physics will not be broken.

Unless you insist on delving into it, which of these two you is the real you. You want to know: am I alive or dead?

An important fact revealed by the study of black holes is that there is no reality at all. Reality just depends on who you ask. In this story there is reality for Annie, and there is reality for you. That's probably it.

"Hawking Radiation" Spewing Out from the Event Boundary "Hawking Radiation" Spewing Out from the Event Boundary

Black hole - once you fall into it, you can never come out again Black holes - once you fall in, you can never come out again

"Spooky action at a distance"

In the summer of 2012, a team of physicists (including 4 Members: Ahmed Almheiri, Donald Marolf, Joe Polchinski and James Sully (AMPS for short) have designed a thought experiment that may completely subvert our understanding of black holes.

The AMPS team realized that Susskind's solution was based solely on the premise that the black hole's event boundary would reconcile the different facts you and Annie saw. You are floating safely in space, and Annie sees you turn into a ball of ashes. It doesn't matter, because Annie can't see you on the other side of the event boundary. But what if Anne had found a way to know what was going on on the other side of the event boundary without having to cross it herself?

Simply applying the theory of relativity, then this problem will not be established, but the principles of quantum physics make this problem more complicated than we imagined. Anne might be able to glimpse beyond the boundaries of events, using a phenomenon that Einstein called "spooky action-at-a-distance."

This is the effect of quantum entanglement - two particles, although separated in space, are strangely connected to each other ("entangled"). They belong to a single and indivisible whole, so the information describing it cannot be found in any one of their particles, but in the "entanglement" that connects them both like a ghost.

The thought experiment of the AMPS team is based on this - imagine that Anne has a set of information close to the event boundary, called A. If her story is correct and you have been reduced to ashes near the boundary of the black hole, then information A must be entangled with another set of information B, which should be related to the high-temperature particle flow.

On the other hand, if your story is correct, you are safely alive on the other side of the event boundary. Then information A must be entangled with another different information C, which should be related to something inside the black hole.

There is a contradiction here: each set of information can only be associated once. That is to say, information A can only be associated once between B and C - either with B or with C, but not both at the same time.

So Anne holds information A and puts it into her handheld entanglement interpretation machine. At this time, the machine will display the answer: either B or C, not Both are displayed simultaneously.

If the displayed answer is C, then your story wins, but the principles of quantum physics will break down. If information A and information C deep inside the black hole are entangled with each other, then for Annie, the information A she has will disappear forever, which violates the principle of quantum physics that information cannot be lost.

So what if the displayed result is B? If the interpretation machine showed that the answer was B, then Anne's story won, but Einstein's general theory of relativity would collapse. If information A and information B are entangled with each other, then Anne's story is the true version, which means that you have really been reduced to ashes, rather than passing through the event boundary unscathed, as the general theory of relativity requires - you encountered A real “wall of fire.”

This brings us back to where we started: What exactly happens when you fall into a black hole? Will you make it through the event boundary unscathed? Or will it hit a "wall of fire" during the fall and be reduced to ashes? No one knows the answer, and it has become one of the most enduring puzzles in fundamental physics.

In fact, physicists have spent more than 100 years trying to reconcile the contradictions between general relativity and quantum principles, knowing that eventually one of the two must give in. This paradox brought to us by black holes may help us judge which theory will make concessions, and guide us to find the deeper basic theory that governs the operation of the universe.

What does the inside of a black hole look like? No one knows the answer. What does the inside of a black hole look like? No one knows the answer

"Spooky action at a distance" - the effect of quantum entanglement - two particles, although separated in space, are eerily related to each other ("entangled") "Spooky "Action at a distance" - quantum entanglement effect - two particles are strangely connected to each other ("entangled") although they are separated in space.

Black holes can absorb matter from surrounding celestial bodies. Black holes can absorb matter from surrounding objects. Absorbing matter from celestial bodies

Back to the starting point

One of the clues may be in Annie's interpretation machine. It is extremely difficult and complicated to decipher another piece of information that is entangled with information A. So physicists Daniel Harlow of Princeton University in New Jersey and Patrick Hayden of Stanford University in California wanted to know how long such an interpretation would take.

In 2013, their calculations found that even with the most powerful computer allowed by the limits of physics principles, it would take an extremely long time for Anne to decipher the required information. By the time she finally deciphered the result, the black hole had already completely evaporated and disappeared from the universe.

If this result is correct, then the extreme complexity of the interpretation process itself would have thwarted Anne's efforts to figure out which of the two versions of the story was true. In this way, we can only assume that both stories are true, what reality is depends only on different observers, and all laws of physics will not be violated - you are dead and reduced to ashes, but at the same time safe Passed the event boundary without encountering the terrible "wall of fire" and lived safe and sound.

This result also inspired physicists to think about some new issues: that is, the connection between extremely complex calculations (such as what happened to Anne) and space and time. There seems to be some deeper secret hidden in it.

This is the story about black holes. They are not just about the fate of space travelers. They are also natural laboratories for theoretical physics, infinitely magnifying some extremely subtle flaws in the laws of physics to us. To the point where they simply cannot be ignored.

If the true nature of reality is still hidden somewhere, the best place to find them is in a black hole. Of course, before physicists can truly figure out the problem of black hole "firewalls" with confidence, it would be better for us to observe from the outside at the boundary of the event.

Or we can just send Annie in, it’s her turn this time