From the linked idea comes a proposal to give the Moon Saturn-like rings, using vacuumed-up moondust.

However, planetary ring structures and stablity are poorly understood, though it is thought that many tiny moonlets act to maintain the structure.

To this end, I propose orbiting golf balls around the Moon, named in honour of its first golfer.
-- coprocephalous, Jun 02 2009

See [theleopard]'s anno. Broom_20the_20Moon
[coprocephalous, Jun 02 2009]

Shepherd moons http://en.wikipedia...wiki/Planetary_ring
[coprocephalous, Jun 02 2009]

Planet You Planet_20You
Own your own planet for $100. I always thought this was one of my best ideas. [xenzag, Jun 02 2009]

The Soundtrack http://www.allmusic...sql=10:3ifexqt5ldfe
Shepherd Moons, by Enya [neutrinos_shadow, Jun 03 2009]

[theleopard] was responding to an anno by [AbsintheWithoutLeave] which introduced the vacuuming thing - but I think some of us may have missed [Awol]'s subtle (vacuum based) joke.
-- zen_tom, Jun 02 2009


//some of us may have missed [Awol]'s subtle (vacuum based) joke//

I didn't miss it. It just sucked.
-- Jinbish, Jun 02 2009


This idea is great, especially because there is so much more that Humanity can do to add to the space garbage already in orbit of Earth.
-- PauloSargaco, Jun 02 2009


[Jinbish] It was a joke, wasn't it?
-- PauloSargaco, Jun 02 2009


I thought of it as a way of finding a use for golf balls.
-- coprocephalous, Jun 02 2009


Jokes aside, I do really like the idea - how hard would you have to hit a lunar golf ball to put it in orbit?
-- zen_tom, Jun 02 2009


//how hard would you have to hit a lunar golf ball to put it in orbit?//
About one sixth as hard as you would have to hit it to put it into Earth orbit.

Still quite a lot.
-- coprocephalous, Jun 02 2009


Not as hard as if you were on Earth...

Right. Well. Assuming a circular orbit, with Kepler's & Newton's shenanigans, there's a F=Gm1m2/r.r equated with F=m.v.v/r and a little bit of jiggery pokery. Unfortunately, I can't remember any more of my school physics.

Yes [Paulo], there's definitely a lack of seriousness in there somewhere! And I have to admit to wanting to throw in a pun too.
-- Jinbish, Jun 02 2009


Even though I don't play golf, I admit it should be awesome to play it on the moon. I mean, if they could slim those spacesuits down a bit. At least enough so that you could swing a golf club. But imagine, without air drag and with only a sixth of Earth gravity, those golf balls could go pretty far. Maybe enough so that they would have to forbid golf playing inside flight paths.
-- PauloSargaco, Jun 02 2009


Plus, there'd be no draw or fade - which would be a boon, on the moon.
-- zen_tom, Jun 02 2009


You can't put a golf ball into orbit by hitting it from the surface of the moon. If it doesn't escape to infinity, it'll be in an orbit which intersects the moon's surface, so at some point it'll hit the ground.

To get into orbit you need to perform a "circularising" manoeuvre when the ball has reached the right altitude.
-- Wrongfellow, Jun 02 2009


Wrongfellow, if you hit it *just* right, it should be possible to for the trajectory to result in a circular orbit.
-- zen_tom, Jun 03 2009


No, [Wrongfellow] is right, any ballistic orbit will include it's starting point, so you need to Tee off in a tower and then take down the tower. The lack of atmosphere should allow a highly eliptical orbit with an apogee of a few feet.
-- MisterQED, Jun 03 2009


Really? A trajectory is normally considered parabolic, but that's a simplification based on the assumption that the surface from which a thing is ballisticated is a flat surface.

I agree that a straight-up launch would require a secondary, sideways thrust to get it to go around the planet, that's fair enough - but say you launched something at 45° (or some other non perpendicular trajectory) and imparted just enough energy to mean that the peak of the parabola was such that the object would have enough "sideways" motion to slip into a circular orbit. It's the same thing as [Wrongfellow]'s suggestion, only you're giving the object the sideways thrust at the beginning, simultaneous to giving it the upwards push.
-- zen_tom, Jun 03 2009


Won't work, I'm afraid. Orbits are ellipses (assuming the parent body is a point mass, which I think is reasonable for this discussion) and an orbiting body can only move from one possible ellipse to another through the application of an acceleration.

So if you accelerate the body from ground level, it will always end up moving on an elliptical path which intersects the ground, no matter what angle you accelerate it at.

To put a body into a genuine orbit, you have to get it onto an elliptical path that doesn't intersect the ground at any point, and so the final application of acceleration must necessarily happen far from the ground.

Or another way to look at it is that Newtonian mechanics is fully reversible. Imagine the time-reversed equivalent of your scenario: a body in a stable circular orbit which suddenly decides to plunge parabolically groundwards. Why did it do that? It can only do that if you apply a force to it.
-- Wrongfellow, Jun 03 2009


//I didn't miss it. It just sucked.//

I'm glad I came back to this idea. I missed the humor in that response the first time.
-- Zimmy, Jun 03 2009


I am afraid [Wrong...] and [MrQ...] are correct. There is also the problem of Earth being a little too big and a little too close.

However, if you are amenable to ribbons of dust, this might work.
-- 4whom, Jun 03 2009


Wait a minute - let's take Wrongfellow's argument about reversible physics a bit further here - and imagine a satellite in orbit whose orbit is slowly but steadily decaying - it will eventually come crashing back to earth and all without anyone prodding or poking it while it is in orbit.

I guess we could say that this satellite's original orbit just wasn't 'stable' - But stability is relative! - that satellite may have been in orbit for 20 years, but in geological terms, the orbit would be seen as a flash in the pan.

And so, if a satellite's orbit can naturally decay into a death spiral, then so mightn't there be a *perfect* ballistic trajectory that might work in reverse?
-- zen_tom, Jun 03 2009


The orbit decays because it's not in a perfect vacuum; it's being prodded and poked by molecules of air.

The time-reversal of a satellite's orbital decay is a situation where those stray air molecules etc are colliding with it in just the right way to gradually speed it up and boost it into a higher orbit.

Theoretically possible, but in practice entropy is against you.

(And herein lies a very interesting question: if physics is perfectly reversible, where does the "arrow of time" come from?)
-- Wrongfellow, Jun 03 2009


[Wrong...] Call SuSy, she's got one of the answers.
-- 4whom, Jun 03 2009


I completely misread this - I thought it would be some invention loosely based around the idea of Alan B. Shepard showing his bottom.
-- hippo, Jun 03 2009


Bit of a leap here, but isn't there an analogous thing to reversing the arrow of time and the idea of being able to calculate the nth Prime Number?

By which I mean that the nth Prime is dependent on all n-1 primes prior to it - in the same way that the nth moment is dependent on the n-1 moments prior to it.

Also, considering direction of time is odd when you're doing sums.
-- zen_tom, Jun 03 2009


Satellite^2?

{Now I can only think of "Sleeping Satellite" by Tasmin Archer}
-- Dub, Jun 03 2009


There is another force available which could, in theory, circularise the orbit - the Earth's gravity. It would be a particularly tricky three-body problem, and a damn tricky shot.

Which gives me an idea...
-- BunsenHoneydew, Jun 12 2009


//Now I can only think of "Sleeping Satellite" by Tasmin Archer//
I think you can get counselling on the NHS for that.
-- AbsintheWithoutLeave, Jun 12 2009



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