Well, if every single person on the planet jumps exactly at the same time would it cause an earthquake on the whole planet, or we would not feel anything at all? So maybe it is probably not something that we have ever considered, but now as the question is out there you may be too much curious to know, why? Well, it is a very interesting question in young minds “What If Everyone on Earth Jumped at Once?”. It’s a great question considering such uniform motion among all the people living on earth which is about 7.3 billion. So, if all people living on earth jumps at the same time without changing their location there would be no change at all as the there will be no change in the Earth’s center of mass. However, there will be a whole lot of energy released. Some will get dissipated in the air while some will be released as sound energy. Some changes in dust might be observed in a dusty area.
With the help of classical mechanics, it has been calculated that the earth at the equator spins at more than 1,600 Km/hr well that is really too fast. And then an amazing thing is that in almost the same way a spinning ice skater will be able to speed up when they just move their arms and legs closer to the body, as because more mass in the centre would result in a faster spin and like this way you can actually increase the speed of the earth’s rotation. Therefore, if you just get down towards the ground or near the surface of the earth right now, and move your whole body mass closer to the center of the Earth, then technically you will actually speed up the rotational speed of Earth and it will make the day little shorter. Though the effect of the impact you have made on the Earths rotation would be so much fractionally small that not even a machine on the earth is sensitive enough to measure the value, but still it can be calculated and like this way it can be figured out the impact of the worlds whole population just by redistributing their mass away from the centre of the Earth and then towards the centre of the earth in just one big jump.
Though we don’t need any of these hypothetical scenarios like this to observe the effect. In 2011, Japan was hit by a disastrous earthquake and because of that, the redistribution of some of the mass of the earth towards the center of the Earth occurred. And due to that incident since then every day has been shortened by about 0.000018 seconds.
However, if everyone on earth is taken to a particular small area on earth just enough to 7.3 billion people which is the population on Earth. There will be little change in the Earth’s Centre of Mass due to the shift of mass of the 7.3 billion populations.
However with respect to the mass of the earth even the mass of the population of 7.3 billion people is a very small quantity. Now, considering if the whole population jumps on the same time there will be almost no effect on the Earth’s orbit. For if we assume the whole population jumps about a height of 30cm, in order to balance the momentum the Earth’s axis will shift away only about one-hundredth of the radius of a hydrogen atom. Which means accumulating all the population and making them jump is not a good way to change the Earth’s orbit.
But the question arises why does the change occur. It is because the Earth tries to keep the position of the center of mass unchanged and to balance the moment caused by the 7.3 billion people while jumping is balanced by the shift in Earth’s Axis. The movement occurs as the whole 7.3 billion populations are exerted by a force by the Earth and the same force is applied on the earth by the 7.3 billion populations. This is according to Newton’s 3rd Law which says “For every action, there is an equal and opposite reaction”. But though the change is almost negligible its a fact that the Earth is affected equally as the people are in the jumping process.
So what will happen if all 7.3 billion people in the gather together at one place? We would definitely make an impact. If all the people of the earth gather together at and jumps one foot in the air, we would land at the same time. And then instantly we would release an enormous amount of energy. Of these huge amounts of energy, some amount of energy would be absorbed by our shoes while rest of the amount of released energy would go into the air and ground. One of the first things we would notice that there would be a tremendous sound like a thunderous applause. The volume would reach approx. 200 decimals which are loud enough to shatter our eardrums and at the same time we would start to feel is that the ground begins to shake.
The vibrations from landing all the 7.3 billion people at the same time would cause anywhere from a magnitude of 4 to magnitude 8 of Richter scale earthquake. The size of the magnitude of the earthquake would depend on how much energy the ground absorbs compared to our shoes. Though a magnitude 4 earthquake would not cause much damage a magnitude 8 earthquake on the Richter scale would flatten the poorly constructed buildings also will collapse electrical lines then the train rails would be out of shape and the bridges will be demolished. And also if we do this incident near the coast the earthquake could trigger a tsunami with the waves of over about 100 meters tall. But still, despite these local destructions earth will continue in its orbit as like nothing has happened. Even 7.3 billions of people cant change the course of the cosmos.