Chapter 308 The most extreme romance of human wisdom: Time and space are bent because of you!
Through rational thinking and in-depth analysis, Li Qiwei boldly hypothesized two basic principles.
First, the inertial force field and the gravitational field are locally equivalent.
Second, all physical laws have the same form in any reference frame.
Based on these two principles, it can be concluded that non-inertial frame = inertial frame + gravitational field.
Therefore, problems in non-inertial systems that are helpless in the face of special relativity can be decomposed into problems in inertial systems.
The inertial system is very simple, and Newton's laws have been studied perfectly.
All that remains is to concentrate on the study of gravity.
Start a thought experiment.
As we said before, suppose there is a spacecraft accelerating with acceleration g.
If there is a person K holding a basketball in his hand, then if he releases his hand, the basketball will fall to the ground of the spacecraft like a free fall.
And the trajectory, speed, etc. are exactly the same as on the earth.
Because the spaceship at this time feels like the earth.
He couldn't tell whether the basketball was affected by gravity or the inertial force given by the spacecraft.
Okay, here comes the point!
Now let's take our thoughts a step closer.
What if K is holding a flashlight instead of a basketball?
Now the spacecraft continues to move upward with acceleration g.
At this time, K turned on the flashlight in the horizontal direction, and the light was instantly generated and moved in the horizontal direction toward the wall directly opposite K.
So, imagine what would happen to people standing on the earth at this moment?
Very simple.
The spacecraft is undergoing uniform acceleration motion with an acceleration of g, and the speed of light is constant.
So the distance traveled by light is different in the horizontal direction and the vertical direction.
Thus, people on Earth would see the light moving in the opposite direction of the spacecraft's acceleration.
It looks like the light is "hanging" downward.
That is, the light becomes curved instead of straight and horizontal.
Looks like a parabola.
You can imagine this scene in your mind.
Suppose that in a Cartesian coordinate system, a small ball is thrown at the origin.
If the distance traveled by the Y-axis is greater than the X-axis per unit time.
Then does it become a parabola when connected?
This is what happens to light in an accelerating spacecraft.
This is incredible.
You must know that the inertial force field and the gravitational field are equivalent.
The spaceship at this time is actually equivalent to the earth.
So similarly, light is curved in the spacecraft, which means that light is also curved on the earth.
It is all due to the effect of acceleration g, which causes light to no longer travel in a straight line, but to propagate in a curve.
This step is very critical, think about it carefully and try to understand it.
Why don’t we usually see light bending on the earth?
Because the Earth's mass is so small, it bends light very little.
Now, we have reached our first surprising but logical conclusion: gravity bends light.
If the average person had reasoned this far, they would probably be overjoyed.
Wow, that’s awesome.
Light actually bends.
What a significant achievement this is.
But Einstein in real history was not satisfied with this conclusion and continued to think deeply.
What does it mean that gravity bends light?
At this time, he suddenly thought of the Leaning Tower of Pisa experiment.
Of course it is not the same as the real experiment, he went a step further.
Einstein was thinking about two completely different objects, such as a basketball and a chicken.
If they are placed in a vacuum, then under the action of gravity, their falling speeds and trajectories will be exactly the same.
This has nothing to do with the physical and chemical properties of basketballs and chickens.
If we boldly assume that the basketball and the chicken reach the speed of light, then they will follow the path of light, just like light.
Light bends and so do they.
Einstein had a flash of inspiration. He felt that this phenomenon made gravity seem to not exist.
Whether it is light, basketball or chicken, they all seem to be moving on a determined path.
What does it mean?
For example, there is a smooth track with a rugged shape.
Then no matter what you put in, they will take the same route.
It can only be the shape of the track itself.
Because the route has been determined, it is this shape.
No matter what substance or speed, it cannot affect the orbit.
At this point, Einstein discovered a shocking secret: gravity does not exist, and what changes the trajectory of objects is space-time itself.
So he boldly guessed: The essence of gravity is the curvature of space and time!
Boom!
After reasoning to this point, Li Qiwei felt thunder exploding in his mind.
There seems to be a stream of heat in the chest that rushes straight to Tianling Gai!
The heat burst out, forming a dominating figure.
The figure stands on the earth, with its back to all living beings, facing the vast universe.
He gently spit out a note: "Power!"
The sound faced the space and spread out like an explosion, reaching the edge of the universe.
Falling in the ears of all beings in the universe, it is like a great bell, swallowing up mountains and rivers, and extremely domineering.
Li Qiwei took a deep breath and slowly recalled the vision.
He deduced step by step from Newton's laws and finally discovered the relationship between gravity and the curvature of space and time.
Is there anything more exciting and crazy than this?
He had never done anything like this in his previous life because he didn't have that special environment.
Now, even though he is deaf to what is going on outside the window, he already knows the expectations of the outside world through Delia.
He is now the center of physics, and the trend of the entire era falls on his shoulders.
At this moment, his brain seemed to have evolved, gradually getting closer to a true genius.
Li Qiwei’s breathing accelerated, his heart beat faster, and the tip of his pen trembled.
The mystery of the universe seemed to materialize at this moment.
Hold in his hand, it bends and wraps like a strange and magnificent light.
Li Qiwei took a deep breath again and slowly calmed down. The matter was not over yet.
Next, he will find a way to prove the shocking point of time and space curvature.
The old rule is still a thought experiment, don’t do it if you can’t do it.
This is the famous disc experiment.
Now, please close your eyes.
Imagine a huge disk in the dark, vast and lonely space.
At this time there are two people standing on the disk, namely X and Y.
X stands at the center of the disk, and Y stands at the edge of the disk.
Now, the giant disk begins to rotate clockwise, producing a centripetal acceleration that is exactly equal to the Earth's gravitational acceleration.
(Note: Although the speed of the disk rotation remains unchanged, it is still a variable-speed motion, because the direction of motion is changing all the time.)
(The acceleration direction of circular motion always points to The center of the circle. )
Then it’s the same as a spaceship.
Y, who is standing on the edge of the disk at this moment, is moving with the disk. Therefore, he will experience an inertial centrifugal force, the magnitude of which is equal to the gravitational force he experiences on the surface of the earth.
So Y will feel as if he is still standing on the earth, which is very comfortable.
But X felt uncomfortable.
Because he is in the center of the disk.
The disc does not exert any inertial force on him, and there is no gravitational force.
So X will become weightless, which is equivalent to him standing at the center of the earth.
This disk is a device equivalent to the earth's gravitational field.
According to the special theory of relativity, Y is accelerating relative to X at this time.
(Don’t ask the other way around, why X is not accelerating relative to Y, it is explained in the previous chapter.)
So Y’s time is slower than X’s time. (Slow clock effect)
Since the acceleration of the disk is equivalent to gravity.
So we can think that gravity causes time in Y to slow down.
If the center X begins to gradually approach Y at this time, then its time will gradually slow down due to acceleration.
As X moves farther, the greater the inertial force acceleration he receives, and the slower time slows down.
Equivalently, the greater the gravitational force on X, the slower time will be.
Li Qiwei calculated for a while.
The process of time slowing down is a curve.
Therefore, he can conclude that gravity can cause time to bend.
Okay, let’s look at the space next.
First, let X return to the center of the disk.
Next, let X and Y measure the circumference of the disk simultaneously.
At this moment, the size of the disk measured by X is the same as the size measured by an observer on the earth.
Because both X and the Earth observer are stationary relative to the disk.
But the size measured by Y is different from X due to the shrinkage effect of special relativity.
The measured circumference of Y is larger.
Because Y appears to X and Earth observers, he has experienced a ruler shrinkage effect, so the ruler in his hand has also become shorter.
So for the same disk, his ruler needed to measure it several times before he could measure the circumference.
(Note that from X’s perspective, the circumference of the disk also shrank at the same time.)
(But the ruler in X’s hand did not shrink, so the circumference he measured was still Less than what Y measured. )
Next, Y uses the circumference he measured to calculate the pi of the disk, and he will find that the result is greater than π.
Ridgway accurately arrived at this result through complex mathematical calculations.
Logically, he can draw an inference from this disk experiment:
That is, the space where the disk is located is curved, and the pi is no longer π.
Because on a two-dimensional plane, the pi of a circle is fixed π.
But now that the pi ratio has changed, it is enough to show that the circle is no longer in a straight space.
Therefore, the huge disk in space is not in flat space.
Gravity bends space.
So far, Li Qiwei has proved that gravity will bend space and time just through clever and exquisite thought experiments.
In other words, where there is gravity, space and time are not straight.
At this point, he has perfectly proved that gravity is just an illusion and does not exist.
Gravity is just a result of the curvature of space and time. It is a geometric effect.
Essentially, it is because the curved space-time allows objects to move around, thus creating the illusion of force.
Wow!
When Li Qiwei wrote this, he let out a heavy breath.
The core theory of the earth-shattering and shocking general theory of relativity was thus completed in his hands.
No one can understand his mood at this moment.
Excitement, passion, trembling, nervousness, confusion, all kinds of emotions are intertwined together.
Even with the calm temperament he has developed over more than ten years, he can't help but be moved.
That’s the general theory of relativity!
The pinnacle representative of ideological achievements in the millions of years of human history.
It allows human thoughts to transcend the limitations of the physical body and embrace the entire universe.
There is no such thing as too much praise in any great language.
The so-called emperors, generals and ministers may not even be qualified to carry shoes in the face of this theory.
Now, Li Qiwei has created this unparalleled theory from scratch.
His heart was racing and his mouth was dry due to excitement. He picked up the tea next to him and drank it hard.
The fine tea brewed from tea leaves worth thousands of dollars is just a thirst quencher at the moment.
One word on the paper in front of him is more precious than all the tea leaves in the world put together.
Li Qiwei shouted: "Delia, add more tea."
Squeak!
Delia, who was outside the office, heard the sound and came in, holding a teapot in her hand.
As soon as she closed the door and turned around to see Li Qiwei, she suddenly let out a "yeah" and then covered her mouth.
Li Qiwei was a little confused. He didn’t have any flowers on his face. What was wrong with the other party?
However, at this moment, in Delia's eyes, the aura exuding from Li Qiwei made her sink.
What kind of charm is that?
There is an irresistible attraction to her.
It's like the best qualities of all the men in the world are concentrated in one person.
Delia has been at King's College London for several years, but has never seen a man like Li Qiwei at this moment.
Sexy, invincible and mysterious, all women dare to look at it from a distance and not to play with it.
Delia's mouth was dry and her whole body was hot. She felt like she could no longer suppress herself.
Li Qiwei's figure seemed to be infinitely tall in a trance, and even the sky could not hold him down.
The aura of wisdom exuding from her whole body made Delia almost suffocate with trembling.
This is the remnant of Li Qiwei’s aura after he had just broken through to heaven and become a saint through physics.
After discovering the great truth of the universe, Li Qiwei's temperament has completely changed.
For a woman like Delia who studies science, it is no less than the strongest drug in the world.
She stammered and said tremblingly: "Professor Bublos, you. You are."
Li Qiwei smiled and said: "What's the matter, Delia, come here and add tea."
"Did I speak too loud just now?"
Delia woke up suddenly, that kind of The feeling gradually faded away.
"No, no, I just seemed to see something incredible."
"Professor Bruce, are you okay."
Li Qiwei looked at this silly foreign girl and said with a smile: "I'm fine. I just made a major breakthrough in theory, so I drank a few more sips excitedly."
"You can refill it for me."
Delia said hurriedly, quickly walked to Li Qiwei's side, and asked excitedly while adding tea:
"Wow, Professor Bruce, your general theory of relativity is finally completed. "
Li Qiwei smiled lightly, "It's still a little bit worse, but it's getting close."
Delia smiled sweetly, and her chest trembled violently again, making Li Qiwei's eyelids jump when he glanced at her.
After Delia added tea, she went out quietly. She did not dare to disturb Professor Bruce to continue thinking.
When she walked to the door, she suddenly felt something strange in her lower body. Her cheeks turned red with shame, and she hid her face and ran away.
However, our gentleman, Mr. Li Sanshao, did not squint his eyes and did not see this scene.
At this moment, after replenishing his energy with tea, he regained his energy and focused on the paper again.
It is now known that the essence of gravity is the curvature of space-time.
The next natural step is to study how space and time are curved.
The classic saying of later generations: Matter tells space-time how to bend, and space-time tells matter how to move.
So what exactly is this "how"?
(End of this chapter)