I saw a video some days ago (Hello Kitty in Space) of a schoolgirl successfully launching a balloon into space which later popped and landed ~47 km from launch site.

If I vertically launch an object (say via balloon or rotors) from the surface of a spinning planet with an atmosphere like ours, then as it rises, will the planet's surface move away below it, or will the object rotate with the earth? (Assume that there are no local strong winds relative to the atmosphere, and it is completely calm.) The latter would mean the atmosphere, being itself a collection of such objects (air molecules), also spins with the planet.

Related SE question: Why does the atmosphere rotate along with the earth?

It seems from common sense that since at launch the object shares the motion of the surface it would keep rotating with the planet, and hence would later land at the launch site. However, as it ascends, the lateral speed required to maintain the same angular velocity with the planet rises linearly. Where would it get this extra momentum/energy from? From the rotating atmosphere? How did the atmosphere get moving in the first place then?

It might seem a lot of questions for a single SE post, but they're all connected, so a single explanatory answer should suffice.

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    $\begingroup$ One word: drag. $\endgroup$ – Michael Brown Feb 18 '13 at 10:18
  • $\begingroup$ @MichaelBrown, so essentially the object gets the energy from the atmosphere via drag? Where did the atmosphere get its motion from? The surface? All the way up to the top? And you see there needs to be constant feeding of energy to maintain this motion. Could you please elaborate a bit? $\endgroup$ – Abhranil Das Feb 18 '13 at 10:21
  • $\begingroup$ Possible duplicate: physics.stackexchange.com/q/1193/2451 $\endgroup$ – Qmechanic Feb 18 '13 at 13:14
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    $\begingroup$ Try this question physics.stackexchange.com/questions/1193/… $\endgroup$ – Michael Brown Feb 18 '13 at 13:14
  • $\begingroup$ @Qmechanic oops sorry :) $\endgroup$ – Michael Brown Feb 18 '13 at 13:15

The planet does rotate relative to the balloon (Like in Focoult Pendulum) This happens because there is no such a thing as inertial acceleration. That should answer your first question, and this line of thinking should answer others.

If not, please write to me, I'll do my best to clarify.

I had a very similar confusion/multiple question, while trying to understand working of Focoult Pendulum.

  • $\begingroup$ While I can of course write to you (because I know you), it would help if you laid out the answer more completely right here, in the spirit of this website. (This post is supposed to be helpful for anyone who thinks of this question and arrives here.) $\endgroup$ – Abhranil Das Feb 18 '13 at 13:04

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