Europe is spending 21 billion euros to build a new large collider. Will my country follow suit?

Latest update time：2020-08-08

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In "The Three-Body Problem", the sophon that locked down basic science for humanity is truly impressive.

When the Trisolarans learned that humans existed on Earth four light years away, they were both happy and scared. They were happy because human civilization was far inferior to the Trisolaran civilization, but they were scared because human civilization was evolving very quickly. If the Trisolarans used their fastest spacecraft at the time to reach Earth, it would take them four hundred years, and by the time they really got there, they might have been crushed by the technological level of humans.

So, they launched a preemptive attack by sending two proton computers at the speed of light to the earth first to cause damage secretly. But what bad things can two particles smaller than atoms do?

In addition to spying on the public intelligence of the earthlings, they also disrupted the particle physics research of human beings, affected the most cutting-edge particle acceleration collision experiments of human beings, created wrong experimental results, drove a group of the smartest physicists of human beings crazy, and finally locked the development of basic science of human beings. If human beings cannot discover new laws of physics at the microscopic level, there will be no higher level of science and technology, and naturally they will never be able to challenge the Trisolarans.

Is it terrifying to think about it this way? We have to ask, is our physics now locked up by the Trisolarans' sophons?

Not really, but basic physics seems to be "locked" by high R&D costs, because the cost of building such high-energy physics experimental machines is really a bit high.

On June 19 this year, the European Organization for Nuclear Research (CERN) unanimously passed the "European Particle Physics Strategy 2020" and planned to build a new high-energy physics experimental machine - the Future Circular Collider (FCC) to study the Higgs boson (the "God particle") and high-energy frontier exploration.

However, the construction cost of this 100-kilometer-long FCC circular collider is estimated to be 21 billion euros. The plan was able to pass thanks to the success of its predecessor, the Large Hadron Collider (LHC). This collider, which cost 5 billion Swiss francs and took 25 years to build and is 27 kilometers long, finally confirmed the existence of the Higgs boson in 2012, confirming a physics conjecture proposed 50 years ago.

It was this successful experiment that gave CERN great confidence, leading it to plan to build a super-large circular collider spanning Switzerland and France, with an area 13 times larger and a circumference 3.7 times larger, to discover deeper fundamental particles, such as the predicted supersymmetric particles, and thus verify those supersymmetric theories that can explain dark matter and dark energy.

Is it worthwhile to use such a large amount of resources to verify a physics hypothesis? In China, there is also a heated debate about whether to build the "Circular Electron Positron Collider-Large Proton Collider (CEPC-SPPC)".

So, what is the purpose of this large particle collider that Europe is going to build? Since Europe is already leading, is it necessary for my country to build a large particle collider?

Why build a large particle collider?

Particle colliders are the most important experimental equipment in modern high-energy physics research. If humans want to understand the microscopic level of the universe, that is, to understand the basic composition of cosmic matter and the basic laws of natural operation, they not only need to propose a series of scientific hypotheses, but also conduct physical experiments that can confirm or falsify these hypotheses. In this case, particle colliders are indispensable verification and measurement tools.

So how does a particle collider work? Just as we want to understand the internal structure of an object, we take it apart to have a look, physicists also use the same idea when dealing with microscopic particles. However, it is very difficult to break apart elementary particles smaller than atoms, so scientists have come up with the idea of accelerating elementary particles and then letting them collide head-on. Only by colliding at speeds close to the speed of light and releasing the greatest energy can these particles be broken apart, and then humans can observe the more basic composition and various physical properties of particles.

(LHC lead ion collision experiment produced a large amount of new substances)

How to make two such tiny particles collide is a very complicated process. The only way that can be thought of is to accelerate hundreds of millions of particles at the same time. In the end, in a storm of particles, only a few lucky pairs of particles can collide head-on. What humans have to do is to measure the traces left by the particle collision in a flash (it is impossible to directly observe particle collisions), which also places extremely strict engineering requirements on particle colliders.

So, how did people find the Higgs boson in the LHC collider in 2012? Because the decay period of this God particle is only a short 10 to the negative 22th power of seconds, the detector cannot directly capture the God particle. Therefore, the signal recorded by the particle detector comes from the decay product of the God particle, that is, a pair of stable positive and negative electrons and positive and negative muons with a long life span. It is by measuring the correlation between these decayed particles that people indirectly deduce the existence of the God particle.

(Higgs boson)

What is the significance of discovering the "Higgs boson"? In the 1960s, scientists proposed the "standard model" of particle physics, which is a theory that describes the three fundamental forces of strong force, weak force and electromagnetic force and the fundamental particles that make up all matter. In this theory, the Higgs boson is considered to be the "source of mass". Other particles can only generate mass by interacting with the Higgs boson.

Therefore, the discovery of the "Higgs boson" has become the last piece of the puzzle to complete the "Standard Model". Since the puzzle of the "Standard Model" is complete, why do humans still need a larger-scale particle collider?

One is that scientists hope to conduct more in-depth research on the Higgs boson, but even if the LHC is continuously upgraded, that is, the energy level of the collision is increased, it is impossible to obtain enough Higgs bosons, so a larger collider device needs to be built.

Another thing is that the "standard model" cannot fully explain all the laws of physics. For example, it cannot explain the mass of neutrinos, the origin of dark matter and dark energy, the imbalance of matter and antimatter, and the grand unified theory that integrates the four forces. The feast of particle physics has just begun, and larger particle collision experiments are needed to verify it.

(European Particle Physics Strategy 2020)

Therefore, CERN is determined to make the study of the Higgs boson and the construction of a higher-energy particle collider "the highest priority in the future." So, what are the pros and cons of this huge scientific project in China?

Top-level confrontation in high-energy physics:

Should we build CEPC?

Currently, there are three "Higgs factory" projects being planned around the world, which are capable of producing more Higgs bosons and measuring them with extremely high precision. The three projects are the Circular Electron Positron Collider-Large Proton Collider (CEPC-SPPC) proposed by Chinese physicists in September 2012, the International Linear Collider (ILC) that Japan is actively pursuing, and the Future Circular Collider (FCC) planned by CERN.

The CEPC-SPPC project proposed by my country in September 2012 is divided into two steps. The first phase is CEPC, which can be used as a Higgs factory; the second phase is SPPC, which will build a high-energy proton collider. The FCC roadmap determined by the European particle physics strategy proposed by CERN is actually highly consistent with our CEPC-SPPC concept. The total investment of FCC is 21 billion euros, while our investment scale is expected to be about 40 billion yuan for the first phase of the project, and the construction time is planned to be between 2022 and 2030; the second phase of the project cost is 100 billion yuan, and its investment scale is much smaller than CERN's investment plan, and the construction time is between 2040 and 2050.

(Guizhou Pingtang 500-meter Aperture Spherical Radio Telescope)

But in any case, the cost of the CEPC-SPPC large collider project is two orders of magnitude higher than that of existing large scientific projects. For example, the Five Hundred Meter Aperture Spherical Radio Telescope (FAST) in Pingtang, Guizhou, cost only 667 million yuan. The Jiangmen Neutrino Experiment is under construction with an estimated investment of 2 billion yuan.

Although this research and development cost is spent in batches over decades, it is still a huge sum for my country's current scientific research funding. On whether to support the construction of the CEPC-SPPC large collider project, my country's scientific community is also divided into two clear-cut factions.

In 2016, in response to the viewpoint of "China building a high-energy collider" proposed by the famous mathematician Qiu Chengtong, the well-known Chinese physicist Mr. Yang Zhenning published an article stating that "China should not build a super collider today", becoming an authoritative representative who publicly opposed the construction of a large collider. The reasons given by Mr. Yang are as follows:

Firstly, the construction of a large collider and its subsequent detection projects are extremely costly and may be a "bottomless pit". The interruption of the Large Superconducting Collider (SSC) in the United States, which wasted $3 billion, is a lesson for us. Secondly, China is still a developing country and more financial funds should be invested in people's livelihood. Thirdly, it will inevitably squeeze other basic scientific research funds. Fourthly, the results of high-energy physics will have no practical benefits for human life in the short term.

There are also objections from the academic perspective. Mr. Yang Zhenning believes that it is impossible for physicists to discover "supersymmetric particles" through large colliders. In addition, since my country's contribution to high-energy physics is not high and its achievements are not great, 90% of the operation and analysis of large colliders after construction will be led by foreign experts. Finally, he also proposed a new approach to high-energy physics research, such as studying new accelerator principles and exploring basic principles from a geometric perspective.

Of course, Mr. Yang Zhenning has his own basis and reason for his consideration. But Professor Wang Yifang, Director of the Institute of High Energy Physics of the Chinese Academy of Sciences, who also supports the construction of a large collider, also has sufficient reasons:

First of all, there is a lot of successful experience in building the first phase of the CEPC project, and the budget is controllable. The interruption of the SSC in the United States caused the United States to lose the opportunity to discover the Higgs boson and lose its international leadership in the field of high-energy physics. Although there is no successful precedent for the second phase of the proton accelerator, we have enough time to develop and research it. If it is not started before it is mature, it cannot be called a "bottomless pit" investment. my country already has a lot of experience in building large-scale scientific projects, and it has been able to control the project cost very well.

Secondly, basic scientific research does not conflict with people's livelihood construction. Building a large collider can enable my country to take the lead in the world in basic science and high-tech fields, cultivate a large number of scientific research talents, and form a technological spillover effect in other high-tech fields.

Third, my country's basic scientific research funding is still far lower than that of developed countries. The cost of building a large collider can be raised from the increase in basic scientific research funding, and 90% of the investment in building an accelerator will be used to purchase domestic equipment.

Fourth, the view that high-energy physics is not good for human life needs to be discussed. The direct benefits of basic research may not be great, but the synchrotron radiation source, free electron laser and spallation neutron source derived from high-energy physics are of great help to the fields of biomedicine, materials, environmental science, etc. The World Wide Web (Internet) we use now is a communication tool produced by the European Organization for Nuclear Research in large-scale collaboration. The newly built large collider accelerator will achieve major breakthroughs in the cultivation of basic scientific talents, high-temperature superconducting materials, superconducting magnets and other applied technologies.

In addition, whether the new large collider can discover the "supersymmetric particles" hypothesized in high-energy physics is not the only goal of this project. CEPC can improve the measurement accuracy of the Higgs particle to about 1%, which can confirm the properties of the Higgs particle and determine whether it is completely consistent with the predictions of the standard model. CEPC is also expected to measure the self-coupling of the Higgs particle for the first time and determine the form of vacuum phase transition involving the Higgs field, which is of great significance to the early evolution of the universe.

As for whether the Chinese can lead the subsequent experiments and analysis of the collider, we need to take the initiative to cultivate more talents starting from the construction of a large collider, so that we can have a greater voice. As for whether to build such a large accelerator, Professor Wang believes that theoretical physics research is important, but experimental physics means are even more indispensable.

So, should we build this "hugely expensive, potentially unsuccessful, or potentially glorious" project? Different people have different opinions. Now CERN has given a clear answer, betting all its efforts on the construction of the Large Hadron Collider. So, as latecomers, should we follow suit?

To build or not to build, a choice that may determine the fate of the country

Not long ago, it was reported online that Dushan County, a poor county in southwest Guizhou, had a local debt of 40 billion yuan, and what was left behind were a series of unfinished image projects. The official report stated that the vast majority of the funds raised by the government were used for the construction of infrastructure, poverty alleviation, and livelihood projects, and played a good role.

We don’t know what role these have played. But the 40 billion debt still surprised people. But 40 billion is exactly the investment amount for the construction of the first phase of the CEPC project.

Although there is no particularly direct comparability, instead of spending huge amounts of money on large-scale infrastructure, it is better to increase the scale and proportion of basic scientific research expenses and invest in the Large Hadron Collider CEPC project.

Moreover, we have successful experience. In the 1980s, when China's economic situation was far worse than it is now, we successfully built the Beijing Electron-Positron Collider, trained a generation of high-energy physics talents, and achieved good scientific results in the field of τ-charm physics. However, there is still a clear gap with the cutting-edge fields.

(European Large Hadron Collider)

Now, facing this new window of upgrading in the field of high-energy physics, my country has the first opportunity to compete with Europe, the United States, Japan and other countries. If we miss this opportunity, there may be no chance for China at the high-energy physics table in the future.

If China and the United States' research in basic science is also affected by more political disputes in the future, my country's basic scientific research will be in a more passive situation.

From a realistic perspective, my country already has the financial strength and technical foundation to build such a large-scale scientific project. Moreover, the huge investment will in turn promote the upgrading of my country's domestically produced high-precision instruments, basic materials, processing equipment and other technologies. Large projects will promote the localization rate of these technologies. At the same time, it can also make my country a research center for high-energy physics, attract the world's top intellectual resources to settle in China and visit for a long time, build a leading scientific research center in China, and cultivate a larger scale of basic scientific research talents.

Of course, among so many major scientific research projects in the country, which one to support and which not to support involves the game among numerous research institutions and the allocation of scientific research resources. The country needs to make careful considerations and provide different stages and levels of support for the development of different scientific research projects according to their importance.

The Large Collider also needs to be given a chance to be approved for construction in a fair competition with other scientific research projects. This is the important reason for us to start this huge scientific project immediately.

From a long-term perspective, the development of a large collider is still the only way for my country to achieve breakthroughs in the field of high-energy physics. The investment in basic scientific research is not only a question of input-output ratio and whether it will benefit at present, but also a question of the future development of a country.

Persistent investment in basic scientific research may not produce actual results in improving people's livelihood and promoting economic development in the short term, but it will bring new technologies and methods that can enable sustainable development and even breakthroughs to a country and even the world in the future.

In 1970, Zambian nun Mary Jucunda wrote a letter to Ernst Stuhlinger, deputy director of science at NASA's Marshall Space Flight Center, asking: How can you afford to spend billions of dollars on the Mars project when there are so many children on Earth who don't have enough food to eat?

Stuhlinger replied in a letter titled "Why Explore the Universe?" He said: The voyage to Mars cannot directly provide food to solve the problem of famine. However, it brings a lot of new technologies and methods that can be used outside the Mars project, which will generate benefits several times the original cost. And this is exactly the case. Every breakthrough in basic science brings many unexpected practical technologies and major inventions to real life.

Whether it is the FCC project newly supported by CERN or the CEPC project that Chinese scientists are striving for, although they will encounter various difficulties and doubts during the implementation process, we should not deny scientists' curiosity and enthusiasm for exploration in the science of elementary particles in the universe, nor should we discredit these scientific research investments from the perspective of "conspiracy theory" or "selfishness theory."

In human history, if there is an innovative undertaking, if we choose not to do it, we may not know what we have missed, but if we bravely choose to do it, even though there is a possibility of failure in the future, we will know what we may have missed, and we will also know what we have gained.

What deserves our serious attention is that in the field of high-energy physics, if we lose the priority in discovering new theories, we may never miss the entire future of physics, and China will no longer have any say.

Compared with those image projects that cost huge amounts of money to build, shouldn’t we think of ways to build a major scientific project of the future that will make our countrymen proud and attract foreign countries to come?

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