Perpetual Motion

[sinsanity2006]

Would a perpetual motion machine be disqualified by the fact that the sun will someday go supernova then become a black hole causing the machine to be destroyed?

Would a perpetual motion machine be disqualified because the earth will one day fall out of orbit and crash into the sun?

Would a perpetual motion machine be disqualified because one of it's parts would wear out. For example if it uses a gear and over thousands of years the gear wears out?

Thanks in advance.

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Most of the things worth doing in the world had been declared impossible before they were done. ~ Louis Brandeis

 

[Ripley Twenty-Nine]

Would a perpetual motion machine be disqualified by the fact that the sun will someday go supernova then become a black hole and destroy it?

Would a perpetual motion machine be disqualified because one of it's parts would wear out. For example if it uses a gear and over thousands of years the gear wears out?

Thanks in advance.

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Most of the things worth doing in the world had been declared impossible before they were done. ~ Louis Brandeis

Be disqualified by what? The Million Dollar Challenge? If that's your question, then yes, James Randi would require that your Perpetual Motion Machine run until the end of time.. Another fiendishly clever way of him getting out of paying the million dollars.

 

[Captain Trips]

I think your answers, in order, would be "no" and "yes."

If you can show no loss of motion for the next 5 billion years (the expected remaining life before nova of the sun) then I think it can be expected that it would keep going longer.

If a part were to wear out, that would be a result of a "loss due to friction" -- and friction implies a loss of energy, which is contrary to the definition of "perpetual."

 

[Squishua]

Would a perpetual motion machine be disqualified ...

A perpetual motion machine is already disqualified because there's no way for it to work without violating the known laws of thermodynamics.

If you can overcome thermodynamics and construct a working perpetual motion machine, then you will win the $million (plus a whole lot more). They won't even wait until the sun goes supernova to pay you.

Best of luck!

-Squish

P.S. The sun will not become a black hole because it is not massive enough.

 

[Starthinker]

I think that since the universe - the largest machine in existance - will one day end then anything in it will be disqualified.

 

[Orangutan]

The gist of any test that would qualify a PM for the $1M prize would be that it produces more energy than it consumes. You'd have to deal with the JREF as to the specifics of establishing this fact. Fortunately the JREF $1M would be a trifle, if you can build such a machine you would well positioned to become a multi-billionaire.

 

[fuelair]

A perpetual motion machine is already disqualified because there's no way for it to work without violating the known laws of thermodynamics.

If you can overcome thermodynamics and construct a working perpetual motion machine, then you will win the $million (plus a whole lot more). They won't even wait until the sun goes supernova to pay you.

Best of luck!

-Squish

P.S. The sun will not become a black hole because it is not massive enough.

Chandrasekhars' limit. Just because I like using it!! (re.S.)

 

[Dr Adequate]

If a part were to wear out, that would be a result of a "loss due to friction" -- and friction implies a loss of energy, which is contrary to the definition of "perpetual."

That wouldn't be a problem if it's the sort of PMM that generates energy. And in that case, I think such a device would be acceptable even though its bearings might eventually wear down, or what-have-you.

 

[Steven Howard]

If you had a perpetual motion machine that produced free energy, would you even need to worry about the sun burning out? Seems to me that with unlimited free energy, you could just make a new sun.

 

[Ziggurat]

P.S. The sun will not become a black hole because it is not massive enough.

Furthermore, even with stars that ARE massive enough to become black holes, their event horizons MUST be smaller than their diameters, so gravitational collapse to a black hole wouldn't change the orbits of any planets that might exist around it.

 

[Squishua]

Furthermore, even with stars that ARE massive enough to become black holes, their event horizons MUST be smaller than their diameters, so gravitational collapse to a black hole wouldn't change the orbits of any planets that might exist around it.

Good point. Though if my memory of astronomy class is accurate, a good amount of its mass is lost when it goes supernova, which would lessen its gravitational pull.

Unfortunately, they (the inner planets) will be consumed when it becomes a red giant and we'll never see the sun go supernova.

-Squish

 

[69dodge]

Furthermore, even with stars that ARE massive enough to become black holes, their event horizons MUST be smaller than their diameters, so gravitational collapse to a black hole wouldn't change the orbits of any planets that might exist around it.

Is this exactly correct? Or only to first order or something like that?

 

[Yllanes]

Is this exactly correct? Or only to first order or something like that?

The supernova explosion would obviously have an effect and it would lose mass.

But if our sun were magically replaced with a BH of its same mass, the orbits of the planets would be the same. The only difference is that we would get rather cold.

Many people think BH are super vacuum cleaners... This is not true. They don't 'suck' any more than a normal star of the same mass would.

The most general solution of Einstein's equations for a BH was discovered by Kerr in 1963. It only depends on the mass and angular momentum. There are no more BH. From this point of view, BH can be considered as huge elementary particles. Two electrons are indistinguishable from each other. In the same way, two BH of the same M and J are indistinguishable.

Of course, this does not happen with stars, we need many parameters to characterise them precisely and more precision requires even more parameters (maybe they are not completely spherical, for example...) This can affect the orbits, so the situation is perhaps more complicated than what I said before. In fact, in the 1920s, even though Einstein had already formulated his GTR, people still tended to think that the preession of MErcury's perihelion was due to astrophysical effects, such as a non uniform mass distribution in the Sun.

 

[Ziggurat]

Is this exactly correct? Or only to first order or something like that?

As Ylanes pointed out, it's exactly correct. He actually forgot one parameter, though: the electric charge can also distinguish between black holes. But since that should be quite small compared to the mass in any real situation, we can pretty much only worry about charge-neutral black holes. But whether the gravitational body has collapsed into a black hole or remains a star is completely irrelevant to the field outside the radius of the star, just as in Newtonian gravity, the radius of a spherically symmetric body has no effect on the gravitational field at distances larger than that radius.