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How space works:Why does an asteroid crush a human in space?

  1. Jul 15, 2015 #1
    I hve a question: IF there is no air resistance or ANY type of resistance in space, then how come an asteroid or fast moving object can crush a persons face in space (like in the movie: Gravity)

    My logic is the following:

    If you imagine a spring extended in space, and a fast moving ball hits the spring in one end, does the spring compress? If it does compress then there must be something in the other end of the spring (space) pushing against it right? Why would a spring compress if there is no resistance in the opposite side of impact? I would imagine the spring would just move. Even if you had one fragile egg in space and another egg moving 1000m/s crushing into the stationary egg,I would imagine both eggs would just move at half the speed of the 1 egg (the moving egg transmits ½ the movement onto the other), because IF there was no resistance in space then Could you not imagine this scenario: (This discription is happening in a split second)

    1. The outer atoms of the edge of the fast moving egg, A, touch against the outer edge of the stationary egg ,B, this gives the egg a bit of movement. Now egg B is moving at 10th the speed of the the moving EGG, and the moving egg is loosing 1/10th of it's speed.
    2. Egg B is still slower than Egg A,and Egg B keeps pushing harder and harder against Egg A (in a nanosecond) until they are moving at the same speed (because they are the same size, however the force of impact did not crush egg B or A because there is no resistance pushing in the opposite side of impact on egg B, so nothing is forcing the shell to crack from the opposide side of the impact site.)

    Are there any experiments confirming or explaining this?
  2. jcsd
  3. Jul 15, 2015 #2


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    F=ma still applies in space. Mass has inertia, which makes larger masses harder to accelerate (or decelerate) than smaller ones.

    What you describe is conservation of momentum, which is true but a different issue from whether the objects can survive the impact.
  4. Jul 15, 2015 #3


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    As russ has pointed out, the issue here is momentum. Do you think air pressure has any significant role in what happens if a baseball batter gets hit in the head by the pitch? Whether his head is in the ballpark or in space, it doesn't want to move as fast as the ball wants it to move.
  5. Jul 15, 2015 #4


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    Do you really think that if a car hits you on the road, it needs the (almost negligible) air resistance behind you to get injured? The air resistance can be ignored for a collision like that. The car may break your leg because, as you yourself note, in a fraction of a second the impact will accelerate you rapidly with a huge force.

    Physics has to do with the real world. You are using your basic knowledge of physics to lose touch with the real world and how it works, rather than enhance your knowledge of how things work.
  6. Jul 15, 2015 #5


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    How can the other end accelerate, when no force is applied to it, because the spring isn't compressed at all.

    Last edited: Jul 15, 2015
  7. Jul 15, 2015 #6


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    Back up a bit. This whole thing is extremely puzzling. Do you mean that if this occurs on earth,ie. with the presence of air resistance, then you don't have any problem with it? For example, if I throw a 100 km/hr baseball into your face, you understand why it smashes your face if this happens on earth, but you don't understand why it still smashes your face if this were done in space, in vacuum?

    Did I interpret this starting point correctly?

  8. Jul 15, 2015 #7


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