If everyone in the world jumped together at the same time, would it shake the earth?

I often see questions like these on the Internet, and I think they are very strange and just laugh them off. After seeing them many times, I have seen many netizens repeatedly raise this question, and some even think that just as if all the people on a large ship jumped together on one side, the ship might capsize, if all the people in the world jumped together, it might shake the earth or even destroy it.

Since it is so serious and involves some scientific common sense, as a popular science writer, I have to join in the fun. So if all the people in the world come together and jump to the sky, will it really make the earth tremble and then destroy it?

Now let's count on our fingers, use elementary school math problems, and based on basic knowledge of physics, talk about the general consequences.

According to the latest statistics from the United Nations, as of September 15, 2022, the total population of 238 countries and regions in the world is 7,898,236,143. Among them, China has the largest population, which is 1,447,301,400 people; India has the second largest population, which is 1,403,018,576 people. The following countries are: the United States, Indonesia, Pakistan, Nigeria, Brazil, Bangladesh, Russia, etc., which are not listed one by one.

These people are distributed all over the world. If they jump up and fall down in different places, according to simple common sense, these forces seem to be mostly offset. I am afraid that this is not in line with the original intention of friends who ask such questions. Friends who ask such questions probably want the world's population to gather together, and someone gives a command: 1~2~3, jump together, and then a horrifying scene occurs, the earth tilts, the orbit shifts, and it goes towards destruction.

In order to better answer the question, let's sort out the problem and clarify some data: first, the total population is an integer, about 7.9 billion; secondly, people include the elderly, the weak, women and children, tall, short, fat and thin, so let's roughly take the average human body size, about 160 cm and 60 kg.

Now let's imagine what a concentrated population would look like.

The earth's surface area is about 510 million square kilometers, of which the ocean accounts for about 71%. The population is mainly concentrated on about 149 million square kilometers of land, most of which is mountainous and desert, so the habitable area is actually very small. Today we don't care about these, just talk about how much area is needed to concentrate the population to make a surprise jump.

It should be no problem for 4 people to stand in one square meter. If all the people in the world were to be crowded together, an area of ​​1,975,000,000 square meters would be needed, which is 1,975 square kilometers. But the problem is that it is difficult for 4 people to jump. They would bump into each other and it would be difficult for them to jump in unison.

If two people stand per square meter, the probability of mutual impact when jumping is much smaller. In this way, the area needs to be doubled, which is 3,950 square kilometers, or a circle with a diameter of about 71 kilometers. The total area of ​​Beijing is 16,410 square kilometers. If all the people in the world stand together, only about a quarter of the total area of ​​Beijing is enough.

From this perspective, the world's population is not concentrated very much. Four people per square meter only accounts for about 1/260,000 of the global area; 2 people per square meter accounts for about 1/130,000 of the global area.

If we use a football to represent the earth, how much area does the person standing on the football occupy?

The surface area of ​​a competition football is 1520.2 square centimeters. According to the ratio of the area occupied by the earth's population concentration to the earth's surface area, if four or two people stand in one square meter, the area on the football will be reduced by the same proportion to about 0.0058~0.012 square centimeters, which is a dot with a diameter of about 0.6 mm, only a quarter of the size of a sesame seed, about the same size as a slightly larger dust particle, and only people with very good eyesight can barely see this dot.

If we think about it, this dust particle bounces up half a dust particle and then falls on this football. Can the football be pushed? The answer seems to be no.

Now let's calculate the impact of jumping based on the total weight of a human:

If each person weighs 60 kilograms, the total weight of 7.9 billion people is 474 million tons. The total mass of the earth is about 60 trillion tons, so the total weight of the world's population is only about 1/12.7 billion of the mass of the earth. In this way, if the earth is reduced to a 60-kilogram human body, the total weight of the population on the human body is only 4.7 micrograms, or 0.0000047 grams.

This is roughly the same weight as a mite, which is basically indistinguishable to the human eye and widely parasitizes on human skin and various spaces. There are hundreds or even thousands of mites active on the human face at any time. If one of these mites jumps, will you feel it?

Then let's calculate how much work can be done if 1~2~3 people in the world jump up and jump in unison (which is actually impossible)? The formula for people to do work to overcome gravity when jumping is: W=mgh. Here W represents the work done, in joules (J); m is the mass of the object doing the work, in kilograms (kg); g is the earth's gravitational constant, which is about 9.8N/kg; h is the height of the jump, in meters (m).

According to this formula, the energy required for each person to jump to a height of 0.5 meters is about 294J. The work done by the world's 7.9 billion people jumping 0.5 meters at the same time is 2.3226 trillionJ. The energy of each ton of TNT explosives is about 4184,000,000J. The energy produced by everyone in the world jumping 0.5 meters at the same time is equivalent to 555 tons of TNT.

The explosion of 555 tons of dynamite may seem like a lot of energy, but it is far less powerful than an ant shaking a tree. The former Soviet Union once tested the largest hydrogen bomb in human history, the "Big Ivan Bomb", with an explosive equivalent of 50 million tons of TNT. The surface of the earth was shaken, but the earth was not shaken at all.

Moreover, the 1~2~3 jumps of humans are different from the explosion of dynamite. When they jump up and push off, it seems that they give the earth a reaction force, but they fall down quickly. The gravitational force between the earth and humans offsets the previous push and neutralizes the energy of the jump.

Conclusion: The idea that humans gather together and jump at the same time in an attempt to move the earth is neither possible nor effective, let alone deviating from the earth's orbit and destroying it.

This is a bit like someone thinking that he can fly to the sky by pulling his hair, or that he can fly by stepping on his feet. Having said so much, can it wake up some heroes from their dreams? Welcome to discuss and comment.

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