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The Earth (and its inhabitants) is rotating and moving along with the Milkyway at approximately 600 000 m/h (not the of the Earth's rotation). Now let's say I'm in my spaceship in earth orbit watching the earth spin, I too would be traveling around 600 000 m/h (or 168 m/s) the same as the Earth, correct?

Now let me compare myself to a ball on a conveyor belt. From my view point I am stationary, but to an outside observer I am moving with the conveyor belt. Now lets say I(the ball) have some method of producing motion in the opposite direction of the belt; in effect, I now look stationary to the outside observer (and as to make the motion unnoticeable, the ball is completely uniform).

Back to my spaceship, what if I were to leave Earth's orbit and travel against the rotation of the galaxy enough to cancel out the effects of motion like the ball and conveyor belt and once at that point give no more means of motion. If all of this were to be correctly implemented, then:

  1. Would I effectively have no motion?
  2. Would I see the Galaxy traveling 600 000 m/h around me (assuming I would never hit something)?
  3. Would I experience time differently?
  4. If I would see the Galaxy moving, what would I see?
user34873
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1 Answers1

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Usually you should denote miles by "mi" and meters by "m" to avoid confusion. 600,000 Mi/h translates into 268km/s (kilometers per second) so I'll use that figure, and assume that it is the speed of rotation of the sun around the center of the milky way.

  1. You would have just as much "motion" as if you were in outer space, due to the principle of relativity. You would be in a freefall frame, and if you accelerated the 268km/s necessary so that you had no angular velocity with respect to the center of the milky way, you would start accelerating straight "downwards" (a very appropriate word in your new reference frame) towards the black hole at the center of the milky way.

  2. Yes, you would have accelerated and you would see the earth and sun wizzing away from you at 268km/s, as well as all the other stars doing the same thing as they continued their circular path around the milky way's core.

  3. No, everything would look and feel the same according to the principle of relativity. You would however, if you looked with a giant telescope, observe people on the earth to be moving slowly due to time dilation, and they would be redshifted according to the doppler effect. (technically the relativistic doppler effect) This is because the earth is now moving away from you at 268km/s.

  4. You would be able to observe the rotation of the galaxy for a short while, until you plunged into the center of the milky way and either got swallowed by the black hole, or more likely until you passed by the center and got kicked out in some other direction. (stars nearby might perturb your orbit enough that you don't fall straight into the black hole.)

Make sure that you're not thinking incorrectly that motion is Aristotelian. It isn't. In physical laws, there is no such thing as an absolute reference frame. (You can define a very special stationary reference frame using the cosmic microwave background but as far as I know it doesn't have any special properties affecting motion. Certainly not in the Aristotelian sense.)

  • So far I think this is giving me all the information I asked for and I am willing to accept this answer, but why would I start falling towards the black hole in the center? – user34873 Nov 29 '13 at 04:23
  • @user34873 We're always accelerating towards the center of the milky way. At some hundred kilometers per second we are in orbit and move in a circle. But with zero angular velocity we are not in orbit and the acceleration continues causing us to fall. It's like being in orbit around the earth: You'll stay in space if you're moving fast, but if you slow down you'll fall. http://what-if.xkcd.com/58/ –  Nov 29 '13 at 05:51
  • To point 4, the gravitational pull of the Milky Way at the Earth is only 200 pm/s^2 (that's 2 x 10^-10 m/s^2). If you stopped your rotation around the galactic center it would take you 12,000 years to reach the heliopause and 650,000 years to reach the next solar system at 4100 km/s. So you'll have some time. – Schwern Apr 01 '16 at 06:32
  • To point 3, 268 km/s is less than 0.001c. You wouldn't notice any time dilation nor relativistic Doppler effect on Earth. To point 2, while 268 km/s is about 10 times faster than the New Horizons probe, it's still pretty sluggish on interplanetary scales (120 hours to Mars) and practically snail-like on interstellar scales (5000 years to the next solar system). You wouldn't see planets and stars whizzing by. – Schwern Apr 01 '16 at 06:41