Perpetual Motion. Real? ...-ish?

I know.  I know. There's no such thing as true perpetual motion, but...

How close have we come?

Mag-lev?

Edit:  ...and how close can we get?

The closest thing we have come to that is the motion of the universe.

Apparently you need very high-end equipment to prove that a Formula E motor's efficiency isn't violating the laws of physics.

obligatory:

Interesting:

https://www.popularmechanics.com/science/energy/a39372219/self-charging-infinity-train/

Of course nothing is "free" but for all intents and purposes this is close.

Closest thing to perpetual motion:

   Any object moving through a vacuum (space).  

Effectively perpetual (as long as it doesn't hit anything)

Also of note: if you allow conversion of the energy of motion to other forms of energy (e.g. heat) all motion is perpetual.  Even gravity (the most likely thing to affect something moving through space) is simply a "sharing" or merging of energy with nothing lost.

In reply to aircooled :

The problem is us meat-brains want to do work (in the mechanical sense) while losing precious heat to entropy.

Y'all are wrong. Perpetual motion exists and can be proven. My bank account. The balance is perpetually moving down. 

I think we need to properly define perpetual motion here.

Objects moving through space demonstrate a good conservation of energy, but it is not perpetual motion in any way.  Perpetual motion requires that the energy output is greater to equal to the energy input.  Since objects in space were set in motion by a very large exothermic reaction and have yet to encounter enough resistance to overcome their kinetic energy (inertia), it is in fact an exact demonstration of non-perpetual motion.

The only reason celestial objects in space could be called perpetual motion is if they have encountered an equal counterforce as their initial propulsion and are still moving.  That is to say, if you throw a tennis ball in space with 20lbs of force, it will continue moving until it encounters a total of 20 lbs of resistance - space dust, tardigrades, phaser blasts, etc.  When it encounters those objects is it outputting some of its energy by giving kinetic energy to the speck of dust.

dimarra said:

I know.  I know. There's no such thing as true perpetual motion, but...

How close have we come?

Mag-lev?

Edit:  ...and how close can we get?

Maglev fits the definition of conservation of energy, not perpetual motion.  A massive amount of electrical energy is required to generate the force.  Mag-lev is (at best) a low-friction alternative ot axles, wheels, and bearings, but it expends more energy generating motion than you get back in the motion itself.  That is to say, you might expend 1kJ of energy for every 0.75 worth of thrust generated.  The rest is wind resistance, electrical resistance, etc.

In reply to Curtis73 (Forum Supporter) :

That's a pretty tight definition of perpetual motion- which literally is motion that doesn't stop.   If you want to add some constraints to the simple literal definition, that's fine.  But the meaning is just motion that is never ending or changing- and since the big bang, the universe as a whole has been moving for as long as time has been part of physics.  Sure, you can find examples of specific objects that slow down.  Still, space is the closest we have gotten to perpetual motion, and even that isn't.  

Your definition is a good one for motion on our planet, I suppose.  If it were a perpetual motion *machine*, then yea....

Perpetual motion is what the "brown's gas" crew attempted to peddle in the 90s.  Take water, use energy to split it into hydrogen and oxygen, then burn it to re-form water.  In essence they were taking exhaust, converting it to fuel, and then back to exhaust.  Even in a 100% flawless situation with zero other losses, the best they could hope to achieve is zero net energy.  In truth, there are losses at each conversion... big losses, especially considering the ICE they were using.

Notice this graph.  This is how I demonstrate the brown's gas or HHO snake oil.  The graph on the right shows a demonstration of how water is converted into H and O.  The graph on the left shows the combustion when you recombine them into water.  You have to expend as much energy (red) to get the water into fuel as you get back by re-combining it.  This eschews the losses along the way.  This chart only shows the amount of energy required to make things happen, not how much is actually expended.  This is why perpetual motion can't exist.  Ever.  People start talking about catalysts, or really efficient electrical generation, but it doesn't change the atomic facts of how much energy is required to accomplish something (or how much energy you get back when you go the other way.)  The catalyst simply assists in the energy source and transfer.

alfadriver said:

In reply to Curtis73 (Forum Supporter) :

That's a pretty tight definition of perpetual motion- which literally is motion that doesn't stop.   If you want to add some constraints to the simple literal definition, that's fine.  But the meaning is just motion that is never ending or changing- and since the big bang, the universe as a whole has been moving for as long as time has been part of physics.  Sure, you can find examples of specific objects that slow down.  Still, space is the closest we have gotten to perpetual motion, and even that isn't.  

Your definition is a good one for motion on our planet, I suppose.  If it were a perpetual motion *machine*, then yea....

Sorry to disagree, but the term perptual motion is not used in the literal sense.  Perpetual motion is a term in physics defined as being one of three hypothetical thermodynamic systems.  This is often confused with a perpetual motion machine... which is a machine that operates (hypothetically along one of the three thermodynamic systems) without regard to the first or second (or both) laws of thermodynamics.

Perpetual motion is a thermodynamic system that violates the laws of physics.  A perpetual motion machine is a colloquialism that stemmed from inventors trying to capitalize on the three systems outline as: (copied and pasted cause it's easier)

• A perpetual motion machine of the first kind produces work without the input of energy. It thus violates the first law of thermodynamics: the law of conservation of energy.
• A perpetual motion machine of the second kind is a machine that spontaneously converts thermal energy into mechanical work. When the thermal energy is equivalent to the work done, this does not violate the law of conservation of energy. However, it does violate the more subtle second law of thermodynamics (see also entropy). The signature of a perpetual motion machine of the second kind is that there is only one heat reservoir involved, which is being spontaneously cooled without involving a transfer of heat to a cooler reservoir. This conversion of heat into useful work, without any side effect, is impossible, according to the second law of thermodynamics.
• A perpetual motion machine of the third kind is usually (but not always) defined as one that completely eliminates friction and other dissipative forces, to maintain motion forever due to its mass inertia (Third in this case refers solely to the position in the above classification scheme, not the third law of thermodynamics). It is impossible to make such a machine, as dissipation can never be completely eliminated in a mechanical system, no matter how close a system gets to this ideal (see examples in the Low Friction section).

But the important part is that "perpetual motion" (which is what the OP asked) is the thermodynamic system in which physical laws are violated.  It has nothing to do with actual motion or machines.  The term perpetual motion machine is a physical, kinetic entity that attempts to capitalize on the existence of a magical world where these laws can be violated.

I'm assuming from the OP's phrasing he was talking about the thermodynamic system, not a physical machine.  The thermodynamic system's concept of PM is any system in which the potential or kinetic energy available FROM as system is equal to or greater than the potenial or kinetic energy you add TO the system.  It can apply to chemical reactions, stones rolling up hills, HHO, or any system.  PM is a concept.  A PM Machine is a colloquial term for a physical item attempting to break the laws of physics.

Also, in your universe/big bang concept, that also displays a system of conservation of energy, not perpetual motion.  The gravity of the universe will eventually cause an equal and opposite force on the expansion, eventually pulling it back into one big ball of stuff.  Think of it like one of those balls on a rubber band tied to a paddle.  You are expending equal energy to propel the ball away from the paddle as the rubber band exerts to bring it back.  There is also and immense amount of energy propelling (and collapsing) the universe, so it is not perpetual unless we look at the current slice of time.  Right now it appears to be these balls of matter zooming through space, but there was considerable energy making them move and an equal energy pulling them back.  Not perpetual motion.... at least not within the physics definition of perpetual motion.

In reply to GeddesB :

I think you've come about as close to perpetual motion as it gets.

Magnets and gravity are two forces that almost violate the laws of physics.

Way back someone on rx7club looked at electric water pumps and had the idea of using an electric motor to drive the alternator.

Yeah.

He claimed that the car had 14v running.  So the alternator WAS functioning as a voltage step-up device, which is still better than running 12v in a full-loss drag car.  But the part that makes my brain hurt.  Obviously the motor would take more power to turn the alternator than the alternator could generate.  This power could only be coming from the battery.  But if the system voltage was 14v, how could the battery be discharging?