Deep Space Fleet

I feel that the recent writing is not very good, and I don’t have much passion. It’s the last day of the May Day holiday. Let’s take a day off and update normally tomorrow.

After all, the author is not Zhang Yuan, who can explode his liver all day long without knowing that he is tired, and needs a normal rest... (I also seem to be him, QAQ)

Finally, here is another popular science article, an article written by an academician, I feel pretty good, you can read it if you are interested.

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Opinions on China's construction of a large collider

He Zuoxiu, Researcher, Institute of Theoretical Physics, Chinese Academy of Sciences, Academician of Chinese Academy of Sciences

Author|He Zuoxiu (researcher at Institute of Theoretical Physics, Chinese Academy of Sciences, academician of Chinese Academy of Sciences)

Editor in charge | Lu Haoran

1

The CEPC-SPPC project proposed by Wang Yifang, director of the Institute of High Energy Physics, Chinese Academy of Sciences, and others is not an innovative project. The overall design idea is borrowed from the LHC and enlarged, and the project funding is also very large. The SSC project in the United States has a planned energy of 20TeV; Italy, that is, Europe, once had a larger Eliosatron project than the SSC in the United States, with a higher planned energy. The energy of the SPPC proposed by Wang Yifang is 70-100TeV, which is actually similar to that of Eliosatron, and the latter died without discussion in many countries, that is, it was opposed by many high-energy physicists in Europe.

The United States launched a fierce debate for the SSC, and finally the dispute reached the Congress, which was voted by Congress and finally rejected. Some people say that this is a victim of political debate between the two parties, no! Regarding the decision-making of the SSC project, the person in charge of the finance of the country believes that this project does not have much scientific value, and the cost is huge, which will affect the country's development ability, so it is finally abandoned. Of course, many high-energy physicists expressed their support, but there were also many high-energy physicists who insisted on opposing it, thinking it was a waste! In the end, Congress adopted the opinion of the opposing party and voted to reject it.

It should also be noted that the thoroughness of the US "veto" is astonishing! The U.S. government has invested 2 billion US dollars, mainly to dig a large tunnel, and the cost of the tunnel accounts for about 10% of the total cost in the plan. Later, an additional US$15-20 billion was requested for the final realization.

But the result is that Congress would rather sacrifice the $2 billion that should have been invested, and no longer allow such unproductive investment. After Congress vetoed it, even the excavated tunnels were filled in to prevent "resurrection".

2

Why did the U.S. Congress question the opinions of many experts, and finally rejected the SSC project after a big debate in Congress? There is another important academic reason: there is an important theory in the theory of particle physics, that is, particle physics will develop to ultra-high energy physics, and there will be no new discoveries. This is called the "big desert" of high-energy physics. "theory.

The "Great Desert" theory believes that only when the energy is increased to the Planck scale, that is, the energy equivalent to 10^16TeV, can new discoveries be made in high-energy physics. Later, some high-energy physicists believed that this theory was not completely correct and should be revised. The correct way is to introduce the concept of "supersymmetry", and think that with these supersymmetric particles, the energy scale will be reduced by many orders of magnitude, but it is still much higher than the order proposed by SPPC! Later, several accelerators in the United States and Europe tried to discover these supersymmetric particles, but found nothing. This also illustrates the rationality of the "Great Desert" theory from the side. Therefore, the US Congress voted overwhelmingly to veto the continued construction of the SSC project.

Of course, the "disappearance" of supersymmetric particles immediately led to a major change in fundamental views, that is, the "collapse" of the superstring theory elaborately crafted by many particle physicists and mathematicians! The so-called "collapse" here is aimed at the theory that superstring theory is meaningless in physics. However, it is not ruled out that it has a certain significance in mathematics.

However, there are still quite a few theoretical physicists working on superstring theory and supersymmetric particles who do not think that supersymmetry is dead, and are still insisting. However, few people believe that this is a promising theory in particle physics, and have announced that they will "change their careers" and not do it. For example, Professor Li Miao from the Institute of Theoretical Physics who has made great contributions to superstring theory has now given up. In other words, superstring theory is no longer the mainstream of high-energy and particle science!

3

Combining the above two arguments, I can only think that the CEPC-SPPC program proposed by Director Wang Yifang is just an "innovation" that has been completely abandoned by the US Congress, but at this time it has been brought over by many scientists to the Chinese government. sell.

As for whether the Chinese government is willing to pay huge sums of money for construction, it depends on how the Chinese government evaluates this matter.

We should also note that many of the people promoting the collider project are American experts such as academicians of the National Academy of Sciences. They said that this plan has "many benefits." Of course, since China's high-energy physics research is far less advanced and developed than that of the United States, it may be that people like us are "short-sighted" and have no scientific foresight. However, there is still a question that I can't understand: why is such a good solution not accepted by the American scientific and technological community? Why is such a good plan not insisting on continuing to lobby the US government? If the U.S. government announces that it will launch this "innovative" plan, and hopes that China will also provide a large amount of funds to join the cooperation, I believe that it will definitely get the full support of many scientists in the field of high-energy physics in our country!

4

One answer to our question is: this scheme still has far-reaching significance for the research of high energy physics in developing countries, such as China. I cannot agree with this. We have always agreed with the saying "Science has no borders, scientists have a motherland", and we cannot agree to a plan that has no significance to world science, but will have "great significance" to the motherland of Chinese scientists. There are too many scientific problems to be solved in contemporary China, and many, many young people are required to participate in this work. But just because some people in China or other countries in the world have already entered the high-energy physics field, but there is a lack of jobs, we should not conceive a plan that is not very "effective" to accommodate these high-energy physicists!

The world is a whole. The economic and scientific development of the countries in the contemporary world must take the road of "integration" and "globalization". Recently, I have been engaged in the study and research of economics and political economy in my spare time. Many conclusions of economics should also be applicable to the development of science in the world.

We know that there is a law of diminishing marginal utility in economics, which can be applied to a wide range. For example, why did my country's economy change from an average increase of 10% earlier to 6.9% today? The simplest explanation is diminishing marginal utility. The way to mitigate this impact is to rely on innovation. These basic principles must also be applicable to the research of high energy physics.

From the proposal of Wang Yifang and others, the feature of this proposal is that there is no revolutionary technological innovation at all, and it only develops towards "super-large", so it must be applicable to the law of diminishing marginal utility.

There is a technical difficulty in applying the law of diminishing marginal utility, that is, it is difficult to judge at what speed the "marginal utility" will "decrease", and how much will its "margin", that is, the "slope" "decrease" in the future? In fact, recent experiments at the LHC have given a verdict.

In the previous period, LHC discovered a "resonant peak" of 750GeV in the energy range of 700-800GeV. The academic circle is very excited, because it seems that there may still be new discoveries in high-energy physics, and the "Great Desert" theory does not match the reality! However, due to the insufficient number of experiments, it cannot be clearly considered that this is a new particle. Therefore, some people advocate investing more operating time and costs in order to fish out this "new particle". There are also a large number of theorists who believe that this is a new thing, and have made many "new" theories to explain this particle, and made various new predictions.

However, most theoretical physicists who insist on believing in the "Great Desert" theory still believe that this so-called "new particle" should be a statistical fluctuation, not a new particle.

As a result, further high-precision experiments showed that the existence of the "new particle" was not confirmed! The "Great Desert" theory is still correct in this energy region. It should be noted that the energy of 750GeV is actually 6 times that of the 125GeV of the Higgs particle known as the "God Particle", but the result is still zero. If interpreted in terms of economics, this experiment has shown that the "marginal utility" of the high-energy collider has been reduced to "zero" in the energy region of the LHC.

Now, in the scheme proposed by Wang Yifang, the maximum energy is only 7 times that of LHC. And if we continue to follow this trend, how can we ensure that new particles or other major new things will be discovered again? Not only that, but the Geneva center is about to further increase the energy to 20TeV and continue to engage in experimental work. But Geneva already has a very large accelerator, and the west only needs to reinvest some money to achieve marginal benefits. However, China wants to restart the stove, which is only to increase the energy by 7 times, but it has to repeat the long journey that the LHC in Geneva has gone through.

In other words, the proposal of Wang Yifang and others is by no means an equal competitor of Geneva.

The LHC at the Geneva Center has made great contributions to high-energy physics. It has been in operation for 20 years and has discovered four important particles, and it has almost completely proved the correctness of the "Standard Model". Now there is only one small problem left, that is, whether the lepton number is "absolutely" conserved, which has not been completely resolved. However, the answer to this question does not require ultra-high-energy accelerators, but low- and medium-energy accelerators, such as the spallation neutron source and ADS projects that have been established by the Academy of Sciences.

It can be said that the current development trend of high energy physics fully corresponds to the repeatedly emphasized supply curve, and will extend to the "right" according to the "S" character. But at this time, there are already "Great Desert" theory and LHC experimental results, all of which show that the "marginal utility" of this extension is roughly close to zero, that is, the "S" shaped curve is close to the "top point". ".

So, why is it necessary for China today to invest heavily in this CEPC-SPPC, which is difficult to produce significant results?

5

Of course, Director Wang Yifang has always emphasized that the high energy institute never exceeded the budget when building the electron-positron collider, and the fluctuation range will not exceed 5%. It should be said that this is a historical fact. But as a witness of the Beijing Electron Positron Collider, I want to tell some stories behind it.

The electron-positron collider built by High Energy Institute is a large-scale basic research project launched by Comrade Mao Zedong in accordance with Premier Zhou's last wish after the "Cultural Revolution", with a total cost of 220 million yuan. Since this is the first large-scale scientific research project specially approved by the central government after the reform and opening up, the central government has come forward to say hello to all parties: this is not a piece of "Tang monk meat", and the ministries and commissions should not take the opportunity to "take a bite". This "greeting" also spread to Hong Kong, which had not yet returned to China at that time. The industry in Hong Kong said that this is a project specially approved by Comrade Xiaoping, and we will definitely support it vigorously. Even if it does not make money, we will try our best to ensure the supply.

In order to ensure that the positron-electron collider was carried out as planned, the central government also dispatched Comrade Gu Yu, the wife of Chairman Hu Qiaomu, to preside over this work. When encountering difficulties, Comrade Gu Yu will coordinate from them. To give an example, when the construction of the electron-positron collider started, nearby residents were concerned about radioactive pollution and expressed their opposition. The environmental protection department sent a department-level cadre to participate in the supervision. But that cadre lacked professional knowledge reserves, and just blindly expressed opposition.

We asked her to come up with a corresponding "indicator", what kind of standard should be reached to pass, but she couldn't give a specific value. At that time, the leader of the Institute of High Energy entrusted me to organize some young comrades to design the protective device of the high-energy accelerator. Since the cadre sent by the environmental protection department was really "a layman", he could not give a specific index, and of course we also suspected that she had "gnawed". A bite" means.

Therefore, Comrade Gu Yu went to Comrade Xiaoping to report the situation, and finally Comrade Xiaoping decided that we would be responsible.

Of course, our designs were quickly completed. Because this collider is an electron-positron collider, it only emits X-rays and γ-rays, and its impact on the environment is smaller than the cosmic ray background.

The question is, in the current era, can the "wishful thinking" of director Wang Yifang be realized again? The conclusion should be: this is a plan that does not suit China's national conditions, and policymakers should not support it.

6

Director Wang Yifang also said that the opponents are almost all experts outside the field of high-energy physics. I don't think this is true.

We also have a group of members of the High Energy Physics Society here (Institute of Theoretical Physics), and many of them expressed their opposition. In fact, there are also some different opinions within the Institute of High Energy Energy, but they are embarrassed to express it publicly due to the feelings of colleagues.

Before Professor Yang Zhenning published an article opposing China's construction of a large collider, some people also pointed out that Mr. Yang has not been in the front line of physics for many years and has deviated from the mainstream of physics. These doubts are not correct. Although Professor Yang is old and has not been in the front line for many years, Mr. Yang's views on theoretical physics cannot be said to be outdated or deviate from the mainstream. From a historical point of view, Mr. Yang's views on the future of physics Nor can judgment be said to be trivial.

Recently, Director Wang Yifang pointed out that almost all high-energy experimental physicists are in favor of China's construction of a large-scale collider project, and the opponents are all theoretical physicists. Some doubts were raised about the opponents' majors, including Professor Yang Zhenning Not an experimental physicist either.

Well, then I will also list a scholar who can definitely be called a high-energy physics experimenter in the world, and is also the teacher of Wang Yifang's director-Professor Ding Zhaozhong. Professor Ding once asked me what kind of research Wang Yifang is currently engaged in. I replied that he is still measuring neutrino oscillations in Daya Bay. In addition, he is studying some new schemes. Professor Ding asked what is the new plan? I said that he wanted to move the similar plan of SSC discussed in the United States to China. Professor Ding immediately said, why do you want to do this? It doesn't make any sense at all!

Sorry, I made Professor Ding Zhaozhong's opinion public here. But I think this is enough to prove that there are still some internationally renowned high-energy physics experimenters who do not support his plan.