What if everyone on earth jumped up at the same time?

[Tamahome]

Let the XKCD author explain in this video. There's a cameo by Felicia Day at the end:

http://io9.com/5937853/what-would-hap...

[Mark]

But what if everyone jumped from an airplane at the same time?

[Stan]

Strangely enough several years ago I figured this out as well.

You have to make some pretty basic assumptions though (world population, average weight, average height of jump, force exerted from initial launch and landing, etc...).

Once you have that it's really just basic algebra.

And I came up with the same answere - nothing would happen, just not enough force

[Tamahome]

What if we all laid down at the same time, would the earth spin faster like an ice skater? Remember, Americans are growing in mass all the time. :)