Have you ever wondered what would happen if every single person on Earth jumped at the exact same time? Would it cause an earthquake or would we not even notice? To answer this question, we first need to understand the Earth’s rotation.
The Earth spins, creating night and day, and it spins quickly. At the equator, the Earth is spinning at more than 1,000 MPH. A spinning ice skater can speed up by moving mass closer to the center, and the Earth is no different. If you move your mass closer to Earth’s center, technically, you will speed up Earth’s rotation, making the day shorter. However, the change that you would make to the Earth’s rotation is way smaller than we could even measure, but it is calculable.
The impact of redistributing mass can be quite impressive when you talk about more than just one person. For instance, the earthquake in Japan last year redistributed so much of Earth’s mass towards the center, that every day since then has been 1.8 microseconds shorter. But what can us humans do to the Earth all on our own? There are more than 7 billion of us now. What if we all got together in one place and jumped?
If you took the entire human population of Earth and had them all live in one place with the same density that people live in New York City, you could fit everyone into the state of Texas. However, if every single person alive right now on Earth stood shoulder to shoulder, you could fit all of us into the city of Los Angeles. It would be an incredible sight to behold – a mere 500 square miles containing every single person on Earth.
Unfortunately, not much. Our collective mass compared to the mass of the entire Earth is like nothing. Dot Physics calculated that if all of us were to get together in one location and all jump 30 cm into the air at the exact same time, we would push Earth away from us a tiny amount. Earth would only move away from us about 1/100th of the width of a single Hydrogen Atom. And because we’re all jumping and then going back to where we started, Earth is just going to move back to where it started.
So, our big jump won’t be able to change Earth’s position in space, but what about seismic activity? The BBC conducted an experiment with 50,000 people and discovered that a kilometer and a half away, it only registered a .6 on the Richter scale. You would need 7 million times more people than even live on Earth right now to jump at once to recreate the earthquake that recently happened in Japan.
Our collective jump would contain a lot of energy. The Straight Dope calculated that even if only the people who lived in China got together and jumped, their jump would be the equivalent of 500 tons of TNT. Of course, 500 tons of TNT doesn’t do much to an Earth that weighs 6 sextillion 588 quintillion tons.
To make yourself feel more powerful, consider this. If you pick a card from a deck of 10, you have just decimated this deck of cards. Technically, decimate does not mean “obliterate completely.” Deci=10. It means to take away 1/10th of something. So, the next time you take a quiz and don’t do so well on it, you only get 10%. Well, sure, that’s an “F”, but by getting 10% of them right, you DECIMATED that quiz.
Since we’ve been talking about crowds, let’s talk about YouTube crowds. YouTube audiences, that view count that you see at the bottom of every video, can give some perspective on it. Dunbar’s Number is an estimation of the maximum number of people we can have stable, social relationships with at a given moment and it’s based on the size of our neo-cortex. These aren’t just acquaintances, these are people you have social contact with – a network where you know how everyone relates to everyone else. The number is usually given to be somewhere between 100-230.
When a YouTube video receives more than 230 views from different people, more people have seen that video than you could ever realistically hope to know well, at a given moment. If a video has more than 100,000 views from different people, more people have seen that video than you will ever meet in your life. And by meet, I mean shakes hands with, learn their name, talk with them for a bit.
Even though you, or even a large group of us, can’t do much to change Earth’s location or rotation, we can affect it a little bit. Newton’s Third Law guarantees this. If you weigh 150 pounds, the Earth is pulling you down with a force of 150 pounds. But you are also pulling up on the Earth with a force of 150 pounds. If you fall 3 meters, the Earth has pulled you down 3 meters. But you have also exerted an equal and opposite force on the Earth. Of course, it’s a lot bigger. So, if you fall 3 meters, you pull the Earth up about a billionth of the width of a proton, which isn’t bad. So the next time you move your body, the next time you jump, think about this. You just affected the Earth as much as it affected you. You’ve got that kind of power.
Gather your classmates and conduct a jumping experiment. Measure the impact of everyone jumping at the same time using a seismograph app on a smartphone. Discuss the results and compare them to the findings mentioned in the article.
Use a globe and small weights to simulate the redistribution of Earth’s mass. Move the weights closer to the center of the globe and observe any changes in rotation speed. Discuss how real-life events like earthquakes can affect Earth’s rotation.
Create a scale model to visualize how the entire human population could fit into the state of Texas or the city of Los Angeles. Use a large map and small figures or dots to represent people. Discuss the implications of such density.
Perform a simple demonstration of Newton’s Third Law using a spring scale and weights. Show how the force you exert on the Earth is equal and opposite to the force the Earth exerts on you. Relate this to the concept of jumping and its impact on Earth.
Select a popular YouTube video and analyze its view count. Compare the number of views to Dunbar’s Number and discuss the significance of having more views than the number of people you can realistically know. Reflect on the impact of large audiences.
Earth – The third planet from the sun in our solar system; the planet on which we live. – The Earth is known as the Blue Planet due to its abundance of water.
Rotation – The action of rotating around an axis or center point. – The Earth completes one rotation on its axis every 24 hours.
Mass – A measure of the amount of matter in an object. – The mass of an elephant is much greater than the mass of a mouse.
Earthquake – A sudden and violent shaking of the ground, often caused by movement of tectonic plates beneath the Earth’s surface. – The earthquake that struck the city caused extensive damage to buildings.
Humans – Members of the species Homo sapiens; individuals belonging to the human race. – Humans have developed advanced technology and complex societies.
Jump – To propel oneself upward or a short distance off the ground by using one’s legs and feet. – The athlete managed to jump over the high bar with ease.
Seismic activity – The occurrence or frequency of vibrations or tremors in the Earth’s crust caused by geological processes. – Some regions experience high levels of seismic activity, leading to frequent earthquakes.
Energy – The capacity or ability to do work; the property that a substance or system has that enables it to perform actions or create change. – Solar panels convert sunlight into energy that can be used to power homes.
Deck of cards – A set of playing cards consisting of a specific number and combination of suits and ranks. – Let’s play a game of poker using a deck of cards.
