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Gravity Manipulation

  1. Feb 22, 2005 #1
    This topic is a little "out there" but what are you thoughts on this being possible someday? I'm doing some research for my Hard SF world and don't want to use anything unplausible. If possible any guesses as to if it'd only need power to turn it on, off and change altitude, not to maintain levitation at the desired altitude? What physical mechanism would allow repulsion against gravitational fields? Could gravity be manipulated not only in the negative but create positive gravity "lasers" to tear objects apart or just pull them to you like sci-fi "tractor beams"?

    Thanks for the help if you can.
     
  2. jcsd
  3. Feb 22, 2005 #2

    pervect

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    I think that gravitry manipulation (artifical gravity ala Star Trek, inertial dampers that allow large acceleration, tractor beams, pressor beams, etc etc etc) is really not plausible. This has not stopped some reasonably good science fiction from being written. I'd suggest concentrating on the story, and not worrying about the fact that the idea isn't really very plausible scientifically.

    There are a few plausible ideas that could be called gravity manipulation written by hard-sf authors, though. If one had hyper-dense materials, one could create regions of zero-gravity on earth by utiliizing the gravity field of a disk of such a hyper-dense material. By hyper-dense, I'm talking about electron degenerate matter. Now, I don't personally think it's very likely that we will be able to create and stabalize electron degenerate matter, but it's on the bare side of physical possibility. Robert Forward is the author of this (see his collection "Indistinguishable from Magic", or the short story "The Singing Diamond"). I think Forward has some other semi-plausible ideas ideas in the area as well, but I don't recall the details any longer.

    Gravity also plays an important role in Stephen Baxter's "Xeelee" series of stories. Here gravity manipulaiton is necessary, because the Xelee are fighting foes basically made out of "dark matter", and gravity is the only thing that will affect them. IIRC, the "dark matter" entities win in the end - they constitute the vast majority of the universe, so it was almost a forgone conclusion. Baxter wisely does not attempt to give any details of the Xeelee's gravity manipulation technology, it is simply presented as ultra-high level technology.
     
  4. Feb 22, 2005 #3
    Well, looking at you question, I have to ask how much do you know abut gravity. Gravity is the bending of space time. Most Scientists believe that gravity travels as a wave. A disturbance in this space time would cause a ripple in the very fabric causing a gravity wave. The only idea that I would suggest is a mechanism that would explode with such great force that it would cause a large enough gravity wave to stretch out an object. But, considering that a supernova occurring in our galaxy causes a strain of 10^-20m, then it is most likely that a weapon designed to harm somebody would be just an expensive toy. To answer your question, there is no current mechanicsm that opposes gravity that could possibly make you levitate.

    Regards,

    Nenad
     
  5. Feb 22, 2005 #4

    arildno

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    You ought to keep in mind that a scientifically sound, but "wild" idea will usually not be a literary "cool" idea.
     
  6. Feb 22, 2005 #5

    GENIERE

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    With a constant acceleration of 1G a spacecraft would need no artificial gravity. Interstellar voyages to nearby stars would take a reasonable period of time and when the halfway point is reached just thrust in the opposite direction. I’ve given the answer; someone else will have to provide the power source. :biggrin:
     
  7. Feb 22, 2005 #6
    GENIERE, you put up a good idea for interstellar travel but I dont see how it would do anything to cause a grevitational shift or wave being produced.
     
  8. Feb 22, 2005 #7
    You can make as gravity as strong as you want (up to and including infinite) but gravity can never be repulsive (no anti-gravity, it would have to be something else pulling you).

    See, energy of any form counts as mass as far as gravity is concerned. Therefore an imaginary ultra laser would create gravitational fields whether you wanted it to or not.
     
  9. Feb 22, 2005 #8

    Gravity can't be repulsive but what about something else? I seem to remember reading about the universe having some kind of force acting against the gravity in the universe. Something about it expanding faster and faster when it should only be going at a constant rate or slowing down. Anti-gravity just means against gravity. Anything that flies is anti-gravity. I'm aware of Einsteinian gravity being caused by a mass warping space-time into a dimple, like a ball of steel being placed on a membrane of thin rubber. Roll another steel ballbearing around inside this "gravity well" and it orbits the center ball. Does the same thing hold true if gravity is caused by graviton particles(or closed strings if Brane Hypothesis is correct)?
     
  10. Feb 23, 2005 #9
    No, the same thing would not hold true if gravitons were discovered. General Relativity describes gravity as the process you described above. While on the opposite end of the spectrum, quantum mechanics chooses to describe gravity as an interaction of gravitons. The graviton is a particle, while general relativity describes gravity as a wave interaction, hence the name 'gravity wave'.

    Now string theory or super strings are what unites general relativity and quantum mechanics. It is still to be proven but it could be a solution to today’s gravity explanation problems.

    Regards,

    Nenad
     
  11. Feb 23, 2005 #10

    LURCH

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    This is not necessarily true. Under certain conditions an exotic form of energy known as "negative energy" can be created. (I should add that negative energy has never been directly observed, and may be impossible to observe directly.) Creating these conditions in the lab, physicists have observed a phenomenon which matches the predicted properties of negative energy. By these same models, negative energy is predicted to be gravitationally repulsive. This property has never been observed, due to the extreme difficulty in detecting the gravitational influence of very small amounts of mass. However, since the observed properties so closely match those predicted by the mathematical model, it is reasonable to believe that this prediction is also accurate.
     
  12. Feb 23, 2005 #11

    GENIERE

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    Actually reading the article (link follows) and previous related articles has convinced me that ZPF may lead to the long sought field unification. If true, gravity may be a manifestation of EM. As such it may indeed be possible to create anti-gravity devices. Also fascinating is the cause of inertia, and the reason electrons, quarks… acquire mass.

    The worrisome part is that I can almost understand it, dooming it to failure.

    The article is in the California Institute for Physics and Astrophysics archives. Follow this link:

    http://www.arxiv.org/abs/gr-qc/0209016


    I believe Lurch is referring to ZPF in his post. If so, that force does exist and has been measured, originally by Lamb who demonstrated an energy shift in the hydrogen electron and later by several investigators of the Casimir effect.
     
  13. Mar 1, 2005 #12

    Very interesting. This is sort of the problem, we don't know the universe completely. Kind of hard to base a hard SF on something that could easily be wrong. It will date fast. So lets say ZPF turned out to fit the universe nicely. Does its anti gravity need energy input to maintain it or just to turn it on, off and change levitation height? Another thing. It wouldn't have an altitude limit like you see in say Star Wars where the landspeeders can't fly more than a few meters above the ground? In other words one could get to orbit for really really cheap on energy, among other things?
     
  14. Mar 1, 2005 #13

    ZapperZ

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    I need to temper the "raging fire" a little bit here. I know this is all about coming up with some plausible scenario for a Si-Fi story, but let's not lose grip on reality completely here, folks.

    The paper that is being cited from the e-print arxiv is based entirely on a paper published by Puthoff and company. Now I don't know about any of you, but Puthoff's ideas are not actually accepted or even uncontroversial, to say the least. Some of the stuff he's saying, if true, would mean that the universe must be OPAQUE. That's how much energy he's claiming he can extract out of the vacuum!

    I suggest reading a few dessenting voices to this to balance out the perspective here. I do not want anyone not familiar with this particular field of study to go away thinking everything is fine and dandy. They are not!

    http://www.aps.org/WN/WN94/wn031194.cfm
    http://www.aps.org/WN/WN02/wn081602.cfm
    http://www.aps.org/WN/WN02/wn080202.cfm

    Zz.
     
  15. Mar 1, 2005 #14

    From you're links that man is a nut. Uri Geller, Mercury "mind flight", oh man.......
     
  16. Mar 1, 2005 #15
    So who is this Lamb guy and the people who studied the Casimir Effect? Just because the Puthoff guy is crazy doesn't mean everything he based his hypothesis on is bunk.
    If gravitation is caused by gravitons(either particles, closed strings...whatever) does this open the door to possible anti grav unlike say with Einsteinian gravitation?
     
  17. Mar 1, 2005 #16

    ZapperZ

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    The Lamb shift and the Casimir effect are NOT "bunk". None of the links I gave indicated that, and none of what I said even remotely infer that.

    But as a bumper sticker that I once read said "Dear God, please save me from your believers", it is the people who took these phenomena and decided to make wild extrapolations to it.

    Look, there is a very obvious test for you to check for yourself to know if so-and-so claim is valid - find CONSISTENT and REPRODUCIBLE experimental evidence in peer-reviewed journals. It is THAT simple! And if we apply this test, you'll automatically realize why you should not build any kind of understanding that depends on the existence of "gravitons".

    Zz.
     
  18. Mar 3, 2005 #17
    For creating AntiGravity U need to look at the repulsive forces that exist in nature. One is Magnetic North North pole repulsion, Can U guess the other one ?

    I will tell U only if U insist.
     
  19. Mar 5, 2005 #18

    Mk

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    Of course the theoretical "exotic matter," not just an exotic matter, but the exotic matter, is like negative mass, and repels normal matter. So to say, a hill on the fabric of space time-rubber sheet analogy.
     
  20. Mar 6, 2005 #19
    If antigravity did exist, would it violate the conservation of energy?
     
  21. Mar 9, 2005 #20

    You don't have to get rough and bite my head off. Yes or no, am I remembering correctly about the universe expanding faster and faster. If I'm remembering correctly they said something like negative energy(whatever this is) could be the cause. Sorry I can't remember the magazine. It was Scientific American, Popular Science, something like that..... If negative energy fights against gravity it stands to reason maybe anti-gravity could work.
     
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