back to article CURSE you, EINSTEIN! Humanity still chained in relativistic PRISON

Disappointing news on the science wires today, as new research indicates that a possible means of subverting the laws of physics to allow interstellar travel apparently doesn't work. Curses! Can nothing pierce this damned rubber sheet? As we are told in a new paper just published in hefty boffinry mag Science: Neutron …

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  1. Yag
    Thumb Up

    The more you know, the less you're sure...

    Thumb up to Marten van Kerkwijk's open mind.

    1. Anonymous Coward
      Anonymous Coward

      Re: The more you know, the less you're sure...

      "The more you know, the less you're sure"

      The unfortunate corollary to that is "the less you know, the more certain you are", which is the reason we have so much political and ideological stupidity in the world

      1. I ain't Spartacus Gold badge
        Happy

        Re: The more you know, the less you're sure...

        I'm certain you're wrong about that...

        1. Anonymous Coward
          Anonymous Coward

          Re: The more you know, the less you're sure...

          "I'm certain you're wrong about that..."

          Oh, I don't know...

      2. Maksim Rukov
        Boffin

        Re: The more you know, the less you're sure...

        Yes, it's called the Dunning-Kruger effect.

        http://en.wikipedia.org/wiki/Dunning%E2%80%93Kruger_effect

      3. trottel

        Re: The more you know, the less you're sure...

        Even though i agree with your statement as it is, in this case you would refer to the contra-positive, which would be "the more certain you are, the less you know".

      4. Fazal Majid

        There's a name for it

        It's called the Dunning-Kruger effect.

  2. hplasm
    Unhappy

    Damn....

    Next contestant!

    1. Turtle

      @hplasm: Re: Damn....

      "Next contestant!"

      As far as I'm concerned, there could not be enough upvotes for that!

      1. hplasm
        Happy

        Re: @hplasm: Damn....

        Thanks.

  3. Anonymous Coward
    Anonymous Coward

    Stupid question

    I'm posting this anonymously as I'm sure there's a really, really, really easy answer to this thought experiment but I'm too thick to know it.

    If I had a metal rod 100 million miles long sitting in a frictionless universe, and I push one end of the rod, surely the other end moves immediately, rather than taking however long light takes to travel 100 million miles. Which means that this violates the speed of light as nowt can travel faster than that, even information. I have heard about Quantum Entanglements and homeopathic medicine but assume this is not at all related as I have no idea what a quantum is except it's probably smaller than a peanut and am not sure what memory water really has.

    Now I'm 100% positive that Einstein was brighter than me, indeed suspect the vast proportion of the world will fit that large set, but nobody has explained to me why my thought experiment is wrong.

    Any takers who can write in crayon and use very, very small words? Please?

    1. hplasm
      Boffin

      Re: Stupid question

      The rod would probably compress due to inertial effects, and the push would propagate down it a at speed <c.

      Sadly, it's the information of the push which is limited.

    2. Anonymous Coward
      Anonymous Coward

      Re: Stupid question

      hmmm I'm not sure that will work as imagined since that amount of metal will have some compressibility and will take some huge effort to push the end of the rod enough distance to move the remote-end although I see your point about faster-than-light.

      1. Michael Wojcik Silver badge

        Re: Stupid question

        that amount of metal will have some compressibility

        Any rod of metal has "some compressibility". The rigidity of a solid is the result of electromagnetic interactions, which are quite willing to redistribute mechanical force orthogonally to the axis of compression. So unless your "rod" is a single layer of atoms, it can always be compressed - it will just expand to the side as necessary.

        And since mechanical force travels by propagating EM interactions, it can't travel down the rod faster than EM can propagate along it. There's no need to invoke compression for this thought experiment; the OP's assumption that the far end of the rod moves immediately is simply wrong. Atoms at the near end move, which decreases their distance to their nearest neighbors, which increases the electromagnetic force between them and their neighbors. Once that force propagates to the neighbors, the neighbors are accelerated by it and move in the direction that the rod is being pushed. Nothing happens immediately.

    3. Anonymous Coward
      Anonymous Coward

      Re: Stupid question

      Equally not an expert on the subject, but the first flaw I notice is that your rod (snigger) is "sitting in a frictionless universe", which is automatically not our universe and so other laws of physics are non-comparable.

      Other than that, I don't think I can be of much help. I'd assume material strength/elasticity, friction, force required, etc., would be enough to make it impossible.

      On the entanglement side, though, my understand is that entanglement can potentially cause a correlated effect to occur instantly at a location over a light-year away, but this (with our current understanding) couldn't be used of itself to transmit information.

      The common example (which I believe I've seen repeated by other commentards) is the "two cars" thought experiment:

      You have two cars (one red, one blue) hidden under sheets, and both are moved a light-year away from each other. You remove the sheet from one car and immediately know the colour of the other car. You aren't receiving this information faster-than-light, but the effect appears to be the same from your position.

      IANAQM

      1. Alfred

        The "two cars, one red one blue" thing

        This is better put as "you have two cars, and if you ever check, one will be red and one will be blue, but at the moment because you haven't checked it's not decided - it's not a case that one is already red and you just don't know it. It isn't. The universe hasn't decided yet. It's not red. It's not blue. No decision has been made. When you look at one, the decision is made, and if the one you looked at is red, the other one will be blue whenever someone checks, even if they check a second later a light year away, so did some kind of information travel that light year in one second?"

        The key thing is that the universe doesn't decide on the colours until you check.

        1. keith_w
          Devil

          Re: The "two cars, one red one blue" thing

          Schrödinger's car?

          1. MJI Silver badge
            Devil

            Re: The "two cars, one red one blue" thing

            <- red car

            Red car Toyota GT86

            Blue car Subaru BRZ

            Same car different colours.

        2. Anonymous Coward
          Anonymous Coward

          Re: The "two cars, one red one blue" thing

          Whenever I buy a car it's the wife that has the last word on the colour, not the universe.

          1. itzman
            Holmes

            Re: The "two cars, one red one blue" thing

            "Whenever I buy a car it's the wife that has the last word on the colour, not the universe."

            When she became your wife she became a relative.

            So its just general relaitivity, after all.

            Simples!

      2. Midnight

        Re: Stupid question

        Where the car analogy starts getting interesting is if you could reach under the blanket with a tin of blue paint and turn one of the cars blue without ever looking at it.

        If the other car must be red because the one you just painted is blue then you've got a fun toy that you won't want to think too hard about.

    4. C 18
      Meh

      Re: Stupid question

      Okay, I'll bite...

      Imagining the rod to be constructed of a non-compressible material in a frictionless universe etc etc...

      Both ends of the rod move at the same speed, which is as fast as you can push one end. This must be less than the speed of light.

      As for information, well, it's not made of matter... so, excuse the pun, it doesn't matter...

      1. Anonymous Coward
        Anonymous Coward

        Re: Stupid question C 18

        Information is near enough the same thing. Everything in the universe is made of information and matter (or information and energy depending how you squint). "Nothing" can move faster than light in this universe (so far as we can tell with all our observations and calculations).

        This should not be a problem though. It's only humans that are concerned with the speed of travel or progress, photons, protons and information can take as long as it wants. ;)

        1. Anonymous Coward
          Facepalm

          Re: Stupid question C 18

          PS, that is "nothing can move faster than [c]", as "the speed of light" is not necessarily "the speed light is traveling at". :P

        2. C 18
          Joke

          Re: Stupid question C 18

          Everything is made from information.

          That's what you think!

      2. Benchops

        Re: Stupid question

        I'm a bit worried about the speed the other end of this non-compressible rod is travelling at as the earth slowly rotates. It's going to do some damage to the first thing it hits, and it might jar your elbows a bit.

    5. Anonymous Coward
      Boffin

      Re: Stupid question

      The metal rod is not infinitely rigid. Therefore it's like a very very stiff spring. When you push one end, the atoms are momentarily compressed, and pass that force onto the next atoms as they start to move and so on down the rod. You're pushing against the inertia of the rod, making your end accelerate. That wave of compression passes along the rod at less than the speed of light until the other end starts moving too.

      When you stop pushing, the atoms at your end spring back, and eventually the whole rod returns to its original shape. Now the whole rod is moving through your frictionless universe, but the whole rod (including both ends) is moving at a steady speed. There's no actual 'change' (read 'information') going on anymore.

    6. This post has been deleted by its author

    7. John H Woods Silver badge

      Re: Stupid question

      There are no stupid questions :-) But this might be a stupid answer...

      Compress your thought experiment back down to a hundred meters ... You hold one end and tap it - I hold the other and listen. What you are doing is (slightly) moving the rod and transmitting a wave - this travels at the speed of sound (albeit in metal - I think that's around 10x faster than in air) but it's a lot slower than light, never mind instantaneous.

    8. Charles 9

      Re: Stupid question

      Imagine if you will the venerable Saturn V rocket on the verge of takeoff. The rockets at the bottom fire and start pushing up the bottom of the rocket. However, the top of the rocket does not react momentarily. For that instant, the rocket compresses and propagates up the height of the rocket until the top start moving.

      A similar thing can be observed with the humble Slinky. There is an El Reg article about a Slinky experiment that discusses the phenomenon at length.

      Basically put, nothing in the universe is perfectly rigid. Apply a force at one end of the rod and, instead of the whole rod moving at once, the rod will compress at that end, and a compression wave will run down the length of the rod at subuminar speed. The other end won't react immediately because of this.

      Incidentally, this compression phenomenon exists regardless of friction, as it can also occur in space where friction is as close to zero as we can get it.

      1. Robin Bradshaw
        Thumb Up

        Re: Stupid question

        I think the letting go of a falling slinky has been covered most impressively by Veritasium on youtube here:

        https://www.youtube.com/watch?v=uiyMuHuCFo4

        The slow motion video is quite captivating.

    9. Brewster's Angle Grinder Silver badge
      Pint

      Re: Stupid question

      I'm afraid that's physically impossible in so many ways.

      A gravitational force would act along the axis of the rod, compressing the centre until it snapped. Even a small alignment error would cause the rod to twist and buckle as the ends were attracted to the centre. Unless you got your push perfectly aligned, the same thing would happen. (I've ignored the problem of not having the rod spinning in the first place.)

      If you manage those problems, then there is no perfectly rigid material you could use to manufacture the rod so the best case is your "push" travels down the rod as a compression wave (sound wave) with the other end moving many years later. But it's more likely it would behave as if one end was anchored: rebounding elastically if the push was small; snapping if it was too big.

      1. hplasm
        Happy

        Re: Stupid question

        Silly rabbit never heard of unobtainium.

      2. Mike Tubby
        Go

        Re: Stupid question

        Mine's the purple one... its neither red, nor blue but both red and blue at the same time... funny stuff this time travel ;-)

        G

    10. Ru
      Boffin

      Re: Stupid question

      If I had a metal rod 100 million miles long sitting in a frictionless universe

      A frictionless universe won't help you here. Instead you'd need an incompressible rod... not something you can make out of normal matter (see also: black holes). You push the end of the rod, you generate a compression wave, and that will travel at a finite speed even in incredibly dense material (do a quick search for 'speed of sound in neutronium', for example).

      Now, I Am Not A Theoretical Physicist, but I rather suspect that you could only manufacture the required massless and incompressible rod if you already had some sort of superluminally propagating force, making it a bit of a circular argument!

    11. Fred 4

      Re: Stupid question

      see this video - at about 50 secs. (sorry I haven't figured out how to link to a specific time)

      http://www.youtube.com/watch?v=JsytnJ_pSf8

      the effect on your 100 million mile long rod would about the same, except it would take a bit longer to propigate.

      1. Arbee
        Boffin

        Re: Stupid question

        > (sorry I haven't figured out how to link to a specific time)

        It's actually really easy with YouTube.

        You just need to add a "t" parameter, giving the number of minutes and seconds you want to skip, e.g.

        http://www.youtube.com/watch?v=JsytnJ_pSf8&t=0m50s

    12. Irongut

      Re: Stupid question

      Only if your rod was poking a spherical cow.

      1. hplasm
        Devil

        Re: Stupid question

        Argh! Flashbacks!!

    13. Richard Wharram

      Re: Stupid question

      "and homeopathic medicine"

      Water has no memory and Homeopathy does not work. You are now fully educated on the subject.

      1. Robert Helpmann??
        Childcatcher

        Re: Stupid question

        Homeopathy does not work

        Well, it does, but you have to choose your victims patients carefully. As homeopathy's effectiveness is equivalent to that of a placebo, it should be administered only to hypochondriacs and other true believers in order to properly "treat" what ails them.

        1. Tom Melly

          Re: Stupid question

          In fairness, placebos are very effective for pretty much everyone. Bizarrely, it doesn't even matter much if you're told that you're taking a placebo. Oh, and it helps if you're charged a lot of money. Seriously.

          Anecdotally, I was given homoeopathic medicine when I was covered in very virulent mosquito bites. It worked brilliantly within minutes, and I know that stuff is a load of bollocks.

        2. Loyal Commenter Silver badge

          Re: Stupid question

          As homeopathy's effectiveness is equivalent to that of a placebo, it should be administered only to hypochondriacs and other true believers in order to properly "treat" what ails them.

          Studies have shown [sic] that the placebo effect works even then the patient knows they are receiving a placebo.

          Homeopathy is total bollocks though, along with beliefs in 'crystal energy', any sort of 'quantum healing' and sky fairies.

          1. Benchops

            Re: Stupid question

            I feel better as soon as the doctor's prescribed me something.

            And really I would believe a placebo can make me feel better even if I know it's a placebo. All you have to do is believe in the placebo effect!

      2. hplasm
        Joke

        Re: Stupid question

        You say that now! I gave up homeopathic medicine completely and ended up in hospital with an overdose!. And the jug of water by my bed wouldn't let me forget it!!!

    14. Maddad

      Re: Stupid question

      I've thought about that as well. I think the rod will compress when you push on it. Even a miniscule amount of compression adds up over 100 million miles, and you're trying to move a lot of inert mass. Eventually the rod will decompress and the far end will move, but not simultaneously with the near end.

    15. Francis Boyle Silver badge

      In fact

      The rod could be completely mechanically incompressible (in the sense that the inter-atomic forces were effectively infinite) and the effect would still propagate at the speed of light since everything including forces propagates at the speed of light. The lightspeed limit is implemented at layer 1 of the universe.

      1. Ken Hagan Gold badge

        @Francis Boyle

        Actually one of the reasons why the rod *couldn't* be incompressible is because the effects of inter-atomic forces can only propogate at the speed of light.

    16. Greg 10

      Re: Stupid question

      Propagation is not instantaneous. Each atom bears some pressure and passes it on to the closest one.

      Pushing on a 100 million miles long rod would not move the other end instantaneously.

      You can actually easily test this in reality.

      Just take a 2 meters long spring (ok, hard to get by but you can engineer one much more easily than a 300 million miles long pole). Push on one end.

      By now you are imagining what's happening and you don't need to actually test it. It probably is obvious to you that the spring will compress some on your end beforespringing on the other end (and that'd be true even without and friction).

      Well, your pole is the same. It's way less compressible than a spring, but then you'd have to apply inifinitely more pressure to actually give it the same acceleration as the spring. So in the end, it'd would compress, that compression would propagate at some speed actually probably way below the speed of light, and your thought experiment problem is solved.

      All along it was not a real problem but just the fact that it's not a real thought experiment but just assuming that because you don't see the delay at our scale, there isn't one. Even at our scale, there is.

      1. Loyal Commenter Silver badge

        Re: Stupid question

        See also:

        Dropping a slinky

        The speed of sound in a slinky is much lower than the terminal velocity of the spring, if you hold one end of the spring and drop it, the bottom of the spring will not start moving before the top reaches it, as the acceleration under gravity will quickly cause its speed to exceed the speed of sound in the spring (the speed at which the compression wave propagates).

        It's a cool experiment, but here's the question - when you let go of the top of the spring, does the bottom become weightless?

    17. This post has been deleted by its author

    18. nanchatte
      Stop

      Re: Stupid question

      Sorry, alternative medicine is by definition medicine that can't be proven to work.... Do you know what they call alternative medicine that is proven to work? Medicine.

      Also, you'd need an incompressible rod, which doesn't exist.

    19. nytemunkey

      Re: Stupid question

      VSauce covered this topic on their YouTube channel. The speed of push is slower than light, a lot slower. It actually moves around the speed of sound. You should check the video out, it's really cool. http://www.youtube.com/watch?v=Do1lm9IevYE around 5:15 is the bit about push speed.

    20. Jamie Jones Silver badge
      Thumb Up

      Re: Stupid question

      "I'm posting this anonymously as I'm sure there's a really, really, really easy answer to this thought experiment but I'm too thick to know it."

      Been there, done that!

      "If I had a metal rod 100 million miles long sitting in a frictionless universe, and I push one end of the rod, surely the other end moves immediately,"

      Actually, that's something I've wondered about too - though I would assume some whizzo rigid carbon nano wotsit or similar!

    21. Gene Mosher

      Re: Stupid question

      Your rod is actually just a chain of molecules, each bound to the others, in theory, by strong interaction. If all of the molecules in a chain 100 million miles long were to affect each other then this would certainly NOT instantly occur everywhere. Every single molecule along the way would have to interact with every molecule next to it along the entire length before the interaction would reach the other end. The rod is not a 'thing', but rather is a chain of molecules. It may well be that the other end of such a chain of molecules would not even move at all.

    22. Chris Holford
      Boffin

      Re: Stupid question

      Any real rod has mass and elasticity;

      You could model this by stretching a 'slinky' spring out on a smooth table. Give one end a push and you can see the pulse propagate to the other end. It takes a non-zero time for the pulse to travel the length of the slinky.

    23. Ed_UK
      Boffin

      Re: Stupid question

      Not a supid question!

      As others have mentioned, the inertia of the material comes into effect, as does its rigidity. These figures determine how fast a wave can travel through your material. In other words, the speed of sound. For steel, this is typically 5800 to 6000 m/sec, travelling as a compression wave. Attempt at ASCII art:

      >|___|__|_||_|__|___|___|___...

      Ignore the rod's other vibrational modes (e.g. longitudinal) because they'll be much slower.

      If your hypothetical rod were 100 million miles long, most of it would be in free space, which is indeed pretty frictionless. Even if you used a more manageable 100m rod, (suggested by someone) then suspending it by threads would give an adquate approximation. Attach microphones to both ends, connect to amplifiers, detectors and a start-stop timer. Calibrate by moving the far mic upto the near mic (keeping the same long cable attached).

      1. Imsimil Berati-Lahn
        Thumb Up

        Re: Stupid question

        With this ASCII art you are really spoiling us.

    24. croc

      Re: Stupid question

      "

      Stupid question

      I'm posting this anonymously as I'm sure there's a really, really, really easy answer to this thought experiment but I'm too thick to know it.

      If I had a metal rod 100 million miles long sitting in a frictionless universe, and I push one end of the rod, surely the other end moves immediately, rather than taking however long light takes to travel 100 million miles. Which means that this violates the speed of light as nowt can travel faster than that, even information. I have heard about Quantum Entanglements and homeopathic medicine but assume this is not at all related as I have no idea what a quantum is except it's probably smaller than a peanut and am not sure what memory water really has.

      Now I'm 100% positive that Einstein was brighter than me, indeed suspect the vast proportion of the world will fit that large set, but nobody has explained to me why my thought experiment is wrong.

      Any takers who can write in crayon and use very, very small words? Please?"

      You really need to substitute in a hydraulic cylinder for your rod...

      1. Dave 126 Silver badge

        Re: Stupid question

        I've upvoted the OP AC - he humbly posted an honest question, and thus prompted some interesting replies, most of them along the right lines.

    25. itzman

      Re: Stupid question

      the transmission is, in the limit, between atoms in the rod's lattice. there is no evidence hat any of the forces inside atomic structure propagate faster than light. so a compression wave will travel down the structure at essentially the 'speed of SOUND' in that medium.

    26. nagyeger

      Re: Stupid question

      No no no, what you need is "Light Inextensible String", available by the mega-furlong

      in any mechanics problem near you when you were 18 or so. You don't even need to

      turn off friction.

      Way back when there were still shops selling videodiscs (OK maybe I'm exagerating)

      some friends and I proved that it violated causality.

    27. despun

      Re: Stupid question

      As others have said, you're assuming a perfectly ridged body, and there isn't any such thing. In fact, special relativitive is ruling out perfectly ridged bodies. The mechanism is that you push one end, the interactions with the molecules, electrons, whtever pushing the next molecule along is takes a finite time, it's light speed limited.

    28. Michael Dunn
      Headmaster

      Re: Stupid question

      Problem with your thought experiment: prior to carrying out the experiment, you have to get the rod into place. This would probably vitiate your attempt to actually do the experiment. As mentioned in another comment, tapping the end of the rod would set up a wave in the rod travelling at the speed of sound to the other end, not superluminal transfer of info!

      It's like the famous twins paradox often cited in discussions of relativity, or at least the Lorentz equations, where the twin travelling at the speed of light does not age while his pedestrian brother gets old. What is not usually included in this anecdote is the fact that the travelling twin, on leaving his brother, will then have to accelerate up to the speed of light, and at the end of his journey, decelerate back down again, and these two phases of his journey will probably occupy as much time as would have been passed in the interim by his stationary brother. The relativity relevance of the story merely deals with their relative velocities once the moving twin has achieved light speed and before he comes "down to earth" from it.

      I'll post this as a pedant - which I am - not as a 'simplicius'* enquirer.

      *cf Galileo's dialogues.

  4. Anonymous Coward
    Anonymous Coward

    Do we know the "fault" is on the side of GE and not QM? At the moment both theories seem incredibly accurate to me.

    1. This post has been deleted by its author

      1. Muscleguy
        Boffin

        @HolyFreakinGhost

        " We *can* write down loop quantum gravity, which is a first-quantised vacuum theory, but mapping from LQG up to GR is to my knowledge still an unsolved problem"

        Which just goes to show that mathematics is a language, albeit a highly formalised and logical one. Languages can be used to write fiction as well as non fiction. When writing fiction, as the best show, you can describe perfectly internally consistent fictional universes, but they are not this universe. It has always seemed to me that many theoretical Physicists and String Theorists in particular forget this aspect of the language they write their theories in, and from this we get assumptions such as that the Mulitverse must be true because we can write consistent stories that require it to be true.

        As an experimental biologist I just sit back and say: 'prove it'. Because such descriptions don't look like this universe. I'm all for throwing up testable hypotheses for the atom smashers and the cosmologists to go see if they are true, but they have to testable. If you are building castles in the air with untestable buttresses supporting untestable towers and resting on untested assumptions then you are not doing science any more.

        1. This post has been deleted by its author

        2. itzman
          Headmaster

          Re: Prove it?

          "If you are building castles in the air with untestable buttresses supporting untestable towers and resting on untested assumptions then you are not doing science any more."

          No, but you are doing Climate Science :-)

      2. Anonymous Coward
        Anonymous Coward

        Thanks for that. While reading it I did find myself wondering if Gödel's theorem might apply to reality itself. The "universal constants" are the axioms and the mathematical relationships between them are the allowed rules of inference. Eventually we are bound to find some parts which can not, and can never be, reconciled.

        Just a thought.

        1. This post has been deleted by its author

        2. itzman

          Gödel et al

          You have hit upon a key issue in metaphysics.

          Self reference. All systems of thought that attempt to describe a universe in which the thinker exists, are self referential and all can be shown to contain essentially Gödelian type statements.

          Douglas Hofstader has explored this in some detail, and a very good outline description of the issues is Hilary Lawson's 'Closure' ..

          In popular culture of course the issues is raised in the 'Matrix'. A completely artificial universe is totally indistinguishable from a 'real one' if it fools all the senses all the time.

          Hilary Lawson's thesis is that it cant do that completely all the time, there will always be gaps. A place where some logical self referential statement will lead to complete and final uncertainty.

          WE (and I) suspect that the most glaring place today in our current scientific worldview is indeed areas like quantum physics. With the illogical conclusions that whether the cat is dead or not is 'caused' by our consciousness of its state. In his idea system, its not just the cat. EVERYTHING is 'caused' by our perception of it, in the sense that the world-as-we-know-it is not the real or the final world. It is brought into being by our attempts to intervene with it., and that intervention consists of a separation of 'us' from 'it' which both defines what we are and defines what the world of our perceptions will be. This has an exact analogue in quantum physics where it is the attempt to intervene in quantum reality that causes it to 'collapse' into classical 4D space from a radically difference phase space.

          All intersting ideas..

  5. TeeCee Gold badge
    Pint

    Inconsistencies with quantum mechanics.

    Given that every time we look very hard at something strange and new to observe it has a habit of proving Einstein right, maybe it's not relativity but quantum mechanics that has the glitches in it?

    Beer, because after a few of those later that might make sense.

    1. Destroy All Monsters Silver badge
      Headmaster

      Re: Inconsistencies with quantum mechanics.

      No.

      It's because they are two views on the same thing which we don't know what it is.

      And GR is difficult to test in the laboratory setting.

    2. Brewster's Angle Grinder Silver badge

      Re: Inconsistencies with quantum mechanics.

      You can "go the other way" and merge the other forces with gravity. The EM field works fine (Kaluza-Klein) and then the program begins to struggle. However it would require extra (really tiny) dimensions and IIRC LHC is close to ruling that out.

  6. jai

    wouldn't be practical though, would it?

    if I understand it right, you would have to get near the collapsing neutron star first, in order to make use of the warped space/time and slingshot yourself to an equivalent point on the other side? so it's still going to take years and years to get from Earth to the nearest collapsing neutron star, isn't it?

    Or is the solution to have a device onboard the ship that creates a collapsing neutron star of the right size as when you require it? I imagine the Health & Safety department of interstellar travel would have a field day with that though.

    i guess, perhaps this does explain why we haven't been wiped out by an alien invasion force yet. maybe we're not alone in the universe, but there's just absolutely no way to get to the next door neighbours to say hi.

    1. John H Woods Silver badge

      jai: "i guess, perhaps this does explain why we haven't been wiped out by an alien invasion force yet. maybe we're not alone in the universe, but there's just absolutely no way to get to the next door neighbours to say hi."

      A similar argument applies to Time Travel - if it were possible, they'd already have visited.

      1. Fred 4

        unless...

        you can't go back in time past the first existence of the time machine.

        TM created in June 5th 2050.

        on June 6th 2050 you can go back to June 5th, but no further.

        1. Midnight

          Re: unless...

          That would explain why half a second after we turn the bloody thing on, it either shorts out, blows up, or has a sperm whale fall on top of it.

        2. Anonymous Coward
          Anonymous Coward

          Re: unless...

          Interestingly, one version of the Tardis (multiple writers = no consistency) is that it can only travel in ITS past. So Gallifrey is in our far distant future. This neatly avoids many paradoxes in that nothing that a Time Lord does affects their own future; they're always simply doing things that, potentially at least, were known to have been done already before they set out. The Time Lords can not change their own future except by acting in their present, just as we (think we) do; they can not travel forwards to see what effect decisions will have and thereby make different ones.

          There is a vestige of this idea in that most Dr Who writers have stuck to the rule that the Doctor can only meet himself in extremely unusual circumstances which are dangerous to the structure of his own timeline. Aside from being a useful plot device rule, this can be seen as recognition of how much energy would be required to actually change one's own past by the transference of entropy from one "knowledge frame" to another and thereby alter the second frame, which is ultimately made up of all the states of matter in the universe.

          Of course, most Dr Who writers don't worry about any of this and there's far from being a "one true" theory of Time in the show. Sadly, recent stories (particularly the dreadful stuff that Davis wrote) have in fact been overly concerned with the time travel aspect as a thing in itself and not so interested in just using time travel as a mechanism for getting the Doctor and his assistants into an interesting story.

      2. Alfred

        Time travel

        There are (or at least, is one) time travel theorems that allow you to travel back only as far as the creation of the time machine. So upon inventing time-travel, it'll be useless to the creator (but would explain why the future people haven't visited).

        1. Ru
          Happy

          Re: Time travel

          Have a quick read of WIki History by Desmond Warzel for an entertaining view on timetravel.

          1. This post has been deleted by its author

      3. Harvey Trowell

        Or not though, I mean, there's also that...

        An alternative explanation could be that the Johnny Alien has picked up our radio transmissions and decided to give Earth the swerve on cultural grounds, viz., I have heard talk of the wonders of Blackpool's Golden Mile, but despite having the means to do so, have never felt the need to visit...

      4. John G Imrie
        Happy

        A similar argument applies to Time Travel - if it were possible, they'd already have visited.

        But I did visit. Next Thursday.

        1. Kevin McMurtrie Silver badge

          Re: A similar argument applies to Time Travel - if it were possible, they'd already have visited.

          Time travel would be possible with infinite computational power. Traveling back in time would be a matter of examining the state of the universe, reversing its path in a virtual environment, and then entering that environment or overwriting the present with it. Altering the present from the past would be calculating what changes a past event would have and then applying them in the present. Altering the future would be predicting what changes would be needed to arrive there and applying them in the present. You could argue that it's not really time travel but, if done well enough, there'd be no way to know the difference. Extremely narrowly scoped examples can already been seen on the Internet, in history books, the financial market, and in good brain washing. The scope of such hacking will increase over time.

          1. Anonymous Coward
            Trollface

            Re: A similar argument applies to Time Travel - if it were possible, they'd already have visited.

            Also: http://xkcd.com/1203/

            When you get the joke, you'll go "Aaaaah!"

            1. dlc.usa
              IT Angle

              Re: A similar argument applies to Time Travel - if it were possible, they'd already have visited.

              Then, if possible, he does the typically human thing and tries it again, establishing a closed loop for all eternity.

      5. Steve Knox
        Alien

        Time Travel - if it were possible, they'd already have visited.

        We have -- you just haven't been paying attention.

      6. A J Stiles
        Coat

        Time Travel

        It has already been invented (or rather, is going to have already been invented). The reason why they haven't visited us to tell us about it, is that going back a few minutes or hours to make witty remarks which people only thought of some time after the event soon became by far and away the major commercial application for time travel, and as a consequence the range of commonly-available time machines is restricted.

    2. Michael Wojcik Silver badge

      if I understand it right, you would have to get near the collapsing neutron star first, in order to make use of the warped space/time and slingshot yourself to an equivalent point on the other side?

      I admit I was thinking the same thing, but I've never gotten around to reading Haldeman's Forever War (I really should some day; I know it's a classic), so I don't know if he addresses this point.

      According to one article, the closest known neutron star is 250-1000 ly away, so we'd still be needing the big suitcase.

      Personally, my favorite fantasy space-travel mechanism is still Larry Niven's proposal to turn the entire solar system into a vehicle, by wrapping the sun with a big ol' ring of electromagnets (possibly in concert with building a full-on ringworld, because hey, while we're dreaming...), and then turning it into a really big ramjet aimed orthogonal to the ecliptic. Niven suggests that by the time you've thrown out an appreciable amount of solar mass (as reaction mass), you're scooping up enough interstellar hydrogen to make up for it. Now you have a "generation ship" that has the best life-support system anyone's ever seen. Just maneuver it into the neighborhood of an interesting stellar system, then use conventional rockets to visit. Space caravan!

  7. Anonymous Coward
    Anonymous Coward

    Relativity --the non existent theory.

    Space has a critical matter density of 3.6 E minus 25 kg/cubic meter. Its components (elementary particles) are in a state of perpetual harmonic oscillation at a rate C at 3E +8 cycles per sec.. It provides the motivation to create the gravitational acceleration towards the centre of bodies because the wavelength of the oscillations get compressed and merges . The concept of velocity in space is wrong . Transmigration of pressure takes place as waves like in air as sound or water. There is an axiomatic theory that has the answers . See www kapillavastu dot com slash index html to get details.

    1. Fred 4

      Re: Relativity --the non existent theory.

      manfrommars??

    2. Schultz
      WTF?

      Transmigration?

      sounds like you got it mixed up, it's Transformation, as in Transformative Hermeneutics of Quantum Gravity.

    3. DavCrav

      Re: Relativity --the non existent theory.

      Nurse! He's out of bed again!

    4. This post has been deleted by its author

      1. Anonymous Coward
        Anonymous Coward

        Re: Relativity --the non existent theory.

        I think Voyager's problem is it made manoeuvres along the way, and the uncertainty in those is larger than the Pioneer effect.

        The Pioneer anomaly has been looked at in detail, and radiation leakage was a candidate for the answer, but nothing convincing has been found. Certainly I would be in favour of a mission designed to check this and establish with certainty if it was simply a spacecraft artefact, or something genuinely different in our understanding of gravity.

        1. This post has been deleted by its author

          1. Anonymous Coward
            Anonymous Coward

            @HolyFreakinGhost

            Thanks for the link to that paper - a little more recent than the last I read on this, and as you say fairly convincing. Still, as you point out, it is still not answered to "discovery" levels of 3-sigma and above, and there is still galactic scale oddities to be addressed.

            We cant probe that sort of distance, but we could do a gravity mission beyond Earth to help resolve the Pioneer anomaly, one way or another, for good.

            1. This post has been deleted by its author

  8. dlc.usa
    Boffin

    Gravity Propagation Question

    The force you impart to the rod propagates through the entire rod much faster than light speed, but all the molecules only increase velocity per the force imparted. This does bring up the question of gravity propagation, however. If a mass pops into space-time, is its gravity manifested everywhere in the Universe instantaneously or does it propagate out from the mass, and, if the latter, at what velocity does it propagate? Inquiring minds want to know.

    1. Fred 4

      Re: Gravity Propagation Question

      c

      if our Sun exploded the moment you read this. It will take ~8 minutes for the gravitational change to reach us.

    2. Ru

      Re: Gravity Propagation Question

      The speed of gravity is apparently finite... I believe that's been known for some time. Newton thought it was infinite, but apparently observations of Mercury's orbit in the mid-1800s showed that the planet's behaviour could not be explained by purely Newtonian physics.

      Modern work on the actual speed of gravity is pretty arcane. Current theories suggest that it isn't any faster than the speed of light, but the related papers are well beyond my ability to understand. Good luck ;-)

      (also, "The force you impart to the rod propagates through the entire rod much faster than light speed"... really? if that were true, we wouldn't be arguing about the existence of superluminal physics still!)

    3. dlc.usa

      Re: Gravity Propagation Question

      [blush] Kindly substitute "force" for "light" in the foregoing post.

  9. steve13565
    Happy

    Special Theory of Relativity

    I thought that it was the special theory of relativity that posed the restriction on traveling faster than light. Maybe the general theory also sets the speed of light as a restriction.

    Sitting here in the U.S., I find the use of the term "boffin" to be hilarious.

    1. This post has been deleted by its author

    2. OrsonX
      Happy

      @Boffin Steve

      Sitting here in the UK I find the (not mentioned in article) USS Ponce to be a funny name, especially far a warship!

      What does Boffin mean in the US?

  10. Anonymous Coward
    Anonymous Coward

    Us2them

    Why should we ever contact or do something more insane give a insane killer a gun and a car to roam the neighborhood. Man is a dangerous violent animal. So violent that we will never give him the knowable or tools to get him off his planet Earth. He will for all eternity be lockup on planet Earth

    1. Fred 4

      Re: Us2them

      probably for the best.....

    2. fung0

      Re: Us2them

      First, while Man is obviously dangerous to Man, it is the height of hubris to think the Universe is losing sleep over our popguns and petty bickering. Second, Man is no more violent than, say, bacteria. Or my cats, which fight constantly, for no apparent reason. Third, eternity is a very long time, and there is a great deal we still do not know.

  11. Irongut

    The Forever War

    Great book. All fans of SciFi or war fiction should read it.

  12. sageev

    Quantum, eh?

    Oh well, collapsars are out. Infinite Improbability Drive is it, then. Tea any one?

    1. fung0

      Re: Quantum, eh?

      As far as I can see, the findings presented in the article simply show an unrelated confirmation of Relativity, rather than a specific refutation of the possibility of Collapsar travel. Moreover, there remains a great deal we do not understand - such as why 95% of the Universe remains unaccounted-for, or why Relativity and Quantum Mechanics can't be reconciled. For starters. Milk and sugar in mine, thanks.

  13. The last doughnut
    Thumb Up

    Since this is ask-a-stoopid-question-Friday

    The gravitational force generated by a spherical (or any shaped) body is maximum at its surface, right? So when we have a neutron-star accreting material from a companion, as the mass builds to that necessary to form a black hole. The black hole will actually form at some point on the _surface_ of the neutron-star, right?

    And I also liked The Forever War.

    1. Midnight

      Re: Since this is ask-a-stoopid-question-Friday

      The pressure is still greatest at the core. That 's why the middle part of the sun is where all the burning happens.

    2. Ken Hagan Gold badge

      Re: Since this is ask-a-stoopid-question-Friday

      "The black hole will actually form at some point on the _surface_ of the neutron-star, right?"

      I would imagine that's right, as long as you substitute "event horizon" for "black hole".

  14. Bill Gould

    Scientists respond with "I dunno"

    Give it a few years and they'll change their mind and start using new theories.

  15. Stevie

    Um...

    When Haldeman wrote The Forever War the term "collapsar" was what they were using for what we now routinely call a Black Hole. I remember Patrick Moore giving a presentation on this then-new postulated phenomenon on The Sky at Night.

    Now if you want a good story about neutron stars, Larry Niven is your man, though his classic "Neutron Star" cannot work as written for reasons Niven goes into in Known Space (I think) and which I won't spoil because it is still a rip-roaring adventure that takes classic hard SF into the world of 70s cutting edge astrophysics. Niven's star drive in that universe is more entertaining too.

    I recommend Forever War to everyone as a classic of rational hard SF and also as an answer to the then not-so distant Starship Troopers. If you want to know why, read Troopers first, then TFW.

  16. Schultz
    Thumb Up

    Collapsar travel...

    is more of a metaphysical thing, you enter in bodily form and you separate into a beautiful smear of photons --liberated from the blob of matter below.

  17. Anonymous Coward
    Anonymous Coward

    "which means that journeys between the stars must take years or centuries at minimum"

    As measured by whom?

    1. Thecowking

      Nearest star is 4 Ly away, travelling at accelerations humans can stand, years is definitely the minimum. Leaving aside the energy costs, it'd take nearly a year to hit C, so you'd have travelled about .5 LY in the first year.

      Lorentz dilation doesn't take it down much in the velocity changing phase given that for a long chunk of speeding up and slowing down you'd be experiencing only minor dilation.

      Of course at lightspeed (if such a thing were possible) you wouldn't experience time, but the two subjective years of speeding up and slowing down would be longer than a year my back of the envelope maths tells me.

      Of course the bonus about accelerating to lightspeed and then travelling at it is that all journeys would,subjectively, take exactly the same time.

      In reality of course the energy requirements get sufficiently onerous as you get faster that constant acceleration is a non-starter.

      1. Thecowking

        I did of course mean the closest star that wasn't the sun.

        Reaching the Sun in less than a year is definitely possible.

  18. Anonymous Coward
    Anonymous Coward

    Any explanation of WHY we thought this might work?

    Was it reasonable to expect that relativity might have been circumvented by such a large mass?

    Seems a bit like thinking I might get to my destinations infinitely fast if I was driving the biggest possible SUV.

    1. This post has been deleted by its author

  19. AmericanGuy
    Pint

    Anything is still possible

    The last sentence of the article was a classic "out" that seemed to invalidate the article content, or at least say "take this with a grain of salt." Einstein knew in physics that all bets are off. The universe is supposed to behave like this or that, at least in our region or "plane" (for lack of a better word) of space. Leave that region or "plane" and the rules of the party change.

    Cheerio!

    1. Michael Wojcik Silver badge

      Re: Anything is still possible

      Feel free to adopt that motto if it makes you happy, but it's no consequentially different from simple subjective solipsism - believing that nothing outside the conscious self can be known. Of course in that case anything is always possible; all of your perceptions could be hallucinations.

      But there's little point in taking solipsism as a substantive foundation - of trying to act based on it. And there's equally little point in trying to act on the belief that physics is different in parts of the universe we can perceive. Maybe so, but so what?

      Formal and empirical results that challenge our models are interesting, because they suggest there's something new to know, and perhaps to do. Theories that challenge our models are sometimes interesting, because investigating them might lead to new formal or empirical results. Saying "maybe our models don't hold under some conditions that we have no empirical access to, and no formal mechanisms to describe" is chit-chat.

  20. Anonymous Coward
    Alien

    So much for my hopes of making the Kessel run in less than 12 parsecs!

    What am I going to have to do to defeat Captain Solo? Encase him in carbonite or something??!!

  21. sisk

    Meh

    It's not as though the idea of a collapsar jump would be particularly useful even if it did work. Our distant descendants on a generational ship might be able to use one, but by the time they got there, assuming they were to leave right now, we'd have already colonized a couple of nearby solar systems.

    Personally I'm still hoping for some brilliant physicist to come up with a practical way to make an Alcubierre drive. Of course they have to wait for some other physicist co come up with a way to harness exotic matter....and that physicist will have to wait till someone figures out how to produce exotic matter in significant quantities....which of course will have to wait till someone actually proves that the stuff exists....I'll stop now. My hopes of visiting Polaris in my lifetime are getting further away.

    1. This post has been deleted by its author

  22. jmmwill
    Thumb Up

    Einstein's Limit and Time Travel

    There never has been any evidence of violation of Einstein's limit.

    One reason is that it would imply violation of conservation laws. A nontechnical discussion related to this may be found at http://www.scribd.com/doc/35613144/Time-Travel

    A slightly technical discussion is at http://www.scribd.com/doc/38202981/A-Simple-Proof-that-the-Speed-of-Light-is-the-Greatest-Possible

    1. Tom 7

      Re: Einstein's Limit and Time Travel

      You cant measure anything faster than your measuring stick.

      1. Muscleguy
        Boffin

        Re: Einstein's Limit and Time Travel

        "You cant measure anything faster than your measuring stick."

        So I can't measure any distance longer than my longest measuring stick? Except with Pythagoras's theorem I can measure any distance I like starting from wherever I like.

        Seeing something move across the horizon is a matter of the number of degrees or arc seconds it transects per unit time. So, if you have a measuring stick of the size of a say a galaxy you have got to with triangulation you can sit and watch for things crossing that horizon at any given speed. Even light takes long enough to cross at galaxy scales that anything travelling that fast would be easily viewable and measurable, if of course it were reflecting or generating light. There are some stars orbiting the monster black hole at the centre of the galaxy and also on strange trajectories out of and around the galaxy that have been measured travelling at appreciable fractions of the speed of light.

        At the other scale if you magnify your view slugs and snails become speedy as they transect the horizon quickly. Things moving under Brownian motion are quite speedy looking once you magnify them enough but their absolute speed is very slow. It's all relative you see. To observe fast moving things move back a long way, to observe slow moving things move much closer.

        1. This post has been deleted by its author

          1. Pascal Monett Silver badge

            Please continue.

            Your posts are among the most informative and interesting of this site. If you stop, it will be much harder to actually learn something here.

            1. This post has been deleted by its author

  23. DF118
    Alien

    Forever War

    So... Ridley Scott apparently won the film rights a few years ago, after decades of trying. Anyone care to hazard a guess as to whether he'll get to make it in his lifetime?

  24. Destroy All Monsters Silver badge
    WTF?

    Jesus F. Christ EL REG FAIL

    A "collapsar" is not a neutron star. Indeed it is a historical name for a black hole. It's one of those historically old-fashioned words. Collapsar because "it collapses in....forever"

    1. Destroy All Monsters Silver badge
      Flame

      Re: Jesus F. Christ EL REG FAIL

      Yeah, I fart in your general direction, downvoter! Are you some kind of liberal? A kumbaya-singing peter puffer? Do you not only believe that man's mind and the laws of nature can be bent to your irrelevant puny laws, regulations, Glass-Steagal acts and other retarded mental contortions, but will you not even stop at science and scientific definitions until the only legally allowed thesaurus conforms to your own personal idea of Goodthink and Correctspeak? I'm sure your postmodernism makes you hope that all which you consider ungood can be banned and be disappeared with just a bit of rewriting. HAH!

  25. FuzzyTheBear
    Pint

    The brighter side of life ..

    That also keeps the aliens from coming to earth groceries shopping for tasty humans ..

    When i think about the relativistic prison under that angle .. i kind of thank Albert :)

    Cheers Albert

    1. Muscleguy
      Thumb Up

      Re: The brighter side of life ..

      Don't worry, we have The Boys to protect us from human eating aliens.

  26. rictay

    re- Stupid question

    No it's not a stupid question, but a perfectly valid thought experiment. So don't be Anonymous, stand up proud and thoughtful!

    Even if the rod was perfectly rigid, you would need a device at the far end of the rod to tell you that the rod had moved. That information coming back to you could only propagate at the speed of light. I'm guessing that your initial push would propagate at the speed of light because you are passing information to the sensing device at the far end.

  27. Paul Hovnanian Silver badge
    Unhappy

    No interstellar travel?

    [Sigh] I guess I'll have to change my holiday plans and book a hotel room in Maui again.

  28. Destroy All Monsters Silver badge
    Trollface

    Excessive churning tests the boundary between El Reg and Science! Film at 11.

    It's rather perplexing how quantum mechanics would come into this.

    On whould think this were a test of GR vs other theories of gravity, like MOND or TeVeS, as described in

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

    One would not expect QM to come into this, like, at all. So, one starts off with space.com:

    http://www.space.com/20826-einstein-gravity-theory-toughest-test.html

    which gets it right. Then one passes over to livescience, which refers to the above:

    http://www.livescience.com/29062-einstein-relativity-tested-again.html

    ... but the churner adds in QM for no good reason, probably because he doesn't quite grasp what's up.

    El Reg doesn't link to livescience but I guess just saw the above, then threw in the wrongly used "collapsar" and from there wanders off to Haldeman and manfrommars territory.

    So what's important about this? This is:

    "Our results indicate that the filtering techniques planned for these advanced instruments (of gravitational wave detection) remain valid," said Ryan Lynch, a physicist at McGill University in Montreal.

    Everything else is manure. Are YOU running einstein@home on your Tesla card?

  29. solaries
    Alien

    Curse You Einstein

    I wouldn't be so sure try Thomas Townsend Brown and John Serle. And there are articles on the io9 website dated Nov.26,2012 titled How NASA Might Build it's very first Warpdrive and one dated Jan.04,2013 titled The Woodward Effect allows for endless supplies of Starship Fuel.

  30. Steve Martins
    Joke

    The point is...

    I had a point to make, but as soon as I evaluated it, it changed...

  31. This post has been deleted by its author

  32. Tinker Tailor Soldier

    Remember time slows down...

    Ignoring energy required (engineering problem solvable at some scale) and getting blasted to bits by high frequency photons (bit harder, but a bunch of ions helps). You can get anywhere you want because time slows down as you approach the speed of light. To an external observer you turn into a blue shifted or red shifted strangely shaped thing, that still can't get anywhere faster than light.

    So long as you aren't trying to build an empire and run it, this is all OK.

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