Would orbital mechanics work at human scales?

[Draconiator]

...In other words, if you were to take a bowling ball and a marble, and somehow keep them floating for long enough, could you make the marble orbit the bowling ball? was playing KSP, and was wondering if small things also have that effect. Had a gameplay question about this but I'll save that for another forum.

[XIRA]

Yes. But because the gravity is so low one orbit would probably take many many years

[RainDreamer]

I kind of wonder if someone tried making little things orbiting each other on the ISS before.

[Tommygun]

Years ago NASA was asking for ideas for simple science experiment to do in space to be shown in class rooms.

I wanted to suggest trying to get different size ball bearings to orbit rare earth magnets, but never got around to it.

I've also wondered if you could do it briefly on Earth. I'm thinking if you mounted the rare earth magnet on a stick and base plate, then suspended a ferrous ball bearing with a sting to the roof, you might get a few orbits out of it.

[Umlüx]

yes it would work.

watch this cool video:

(best explanation of gravity i have ever seen)

a teacher simulates gravitional effects with spandex and marbles and he gets 2 marbles to 'orbit' each other.

[Ralathon]

Yes. But because the gravity is so low one orbit would probably take many many years

Mass of a heavy bowling ball: about 7kg.

Radius of our orbit: Lets say half a meter.

Resulting orbital period:

2*pi*sqrt(0.5^3/(G*7)) ~ 28.5 hours.

So it isn't quite as bad as years. But still very very slow.

[tomf]

You probably wouldn't get this with sperical objects but accoroding to this XKCD http://what-if.xkcd.com/68/ the orbit od a non sperical body might be wierd and non-circular due to tidal effects.

[KerbMav]

I kind of wonder if someone tried making little things orbiting each other on the ISS before.

The ISS operates at 1 atm - so, would not work that well, would it?

[Z-Man]

Fun fact: The duration of a low orbit (negligibly far away from the surface) around a spherical object depends only on natural constants and the density of the sphere. So yes, this would work. But not on the ISS itself, as KerbMav says; air currents are going to mess everything up. Near the ISS is also not a very good place; tidal forces from Earth are going to be of equal magnitude to the gravitational forces between your bodies even if they are as close as possible. See Roche Limit. There is some leeway if you make your bowling ball out of gold, but your orbits are not going to be very stable. You'd have to do it further away from Earth.

[FishInferno]

I kind of wonder if someone tried making little things orbiting each other on the ISS before.

I don't think that would work due to the air in the ISS.

[Sirrobert]

They did an experiment on NASA with a charged needle and water drops:

For all intents and pursoses, the same thing as gravity in this situation (asuming the subjects are effected by magnitism)

[Bill Phil]

If there's no other major gravitational influence for a good long distance, yes.

[Mr Shifty]

...In other words, if you were to take a bowling ball and a marble, and somehow keep them floating for long enough, could you make the marble orbit the bowling ball? was playing KSP, and was wondering if small things also have that effect. Had a gameplay question about this but I'll save that for another forum.

You can, in fact, simulate exactly this with Universe Sandbox.

[lajoswinkler]

They did an experiment on NASA with a charged needle and water drops:

For all intents and pursoses, the same thing as gravity in this situation (asuming the subjects are effected by magnitism)

This is a decent analogue because you have an electric monopole (rod) and an object (water droplet) which can act like a charged object because of electrical influence.

Magnets can't do this because they're dipoles. It's something completely different and including them into the discussion about orbits just leads to huge confusion.

[michaelsteele3]

I don't know why, but this reminds me of this:

[pincushionman]

With gravity alone, you need to be far enough away from more massive bodies that the region of space dominated by the gravity of the "parent body" you're interested in (the Hill sphere) is comfortably outsde that body's surface. Near Earth, the influence of the Sun, Earth, and the Moon are great enough that the Hill sphere of any object we can take up with us intersects the object itself (Wikipedia states that the Shuttle's Hill sphere was roughly 2.4 m in diameter).

In the outer solar system, however, things are different. A bowling-ball-sized KBO would have a sgnificant Hill sphere just because it would be so far from any other influencing bodies.

Edited February 4, 2015 by pincushionman

[PB666]

The ISS operates at 1 atm - so, would not work that well, would it?

Yes but at 28 minutes the is next to no drag, the drafts are issue however. Even if the ISS had no atmosphere, the ISS has a higher GM than a bowling ball, and so eventually the bowling ball would get close enough to another more massive object the satellite with go hyperbolic. To do the experiment with as much favoritism one would use a ball made of lead with a magnetic feild that can be held at position, the satellite would be non magnetic but also dense, the the central body would be held in a position that had exterior gravity that was equal in all directions.

[-Velocity-]

Years ago NASA was asking for ideas for simple science experiment to do in space to be shown in class rooms.

I wanted to suggest trying to get different size ball bearings to orbit rare earth magnets, but never got around to it.

I've also wondered if you could do it briefly on Earth. I'm thinking if you mounted the rare earth magnet on a stick and base plate, then suspended a ferrous ball bearing with a sting to the roof, you might get a few orbits out of it.

Magnets don't work like gravity. They are dipoles, so in the far field the strength falls off with 1/r^3, and their fields are not spherically symmetrical. (The extra 1/r comes in there because the farther you are away from magnet, the closer and closer the two poles get relative to your distance away from them.)

It would be far better to do this experiment with balls with opposite electric charges. You could make those work exactly similar to gravity, since the equation for Newtonian gravity and Coulomb's law is essentially the same. If you put them in a vacuum chamber, you could make them orbit each other indefinitely.

Edited February 4, 2015 by |Velocity|

[Superfluous J]

If there's no other major gravitational influence for a good long distance, yes.

This is the big problem. Sure you could get a ball bearing to orbit a bowling ball, if it wasn't for that doofus floating in space nearby screwing up the gravitational field.

[Tommygun]

Magnets don't work like gravity. They are dipoles, so in the far field the strength falls off with 1/r^3, and their fields are not spherically symmetrical. (The extra 1/r comes in there because the farther you are away from magnet, the closer and closer the two poles get relative to your distance away from them.)

It would be far better to do this experiment with balls with opposite electric charges. You could make those work exactly similar to gravity, since the equation for Newtonian gravity and Coulomb's law is essentially the same. If you put them in a vacuum chamber, you could make them orbit each other indefinitely.

Oh yes, I forgot about the poles. Maybe those Styrofoam packing peanuts would work.

I have manage to levitate packing peanuts for several minutes with a static charge.

[Voyager55]

Shot answer, yes. It takes only highschool level physics to make the calculations if you know the mass of the marble and the bowling ball. You can calculate the velocity required to maintain an orbit at a certain radius, and then from the velocity you can calculate the orbital period.

But I took the liberty of doing the calculations assuming the Bowling ball has a mass of 3Kg and the Marble, .020Kg at an orbital radius of 1 meter.

The marble would orbit the bowling ball at 2.0x10(-10) m/sec, and each orbit would take about 1030 earth years.

[Ralathon]

Shot answer, yes. It takes only highschool level physics to make the calculations if you know the mass of the marble and the bowling ball. You can calculate the velocity required to maintain an orbit at a certain radius, and then from the velocity you can calculate the orbital period.

But I took the liberty of doing the calculations assuming the Bowling ball has a mass of 3Kg and the Marble, .020Kg at an orbital radius of 1 meter.

The marble would orbit the bowling ball at 2.0x10(-10) m/sec, and each orbit would take about 1030 earth years.

Sure you did your maths correctly? Orbital period of the small body should be about 2*pi*sqrt(1^3/(G*3)). And that gives me an orbital period of about 5 days.

[Voyager55]

Are you positive that your calculations are correct?

I'll run through the process I went through to get my answer.

Using the equation G(M1)(M2)/r = v(squared)

I calculated that the marble would need an orbital velocity of 2.0x10(-10) m/sec to maintain an orbit at 1 meter around the bowling ball.

I then calculated the circumference of a 1 meter orbit which is 6.3 meters.

And then it was a simple T = d/r Time = 6.3/2.0x10(-10)

Which gave me 3.2x10(-10) seconds, which I divided into hours, then days, then years.

Which in the end gave me 1028 years which I rounded to 1030.

I was pretty sloppy with the scientific notation, but i'm fairly confident in my result.

[Ralathon]

Are you positive that your calculations are correct?

I'll run through the process I went through to get my answer.

Using the equation G(M1)(M2)/r = v(squared)

I calculated that the marble would need an orbital velocity of 2.0x10(-10) m/sec to maintain an orbit at 1 meter around the bowling ball.

I then calculated the circumference of a 1 meter orbit which is 6.3 meters.

And then it was a simple T = d/r Time = 6.3/2.0x10(-10)

Which gave me 3.2x10(-10) seconds, which I divided into hours, then days, then years.

Which in the end gave me 1028 years which I rounded to 1030.

I was pretty sloppy with the scientific notation, but i'm fairly confident in my result.

You forgot to take the root of G(M1+M2) to get the actual velocity from the squared velocity. G(M1+M2) is indeed 2e-10, but the root of it is only 1.4e-5 m/s giving an orbital period of about 5 days.

[Norpo]

Sure you did your maths correctly? Orbital period of the small body should be about 2*pi*sqrt(1^3/(G*3)). And that gives me an orbital period of about 5 days.

Can confirm, used Universe Sandbox.

A 2 gram die orbiting a 3 kg bowling ball with a semi-major axis of 1 meter, in a roughly circular orbit has an orbital period of 5.15 days. Close enough it could be rounded to 5 days, and certainly nowhere close to 1030 years.

EDIT: To get an orbital period of 1030 earth years, the die/marble would need a semi-major axis of 1.75 kilometers. That's 1750x more.

Edited February 5, 2015 by Norpo