[extropy-chat] Relativity drive: the end of wings and wheels?

[Eliezer S. Yudkowsky]

Keith Henson wrote:
> At 06:53 PM 9/8/2006 -0700, you wrote:
> 
>>Keith Henson wrote:
>>
>>>Reactionless drives *are* perpetual motion machines.  If you can't
>>>visualize why I can explain the obvious.
>>
>>Actually, I can't see this as obvious.  Suppose the reactionless drive
>>requires a thermal differential to drive it, and equalizes the thermal
>>differential in the process.  How would it necessarily violate the
>>second law of thermodynamics in the course of violating conservation of
>>momentum?
> 
> Thought experiment.  The power you can get out of a moving object is the 
> product of speed and force.
> 
> So let a vehicle with a reactionless drive on a zero friction bearing 
> accelerate to a high enough speed.  Then you lower a wheel and draw enough 
> power to run the drive.  Let it go a little faster and you are making 
> power.  (This assumes the drive force is invariant to the reference 
> frame.)  QED, a reactionless drive is the same thing as a perpetual motion 
> machine that *makes* power.

Only if the reactionless drive requires no power to run, or if it 
requires less power to run than the corresponding work produced.  They 
made some strange claims, but not that one.

-- 
Eliezer S. Yudkowsky                          http://singinst.org/
Research Fellow, Singularity Institute for Artificial Intelligence