On 03/08/14 01:09, Ian Woollard wrote:
There's essentially no chance that a thruster can work where you turn it on, feeding only electricity through it, and with nothing leaving it; where you switch it off, and you're now moving faster. This is what the emdrive is claimed to do. If you could do that, we're in perpetual motion territory; because it violates both conservation of momentum, and (more subtly) it can be shown to violate conservation of energy. The emdrive paper tried to fix that by using the kinetic energy equation in one frame of reference, but you can show that energy is violated in every other frame of reference except the one he did the calculation in. So he's done something wrong. You can fix it, if you introduce an efficiency variable, and set the variable to zero.
Suppose, as has been claimed, the drive is somehow exchanging momentum with the entire universe. The momentum of the universe may have a (?local) velocity - which would be mathematically equivalent to a preferred frame of reference.
If so, there need be no violation of either of the conservation laws.More, that would not violate special relativity; which, afaik, while it does not contain a preferred frame of reference, doesn't actually _disprove_ the existence of one either.
In fact, a lesser version of a preferred frame of this type almost certainly exists: if you go at half the speed of light in any direction from here, the cosmic background becomes noticably more anisotropic. Here is closer to some preferred frame than travelling at 1/2 c in any direction.
It might be interesting to see whether the force varies in eg a diurnal pattern.
To put this in terms which can be more easily understood, suppose the universe acts as a very large mass somewhere within reach of the drive. The drive pushes on it and it (!?maybe?!) pushes back.
The only question now, in terms of Newtonian or SR energy and momentum math, is the relative initial velocities of the drive and the mass.
Haven't done an analysis in terms of general relativity, but offhand it isn't impossible there either.
(I agree it's almost certainly a measurement mistake: but it doesn't seem to be completely impossible, or to violate any physics we already know.
It does introduce two new-ish things though, a (?local) velocity for the universe, which as we have seen is not really so new after all - and some way of pushing against it.
well, three newish things, the third being the question: if the universe gets pushed by the drive, where, if anywhere, does it go?)
-- Peter Fairbrother
-Ian Woollard