Warp speed space travel and GR:

[paddoboy]

Paddoboy and I eventually picked up on the fact that Professor Geraint Lewis was not saying anything that is connected to established science. It was sheer speculation. He said so. .

Obviously it is you with the baggage.
Professor Lewis certainly was speculating on knowledge and possibilities resulting from what is allowed by the laws of physics and GR, and has everything to do with science, along with the links I gave concerning the laws of physics and GR.
It was you wasting bandwith time insulting Lewis and Thorne with your usual drooling vitriol with inane childish remarks such as, "Professor GeraintLewis is fabricating fiction for science. His credentials aren't worth the paper and ink used in their forgery"
Although one must say that when you realised how stupid it was you did give a belated apology.

 

[tashja]

Hi, Dan. Prof Lewis answers your questions:

Hi Tashja -
Thanks for the questions -

Is "negative density energy" is a variation on "exotic matter"?

Exotic matter is just a catch all phrase for stuff that isn’t normal matter – but negative energy refers to a property of material, such that the pressure divided by the density is negative. I guess negative energy density materials would fit into the exotic energy bucket.

Isn't gravity supposed to be made of negative density energy or be non-conservative in terms of energy?

Gravity is not made of a material substance – but is created by energy densities – negative energy densities can cause an acceleration (which is why the cosmological constant is a negative energy material).

Is negative density energy conserved, or to put it another way, does negative energy combined with energy violate conservation of energy? Has this guy or anyone else ever built a prototype of a perpetual motion machine using negative density energy?

Not sure what you mean by this question – but a negative energy material has a conservation equation like all other forms of energy. However, it is important to note that energy is not conserved in an expanding space-time (such as an expanding universe). And no, no-one has ever built a perpetual motion machine (it’s not possible with negative energy material either).

Give an example of negative energy or exotic matter anyone has ever observed; I'm not talking about dark matter or dark energy, or anything happening during or 1 billion years after the Big Bang.

The cosmological constant (dark energy) is a negative energy density (this exists today, not just a billion years after the big bang). Also, the quantum vacuum (responsible for the Casimir effect) is a negative energy material.

'Warp speed' relative to WHAT? Anything matter or energy moving faster than light in one direction would need to move faster than light in EVERY direction at the same time (and by that I mean, not in a straight line along their former sublight or light speed paths of propagation). Matter or energy can't propagate like that. Quantum fields can. That is fact. Blowing warp bubbles or wormholes out of a pipe faster than light in a vacuum is a fairy story.

No, this is incorrect. It is relative to any observer in a Minkowski space-time. No, it does not have to propagate in all directions, only one. You should read the original paper by Alcubierre. Also, the statement about quantum fields is incorrect. Quantum fields are limited by special relativity. You statement about “faster than light in a vacuum”” is based on special relativity – the warp drive is a solution in general relativity.

Another difference between knowledge and imagination is the chasm separating science and relativity from episodes of Star Trek. Why is it that so many people confuse the two? Was Star Trek really that well played? I'll grant you, it was probably more entertaining than reading about physics. Build all the flashy warp drive and nacelle props you want. It will get you nowhere as fast as you are going right now.

I don’t like Star Trek.



//\\//\\//\\//\\//\\//\\//\\// \\
Geraint F Lewis,

Professor of Astrophysics

Sydney Institute for Astronomy
Associate Head (Research),
School of Physics A28
The University of Sydney
NSW 2006 Australia

 

[brucep]

Hi, Dan. Prof Lewis answers your ques:

The saying goes there's no such thing as a stupid question. I beg to differ with that. Thanks for the comments from Professor Lewis.

 

[The God]

Prof Geraint F Lewis, says

.... Also, the quantum vacuum (responsible for the Casimir effect) is a negative energy material....

Warp (Warping)....Quite a negative word

1. to bend or twist out of shape, especially from a straight or flat form, as timbers or flooring.
2. to bend or turn from the natural or true direction or course.
3. to distort or cause to distort from the truth, fact,true meaning, etc.; bias; falsify:

So is the good and erudite Prof saying that spacetime is a material and it is capable of twist or bent ?

Is it not the time to define spacetime with respect to material or energy or nothing, keeping in view the meaning of warping ?

 

[tashja]

Hi God,

Prof Geraint F Lewis, says

.... Also, the quantum vacuum (responsible for the Casimir effect) is a negative energy material....

Warp (Warping)....Quite a negative word

1. to bend or twist out of shape, especially from a straight or flat form, as timbers or flooring.
2. to bend or turn from the natural or true direction or course.
3. to distort or cause to distort from the truth, fact,true meaning, etc.; bias; falsify:

So is the good and erudite Prof saying that spacetime is a material and it is capable of twist or bent ?

Is it not the time to define spacetime with respect to material or energy or nothing, keeping in view the meaning of warping ?

Hi -

No - space–time is not a thing that bends and stretches, but the mathematics that describes it is similar as the mathematics that describes curved surfaces (Riemannian geometry) - but no where in relativity is space-time a material substance. Perhaps you want to have a read of a paper we wrote -

“Expanding space – the root of all evil” - http://arxiv.org/abs/0707.0380

Space-time is a mathematical tool for explaining how mass interact with mass – it’s not a thing.


Cheers - Geraint


//\\//\\//\\//\\//\\//\\//\\// \\//\

Geraint F Lewis,

Professor of Astrophysics

Sydney Institute for Astronomy
Associate Head (Research),
School of Physics A28
The University of Sydney

 

[danshawen]

You diss yourself and your comments are full of shit. The metric isn't speculation. It's a solution to the field equations derived as a prediction by the theory of general relativity. Speculation is the bullshit prediction by you that the Higgs boson is the source of gravity. Nobody in the science community, much less Professor Strassler, are interested in your juvenile delusions and lust for recognition.

You're funny, I'll grant you that. Peace.

 

[danshawen]

Prof Geraint F Lewis, says

.... Also, the quantum vacuum (responsible for the Casimir effect) is a negative energy material....

Warp (Warping)....Quite a negative word

1. to bend or twist out of shape, especially from a straight or flat form, as timbers or flooring.
2. to bend or turn from the natural or true direction or course.
3. to distort or cause to distort from the truth, fact,true meaning, etc.; bias; falsify:

So is the good and erudite Prof saying that spacetime is a material and it is capable of twist or bent ?

Is it not the time to define spacetime with respect to material or energy or nothing, keeping in view the meaning of warping ?

Warping with respect to what? What if we live in a universe in which it is a geometric and mathematical impossibility for any observer to determine what is bent and what is not? Or to put it another way, how do you expect to be able to do fluid dynamics when the only available tool is a straight edge, and different observers cannot even agree on whether it is actually straight, or if it is bent, by how much?

Even your stopwatches will need upgrades in order to understand what is meant by warpage of spacetime. Sub relativity clocks won't cut it. You need a faster clock; FTL, in fact. Fortunately, you won't need any exotic matter, negative density energy, or fairy dust in order to accomplish that. Every paired electron in matter is already entangled, and entanglement can effect changes FTL, and it need not propagate matter or energy FTL in order to do so.

But if the only working theory about quantum fields you have involves pixie dust, you're probably going to miss the next warp capable drive ride off of this rock, in which case, you're stuck here doing some very flawed remedial quantum math with the likes of prof Lewis. "Tell us class, what is the difference between 10^120 Plancian units and zero point modules again?"

Work it all out for us with a pencil, brucep. Show all your work if you want full credit. That goes double for prof Lewis, who has already arrived in FTL pixie land and desperately needs a cash infusion to finish his warp drive design. Who has some spare change for the good professor to do rocket science? Does anyone have the time? Time is money. Work it out. We know it's in there somewhere.

 

[OnlyMe]

Hi, Dan. Prof Lewis answers your questions:

Hi God,

Tashja, once again.., very nice responses!

 

[OnlyMe]

Warping with respect to what? What if we live in a universe in which it is a geometric and mathematical impossibility for any observer to determine what is bent and what is not? Or to put it another way, how do you expect to be able to do fluid dynamics when the only available tool is a straight edge, and different observers cannot even agree on whether it is actually straight, or if it is bent, by how much?

Even your stopwatches will need upgrades in order to understand what is meant by warpage of spacetime. Sub relativity clocks won't cut it. You need a faster clock; FTL, in fact. Fortunately, you won't need any exotic matter, negative density energy, or fairy dust in order to accomplish that. Every paired electron in matter is already entangled, and entanglement can effect changes FTL, and it need not propagate matter or energy FTL in order to do so.

But if the only working theory about quantum fields you have involves pixie dust, you're probably going to miss the next warp capable drive ride off of this rock, in which case, you're stuck here doing some very flawed remedial quantum math with the likes of prof Lewis. "Tell us class, what is the difference between 10^120 Plancian units and zero point modules again?"

Work it all out for us with a pencil, brucep. Show all your work if you want full credit. That goes double for prof Lewis, who has already arrived in FTL pixie land and desperately needs a cash infusion to finish his warp drive design. Who has some spare change for the good professor to do rocket science? Does anyone have the time? Time is money. Work it out. We know it's in there somewhere.

Dan.........., talking about Pixie Dust.......!

Seems to me Prof. Lewis addressed your issues clearly and without descending into insults.

 

[danshawen]

Dan.........., talking about Pixie Dust.......!

Negative density energy, or equivalently exotic matter, is an idea fabricated from whole cloth. We know a little bit about the energy we see, and imagine how it might work with the energy we would LIKE to see.

Anyone can do this with or without a PhD. We notice that gravity attracts and (except maybe for the case of dark energy) never repels, even for antimatter, upsidaisium, or unobtainium. We surmise, it might be nice once in a while if things fell in the other direction. Sure it would. But rocket engines that make use of Newton's third law isn't quite good enough. We want something, and we want it for nothing. Wish upon a star. Make someone else pay for the wish. Nice work if you can get it. Lewis has. Thorne has. Certain other folks I've met in my life would very much like to know how to arrange that, and who wouldn't? But it isn't about science. Don't pretend that it is.

If you don't wish to be insulted, stop giving me or reasons to or things to insult you about. No one else here does. The main difference between us is, I'm not a spambot meister looking for my next easy mark. You don't need to know any science to do that. I get it.

The spam storm in my email inbox isn't working either, by the way. Now I understand exactly what it is you are doing here, and even a little about how you do it. Keep up the good work until they catch you. Dream BIG.

For anyone else, or, oh, I don't know, maybe a science bulletin board that occasionally has spam problems, I think I might know one individual who is involved. He's evidently no rocket scientist.

 

[sweetpea]

From the pdf link in Professor G. lewis's reply to tashja.

2 Expanding Space
In understanding the concept of expanding space, it is important to examine the basic premise of general relativity, neatly packaged in John Wheeler’s adage matter tells Spacetime how to curve, and Spacetime tells matter how to move which sets out the dynamical relationship between the geometry of spacetime and the density and pressures of fluids contained therein. However, if the prominent cosmologists quoted in the previous section, will ask “how can space, which is ultimately empty, expand”, we must also ask the question of how this “nothingness” of the vacuum can be curved? By reducing Wheeler’s adage to matter tells matter how to move
the concept of spacetime, just like the aether, can be banished as being non-existent and unnecessary (e.g. Chodorowski 2006b).

My bold.

I'm not saying spacetime is a material thing or some kind of aether.
I can see the mathematical tool of a geometrical theory on the manifold of spacetime.

I just trying to picture the concept of movement if the concept of spacetime is banish.
If spacetime is banished are we then left talking of an absolute space and time background upon which 'matter tells matter how to move' ?

 

[paddoboy]

Dan.........., talking about Pixie Dust.......!

Seems to me Prof. Lewis addressed your issues clearly and without descending into insults.

Nicely put.
As I previously said, my contact with Professor Lewis stems from his regularity on a now defunct forum in which I also participated.
Professor Lewis as I also said, was rather "realistically" conservative without any flowering or guilding the Lily type of answers.
I actually had cause to cross swords with him on certain issues a couple of times, but it certainly did not dampen my respect for him as a qualified professional, something obviously which Dan is not.
It's a shame that this thread has denigrated into name calling and insults, purely as a result of the vitriol Dan has for many qualified professionals, Professor Lewis being one, and Kip Thorne another.

 

[paddoboy]

http://www.hawking.org.uk/space-and-time-warps.html
"In science fiction, space and time warps are a commonplace. They are used for rapid journeys around the galaxy, or for travel through time. But today's science fiction, is often tomorrow's science fact. So what are the chances for space and time warps".
more at the link.

Not only has spacetime warpage been shown to occur in the presence of mass/energy as per GR, but also the Lense Thirring effect has been verified. [GP-B]
While gravitational radiation has not as yet been directly observed, we do have pretty substantial evidence as to that prediction of GR also. [ Hulse-Taylor Pulsar]

Knowing those facts, it follows that what Professor Lewis has speculated, along with a myriad of other professional cosmologists over the years, is theoretically possible and obtainable for some super advanced civilisation.
The "Alcubierre drive" proposal more than a decade ago now, outlines that possibility.
The negative energy density needed for such a drive could theoretically come from the DE component of spacetime, something we do not know too much about as yet, but which we have observed through the accelerated expansion of the Universe.
Another version could make use of the Casimir effect.

 

[paddoboy]

The following is a very detailed paper as to the mechanics behind a possible future warp drive mechanism.

http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015936.pdf

 

[tashja]

Hi sweet. I sent your questions to Prof. Lewis. Below is his reply:

From the pdf link in Professor G. lewis's reply to tashja.
My bold.

I'm not saying spacetime is a material thing or some kind of aether.
I can see the mathematical tool of a geometrical theory on the manifold of spacetime.

I just trying to picture the concept of movement if the concept of spacetime is banish.
If spacetime is banished are we then left talking of an absolute space and time background upon which 'matter tells matter how to move' ?

Hi -

The concept of space-time is not banished – you just have to realise what it is – the mathematical medium that tells you how mass and energy influences mass and energy. Relativity tells you how to connect events with particles and photons, and this depends upon the mass and energy distribution around it.

The mistake people make is to treat space-time as a thing and then make suppositions of what happens in relativity based on this.

Did you read the Alcubierre paper? There is nothing mysterious about superluminal motion when it compares the motion here to photons over there – this is precisely the case in the Universe where we talk about the expanding universe.

Cheers - Geraint

//\\//\\//\\//\\//\\//\\//\\// \\//

Geraint F Lewis,

Professor of Astrophysics

Sydney Institute for Astronomy
Associate Head (Research),
School of Physics A28
The University of Sydney

 

[OnlyMe]

Hi sweet. I sent your questions to Prof. Lewis. Below is his reply:

Another nice one,

The concept of space-time is not banished – you just have to realise what it is – the mathematical medium that tells you how mass and energy influences mass and energy. Relativity tells you how to connect events with particles and photons, and this depends upon the mass and energy distribution around it.

The mistake people make is to treat space-time as a thing and then make suppositions of what happens in relativity based on this.​

 

[sweetpea]

Hi sweet. I sent your questions to Prof. Lewis. Below is his reply:

Thanks Tashja, I was hoping you would do that.
Using a geometrical theory about the manifold of space and time means you don't have to invoke a force or fictional force to find the path (geodesic )of a particle. I was wondering, would a force have to be invoked to explain a path in what Prof: G. Lewis is saying about 'matter tells matter how to move'.

I think the idea of putting-in a force of attraction with no explanation of how that force attracts is also a mathematical tool, and so like the spacetime model is just a model.
I'm not even a layman in these things and would find reading scientific papers a bit beyond me unless they are 'interpreted ' down to my level.
Thanks again Tashja and thank you Prof: Lewis.

 

[OnlyMe]

Thanks Tashja, I was hoping you would do that.
Using a geometrical theory about the manifold of space and time means you don't have to invoke a force or fictional force to find the path (geodesic )of a particle. I was wondering, would a force have to be invoked to explain a path in what Prof: G. Lewis is saying about 'matter tells matter how to move'.

It depends on what you mean by explain!

The reason I reposted that portion of Prof. Lewis' comment, in the post above, is because it speaks directly about the issue. GR is not a theory of fundamental cause and effect. It is a descriptive field theory that describes only the effect. It does not say anything about the why or how, matter tells space-time or other matter how to move, it only describes the result. I have had a long standing disagreement with Brucep on this point, where I have referred to his interpretation as a modern interpretation. A view that does think of space-time as a thing.

I am not sure I agree entirely with Prof. Lewis as he describes space-time in that last sentence, though I agree completely with what I understand of its intent. It is not clear to me, whether space-time is a thing, as in has some quasi-independent substance, or just a mathematical representation of a gravitational field. However in either case, anytime the path through space over time of matter, meaning a massive object, be it a particle, a rock or a planet, changes.., some force must be involved. It is just that in the case where changes in motion or path, through a gravitational field are involved, through we can describe the path and changes, we have no clear understanding of the fundamental mechanism(s)/force(s). Newton just labeled it/them action at a distance. Einstein, at least in the beginning seemed more interested in describing the dynamics, than in attempting to isolate the fundamental origin, and gave us GR.

As you may have noticed in the above, I am stuck somewhere between the idea that space-time is just a mathematical field theory, describing the dynamics.., and that it, space-time does have some undefined pseudo-independent substance of its own. But before this question has any place in the discussion it is important to understand exactly what is meant by the idea of warp speed.

I have not read the Alcubierre drive paper recently, or even Prof. Lewis' paper referenced earlier, so I cannot answer that question in the context of the OP.

I will say this much, again.., it is my belief that any time there is a relative change in the path of a massive object - a change in direction or speed - there is some force involved. Where gravitation is concerned the dynamics is described by GR and a space-time model, without needing to identify the fundamental force... That does not mean there is no fundamental force, just that it is not needed to describe the dynamics, of the field.

 

[sweetpea]

Hi Onlyme

It depends on what you mean by explain!

My point there about not giving an explanation for how an attracted force attracts was to show how the 'force idea' is just a mathematical tool of convenience for predictive purposes.

It is not clear to me, whether space-time is a thing, as in has some quasi-independent substance, or just a mathematical representation of a gravitational field. However in either case, anytime the path through space over time of matter, meaning a massive object, be it a particle, a rock or a planet, changes.., some force must be involved.

My bold.
I hope I'm not taking you out of context here, but that last part 'some force must be involved'.
Not in a geometrical theory about the manifold of space time. A particle travels along the straightest possible line (the geodesic) for such a spacetime manifold, that particle does not at any time need a force to change direction as it orbits, say the earth. Using the appropriate geometrical space time equations requires no force. Again, a mathematical tool of convenience for predictive purposes.

GR is not a theory of fundamental cause and effect. It is a descriptive field theory that describes only the effect. It does not say anything about the why or how, matter tells space-time or other matter how to move, it only describes the result.

Yes, I know GR does not explain why mass or energy curve spacetime it just does. I think Brucep would agree with that, I have never come across Bruce suggesting that GR does explain the 'why'. I think you have Brucep wrong there, but he can speak for himself.

 

[OnlyMe]

My bold.
I hope I'm not taking you out of context here, but that last part 'some force must be involved'.
Not in a geometrical theory about the manifold of space time. A particle travels along the straightest possible line (the geodesic) for such a spacetime manifold, that particle does not at any time need a force to change direction as it orbits, say the earth. Using the appropriate geometrical space time equations requires no force. Again, a mathematical tool of convenience for predictive purposes.

My intent was to point out that as Prof. Lewis described, but in my words here.., space-time and thus GR as a geometrical theory is only describing the field dynamics. You agreed I believe with that much.

My further statement which you seem to be at odds with, may be a, chicken or the egg issue. I might restate is as.., it does not matter whether you imagine that by some means matter exerts some force that curves space-time or that space-time is just a geometric field description of how one massive object affects the motion of another massive object....., in either case there is some force at play.., either directly between the two massive objects or by each massive object affecting its local geometry of space-time.., which then affects the other massive object.... But then that runs into issues with whether space-time is an independent thing or not! Prof. Lewis seems to have indicated that from his perspective that is in error, when he said, "The mistake people make is to treat space-time as a thing...". I believe he is right in that, because too often it leads to an assumption that there is no force of gravitation. While in free fall that seems reasonable because no force can be felt or measured, any change of motion from a state of free fall still requires force, which something in the free fall state must be resisting.., a counter force? And the debate can go on and on.

I personally don't believe that space-time itself causes things to move in any particular way. I believe that space-time is better thought of as a geometric field description of how an undetermined force of gravitation affects the motion of objects..., particles, rocks planets and yes even photons.