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Re: Propellantless propulsion from plain-old Special Relativ

Posted: Wed Apr 01, 2015 12:52 am
by D Tibbets
Back to GR and instantaneous versus limited speed interactions, I am far out of my depth. Does the speed of gravity fit into the argument? The speed of gravity is apparently ~ equal to the speed of light. This superficially causes all sorts of problems with orbital mechanics, but there are considerations that apparently resolves the conflict.

http://math.ucr.edu/home/baez/physics/R ... speed.html

Dan Tibbets

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Wed Apr 01, 2015 2:04 pm
by GIThruster
D Tibbets wrote:Does the speed of gravity fit into the argument?
Yes. The basic idea is that if gravity causes inertia (Mach's Principle), and is linking gravity sources from across billions of light years, how can we have instantaneous inertial effects caused by gravity? The answer is in Wheeler-Feynmann Absorber theory, which posits waves moving both forward and backward in time, and this theory works for several different kinds of needs. It works in electrodynamics to provide answers we don't otherwise have, about how fields work inside for example, every electric motor. The back reaction from electric and magnetic fields appears likewise to be instantaneous, but we do not note an issue here because if they propagated at c we would not notice this given the small distances inside a motor. Absorber theory says the effects are instantaneous since they're the result of half the sum of the advanced and retarded waves, which are themselves not instantaneous but propagate forward and backward in time.

Absorber theory has trouble when it comes to the self-energy of the electron and this is why Einstein gave up this line of inquiry, and later why Wheeler and Feynman abandoned it. The theory makes good sense and is "elegant" in that it has symmetry no other attempts in electrodynamics have. Time symmetry is a nice thing to find in physics, especially when it solves the problem of instantaneous action at a distance. The trouble was, the electron self-energy issue.

Woodward solved the electron self energy issue. This is what chapters 6 & 7 are all about and IMHO, Woodward deserves an Nobel for this work alone. Time will tell, as physicists work it out, but his solution is again elegant, and truly astonishing.

And it does not hurt to note the utility of the theory proposed. If Wheeler-Feynman and Woodward are all correct, we can have mastery over inertia. We also should expect Cramer and Kastner to be correct in their similar adaptations of Absorber theory, meaning this Transactional Interpretation of Quantum Mechanics, and if this is right, then we have a way forward in looking at quantum gravity. The fact we can't even agree on an interpretation of quantum phenomena, is much of what has held up progress in bringing QM and GR together.

BTW, this is an opportunity for a bright guy to make a name for himself. Design an experiment that would show whether there is a speed c time delay in electromagnetic effects. Since EM is easily turned on and off, there should be a way to test for time delay. The issue would seem to me to be one of measurement when looking at distances divided by c, would require some impressive precision, but there are all sorts of ways to get impressive time measurement precision.say your E field or B field couples across 0.1M, and c is 3E8M/s, so you need sE-9 precision. Seems to me there must be many ways to determine if fields couple at c or instantaneously. Would be a great experiment to do, and maybe not too difficult nor expensive.

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Mon Jun 01, 2015 1:06 pm
by Diogenes
Not quite a good fit, but no other heading looks any better.




Spacecraft built from graphene could run on nothing but sunlight



Image


While cutting graphene sponge with a laser, they noticed the light propelled the material forwards. That was odd, because while lasers have been used to shove single molecules around, the sponge was a few centimetres across so should be too large to move.


http://www.newscientist.com/article/mg2 ... WxX5kdc4sb




Makes you wonder what would happen if a Graphene sail pulls it's own light source behind it. :)


If it is expelling electrons, I don't see this process continuing for very long before sufficient charge builds up to stop it.

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Mon Jun 01, 2015 2:45 pm
by JoeP
Diogenes wrote: If it is expelling electrons, I don't see this process continuing for very long before sufficient charge builds up to stop it.
... and this should be easy enough to test with the experimental setup they have already put together.

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Mon Jun 01, 2015 10:37 pm
by paperburn1
That still will not move me faster than C

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Tue Jun 02, 2015 12:41 am
by Diogenes
paperburn1 wrote:That still will not move me faster than C



I wouldn't worry about it, there's plenty enough to do in this solar system, for awhile anyway.


But if this phenomena opens the door to some new physics, It just might get you moving faster than C.

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Tue Jun 02, 2015 1:36 am
by Skipjack
I am looking for something that helps us get to orbit faster, cheaper and more reliably. Once you can do that, going anywhere else becomes much easier. But for some reason that seems to be more elusive than in space propulsion :(

Re: Propellantless propulsion from plain-old Special Relativ

Posted: Wed Nov 11, 2015 6:17 am
by KitemanSA
Skipjack wrote:I am looking for something that helps us get to orbit faster, cheaper and more reliably. Once you can do that, going anywhere else becomes much easier. But for some reason that seems to be more elusive than in space propulsion :(
Kite launcher.