Perpetual Motion From Satellite Revolution

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Discussion Overview

The discussion explores the concept of harvesting energy from the revolution of nearby satellites, specifically using the Moon as an example. Participants examine the theoretical feasibility of such energy extraction and its implications, while acknowledging the limitations imposed by the laws of physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant proposes the idea of harvesting energy from the revolution of a nearby satellite, questioning its theoretical viability.
  • Another participant points out that extracting energy from an orbiting body would cause it to lose altitude over time, indicating that the scheme cannot be perpetual.
  • A participant acknowledges the impossibility of a perpetual motion machine but suggests that a long-term means of energy extraction could be possible.
  • One participant references tidal power as a practical example of energy extraction from the Moon, suggesting that energy is already being harvested from such celestial bodies.
  • Another participant argues that the energy expended to place satellites into orbit would exceed any energy gained from them, questioning the practicality of the proposal.
  • A participant emphasizes that the Moon is the largest object in orbit around Earth and discusses the significant tidal effects it has compared to any other potential satellite.

Areas of Agreement / Disagreement

Participants generally agree that while energy extraction from satellites is theoretically interesting, practical limitations and the laws of physics impose significant constraints. There is no consensus on the feasibility of the initial proposal, with multiple competing views presented.

Contextual Notes

Participants express uncertainty about the implications of energy extraction and the definitions of perpetual motion, highlighting the complexity of the topic and the need for careful consideration of energy balances.

LotoSage
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"Perpetual Motion" From Satellite Revolution

This is going to sound very far fetched, and I know very little about the laws of physics, admittedly (I don't even know if I'm posting this in the right area), but curiosity compels me.

I was wondering if it would be possible to harvest energy from the revolution of a nearby satellite as I've illustrated here: http://i.imgur.com/Z3u5i33.png

I use the moon as an example here, but that could be replaced with any nearby satellite. Would this work, in theory?
 
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I'm not sure what your sketch is trying to show. However, it is the policy at PF not to discuss PM and the like.

In any event, if you try to extract energy from an orbiting body, you are going cause that body to lose altitude over time. After all, it takes a fixed amount of energy per unit mass to put something into a particular orbit, so while your scheme may be long-lived, it cannot be 'perpetual'.
 
Yeah, that's why I put it in quotes. While my understanding of physics is very limited I felt of course it couldn't last forever. I don't literally mean PM in this case (and that goes twicefold since it's disallowed), but simply a long term means of energy extraction. You seem to have gotten the right idea from my rudimentary illustration, and I thank you for your input.
 
LotoSage said:
I use the moon as an example here, but that could be replaced with any nearby satellite. Would this work, in theory?
We are already extracting that energy in practice:
http://en.wikipedia.org/wiki/Tidal_power‎
 
We'd have to expend more energy putting the satellites into orbit than we'd get back, so there's no point.
 
LotoSage said:
I use the moon as an example here, but that could be replaced with any nearby satellite. Would this work, in theory?

It's all a matter of degree. The Moon is the largest object that will ever (could ever) be in orbit around the Earth. Any event that could introduce a comparable size of satellite would spell the end of the world for humans. Tidal surges or whaaaaat?

Tidal effects from the Moon (And the Sun, aamof) are many orders of magnitude greater than from anything else out there so those are the ones to go for. And we already do. From our point of view, the energy is 'inexhaustible' but it's not PM (verboten in PF).
 
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