Warp Drives

“Warp drives” originated in the science fiction shows “Star Trek” in the 1960s, but in 1994, the Mexican Miguel Alcubierre published a paper arguing that under certain conditions exceeding light speed was not forbidden by Einstein’s General Relativity. Alcubierre reached his solution by assuming it was possible, then working backwards to see what was required while rejecting those awkward points that arose. The concept is that the ship sits in a bubble, and spacetime in front of the ship is contracted, while that behind the ship is expanded. In terms of geometry, that means the distance to your destination has got smaller, while the distance from where you started gets longer, i.e. you moved relative to the starting point and the destination. One of the oddities of being in such a bubble is you would not sense you are moving. There would be no accelerating forces because technically you are not moving; it is the space around you that is moving. Captain Kirk on the enterprise is not squashed to a film by the acceleration! Since then there have been a number of proposals. General relativity is a gold mine for academics wanting to publish papers because it is so difficult mathematically.

There is one small drawback to these proposals: you need negative energy. Now we run into definitions, and before you point out the gravitational field has negative energy it is generated by positive mass, and it contracts the distance between you and target, i.e. you fall towards it. If you like, that can be at the front of your drive. The real problem is at the other end – you need the repulsive field that sends you further from where you started, and if you think gravitationally, the opposite field, presumably generated from negative mass.

One objection often heard to negative energy is if quantum field theory were correct, the vacuum would collapse to negative energy, which would lead to the Universe collapsing on itself. My view is, not necessarily. The negative potential energy of the gravitational field causes mass to collapse onto itself, and while we do get black holes in accord with this, the Universe is actually expanding. Since quantum field theory assumes a vacuum energy density, calculations of the relativistic gravitational field arising from this are in error by ten multiplied by itself 120 times, so just maybe it is not a good guideline here. It predicts the Universe has long since collapsed, but here we are.

The only repulsive stuff we think might be there is dark energy, but we have no idea how to lay hands on it, let alone package it, or even if it exists. However, all may not be lost. I recently saw an article in Physics World that stated that a physicist, Erik Lentz, had claimed there was no need for negative energy. The concept is that energy could be capable of arranging the structure of space-time as a soliton. (A soliton is a wave packet that travels more like a bubble, it does not disperse or spread out, but otherwise behaves like a wave.) There is a minor problem. You may have heard that the biggest problem with rockets is the mass of fuel they have to carry before you get started. Well, don’t book a space flight yet. As Lentz has calculated it, a 100 m radius spacecraft would require the energy equivalent to hundreds of times the mass of Jupiter.

There will be other problems. It is one thing to have opposite energy densities on different sides of your bubble. You still have to convert those to motion and go exactly in the direction you wish. If you cannot steer as you go, or worse, you don’t even know for sure exactly where you are and the target is, is there a point? Finally, in my science fiction novels I have steered away from warp drives. The only times my characters went interstellar distances I limited myself to a little under light speed. Some say that lacks imagination, but stop and think. You set out to do something, but suppose where you are going will have aged 300 years before you get there. Come back, and your then associates have been dead for 600 years. That raises some very awkward problems that make a story different from the usual “space westerns”.

4 thoughts on “Warp Drives

    • My effort on this starts like this:
      “Pallas Athene was in disgrace, but she felt that it was worth every gram of it for she had immortalized herself, starting over three thousand years before she was born. Yes, she knew that her career as a serious classical historian was over, and being consigned to this miserable cell was not exactly a career highlight…”

      and continues shortly after like this:
      “What was known only to a handful of classical scholars was that there was an obscure tale of the Trojan War and somebody called Achilles, apparently told by, of all things, a blind poet of no significance. This was followed by what could be called a sequel, and this was a miserable tale of a drunkard who spent ten years fornicating around Greece before he returned home. When he did return, he thought his wife was taking lovers, so, after getting suitably drunk and unsuitably angry, in a quite messy and deplorable scene he bludgeoned the unfortunate wooers to death. This was followed by a sequence of squalid revenge bludgeonings. The original splatter tale!
      She, Pallas Athene, had realized that information had neither inertial mass nor entropy, and accordingly, under certain conditions it was possible to be more active. The key was, a human’s brain was always active, even when it was not doing anything significant, hence information could be transmitted there, redirecting electrical activity that was happening anyway without violating the laws of physics. If an historical person happened to be inside a certain configuration of stones or partially surrounded by another material of sufficiently high impedance, she could generate a direct communication with the subject’s brain, particularly if the person was asleep or deeply relaxed. She could give seers prophecies, which were harmless because nobody believed them until they came true. She had ruined Kassandra’s life, but later efforts were more fruitful. The Delphic Oracle was in an ideal site, and one particularly fruitful effort had been to give the oracle Galba’s age, which greatly enhanced the mystique of the prophecy relating to Nero. She had drafted a short paper outlining how to do it, and she had intended to send this out for peer review shortly. She would be famous!
      However, the highlight occurred in the temple in which the blind poet spent a lot of time. She, Pallas Athene, gave him visions that would improve the stories, and at the same time she inserted her name, as a Goddess.
      Once Homer realized he could get visions in the temple, he came often. For a blind man, vision was a gift from the Gods. She had shown him what Ithaca, Troy, and the Plains of Illios actually looked like, she could show him the battles, and more to the point, she greatly improved the second story. A squalid drunken hypocrite who killed to escape the consequences of his fornicating was not the stuff of legends; make him truly a man of wrath. With the aid of special graphics she could show him monsters and places he could never imagine to better account for why the hero was away so long, and she could show the bloody ending that a true man of wrath would impose.
      There had been a problem: the Gods had only one name. Why had she called herself Pallas Athene? Yes, it was her name but that was insufficient so she had to concoct this story about her having devoured Pallas, which made her a twin Goddess, but of what? The ferocity made warfare obvious, but the second? When the image of an irate Dr Chu came to mind, she had said science, then added wisdom as an explanation. The blind poet was impressed and made her part of the tale. Then, to make certain of her immortality, she had recorded the colour of her eyes. Who had ever heard of a grey-eyed Greek of that period? Athene had thought that this was truly safe because the change was noticeable only to those in the temporal satellite at the time and who had heard of the original versions; she was currently the only classical scholar on board.
      The effect was startling. With such inspiration Homer completely changed his stories, and where before they had been eminently forgettable, and only recorded much later by sheer accident and then largely ignored except by half a dozen scholars, suddenly history had two pieces of truly great literature. The problem was, those within the temporal satellite retained their old memories but could view the changed scenario, and because of the greatness of the stories her prank had been uncovered. The sudden change in the name of the capital of Greece was also a bit of a give-away.

  1. I understand complex numbers from physics (polarization of light gives the square root of minus one). I don’t understand negative energy (as it is Force multiplied by Distance; OK, Force can be negative, but that’s just convention). Or, let me be clearer, if negative energy appears it will disappear as the Dirac electron sea with its holes… Or as any potential energy in basic physics.

    In the LCDM (“Big Bang”) model, cosmic inflation (CI) goes at a torid 10^23 C or so…

    So LCDM claims that there is warp speed, the speed of space. LCDM does that to look consistent with observations… So it is a backward way to recognize the existence of warp speed…

    Now General Relativity is a near-tautology, given local classical theory of gravitation (attributed erroneously only to Newton). But CI is “exterior” so to speak. This reflects the situation from the embedding theorems: the spacetime manifold is embeddable in high dimensional flat space (in a number of ways). This brings the question of what space is made of.

    I don’t believe in internal ways of going faster than light… Short of using FTL Quantum Entanglement (which you like very much)… Now FTL QE may be what space is made of… This is what I believe. Dark Energy is actually simply the leakage of gravitation over billions of light years according to the non-instantaneous collapse theory (SQPR). Given a cosmic expansion, it will accelerate if gravitation weakens… Positive energy saved!

    • Negative energy comes in two forms. One is “obvious”, namely gravitational potential energy, but that is because of our definition that the gravitational interaction energy of two objects at infinity is zero. Because they fall towards each other, the new energy must be negative, but kinetic energy must be positive, so potential energy becomes more negative to satisfy the virial theorem.

      However, what we are talking about here is the is the energy from mc^2. For that to be negative, we need negative mass, and we would get antigravity. So far, all we know about mass is it is monopolar. In this sense, positive energy was never in doubt. Essentially how this drive works is you have an effective gravitational attraction at the front so you fall towards your target and an antigravity at the rear, you you push away from everything behind you. I have no idea what happens if spacetime is simply a mathematical construct, which I think it is, because in these theories so far the spacetime has to be severely stressed.

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