Author Topic: Free energy, FTL paradoxes and so on.  (Read 12515 times)

Offline KelvinZero

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Free energy, FTL paradoxes and so on.
« on: 08/03/2014 04:50 AM »
I have noticed a few threads getting effectively derailed by repeated explanations of these general issues, till the point the specific idea being claimed is totally lost in the noise. However I think any proponent of those ideas has to fully understand these issues and be able to defend their claim with respect to it. The defense should not be a phrase or word salad. They should be able to explain how it behaves in specific scenarios.

If you do not know how you claim behaves, you do not know what you are claiming.

For example there are many phenomena that are FTL yet do not provide FTL communication. The spot of a torch beam flicked across a distant wall could easily move faster than light, for example. I have also heard descriptions of FTL warp travel where, yes, but the theory also predicts you can not exit the bubble at the other end. You have FTL, paradoxes are avoided, but it is not the Star trek drive that you want.

So therefore I thought we could move this to a general thread. We can put nice explanations here and then link to them instead of repeating them endlessly in specific threads.

Another use for this thread is that I would like to gather some nice simple paradox examples. For example I would like a nice example of how to produce a paradox from communicating only slightly faster than light.

Finally..There may be loopholes! Im quite prepared to admit that, in fact I enjoy proposing them. A general issue stated here does not kill every possible variation of the idea. I just think that they are an excellent framework for investigating what a given claim actually means, or if it has any defined meaning at all.

Offline KelvinZero

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Free energy from propellantless propulsion.
« Reply #1 on: 08/03/2014 05:06 AM »
A common claim of propellantless propulsion is that you can get a constant acceleration from a constant source of power. This would provide free energy.

(*) Propellantless propulsion lets you increase velocity proportional to the energy you put in.
(*) Classical physics lets you extract energy proportional to the velocity squared.

Possible workarounds:
(*) Firstly why not free energy? In for a penny, in for a pound as they say. Also perhaps the energy is coming from somewhere else. To this I would just say: at least stop talking as if the only application is a better ion drive. It is still freaking free energy, man.

(*) How about if it is somehow tied to a particular inertial frame. In this case you have something that is propellantless in the sense of a plane with a propeller. You won't get the same advantage but it could still be way better than a rocket which requires exponential amounts of fuel to achieve a given velocity. Another interesting result is that it may also provide a form of free energy, but only the well known type exploited by sailing ships that act in two mediums with different average velocity.

(*) frobnicat points out that a photon rocket is a special case that fits within my definition, and obviously does not deliver free energy. We can't just assume an infinite power source that we can carry along with us. So check your maths isn't just a fancy way of describing a photon rocket!
I would add a third workaround : if the propellantless propulsion ship has not a higher Thrust/Power ratio than a perfect photon rocket engine (that is not much efficiency, T/P<1/c) then it is not giving free energy,
« Last Edit: 08/04/2014 04:46 AM by KelvinZero »

Online Stormbringer

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Re: Free energy, FTL paradoxes and so on.
« Reply #2 on: 08/03/2014 05:14 AM »
i think 2 or more reference frames kind of muddy the issue a bit when it comes to FTL and time travel.

the best example i can think of is Dr Woodward's and Dr Cramer's talks on Wormholes. in the home reference frame the results are absurd. but Physicists in the audience do not object on the ground that present understandings of physics forbid it. they instead caveat that when we get a theory of Quantum gravity it will probably forbid it. that's not a strong critique. we don't even know much of anything about a formal framework for QG. but we do have one for relativity and apparently even relativity with all it's restrictions on FTL and time travel does not forbid absurd results.

i am speaking specifically of opening a worm hole and sending the distal opening towards a star 2000 light years away with the distal end traveling at fractionally bellow c. on the near end frame of reference the wormhole is usable within weeks even though the other end will not arrive for 2000 years according to common sense. you can look through it and see the destination as if the distal end were already there. you can step through it and be at the destination AND then step back through and be back nearly instantly. the wormhole clearly allows you to travel 2000 years into the future and then back to the present as well as travel 2000 light years FTL.

You'd think a room full of troubleshooting physicists would cream the idea. but the best they did was speak of a future theory of Quantum Gravity will most likely forbid it later. not relativity forbids it. not present day understanding of physics forbids it.

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Online ChrisWilson68

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Re: Free energy, FTL paradoxes and so on.
« Reply #3 on: 08/03/2014 05:21 AM »
For example I would like a nice example of how to produce a paradox from communicating only slightly faster than light.

The standard paradox from being able to communicate faster than light is that you can send messages back in time, thanks to relativity.  If it's only slightly faster than light, it requires moving your communication apparatus at very close to the speed of light.  As your communication gets faster, the speed at which you need to get your communication setup moving becomes lower and lower.  But for any communication speed greater than that of light, there is some speed less than light speed at which you can move your communication gear to be able to send your message backward in time.

This effect comes from one of the main points of relativity -- that two events that are simultaneous but at different points in space in one inertial reference frame happen at different times in a reference frame moving with respect to the original one along the axis connecting the two points.

Here's the setup.  Send out four spaceships, ships A, B, C, and D.  A has a faster-than-light transmitter to a receiver on B and C has a faster-than-light transmitter to D.  Put ships A and D in the vicinity of Earth and B and C in the vicinity of Mars.  Accelerate A toward Mars and D away Mars at a significant fraction of light speed and arrange that A and D pass close to each other at noon by Earth clocks.  Also accelerate B away from Earth and C toward Earth and arrange for B and C to pass by each other going opposite directions at the same speeds as A and D, and make sure they pass at about the same time that A and D pass.

A and B are going the same speed in the same direction.  Have A send a message to B faster than light in the inertial frame they share.  If they're going fast enough and the message goes fast enough over light speed, the message will arrive from A (near Earth) at B (near Mars) at a point in time that is before it was sent from Earth's reference frame.  B is near C, so have B flash a light in Morse code for C to see.  Now C and D are also in the same reference frame, so have C send the same message to D using the same faster-than-light communication method.  From the point of view of someone on Earth, the message arrives at D at a point in time before it was sent by C.  So, round trip, the message goes from A to B to C to D and goes back in time from the point of view of the Earth on the A to B leg and on the C to D leg.  B and C are near each other, so arbitrarily little time can be taken by that leg.  And the same is true of A and D, so the message can be sent to A and arrive before it was sent from A.

Now if you can send a message back in time, you have causality issues.  What if you decide that if you get the message "yes" you will send the message "no" and if you get the message "no" you will send the message "yes"?  Since you get the message before you send it, you can choose to do that, and you have a paradox.
« Last Edit: 08/03/2014 05:25 AM by ChrisWilson68 »

Offline KelvinZero

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Re: Free energy, FTL paradoxes and so on.
« Reply #4 on: 08/03/2014 05:35 AM »
@Stormbringer
Just think in terms of explaining it to a science fiction writer.

They won't particularly care whether it is permitted by quantum gravity, they will just want to be able to describe to their audience what actually happens when, for example, someone tries to murder their grandfather before they are born. What do they experience? What do observers experience?

My position is that if someone claims to have a time machine but cannot describe what happens in this case, then they cannot describe what the word time machine actually meant when they used it.

@ChrisWilson68
I will have to try drawing that out on paper :) .. I know I can demonstrate it with an 'instantaneous communicator' but this is a bit tougher.

Online Stormbringer

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Re: Free energy, FTL paradoxes and so on.
« Reply #5 on: 08/03/2014 05:48 AM »
@Stormbringer
Just think in terms of explaining it to a science fiction writer.

They won't particularly care whether it is permitted by quantum gravity, they will just want to be able to describe to their audience what actually happens when, for example, someone tries to murder their grandfather before they are born. What do they experience? What do observers experience?

My position is that if someone claims to have a time machine but cannot describe what happens in this case, then they cannot describe what the word time machine actually meant when they used it.



i can buy that.

we don't know because there are several theories that allow or disallow paradox situations from arising. until we know which theory is correct we cannot describe the outcome of such an effort. E.G. you cannot effect your own past because any time traveling spits you into a parallel timeline. in this type of solution you could actually surveill the past or return with an extinct critter because most things would still be the same. some solve it by saying no form of time travel is permitted. period. some say your action creates a paradox it self nullifes your action.


but like you said until we nail the correct theory we cannot describe what happens truthfully.
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Offline CW

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Re: Free energy, FTL paradoxes and so on.
« Reply #6 on: 08/03/2014 09:33 AM »
Concerning free energy coming from somewhere else.. it would be 'free' in the sense that we don't have to, well, pay for it in any way. But this seems just like drilling a 'hole' somewhere in physical reality and extracting some stored up energy potential. That potential would still be missing elsewhere, after we made use of it. So, looking at the whole picture, I think this would qualify as 'free' energy in only relative terms. Maybe it would be like going to a foreign country and robbing that place of its resources - for 'free'. Who knows :) .
Reality is weirder than fiction

Offline MP99

Re: Free energy, FTL paradoxes and so on.
« Reply #7 on: 08/03/2014 09:40 AM »


@Stormbringer
Just think in terms of explaining it to a science fiction writer.

They won't particularly care whether it is permitted by quantum gravity, they will just want to be able to describe to their audience what actually happens when, for example, someone tries to murder their grandfather before they are born. What do they experience? What do observers experience?

My position is that if someone claims to have a time machine but cannot describe what happens in this case, then they cannot describe what the word time machine actually meant when they used it.

I find the "many worlds" hypothesis easiest to swallow.

Every second of the grandfather's life, some of the "worlds" include him dieing in various ways.

So, congrats to the murderer - they just created another branch where the grandfather died, and the grandchild never existed.

If this is correct, then "a" grandfather dies, but not the one in the grandchild's past. From the murderer's POV, they then just need to kill themselves in all universes where the grandfather didn't die in order that they get to experience the world they tried to create.

Cheers, Martin

Offline MP99

Re: Free energy, FTL paradoxes and so on.
« Reply #8 on: 08/03/2014 10:13 AM »


I have also heard descriptions of FTL warp travel where, yes, but the theory also predicts you can not exit the bubble at the other end. You have FTL, paradoxes are avoided, but it is not the Star trek drive that you want.

But, surely this is sending at least one "bit" of information to an outside observer - the presence / transit of the bubble itself. Something like "hurrah, we made it there", or "send help".

Imagine an ET sending such a device barrelling through our Solar System. Assuming a natural origin can be eliminated, confirmation of the existence of ETs would be one hell of a "bit" of information to impart.

Actually, more than that - the origin can also pass further information about the location of the sender. Also, changes of speed & direction might be modulated to pass further information?

You could also imagine a stream of such objects (miniaturised, presumably), passing more complex messages.

Or... is the warp bubble somehow invisible to outside observers?



Also, does "can not exit" mean can never stop - must keep travelling forever? Doesn't that need continuous energy to maintain the warp bubble?

Or does it mean the collapse of the warp bubble is too energetic to be survivable? If so, would that make for an incredibly potent "interstellar ICBM" if ET fired it towards Earth and collapsed the bubble in our vicinity?

Cheers, Martin

Offline MP99

Re: Free energy, FTL paradoxes and so on.
« Reply #9 on: 08/03/2014 10:22 AM »


A and B are going the same speed in the same direction.  Have A send a message to B faster than light in the inertial frame they share.  If they're going fast enough and the message goes fast enough over light speed, the message will arrive from A (near Earth) at B (near Mars) at a point in time that is before it was sent from Earth's reference frame.  B is near C, so have B flash a light in Morse code for C to see.  Now C and D are also in the same reference frame, so have C send the same message to D using the same faster-than-light communication method.  From the point of view of someone on Earth, the message arrives at D at a point in time before it was sent by C.  So, round trip, the message goes from A to B to C to D and goes back in time from the point of view of the Earth on the A to B leg and on the C to D leg.  B and C are near each other, so arbitrarily little time can be taken by that leg.  And the same is true of A and D, so the message can be sent to A and arrive before it was sent from A.

Per my previous post, A sends a "can not exit" warp object to/past B, and C sends another back to/past D.

Only one bit, but that's enough for paradoxes, yes?

(Do you actually need objects B & D, or can C & A just observe the message objects whiz past?)

Cheers, Martin

Offline john smith 19

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Re: Free energy, FTL paradoxes and so on.
« Reply #10 on: 08/03/2014 10:40 AM »
They won't particularly care whether it is permitted by quantum gravity, they will just want to be able to describe to their audience what actually happens when, for example, someone tries to murder their grandfather before they are born. What do they experience? What do observers experience?
Well not murder but certainly trying to change the future is the subject of Gregory Benford's novel "Timescape."

It's my impression the SF writers of the 1930's understood the actual quantum thinking of time travel quite well. Another classic short story from that time is "Sidewise in time."

Bottom line. You cannot change your past. You can create a new universe where those events happened and the new universe has the resulting follow on. However a pure time machine would only take you back through your time line (its a time machine, not an inter universe transporter).  :(
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Offline KelvinZero

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Re: Free energy, FTL paradoxes and so on.
« Reply #11 on: 08/03/2014 11:17 AM »
I wasn't really asking for solutions to the grandfather paradox:)

However, since FTL apparently is time travel, we can expect FTL to be just as strange.

What I really wanted to do was separate this really general stuff that everyone should know from specific threads about propellentless propulsion and FTL. Then we can ask on those threads just how those particular claims work around a specific paradox, and not have to explain the issue again and again to each new person who joins the conversation.. just point them here.

I don't expect to understand the theory behind any particular claim, If it is correct but not obvious to the physics community it must be mindbogglingly difficult. But I should be able to understand what I experience if I had such a device and tried to recreate one of the classic paradoxes.

Offline Nilof

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Re: Free energy, FTL paradoxes and so on.
« Reply #12 on: 08/03/2014 01:15 PM »
I wouldn't dismiss what physicists mention about quantum gravity affecting wormholes just yet. You can actually get quite far and make some useful predictions with semiclassical quantum corrections to GR. Essentially, using a fixed curved metric as a background for a quantum field theory and seeing if anything happens.

If all the fields stay at similar values to what is found in flat space for a given metric, you don't get much out of it. But if you see significant changes, you get a warning that the considered metric breaks down completely as soon as quantum mecanics is considered.

The best known example is Hawking radiation around a black hole, which implies that black holes are not static and will evaporate in a finite ammount of time. But some wormhole metrics see vastly more dramatic effects. The example above of two wormhole mouths being moved so that a closed timelike curve is formed will have streams of virtual particles moving along that curve leading to infinite stress-energy densities. In other words, for that system, GR breaks down completely and the classical solution is useless.

This is the background of the chronology protection conjecture by Stephen Hawking. It may or may not be true in quantum gravity for more complex systems, but the background is certainly worth considering. Metrics that have CTCs but no stream of virtual particles in semiclassical gravity exist.

Note that such a pulse of virtual particles could actually be quite useful for some applications, especially if it can be tuned so that the mouths do not collapse. If momentum is exchanged between the mouths by the pulse, as a repelling force, it could be a good way to move extremely heavy stuff around. One of the very few things that is better than a reactionless drive is a reactionless drive that moves wormholes.

By "riding the edge" of the future lightcone of a stationary wormhole mouth, you could in theory move a wormhole mouth to a distant point in a very small amount of proper time. The means that the distant destination would be available in an equally short amount of time to the people residing near the stationary wormhole mouth because they would be traveling into the future(in their reference frame).
« Last Edit: 08/03/2014 02:19 PM by Nilof »
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.

Online Chris Bergin

Re: Free energy, FTL paradoxes and so on.
« Reply #13 on: 08/03/2014 01:50 PM »
Isn't this oogey boogy?

If my post gets more than five likes, that'll be a yes and a lock. If the opening post gets more than five likes, it stays.

Who wins? You decide!

Offline DMeader

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Re: Free energy, FTL paradoxes and so on.
« Reply #14 on: 08/03/2014 02:32 PM »
By "riding the edge" of the future lightcone of a stationary wormhole mouth, you could in theory move a wormhole mouth to a distant point in a very small amount of proper time. The means that the distant destination would be available in an equally short amount of time to the people residing near the stationary wormhole mouth because they would be traveling into the future(in their reference frame).

Didn't Seven Of Nine say that in the Voyager episode where the ship was trapped on the event horizon of a quantum filament and Janeway wanted to reverse the polarity of the main deflector to yadda yadda yadda........

Can we have some discussions of real-world spaceflight-related advanced concepts and not yet more bad Star trek technobabble? Please?

Offline Nilof

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Re: Free energy, FTL paradoxes and so on.
« Reply #15 on: 08/03/2014 03:36 PM »
@ DMeader:

General relativity isn't exactly near term "real life" spaceflight, but it is a roughly 100 year old and well established scientific theory. Semiclassical corrections from QFT to  it is a rich subject with almost 50 years of history. If common physics terminology sounds like technobabble to you, I can provide equations:

For a wormhole mouth traveling at velocity v, we have dτ = dt/sqrt(1-v2) = cosh(r)dt where r is the rapidity(which is defined by r = atanh(v), replaces delta-v in the relativistic rocket equation and is generally more useful than the velocity).

The proper distance between the two synced mouths is given by s2 = x2 - (t - τ)2. What I was referring to as "riding the future lightcone" of the fixed mouth is a trajectory of constant s, since a lorentz invariant and symmetric interaction between the two mouths will depend only on s2. If s2 ever becomes negative, we get a CTC.

So we have the algebraic equation (t - τ)^2 = x2 - s2. Taking the τ derivative and rearranging, we get x/(t -  τ) =  (cosh(r) - 1)/sinh(r).

Looking at the LHS, the ratio x/(t -  τ) will get closer and closer to one as you get closer you are to the lightcone edge. Similarily, the RHS is a strictly increasing function of r and tends to one as r goes to infinity. So if there is a repelling force between wormhole mouths that may cause a stable constant s trajectory, it can be used to propell one mouth at arbitrarily high final speeds away from the stationary mouth as the two push against each other.

(Using units with c = 1 throughout the post.)
« Last Edit: 08/03/2014 04:03 PM by Nilof »
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 DMeader

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Re: Free energy, FTL paradoxes and so on.
« Reply #16 on: 08/03/2014 07:43 PM »
Ok, and that has anything to do with spaceflight in the near future (like our lifetimes), how?

Maybe we are working off of two very different definitions of what "advanced concepts" means. The header for the thread states "In-works and future conceptual ideas of space flight, from Nuclear Propulsion to Tethers and beyond". I don't see "free energy, FTL paradoxes, dark energy, wormholes, warp travel, FTL communications", any of that being within that definition.

I think that there are those who take the term "advanced concepts" as an excuse to go off into oogie-boogie sci-fi bordering-on-nonsense that will have no application while any of us are on this earth and long beyond this until several laws of physics can be broken. Of course, if this forum were to be renamed "Sci-Fi Advanced Concepts" I'd go away and never say another word about it.

Offline Lee Jay

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Re: Free energy, FTL paradoxes and so on.
« Reply #17 on: 08/03/2014 07:48 PM »
I'm not fond of the term "free energy" to describe something that has an efficiency higher than 1 or otherwise violates conservation of energy.  One could argue that the Bussard ram jet is a free energy device since it harvests fuel it finds along the way, the way a propeller harvests propellant (and oxidizer, if not an electric) along the way.

Offline MP99

Re: Free energy, FTL paradoxes and so on.
« Reply #18 on: 08/03/2014 07:58 PM »
Isn't this oogey boogy?

If my post gets more than five likes, that'll be a yes and a lock. If the opening post gets more than five likes, it stays.

Who wins? You decide!

Chris,

please, don't!!!

This is the science counter aurgument to possible oogey boogy stuff.

How do I record an un-like for this???

cheers, Martin

Edit: there are probably many threads where a link here may be a valid alternative to closing some anti-science thread.
« Last Edit: 08/03/2014 08:08 PM by MP99 »

Offline IslandPlaya

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Re: Free energy, FTL paradoxes and so on.
« Reply #19 on: 08/03/2014 08:35 PM »
Isn't this oogey boogy?

If my post gets more than five likes, that'll be a yes and a lock. If the opening post gets more than five likes, it stays.

Who wins? You decide!

Chris,

please, don't!!!

This is the science counter aurgument to possible oogey boogy stuff.

How do I record an un-like for this???

cheers, Martin

Edit: there are probably many threads where a link here may be a valid alternative to closing some anti-science thread.
Thanks Chris.

Offline frobnicat

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Re: Free energy from propellantless propulsion.
« Reply #20 on: 08/04/2014 01:05 AM »
A common claim of propellantless propulsion is that you can get a constant acceleration from a constant source of power. This would provide free energy.

(*) Propellantless propulsion lets you increase velocity proportional to the energy you put in.
(*) Classical physics lets you extract energy proportional to the velocity squared.

Possible workarounds:
(*) Firstly why not free energy? In for a penny, in for a pound as they say. Also perhaps the energy is coming from somewhere else. To this I would just say: at least stop talking as if the only application is a better ion drive. It is still freaking free energy, man.

(*) How about if it is somehow tied to a particular inertial frame. In this case you have something that is propellantless in the sense of a plane with a propeller. You won't get the same advantage but it could still be way better than a rocket which requires exponential amounts of fuel to achieve a given velocity. Another interesting result is that it may also provide a form of free energy, but only the well known type exploited by sailing ships that act in two mediums with different average velocity.

In software a well known rule is garbage in, garbage out. I have the feeling that "constant acceleration from a constant source of power necessarily implies free energy" is ignoring the first term of the likewise rule : free energy in, free energy out. The "constant source of power" is often implicitly supposed to be free, mass-wise, it is supposed being able to deliver its output at constant mass. This is approximately true for low energy density generator but starts to be false to few % if going nuclear and completely false with matter/antimatter. So like a classical rocket can do a constant thrust from a constant power without acquiring free net energy, because it has to accelerate a mass of fuel to V before this mass can be used to thrust to 2V, a propellantless propulsion ship has to accelerate to V the mass of fuel that will have to be converted to energy to provide the power to keep accelerating to 2V.

Therefore, while the second workaround (particular inertial frame) makes sense, I would add a third workaround : if the propellantless propulsion ship has not a higher Thrust/Power ratio than a perfect photon rocket engine (that is not much efficiency, T/P<1/c) then it is not giving free energy, it does not increase dry mass velocity proportional to the energy because enough fuel mass is to be tapped and the ship bleeds mass along the way, so it had to start heavier. It means that such a "propellantless propulsion" would not be more efficient than using photon momentum as propellant. Better having a free energy generator from the start...

I already posted similar comment on the other thread, about the high Q RF cavity, that apparently claims a T/P 2 orders of magnitude higher than 1/c. I don't want to sound insistent but the lack of E=mc˛ in the other comments makes me wonder : it's not because the only flow is "pure energy" in any device that mass bleeding is magically repealed. It takes a lot of energy to save on ejected mass, to the point power source starts to lose mass.
« Last Edit: 08/04/2014 01:12 AM by frobnicat »

Offline KelvinZero

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Re: Free energy, FTL paradoxes and so on.
« Reply #21 on: 08/04/2014 04:32 AM »
Good point frobnicat. I did see that before, but did not click that a photon rocket falls within the definition I gave of "propellantless".

I guess the nonsensical case works out to be equivalent to a rocket with FTL effective exhaust velocity, or something like that.

Online ChrisWilson68

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Re: Free energy from propellantless propulsion.
« Reply #22 on: 08/04/2014 06:21 AM »
In software a well known rule is garbage in, garbage out. I have the feeling that "constant acceleration from a constant source of power necessarily implies free energy" is ignoring the first term of the likewise rule : free energy in, free energy out.

No, you're missing the point.  Imagine you have a box.  You put in one dollar and two dollars come out the other side.  Obviously, by cycling those dollars back around, you can make as many dollars as you want.  They're free dollars.

That's what free energy means.  It means you have a box and if you put X amount of energy in one side, you get more than X amount of energy out the other side.  You can just cycle the energy you get back as output into the input and you get as much energy as you want, without limit.  That's what free energy means.

You need to put some energy in to jump-start the whole process, but after it gets going, you just cycle the some of the output power back to the input and the device runs forever producing power, without any more power input ever needed.

Online Stormbringer

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Re: Free energy, FTL paradoxes and so on.
« Reply #23 on: 08/04/2014 07:02 AM »
 i don't think that analogy holds for some of these things. it may be your basic perpetuum mobile posited by the average fringe science type. but i don't think it applies to all situations where the term free energy is used.

e.g; Geothermal heat pumps. solar power systems. systems that tap a source of ambient energy. something like a tuned antenna that taps an ambient RF source (maybe a Moray valve or something Tesla came up with.) -or carried further (closer to the matter in contention lately) something that makes use of vacuum energy some ways.
« Last Edit: 08/04/2014 07:05 AM by Stormbringer »
When antigravity is outlawed only outlaws will have antigravity.

Offline SteveKelsey

Re: Free energy, FTL paradoxes and so on.
« Reply #24 on: 08/04/2014 07:19 AM »
Agreed  ChrisWilson. One perspective that has not been included yet is a transistor ( transfer resistor) system. The transistor functions like a valve controlling the flow of power from the power supply according to the demands of an input signal. If you draw the bounding box around the transistor excluding the power supply it might appear to be a free energy device. It produces more at the output than at the input.

From what I understand of some proposals, e.g. Woodwards Machian inertia model, the ' free' energy is the product of accessing  a remote energy source, in the case of Woodward's  description ' Far of active matter'
This seems controversial because Mach's principle is no longer favoured as a model for inertia. The current model favours gravity and inertia as separate properties and the result of particle derived forces.  However , ithe mach primciple has always  struck me as  at least plausible. Gravity has no known distance limit, the inverse square law does not imply anything like such a limit. There is a lot of mass in the universe. How is it possible that we are not affected locally by far off matter? This is an aspect of Mach's model that we ignore today with no good cause.  The transistor model is worth considering and certainly great care needs to be made when drawing boxes around any system.
2001 is running a little late, but we are getting there.

Offline frobnicat

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Re: Free energy from propellantless propulsion.
« Reply #25 on: 08/04/2014 09:08 AM »
In software a well known rule is garbage in, garbage out. I have the feeling that "constant acceleration from a constant source of power necessarily implies free energy" is ignoring the first term of the likewise rule : free energy in, free energy out.

No, you're missing the point.  Imagine you have a box.  You put in one dollar and two dollars come out the other side.  Obviously, by cycling those dollars back around, you can make as many dollars as you want.  They're free dollars.

Well, that is the extraordinary claim. It might work with trading, but so far is a basic impossibility with real mass-energy, at least in a patch of universe that's stable to the time scales involved by ships : By Noether's theorem "the principle of conservation of energy is a consequence of invariance under time translations" (wikipedia) so it's not like conservation of energy is a rule that could be broken without consequences, the reverse proposition would imply to break time invariance. So, not only if a device claims to be such a perpetual machine of the first kind (breaks the first principle of thermodynamics) forget about propulsion applications as KelvinZero stated as this is by itself bigger news by itself, but also dig to the even deeper consequence that reality is not stable, that physics is not the same in 2015 than in 2014. At cosmological scales such fundamental "rolling" of potential energy or phase parameters (of say quantum vacuum) is believed to occur (inflation, dark energy...) but not at human timescales. Or else it would imply locally releasing/accelerating such a process, akin to taping to some already there potential energy (and also implying irreversibility ?) anyway this is no longer free energy in the strongest sense.

Quote
That's what free energy means.  It means you have a box and if you put X amount of energy in one side, you get more than X amount of energy out the other side.  You can just cycle the energy you get back as output into the input and you get as much energy as you want, without limit.  That's what free energy means.

You need to put some energy in to jump-start the whole process, but after it gets going, you just cycle the some of the output power back to the input and the device runs forever producing power, without any more power input ever needed.

So maybe we should make categories, I'll try to incorporate some of the ideas so far :

*1 Free energy of the first kind, real free, like "coming from nowhere", not even vacuum, with no borrowing or debt. Be prepared to see some time invariance breaking of physics unless you find a flaw in Noether's theorem.
Edit : GR is more finicky about how to cleanly define "energy" and this is quite above my level of understanding but I found this post by Lubos Motl http://motls.blogspot.fr/2010/08/why-and-how-energy-is-not-conserved-in.html to be clear enough as for the consequences :
Quote
you cannot ever violate the energy conservation law unless you are considering a situation in which the whole global shape of the Universe - its asymptotic behavior at infinite distance - is being transformed. So whatever happens near the Earth will always conserve the energy pretty much exactly, with the deviations' being undetectable.
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Around the Earth, as long as you do no cosmic-size experiments, and we won't be able to do them, the spacetime has a time-translational symmetry at infinity because the spacetime is almost exactly flat and with this time-translational symmetry of the background in place, Noether's theorem guarantees the existence of the energy conservation law. So no perpetual motion machines. Again. The violation in cosmology is something like that the total energy carried by dark energy (or photons) increases (decreases) by a factor of 2 in something like 10 billion years. It's significant at the cosmological timescales and length scales but it has no impact on local experiments performed on the Earth.
(I understand : in any playfield as small as a galaxy, even if juggling with singularities)

*2 Cheap energy without reference frame (without velocity penalty, indefinite constant acceleration) : from some usually stable potential "zero point" of vacuum or space or whatever by somehow locally rolling to a lower point. This is just a loaning, and unless you pay back you have less potential energy to tap into in the future, until local bubble of reality goes bankruptcy. I will assume that vacuum has no absolute reference frame and that such a device indeed has indefinite constant acceleration given constant power harvesting capability, hence without velocity penalty. But the enormous amount of energy you could recover in the average reference frame (say by colliding a bystander moon) after a billion year of such acceleration would somehow be present as a trail of growing debt in some potential energy in the ship's path (radiating tachyon flows ?). The debt, as measured from the average reference frame has to grow along the path because of the quadratic (and the relativistic) progression of kinetic energy compared to the "constant power, constant acceleration" in the ship's frame. So this has to be explained : how such a process taps more power as measured from a moving reference frame (relative to it) than it gets to use in its local frame (unless there is free energy of the first kind)

*3 Cheap energy with one absolute reference frame (with velocity penalty, indefinite power and acceleration but not both constant) : harvesting/pushing on some medium that has its own stable rest speed, meaning that it becomes harder to get same yield as velocity increase relative to this medium, be it CMB radiation, dark flow, or more mundane interstellar gas like the Bussard ram jet mentioned by Lee Jay. At some point the "drag" or lower yield induced by harvesting higher velocity incoming medium will equilibrate with the thrust that can be emitted, depending on the efficiency of the process. This point of equilibrium and ultimate speed (relative to medium) will depend on the efficiency.

Edit :
*4 Relatively cheap momentum by pushing on one absolute reference frame : if not harvesting energy from the medium (self contained energy in ship) and just pushing on medium, the lower yield comes from pushing back on a faster "road". Still very worth compared to classic propulsion if doable. That would be the case for pushing on planetary or interplanetary magnetic field (electrodynamic tethers) as more power must be pumped against induced voltage (at constant intensity thrust).

*5 Cheap energy with two absolute reference frame : harvesting a differential of two mediums that have different rest speeds, one of those can be a mundane planetary body but its orbit would be altered (windmill). Well, for a planetary body that could be evened out yearwise but solar system as a whole would "recoil". For a ship this needs two exotic flows, dark flow vs CMB for instance, and the same caveats as above case apply : the faster the ship, the harder the harvesting.

*6 Sailing without keel, cheap momentum with one absolute reference frame (with significant speed relative to earth/solar system) : letting ship couple and drag on a flow, mundane like solar sailing or more exotic... Also you can't go upwind can you ?

*7 Sailing with keel, cheap momentum with two absolute reference frame (with significant speed relative to earth/solar system) : letting ship couple and drag on two flows. By tacking on one of the medium you can go upwind the other flow.

Edit :
*8 ? Borrowing kinetic energy from a future payback, finding a way to take the initial debt (of acquiring cheap velocity) with the ship and repay later when settling to rest (relative to initial rest frame). Alcubierre drive or other negative mass/energy device ? Not sure about this one and its consequences/premises...
« Last Edit: 08/04/2014 01:48 PM by frobnicat »

Offline IslandPlaya

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Re: Free energy, FTL paradoxes and so on.
« Reply #26 on: 08/04/2014 12:29 PM »
Awesome post frobnicat!
I don't think I've ever seen better info on the matter in hand anywhere else. Yay NSF!
Maybe you could number your * points?
That would enable us to discuss with reference to your post with things like "blah.. frobnicat class 2 blah..."
My opinion is that all the propellant-less drives are of frobnicat class 3.
 ;D

Offline frobnicat

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Re: Free energy, FTL paradoxes and so on.
« Reply #27 on: 08/04/2014 01:17 PM »
Done numbering. Glad if it can be useful. Before it's adopted as an official propulsion crackpot scale I should state that I'm not a professional physicist : this is a hopefully serious and informed contribution but amateur level.

Offline KelvinZero

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Re: Free energy, FTL paradoxes and so on.
« Reply #28 on: 08/09/2014 01:49 AM »
I was thinking about the possibility of loopholes that could avoid FTL paradoxes. So you can construct a time machine, but could we apply some additional restriction such that it is never used to create a paradox?

I failed but I would be interested to hear other schemes.

Three possibilities I thought of were:
what FTL were limited to a single frame of reference such as the CMB frame?
or what if some effect prevented FTL travel in the other direction for some period of time?
or similarly what if all FTL were outwards, sort of like the expansion of the universe?

However all these possibilities can be ruled out because we can create a paradox with just a single FTL trip:
The standard paradox from being able to communicate faster than light is that...

Thus even if the trip were wrt to a special frame or no FTL travel ever happened again in the entire universe, a paradox could be created.

It always surprises me when people actually investigating this show no interest in these paradoxes, as if just not looking at them will allow it to behave like it does on star trek

Offline RotoSequence

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Re: Free energy from propellantless propulsion.
« Reply #29 on: 09/16/2014 03:31 AM »
(*) Classical physics lets you extract energy proportional to the velocity squared.

Where, and how?

Offline KelvinZero

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Re: Free energy from propellantless propulsion.
« Reply #30 on: 09/16/2014 04:00 AM »
(*) Classical physics lets you extract energy proportional to the velocity squared.

Where, and how?

http://en.wikipedia.org/wiki/Kinetic_energy

Quote:
In classical mechanics, the kinetic energy of a non-rotating object of mass m traveling at a speed v is
v = 1/2mv^2


There are multiple ways you could extract the energy, for example an electric train generates electricity slowing down. It is probably easiest to imagine with some sort of frictionless maglev train. Push it up to speed with your propellantless thrust then extract the energy as electricity slowing down. A train moving twice as fast can return four times as much energy as you slow it to a stop.
« Last Edit: 09/16/2014 04:07 AM by KelvinZero »

Offline QuantumG

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Re: Free energy, FTL paradoxes and so on.
« Reply #31 on: 09/16/2014 04:21 AM »
.. but a rotating mechanism is probably more likely, and would work just as well.
I hear those things are awfully loud. It glides as softly as a cloud. What's it called? Monowhale!

Offline RanulfC

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Re: Free energy, FTL paradoxes and so on.
« Reply #32 on: 09/16/2014 04:15 PM »
Ok, and that has anything to do with spaceflight in the near future (like our lifetimes), how?

Well if you're talking that kind of spaceflight then it's always going to be nothing but a few astronauts (government employees) and a very few manned and unmanned missions with not a lot to "look-forward-too" now isn't it? :)

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Maybe we are working off of two very different definitions of what "advanced concepts" means. The header for the thread states "In-works and future conceptual ideas of space flight, from Nuclear Propulsion to Tethers and beyond". I don't see "free energy, FTL paradoxes, dark energy, wormholes, warp travel, FTL communications", any of that being within that definition.

NASA for a recent example (but not limited to as the ESA, Russia, India, China, etc have all spent "real" money on this stuff) has done research under the definition of "advanced concepts" in just about all the mentioned subjects and is if fact continuing to do so on the off chance that some of this really far out "theoretical" stuff may in fact have some current applications. "And beyond" should have been your first hint that the "subject" of "Advanced Concepts" by its nature does not include JUST what you might think is possible...

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I think that there are those who take the term "advanced concepts" as an excuse to go off into oogie-boogie sci-fi bordering-on-nonsense that will have no application while any of us are on this earth and long beyond this until several laws of physics can be broken. Of course, if this forum were to be renamed "Sci-Fi Advanced Concepts" I'd go away and never say another word about it.

If one is to be technically accurate at some point MOST of what we now know to be "true" was considered "oogie-boogie science" or worse and "not discussing it" was the polite as well as "politically correct" thing to do. You are now aware of what is contained under this thread title and are under no obligation to discuss the subject matter JUST because it happens to be on here. On the other hand the OP has a very good point in that the subjects discussed herein DO appear quite often and having a thread dedicated to the subjects would cut down on proliferation of numerous other threads on the subjects poping up in which you would be obliged to comment yet again. I see this as saving bandwidth.

Chris:
Isn't this oogey boogy?

If my post gets more than five likes, that'll be a yes and a lock. If the opening post gets more than five likes, it stays.

Who wins? You decide!

I hit like on the OP, and it went from "X-and five others like this post" to just me and CW68 and you'rs is showing 9+ you so I guess I'll be lucky to get this posted before you lock the thread... But I'll point out again that this is actually an ANSWER to the numerous "oogie-boogie" threads so you might want to reconsider locking it...

Randy
From The Amazing Catstronaut on the Black Arrow LV:
British physics, old chap. It's undignified to belch flames and effluvia all over the pad, what. A true gentlemen's orbital conveyance lifts itself into the air unostentatiously, with the minimum of spectacle and a modicum of grace. Not like our American cousins' launch vehicles, eh?

Offline Nomadd

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Re: Free energy, FTL paradoxes and so on.
« Reply #33 on: 09/16/2014 04:32 PM »
Isn't this oogey boogy?

If my post gets more than five likes, that'll be a yes and a lock. If the opening post gets more than five likes, it stays.

Who wins? You decide!
Does both posts getting more than 5 likes put the thread in an uncertain state in which it's both locked and unlocked until someone observes the result and collapses the consciousness based wave function? (The Schrodinger/Bergin cat paradox?)
« Last Edit: 09/16/2014 04:33 PM by Nomadd »

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