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Solar System in a Can May Reveal Hidden Dimensions

Posted by Zonk on Fri Jul 07, 2006 06:45 PM
from the you-can-get-them-in-cans dept.
Space Science
dylanduck writes "A model solar system, made of tungsten and placed in space, could reveal hidden spatial dimensions and test alternative theories of gravity. If the system's 'planets' moved slightly differently to the way predicted by standard gravity, it would signal the presence of new physical phenomena." From the article: "Once at the Lagrange point, the artificial solar system would be set in motion inside the spacecraft. An 8-centimetre-wide sphere of tungsten would act as an artificial sun, while a smaller test sphere would be launched 10 cm away into an oval-shaped orbit. The miniscule planet would orbit its tungsten sun 3,000 times per year."
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  • Gotchas, we got em (Score:3, Interesting)

    by Ancient_Hacker (751168) on Friday July 07 2006, @06:53PM (#15680395)
    This sounds mighty dubious. The gravitational attaction of the spacecraft is likely to be much larger than the effect looked for.

    • Re:Gotchas, we got em (Score:4, Informative)

      by d34thm0nk3y (653414) on Friday July 07 2006, @07:00PM (#15680425)
      FTA:
      And the spacecraft components themselves would exert gravitational forces on the spheres. These forces could be minimised by making the spacecraft as symmetrical as possible and putting its heaviest components as far from the artificial solar system as possible.

      "Such an experiment would be quite challenging to set up, but I don't think it is technologically impossible," says MOND expert Stacy McGaugh of the University of Maryland, US.

      Not impossible can be quite a stretch to feasible, though.

    • Re:Gotchas, we got em (Score:5, Funny)

      by pilgrim23 (716938) on Friday July 07 2006, @07:04PM (#15680442)
      the old L5 Society wanted to place a module they called a High Orbital Mini-Earth there... sort of a H.O.M.E. on LaGrannge.....

      • Home on LaGrange (Score:3, Funny)

        by Anonymous Coward

        Oh, give me a locus where the gravitons focus
        Where the three-body problem is solved,
        Where the microwaves play down at three degrees K,
        And the cold virus never evolved.

        Home, home on LaGrange,
        Where the space debris always collects,
        We possess, so it seems, two of Man's greatest dreams:
        Solar power and zero-gee sex.

        We eat algea pie, our vacuum is high,
        Our ball bearings are perfectly round.
        Our horizon is curved, our warheads are MIRVed,
        And a kilogram weighs half

    • Re:Gotchas, we got em (Score:5, Insightful)

      by ceoyoyo (59147) on Friday July 07 2006, @07:11PM (#15680476)
      They mentioned that would have to be taken into account. Scientists measure the gravitation attraction between human scaled objects on Earth all the time, yet that's dwarfed by Earth's gravity.
    • Since it's not explicitly stated in the article or these replies, gravitational effects precisely cancel inside a uniform shell. So if the spacecraft's mass was evenly distributed on a spherical shell there would be zero effect on items inside the shell, even when those items are close to the shell's interior surface.

      Of course, the math for that is based on regular-old physics. It might not apply in higher-dimensional physics that these scientist hope to prove.

      Of course, the article ignores the difficulty i
      • >Since it's not explicitly stated in the article or these replies, gravitational effects precisely cancel inside a uniform shell. So if the spacecraft's mass was evenly distributed on a spherical shell there would be zero effect on items inside the shell, even when those items are close to the shell's interior surface.

        Um, I don't think so.

        The effects cancel very nicely at the exact center, and nowhere else. As you get off-center, the attraction of the nearest wall exceeds the attraction of the oppo

    • Re:Gotchas, we got em (Score:4, Informative)

      by Rob Carr (780861) on Friday July 07 2006, @08:02PM (#15680727) Homepage Journal
      In Freshman physics, it's common to demonstrate the net gravitational or electrical attraction inside a uniform sphere is zero. Any force with an inverse-square law will exhibit this peculiarity. If you want the details, there's a Wiki article on the Divergence theorem of vector fields.

      The proof, involving triple integrals, is left for the reader.

      Of course, designing a spacecraft that is as spherically symmetrical and uniform in density as possible will be difficult. TFA refers to this, and before much money is spent on this project, one would hope some number-crunching is done to see how extreme the effect is.

      Another problem will be microgravity. Orbital velocity is dependent upon the distance from the center of the object being orbited. In Earth orbit, even a few inches difference can produce a velocity gradient that can result in minute accelerations. At L2, some of these effects might be minimized, although again, number crunching should be done.

      The late Robert L. Forward proposed a system of massive spheres that could flatten spacetime in a local region [aps.org]. To further minimize extraneous effects due to microgravity, a system like this might need to be used. One advantage would be that this same system might eliminate some of the problems due to assymetry in the spacecraft. One of the problems with this situation would be mass lofted, which currently tends to be expensive, and additional calculations that might be required to analyze the data.

        • Re:Gotchas, we got em (Score:4, Informative)

          by Rob Carr (780861) on Saturday July 08 2006, @12:27AM (#15681622) Homepage Journal
          We demonstrated that forces that follow an inverse square law follow this rule. We demonstrated that a charged sphere followed that rule in a lab by charging the sphere and then measuring the electrical force inside the sphere and out. We demonstrated that electrical forces follow the inverse square law in the lab. I'd argue that stable orbits demonstrate inverse square law for gravity, and we did visit the telescope and look at the moon in Freshman physics. We also calculated G using the old torsion technique.

          Calculating the position of the moon throughout the month and deriving the orbit wasn't something I did until I got out of college. It's well within the capability of a Freshman physics student, so in theory we could have confirmed the inverse square law to a decent level of precision.

          Tightening the exact value of that exponent (is it really -2?) further is the purpose of the proposed experiment.

          If you know that gravity follows an inverse square law, then you know that inside a uniform sphere the gravitational acceleration will be zero.

          You are correct. We never demonstrated experimentally for gravity that the net gravitational force inside a sphere was zero. Of course, I never said we did. The term "demonstrate" can, in fact, be used in a mathematical sense. When one of the kids on our dorm floor claimed the Ringworld was unstable, we had no trouble demonstrating that instability -- not that anyone had a Ringworld to work with.

  • If the minature solar system is sent into space, then would it also come under the effect of the gravity of the actual solar system? Granted the effect will be very small (considering one object is very small and is far away anyway) but surely it would cause enough of an effect to make a difference? I'm sure they're trying their best to cancel out these forces, but they'd need absolutely minute amounts of gravity or (impossibly enough) none at all for a good reading.
    • If the minature solar system is sent into space, then would it also come under the effect of the gravity of the actual solar system?

      Lagrangian Point [wikipedia.org]
      • even the lagrangian point feels miniscule effects from other planets...

        it's lagrangian for the earth/moon system... not for the rest of the planets...

        with that force, and with the gravity from the spacecraft, how can any measurements be useful enough (i.e. free from otside noise) to show anything useful? one ide.... maybe they will model everything (spacecraft, and solarsystem) in a computer and compare to what really happens in the experiment. Even so... wont there be thermal considerations that eve
    • Despite the misleading title they're not trying to make a model solar system. They want to put one metal sphere in orbit around another one and then watch to see if its orbit precesses the way they predict.
  • You would need to be extremely precise for that to work. The masses of the model planets would have to be PERFECTLY scaled. Do we actually know for a fact the masses of all the other planets, and can we make something that precise?

    Then you have to consider the gravitational effect of the asteroid belt. Do we know the mass of that, too? That might affect the model when put in use.

    Any conclusions made from this experiment would be debated over endlessly because of this...
    • "The masses of the model planets would have to be PERFECTLY scaled."

      Yeah, if they were trying to do a model of our solar system.
    • The masses of the model planets would have to be PERFECTLY scaled
      I'd love to know what is going through your mind at this point. Are you imagining these experimenters are planning to place nine little spheres in position around one big one and that we're going to see them orbit because of the gravitational forces between these spheres?

  • What if (Score:5, Funny)

    by Raindance (680694) <johnsonmxNO@SPAMgmail.com> on Friday July 07 2006, @06:57PM (#15680411) Homepage Journal
    I wonder if our universe is just a hidden spacial dimension test for a super-advanced alien civilization... still trying to figure out string theory.

  • Suspect this is rubbish - NS has been had? (Score:3, Insightful)

    by Toby The Economist (811138) on Friday July 07 2006, @06:58PM (#15680412)
    A tungsten sphere 10cm in diameter would have such a tiny gravitational field that I suspect even a hydrogen atom at the ambient temperature of local space would possess escape velocity.

    What exactly are they thinking of putting into orbit around this thing?

  • I got black text on a mostly black background. Sheesh! The printable page [newscientistspace.com] reads a lot better.

    Flyboy 8v)

  • Sounds like a fancy version of... (Score:3, Interesting)

    by exp(pi*sqrt(163)) (613870) on Friday July 07 2006, @07:18PM (#15680515) Journal
    ...Cavendish's [wikipedia.org] classic experiment. I look forward to seeing the results.
  • Boy, this puts the old RLC calculators to shame ...

    A link [wikipedia.org] for those too young to remember!

  • But can anyone explain to me why gravity would be the only force bleeding into other dimensions? Or is it the only one? Also is there any evidence of extra dimensions already? I would think there would already be some evidence since it does not sound very scientific to me to base the very popular string theory on imaginary notions with no basis in reality. If we are just gonna make up dimensions to make the math work isn't that just as bad as making up Thor to explain the thunder and lightning?
    • You have to understand that to a theoritician, having a "basis in reality" is a vague phrase. We have these equations, and they work really well for certain things that have been troubling the physics community for quite some time. They happen to require more than 4 dimensions. The theoretician says, "Oh well, find the other dimensions!" It's not a strange concept to make up new physics to "make the math work out". Quarks were hypothesized, then as each quark pair was discovered, we knew how many pairs of
  • Article states the orbit would be 1/3,000 degree in year.
    This is MUCH MUCH less than 3000 times in year
  • I don't like the word choice "hidden". Hidden is the past participle of hide.

    "hide"
    v. hid, (hd) hidden, (hdn) or hid hiding, hides
    v. tr.
    To prevent the disclosure or recognition of; conceal.

    This fairly clearly implies intelligent action. I.E. something did the hiding. I.E. the dimensions we can't see (if they exist) are purposefully invisible to us because something chose for them to be, something intelligent. Invisible, as another word choice, would've been better.

    Besides, something can't be hidden and

  • Simpson's... (Score:3, Funny)

    by grumling (94709) on Friday July 07 2006, @07:47PM (#15680662) Homepage
    "Well, we're running an experiment to see the effects of gravity on these little screws."

  • Some sanity here (Score:3, Insightful)

    by viking2000 (954894) on Friday July 07 2006, @08:29PM (#15680815)
    The key question is: What is the ratio between signal and noise here? The article does not mention this at all except talking about lagrange points, solar wind, etc. I assume placing it at L2 is to get the S/N ratio >1.

    This fails when considering some noise sources:
    1. Accelleration felt by a "grain sized planet" due to a 5kg ball 10cm away is 1m/s/year.
    2. Acceleration felt by same "planet" due to moon 1 million kilometers away: 130 times more
    3. Accelleration felt due to spaceship: ?
    4..? L2 orbit itself, light pressure, magnetic & other fields etc

    This appears unfeasable by orders of magnitude.

    I do not have much faith in statments like "Gravity leaks into other (higher) dimensions." Where does this come from? Efforts to make string theory models fit the real world?

  • interesting but (Score:5, Insightful)

    by rucs_hack (784150) on Friday July 07 2006, @08:52PM (#15680905)
    Since we're not able currently even to build a spaceship capable of making it to the moon (having mothballed all the relevent tech and gone for the technical nightmare that is the shuttle, and the hidiously expensive disaster that is the ISS), why bother with these types of experiments?

    Such experiments, while useful, aren't practical when we have a real and current need to figure out how to get construction workers and ordinary people into space, so we can build a realistic presence there.
    Once we're there, we could perform experiments like this at a fraction of the cost.

    Ok, perhaps I'm thinking too fancifully, but it's real concern. Let's face it, every environment we've moved into only becomes liveable when the ordinary people who know how to build stuff and make things arrive. The larger the number of people, the faster things progress.

    So long as it's only scientists and the 'elite' going into space and performing experiments progress will be very slow. That can't be good.

    What we need is people going 'prospecting' for interesting asteroids/orbiting 'junk' that can be exploited, building commercial stations, setting up routine flights into space. In short, we need economic forces active in space.

    • Since we're not able currently even to build a spaceship capable of making it to the moon [snip] why bother with these types of experiments?

      Yes, why play with twitching frog legs and your so called "electricity" when we have starving people and battling kingdoms to take care of?

      Funnily enough, fancy abstract "basic research" often has benefits that greatly outweigh the relatively small costs of setting up "these experiments".

  • Too many uncertainties (Score:4, Interesting)

    by mcguiver (898268) on Friday July 07 2006, @08:52PM (#15680908)
    It seems to me, after reading the article, that there are just too many influential factors to be able to conclude anything by such a test. From the article If gravity is leaking into extra dimensions, the slight change in its force should cause the planet's oval-shaped orbit to rotate, or precess, slowly... the orbit would precess by 1/3600 per year - "a reasonable quantity to try and measure," they say.
    I wonder how they could conclude that a change of this magnitude would come from gravity leaking into other dimension and not from any of the other myriad of possible effects. It is a good idea, I just don't see how it could work.
    • I wonder how they could conclude that a change of this magnitude would come from gravity leaking into other dimension and not from any of the other myriad of possible effects.

      The way any scientist would. List all known possibilities of your "myriad of possible effects". Then quantitatively estimate and calculate the magnitude of those effects on the orbit's precession. If all effects are less than the gravitional effect by some quantity greater than the experiment's margin of error, then you assume you

  • High School Physics (Score:5, Informative)

    by Soong (7225) on Friday July 07 2006, @09:14PM (#15680984) Homepage Journal
    Ok, some orbital mechanics.

    Going with a circular orbit because they didn't specify the ellipse:
    365.24*24*3600 = 31556736.00 seconds per year
    ./3000 = 10518.912 seconds per orbit
    1/. = .00009506686623103225 orbits per second
    .*.14*3.1415926*2 meters per orbit =
    .0000836 meters per second
    .*1000 = .0836 millimeters per second

    Pretty slow orbit. About that tungsten, 19250 kg/m3
    3.1415926*(4/3)*.04*.04*.04 = .000268 m^3
    .*19250 = 5.16 kg
    And let's say the planet is 8 mm in diameter, .004 m in radius
    3.1415926*(4/3)*.004*.004*.004 = .000000268 m^3
    .*19250 = .00516 kg

    F = G m1 m2 / r^2 =
    gravitational constant = 6.67300 × 10-11 m3 kg-1 s-2
    .00000000006673000000 * 5.16 * .00516 / (.1*.1)
    = .00000000017767262800 Newtons of force, resulting acceleration on the smaller body of
    ./.00516 = .00000003443267984496 m/s = .00003443267984496 mm/s

    Sounds reasonable to me. Assuming they can get a clean launch at exactly .0836 millimeters per second everything should be fine!

  • semantics (Score:3, Interesting)

    by v1 (525388) on Friday July 07 2006, @09:42PM (#15681081) Homepage Journal
    Once at the Lagrange point

    Lets review this. Lagrange point. Last I checked, a point is not a "region". So there's no way to put a titanium anything completely within a Lagrange Point. At the very best they might put the "sun" part of it centered at the LP, but then the "planetoids" would all be outside the LP, and however minorly, would be affected to varying degrees by the gravity of the earth and of the sun.

    This test is invalid. The use of a LP is not going to nullify the effect of gravity of the earth, let alone of the sun. If they are going to do a test that is this sensitive, there is nowhere in the solar system they can hold it and get accurate results.
    • Yes. You need to build a very precise spaceship. Starting with a sphere might be easiest as gravity cancels out everywhere inside a sphere. You'd probably need thrusters and things (although maybe you could make them detach and leave the scene after you were done with them) but you'd measure them very carefully so you could account for their effect.

    • Gauss's Law (Score:5, Informative)

      by amightywind (691887) on Friday July 07 2006, @08:49PM (#15680897) Journal

      Gauss's Law [wolfram.com] says that the gravitational acceleration of a body anywhere in an enclosed sphere is 0. At L4, L5 Earth and Sun graviational forces are balanced. The only accelerations that don't cancel out are the two body accelerations of interest. It is surprising to me that the bodies orbit as fast as 10 times per day. I wonder why they don't use heavier Uranium as the mass. It is an interesting side note that a body can stably orbit one of these points. They orbit with no body (!) at the focus. The Genesis Probe and WMAP missions have already taken advantage of this.

      • Re:Gauss's Law (Score:5, Informative)

        by bbaskin (24236) <bryanbaskin.sbcfreakingglobal@net> on Friday July 07 2006, @09:18PM (#15681005) Homepage
        If I had a nickel for everytime I heard someone suggest replacing a tungsten weight with uranium, I'd have a buck or so. Uranium (238 anyway) isn't denser than tungsten. Tungsten is the densist material for semi-practical applications. It's more available than iridium or osmium, and far less expensive than platinum, three more dense elements. For a few reasonably obvious reasons, neptunium and plutonium aren't really good alternatives to tungsten if you just want a dense lump of metal.

      • Re:Gauss's Law (Score:5, Informative)

        by Quantum Fizz (860218) on Friday July 07 2006, @11:40PM (#15681499)
        Gauss's Law says that the gravitational acceleration of a body anywhere in an enclosed sphere is 0.

        No it doesn't, re=read the law you linked to. It says the "surface integral of gravitational acceleration" will be zero over any arbitrarily-shaped closed surface, as long as that surface encloses zero mass. You cannot work backwards from this statement to assume that the local gravitational acceleration will be zero.

        Simple example. Imagine a closed surface (say a small sphere) 20 feet above the ground (and also assume there's no air inside) such that the surface is closed. Since it encloses no mass, the net acceleration will be zero as summed over the whole sphere. However, any object placed within this hypothetical spherical surface (eg a brick) will fall to the ground.

          • Do you even understand Gauss's law? My example did envelop the mass with a "Gaussian surface", the fact you don't understand that and yet resort to namecalling only makes you look both naive and immature.

            .

            Read my first reply to my comment for more clarification if you want. But as per your comment here, the surface integral of the vector field (dot producted with its infinitesmal area element, of course) is identically zero for any surface enclosing zero net source/sink density (ie, masses or charges).

    • Re:Why L2? (Score:5, Interesting)

      by addie (470476) on Friday July 07 2006, @07:18PM (#15680511)
      Well actually the article did say:
      A spacecraft placed there would stay fixed in space, relative to Earth, making it easier to monitor. The Earth would also shield it from the Sun's radiation, which pushes gently on any objects it shines on. Any such push could change the spacecraft's position relative to the tiny "planets" held inside it.

      So they've got that much of it thought out. But in regards to the mass of the spacecraft carrying this jar:
      And the spacecraft components themselves would exert gravitational forces on the spheres. These forces could be minimised by making the spacecraft as symmetrical as possible and putting its heaviest components as far from the artificial solar system as possible.

      "Such an experiment would be quite challenging to set up, but I don't think it is technologically impossible," says MOND expert Stacy McGaugh of the University of Maryland, US.


      So while they're full aware of the problems the mass of the craft can cause, they seem to think it's possible to minimize the effects to a reasonable level.

      My question is, aren't Lagrangian points going to start to get a bit crowded? There are only five to work with in our neighbourhood and who gets to say who uses which and for how long?
    • No big deal, plenty more scientists where they came from. I'd be more concerned about them creating a great big black hole, and us never being heard from again.

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