1900: A physics genius wandering around Europe

Chapter 119 Question : Inertial Reference Frame
Einstein stood on the stage, and below him was a huge crowd of people.

He adjusted his condition to his best and turned on the projector. He had practiced it under Li Qiwei's guidance before.

Suddenly, a huge shadow of light was projected onto the wall behind.

The text on the screen is clear and the colors are bright, so even in the last row of the venue, you can see it clearly.

Now the homepage displays the big words “The First Relativity Symposium”.

That was written by Einstein on the spot.

Whatever he writes on the template on the projector will be displayed on the big screen in real time.

It looks exactly the same as the PPT of later generations, and is easier to modify.

The participants were immediately attracted by this gadget, which was simply a tailor-made instrument for scientists' meetings.

But soon, they were shocked by the content of the speech.

With the help of the projector, Einstein became even more powerful.

As a young man in his twenties, he had no idea what foreshadowing, transitions, warm-up, etc. were.

He started by tearing up the formula by hand, and with a few clicks, he derived the core formula of the theory of relativity on the spot.

"Ladies and gentlemen, the premise of the theory of relativity is two axioms."

"The first is that all the laws of physics are equivalent in all inertial reference frames (reference frames at rest or in linear motion)."

"The second is that the speed of light in a vacuum, c, is always constant in all inertial reference frames."

"And the core of relativity is the relativity of space and time."

"Only by understanding that space and time are relative can we reasonably explain the speed of light."

"And according to the formula, the speed of any substance cannot reach the speed of light, and the speed of information transmission cannot exceed the speed of light."

"The faster an object is moving, the slower the time it experiences relative to a stationary observer."

"The object's length will also appear shorter when measured in the direction of motion."

"It is important to note that the shortening here is relative to a stationary observer."

"The observer on the object itself does not change the size of the object when measuring it."

“The above is the core conclusion of the theory of relativity.”

"According to Newton's absolute view of space and time, time and space are independent of each other."

"And both are uniformly distributed, regardless of the object's state of motion."

"But the theory of relativity holds that space and time are an indivisible whole that is related to the speed of an object's movement."

"These are the explanations of the theory of relativity. Please feel free to ask questions."

After Einstein finished speaking, there was silence in the conference hall.

Everyone looked at the formula on the screen, thinking silently, and exclaimed in surprise from time to time.

Einstein's explanation on the spot was indeed more vivid and easier to understand than reading the paper yourself.

Soon, some young people who were fearless like a newborn calf began to ask questions at Lorenz's signal.

The first person to appear is Laue. In real history, Laue later became Einstein's lifelong best friend, and the two often exchanged academic ideas together.

"Hello, Einstein."

"My question is, since the premise of relativity is that objects must be in an inertial reference frame to be valid."

"So, if an object is moving with acceleration, how does relativity deal with it?"

"It can't be just a theory that needs to be strictly restricted."

When the question came up, it did not cause the commotion that one might have imagined.

Obviously, this is a basic question, very suitable for a little Karami like Laue to raise.

Almost all the physicists and physicists present could think of it.

After listening to the question carefully, Einstein smiled and said, "Thank you very much for your question, Laue. This is a very good question."

"The premise for Newton's laws of motion is also an inertial system."

"But when dealing with objects that are accelerating, Newton's laws of motion still apply."

“Similarly, although the basis of relativity is inertial system, it does not mean that it cannot deal with the motion of non-inertial system.”

"If an object moves at a variable speed in an inertial system, we can use the idea of ​​calculus to solve it."

"That is to establish multiple instantaneous inertial systems and then perform integral operations on all processes." "In this way, the theory of relativity can be used to describe speed changes."

Go ahead, Einstein started calculating.

The LQW transformation was calculated immediately, and the integral of the change in speed dazzled the people present.

Everyone was impressed by the young man on the stage's profound mathematical skills.

Soon, a beautiful result appeared before everyone.

The theory of relativity can fully deal with the problems of non-inertial frames.

Laue was also impressed by the concise and elegant proof, and he was the first to applaud in agreement.

Immediately afterwards, there was applause in the conference hall.

Obviously, a small inertial system problem is not enough to move the physics masters.

At this time, another young man asked a question. Li Qiwei looked at him and found that it was Born.

At the last young scholars exchange meeting, this young man left a very deep impression on everyone.

He has a sharp vision, a tricky perspective, and a jumping mind. He is an absolute genius.

Sure enough, Born asked a sharp question:

"Hello, Einstein, my question requires a thought experiment."

"Suppose there are two identical trains, A and B, moving at nearly the speed of light."

"They are on two parallel tracks, A on the top and B on the bottom, moving towards each other at the same speed."

“Let’s make a rule.”

"Event 1 means the front of train A meets the rear of train B."

"Event 2 means the front of train B meets the rear of train A."

"If we were standing on stationary ground and looking at it, event 1 and event 2 should have occurred at the same time."

"But according to the calculations of relativity, the people on train A will observe that train B becomes shorter due to the motion of train B."

"This is caused by the shrinkage effect you derived."

"So, for the people on train A, event 1 happened first and event 2 happened later."

"But by the same token, for the people on train B, event 2 happens first, and event 1 happens later."

"Isn't this a contradiction? Events 1 and 2 should have happened at the same time."

"How does the theory of relativity explain this problem?"

Wow!
After Born asked his question, everyone present looked sideways at this boastful young man.

Many people didn’t even understand the question, what 1 and 2, A and B, but they still felt it was powerful.

Even the physics masters couldn't help but observe each other. The young man who asked the question was not simple!
This thought experiment is very interesting, and it is essentially a problem between reference frames.

However, through logical thinking, we can find the contradictions between the theory of relativity and logic.

Great!

Everyone gave Born their evaluation in their hearts.

Now, besides studying physics, Born's favorite subjects are logic and mathematics.

That is why he was able to find loopholes in the so-called theory of relativity with his extremely insightful ideas.

Einstein also admired Born very much, and thought to himself that the heroes of the world are really like you who crossed the river. How wonderful!
He quickly drew a diagram on the screen based on Born's question.

Sure enough, when the schematic diagram came out, everyone understood the problem.

Then I realized that Born is really a genius.

This question does seem very contradictory.

It's obviously the same thing, so why do different people see different orders of events?
So, everyone in the audience couldn't help but look at Einstein.

They wanted to know how the young man could explain this problem.

On the stage, Einstein smiled slightly, as if everything was under control.

Does anyone know this question about Born?

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(End of this chapter)