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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1$\begingroup$ 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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2$\begingroup$ Sunlight get into the bottle. Thus, it is not fully sealed from the outside world and is not self sufficient. $\endgroup$ – daniel.neumann Aug 21 '16 at 8:54
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$\begingroup$ 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
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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.
- How is the dissipation of energy being concealed? That is to say, some energy store is being depleted - where is it?
- 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.
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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.
