Chapter 255 We have never actually measured the speed of light!
The inverse square problem of gravity raised by Li Qiwei was like a piece of ice, cooling down the students present from their enthusiasm for modern physics.
It turns out that the physics studied by the big guys and the physics they learned in textbooks are completely different things.
You think you understand it, but it’s actually because you have learned too little.
In real history, Bohr once said: If you think you understand quantum mechanics for the first time, it means you haven’t understood it yet.
Although classical physics is not as difficult to understand as quantum mechanics, it is not something that can be mastered casually.
The interest of the students in the auditorium has been completely aroused at this moment.
They usually never hear such vivid and in-depth physics courses in class.
Many teachers only follow the instructions.
And some professors are very good at academic level, but their teaching level is average.
Academics and teaching are two abilities.
In real history, Einstein made so many achievements, but I have never heard of any outstanding students he taught.
Many people complained that Einstein could not teach students.
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 is just a speech.
Bohr and Master Qian looked at Li Qiwei with admiration.
In fact, they didn't know why it was an inverse square ratio just now. They suddenly realized it after listening to Li Qiwei's explanation.
It even suddenly dawned on me that Newton’s law of universal gravitation was also imperfect.
This shows that there must be some problems with the inverse square ratio.
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 it.
Young people like the excitement the most, and at the same time they least like it to end.
When Li Qiwei raised such a novel question, what everyone thought about was not to immediately figure out the mechanism behind the problem, but whether there could be another one?
It’s so enjoyable to listen to.
So, the young man who first asked the question suddenly asked provocatively: "Professor Bruce, are there any similar questions in classical physics?"
"If you tell me more, we can go down and study it carefully."
Wow!
As soon as these words came out, they resonated instantly.
"Yes, Professor Bruce, let's do one more."
"It's hard for you to come to the United States, so you can't hide your secrets."
"Physics is so interesting, Professor Bruce, please tell me more."
"."
I didn't expect that the scene suddenly turned like this, making Li Qiwei dumbfounded.
Even Woodrow, Michelson and others were helpless.
Today’s speech is destined to go in an unknown direction.
There is no way, there are too many students in the auditorium.
Students in this era are not the obedient babies of later generations. They have to sit upright when listening to the leader's speech and dare not play with their mobile phones.
Especially in Europe and the United States, students’ ability to make trouble is first-rate.
Li Qiwei calmed down and said: "Okay, then I will say one more thing."
"In fact, as long as you have a pair of eyes that are good at discovery and a mind that is good at doubting, then you can also come up with many things. Question.”
"And the question I'm going to talk about next is related to one of the people here."
Buzz!
The people at the venue suddenly burst into surprise.
The question raised by Professor Bruce must be related to physics.
Almost all the famous physicists from the United States are here today.
However, objectively admitted, their level is still far behind 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 are big guys who participated in the first blues conference, there is a difference between big guys and big guys.
However, Professor Bruce said that the next question is related to the people here.
It’s definitely not him anyway, so who could it be?
Everyone present was curious.
At this time, Li Qiwei smiled and said: "Let me ask a small question first. Does any of you know about the Michelson-Morley experiment?"
"Hubble, do you know?"
Wow!
Everyone laughed.
Obviously, as an American physics student, it would be a shame if you didn’t know about this experiment.
The original author of the experiment is sitting in the front row.
Hubble didn't react for a moment. He didn't expect Professor Bruce to call his name alone.
But he was happy in his heart.
Why Professor Bruce didn't ask others to answer, but called himself, it shows that the other party values him.
It seems that my answer left a deep impression on Professor Bruce.
Hubble's heart was filled with excitement.
This question is also very simple, 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 300,000 kilometers per second."
"And It has nothing to do with the reference system, which means that the ether does not exist."
"And it was just to solve this experiment that you published the special theory of relativity that shocked the world."
Hubble followed the trend. Flattered him a bit.
Ridgway smiled, nodded, and said, "Well, Hubble is very good."
Michelson in the audience was suddenly stunned, why did Bruce talk about himself.
Is there something wrong with this experiment?
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.
Bruce is turning against himself.
Li Qiwei suddenly looked at Michelson and said jokingly: "Professor Michelson, don't be nervous."
"There is nothing wrong with your experiment, and I will not prove you wrong in public. ”
Everyone laughed again.
Ridgway turned his head, then looked at Hubble and asked: "Hubble, you said the speed of light is 300,000 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 up.
The audience was instantly shocked.
Hubble was dumbfounded and had no idea what Li Qiwei meant.
His brain was working rapidly.
“Hasn’t the speed of light been measured by many physicists?”
“Although the most accurate result is not available, that is just a matter of the accuracy of the measuring instrument.”
< br>"It does not affect the correctness of the experiment itself at all."
"And isn't speed equal to distance divided by time?"
"Listen to Professor Bruce, we have never really measured the speed of light?"
"My God, how is this possible? ! ”
Outsiders don’t know that a crazy war between heaven and man is going on in Hubble’s heart at this moment.
Everyone present felt that Professor Bruce was crazy. Is there any problem with the speed of light?
"Wow, don't tell me, there is a problem with the speed of light. Isn't speed the simplest physical quantity?"
"We have measured the speed how many times in the experimental class."
“Although the speed of light is fast, it is still speed. This does not affect its measurement method.”
“I don’t understand, I really don’t understand.”
At this time, Professor Michelson in the front row thought of something, and he suddenly smiled bitterly.
"Bruce, Bruce, you are so good at educating these young students."
"How does your brain grow?"
Obviously, Michelson knew where the problem lay.
But Hubble did not have Michelson's experience. At this moment, he didn't know whether to answer.
Such a simple question made Hubble deeply doubtful of what he had learned.
The person who asked the question was not Minke, but Bruce Lee, the first person in physics today.
No matter how simple the question is, it will definitely become more complicated after his blessing.
But Hubble really doesn’t know what the problem is.
So he had to answer honestly: "Sorry, Professor Bruce, I agree with this conclusion."
No one laughed at Hubble; everyone was firmly on his side.
Seeing how stressed Hubble was, Li Qiwei quickly smiled and said: "Hubble, don't be nervous."
"This is just a speech."
"Neither are we. We are discussing the issue specifically, just treat it as a casual conversation."
Hubble felt relieved. He was particularly afraid of leaving a bad impression on Professor Bruce.
That would make him feel unworthy of the compliment.
At this time, Li Qiwei stopped talking and said: "If you carefully study the original text of my special theory of relativity, you will find a detail."
"I defined the speed of light in the paper. , not the one-way definition, but the average speed. "
"What does it mean?"
"Suppose the light runs from A to B, and then returns to A."
"The speed of light I define is the average of the 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 have never actually measured the speed of light in one direction.”
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 is the situation, the speed of light has never been truly measured?"
"You are wrong, the one-way speed of light has never been truly measured."
" I seem to understand what Professor Bruce means, my God, this is amazing."
"Shift, what are you talking about? Isn't the speed of light 300,000 kilometers per second? Another one-way speed of light comes out.”
Li Qiwei looked at everyone's surprised expressions and knew that many people didn't 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 at a speed of 50 km/h The speed is returned from B to A. ”
“So what is the average speed of this person?”
“According to the average speed formula, we can easily find that it is 66.67 kilometers/hour.”
"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 speed of light is likely to be the same. , the so-called 300,000 kilometers per second is just a round-trip average speed. "
"Maybe the light from A to B is 1 million kilometers per second, and from B to A is 176,500 kilometers per second. "
" Calculated in this way, the average speed is also 300,000 kilometers per second. "
"We don't know what the true one-way speed of light is."
"It can even be said that it is any value, as long as the average speed is 300,000 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 like a fantasy.
The speed of light has never been truly measured?
Is there anything more incredible than this?
Why is the speed of light so strange? Why can't we directly use one-way speed, but must use the average speed?
Many people couldn't bear it and asked questions all over the place.
"Professor Bruce, why don't physicists measure the one-way speed of light?"
"Since we can measure the average speed, we should also be able to measure the one-way speed, right?"
Facing everyone's questions, Li Qiwei shook his head and said: "It can't be measured."
"It is impossible for us to measure the one-way speed of light."
"I made it clear in the special theory of relativity He wrote: The constant speed of light is just a hypothesis and cannot be verified experimentally."
"And I have agreed that the speed of light is the same in all directions of space."
"Only in this way can [simultaneity] be guaranteed to be effective."
"So, I The speed of light used is the average speed, not the one-way speed.”
Boom!
At this time, everyone was completely shocked and speechless.
The famous genius of physics actually said that the one-way speed of light cannot be measured.
Many people’s outlook on life has collapsed.
Michelson looked at Li Qiwei and sighed repeatedly.
Even Millikan didn’t know what was going on.
As for the other physicists, they were almost like the students present and had no idea what was going on.
Michelson seemed to recall: "In 1849, the French physicist Fizo used the gear method to measure the speed of light more accurately for the first time."
"His experiment was very clever."
"Fizzo placed a reflector and a light emitter in two places far apart, and there is a gear in front of the light emitter."
"When the light passes through the rotating gear, It reaches the reflector and then passes through the gear. "
"As long as the speed of the gear is appropriate, the light will be blocked by the teeth of the gear after returning through the reflector. "
"At this time, the observer cannot see the light."
"Then the speed of light can be easily calculated by using the gear's rotational speed, number of teeth, and the distance traveled by the light."
" The speed of light measured by Fizo is 315,000 kilometers per second."
"This is very close to the current measured accurate speed of light."
"However, you should have discovered it. , Fizzo’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 measure it, but Bruce's special theory of relativity makes it impossible for us to measure it in principle."
< br>"Bruce is all to blame for all this."
Michelson thought he had made it 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 the one-way speed of light be measured?"
Li Qiwei smiled slightly.
(End of this chapter)