What do you think will happen if every single human being on earth jumped at the same time? It's one of those questions that smart-aleck children ask their parents just to see them squirm and scramble to make up an answer to a question they obviously don't know.
Of course, some kids ask because they're really curious and they want to know. The answer has always remained a mystery--up until now, that is. Will the earth jump out of its orbit? Will the world implode? Will the planet somehow get closer to the moon? (Okay, the third one's just plain silly, but who knows what might happen?)
Actually, XKCD's Randall Munroe does know. Or at least, he thinks so. Check out what he thinks in the video above.
Have you watched it? Pretty disappointing, isn't it, to find out that what will happen will most likely be a big fat nothing. But we probably should've been able to figure that out, since the earth weighs a trillion times more than the weight of all human beings combined.