Scientists do an experiment, and I have to gain three pounds?

After the Mid -Autumn Festival,

The sycamore leaves in Beijing were yellow.

There is a sound in the underworld,

Round in the brain, stomach, and every cell:

"It's time to post autumn!"

So steamed lamb steamed bears steamed deer tail,

Roasted chicken roasted flowers, duck, roast goose, and goose.

And successfully wiped out.

Every time I go to the scale, Xiaobian was shocked by the number of weight -loss.

(When can the balance of the wallet change this way?)

Despite the quality of weight use,

But the weight measure is really powerful!

is it possible--

It's not that I get fat,

Is there a problem with the gravitational constant?

No doubt

Gravity constant G is the most accurate physical constant measured by scientists.

From Newton to today,

G's value often jumps repeatedly.

Let's take a look today,

Story of gravitational constants over the past three hundred years.

gravitational! gravitational!

In 1687, Lord Newton Niu wrote such two paragraphs in "Mathematics of Natural Philosophy":

The gravity of the object that the object is pointing to any planet is the square of the gravity of any planet from the distance from the center of the planet. All objects are attracted to every planet; the gravity of an object on any planet is equal to the distance between the center of the planet, which is proportional to the amount of material contained in the respective objects.

Ji Ye waved his hand and wrote the most critical physical content of gravity, but left a proportional coefficient G in the formula. This is the pseudo -gravity constant of more than 300 years of scientists.

For three hundred years, scientists have not been able to accurately determine the value of gravitational constant. Today, most of the basic physical constant accuracy is one billion or even one -tens of billions, and the accuracy of the gravitational constant is still one -one -one -one -one -inch.

Gravity is too weak, and the weak universe is its stage; gravity is too difficult to block. You always need a house to do the laboratory -the quality of the cement and bricks itself will interfere with measurement. To this day, there are still a large number of the best physicists who tirelessly improving the constant of gravitational constant.

Time has flowed from Newton for three hundred years, and generations of scientists Yu Xingye Hao Hao's scriptures, finally found out several methods that can precisely measure gravitational constants: twisting scales compensation method, twisting cycle method, atomic bouquet or laser Interference method and the recent resonance method. They each have their own autumn and calculate this annoying and charming physical constant.

High School Physics Story

Newton wrote for more than a hundred years of gravitational law, and no one has always measured the specific values ​​of the constant gravitational constant. It was not until 1798 that Kavadi, the University of Cambridge University in the UK, improved the precision twisting scales and completed the famous twisting scales. It was now written into textbooks. The experimental device, one of the top ten most beautiful experiments in the history of physics, is very subtle, becoming a blueprint for many precision measurement devices in later generations.

Twisting scale is a device that is suitable for measuring weak interaction. Its core component is a wooden rod hanging on the hanging wire. The two ends of the wooden rod can be placed in different inspection devices.

In the experiment of measuring gravitational constant, the two ends are a pair of high -density quality metal balls; and in the Kulun twisting experiment with static electricity strength, the inspection device is a pair of small objects with equivalent charge. Essence Put on the inspection device that can significantly change the force field, such as a shot that weighs one ton, or a metal with a lot of electricity in the Kulun experiment.

Schematic diagram of Kwendi Xu Two Scale Device

The inspection device and force source at both ends of the wooden rod are always arranged symmetrically, so the power of the two ends is large, and a large reverse is formed to form a forceful twist scales and the hanging wire twist. When the torque of the twisting of the hanging wire is balanced with the puppet torque of the outside, the size of the torque can be measured through the angle of the switch to reversing, and then the size of the force is calculated. Because at this time, there was only the unknown of the gravitational constant in the gravity formula, the calculation of G became a primary school mathematical practice question.

Although primary school mathematics is very simple, it is difficult to get reliable data that can be substituted into the formula. How to avoid the wind interference experiment that people walk around in the room? How to accurately read the angle of the twisting of the suspension?

In order to shield the interference as much as possible, the twisting scales were placed in a wooden box. The person was used to adjust the twisting scales by pulling the hand and the knob outside the room, so as to avoid the impact of the quality and air flow during the operation.

In order to more accurately measure the turning corner of the hanging silk, Cavendi used the way of light release. The accurate fine light beam sent from the light source is reflected on the wall of the room on the flat mirror with the twisting scale. With the rotation of the twisting scale, the light spots on the wall also moved, so that the tiny -turning angle of the twisting scale was converted into a relatively long distance. People can obtain another key data in the G experiments by observing the distance from the lens barrel outdoors.

Freshman of twisting scales

Since the 20th century, the many inconveniences of the classic twisting scales static measurement, scientists have begun to use the twisting cycle method as one of the most commonly used methods for precise measuring gravitational constants. The periodical method of twisting scales is a dynamic measurement method, which mainly measures the change of several physical quantities over time, so it can be removed from the interference of the static method without changing with time.

Tom: As long as I don't bow my head, the gravity does not exist

An ordinary free suspension scales will be reversed according to the form of damping the vibrator, and the angle of the twist is met. Among them, the turning inertia of the twisting scale (the status is equivalent to the quality in the linear movement); it is the damping coefficient that covers all the exercise attenuation The effect of the twist in the twisting scale. The rotation frequency of the twisting scale meets. In the process of measurement of the cycle method, two heavier objects near the twisting scale are placed as "attractive quality", and the two attractive quality connections are parallel to the balanced position of the twisting scale. At this time The total recovery torque increases, the system rotation becomes faster, and the vibration frequency is, the gravitational coupling constant determined by the quality distribution.

Next, the position that attracts the quality is adjusted to the two -connected connection at the balancing position of the twisting scale. At this time, the attractive quality gravity provides a negative recovery torque for the twisting scale system. Essence In this way, the two types can be reduced to determine the gravitational constant. Among them, the square difference between the two types of twisting scales under the configuration, and the difference between the two configurations, respectively.

Twist scales cycle method G principle diagram

In the twisting cycle method, we really need dynamic measurement in fact only the frequency -that is time. It happens that time is a physical quantity that is easy to measure accurately. Compared to the rotating angle with a flat mirror reflection light, the time to measure the pulse laser is as simple as a cat eats fish.

As for other parameters, such as rotating inertia, power coefficient, and even gravity coupling constant, are geometric parameters without involving the movement of twisting scale -in short, you can take it down and put it on the table. These relatively simple measurement requirements enable the periodic measurement G experiment to achieve a relatively high accuracy. However, the simple price of measurement is that the experiment continues for a long time. How to maintain the environmental stability without introducing new interference has become a problem that scientists need to solve.

HUST-99 experimental device schematic diagram

In order to obtain a stable external environment, scientists chose to conduct experiments in the cave and use heavy mountains to block external vibrations. In 2006, the Hust-99 experiment measured by Chinese scientists using the twisting scales (in Wuhan cave) was measured at 130 in the relative error of one million, which became the eight recommendation values ​​of the gravitational constant of the gravitational constant adopted by the International Science and Technology Council. One of them also appeared on high school physics textbooks.

I got fat again?

Recently, a group of Swiss scientists used a new dynamic resonance method to give a measure value of the gravitational constant. The gravitational field of a vibration beam will cause a weak vibration of another beam. Use a laser to measure the cycle of two vibrations to calculate the value of the gravitational constant. They measured 18 times, and the average value was that the uncertainty was 1.66%. In other words, the constant value of the gravity of this measurement is 2.2%higher than the existing international recommendation value. If this is the case, Xiaobian has to be "three pounds of fat" (seemingly exposed to weight?).

Original source, translation source

Although the uncertainty of the new method is relatively large compared to traditional methods such as twisting scales, even if considering the uncertainty of 1.66%, the value measured by the new method is still greater than the current standard value. This may be because the new method is measured more accurately, but it is also likely that there are some system errors that have not been excluded -after all, from Cavendi to more than 200 years, everyone has used different twisting scales around the world all over the world. The results of measurement in various places are still very close.

Of course, it may be simply that the gravitational constant in the Swiss cave is different from the value of the other parts of the world -previous scientists have claimed that the gravity constant will change with the position and even measurement scale. If this is really the case, can this proportional coefficient in the gravity formula be called "constant", and it may be another thing that scientists will have some brains and saliva.

In any case, to this day, it is already classic, stable enough, and daily use. The continuous pursuit of gravitational constant precision measurement values ​​is more about the pursuit of physical theory truth and climbing the peak of precision measurement technology -the development of theory and technology is of course not a waste, of course, it will benefit people's lives. It will grow into a giant in the next era [Note].

Faraday feels great

The change of gravity constant is not important to increase a few pounds. It is important to eat a full stomach. Crab body fertilizer and sea bass flavor. I wish our food readers a lot of meat.

Note: High school physics textbook once mentioned a Faraday anecdote: When Faraday first invented the generator, a British lady asked him what the electricity was. ? "

references

[1] Newton, Wang Kedy. Scientific literacy, scientific Yuan Dian series: mathematical principles of natural philosophy [M]. Peking University Press, 2013.

[2] What are the significance and difficulties of high -precision measurement of "all gravity constant"? -The Answers of the Crab of the Lottery -Zhihu

https://www.zhihu.com/question/375778009/answer/1112711841

[3] Tu Liangcheng, Li Qing, Shao Chenggang, Hu Zhongkun, Luo Jun. The precise measurement of gravitational constant G [J]. Chinese science: Physics mechanics astronomy, 2011,41 (06): 691-705.

[4] Zhao Jinquan, Zhang Shuo, He Yanlan. Laser interference method Testing Gravity constant [J]. University Physics, 2007 (12): 53-56+59. [5] Brack, T., Zybach, B., Balabdaoui, F. Et Al. Dynamic Measurement of Gravital Coupling Between Resonating Beams in the publicz regime. Nat. PHYS. 18, 952–957 (2022).

[6] Nie Fuyuan. Gravity constant measurement 200 years [j]. Physics report, 1998 (07): 37-38+44.

[7] He Wenyu, Wang Xiaojun. In-depth restoration of the teaching and discussion of the inquiry process of the physicist-take the Kavendi Xu twisted scales as an example [J]. Physics teacher, 2019,40 (11): 20-23.

[8] Tu Liangcheng, Luo Jun. New progress of gravity experiments and theoretical research [J]. Natural scientific progress, 2005 (08): 897-906.

[9] https://mp.weixin.qq.com/s/wcyklhs1knsrg5jflk83a

Emoticon package comes from the Internet

Edit: Tibetan idiot

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