Before talking about this problem, let's talk about the difference between quantum mechanics and relativity:
First, quantum mechanics is the product of brainstorming by many scientists, and Einstein obtained the theory of relativity by himself.
Second, quantum mechanics was accumulated bit by bit from Planck, while relativity was born overnight.
Third, quantum mechanics, no matter how absurd, at least begins with experimental phenomena. In order to explain the experimental results and piece together various theoretical formulas, Einstein fabricated the theory of relativity out of thin air, and then searched for experimental phenomena according to the theory.
Fourth, quantum mechanics has won numerous Nobel Prizes, while relativity has never won any prizes.
Fifth, quantum mechanics has been widely used for a long time and many people may not know it. They think that quantum mechanics is just a physicist's game. In fact, most of the brilliant achievements of modern science and technology are attributed to quantum mechanics, while relativity provides no production technology except calculation and calibration.
Sixth, quantum mechanics is applied to microscopic, electronic, proton and so on. , and the theory of relativity applies to the macro, stars, time and space.
Seventh, the world described by quantum mechanics is fragmented and quantized, while the world described by relativity is continuous.
Tell me, is this coincidence a bit excessive, which makes people wonder if God is playing tricks on mankind. Relativity and quantum mechanics seem to be consistent, so contradictory, but both are so shocking, which really tortured several generations of physicists!
Physicists are born with the idea of "great unity", so it is best to sum up all the laws in the universe into a formula. In order to match these two theories, human beings have made great efforts. Let's leave this touching story for later.
In fact, in the era of classical physics, it is also a unified story. After the "Newton era", classical physics gradually gathered and moved towards unity.
The peak of the road to "great unification" is not Maxwell's equations, but at least it ranks in the top three of the greatest formulas of mankind!
It's easy to say. Electricity and magnetism used to be two different people, but since Faraday Q discovered electromagnetic induction, everyone knows that the ambiguous relationship between electricity and magnetism has a long history, but they suffer from no matchmaker. Just when everyone was in a hurry, Maxwell made a stroke of his pen, and electricity and magnetism became a family from then on.
Maxwell's equations, in an extremely beautiful form, fully expounded the mutual transformation law of electricity and magnetism, which is a rare beauty in physics! Since it is rich and beautiful, it will inevitably attract bees and butterflies, including our protagonist Einstein today.
Einstein has always had a soft spot for "light". Light is electromagnetic wave, and electromagnetic wave belongs to Maxwell, so Einstein looked at this set of equations in a daze. This scene is like Yang Guo's ecstasy. Einstein looked at it and suddenly had an epiphany. He put forward an ecstasy hypothesis: the principle of constant speed of light.
What does the principle of constant speed of light mean? For example, if you stand still on the side of the road, my riding speed is 10, and my sister's driving speed is 50, then my sister's speed is 50 and I'm 40.
This is our normal understanding, right?
In the same scene, the girl is replaced by a beam of light, so it should be: the speed of light is 300,000, and I am 299,990, right? Einstein said you don't know much about light. No matter what your speed is, her speed will always be 300,000.
In extreme cases, your speed is 0 and my speed is 299,999. The same "light" passes through us. This speed of light is 300,000 for you and 300,000 for me!
So is this one lamp or two lamps? Of course, it is a beam of light, but this beam of light is always the same speed for different people. The starting point of relativity comes from such an extremely absurd assumption: the principle of constant speed of light!
Since the speed of light is absolutely constant, it should be called "absolutism". Why is it called "relativity"?
The concept of relativity corresponds to the concept of absolute space-time. Academically speaking, all physical laws have the same mathematical form in all inertial reference frames, and the scientific name is the principle of relativity. This is the second hypothesis of relativity. I know you can't understand the meaning of this sentence. Don't worry.
This topic has a philosophical flavor again.
Back to the scene just now, the speed of my bike is 10, and you are standing on the side of the road. Suppose the whole system or the whole universe is just you and me, then who is moving?
It seems to you that I am moving, and it seems to me that you are moving. To find out who is moving, suppose my speed relative to you is 10. This is the content of high school physics, which is not difficult for people to understand today, but it is different under the background of "ether" theory at that time.
What is "ether"?
It is also the concept put forward by Aristotle, an old classmate: space is ether, but we can't see it. Both stillness and motion are relative to space, that is, "my speed relative to space is 10", not "my speed relative to you is 10". This view, together with the eternal one-dimensional time, is called the "absolute view of time and space" in Newton's era.
This was a very mainstream assumption at that time. Michelson, a famous scientist, Nobel Prize winner in physics and absolute Daniel, has been looking for ether for eight years, and he strangled the ether theory himself.
Regression relativity
"The principle of invariance of the speed of light" and "the principle of relativity", okay, then what? With these two, you can subvert the world? Yes, these two are enough. Attention, everyone! Old driver Einstein is racing!
Suppose the old driver soars to 50% of the speed of light, and then a beam of light shines vertically on the floor from the ceiling of the carriage. For the people in the carriage, there is no speed in the carriage, which is equivalent to shining a beam of light from top to bottom in the stationary carriage. Then the result is very simple, this light just shines on the ground in a straight line. So the distance traveled by this beam of light is the height of the carriage and the time it takes: the height/speed of light of the carriage.
But for people outside the car, things are a bit troublesome. The light beam shines from top to bottom in the moving carriage. In this process, the carriage has been moving, so the path of light is a diagonal.
It's like a bullet hitting the ground from the top of a car. To people inside the carriage, the bullet fell straight, but to people outside the carriage, the bullet actually fell obliquely. Of course, running sideways is farther than running straight.
This is no problem in classical physics. Because the speed of the bullet should be combined with the moving speed of the carriage, the actual speed of the bullet has increased, even if the distance has increased, the final time is the same.
However, Einstein said that the speed of light is constant, no matter what the speed of your car is, the speed of light is still the same, so things will get better, because the distance increases, the speed of light remains the same, so the time has to increase!
The same thing, spending more time in the car than outside, is hard to explain.
Einstein said, what's wrong? The speed of light is constant, so we can only be wronged by time. Yes, the time in the carriage is bloated!
Time is invisible and intangible. Einstein can say whatever he wants. Let's take another example.
When the old driver is racing, flashing a light in the middle of the car is equivalent to lighting a light bulb. For the people in the carriage, the carriage is still, so the light should illuminate both the front wall and the back wall. But for people outside the carriage, the car is moving forward and the speed of light is constant, so the light should illuminate the back wall first and then the front wall. This is not a question of whether time expands or not.
If there are two receivers on the front and rear walls, do they receive signals simultaneously or in series?
Einstein said that you have no idea what "at the same time" means. How to judge whether two events in two places happen at the same time? When these two events occur, they will send out flashing signals. If the light reaches the middle of these two places at the same time, then these two events are considered to be simultaneous, otherwise they are not simultaneous. Therefore, people inside the carriage watch at the same time, while people outside the carriage watch at different times, and "at the same time" is also relative.
You got it? This "light" is really a collection of Einstein's thousands of favorites, and even time must follow the footsteps of light.
For another example, suppose the sun suddenly disappears, and after 8 minutes, the earth will know. Is it possible for people on earth to know at the moment when the sun disappears? Einstein said, absolutely impossible. After the sun disappears, the earth can still feel the sun and its gravity. No matter how you use it, it is impossible to know that the sun has disappeared within 8 minutes.
Even if you find someone calling you from the sun, it will take 8 minutes for the radio signal to fly to the earth. Then the problem is coming. For people on earth, did the sun disappear eight minutes ago or now?
Ok, I admit I'm a little confused, so I'll mess up the question a little more. How do people in the car measure the length of the car?
This is very simple. Just take a scale and measure it directly. But it is more troublesome for people outside the carriage, because the carriage is moving. But the scale you're holding is still.
You must write down the scale readings before and after the car at the same time. If you follow Einstein's definition of the same time, then you will find that a moving car is shorter than a stationary car. Is this conclusion a bit ridiculous?
Einstein said that in the face of "light", time can be wronged, and the length is nothing! The length of an object will shrink along the direction of motion, which is called "length contraction effect" or "scale contraction effect" for short. Come on, the quality will probably be difficult to guarantee.
Yes, because time is related to speed, speed is related to kinetic energy, and kinetic energy is related to quality, so quality is not the original quality. Einstein said: mass will increase with the increase of speed, and then combined with momentum and kinetic energy formulas, the famous mass-energy equation is obtained: e = e = the square of MC.
Einstein confused time, length and quality, but in essence it was nothing more than the formula conversion between the moving reference system and the static reference system. Students who are good at math are beginning to show off in an ostentatious manner. Time expansion, length shortening and mass increase can all be deduced from Lorentz transformation:
Look at these formulas, and you will understand why Einstein didn't like superluminal. According to the above formula, once an object reaches the speed of light, time becomes infinitely slow, length becomes infinitely small and mass becomes infinitely large. In the end, even Einstein himself could not accept this nonsense.
Have you noticed that the assumptions just mentioned are all discussed on the premise of constant speed and stillness? This kind of scenario is only applicable to the ideal situation, and the application scenario is relatively narrow, so it is called "special relativity".
In fact, it is often necessary to add gravity or acceleration to the system, and the application scenarios are more extensive. As the name implies, this is "general relativity".
General relativity is not only wonderful in content, but also extremely complicated in mathematics. Einstein had to turn to mathematician Grossman to finish his thesis "Outline of General Relativity and Gravity Theory". This great paper, except the students in the department of mathematics and physics, should not be read by other students, so as not to irritate their eyes!
Eddington, a British scientist, is a big fan of Einstein and the first person to introduce general relativity into the English-speaking world.
One day, Eddington was asked, "Dear professor, I heard that only three people in the world know the theory of relativity. Is that so? After thinking about it, Eddington Luke replied, "You may be right, but I want to know who the third person is? 」
This little story eventually evolved into a myth that we often hear now: only three people in the world understand the theory of relativity. This is of course an exaggeration, but general relativity is indeed more troublesome than quantum mechanics.
Bohr said that quantum mechanics can't be learned for the first time, but on the other hand, there is still hope for learning more times. As for the general theory of relativity, we ordinary people should start treatment as soon as possible. We can only copy mechanically, just swallow the dates.
The following is the general theory of relativity:
The old driver stepped on the accelerator hard, and the car accelerated. Pay attention to the acceleration. A beam of light shines from the roof to the floor, the speed of light is constant, and the speed of the car is getting faster and faster, just like the water is flowing downwards and the car is accelerating, so the water flow should be curved, that is, the path of light propagation should be curved.
Einstein said that the speed of light can't be changed, only space can be wronged, and space is curved! This is a lie, obviously you bent it yourself, not the space!
Einstein went on to say that "gravity" and "acceleration" are equivalent, so gravity will also lead to space bending. Then imagine, if the gravity is strong enough and the space is curved enough, like origami, what will happen if the two points at the far end bend and overlap?
Yes, the concept of wormhole exists! Open a wormhole and tear the space, you can go directly from this point to another point, and this is how the fantastic space jump comes from!
So far, you can still think that all this is nonsense and call Einstein a grandstanding stick!
The theory of relativity at this time, like explosives buried in the physics building, is just a fuse. However, people soon discovered countless fuses that detonated this classic building for hundreds of years.
19 1 1 year, Einstein published the influence of gravity on light propagation. Because the gravity and mass of the sun will bend the surrounding space, light will bend when it passes near the sun. This phenomenon can be observed in the total solar eclipse.
Eddington, a loyal fan, cheated the British government into funding this absurd test. Finally, the observation data show that the position of the constant star has indeed shifted, which is consistent with the calculation results of relativity. Eddington said with emotion: This little movement has changed the world.
Thus, Einstein became famous overnight, and Chaplin's quip properly summed up the scene at that time: "People cheered for me because they understood my art, and people cheered for Einstein because no one understood his theory.
The precession of Mercury's perihelion, which has puzzled astronomy for many years, has also been satisfactorily explained. When Mercury moves to perihelion, there will be some extra precession (we ordinary people can understand that when Mercury approaches the sun, there will be some inexplicable jitter). The extra precession value is 43 seconds every hundred years, and no one can explain it at that time.
Einstein calculated that the curvature of the sun to space is exactly 43 arc seconds every hundred years, which is exactly the same, that is to say, this extra precession is caused by the curvature of space. Later measured Venus data also accord with the theory of relativity.
In order to verify the influence of gravity and speed on time, scientists have sent atomic clocks to outer space, and the time deviation caused by gravity is completely in line with the calculation of relativity.
All experiments have proved that the theory of relativity is reliable, and it is definitely not the product of madman's fantasy.
Relativity unveiled the cloak of this absurd world with an overwhelming attitude, and once again made human beings realize their ignorance and smallness.
I want to worship Einstein again! You know, people at that time had been immersed in the great shock brought by quantum mechanics: everything was fragmentary and the position was random, but the spatial description of relativity was continuous and accurate, which was completely contradictory to quantum mechanics and simply moved against the general trend!
No one expected that God would give mankind two completely different gifts at the same time! What is more commendable is that Einstein is not only one of the founders of quantum mechanics, but also the pioneer of relativity. This skill of "left-right struggle" dare not say "no one came after", at least "unprecedented"
Therefore, Einstein's position in the history of physics is second only to that of Newton.
However, the application of relativity is rare, and it is only used to calibrate various observation data or experimental equipment, such as GPS accuracy calibration, changes in the mass and life of high-energy particles, or predicting the existence of gravitational waves.
Looking back at this mess, Einstein drove away with a bang, but countless physicists have gone crazy about the starting point of this theory: the principle of constant speed of light.
Relativity and quantum mechanics abruptly split the trunk of the tree of science and technology into two directions, but physicists stubbornly believe that the origin of things is the same in the end. In the past 100 years, everyone dreamed of unifying these two theories, but they all failed!
Although the road ahead is long, everyone is still running tirelessly on the road of reunification. The "superstring theory" and the large collider, which are very popular in recent years, are another charge to the cause of great reunification.