Training the Heavens

Chapter 271 Gas Conductivity Experiment
The inspiration for the new experiment happened to come from Lang Zhiwan. Two days ago, he told Zhang Xingjiu that he had received an invitation from the Cavendish Laboratory of Cambridge University and was going to continue his studies under Thomson.

Zhang Xingjiu immediately thought of an important experiment that Thomson would conduct next year. It was this experiment that won Thomson the 1906 Nobel Prize in Physics.

The investment in this experiment is slightly larger than that of the blackbody radiation experiment. If Zhang Xingjiu had proposed it at the beginning, it would probably have been difficult to obtain permission. Now there is no problem. The success of the blackbody radiation experiment has earned him a certain reputation, and this reputation has also increased his voice. If a suitable experimental plan is put forward, Lippmann has no reason not to approve it.

Since Maxwell established the electromagnetic field theory, electromagnetism has ushered in great development. Many theories have been quickly transformed into industrial applications. Motors, transformers and high-voltage transmission lines have gradually been used in production, and air leakage has become a problem that needs to be solved urgently.

At the same time, electric lighting also attracted the attention of many scientists, so people competed to study the phenomenon of low-pressure gas power generation.

In 1858, when the German Pluckler was studying gas discharge, he noticed a green fluorescence on the wall of the discharge tube facing the cathode, proving that it was caused by some kind of ray emitted from the cathode and hitting the tube wall. This ray was later called cathode ray.

In 1871, British scientist Walley discovered that cathode rays would be deflected in a magnetic field, which was very similar to the behavior of charged particles; Crookes confirmed in his experiment that cathode rays not only move in a straight line, can be focused, and deflected in a magnetic field, but can also transfer energy and momentum.

Hertz noticed that cathode rays could pass through metal partitions, causing the blocked glass wall to emit a faint fluorescence. This phenomenon was later continued by his student Leonard.

Thomson at the Cavendish Laboratory had also been studying the phenomenon of gas conductivity, trying to figure out the nature of cathode rays - are they particles or waves?
When Roentgen discovered X-rays, Thomson keenly realized that this discovery might promote his research, so he began to study what X-rays could do in gas conductivity experiments and designed several ingenious experiments.

Now Zhang Xingjiu intercepted his mistake and took out his experimental plan in advance and submitted it to Lippmann for review. Lippmann was a little excited at first, but was surprised when Zhang Xingjiu took out a new blackbody radiation experimental plan. When he opened it, he couldn't help but frowned, "You have already made a breakthrough in the field of blackbody radiation. Why don't you continue along this path, but enter a new field?"

"I don't have any new inspiration for the time being, so I can only continue to use the current plan to repeat the experiments and pay attention to the research of other scholars. If I do this, my time will be wasted. It just so happens that I have some new inspiration in the field of gas conductivity. The discovery of X-rays may bring new breakthroughs to this field. This is also a relatively hot field. I think it is worth some attempts." Zhang Xingjiu explained.

By the way, he also complimented me, "I admire your achievements in the field of electricity. As your student, I also want to make breakthroughs in the field of electricity."

Lippmann once invented the capillary potentiometer. If he had applied for a patent for this invention in his own country or other countries, he would have immediately become a millionaire. However, he donated this invention to the French Physical Society.

This is also one of the most important achievements in his life. Now hearing what Zhang Xingjiu said, he naturally felt comfortable and picked up the experimental plan again and read it carefully.

Zhang Xingjiu explained on the side, "Nowadays, many scientists are arguing about whether cathode rays are particle streams or electromagnetic waves. If X-rays are used to bombard the gas, if the cathode rays are particle streams, then they will change their direction of movement when passing through electric and magnetic fields. Otherwise, they are electromagnetic waves." Lippmann saw that Zhang Xingjiu designed a special cathode ray tube to measure the deflection of cathode rays in an electrostatic field. A pair of metal plates were installed parallel to the cathode ray channel and connected to a battery pack.

Based on his professional judgment, Lippmann believed that the experimental plan was very ingeniously designed and had a very high probability of success. Looking at the experimental budget attached at the end, although it was a bit high, it was within his acceptable range.
He signed the application and said, "I'll tell Pierre to purchase the equipment you need as soon as possible. If we can't buy it, we'll modify and manufacture it ourselves. I hope you can seize this opportunity."

"Thank you very much. I am full of confidence in this experiment." Zhang Xingjiu couldn't help but sigh secretly. Fortunately, France is now in a good era and the scientific research budget of universities is very abundant. Otherwise, it may not be passed.

Pierre's ability in experimental management was unquestionable. He quickly prepared for the experiment according to Zhang Xingjiu's needs. Lang Zhiwan also came over excitedly to join in the fun. "Professor Thomson is also studying gas conductivity, so I'm just getting used to it."

Zhang Xingjiu didn't know what to say for a moment.
Soon, they conducted their first experiment, and the results showed that the cathode rays were not deflected at all. Lang Zhiwan believed that this was evidence that cathode rays were electromagnetic waves.

Zhang Xingjiu didn't jump to conclusions, but instead proposed a possibility. "Just now, when the battery was connected, the fluorescent spot of the beam wavered slightly. Could this be because the residual gas molecules dissociated under the action of the electric field, forming positive and negative ions? The positive ions tended to the negative plate, and the negative ions tended to the positive plate. Before they could deflect, they quickly canceled out, and the light spot returned to its original position?"

"Well, that's indeed a possibility." Lang Zhiwan replied after a moment's thought. "Then let's conduct another experiment to see if we can continue to observe the light spot's swaying."

The results of the second experiment were exactly the same. The light spot shook, but the cathode rays did not deflect at all.
So Zhang Xingjiu updated the experimental plan. He spent several days draining the gas in the vacuum tube as much as possible, and then conducted the experiment again. This time he obtained stable deflection.

This result made Professor Lippmann very excited. He came to the laboratory to watch the experiment in person. Zhang Xingjiu also used the method he had just designed to measure the propagation speed of cathode rays in the vacuum tube during the experiment. The result was 1.9×107 cm/s.

He held up the data and announced to everyone, "This speed is far lower than the speed of light, so cathode rays cannot be electromagnetic waves."

"Is that particle flow?" someone blurted out.

"No, this experiment only proves that cathode rays are not electromagnetic waves, but it cannot prove that they are particle streams. So we need new experiments."

(End of this chapter)