Perpetual motion is everywhere in space. Using that motion for doing work will always change the motion, and it will eventually no longer be useful. This is what a perpetual motion machine tries to do but can not.
If something could rotate infinitely after being initially pushed, would the initial push disqualify it from being classed as perpetual motion?
Submitted 2 weeks ago by Anchorxiety@reddthat.com to [deleted]
Comments
mvirts@lemmy.world 2 weeks ago
Nomad@infosec.pub 2 weeks ago
AFAIK even space will cool down and stop eventually. So not perpetual motion very low friction motion? I know that expansion also plays a role.
bufalo1973@piefed.social 2 weeks ago
If you think about it, when the universe cools down, maybe some rocks will fly forever without hitting anything.
AbouBenAdhem@lemmy.world 2 weeks ago
“Perpetual motion” is a bit of a misnomer—it’s only a violation of the second law of thermodynamics if the system is losing energy to friction (or if you try to extract energy from it).
jeffw@lemmy.world 2 weeks ago
This would work perfectly… if we lived in a vacuum
gedaliyah@lemmy.world 2 weeks ago
No, if something rotated infinitely, that still violates thermodynamics and is “perpetual motion.”
This of course is impossible. Even the Earth slows down by about 2 ms per century due to tidal forces.
FuglyDuck@lemmy.world 2 weeks ago
“Due to tidal forces”
Because, the moon (and maybe the sun, and other planets like Jupiter) are acting on it, yeah?
The earth won’t stop spinning. What’s happening is that the moon’s gravity is slowing the earth’s spin as it drags our oceans towards it.
Once our day is the same as the moon’s orbital period, then the tide will essentially be fixed, which means it’s no longer slowing us down.
And all that energy, for the record, is going into the moon and expanding its orbit slightly.
gedaliyah@lemmy.world 2 weeks ago
Yes, although quantum effects also slow spinning celestial objects/systems, even in the absence of measurable tidal effects. That would take much, much longer to slow down.
sylver_dragon@lemmy.world 2 weeks ago
If something could move forever, without further input of energy, then yes, that’s perpetual motion. We just haven’t found anything which will do that yet and out best models for describing the universe hold that it’s impossible.
HubertManne@piefed.social 2 weeks ago
Given no external influences that is actually just normal behavior. In a vaccum away from any gravitational influence or such once you push something it should keep going. Thats conservation of momentum. Air resistance and such is why things stop.
Nemo@slrpnk.net 2 weeks ago
no, only if it has to be re-pushed periodically