What would happen if everyone on Earth jumped at the same time?

Have you ever thought what would be the possible outcomes if everyone on Earth jumped at the same time? Obviously, something would happen because, we know, by Newton’s Third Law that: For every action, there is an equal and opposite reaction. About 7.1 billion people live on Earth. If all of us were to gather up at the same place to jump at the same time, it would inevitably result in something if not something big.

Understanding the Science behind it:

Imagine a ballerina rotating on a fixed spot with her arms stretched out. When she pulls her arms in, her rotating speed increases. The distance of her arms from the axis decreases and thus, the inertia decreases too. Due to the law of the ‘Conservation of Angular Momentum’, the speed increases. Similarly, if all the people on Earth were to crouch down on the ground then jump, the Earth would rotate faster although by a negligible amount.

The same concept applies when major earthquakes shake and redistribute the tectonic plates. In 2011, a 9.0 magnitude earthquake hit Tōhoku, Japan. The massive quake moved a lot of mass towards the centre of the Earth that, after the earthquake, it was found out that every day has been 0.0000018 seconds shorter. To create that impact, we’d need 7 million times the current number of people living on planet Earth.

The increase in the speed of rotation will also cause an effect on the Earth’s gravity. The Earth’s gravity is 9.807 m/s² and, it depends on the rotational speed of the planet, which decreases as we move away from the equator towards the poles and it results in the gravity on equator being less than the amount found on the poles due to the centrifugal force affecting the equator due to Earth’s rotation. When the rotational speed increases, the effect of earth’s gravitational pull is reduced. After a certain point, if the speed continues to increase, the gravity would be reduced to negligible and everything would be thrown off into space.

But the question is, how to gather all the people in the same place?
It’s not practically possible. This is why we use what is called a thought experiment.

Time for the Experiment:

Hypothetically, if all the 7.1 billion people were to gather at the same place to better sync our times to jump at the same time, they would proceed to also land at about  the same time.

Courtesy: BI Science

First of all, that would create an ear-piercing, thunderous noise due to the all our feet hitting the ground and creating a thud noise being amplified by about billions of other pairs of feet resonating at the same frequency.

Secondly, assuming that all of us managed to jump 50 centimeters high, the force generated by that would propel the Earth away from us by a negligible distance. To be exact, the distance would be 1/100th of the diameter of a Hydrogen atom. After jumping, we’d return back to the same place and so will the Earth. Thus, it will not cause much of an effect at all.

And to finish it off, it would generate an enormous amount of energy. Some of the energy would be absorbed by our shoes. The rest of the energy would spread across the air and ground causing the ground to vibrate resulting in an earthquake of 4-8 magnitude. A 4.0 magnitude earthquake will not cause much damage but one with 8.0 magnitude can demolish buildings, bridges, electrical towers and other poorly constructed structures.

Conclusion:

However, all that destruction will not affect the cosmos in any way. The effect of this on the Earth’s rotation will be calculable but extremely small and immeasurable by any man-made device. The Earth will still continue to rotate at the same exact axis. The question of how to get those people back to their homes might be a more interesting one and as far as we can tell at least One Billion of them will die within the course of a year around the place they decided to perform their greatest feet of accomplishing nothing but pushing humanity to start over with civilization all over again.