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Stupid earth question

  1. Oct 7, 2003 #1
    if everyone in the world were to jump up at the same time would that affect the earth in any way?
     
  2. jcsd
  3. Oct 7, 2003 #2

    chroot

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    Yes, but not measurably.

    - Warren
     
  4. Oct 7, 2003 #3

    Chi Meson

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    The mass of the earth is about 6,000,000,000,000,000,000,000,000 kg. All the people in the world adds up to less than 500,000,000,000 kg. If everyone gathered on one side of the earth and jumped up one meter, the earth would move less than a trillionth of a meter. THis is one hundredth of the diameter of a hydrogen atom.

    So...
     
  5. Oct 7, 2003 #4

    Njorl

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    What if we all gathered together on one techtonic plate, and jumped periodically in sync with its fundemental frequency of vibration?



    Njorl
     
  6. Oct 9, 2003 #5
    Tesla claimed that if he hit an exposed area of bedrock with a hammer, let the wave go round the earth, come back, and hit it again just as it departed again, adding more energy to the wave, he could eventually build up a wave of sufficient energy to crack the earth apart.

    I have always wondered if this is what the little man in Mr. Robin Parson's former avatar was up to.
     
  7. Oct 9, 2003 #6
    There was that kid who asked his mom:
    -Mom, if all rocks of the earth, all the big stones, all the little pebbles, all the rocks you can find, if all of them gathered together, then would they form a huge rock?
    -Yes, answered his mom, obviously from fear of dissapointing her child's imagination.
    -And if all the seas and lakes and the water from all water tanks, clouds, icy areas, if all the water of the world gathered together, then would a gigantic lake be formed?
    -Yes, said the mother again.
    -And if all the people of the world climbed the one over the other, then would a giant man be created?
    -Yes.
    -Wow! Mom, imagine that giant man pick up that huge rock and throw it in the gigantic lake! Wouldn't that be ONE BIG SPLASH!?
     
  8. Oct 9, 2003 #7

    I wonder if this is nearer to the true answer. Admittedly the effect on the Earth itself of all those people jumping would be minimal, but where would the energy they had on landing go to?
    It was a commonly known 'fact' (note the quotes!) when I was a lad, that if all the Chinese people jumped up and down in unison, the Energy would create a large tidal wave engulfing the UK. This sounds like rubbish, but is there a possibility of creating a noticeable wave in the sea?

    The amount of assumptions, estimates and guesses that a problem like this would need to be solved, probably makes it unanswerable...... So I won't try! :smile:
     
  9. Oct 9, 2003 #8
    Didn't you get the Memo?? SHHHHHHHHH!
     
  10. Oct 9, 2003 #9

    Nereid

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    How much energy, from the first hammer blow, would be left in the returning wave? Let's say 1%. Then the second hammer blow would, in effect, be 1.01 (using the first as 1). And the third would be ... Mr Parsons, please hit harder.
     
  11. Oct 9, 2003 #10

    Nereid

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    And the fundamental frequency of a tectonic plate is ... wait, don't they have rather irregular shapes? So there must be more than one such frequency, right? Do you think it'd be a catchy dance rhythm (not)? [zz)]
     
  12. Oct 11, 2003 #11
    WOW you people ever miss that one, that littel guy was tapping out, in "MooseCode" the ToE, he actually got to do it twice for the time he was up there!
    Don't tell me that you people missed that completely?? DID ya??
     
  13. Oct 11, 2003 #12
    Of course there's a catchy rythm to their frequency... badgerbadgerbadger MUSHROOM MUSHROOM...

    but you guys know that like riddle about building a really big wall somewhere with like a bizillion tons of rock, how would that effect the earth? well, the answer was always, it wouldn't cause the rock came from earth. well, is that completely true? and what if instead of everyone jumping up and down, what if we all like fell off really high buildings, would that mess up the earth or something?
     
  14. Oct 11, 2003 #13
    Dunno about the earth, but it wouldn't do us much good.
     
  15. Oct 11, 2003 #14
    I think a neutron star would be a better conductor of sound waves than the Earth. The Earth is comparatively an oblate spheroid whose resonances are not necessarily constructive, whose relatively conglomerate and irregular composition would tend to dampen reverberation, and whose lower speed of sound indicates wider, dissipated radiation lobes.
     
  16. Oct 12, 2003 #15
    Humm someone who reads Moosecode, Hummmmm........
     
  17. Oct 12, 2003 #16
    What's a moosecode - rhinitis of an ungulate?
     
  18. Nov 7, 2003 #17
    Sound waves? Sound is accoustical. What does that have to do with Neutrons?
     
  19. Nov 7, 2003 #18
    Probably because seismic waves behave very much like sound waves, and the original question was about a topic that would have involved seismic waves, as in could we generate a big one if enough people jumped up and down at the same time, that kinda stuff.....
     
  20. Nov 7, 2003 #19

    chroot

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    Sound waves are just pressure waves in air. Any substance can support pressure waves, all of which could appropriately be called sound waves.

    - Warren
     
  21. Nov 7, 2003 #20

    NateTG

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    Let's take a look at the math for a second:

    Population of earth 6.0 * 109
    Avergate Weight 75 kg
    Jumping .5 m
    so that's a total energy of:
    9.8*75*.5*6.0*109=2.2 * 10 12 J

    Now, let's assume that the energy density of TNT is similar to diesel: 46 J per KG so that's 4.7 * 10 7 KG of TNT or about 47000 Tons TNT, which is roughly three times the size of the Hiroshima bomb.

    The US set off a 1.5 Megaton (30 times the energy) bomb in bikini and did not cause noticable disturbances in the mainland US.

    So the answer is, that it probably wouldn't cause any noticable disturbances.
     
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