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Newton's third law states that in every action, there is a equal and opposite reaction.

When we jump, we exert a force on the ground and the resultant force upwards propels us up into the air. However, the Earth's gravitational force pulls us down onto the Earth. As there is an equal and opposite reaction, we are also pulling the Earth to ourselves.

That said, is it theoretically possible to steer the Earth if all humans jumped at the exact same time?

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Not really, because the effect is too small.

Let's say there are 8 billion people on Earth and each of them has a mass of $100$ kg. That makes the total mass of humans $8 \times 10^{11}$ kg. For comparison, the mass of the Earth is about $6 \times 10^{24}$ kg - 13 orders of magnitude larger.

It would be a bit like asking "if a flea on your body jumped in one direction, could it push you?" Furthermore, the flea's effect on your body is larger than our effect on Earth.

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To jump up, all the humans would need to exert a force on the earth, true. But if the humans were equally distributed around the earth, these forces would cancel out.

To have an effect, humans could go to one side of the earth and all jump at the same time.

What would happen then?

The earth would be pushed sideways and deviate from it's course (a tiny amount) for about a second until all the humans landed again.

But the centre of mass of the earth (including humans) would never change course - either during the journey that the humans took to get to one side, or during the jumping and landing.

So the short answer is that it's not possible to steer the earth.

Where were you thinking of going?

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  • $\begingroup$ It was just radical thinking. Just wanted to see what would happen is all. $\endgroup$ – Nigel Tan Apr 8 at 8:55
  • $\begingroup$ Interesting thought, some might wonder whether the orbit of the planet could be adjusted to combat global warming. One thing not mentioned was that before the jump, everyone would have to bend their legs slightly, bringing people closer to the earth, and the earth would be raised up towards the people, (if they were at one side) - but the combined centre of mass stays in one place. By everyone sitting down this effect could last longer than jumping up, but again the centre of mass is unchanged. To truly steer the earth we would have to eject a mass off it permanently e.g. using a rocket. $\endgroup$ – John Hunter Apr 8 at 9:31

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