I was not sure just where to ask this question, but I was wondering if the sealed bottle garden be really called a perpetual motion machine.


It has its own isolated ecosystem, and can be self sufficient for years with only needing to water once.

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    $\begingroup$ As a general rule of thumb, there is no such thing as a perpetual motion machine. $\endgroup$ – Gimelist Aug 21 '16 at 8:22
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    $\begingroup$ Sunlight get into the bottle. Thus, it is not fully sealed from the outside world and is not self sufficient. $\endgroup$ – daniel.heydebreck Aug 21 '16 at 8:54
  • $\begingroup$ Downvoted, like all questions that depend on an unscientific premise — evidence from the bible, deluded conspiratorists, perpetual motion machines, etc. $\endgroup$ – kwinkunks Aug 22 '16 at 17:37

There are no perpetual motion machines.

So when you think you've found one, you need to ask a couple of questions, because there will always be an answer to at least one of them.

  1. How is the dissipation of energy being concealed? That is to say, some energy store is being depleted - where is it?
  2. Where is the additional energy coming from?

In this case, additional energy is coming from the light that enters the sealed bottle garden. If there's no light, there's no growth.


I think this is off topic - its physics; basic thermodynamics, to be precise. But EnergyNumbers is correct. Whenever there is a claim to perpetual motion, always take as close look at the total energy inventory, including infra-red, heat, light, UV, chemical, and radioactivity. Invariably, someone has either overlooked a component of the energy balance, or is not looking at a realistic time scale.


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