Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

I Alcubierre warp threat correct?

  1. Feb 8, 2017 #1
    I'm interested in developments concerning the 'Alcubierre Warp Drive', specifically, the arrival problem:

    http://www.extremetech.com/extreme/...nihilating-whole-star-systems-when-you-arrive

    established in this paper, by a group from Australia:

    http://d1jqu7g1y74ds1.cloudfront.net/wp-content/uploads/2012/02/MatterOfMatter-revised-final.pdf

    I found a news article claiming that the problem turned out to be false, based on a mathematics error:

    https://www.extremetech.com/extreme...hip-called-enterprise-of-course#disqus_thread

    I could not, however, find any source to corroborate this. I even emailed the author of the article, who did not want to revisit the article and offered little information and didn't seem to remember his source, although he provided a link to a paper by Dr. Harold White of Eagleworks, NASA, in which he thought it was addressed:

    https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=0ahUKEwjym4WQuIHSAhVH74MKHRIjChMQFggcMAA&url=http://www.amarketplaceofideas.com/wp-content/uploads/2014/08/201100159361.pdf&usg=AFQjCNG9SIgNFLPa237i-rqNY03Dk59a8A&sig2=kwOEbTqyTUO5ynXe9LWfWQ

    I read through most of this and did not find a mention of the 'arrival problem'.

    I then attempted to contact Dr. White himself about the problem, twice, by email, with no response.

    So, that brings me to this forum. Is anyone aware of any mistake in the paper by the Australian group? To what extent has it been peer reviewed?

    Thanks all!
     
  2. jcsd
  3. Feb 16, 2017 #2
    Thanks for the thread! This is an automated courtesy bump. Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post? The more details the better.
     
  4. Feb 16, 2017 #3
    Upon reading the Australian paper, I've noticed that they only use the bubble configuration initially proposed by Alcubierre, which as I understand requires far too much energy to be possible to implement. The later bubble configuration proposed by White, which is instead a ring, apparently is not mentioned in the Australian paper. So my question is, will the altered bubble configuration proposed by White still produce the arrival problem? Please help guys. I'm an engineer not a physicist, so it would take me time I don't currently have to learn the physics behind the Australian paper enough to come to a conclusion.

    Thanks
     
  5. Feb 16, 2017 #4

    PAllen

    User Avatar
    Science Advisor
    Gold Member

    If there was a refutation, one would expect a paper to exist on arxiv citing the original paper. The only paper on arxiv citing the original paper you mention is one showing that the drive becomes more practical if you assume GR is wrong, and a particular alternative theory of gravity is used instead.

    https://arxiv.org/abs/1202.5708. (Original paper on arrival catastrophe)

    https://arxiv.org/abs/1208.3706 (only referencing paper found via arxiv cited by search)

    If this latter is the so called refutation, it requires that GR be wrong. Further, most physicists believe the whole NASA effort is ill founded because GR requires exotic matter (negative energy) to produce a warp bubble, and they see nothing in the NASA plan that could possibly produce negative energy.
     
    Last edited: Feb 16, 2017
  6. Feb 16, 2017 #5
    Hello,

    As it takes time and attention to a problem before papers are produced, it is certainly plausible that a feasible refutation exists that has not been identified and produced in the literature. That refutation need not necessarily be an alternative version of general relativity; it could be that the alternative bubble configuration had not been considered. I am aware of the skepticism in this area, and that is likely to generate inertia with regard to proper peer review. That is why I was asking here for someone who may be interested to actually sit down and check it out.

    With regard to the negative energy required, yes of course I am aware of that also, but as it is possible to violate the relevant energy conditions to achieve negative energy densities (otherwise the Casimir effect would not be possible), thus we know it is not infeasible to produce negative energy in some quantity. If it is possible to produce negative energy in any quantity, it is not irrational to assume that future technology may allow for this drive to be actually produced, even if it is infeasible now.

    I may be in the minority, but I believe that it is naive to assume that any given technology will remain indefinitely infeasible. Since it is possible to produce negative energy, and since some bubble configurations allow for conceivable amounts of it to work the drive, I feel it is only a matter of time before this drive is actually produced. If/when that is the case, the arrival problem will become extremely relevant.

    I still feel that it could be worth someone's time to check out the alternative bubble configuration to see if it is still prone to the arrival problem.
     
  7. Feb 17, 2017 #6
    Traveling faster than light will not cause one to arrive before leaving. A clock at the traveler's starting point will appear to have gone backward but a FTL return trip will not cause the traveller to return before leaving. Traveling infinitely fast could do it, maybe, but that would require "simultaneity" and that doesn't exist except for individual reference frames.
     
  8. Feb 17, 2017 #7
    Last edited by a moderator: May 8, 2017
  9. Feb 17, 2017 #8
    Last edited by a moderator: May 8, 2017
  10. Feb 19, 2017 #9
    The following maybe of interest.................................

    https://arxiv.org/pdf/0712.1649v6.pdf

    Warp Drive: A New Approach

    Abstract

    Certain classes of higher dimensional models suggest that the Casimir effect is a candidate for the cosmological constant. In this paper we demonstrate that a sufficiently advanced civilization could, in principal, manipulate the radius of the extra dimension to locally adjust the value of the cosmological constant. This adjustment could be tuned to generate an expansion/contraction of spacetime around a spacecraft creating an exotic form of field-propulsion. Due to the fact that spacetime expansion itself is not restricted by relativity, a faster-than-light ‘warp drive’ could be created. Calculations of the energy requirements of such a drive are performed and an ‘ultimate’ speed limit, based on the Planckian limits on the size of the extra dimensions is found.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted