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# Einstein's orrery

Small spheres rolling in a hyperbolic funnel symbolizing space time curvature
 (+6) [vote for, against]

I've seen this done on computer simulations, but never in actuality. It seems like something that should be in a science museum somewhere, but I haven't been able to Google it. So my apologies if this is already baked, but I've never seen one.

The idea is to take a shallow plastic hyperbolic funnel and suspend a small glowing "sun" over the center, then orbit steel planets around it. The funnel is plastic as you will need to have magnetic accelerators embedded in the funnel which will periodically accelerate each of the planets to account for friction.

The advanced set would actually use non-rolling shells over the balls with the planet designs on them, which would allow the addition of Saturn's rings and allow the addition of our moon where the shell of the moon had a magnet (or string if a powerful enough magnet cannot be found) on it's Earth facing face to add in the Earth's gravitational field.

Sadly for simplification and for realism poor Pluto would have to be demoted for it's non-planer orbit.

 — MisterQED, Feb 17 2010

Planequarium Planequarium
[theircompetitor, Feb 17 2010]

Pluto is just the most extreme deviation from the Ecliptic. Also, what about the precession thing which general relativity predicts?
 — nineteenthly, Feb 17 2010

 Precession thing? Sorry, I learned relativity in the eighties, so I've forgotten most of it from disuse.

For me the coolest thing would be the possibility that the moon would orbit the Earth correctly which would show how it gets twice the pull from the Sun as it gets from the Earth. Also the possibility of showing an asteroid belt and comets.
 — MisterQED, Feb 17 2010

You call that an asteroid belt ? Fashion victim ...
 — 8th of 7, Feb 17 2010

//someone wearing flares// - Coming out of the sun?
 — wagster, Feb 17 2010

Solar Flares ...
 — 8th of 7, Feb 17 2010

 I think it would be nifty. I've never understood the precession thing. Mercury's orbit precesses because of relativity, and presumably the others do too. Newtonian gravitational theory doesn't predict that. I don't know why it happens.

To be really anal about it, each body needs a gravity well, which wouldn't make much difference to most of them. The elasticity of the surface would be important. There would also be losses via friction, and i'm wondering how that could be alleviated. Little motors maybe?
 — nineteenthly, Feb 17 2010

 // which wouldn't make much difference to most of them //

You want to try that one again when you're in a decaying orbit ? Yes, it makes a difference. The masses of the planets are small compared to your sun, but they're still non-zero.
 — 8th of 7, Feb 17 2010

It makes a difference to large objects in the solar system over a long period. In this scenario, it would depend on the detail, on the whole. I would expect comets to be the most affected, but even that would take hundreds of orbits at least, on the whole.
 — nineteenthly, Feb 17 2010

 Hint: you have to speed up time in proportion with space ....

Your squalid little planet's orbit is 150 million of your kilometers from your sun. Squeeze it down to a couple of metres and the planets are going to whizz round like demented wasps in a jam jar.
 — 8th of 7, Feb 17 2010

I see that, but i didn't imagine this would be an exact model because if it were, it would be the size of a football field and have the occasional sand grain or marble representing each planet. I saw it as obeying Kepler's laws but ignoring the gravitational influence of each major planet except maybe the barycentre of the whole solar system.
 — nineteenthly, Feb 17 2010

Well, if you're not going to take it seriously, why bother ?
 — 8th of 7, Feb 17 2010

 // I've never understood the precession thing. Mercury's orbit precesses because of relativity, and presumably the others do too.// Oh, wait, I remember this one. The effects of gravity cannot travel faster than the speed of light, so the gravity vector is not directed at the center of the sun, but is offset slightly due to relativity. So, no, this wouldn't handle precession.

I thought about creating each of the gravity wells, but because of friction, you'd have to completely mechanize the motions of the planets and even then the resulting surface would have significant friction. By simplifying the geometry by only showing the sun's gravity well, you could get natural planetary elliptical orbits and only have to mechanize smaller perturbations using magnetic fields. The causation wouldn't be perfect, but it would be interesting and the motions could all be corrected by immobile radially aligned magnetic linear accelerators. If the hyperbolic funnel is shallow and the planets are massive enough the systems could be slowed to a reasonable level.
 — MisterQED, Feb 18 2010

//barycentre// I love this word, but it always conjures up an image for me of some 1960's architected shopping precinct (possibly somewhere in Kent) that's populated entirely by people called Barry.
 — zen_tom, Feb 18 2010

The recent fascination with orreries the Half Bakery has developed, is somewhat disconcerting...
 — MikeD, Feb 18 2010

 //The recent fascination with orreries the Half Bakery has developed, is somewhat disconcerting..// Why? Not to start a flame war, but [MikeD] were you not here for the custard? Or is that a perennial theme along with vacuum balloons? I personally had to look up to find out what the word meant and that is what I expect from the HB. I'm a pretty smart guy, or at least that is what my mom tells me, and I generally feel like an idiot here and that doesn't even count the [Vernon] posts.

So the word of the week is orrery. Next week I expect to be dragged to another obscure page in Wikipedia. Bring it on. :-)
 — MisterQED, Feb 18 2010

 [MikeD], you say the precession is to do with the speed of the force, as it were. That could in fact be duplicated here through the speed of the shock wave in rubber, or whatever the sheet's made of. That would presumably mean that matching that property of the material to the densities and masses of the objects concerned could theoretically, again avoiding the issue of friction, reproduce the precession, or at least _a_ precession. The other thing is that i don't think the inverse square law is going to work in quite the same way with this because you're comparing dimples in a surface with "hyperdimples" in a volume. I have a hunch that the forces concerned would diminish linearly with distance rather than as the square root of the inverse proportion of the distance, and surely that would make a difference? I also wonder if the gradient is scaled down, you could compensate for that.

Having said all that, it would still be interesting.
 — nineteenthly, Feb 18 2010

 [19thly], I think you are commenting on the anno I left on the other orrery idea.

[Mr.QED], I'm not complaining. Hell I jumped on the orrery idea band wagon. I had previously known about orreries, but I was absolutely fascinated with them when I did learn about them. Were it not for the large price tag, I would assuredly have an orrery. So I guess I can see where it is coming from. Albeit, I am in a flame war kind of mood, and [21quest] just hasn't been very combative lately.
 — MikeD, Feb 18 2010

Not sure, [MikeD]: it's all got a bit confusing in the last few days, hasn't it?
 — nineteenthly, Feb 18 2010

The National Museum in Edinburgh has donation boxes in the form of large shallow plastic hyperbolic funnels, with tangential coin launchers. It's fun to shoot a thin, large-diameter coin down them - 2p works well. It's suprising how much friction there is from a rolling coin on a plastic surface. (dead coins that people have mis-launched don't help...)
 — pocmloc, Nov 05 2015

 // Edinburgh //

Just how long did you have to wait until someone put a coin in ? Presumably, until a non-scotch person arrived ...
 — 8th of 7, Nov 05 2015

So it is just a model solar system?
 — travbm, Nov 05 2015

I used my own coin thank you very much!
 — pocmloc, Nov 05 2015

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