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Space Transportation Science

Warp Drive Might Be Less Impossible Than Previously Thought 867

Posted by Unknown Lamer
from the warp-seven-engage dept.
runner_one writes "Harold 'Sonny' White of NASA's Johnson Space Center said Friday (Sept. 14) at the 100 Year Starship Symposium that warp drive might be easier to achieve than earlier thought. The first concept for a real-life warp drive was suggested in 1994 by Mexican physicist Miguel Alcubierre, however subsequent calculations found that such a device would require prohibitive amounts of energy, studies estimated the warp drive would require a minimum amount of energy about equal to the mass-energy of the planet Jupiter. But recent calculations showed that if the shape of the ring encircling the spacecraft was adjusted into more of a rounded donut, as opposed to a flat ring the warp drive could be powered by the energy of a mass as small as 500 kg. Furthermore, if the intensity of the space warps can be oscillated over time, the energy required is reduced even more."
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Warp Drive Might Be Less Impossible Than Previously Thought

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  • by Tanuki64 (989726) on Monday September 17, 2012 @07:20PM (#41369041)

    ...while never actually accelerating past the speed of light doing it...

    Does not matter. Special relativity does not make provisions how you travel. If you travel from point A in space to point B in space, be it by warp drive, be it by wormhole, be it by magic, faster than a beam of light could do it in vacuum, you travel ftl. And this means timetravel.

  • by Anonymous Coward on Monday September 17, 2012 @07:26PM (#41369127)

    The energy argument was completely secondary. The main objection (which is barely touched on in the article) is that there are some fairly strong proofs that you need exotic matter in order to actually implement the drive. My understanding is that the space-time configuration necessary for the warp drive has been shown to be impossible to create without exotic matter.

    Exotic matter, by definition, requires violations of the known laws of physics. In other words, the currently accepted laws of physics indicate that you need to break the laws of physics to make the drive work. This means that while the results in this article might have alleviated some secondary concerns, the main problem with this type of warp drive is still completely unaddressed.

    Of course, there are some people who will waive their hands and say "abracadabra - QUANTUM MECHANICS" to try and get around the exotic matter problem. But you are now trying to combine general relativity with quantum effects, so there isn't any firm foundation to base your arguments on.

  • Less impossible? (Score:4, Informative)

    by twotacocombo (1529393) on Monday September 17, 2012 @07:29PM (#41369159)
    Even a little bit impossible is still entirely impossible in my book.
  • by Samantha Wright (1324923) on Monday September 17, 2012 @07:38PM (#41369253) Homepage Journal
    I don't think you quite understood—the relative motion would be FTL, but so is the relative motion of two beams of light going in opposite directions when measured from an absolute frame of reference. That gets you up to 2c. No time travel. Hilarious amounts of dilation, sure, but nothing wibbly-wobbly.
  • by Tanuki64 (989726) on Monday September 17, 2012 @07:40PM (#41369279)

    *sigh* I know, it is hard to understand. But even if you use the warp drive you travel faster than light. The problems with time travel and the resulting paradoxes are not triggered by any kind of movement. Being at point A and suddenly being at point B in shorter time than a beam of light could go from A to B in vacuum is all that is needed.

  • by blueg3 (192743) on Monday September 17, 2012 @07:48PM (#41369357)

    This is actually one of the fundamental observations that led to relativity (and why the speed of light is the fastest information or energy can travel).

    Light moves away from you at exactly the speed of light, regardless of what your velocity is. If you're travelling at 0.99c (relative to a "stationary" observer) and you shine a light forward, it looks like it's moving at speed c away from you. Shine a light backwards, looks like it's moving speed c away from you. To the stationary observer, both beams of light *also* look like they're travelling at exactly speed c (and you look like you're travelling at 0.99c). So the stationary observer's perception of how you and the beams of light are moving relative to one another is different from your perception of the same thing. (However, both are equally valid.)

  • by Your.Master (1088569) on Monday September 17, 2012 @07:58PM (#41369449)

    Here is a relatively understandable explanation of why beating a photon to its destination implies time travel, even if you don't locally travel faster than light: http://www.theculture.org/rich/sharpblue/archives/000089.html [theculture.org]. Basically, if you can pass stuff along at FTL between people at sub-light speed, and those people are moving relative to one another, you can send stuff into the past.

    There *are* workarounds. A fairly comprehensive list is here:

    http://www.physicsguy.com/ftl/html/FTL_part4.html#subsec:specialframe [physicsguy.com]

    They're all kind of about relativity being wrong, and there's no evidence any of these are true. Mostly wishful thinking on the part of people that want to believe we can have an interstellar civilization but can't quite let go of causality. Briefly:

    1. FTL takes you to a parallel universe. So if you try to kill your past self, there's no paradox and you keep living because it was actually your counterpart in a different universe.
    2. There's some unknown physics that would prevent using FTL to violate causality. So even though there's technically time travel in some sense, it has no practical use and therefore you could say it isn't "really" time travel.
    3. A specific case of the above: perhaps the act of travelling FTL prevents any other FTL travel within a certain spacetime "radius".
    4. Violate relativity by having a "true" frame of reference with a "true" sequence of events. All FTL takes place in that context and is theoretically unlimited in speed. Within any other frame of reference, it looks like a speed limit, but still possibly faster than light speed.

  • by Tanuki64 (989726) on Monday September 17, 2012 @08:25PM (#41369677)

    Here you find a better explanation in the links:

    http://science.slashdot.org/comments.pl?sid=3124243&cid=41369449 [slashdot.org]

    http://science.slashdot.org/comments.pl?sid=3124243&cid=41369345 [slashdot.org]

    I'd say you take a few more physics classes.

  • by nine-times (778537) <nine.times@gmail.com> on Monday September 17, 2012 @08:34PM (#41369743) Homepage

    the relative motion would be FTL, but so is the relative motion of two beams of light going in opposite directions when measured from an absolute frame of reference.

    Nope. First, there's no such thing as an "absolute frame of reference". That's the really cool thing that Einstein proved, which gets referred to as "relativity". When two beams of light going in opposite directions are measured from any frame of reference, both are going c, neither are going 2c. Even if you were traveling along behind one of the beams of light going at 99% c, each would still only be going c.

  • by Nyrath the nearly wi (517243) on Monday September 17, 2012 @08:38PM (#41369773) Homepage

    No, nothing can go faster than the speed of light because it will violate causality. Which is more or less forbidden by the entirety of physics.

    The only way to avoid this is by some magic-juju like Parallel Universes, Consistency Protection, Restricted Space-Time Areas, or Special Frames (with Special Frames forbidden by Relativity). All of which look like desperate hand-waving, if you examine them closely.

    http://www.projectrho.com/public_html/rocket/fasterlight.php#id--Causality

  • by hoggoth (414195) on Monday September 17, 2012 @08:41PM (#41369807) Journal

    No pictures, but its true. There are some people who have waived their hands:

    http://www.thedailybeast.com/newsweek/2008/05/28/cutting-desire.html [thedailybeast.com]

  • by spike hay (534165) <blu_ice@@@violate...me...uk> on Monday September 17, 2012 @08:55PM (#41369909) Homepage

    For chrissake:

    Here [everything2.com]

    FTL implies at least backwards communication is possible under any method you can think of. If you get get to Alpha Centauri by stuffing yourself in your ass, it will still allow backwards time travel.

  • by Samantha Wright (1324923) on Monday September 17, 2012 @09:08PM (#41370009) Homepage Journal
    Absolutely [youtube.com].
  • by Cyberax (705495) on Monday September 17, 2012 @09:09PM (#41370019)
    There are no proofs that it's impossible to create a warp drive without exotic matter. It's just that we know several configurations of exotic matter that can produce warp drives.
  • by shutdown -p now (807394) on Monday September 17, 2012 @09:26PM (#41370109) Journal

    The light won't move faster. Instead, the frequency will be insanely high. Your infrared emitting tungsten filament bulb will be emitting gamma ray photons.

    Not to you, it won't. Only to that observer, relative to which you were moving at 0.99...c in the first place.

    If you are going 100% speed of light, you will *never* succeed in toggling the switch.

    You can't reach c while having any mass, so if you're going at c, then there's no switch.

  • by Jane Q. Public (1010737) on Monday September 17, 2012 @10:21PM (#41370479)

    "Exotic matter, by definition, requires violations of the known laws of physics."

    No, it doesn't. Antimatter is one valid type of "exotic matter", and it has been manufactured in labs in various (small) amounts for many decades now, without a physics violation in sight.

    Further, there is nothing theoretically preventing us from manufacturing it in fairly large quantities, as long as it can be kept in magnetic containment.

  • by Jane Q. Public (1010737) on Monday September 17, 2012 @10:41PM (#41370615)

    "... we can see it in certain configurations of regular matter, such as the Casimir effect."

    What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

  • Re:Negative Mass (Score:4, Informative)

    by Jane Q. Public (1010737) on Monday September 17, 2012 @10:43PM (#41370633)

    "In fact, I propose that anti-matter has negative mass, not opposite charge as generally accepted."

    That might have been a viable theory half a century ago or more. But antimatter has been observed to have positive mass.

  • by Anonymous Coward on Monday September 17, 2012 @11:59PM (#41371081)

    I can't believe this post was rated "+4, Interesting". Time dilation means that as you acquire more energy (i.e. the faster you go), time will pass slower and slower.

    So in effect you could in theory go through large distance (say, 1 light year) in what would subjectively (for the traveller) appear to be 1 second. If you take another second to come back, then the stationary element is now 2 years older : it saw the traveller spend one year to go one way and another year to come back.

    So in the case if your ships going opposite directions, if they go for a year (from the stationary point of view) in opposite directions at almost c, then they will be almost 2c apart. Except that from their perspective, they are only 2 light seconds apart now. And yes from each moving ships perspective, the other one would be looking like it's going faster than light, redshifting like crazy, etc.

    FTL "apparent" movement is not uncommon at all. For example, take alpha centauri. 1 light year away. Revolving around us in 24 hours. So doing a great 2 * pi * (1 light year) every 24 hours... apparently faster than light, except it's not.

  • by khayman80 (824400) * on Tuesday September 18, 2012 @12:54AM (#41371319) Homepage Journal

    "Exotic matter, by definition, requires violations of the known laws of physics."

    No, it doesn't. Antimatter is one valid type of "exotic matter", and it has been manufactured in labs in various (small) amounts for many decades now, without a physics violation in sight.

    Antimatter certainly isn't common, but it's not "exotic matter" [wikipedia.org]. Stable wormholes and the Alcubierre drive require using exotic matter that has negative mass-energy, which would violate the weak energy condition [wikipedia.org].

    "... we can see it in certain configurations of regular matter, such as the Casimir effect."

    What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

    The Casimir effect is the best known example of negative energy [wikipedia.org]:

    Morris, Thorne and Yurtsever[4] pointed out that the quantum mechanics of the Casimir effect can be used to produce a locally mass-negative region of space-time. In this article, and subsequent work by others, they showed that negative matter could be used to stabilize a wormhole.

  • by Cyberax (705495) on Tuesday September 18, 2012 @01:36AM (#41371497)
    Nope. He has shown that that one configuration requires exotic matter. He hasn't proved that in the general case as that's incredibly hard to do it - the equations of the general relativity do not impose a lot of boundary conditions.

    Moreover, even the Alcubierre drive might be possible with only positive matter if one uses a dynamic metric. I've seen a paper about it a few years ago, but I can't find it.
  • by khayman80 (824400) * on Tuesday September 18, 2012 @05:19AM (#41372379) Homepage Journal

    What does the Casimir effect have to do with it? That is merely a demonstration of so-called "zero point" fluctuations. It isn't "negative energy", except to the extent that you have particles and their counter-particles spontaneously arising at the same time. Even so, in the case of the Casimir effect it exerts a net positive energy on the affected mass.

    The AC is terse but correct. The Casimir effect [wikipedia.org] occurs because vacuum fluctuations are suppressed between two parallel conducting plates that are placed very close together. Maxwell's equations force E=0 inside perfect conductors, which means that vacuum fluctuations with a half-wavelength longer than the separation between the plates can't exist between the plates. Because they exist in the vacuum outside the plates (which is defined to have zero energy), the energy inside the plates is actually negative. The attractive force implies negative energy between the plates because force is the negative gradient [wikipedia.org] of potential energy.

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