Ball Thrown Up Follows Curvature of Spacetime

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Discussion Overview

The discussion revolves around the behavior of a ball thrown upwards in relation to the curvature of spacetime. Participants explore the implications of spacetime curvature on the ball's trajectory, questioning whether it could rise again after descending due to gravitational effects. The conversation touches on theoretical aspects of gravity, spacetime, and the influence of mass on curvature.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants propose that a ball follows the curvature of spacetime, leading to the question of whether it could ascend again before hitting the ground if the curvature changes direction.
  • Others challenge the idea of upward curvature, asking for clarification on how such a curvature could exist in the context of gravitational fields.
  • One participant suggests that if a sufficiently large mass were placed directly overhead, it could theoretically alter the curvature of spacetime to redirect the ball's path away from the Earth, although this scenario is deemed impractical.
  • Another participant argues that under normal circumstances, the curvature caused by the Earth will always direct the ball towards its center, emphasizing that additional mass is required to change this curvature.
  • There is a discussion about the analogy of a toy car and a vase to illustrate the concept of curvature, with questions raised about why a vertically thrown ball remains directly overhead rather than moving forward in a curved path.

Areas of Agreement / Disagreement

Participants express differing views on the possibility of upward curvature and the behavior of the ball in relation to spacetime. No consensus is reached regarding the mechanics of the ball's trajectory and the implications of spacetime curvature.

Contextual Notes

Limitations include the speculative nature of the proposed scenarios and the dependence on hypothetical arrangements of mass to alter spacetime curvature. The discussion remains focused on conceptual exploration without resolving the underlying physics.

rajeshmarndi
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A ball thrown up comes down again because the ball follows the curvature of spacetime. So is it possible that the ball comes down and before hitting the surface, goes up again due to curvature of the spacetime,which now point upward.
 
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rajeshmarndi said:
curvature of the spacetime,which now point upward

Why would the curvature point upward?
 
rajeshmarndi said:
A ball thrown up comes down again because the ball follows the curvature of spacetime. So is it possible that the ball comes down and before hitting the surface, goes up again due to curvature of the spacetime,which now point upward.

Sure, if you can arrange to curve spacetime in such a way that the curvature carries the path of the ball away from the surface of the earth. You could do that by arranging to fix a mass much larger than that of the Earth directly overhead. You don't even need any general relativity to do this, ordinary classical Newtonian gravity will describe this (completely impractical and unrealistic) setup just fine.

But if the Earth is the only large mass in the area, the curvature will be such that the ball's path heads towards the center of the earth. Mass and energy are what curves spacetime, so you won't get a different curvature unless you introduce another large mass into the picture.
 
PeterDonis said:
Why would the curvature point upward?
hatstarter.jpg

Like in the picture, if the toy car is driven upward, when it goes to the other side, it comes down. Likewise if the line in the picture is high enough, when it can go up and come down, couldn't while it is coming down, couldn't it rise up again.

Also why is that the ball thrown vertical, always remain overhead us and do not go ahead from us in the curve path.
 
rajeshmarndi said:
hatstarter.jpg

couldn't while it is coming down, couldn't it rise up again.
Nope. The path always tends towards the wider part. Get a vase, some adhesive tape, a try it out. Stick the tape as straight as possible around the vase, without tearing or folding it.

To come back it would have to fall through the Earth to the other side, where the curvature is the other way around, like shown here:
http://www.adamtoons.de/physics/gravitation.swf

rajeshmarndi said:
Also why is that the ball thrown vertical, always remain overhead us and do not go ahead from us in the curve path.
This diagram only has the vertical space dimension in it, so it can only show a vertical trajectory. The other dimension is time.
 

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