It's another speculative warp-drive paper, based on quantum theory...if anyone has read it and cares to comment, I would be interested...
http://arxiv.org/abs/0712.1649
Newbie
It's another speculative warp-drive paper, based on quantum theory...if anyone has read it and cares to comment, I would be interested...
http://arxiv.org/abs/0712.1649
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Thanks for posting that. But please use a more descriptive title, such as "Lambda Warp Drive", which is what I'm going to call it.
This is not really agin' the mainstream, at least as that usually plays out here. This is based on our favorite and most successfull theory of space-time, General Relativity. It's just a very highly speculative, wild, pie in the sky application of it.
For those who don't want to wade through that paper and aren't familiar with the jargon and concepts. Alcubierre, many moons ago, described a space-time consisting of a little "bubble" of space-time that could move at a coordinate speed much faster than light in flat space-time, and drag the interior along with it. There's no problem here at all with special relativity. It is "space time itself" that is moving faster than light, not anything moving through it. I hate to phrase things that way, but that's about the best you can do without rambling on and on.
Now, only problem is you need *negative mass-energy* (and solar masses worth of it to boot) to create that bubble, plus some very weird problems such as signals taking infinite time to reach the boundary of the bubble from within. And there are some "quantum energy conditions" that appear to be violated, although some say there are ways around that. One of them posted here a while back. And there is a proof that states such "exotic matter" is always required to make such exotic space-times. No way to do it with regular mass-energy that we're familiar with.
In this paper, however, the idea is to create that bubble by manipulating *Lambda*, the cosmological constant locally, rather than using exotic matter. Well, depending on how you like it, Lambda itself may be "exotic matter", so there you go.Anyway, the authors here suggest you may able to do something with the local quantum vacuum that will vary lambda locally in such a way as to create the bubble.
And note that many, including the present authors as well as Alcubierre himself use the language of space-time expanding behind the bubble and contracting in front of it. That is just one way to look at it.
And keep in mind, as Johnny Carson used to say, this is wild, wild stuff. I love stuff like this, but it's far, far beyond anything we could even think about doing now, even if it is possible.
-Richard
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Well, reading through it, their back of the envelope calculations suggest it would take 1 Jove mass worth of energy to get a bubble to Warp Factor One. That's in line with energy requirements of similiar Alcubierre bubble models I've seen. Well, in the order of magnitude range.
Now, figure out how to convert a jupiter mass to "pure energy" then concentrate it in a small volume and convert that to "dark energy" mode, and do it all without blowing your fool self up in the most spectacular explosion every witnessed locally that might well vaporize the earth and the whole darn solar system with it, and there you go. Warp factor one, engage!
Maybe that's what some of the gamma ray bursts are. ETs out there blowing themselves up testing warp drive for the first time.
-Richard
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I like my Lambda with mint jelly, and my Porkra with applesauce.Originally Posted by publius
STARGAZING: All I see are the lights of a billion places I'll never go. --Howard Tayler, Schlock Mercenary
Newbie
...for the explanation. I actually first found the link on Wired Magazine's science blog. I was curious about the energy requirements, recalling that other schemes of this nature also required massive amounts of energy. I haven't been able to read the paper, but the blog entry led me to believe that they also speculate as to a "speed limit" set by the Planck-length in this formulation?
I realize that it's not really ATM physics, but I thought I'd post it here just to be safe...it is about 'warp drive', after all.
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Hey, from one sol to one jove. Give it a few more years and we may have the amount required small enough to fit into a couple of nacelles.
Order of Kilopi
[QUOTE=vercingetorix;1133979 I haven't been able to read the paper, but the blog entry led me to believe that they also speculate as to a "speed limit" set by the Planck-length in this formulation?
[/QUOTE]
Yes, that was something to do with some quantum limit on how much you could vary Lambda locally (according to how their idea works, of course, which may or may not have anything to do with how the universe works
That's nothing to sneeze at, but at the that level, the energy required exceeded that contained in the observable universe.
Our poster here who had his ideas about this was DavidW. He was a bit, well, "pleased with himself" so to speak. If you search on that username you should find it.
He said he could get around the energy condition violations and some of the other weird stuff, and I think he said he was down to the earth mass level of energy. And they had some limit too in their scheme, about 10^10 c IIRC. That's just what he said, and I don't know enough to know if his work was correct or not.
But it's certainly fun to speculate about.
-Richard
Moderator
Absent the presentation of a truly ATM concept, let's try this in Q&A.
Never attribute to malice that which can be adequately explained by ignorance or stupidity.
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*******************Thanks for posting that. But please use a more descriptive title, such as "Lambda Warp Drive", which is what I'm going to call it.
This is not really agin' the mainstream, at least as that usually plays out here. This is based on our favorite and most successfull theory of space-time, General Relativity. It's just a very highly speculative, wild, pie in the sky application of it.
For those who don't want to wade through that paper and aren't familiar with the jargon and concepts. Alcubierre, many moons ago, described a space-time consisting of a little "bubble" of space-time that could move at a coordinate speed much faster than light in flat space-time, and drag the interior along with it. There's no problem here at all with special relativity. It is "space time itself" that is moving faster than light, not anything moving through it. I hate to phrase things that way, but that's about the best you can do without rambling on and on.
Now, only problem is you need *negative mass-energy* (and solar masses worth of it to boot) to create that bubble, plus some very weird problems such as signals taking infinite time to reach the boundary of the bubble from within. And there are some "quantum energy conditions" that appear to be violated, although some say there are ways around that. One of them posted here a while back. And there is a proof that states such "exotic matter" is always required to make such exotic space-times. No way to do it with regular mass-energy that we're familiar with.
In this paper, however, the idea is to create that bubble by manipulating *Lambda*, the cosmological constant locally, rather than using exotic matter. Well, depending on how you like it, Lambda itself may be "exotic matter", so there you go.
And note that many, including the present authors as well as Alcubierre himself use the language of space-time expanding behind the bubble and contracting in front of it. That is just one way to look at it.
And keep in mind, as Johnny Carson used to say, this is wild, wild stuff. I love stuff like this, but it's far, far beyond anything we could even think about doing now, even if it is possible.
-Richard
Hi, Sounds like " Mr. Fusion " is going to be inadequate for this purpose,
and we don't even have Mr. Fusio. http://www.bautforum.com/images/icons/icon12.gif
Wink Sounds like FLS is easy as long as you have enough energy to
accelerate the solar system!
Best regards, Dan
Established Member
Been suggested before. There's a sad lack of blue shifted ones, should expect to be 50% after correction for expansion.
Maybe that's what some of the gamma ray bursts are. ETs out there blowing themselves up testing warp drive for the first time.
-Richard
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Warp Drive
WARP DRIVE. Or if the speed of light is considered to be Warp 10, then the ejecta cloud of a type 2 supernova reaches ~ Warp 1 quite nicely...(Alexei Fillipenko, re: SN 1987a ). Nothing extraordinary at all. Fairly mundane. No spacetime bubbles. No solar mass starships. No Alcubierre Drive. Just astrophysics. pete
Administrator
Ok, but other than that, what are the problems.
Established Member
I think the best area of research for this mysterious power source should focus on toddlers, squirrels and excitable toy house dogs. They all seem to have a limitless supply of energy - if only we could find a way to harness it!
Administrator
My bold - And that certainly would be dark energy.
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At least there would finally be a use for the little yappers. The dogs, I mean. And the way squirrels should be used for energy is as a fuel source, nasty little buggers!
STARGAZING: All I see are the lights of a billion places I'll never go. --Howard Tayler, Schlock Mercenary
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I'm going to shoot the one who brought up those little dogs. Lord, I hate 'em. This local neighbor couple got one of those things. They think it's just the cutest thing and fawn over it ridiculously. I was over there, and that little sucker went nuts, yapping and barking. They thought it was cute, assuring me he meant no harm. I turned my back on him, and that little sucker bit me right on my ankle. Luckily I had my boots on.
They couldn't believe it, "Bad, bad, little precious---awww, widdle precious is still so cutey wooty, smooch smooch, smooch". And I got the impression they were more amused by it than anything else, proud that their baby could really attack or something.
I wanted to kill that thing, just stomping it dead right there -- and still do. I just don't understand why people like them. They are worse than any of the normal sized or bigger dogs, even the mean ones. They're just not right in the head somehow or another.
-Richard
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Anyone buying a dog should pay for a dvd from Ceasar Milan ,
The Dog Whisperer. Then, they would actually know how to take care of and train a dog, rather than the haphazard excuse for dog ownership we see all too often. It's ridiculous.
Established Member
(Note: I had a hard time deciding what forum this should be posted under, but it struck me mostly as an ATM concept. My apologies in advance if my decision was wrong.)
Now, I am not supporting this ATM idea or trying to defend it. What I am doing is questioning its validity since my knowledge is woefully limited in regard to this sort of thing.
I had always thought this stuff was absolutely impossible, but it seems a paper came out yesterday by a Richard K. Obousy and Gerald Cleaver that is supposed to somehow illustrate how this would be possible.
This .pdf file can be viewed in its entirety here: http://arxiv.org/PS_cache/arxiv/pdf/...712.1649v3.pdf (121 Kb., 6 pages in length.)
For whatever reason, I have a very hard time trying to swallow this despite my lack of algebra acuity. Plus, I find it very hard to believe something as groundbreaking as this could just pop-up out of nowhere without being noticed by more people in the scientific community.
Are these folks making a number of grievous thinking errors like I suspect them to be? What are some blatant scientific mistakes they have made, if any? The concept as a whole just doesn’t sit right with me.
Am I just being overly suspicious, or am I right to be skeptical about this idea?
Order of Kilopi
Boy, I hate PDF.
Established Member
To be honest, so do I. Unfortunately I can't seem to find it anywhere else or under any other format. Waiting for IE to load that cumbersome .PDF viewer into the browser is downright painful, every time.
I suppose I could transform the six pages into .gif images and upload them to my photobucket, but I am not sure how they would feel about me using it like that. I am sketchy on copyright and usage rules, so I play it safe by not taking chances.
Moderator
(Note: I had a hard time deciding what forum this should be posted under, but it struck me mostly as an ATM concept. ...)
ToSeeked. Also, based on other posts, the concept isn't really ATM. Threads merged in Q&A.
Never attribute to malice that which can be adequately explained by ignorance or stupidity.
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I just made the mistake of reading that Wired blog and the comment sections. It just makes me mad at head banging misconceptions that arise with this stuff. The one that took the cake with me was a comment that "this is based on quantum theory, not General Relativity". I just wanted to grab the author of that and shake him, maybe whop him upside the head once or twice as well. The whole thing is GR, just using some quantum notions of what lamdba might be and how it might be varied to get the required space-time.
While they did mention Alcubierre at the end, this "warp bubble" idea is not new. This is just the latest variation on it.
-Richard
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You know, it might be fun and interesting to see how the Alcubierre "warp bubble" works roughly. Note that negative mass energy was required in the original version. This latest variation just does it with Lambda.
We can actually use Newton to get a general idea of how this negative mass thing works.
Consider the gravitational field of a negative mass. Now, think carefully about negative mass means. Does that mean just negative *gravitational mass* or does it mean negative inertial mass as well? What would the Equivalence Principle apparently say about this? What does F = ma say when 'm' is negative?
To consider this, it may help to write Newtonian gravity out in the full form, where M is the source, and m is the test particle. The inertial mass of the test particle is m_i, and its gravitational mass is m_g.
F = m_i*a = -G *M *m_g/r^2
The Equivalence Principle says m_i = m_g. Well, what about when m_g is negative?
Now, ponder that a bit and when you think you have the answer, consider this. Place a negative mass of -M and a positive mass of +M some distance 'd' apart and let gravity do what it will. What happens, there? It's very important What is the acceleration of both sources due to the other's field?
Now, all of you, don't be shy. Take a stab. Don't be surprised if you think the result is crazy. That's what negative mass is, weird and crazy, and that weird and craziness is what makes our warp bubble work.
-Richard
Newbie
I am a physicist and have read the paper. The authors mention Alcubierre in the first sentence and so clearly are not claiming be introducing the groundbreaking new idea of warp propulsion. They present their ideas modestly and with a pinch of salt..."The authors wish to reiterate that these calculations are extremely 'back of the envelope' "
The main calculation of the origin (and potential manipulation) of the necessary negative energy is completely quantum field theoretic so, respectfully, the above quote is unjustified from Richard. (note section where Zeta function regularization is used in the divergent sum and integral).
What the authors are pointing out is that although a warp bubble is possible, no-one has done much in over a decade to suggest how this bubble could be created. The original aspect of the paper is that the authors take an approach inspired from string theory, i.e the suggestion that extra spatial dimensions exist. They then go on to propose that these compact extra dimensions could be manipulated in a way that propels a spacecraft within our universe. Just listen - manipulating the 5th dimension to propel a spacecraft. That is the original take that this paper presents. This is highly creative and is groundbreaking in that it represents a paradigm shift in the small but growing field of 'warp drive' physics.
I would not take anything away from authors. To reach this level of mathematical sophistication and physical insight takes absolutely years of very intense study. And to then publish a paper on such a 'fringe' subject takes guts.
Newbie
Its not like its a cure for cancer. For a start the energy required would involve an amount of negative mass the size of Jupiter (!!). Also, its not 'out of nowhere'. Warp drive and wormhole papers come out quite frequently.
For whatever reason, I have a very hard time trying to swallow this despite my lack of algebra acuity. Plus, I find it very hard to believe something as groundbreaking as this could just pop-up out of nowhere without being noticed by more people in the scientific community.
Are these folks making a number of grievous thinking errors like I suspect them to be? What are some blatant scientific mistakes they have made, if any? The concept as a whole just doesn’t sit right with me.
Am I just being overly suspicious, or am I right to be skeptical about this idea?
Most physicists visit, and publsh on xxx.lanl.gov frequently. The 'gravitation and quantum cosmology section is here:
http://xxx.lanl.gov/list/gr-qc/recent
You should look for yourself. A new paper on wormholes comes out every other day. check back and see for yourself. Warp drive papers are a bit rarer, but still not infrequent.
I have been in email contact with the authors as I am writing an article for a student magazine. I have learned the authors have been interviewed so far by the BBC, the Guardian, new scientist, Physics today and have featured in the wired magazine blog. On top of this a documentary has been filmed and is being released later in the year.
For a technology that is clearly centuries (if not millenia) away from being within the grasp of the human race, this seems like quite a large impact.
Take it for what it is. A beautiful expression of what the human mind is capable of imagining. (think da vincia and helicopter designs 500 years ago...)
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I think there's a big misunderstanding here. I'm not referring to the authors of the paper, but to 1) the content of a _Wired_ magazine online blog, and specifically to *reader comments* on that blog. That's what my dander was up about, not the authors of the actually paper. The paper and its authors are fine and dandy, hunky dory, peachy keen with me.
Yes, absolutely. Tweaking Lambda as they envision it is pure quantum. And that results of that tweaking are applied to a GR solution, which describes what it does.
The main calculation of the origin (and potential manipulation) of the necessary negative energy is completely quantum field theoretic so, respectfully, the above quote is unjustified from Richard. (note section where Zeta function regularization is used in the divergent sum and integral).
Again, I wasn't complaining about the paper or the authors, just some idiot comment on a blog, which said there was no GR involved in this, as there was with Alcubierre, just pure quantum theory. That is what I was talking about.
Of course the authors here acknowledge Alcubierre. Anyone who knows their rear end from a hole in the ground about it would. They've just thought up another way to do it, and more power to them. I'm right there in the stands pulling for 'em. Go, go, go, let's figure it out.
-Richard
Newbie
my apologies richard...I misread your post, and upon your kind clarification agree with you fully.
Hate to bring up politics here, but something that bothers me a lot...I read on bbc news recently how the projected total cost of the iraq war is around 2.7 trillion.
Thats a lunar base...a manned mars mission, a new orbiter and god knows what else.
Spock
Last edited by spock0149; 2007-Dec-25 at 03:57 AM.
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No problem.my apologies richard...I misread your post, and upon your kind clarification agree with you fully.
-Richard
Newbie
Hi richard. thats a great question. One I've been looking at recently in my work.You know, it might be fun and interesting to see how the Alcubierre "warp bubble" works roughly. Note that negative mass energy was required in the original version. This latest variation just does it with Lambda.
We can actually use Newton to get a general idea of how this negative mass thing works.
Consider the gravitational field of a negative mass. Now, think carefully about negative mass means. Does that mean just negative *gravitational mass* or does it mean negative inertial mass as well? What would the Equivalence Principle apparently say about this? What does F = ma say when 'm' is negative?
To consider this, it may help to write Newtonian gravity out in the full form, where M is the source, and m is the test particle. The inertial mass of the test particle is m_i, and its gravitational mass is m_g.
F = m_i*a = -G *M *m_g/r^2
The Equivalence Principle says m_i = m_g. Well, what about when m_g is negative?
Now, ponder that a bit and when you think you have the answer, consider this. Place a negative mass of -M and a positive mass of +M some distance 'd' apart and let gravity do what it will. What happens, there? It's very important What is the acceleration of both sources due to the other's field?
Now, all of you, don't be shy. Take a stab. Don't be surprised if you think the result is crazy. That's what negative mass is, weird and crazy, and that weird and craziness is what makes our warp bubble work.
-Richard
The 'obvious', or intuitive answer based on the equations you gave that negative mass is repelled from a gravitational source.
This idea is backed up in:
"Novel features of the energy momentum tensor of a Casimir apparatus in a weak gravitational field."
arXiv:0710.3495 [hep-th]
http://arxiv.org/PS_cache/arxiv/pdf/...710.3495v1.pdf
This is an exciting result as it has all sorts of anti gravity type applications.
Sadly the results is disputed in
"Gravitational and inertial mass of Casimir energy"
arXiv:0710.3841
http://arxiv.org/PS_cache/arxiv/pdf/...710.3841v1.pdf
Both papers are recent (the last few months).
'Sadly', the one that disputes the idea is written by Kimball Milton...quite the guru of the Casimir effect and negative energy. Of course that doesn't mean he is correct, and the other guys are actually performing an experiment to test their hypothesis...but when i guru talks he is usually correct.
I remain optimistic however.
spock
Order of Kilopi
So, negative mass should be repelled by a postive mass? That's what you'd think at first blush, sort of Maxwell with negative signs, where like "charge" attracts but opposites repel.
But that is a violation of the Equivalence Principle!
g = -GM/r^2.
Consider a negative test mass of '-m_g', negative gravitational mass. The force is indeed positive:
F = -m_g*g = GM/r^2. Positive, radially outward.
But the all important thing is the inertial mass. If we hold steadfast to the EP, that has to be negative, m_i = -m_g, so
a = F/m_i = g!
It is attracted to the positive mass. This seems to be demanded by the geodesic picture. Test particles follow geodesics of the space-time irregardless of their own mass, even if it is negative.
Now, consider a negative *source mass*, big 'M' = -M
g = -G(-M)/r^2 = GM/r^2. This is outward, repulsive.
A postive test mass, 'm' will be repelled. But, by the same sign flipping process above, a negative test mass '-m' will be repelled as well!
So, it seems that GR/EP says the postive mass attracts everything, including negative mass, while negative mass repels everything, both positive and negative.
Following that, consider two equal and opposite masses, +M and -M some distance r apart.
What happens? The result is so odd it blows your mind. Look an energy conservation there. Look at momentum. Is that conserved? Remember that minus sign on everything.
-Richard
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