Author Topic: Questions about Wheeler–Feynman absorber theory and ME thrusters  (Read 1942 times)

Offline CW

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Hello all,

maybe someone can answer a question that came up in my mind in relation to thinking about Wheeler–Feynman absorber theory and its application in Mach effect type thrusters.

Imagine that you create new matter from energy, so this matter really did not exist before. If a wave from the future interacts with this newly created matter, doesn't that imply that an object from e.g. 1 billion light years away must have 'known' already, that from its own perspective, a new matter object would be created in 1 billion years from now to send out the wave in time? I'm not sure if this would make any physical sense, even in Wheeler–Feynman absorber theory. Because the 1 billion light years distanced object, from its own perspective, would then have shown a reaction to an object in the future, that wouldn't even exist for another 1 billion years. I can imagine the theory working when all matter did exist together from one specific point in time onwards. But I have difficulties with this scenario :-) .
Reality is weirder than fiction

Offline laszlo

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Ask this guy, bet he knows :-)



A bit more seriously,  the "new" matter isn't really new, is it? It's just matter/energy that has taken on a new "phase" and carries along all the history that was trailing along in the energy, right?

For that matter, if the wave from an object 1 billion light years away interacts with it, that wave is from the past, not future, right?

And finally, you are making radiation into something volitional. I don't see how that's valid.


Offline CW

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Ask this guy, bet he knows :-)



A bit more seriously,  the "new" matter isn't really new, is it? It's just matter/energy that has taken on a new "phase" and carries along all the history that was trailing along in the energy, right?

For that matter, if the wave from an object 1 billion light years away interacts with it, that wave is from the past, not future, right?

And finally, you are making radiation into something volitional. I don't see how that's valid.

Hello laszlo,

thanks for your answer. I'm not sure what you mean with 'history' that the energy carries with it. I can't see how energy would or could store a history.

When the wave is from the past and reaches the newly created matter A, how could the 1 billion light years away matter B react to something, that from perspective of B would only begin to exist in 1 billion years from now? Again, I can't see how the energy, that A was made of, could store a history to bridge that apparent logical gap, IMHO.

I'm not trying to make radiation into something volitional.. but it just confuses me to think that there would be a local reaction of B to A, that would not exist until 1 billion years into the future of B. I could only understand this if the whole of reality is 100% deterministic. Like a story, carved in stone and immutable. If this were the case, I could even imagine, in principle, constructing a crazy complex multidimensional periodic Fourier series that 'encodes' this story, like a movie.. with the ZPFs as a numerical artifact ;-) .
« Last Edit: 04/18/2015 07:00 PM by CW »
Reality is weirder than fiction

Offline nadreck

Ask this guy, bet he knows :-)



Where is John Hurt?
It is all well and good to quote those things that made it past your confirmation bias that other people wrote, but this is a discussion board damnit! Let us know what you think! And why!

Offline Nilof

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Your example is just an artefact of classical electrodynamics being deterministic and reversible. So if you know the final state rather than the initial state you can play the tape backwards. This doesn't mean you can physically break causality.

What determines whether the retarded or advanced solution should be used is the boundary values. If you have the initial values of the electromagnetic field and the initial particle positions, you use the retarded one. If you have a final value, you have to run the tape backwards to compute the field values and particle positions before that, and here you use the advanced solution.

What Wheeler-Feynman theory really states is that any process that emits a photon is equivalent to a process that absorbs one if you play everything backwards. It looks at the special case where the future boundary values are forced to be zero(or whatever else it ends up being, which you may mathematically keep fixed to make the problem homogeneous). Since this is a future boundary condition, it isn't surprising that values seem to be determined by future events.
For a variable Isp spacecraft running at constant power and constant acceleration, the mass ratio is linear in delta-v.   Δv = ve0(MR-1). Or equivalently: Δv = vef PMF. Also, this is energy-optimal for a fixed delta-v and mass ratio.

Offline CW

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Your example is just an artefact of classical electrodynamics being deterministic and reversible. So if you know the final state rather than the initial state you can play the tape backwards. This doesn't mean you can physically break causality.

What determines whether the retarded or advanced solution should be used is the boundary values. If you have the initial values of the electromagnetic field and the initial particle positions, you use the retarded one. If you have a final value, you have to run the tape backwards to compute the field values and particle positions before that, and here you use the advanced solution.

What Wheeler-Feynman theory really states is that any process that emits a photon is equivalent to a process that absorbs one if you play everything backwards. It looks at the special case where the future boundary values are forced to be zero(or whatever else it ends up being, which you may mathematically keep fixed to make the problem homogeneous). Since this is a future boundary condition, it isn't surprising that values seem to be determined by future events.

Hello Nilof,

thank you very much for your great explanation. I think I can see now how this is connected. But one thing comes to my mind when I think it through to the end: Wouldn't the way our universe ends, in the far future, already be reflected in today's reactions or behavior of all existing particles? Just that we don't know how to read it?
« Last Edit: 04/18/2015 08:10 PM by CW »
Reality is weirder than fiction

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