Perpetual Motion and the Laws of Thermodynamics

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Discussion Overview

The discussion centers around the concept of perpetual motion in relation to the laws of thermodynamics and the expansion of the universe. Participants explore the implications of these concepts, particularly how they relate to the speed of light and the nature of motion in an expanding universe.

Discussion Character

  • Conceptual clarification
  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the impossibility of perpetual motion in light of the universe's accelerating expansion, suggesting a potential contradiction with thermodynamic laws.
  • Another participant asserts that the universe is not expanding faster than the speed of light, explaining that if it were, light from distant galaxies would not reach us.
  • A different participant clarifies that relative to any observer, nothing is moving faster than the speed of light, emphasizing the importance of definitions in discussing motion and speed.
  • One participant introduces an analogy involving a balloon to illustrate that objects in the universe are not moving away from each other faster than light; rather, the distances between them are increasing due to the expansion of space itself.

Areas of Agreement / Disagreement

Participants express differing views on the relationship between perpetual motion and the expansion of the universe. While some agree on the definitions of motion and speed, others challenge the implications of these definitions in the context of thermodynamics and cosmic expansion. The discussion remains unresolved regarding the interpretation of these concepts.

Contextual Notes

Participants rely on various definitions of motion and speed, and there are unresolved assumptions about the nature of expansion and its implications for perpetual motion. The analogy used to explain cosmic expansion may not fully capture the complexities involved.

binbots
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How come we say perpetual motion is not possible according to the laws of thermodynamics. Yet our universe is expanding faster and faster. How can we say nothing is faster than the speed on light but the universe expanding is? Keep it simple please.
 
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The universe is not expanding faster than C. if it were, light from distant galaxies would never reach us because the space between them would grow faster than the light could cross it.

As for perpetual motion, It is not the same as a force. We do not know why the universe is expanding faster and faster, but it seems to be due to some accumulating acceleration. We do not say an orbiting satellite is perpetual motion, yet it perpetually moves. Be careful with the definitions.
 
I think what bin is asking is that if it is expanding at any rate, wouldn't it eventually exceed the speed of light far enough away. The answer is no, relative to any observer in the universe nothing is moving faster than the speed of light.

Speed is distance over time, but take the time of any relative object and you get

[tex]t' = \frac{t}{1-\frac{v^2}{c^2}}[/tex]

So

[tex]\frac{d}{t'}[/tex]

will never exceed c where c is the speed of light.
 
Back in one of my astro classes my professor tried to explain that what's happening is that the objects aren't 'moving' away faster than the speed of light, but instead, the distance between the objects is getting longer! kind of like drawing two dots on a balloon and filling it up, they aren't moving with respect to the balloon, but are becoming farther apart due to its expanding nature. now, obviously this balloon example is wholly crude, but the point is that it's not that the objects are moving, but instead, the way we perceive distances have changed and are changing with respect to time. i hope this helps.
 

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