Paul March wrote:
Anyway, a couple of questions posed by people there:
by Vanadium50:
"The problem, apart from the fact that Woodward's calculation is Just Plain Wrong (it takes the same momentum to stop a the mass that it did to get it going in the first place) is that momentum is conserved locally as well as globally. I can't move the momentum to the "rest of the universe" without applying a force"
The required force you seek is supplied by Newton's third law. Remember that the Mach Effect is nothing more than taking advantage of transient forces buried in normal inertial reaction forces we've ignored to date.
from CuriousKid
"For those not wanting to delve into it, here are some facts about this theory:
1) His theory requires non-local interactions (is not compatible with SR and causality).
You need to look a little closer at Woodward's M-E derivation. The Mach-Effect is compatible with SR, GRT and is Lorentz invariant in the 4D analysis.
"2) The "mach" comes from his theory claiming mass is due to the interactions with the rest of the universe (including interactions propagating back in time)"
It's not only Woodward's theory. It's based on Dennis W. Sciama's 1953 "On the Origins of Inertia" PhD thesis paper under Paul Dirac and Woodward's late 1980s discovery of some transient temporal terms in normal inertial reaction forces that people have ignored to date.
"So, in my opinion, if you want to use this for propulsion, you can pretty safely ignore it.
If you are interested in it more for theoretical reasons, you can safely ignore it, unless you are okay with accepting all of the above. Since I doubt that is the case, I'm not going to bother commenting further."
That's your priviledge.
from Kev
"The short answer is no. The mutual gravitational pull will be less, if the two bodies are moving relative to the observer. To an observer co-moving with the two bodies, the mutual gravitational pull will be the same. This is simple application of SR. If the two bodies moved towards each other faster as you suggest, this would provide a method to detect absolute motion and this would violate SR."
If you folks would actaully read and understand Sciama's 1953 "Origins of inertia" PhD thesis and Woodward's 2004 "Flux Capacitors and the Origins of Inertia" paper before firing off these uninformed one liners, a lot of these misconceptions could be resolved before hand. I'd append their papers but this forum won't allow it, so happy hunting...
See:
http://en.wikipedia.org/wiki/Dennis_William_Sciama
http://adsabs.harvard.edu/abs/1953MNRAS.113...34S
See:
http://www.springerlink.com/content/m442n70106j14012/