1900: A physics genius wandering around Europe

Chapter 255 We've never actually measured the speed of light!
The inverse square law problem of universal gravitation raised by Li Qiwei was like a piece of ice, calming the students present from their enthusiasm for modern physics.

It turns out that the physics that the big guys study and the physics they learn in textbooks are completely different things.

You think you have understood it, but in fact it is because you have learned too little.

In real history, Bohr once said: If you think you understand quantum mechanics when you first learn it, it means you don’t understand it yet.

Although classical physics is not as difficult to understand as quantum mechanics, it is not something that can be mastered easily.

The interest of the students in the auditorium has now been fully aroused.

They usually don't hear such vivid and in-depth physics courses in class.

Many teachers just read from the textbook.

Moreover, some professors have strong academic capabilities, but their teaching skills are average.

Academics and teaching are two abilities.

In real history, Einstein achieved such great achievements, but I have never heard of him teaching any outstanding students.

Many people complained that Einstein was not good at teaching students.
And now, Li Qiwei's speech let the students present know what the top teaching ability is.

Even the other party is not really teaching, it's just a speech.

Bohr and Master Qian Wu looked at Li Qiwei with admiration.

In fact, they both didn't know why it was an inverse square proportion just now, but they suddenly realized it after listening to Li Qiwei's explanation.

It even dawned on me that Newton's law of universal gravitation was also imperfect.

This shows that there must be some problem with the inverse square law.

At this moment, they realized how lucky they were to be Professor Bruce's doctoral students.

The people present were probably going crazy thinking about this.

Young people love the excitement the most, but at the same time they hate it the most when the excitement ends.

When Li Qiwei raised such a novel question, everyone did not think about figuring out the mechanism behind the problem immediately, but whether they could come up with another one?
It’s so enjoyable to listen to.

So, the young man who asked the first question suddenly asked provocatively: "Professor Bruce, are there any similar questions in classical physics?"

"Tell us more so we can go down and study it carefully."

Wow!
As soon as these words were spoken, they resonated instantly.

"Yes, Professor Bruce, one more please."

"You have finally come to the United States, you can't hide anything."

"Physics is so interesting, Professor Bruce, please tell me more about it."

"."

Unexpectedly, the situation suddenly turned out like this, which made Li Qiwei laugh and cry.

Even Woodrow, Michelson and others were helpless.

Today's speech is destined to run in an unknown direction.

There is no way, there are too many students in the auditorium.

Students in this era are not like the obedient children in later generations. They have to sit up straight when listening to the leader’s speech and dare not play with their mobile phones.

Especially in Europe and the United States, students are first-rate in their ability to stir up trouble.

Li Qiwei calmed down and said, "Okay, then I'll tell you another one."

“In fact, as long as you have a pair of eyes that are good at discovering and a mind that is good at doubting, you can also ask a lot of questions.”

"And the issue I am going to talk about next is related to someone here."

hum!
The people in the venue suddenly burst into surprise.

The questions raised by Professor Bruce are definitely related to physics.

Almost all the famous American physicists are here today.

But objectively speaking, we have to admit that there is still a big gap between their level and that of European physicists.

Even current leading figures in the United States such as Professor Michelson and Professor Millikan.

If they were placed in Europe, they would not be considered first-tier physicists.

Although both of them are bigwigs who participated in the first Bruce Conference, there are differences between bigwigs.

However, Professor Bruce said that the next question was related to the people present.

Anyway, it definitely wasn't him, so who could it be?
Everyone present became curious.

At this time, Li Qiwei smiled and said, "Let me ask a small question first. Does anyone know about the Michelson-Morley experiment?"

"Hubble, you know what?"

Wow!
Everyone laughed.

Obviously, as a physics student in the United States, it would be embarrassing if you didn't know about this experiment.

The original author of the experiment was sitting in the front row.

Hubble didn't react at first. He didn't expect Professor Bruce to call his name alone.

But he was very happy in his heart.

Why did Professor Bruce not ask others to answer but called himself instead? It shows that the other party values ​​himself.

It seems that Professor Bruce was deeply impressed by his answer.

Hubble's heart was moved.

This question is also very simple, it’s not even a question.

Hubble said confidently, "Professor Bruce, of course I know."

"The Michelson-Morley experiment is also the first dark cloud problem."

"Through this experiment, Professor Michelson measured the speed of light to be 30 kilometers per second."

"And it has nothing to do with the reference frame, which proves that the ether does not exist."

"Moreover, it was to solve this experiment that you published the special theory of relativity that shocked the world."

Hubble took the opportunity to flatter him.

Li Qiwei smiled and nodded, saying, "Well, Hubble is very good."

Michelson in the audience was suddenly stunned. Why did Bruce talk about him?

Is there something wrong with this experiment?

That's impossible, his special theory of relativity is based on the results of this experiment.

If there is a problem with the Michelson-Morley experiment, there will also be a problem with the special theory of relativity.

Isn't Bruce turning against himself?

Li Qiwei suddenly looked at Michelson and said jokingly: "Professor Michelson, don't be nervous."

"There's nothing wrong with your experiment, and I won't prove you wrong in public."

Everyone laughed again.

Li Qiwei turned his head and looked at Hubble and asked, "Hubble, you said the speed of light is 30 kilometers per second."

"Then let me ask, do you agree with this statement?"

"Do you really think that physicists have measured the true speed of light?"

boom!
As soon as Li Qiwei's question came out.

The audience was instantly shocked.

Hubble was stunned and at a loss, completely unable to understand what Ridgway meant.

His mind was racing.

"Hasn't the speed of light been measured by many physicists?"

"Although there is no most accurate result, that is just a matter of the accuracy of the measuring instrument."

“It does not affect the correctness of the experiment itself at all.”

"And isn't speed equal to distance divided by time?"

"From what Professor Bruce said, we have never actually measured the speed of light?"

"Oh my God, how is this possible!"

Outsiders don’t know that Hubble is experiencing a crazy struggle between conscience and desire in his heart at this moment.

Everyone present wondered if Professor Bruce had gone mad. Was there something wrong with the speed of light?

"Wow, don't tell me there's a problem with the speed of light. Isn't speed the simplest physical quantity?"

"We have measured the speed many times in the lab class."

"Although the speed of light is fast, it is still a speed. This does not affect the way it is measured."

"I don't understand. I really don't understand."

At this moment, Professor Michelson in the front row thought of something and suddenly smiled bitterly.

"Bruce, Bruce, you are really good at educating these young students."

"What the hell is wrong with your brain?"

Clearly, Michelson knew where the problem lay.

But Hubble did not have Michelson's experience, and at this moment he did not know whether he should answer.

This simple question made Hubble deeply doubt what he had learned.

The person who asked the question was not a folk scientist, but Bruce Lee, the number one physicist today.

No matter how simple a problem is, it will become no longer simple after his blessing.

But Hubble really didn't know what the problem was.

So he had to answer honestly: "Sorry, Professor Bruce, I agree with this conclusion."

No one laughed at Hubble, everyone stood firmly on his side.

Seeing how stressed Hubble was, Li Qiwei quickly said with a smile, "Hubble, don't be nervous."

“It’s just a speech.”

"We are not discussing the issue specifically, just treat it as a casual chat."

Hubble finally felt relieved. He was particularly afraid of leaving a bad impression on Professor Bruce.

That would make him feel unworthy of the other person's compliment.

At this point, Li Qiwei stopped keeping the secret and said, "If you carefully study the original text of my special theory of relativity, you will find a detail."

"When I defined the speed of light in my paper, I did not use a one-way definition, but an average speed."

"What does that mean?"

"Suppose light travels from A to B, and then from B back to A."

"The speed of light I defined is the average of these two speeds, not the one-way speed of light from A to B or B to A."

“These two speeds are not the same thing.”

"We've never actually measured the one-way speed of light."

boom!
Li Qiwei's words were like a huge stone thrown into a small pond, causing a huge sensation.

Everyone's eyes widened in disbelief.

"What, the speed of light has never actually been measured?"

"You're wrong. The one-way speed of light has never been actually measured."

"I seem to understand what Professor Bruce means. My God, this is amazing."

"Shift, what on earth are you discussing? Isn't the speed of light 30 kilometers per second? How come there is a one-way speed of light?"

Li Qiwei looked at the surprised expressions of the crowd and knew that many people did not understand what it meant.

So, he continued, “Let me give you an example.”

"Suppose a person drives from A to B at a speed of 100 km/h, and then drives from B back to A at a speed of 50 km/h."

"So what's this person's average speed?"

"According to the average speed formula, we can easily deduce that it is 66.67 km/h."

"The calculation process is very simple. Just use a pen to verify it. I won't write it on the blackboard."

"Then the problem arises."

"The same is probably true for the speed of light. The so-called 30 kilometers per second is just an average round-trip speed."

"Perhaps the speed of light from A to B is 100 million kilometers per second, and the speed from B to A is 17.65 kilometers per second."

"Calculated in this way, the average speed is also 30 kilometers per second."

"We don't know what the true one-way speed of light is."

"You can even say that it is an arbitrary value, as long as the average speed is 30 kilometers per second."

boom!
After Li Qiwei finished explaining, everyone understood what he meant.

However, after understanding it, they became even more confused.

This is simply like a fairy tale.

The speed of light has never been actually measured?

Is there anything more incredible than this?
Why is the speed of light so strange? Why can't we just use the one-way speed, but have to use the average speed?

Many people couldn't help but ask questions at once.

"Professor Bruce, why don't physicists measure the one-way speed of light?"

"Since we can measure average speed, we should be able to measure one-way speed, right?"

Facing everyone's questions, Li Qiwei shook his head and said, "It can't be measured."

"It's impossible to measure the speed of light in one direction."

"I wrote explicitly in the special theory of relativity that the constancy of the speed of light is only an assumption that cannot be verified experimentally."

"And I agreed that the speed of light is the same in all directions of space."

“Only in this way can we ensure the validity of [simultaneity].”

"So, the speed of light I used is the average speed, not the one-way speed."

boom!
This time everyone was so shocked that they were speechless.

The famous genius of physics actually said that the one-way speed of light cannot be measured.

The three views of many people have collapsed.

Michelson looked at Li Qiwei and sighed continuously.

Even Millikan was not sure what was going on.

As for the other physicists, like the students present, they had no idea what was going on.

Michelson seemed to recall the past when he said, "In 1849, French physicist Fizeau used the gear method to measure the speed of light with relative accuracy for the first time."

“His experiments were very ingenious.”

"Fizzo placed a reflector and a light source at two locations far apart, and there was a gear in front of the light source."

"When the light passes through the rotating gear, it hits the reflector and then passes through the gear again."

"As long as the gear rotates at the right speed, the light will be blocked by the gear teeth after passing through the reflector."

"The light is then invisible to the observer."

"Then, through the speed of the gear, the number of teeth, and the distance traveled by the light, we can easily calculate the speed of light."

"Fizeau measured the speed of light to be 315000 kilometers per second."

"This is very close to the precise speed of light measured now."

"However, you should have discovered that Fizeau's method still measures the average speed of light, not the one-way speed."

"Even now, we cannot measure the one-way speed of light."

"It's not that we don't want to test it, but Bruce's special theory of relativity makes it impossible for us to test it in principle."

"Bruce is to blame for all this."

Michelson thought he had made it very clear because he had studied the special theory of relativity very deeply.

But Millikan and others were still confused.

At this time, many students couldn't help but ask: "Professor Bruce, why can't we measure the one-way speed of light?"

Li Qiwei smiled slightly.

(End of this chapter)