Question: what happens if one side of earth jumped at the same time

Emilia Arguello answered on 4 Nov 2024:

If everyone in one hemisphere of Earth could somehow jump simultaneously, the impact would be interesting but not as dramatic as one might imagine (maybe for the best!) Earth’s mass is so large (around 6×10^24 kg) compared to all humans combined that even the combined jump wouldn’t significantly affect the planet’s momentum. Assuming each person weighs 62 kg (and that’s being generous), all combined humans (~8 million) would weigh 496,000,000,000kg, which is essentially negligible on a planetary scale—about only 0.000000000008% of Earth’s total mass! Assuming a hemisphere contains half of that, the number is even smaller!

If, say, half the world’s population of about 4 billion people each jumped up 30 cm and then fell back down, this maaayyyy produce a momentary force on Earth, but it would only be minuscule, and the planet would settle back due to gravity almost instantly. The collective jump and landing would, however, produce a loud thud that’s probably not that pleasant.