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Why is the earth constantly rotating, but we as humans can never feel it?

  1. Jul 26, 2006 #1
    I don't understand why we can still go about with our lives, and stay stuck on this earth while the earth is actually moving. Why does this not affect us?
  2. jcsd
  3. Jul 27, 2006 #2
    I can feel it every night that I peak up at the beautiful stars and watch them slowly seem to drift across the sky... when in my mind I know that the earth is really rotating. There is a force that hasn't fully been figured out yet called gravity that keeps us grounded. It does effect us... from seasons to night and day and beyond.
    Last edited: Jul 27, 2006
  4. Jul 27, 2006 #3
    I hear that the Earth's crust is also divided up into sections that move around, but I don't feel them moving. I'm in the Midwestern US, and I have never even felt the slightest tremor.

    I guess it's because I'm on top of one of the sections at an area where it's very stable and I move along with it. And as I move along with the section, the stability goes with me!
  5. Jul 31, 2006 #4


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    Everything is relative. If you are moving at forty-five miles per hour in your car, do you feel like you are moving? Only when you accelerate to it. This is because you are moving forty-five miles per hour along with your car, so the difference is zero. You feel zero. When you are sitting in front of your computer screen on Earth, you are moving at the same speed in the same direction as the ground. Therefore the difference is zero. You feel zero.
  6. Aug 2, 2006 #5


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    The sections (Plates) move at about the speed your fingernails grow, so unless they go with a bit of a jolt (ie. an earthquake) you're not going to feel a thing.
  7. Aug 2, 2006 #6


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    1] We don't feel constant motion (such as in a train going straight), but we do feel accelerated motion (such as in a train going around a curve).

    2] While the Earth's straight-line motion is pretty fast (you are moving East at between 500 and 1000 mph), it's angular motion is pretty small because Earth is so large. Pick up a tennis ball and rotate it as fast as the Earth turns: after an hour you will have only turned it by a half inch.

    3] The only way to feel this kind of motion is to be very large. Air masses are large enough to feel this rotation - that's why they curve into rotating storms. This is called the Coriolis Force.
  8. Aug 2, 2006 #7
    But I still don't feel earthquakes when they happen, since I'm no where near the edge of the plate. It's like Galileo on a ship with a bunch of butterflies in boxes and... oh nevermind. :redface:
  9. Aug 6, 2006 #8


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    additional quesiton:

    Does the earth's rotation speed vary? Wouldn't we feel it if the earth accelerated enough?
  10. Aug 6, 2006 #9
    Is there anything constant in the movements of the Earth? The spinning for instance, or the length of day is changing in cycles with micro seconds a day


    But forces associated with those perturbations are a few dozen orders of magnitude smaller than gravity, so there is nothing to notice.
  11. Aug 13, 2006 #10


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    but is the buttefly effect applicable? What if, at a peak in the magnitude of the jerks, I was involved in an extremely calculating coordination, like spinning around and making a shot around an opponents arms, and the little disturbance is enough to throw me off and knock me over, and i'm like "man I must be off my game today" but it's really the earth's fault. I KNEW IT!
  12. Aug 13, 2006 #11


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    In a word, no.

    And even if it actually could happen, it wouldn't seem like "a little disturbance". Think about how the energy of that jerk would be transferred through the Earth's mass. No, it wouldn't be a little disturbance, it would be the mother of all Earthquakes.
  13. Aug 30, 2006 #12
    Indeed, relative motion is the key.
    To actually feel/see the difference between equatorial an polar earth rotation speed, you need sensitive instruments like an accelerometers. Then rapid North-South motion will defiantly register on an East-West mounted accelerometer.
  14. Nov 22, 2006 #13

    Andrew Mason

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    The earth is in orbital freefall around the sun (and around the earth moon centre of mass). According to Einstein's principle of equivalence, gravitational freefall is equivalent to an inertial (non-accelerating) frame. So there is nothing to feel.

  15. Nov 23, 2006 #14


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    Acually free fall only equals inertial in the small limit. For extended objects there are tidal forces. And the earth is also spinning which is quite noninertial and which generates forces (centrifugal and coriolis) that we DO feel! We feel coriolis, when combined with the solar input and the thermodynamics of the atmosphere, as weather. Think of that when you're shoveling four inches of earth-spin off your driveway.
  16. Nov 24, 2006 #15
    You don't just get e'quakes at plate boundaries ya know (okay predominantly you do but..) about a hundred years ago therre were some pretty big tremors in the New Madrid region in central USA, you anywhere near there coz some think it might happen again.
  17. Jan 6, 2007 #16
    Its like when you are driving at the same speed as other cars on the highway, they are all standing still with respect to your car.. Everything else thats not spinning with us, is just so far away that it doesn't create for much of a motion blurring effect like youd expect going at thousands of miles an hour.
  18. Jan 7, 2007 #17


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    10 char
  19. Jan 7, 2007 #18

    D H

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    You do feel the effects of the Earth rotating on its axis. It reduces the gravitational acceleration toward the Earth by a small amount. A person is heavier at the North and South Poles than at the equator. g is 9.78039 m/sec^2 at the equator, 9.83217 m/sec^2 at the poles. The rotational effect at the equator, 0.034 m/sec^2, accounts for about 2/3 of the difference in g values.
  20. Jan 7, 2007 #19


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    That's not quite the situation. Rotation is accelertion (rotational speed is constant but velocity direction changes) so we do "feel" the earth's rotation. As D H said, it causes us to feel slightly lighter.
  21. Jan 8, 2007 #20


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    If this were true, all the water in the world would pool around the equator.
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