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Here's why any rotating perpetuum mobile device cannot work regardless of the principle (gravity, magnets, springs, balls, ...). Anything that moves on it's own

by dvh 5y ago

Here's why any rotating perpetuum mobile device cannot work regardless of the principle (gravity, magnets, springs, balls, ...). Anything that moves on it's own is moving because it is lowering it's potential energy. You start at 12 o'clock, and it moves to 3 o'clock because there, it will have lower potential energy. Then it continue to move but eventually it will reach the starting point (because it is circular). But you already know that potential energy there is higher, so the device will not move there because it wants to lower it's potential energy, not raise it. So any device that at some point reaches it's starting configuration cannot work because the potential energy is the same. If you put ball on flat plane it will not move sideways because potential energy is the same there.

forinti 5y ago
There's a large university in that town and it has a Physics department. Before this bloke spent his money building this thing, he should have called them up and asked them a few questions.
- ratww 5y ago
  At the end of the page it seems the university offered some unrequested advice on the second law of thermodynamics. It was dismissed on the grounds of the sun being "eternal" and gravity being an energy that can be "harvested" in the same way solar energy can.
  - vasco 5y ago
    They are right in the sense that you can count on the earth to pull your stuff down for free, they just forgot they have to put it back up themselves.
    - drran 5y ago
      Earth rotation and Moon orbiting can do a massive amount of work (see tide waves), but energy density is very low.
Const-me 5y ago
> because it is lowering it's potential energy. There’s also kinetic energy. The Earth rotates, and we have the Moon. It’s theoretically possible to build a machine which harvests energy from that rotation. Tides are powered by that energy, it’s obvious one could build a machine to extract energy from tidal waves in the ocean. It should be possible to build a machine which extracts that energy directly, without the water. Probably not practical because the energy density is too low, and the machine needs to be prohibitively massive.
- ac29 5y ago
  Tidal power is definitely a thing, and there are large commercial operations running today. The largest produces 552 GWh / year. See https://en.wikipedia.org/wiki/Tidal_power https://en.wikipedia.org/wiki/Tidal_power

by dvh 5y ago

forinti 5y ago

There's a large university in that town and it has a Physics department. Before this bloke spent his money building this thing, he should have called them up and asked them a few questions.

ratww 5y ago
At the end of the page it seems the university offered some unrequested advice on the second law of thermodynamics. It was dismissed on the grounds of the sun being "eternal" and gravity being an energy that can be "harvested" in the same way solar energy can.
- vasco 5y ago
  They are right in the sense that you can count on the earth to pull your stuff down for free, they just forgot they have to put it back up themselves.
  - drran 5y ago
    Earth rotation and Moon orbiting can do a massive amount of work (see tide waves), but energy density is very low.

Const-me 5y ago

> because it is lowering it's potential energy. There’s also kinetic energy. The Earth rotates, and we have the Moon. It’s theoretically possible to build a machine which harvests energy from that rotation. Tides are powered by that energy, it’s obvious one could build a machine to extract energy from tidal waves in the ocean. It should be possible to build a machine which extracts that energy directly, without the water. Probably not practical because the energy density is too low, and the machine needs to be prohibitively massive.

ac29 5y ago
Tidal power is definitely a thing, and there are large commercial operations running today. The largest produces 552 GWh / year. See https://en.wikipedia.org/wiki/Tidal_power https://en.wikipedia.org/wiki/Tidal_power