Why should Newton be quoted in the first sentence today? Obviously, what I'm going to say next has something to do with Newton's law. I wonder if you have heard of EmDrive? This thing once occupied the headlines of science and technology news with the title of "Arriving on Mars in a few weeks". Why? Because it's amazing, it doesn't matter if you haven't heard it. Let's talk about what EmDrive is first! Then review a scientific farce in the history of science, and then reflect on EmDrive.
What is EmDrive? Why did it violate our fundamental theorem?
EmDrive is full name of electromagnetic drive. From the name, this propeller does not need liquid or solid fuel in the traditional sense, but uses electricity!
EmDrive prototype
This kind of propeller has a special microwave cavity, which relies on the power provided by solar energy to maintain the microwave energy reflected in the cavity and generate thrust outward, without any mass or energy escaping. This sentence is crucial: there is no energy escape, and we all know how rockets get thrust. They rely on powerful chemical energy to inject energy into the outside, creating high-pressure areas and low-pressure areas in the cavity to provide power! This is the same principle as releasing balloons.
At first glance, EmDrive violates the known laws of physics, Newton's third law and conservation of momentum. Newton's third law tells us that when you exert a force on an object, the object will exert an equal and opposite force on you. If two skaters have the same mass and the friction between the soles of their feet and the ice is zero, then the total momentum of their initial state is zero. If they push each other, they will get an initial momentum, but in the opposite direction, the total momentum of the system is still zero. This is our common sense in physics! EmDrive works like you can lift yourself, and you can step on each other. Then how did EmDrive, a fuel-free propeller, catch fire? Because it has been verified by some laboratories.
The concept of Emdrive was put forward by electronic engineer Roger Shawyer in 1999. By 20 16, four independent laboratories had made machines and proved to have real driving force. These include Yang Juan's team from the School of Astronautics of Northwestern Polytechnical University, and Eagleworks Laboratory of NASA, which caused a sensation in the scientific community.
What should we do when the experiment goes against the theory?
In essence, physics is an experimental science Therefore, if the experimental results are contrary to the theory we think we know, then it is the theory that needs to be explained, not the experiment. After all, practice is the standard for testing truth!
Of course, unless there are some unclear problems in the experiment, whether these problems are caused by fraud, carelessness, equipment failure or a series of other errors. There is a saying in science: unusual claims need unusual evidence! So we need to consider the following points:
When the results given by an experiment cannot be predicted or recognized by theory, we must be very vigilant to ensure that the experimental results will not go wrong.
This means that we must consider and quantify all sources of uncertainty, including statistical error (depending on how many data points there are) and systematic error (inherent error in experimental setup).
It is important and necessary to independently verify and reproduce the experimental results, which means that we have explained the experimental settings and methods in detail, and anyone else can independently obtain the experimental results with appropriate equipment through this method.
The n-ray farce in history is simply a noise!
In fact, there are many oolong experiments in science, some are equipment failures, some are human factors, and even some impure people participate in some interests, and the experiments will also have problems! I believe you have heard of the experiment of neutrino superluminal. At that time, it also caused an uproar among scientists, which directly threatened the basis of relativity, but it was later proved that it was caused by errors in experiments. In history, there is another example that you may not have heard of, which can be traced back to 100 years ago: N-ray. This is a striking and important "morbid" case in the history of science, full of factors of eagerness for success, nationalism and malicious falsification, and it is a farce in the history of science.
X-rays are familiar to us It is a kind of high-energy electromagnetic radiation, which can directly penetrate human skin and body, but cannot penetrate bones. As early as the beginning of the 20th century, many physicists experimented with different wavelengths of light to understand their behaviors and characteristics in various situations. One of the studies tried to polarize X-rays. As part of the experiment, a spark gap needs to be established. The working principle of spark gap is simple. The two electrodes are separated by a certain distance. When the voltage between the electrodes exceeds the breakdown voltage of the medium (including air) between the electrodes, sparks will be generated to jump over the gap.
Brownlow, a famous French physicist, found a very strange and unexpected result: when he put this gap into the X-ray beam, the brightness of the spark inexplicably increased. Brownlow attributed this effect to a hitherto undiscovered form of radiation called N-rays. Why n? These are all people's names, because the experiment was done at the University of Lorraine in France, and one of them was a big one in Nancy.
Above: Action photography of N-ray on small electric spark, Brown Draut 1904.
At that time, 120 scientists successfully discovered these effects. Not surprisingly, these scientists are all French scientists around Brown Draut. At that time, out of unity and national pride, and in order to compete with the British and improve France's position in the scientific community, it took subjective assumptions as objective facts and staged a fake farce. Just as the momentum of N-rays is getting bigger and bigger, scientists from other countries have joined the research, but there is no ideal experimental result!
The degree of these effects varies greatly in different experiments.
At that time, some top scientists also did experiments, including Lord Kelvin, Heinrich Rubens and robert wood, and the results were all invalid.
However, N-ray researchers (French scientists) still claimed that the results they saw were true, and presented evidence to argue the successful shooting of the brightness change of electric spark. In the end, the debate was fierce, so robert wood was entrusted by Nature to witness N-ray's demonstration in the Brown Draut Laboratory of Nancy University to see if it was true.
Robert williams Wood's photo, taken at 19 10.
What Wood saw, however, was the highest level of scientific fraud in history. Before Brown Draut Le demonstrated, Wood quietly took out a prism from the experimental device while the room was dark, and then replaced a metal file (an imaginary N-ray emitter) with a piece of wood.
However, when Damblanc Delautre demonstrated, he still claimed that N-rays were detected in the spark gap. Shortly thereafter, in September of 1904, Wood published his research results in the journal Nature. He said:
"After spending more than three hours watching various experiments, I not only can't report any observation results indicating the existence of N-rays, but also firmly believe that a few experimenters who have obtained the experimental results of N-rays are a kind of deception to some extent."
Now, let's go back to today's Emdrive (fuel-free propeller).
So what exactly did you say about EmDrive's experiment?
Team China, an English inventor and Guido Fetta made three different versions of EmDrive. It is speculated that the thrust results given by these three versions are different, with a difference of about 500 times.
The "test" equipment (torsion pendulum) conducted by NASA is very sensitive to the minimum thrust threshold of 10 to 15, and the "results" show that the detected thrust is between 30 and 50.
Finally (and most deadly), both a "true" version and an "empty" version of EmDrive were tested on the torsion pendulum. It is expected that the true version will generate thrust, but the empty version will not. But the results show that the two versions have the same effect.
Summary of the report from NASA:
"Thrust was observed on both test pieces, although one of the test pieces was originally designed without thrust. Specifically, one test item contains internal physical modifications to generate thrust, while the other does not (the latter is called an "empty" test item).
In other words, NASA also confirmed the "impossible" space drive.
EmDrive has not been confirmed by NASA; According to the National Aeronautics and Space Administration (NASA), EmDrive is no different from "empty" equipment. Later, German scientists proved that the thrust did not come from EmDrive itself, but the electromagnetic interaction between the conductor and the joint area provided a small thrust.
Although EmDrive has inevitable defects in theory, we will not call EmDrive "civil science" because of its theoretical defects. Because physics is essentially an experimental science, a good experiment can overturn or deny even the most elegant theory. But from the experimental point of view, EmDrive does have a big problem, because:
The experimental results are not reliable, because EmDrive cannot be copied exactly the same or similar by different teams. The experimental results will be biased, and no one can prove conclusively that their engine can operate as described in theory.
The result is not important because EmDrive cannot be distinguished from a setting that should give an "empty" result. This may prove that there are other unknown experimental loopholes. )
German scientists have proved that this is due to electromagnetic leakage.
Here we think of the example of N-ray, which is the nightmare of every scientist who pursues truth: false information pretends to be science and erodes the public's trust in science itself. The greatest function of science is to be able to self-test, introspection and self-correction!