Faced with the dean's subconscious question, Gu joked.

Why make an atomic fountain that can easily reset two sets of initial harmonics?

He was happy to answer this question without much effort and pretending:

"Because this type of cesium atomic clock, when it was first put into commercial use, it was to be used in two categories. One will be placed in a terrestrial space center, such as NASA headquarters in Houston, and the other will be launched into orbit with GPS satellites.

According to Einstein's special theory of relativity in its simplest form, the faster an object moves, the slower its passage of time becomes. The orbit of the GPS satellite is 19,000 kilometers above the earth, so the orbital speed is much lower than the first cosmic speed, only about 3.9 kilometers per second.

At mid- and low-latitude temperatures, such as Houston in the oceanic nation of Texas, the Earth's linear rotation velocity is less than 400 meters per second. (It can exceed 460 meters at the equator, because there is the largest radius of rotation of the Earth)

The difference between the orbital speed of GPS satellites and the speed of terrestrial space centers following the Earth's rotation line is about 3.5 kilometers, which is equivalent to 1.17 ths of a hundred thousand speeds of light.

So, we roughly estimate that the passage of time on GPS satellites is roughly more than 100 microseconds slower per day than that of ground-based space centers.

Of course, this result only calculates the effect of velocity on time in special relativity, not the distortion of time by gravity under general relativity. This calculation process is a bit more complicated, you can see what I wrote in the material.

In the end, the gravitational-time warp should be slightly larger than the velocity-time warp, which can cancel out most of it, but there is still an accumulation of errors of 20~30 microseconds per day.

Therefore, if you do not fine-tune the difference between the preset harmonic frequencies of the two fountains of heaven and earth at the atomic fountain level of the atomic clock, then you will have to use more troublesome methods and add external mechanisms to calibrate the back-end communication.

According to my calculations, if the ground static cesium atomic clock uses a standard harmonic frequency of 9,192,631,770 times. For those atomic clocks on satellites, the harmonic speed of the fountain should be reduced to about 9,191.5 million times, which can roughly solve this problem naturally. ”

(Note: The above calculation uses the intrinsic time-gravitational field gauge equation under general relativity, but the website does not support the display of such a complex formula, so it cannot be typed.) If you are interested, you can check the relevant physics monographs by yourself.

In fact, I originally planned to pick up the college physics textbook and calculate it myself, but later found that it had been more than ten years since graduation, and my ability to do questions had decreased seriously, which was a waste of time, so I found a data on the Internet. Hardcore book friends, don't raise the bar, the principle must be right, but I didn't calculate the calculation process myself. ）

As soon as Gu Wan finished speaking, Dean Ding had a sense of remorse for "such a simple truth, why didn't others think of it".

It's like the remorse of those leaders who can't help but want to break their thighs after their teams lose because of low-level mistakes.

Einstein's theory of relativity, Dean Ding, of course, is too familiar to be cooked, and it belongs to the kind of familiarity that can be solved when he is asleep. For Dean Ding, that's the level of babies and children in the nursery.

However, it is not easy to combine such a simple truth with the engineering application of atomic state control and aerospace.

This has moved from nursery school babies to the level of math problems in the third grade of primary school.

Dean Ding roughly knew that Gu Wan was right, but he didn't understand aerospace satellite engineering, nor did he understand GPS and atomic clock accuracy, so he asked casually:

"How important is this amount of error?"

Gu Yu thought about it for a while and decided to explain it in the most popular way: "Let's put it this way, upgrading the rubidium atomic clock to the cesium atomic clock, the improved accuracy is less than 30 microseconds per day." Therefore, if you ignore the relativistic time error of navigation satellites, it is equivalent to wasting the accuracy improved by upgrading a generation of atomic clocks, or even more.

In terms of ranging accuracy, at least a few kilometers of positioning errors can be accumulated every day. If you use a navigation satellite that doesn't take into account the relativistic time-lapse speed error, you are in the school by Xuanwu Lake, and the positioning result may determine that you are in the Confucius Temple. ”

This is very vivid, and it directly amused Dean Ding, who has been in Jindu for more than ten years.

People are in Xuanwu Lake, and they are located in the Confucius Temple, and the broken satellite must not be usable.

Any small error in physical quantities, once multiplied by the "speed of light", will be magnified and exaggerated to the point that it cannot be ignored.

Dean Ding sighed, and finally confirmed: "Then how can you guarantee that the people of Tunghai University really didn't expect this?

Gu Play thinks it's appropriate.

Because historically, the Americans on Earth, when they first launched a GPS test star, did not expect it.

There is a lack of communication between the research department of atomic clocks and the research department of navigation satellites.

Anything that seems easy, when all mankind does it for the first time, there will be a lot of simple coupling across circles, which is unthinkable.

This is the history that really happened on Earth.

Of course, this problem did not cause much serious consequences later, because after the Americans discovered it, the subsequent mass-produced satellites were adjusted, and a mechanism of frequent timing was added, which was nothing more than a little more complicated.

However, since Gu Play can do it all over again, this is his chance to pick up the leaks and make things more concise.

It's just that the "historical knowledge" part of this, Gu Wan can't directly tell Dean Ding.

He could only make a roundabout statement: "I know, Yuan Xiong hasn't thought of this yet, because his research and development hasn't done it yet." Moreover, he only cares about the atomic clock, and does not care about the coupling of GPS as a whole system engineering.

Even if there is a problem, he must feel that this should be delivered in February next year. Moreover, as I said, Yuan Xiong's feasibility report and project approval documents were actually induced under my influence. I know he didn't think of anything. ”

In February next year, it will be the deadline for the delivery of the cesium atomic clock for international cooperation and the final pre-launch coupling with the satellite.

The GPS No. 2 test satellite will not be officially launched until the summer of next year. At that point in time, you can't change it, and all countries in the world are watching.

Hearing this, Dean Ding couldn't help but take a deep breath.

Gu Play's thoughtfulness made him have to admit: this kid has two brushes.

You say how in-depth he studied each course, but it doesn't necessarily matter.

But it's a good cross-circle association and a high-level vision.

This is God's appreciation for food, and he can't envy it.

Dean Ding sincerely sighed: "Classmate Gu, I won't be wrong. In the future, you may not be able to have much first-line scientific research expertise, but your ability to integrate scientific research resources and coordinate systematic scientific research projects will not be bad. In time, maybe you can become Dornberg or von Braun, but the future is terrifying. ”

"Then you are also using the laboratory resources of this university to do the research and development of the sub-project of 'Atomic Fountain'?" Gu Yu was waiting for this moment.

Dean Ding: "In principle, it can be discussed at the meeting. However, in that case, if you can apply for public funding, the research results will belong to the school. Looking at your posture, do you want to introduce social capital and commission R&D?"

If you go for state-funded scientific research, the process must be complicated.

However, if the source of funds is obtained, the investor rents the school's instruments and equipment at the market price, and pays research allowances to scientific researchers (in fact, the second salary, and bonuses), and it is clearly stated in the contract.

Then, the process will be much simpler, and the business value of the future results will be clear.

Gu Yu said gratefully: "I have a way to find money, and even, I can directly find a way to cut out a part of the budget from the projects that Tunghai University has already gotten - because Tunghai University, after not having to do the sub-project of 'Atomic Fountain', it should not have been able to use the budget of 20 million US dollars, and their workload has also been reduced."

However, this may require us to occupy the high point of technical demonstration first, such as demonstrating their current practices and technical routes, and the atomic fountain made may not be able to achieve the optimal effect, so as to give an explanation to the competent science and technology commission and the employer. ”

Dean Ding shook his head: "Things can't be as simple as you think, and in that case, in the final analysis, the venture capital fund will make all the money, and the left hand will be the right hand, so it is better to let the country earn it."

However, I will arrange the prelude to the technical demonstration. Your related papers, which should be made public, should be published, such as the calculation of the time difference calibration problem caused by the motion of GPS satellites and gravity, will be published in our "Journal of Oriental Physics". ”

The Journal of Oriental Physics is a journal jointly organized by the Chinese Academy of Sciences and the Central University of Science and Technology, which is roughly equivalent to the Chinese Journal of Physics on the earth.

However, because the Central University of Science and Technology on the Blue Hole Star is much stronger than the NTU on the earth, the "Oriental Physics Sinica" is also the first physics journal in China, with an impact factor of about 5 or more, which is already very top in China.

There are not no scientific journals with an impact factor of more than 10 in China, but those are often more subdivided and specialize in a certain subdivision direction.

The first-level discipline journal, which is held back by the shortcomings on average, can have an impact factor of 5, which is definitely awesome.

After Gu Play's idea was announced, Tunghai University could certainly copy it.

But Gu Wan is not afraid of copying, because if the other party makes a temporary argument, it may be too late in time.

More importantly, Dean Ding reminded him: even if there is time, as long as the investor has the confidence to believe that he is too late, the investor will have an excuse to withdraw a sub-project and forcibly match, requiring Tunghai University to hand over this sub-sub-project, and then give it to the Central University of Science and Technology, and finally the two sides will jointly develop and subcontract each other.

Just like the developer, after the general contract of the project, halfway through the construction, it was found that the contractor did not have the strength to finish it alone, so the two, three, four, five and six packages were subcontracted layer by layer, which is a reason.

It's just that it is illegal to subcontract privately, but if the employer holds a meeting, or even the employer feels that it should be subcontracted, and the process is complete, then there is no problem at all.

"Then I'm going to prepare my thesis...... Is it time to publish it in the issue after the National Day?"

"I'll help you say hello to Gasai, what's too late?" Dean Ding couldn't help but feel a little bit of tiger power when he said this.

——

PS: Yesterday it was 400 live fans, thank you for your support, today as promised will be added, more than 4 o'clock in the afternoon, before 5 o'clock, there will be a third change.