By Phil Plait | August 25, 2012 7:00 am

I have a very odd coincidence to report.

I like getting fun questions from folks, the kind that take a little bit of math and physics to explain, but wind up taking you to fun places. A common question like that is, "What would happen if everyone in China jumped all at once?" Would it throw the Earth out of orbit? Would it cause an earthquake? Would it do anything?

The answer is, essentially, no. I tackled this a few years back; there was this announcement by a group that wanted to get 600 million people to all jump at once so that the Earth would be pushed farther from the Sun and global warming would be solved.

Um, yeah. They called it World Jump Day, and I made quick work of it. Nothing at all would happen, for lots of reasons. Still, it’s fun to think about, right? And it turns out World Jump Day was something of a prank anyway.

And that’s where the coincidence I mentioned comes in. I recently happened to see a video done by vsauce asking this very question. He handles it really well in an entertaining video:

My opinion: science is always better when Felicia Day makes a cameo! And, of course, vsauce is right.

So anyway, I liked the video, and made a note to myself to write it up on the blog here. And then, literally the next day, what happens? My pal Randall Munroe (of xkcd fame) goes and writes about this very topic for his "what if?" series!

Although, to be fair, Randall takes it in a slightly different direction. Still. Weird.

Of course, coincidences happen all the time. It’s a big world out there, with lots of things going on. There’s bound to be the seemingly-spooky overlap or two between ’em.

And as a final note, if you want to read more about the gnarly math of millions of people jumping, Dot Physics has you covered.

CATEGORIZED UNDER: Cool stuff, Debunking, Geekery, Humor, Science

Comments (36)

  1. Chris P

    I subscribe to your blog, XKCD and vsauce, and I was wondering if it was some sort of cross-platform group activity where the same question was asked to, and answered by, lots of different science communicators or something. And I wondered if there were any others answering the question that I had missed, but nothing more was said about it so it just kinda slipped off my radar.
    Thanks for explaining it was just a huge coincidence 😀

  2. Nice! A very good synchronicity… I liked the rather… unexpected direction the xkcd explanation took.

  3. But.. but what if.. at the same time as everyone on one side of the planet was jumping up, everyone was also on the other side of the planet pushing down?? (using some not entirely feasible quantum teleportation malarky of course 😉 )

  4. edwardv

    What if everyone moved to the equator, or the poles? How much would the Earth’s rotation change?

  5. Chris

    @1 Chris P
    For their next blog they will be talking about quantum entanglement and spooky action at a distance. 😀

  6. KAE

    And if everyone ran in an easterly or westerly direction would the Earth’s rotation slow/speed up measurably or at all? Probably not.

  7. MichaelL65

    What if everyone took a breath and blew up at the sky? Would that make the clouds go away on a rainy day?

  8. edwardv

    @6 KAE
    It’s still fun to see what the calculations say.

  9. edwardv

    @7 MichaelL65
    Or maybe they could start a tornado.

  10. Ehm, Dr Phil? Beg to differ. Happens that this morning I was watching something on german tv, were the moderator asked the public of a big outdoors popfestival to jump. Just that they could measure the impact.
    As of 2:55
    The jumped a freaking 0.6 on the scale Rockter!
    And since there are more chinese than whatever, they simply has to rock the planet.

    Ow and btw, before anyone goes on looking into the program. He´s goin to extract some of his own meat to eat to know what it tastes like.
    Just that you know.
    The wonderous things you´ll see at 11 something in the morning.

  11. Wzrd1

    I remember the jump story when it first was published in a newspaper as an allegory for cold war armaments. The theory then being China jumped one foot as one body, triggering massive earthquakes in the US, which was counted by every US citizen jumping 3 feet and culminating with one side jumping 10 feet and the other side jumping even higher, resulting in both sides having broken legs.
    I think it was reprinted in the Philadelphia Inquirer, but hanged if I can recall the date now.
    Over the years, I’ve witnessed a few allegorical stories and jokes become the meat of rumored “facts”.
    But then, people tend to believe anything that they’re told, even campaign promises.

  12. Fozzie

    Of course, assuming everyone was in one place at midday and jumped together and could actually move the Earth away from the Sun, it would put it into an elliptical orbit, so instead of curing global warming, it would heat the Earth up even more twice a year!

  13. Frost Bite

    The “jump” idea is just another example of the over-inflated ego of human’s trying to incorperate their existence into the grand scheme. Get over it already, the earth could vanish today and the universe would continue unchanged and without notice.

  14. And how high do I have to jump up to land excactly next to my footprint I left?
    I mean, I jump, the earth rotates under me etc.

  15. DanM

    I have an even stranger coincidence to report. Just as I sat down to read about your interesting coincidence, a friend of mine called, and he was just also sitting down to read the *same* blog post at the *same* time.

    That there, that’s what ya call a meta-coincidence. I suppose I never meta-coincidence I didn’t like.

  16. Yes, Felicia Day makes everything better.

  17. HvP

    SkyGazer you said, “I jump, the earth rotates under me…”

    Tsk tsk, you forgot that your sideways momentum will still be preserved and you will continue to move along with the rotation of the Earth even as you are in the air. It’s just like if you flipped a coin in a moving airplane the coin wouldn’t fall to the rear of the plane; it would continue moving along with you until it just fell back into your hand.

  18. Ah well, back to building a counter rotating house on the North Pole.

  19. Chris

    But what if we kept jumping at the resonant frequency of the Earth?

  20. Hmmm maybe if the Mythbusters just made more of those lovely bridgewalking soldiers and make ´m jump…*

    * I love tose little steppers (dsc.discovery.com/tv-shows/mythbusters/videos/breakstep-bridge-minimyth.htm)

    @16. HvP
    I didn´t forgot, I just didn´t bother.

  21. Alaric

    But… what if everyone in the world jumped at the same time, but they were all simultaneously distracted while in the air, causing them all to miss the ground?

  22. Daniel J. Andrews

    For those who haven’t heard, Neil Armstrong just died.

  23. Sean H.

    I just got lost in Vsauce’s videos, quite brilliant. Thank you pointing them out.

  24. Prof.Pedant

    My impression is that the number of possible strange coincidences is large enough that not experiencing strange coincidences would be a far stranger thing than any possible combination of strange coincidences would be.

  25. Sili

    I’d be more curious as to what might happen if everyone ran in the same direction East to West or the other way round. How much could be slow the rotation of the Earth? Or speed it up to counter the leap seconds?

  26. Lucas

    Just tell Randall to get out of your head. He likes to do that.

  27. Infinite123Lifer

    I think experiencing like say … 86,399 strange coincidences per day would be just as equally a strange (not lesser) coincidence as not experiencing any strange coincidence ever. I had to take a second away for all the monkeys jumping and breaking their legs.

  28. JimmyDean Breakfastsausage

    If the entire population of earth was on Rhode Island, wouldn’t it create a huge increase in temperature at that spot? The equivalent of Seven Billion 50 watt light bulbs?

    Perhaps enough to create a strong wind? Maybe a hurricane?

    After all, a hurricane is caused by the oceans getting rid of heat? Yes? No?

  29. Phlip

    @HvP: All that means is you need to jump high enough for the Coriolis effect to be significant…

  30. HvP

    SkyGazer, “I didn´t forgot, I just didn´t bother.”

    You could be on to something here. According to Douglas Adams the secret to flying is to throw yourself at the ground and keep missing it (usually by forgetting that it’s there) then I don’t see why you couldn’t go into low orbit simply by shrugging off the laws of inertia. 😉

  31. Finally, someone who understands.

  32. Zippy the Pinhead

    IF 600 million people jumping up simultaneously COULD actually move the earth a net amount, those unfortunate souls would find themselves launched into space to die a quick but horrible death.

    Of course, no individual can jump off the earth under their own power and neither can a large group. Maybe if we could combine all the energy of jumping and all ganged up on one guy we really didn’t like we could launch that person into space.

  33. James Evans

    I have a button that asks, “What if the whole world farted at once?”

    I really do.

  34. Fredeliot

    Back in the 1960’s there was a proposal that if everyone in China jumped repeatedly in a coordinated manner to achieve resonance, they could cause destruction elsewhere on earth. I don’t think very many took it seriously pre-internet.

  35. Matt B.

    I’d like to tell the narrator, Michael, that the word is “calculable”, not “calculatable”. The suffix “-ate” is dropped before adding “-able”. But you have to be careful; sometimes the “ate” isn’t a suffix, like in “translate”. Once I learned this, I finally understood words like “inimitable” (unable to be imitated) and “implacable” (unable to be placated).

    Also, when he mentions the city of Los Angeles, the map shows the county of Los Angeles, which is much bigger.


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