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

[Eliezer S. Yudkowsky]

Hal Finney wrote:
> Keith's example may not have worked, but Dirk Bruere explained a few
> months ago that a reactionless drive is inconsistent with conservation
> of energy.  This is true even if the drive uses power to produce thrust.
> 
> Suppose constant power leads to constant thrust, as the principle of
> relativity would require.  Constant power implies that total energy used
> will be proportional to time; but constant acceleration makes velocity
> proportional to time, and kinetic energy is proportional to v^2, which
> means it is proportional to time squared.  Any time you have input energy
> proportional to time while output energy is proportional to time squared,
> you will go over unity after enough time.

Understood.

Also:

"Shawyer cautions that the calculations only work for static thrusts. 
‘You can’t beat the laws of physics. If it is used to accelerate, the Q 
value drops. It is best used to lift a body and oppose a force, for 
instance to counteract gravity. It cannot be used to accelerate further.’"

Sounds like this violates the equivalence principle in General 
Relativity.  Staying put against gravity = accelerating in free space.

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