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Digging hole through Earth

  1. Oct 5, 2004 #1

    Cal

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    Hello,

    Sorry if this is wrong section of forum. But i think its correct. :smile:

    Ok, so this has always baffled me. If you could dig a hole through the Earth until you reached the other side, would you come out feet first? Of course, you have to take out of account the fact you would burn to death from the Earths core etc. Now of course this may sound stupid. But i have never understood it.

    Could anyone of you people shed light on this theory?

    Many Thanks in advance.

    :smile:
     
  2. jcsd
  3. Oct 5, 2004 #2
    I suspect you would come out shovel first.
     
  4. Oct 5, 2004 #3

    chroot

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    Gravity will always pull you toward the center of the Earth. Once you passed the center of the Earth, gravity would be pulling you up, through the hole you've already dug above you, not down. I suspect you'd have to change your shovelling posture considerably.

    - Warren
     
  5. Oct 5, 2004 #4
    I dont see how he could continue shoveling up b/c there would be nothing to stand on after he had passed center, except the hole he had just dug. You would have to be not only shoveling but also climbing at the same time.

    Nautica
     
  6. Oct 5, 2004 #5

    chroot

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    nautica,

    That was basically my point. :wink: You dig down till you get the center -- then you have to starting digging up.

    - Warren
     
  7. Oct 5, 2004 #6

    Gokul43201

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    You stick your legs outwards and pin yourself against the walls of the hole with friction. Or you carry a spring loaded jack to span the hole. You then straddle this, close your eyes and dig upwards.

    You could dig downwards too, but you'll have to wrap your legs around the jack and be hanging upside down.
     
  8. Oct 5, 2004 #7

    chroot

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    Either way, if I'm ever offered a job digging a hole through the earth, I'll probably turn it down.

    - Warren
     
  9. Oct 5, 2004 #8

    Gokul43201

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    Even if your life's ambition was to get to China ??!!
     
  10. Oct 6, 2004 #9
    my favorite bit about digging through the earth has always been that if you had a hole that went all the way through (pre-dug by a team of very fit dwarves, none of whose name is chroot) and you jumped in the hole you'd accelerate until you passed the middle and would then decelerate until you got to the other side china (er, australia), so you could take a step forward just as you got to the other side and be on standing on the ground. with no excess vertical velocity. and you would end up coming out feet first, unless you'd started with a some angular momentum and rotated on the trip down (and up). anyway, it's a nice consersvation of potential energy idea.

    of course we are assuming things to be convenient to our desire to easily(?) travel through the earth such as: a vaccuum through our hole, thus no air friction, thus no terminal velocity. oh, and no very very very hot molten stuffs in the inbetweens. etc, etc.
     
  11. Oct 6, 2004 #10
    Adding two cents to the conversation.

    How long would it take to complete that fall up and down that hole, assuming no drag/friction and how would that compare to a theoretical orbit time of a satellite at Earth Surface level?
     
  12. Oct 6, 2004 #11
    Hey, I remember that problem from classical mech! If memory serves me, they are the same. I hope I'm remembering right, cause otherwise I'll have to get the pen and paper out :D
     
  13. Oct 6, 2004 #12
    Yep, I believe someone was already offered the job back in the 50's or 60's. They were going to start at the bottom of the ocean. Then after millions of dollars were spent with only an 80 foot test hole to show for it they were fired. If my memory serves me correct the feasibilty study and the test hole cost more than the original estimates of the entire project.

    An these people just wanted to get to the core. It would have really been exciting if they would have tried to dig out the other side.

    Nautica
     
  14. Oct 6, 2004 #13

    Cal

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    Thanks for all your replies people. I think i now understand it better. But, unless its actually attempted (which it proably never will) we would never know. All we have unfortunantly are theories. :frown:
     
  15. Oct 6, 2004 #14
    No, it is a bit more than a theory, it is the law of gravity. Which says and has been proven that gravity starts at the center of the mass, not in the outer areas of the mass.

    Nautica
     
  16. Oct 6, 2004 #15

    Integral

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    Operation Mohole?
     
  17. Oct 6, 2004 #16

    arildno

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    Dearly Missed

    I think the time down and back again would be approx. 42 minutes
    (Or was that just one-way?)
    Whatever the truth, 42 is definitely the answer to lots of stuff..
     
  18. Oct 6, 2004 #17
    Yep, if my memory serves me correct. It was headed by Hess. They were digging through the crust to study the history of the earth, continental drift, flow of heat from the interior, and formation of mineral resources. They planned to drill 18,000 feet, but the deepest hole ever dug before that time was only around 100 feet.

    They asked the NSF for around $30,000, but were funded almost $80,000. After more money was spent it was turned over to Brown & Root, who had some connection with the government. The fiinal estimate I believe was around $67 Million and I don't exactly remember how much was actually paid to Brown & Root, but it was alot.

    Finally, congress put a stop to it in the late 60's.

    Big Science at its best.

    Nautica
     
  19. Oct 6, 2004 #18

    Gokul43201

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    I second that. It looks like the time period of oscillations is independent of the path taken by the tunnel joining two fixed points on the surface...unless I'm making a mistake somewhere.

    That's neat ! :cool:
     
  20. Oct 7, 2004 #19

    Integral

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    This would be especially nice to know when you are digging your way back up.... So you could duck when a shovel full of dirt comes back to you!
     
  21. Oct 26, 2004 #20
    I have a question about this. Suppose you did dig a hole and jumped into it, you would float in the center right? But... would you be crushed to death by the gravity?
     
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