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Solar System in a Can May Reveal Hidden Dimensions 251 251

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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Solar System in a Can May Reveal Hidden Dimensions

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  • Gotchas, we got em (Score:3, Interesting)

    by Ancient_Hacker (751168) on Friday July 07, 2006 @07:53PM (#15680395)
    This sounds mighty dubious. The gravitational attaction of the spacecraft is likely to be much larger than the effect looked for.
    • by d34thm0nk3y (653414) on Friday July 07, 2006 @08:00PM (#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.
    • by pilgrim23 (716938) on Friday July 07, 2006 @08:04PM (#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.....
      • I hear they gotta lotta nice girls.
      • 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

    • by ceoyoyo (59147) on Friday July 07, 2006 @08:11PM (#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.
    • Every time I turn around someone is trying to launch balls into space. First we had those balls that were suppose to detect gravitational waves, now we have these balls that are suppose to rotate around each other. What's next, balls on the moon, mars, and beyond?
    • by KFury (19522) *
      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
      • Only L4 and L5 are stable over astronomical time scales. Orbits around L2 decay over a few years so the point is just about free of natural objects.
      • >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

    • by Rob Carr (780861) on Friday July 07, 2006 @09:02PM (#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.

      • In Freshman physics, you demonstrated that the net gravitatinoal attraction inside a uniform sphere is zero? Are you sure you did this experimentaly and not just on paper? Maybe the state of Freshman physics has improved since my days, but color me sceptical.
        • by Rob Carr (780861) on Saturday July 08, 2006 @01:27AM (#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.

    • Perhaps, but the gravitational attraction of the spacecraft would be accounted for... even if, at first, it might be subtle, the eventual results of the gravitational force of the spacecraft would definitely be noticeable.

      Any unexplained change, basically, is cause for more research.
    • But any external gravitational forces will act very nearly identically upon both the tungsten 'sun' and the test sphere.

      The net force exerted by nearby (distance to test system less than, say, 1000 times the distance between the test sphere and the 'sun') objects can be fairly trivially determined by measuring movement of the test sphere relative to some fixed point. After that, the effect of local gravitational attraction can be readily eliminated. Some measurement or calculation of gravitational noise c
    • reminds me of douglas adams fairy cake theory a little:
      To explain: since every piece of matter in the Universe is in some way affected by every other piece of matter in the Universe, it is in theory possible to extrapolate the whole of creation - every sun, every planet, their orbits, their composition and their economic and social history - from, say, one small piece of fairy cake.
  • Outside effects? (Score:2, Interesting)

    by Clazzy (958719)
    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.
    • Re:Outside effects? (Score:3, Informative)

      by Compholio (770966)
      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]
      • by HelloKitty (71619)
        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.
      • What's wrong with studying the moon's orbit?
        • The moon and Earth have irritating imperfections like mountains. Plus there are all kinds of other significant influences like other planets and the sun. It's actually not possible to predict the moon's orbit accurately very far into the future because the other bodies in the solar system make it semi-chaotic. The moon doesn't orbit the Earth 3000 times a year either, so you'd have to wait longer to see the same magnitude of precession.
    • F = G * (m1*m2)/r^2

      The effects of gravity drop off pretty quickly as the distances increase.

      As others have mentioned, the bigger problem is the small amount of gravity caused by the ship itself.

      It could be accounted for, especially if the ship was designed so that it's gravitational effects could be accounted for... but it's still a challenge in an experiment like this where precision is key, and the effects they're looking for might be very small.

      Maybe they should consider using bigger orbs for the sun and
  • Yeah, but... (Score:2, Interesting)

    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) <johnsonmx&gmail,com> on Friday July 07, 2006 @07:57PM (#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.
  • by Toby The Economist (811138) on Friday July 07, 2006 @07:58PM (#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?

    • Read the summary again - nowhere is a 10cm sphere mentioned.
    • by erice (13380) on Friday July 07, 2006 @08:19PM (#15680520) Homepage
      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.


      No doubt. The only reason there is any hydrogen on *Earth* is because it binds readily with more massive elements. Helium does not and, as a consequence, any helium released into the atmosphere will ultimately escape. My understanding is that the only reason we have any helium at all is due to radioactive decay from heavier elements
    • Not only that, Lagrange points aren't necessarily stable. The article mentions L2, which is one of the unstable lagrange points, meaning that it requires station keeping (occasional thruster firing), I'd think that would interfere with this experiment.
    • by Cecil (37810) on Friday July 07, 2006 @09:26PM (#15680805) Homepage
      Actually, an 8cm tungsten sphere would exert the same gravitational pull on any object 10cm away, regardless of the other object's mass. It would have an escape velocity of 0.013 cm/s or 1.3 microns per second -- which, while very slow, is certainly within the realm of feasability. Your hard drive heads move accurately with tolerances significantly smaller than that.

      I calculated the escape velocity using the formula sqrt(2Gm/r) [yale.edu]:

      sqrt((2)(6.6742x10^-11)(5.16)/0.4) = 0.00013m/s or 0.013cm/s
      • > Actually, an 8cm tungsten sphere would exert
        > the same gravitational pull on any object 10cm away,
        > regardless of the other object's mass.

        Need a real physicist to answer this, but I'm half-guessing this is wrong; I think the greater the mass of an object, the more it is attracted to another object - but its mass in exact proportion cancels out the additional pull, by simple dint of being more massive and thus requiring more force to move.

        This is why high and low mass objects fall at the same rate
      • There's no way it would orbit 3,000 times a year, right? It'd have to go very slowly to keep from escaping the gravity well of the tungsten sphere and at that speed, it couldn't cover much ground (even less than 2*pi*10cm*3000 per year).

        Right?
        • Assuming the "10cm" orbit number is altitude from the surface of the tungsten sphere, it actually would orbit 6,000 times a year. It would move at 1.66E-4 m/s, or 1 cm/minute. The orbital path is about 90cm around (14cm*pi), so it would orbit about every 90 minutes, meaning 16 per day * 365 days or about 6,000 a year.

          Amazing. I would have said it was impossible.
      • "Actually, an 8cm tungsten sphere would exert the same gravitational pull on any object 10cm away, regardless of the other object's mass"

        Yes, but you're forgetting that the second object has a gravitational pull too; a larger secondary object will have a greater pull back, meaning a greater combined pull.

    • Fortunately, thermal velocities of macroscopic objects are much lower than those of atoms.
    • Density of tungsten: 19250 kg/m^3
      Mass of 8cm-wide sphere: density * volume = 19250 kg/m^3 * (4/3 * pi * (4cm)^3) = 5.2 kg
      Gravitational acceleration of negligible-mass object towards mass M at distance r: a = GM/r = G * 5.2kg / 10cm = 3.4e-9 m^2 s^-2
      Acceleration of object rotating in a circle at speed w and distance r: a = r^2 w^2
      Hence a = (10cm)^2 w^2 = 3.4e-9 m^s s^-2, so w = 0.0006 s^-1 (radians per second)
      0.0006 rad/sec = 19000 rad/year = 2950 [google.com] orbits per year. Which is about 3000, as they say.
  • I got black text on a mostly black background. Sheesh! The printable page [newscientistspace.com] reads a lot better.

    Flyboy 8v)
  • by exp(pi*sqrt(163)) (613870) on Friday July 07, 2006 @08:18PM (#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
    • A "dimension" is just a variable in an equasion, not as much of a physical property as connotations of the word imply, but a property of the physical 'stuff' that an equasion is describing. Any of the dimensions that we see may actually be functions of more than one dimension for certain calculations.

      So, the number of dimensions there are depends purely on what you're calculating. Many dimensions may fold into fewer dimensions for some calculations (think, simplifying an equasion). There is likely, though,
  • by MindStalker (22827)
    Article states the orbit would be 1/3,000 degree in year.
    This is MUCH MUCH less than 3000 times in year
    • Sorry I screwed up summary is correct, the 1/3000 degree is the estimated change or something to that effect.
      • The article says the system may precess [wikipedia.org] by 1/3600 degrees in a year, while still orbiting 3000x/year.

        For an oval orbit, to precess means that the oval of the orbit will also be rotating, and that rotation can be measured. That's precession. The planets in our solar system do this too. Precession is what makes this the Age of Aquarius [wikipedia.org].

        Let the Sun shine in.

        David
  • 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
    • This fairly clearly implies intelligent action.

      "Hidden" doesn't imply intelligent action. E.g. "The sun was hidden behind the clouds"

      Besides, something can't be hidden and yet physically interact with the universe.

      Yes it can. Sub atomic particles were hidden for most of history and yet they had no trouble physically interacting with the universe.

      despite being able to probe to fundamental scales (planck, anyone?)"

      No-one is poking around at those scales.
  • by grumling (94709) on Friday July 07, 2006 @08:47PM (#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 @09:29PM (#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?
  • Hmm... (Score:2, Insightful)

    by muzammal (987574)
    Would the fact that this little universe would be enclosed in a spaceship have any effect on it?
  • interesting but (Score:5, Insightful)

    by rucs_hack (784150) on Friday July 07, 2006 @09:52PM (#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.

    • 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.

      Nevermind that, how about we start actually sending mostly scientists to space!

      Currently, the vast majority of people visiting space come from regular militaries, and almost every mission has some military goal as its primary purpose, with the "science" aspect coming in only as an "oh yeah we can fit one of those things in there too".
    • Re:interesting but (Score:3, Insightful)

      by Kopretinka (97408)
      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".

  • by mcguiver (898268) on Friday July 07, 2006 @09:52PM (#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

  • Wow... (Score:2, Funny)

    by Jugalator (259273)
    I nominate this for the strangest news article title of 2006.
  • High School Physics (Score:5, Informative)

    by Soong (7225) on Friday July 07, 2006 @10:14PM (#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!
  • It won't work. (Score:2, Insightful)

    Wouldn't the space ship exert its own gravity on the system and ruin the whole experiment?
  • So, they're going to use actual bodies as a computational model that measures the fit of a theoretical model to actuality? Sounds fishy. Using reality as a model of reality...couldn't that lead to some kind of infinite regress? A semantic gravitational collapse? Before we all disappear behind the denotational event-horizon, perhaps we should run a (safe) computer simulation modelling the idea of using reality as a way of testing our models of reality.

    In any case, given the risks, I think they should ban t

  • semantics (Score:3, Interesting)

    by v1 (525388) on Friday July 07, 2006 @10:42PM (#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.
  • ...and place it at the Lagrange point between the Moon and the Earth. There, external forces may be minimized, and some productive observations could be made. Any experiment which tries to measure "extra dimensions" or whatever would have to have such a low margin of error that yes, it would be IMPOSSIBLE to acheive within a space craft. Don't believe everything you hear -- the fundamental laws of physics are still the most important considerations at the scale of observation currently possible.

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