Talk:Disjunction drive

For a May 2005 deletion debate over this page see Votes for deletion/Disjunction drive

To me, this part sounds completly stupid: "By the time the field reaches the plate, the magnet could even have been destroyed. Does the plate still experience a force? If so, it no longer has an object to impart an opposite force against." The proposed gedanken-experiment basically mandates the use of relativistic theory. In this theory, however, the magnet and the plate _never_ interact directly (or, at least, saying that they do isn't really usefull). Each interacts with the magnetic field. So the plate _always_ has an object to "impart an opposite force against" as it imparts it on the magnetic field.

This would basically mean that the given example is nonsensical. (The question it askes "Does the plate still experience a force?" sounds like a paradox, when in fact it isn't: there is only one, well-defined, correct answer -- unless one commits deliberate error when answering it.) However, maybe others can defend it, so I won't delete it for now. (in fact, I think the description at http://www.daviddarling.info/encyclopedia/D/disjunction_drive.html sounds much more sensible) -- Abel Daniel

As far as I can see, this is not very different from turning a light bulb on for a short period of time and running a solar sail off the resulting light beam when the bulb is no longer turned on. The electromagnet creates a field by emitting photons, which interfere in such a way as to give the macroscopic effect of a magnetic field. The photons are emitted in such a way that the field initially has no intrinsic momentum. The plate absorbs some of these photons, and in so doing gains momentum - macroscopically, the magnetic field acts upon the metal so as to produce a net force. The end result is a plate which has net momentum, and an expanding electromagnetic pulse which has total momentum equal and opposite to the momentum of the plate. In short, if you only consider local interactions with the field, and do away with all concept of action at a distance, there is no paradox.

I merged this article with Breakthrough Propulsion Physics Program because a similar VfD debate over Bias drive was to merge. It is for sake of consistency that I am doing this. Sjakkalle 08:32, 14 May 2005 (UTC)