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Claude Remains
11-03-2010, 12:22 AM
If I could set one of these (http://s7.thisnext.com/media/largest_dimension/CC8AE352.jpg) units into motion in the vacuum of outer space would it be a case of true perpetual motion?

Washoe
11-03-2010, 12:37 AM
Errr…what exactly are they and what do they do? The criterion for a perpetual motion machine is that it is capable of doing work. Simply moving forever is not impossible, and in and of itself does not qualify as perpetual motion.

Spatial Rift 47
11-03-2010, 12:51 AM
No, it would not be a perpetual motion machine. There can be no perpetual motion machine. If you set this thing going in the vacuum of space, it would immediately begin to radiate energy away in the form of electromagnetic radiation, also known as light. Friction in the joints would heat the metal and the heat would radiate away. Eventually it would come to a stop.

Say it with me now, all together: There is no such thing as a perpetual motion machine.

Washoe is correct in saying that "simply moving forever is not impossible", but only in the scenario where all an object does is travel through space with a constant velocity. The difference there is no part of the object moves relative to any other part of the object - that causes, broadly, friction, and hence energy loss.

Claude Remains
11-03-2010, 01:08 AM
Ah.I didn't know that such a device needs to be "capable of doing work". The linked toy (http://www.youtube.com/watch?v=ibFtijBf3zE) is just that, a toy. Not sure if it runs on batteries. My question is now - if I were to put this toy into motion in the vacuum of space, how long could it go without batteries?

Claude Remains
11-03-2010, 01:20 AM
Eventually it would come to a stop.

Not to be a PITA but can we get a ballpark figure on "eventuallly"? I felt that my OP was kind of silly but I want to believe that it would spin for a good long time.

Claude Remains
11-03-2010, 02:15 AM
I now have found that this toy is Kinetic/magnetic. I would love to see a post by CHRONOS with any info regarding life expectancy in vacuum of space. Thanks for letting me play in GQ. :)

Finagle
11-03-2010, 10:23 AM
Looking at the device, it looks like it needs gravity to initiate a pendulum effect. In which case, outer space wouldn't be particularly beneficial. But ignoring that, the lack of atmosphere would result in reduced resistance in the pendulum, however you'd also boil or sublimate away any lubricating oils on the bearings in the pendulum So it's probably a wash -- it wouldn't run noticeably longer than on Earth is my guess.

Spatial Rift 47
11-03-2010, 01:46 PM
Not to be a PITA but can we get a ballpark figure on "eventuallly"? I felt that my OP was kind of silly but I want to believe that it would spin for a good long time.

Hard to say without at least a rough estimate of the coefficients of friction in the joints. Finagle makes a good point about losing lubrication to the vacuum via sublimation. That'll drive the friction up rapidly. However, heat loss via radiation is surprisingly inefficient, so depending on the cohesiveness of the lubrication and the design of the joint, it could freeze up within seconds or run for hundreds of years.

11-03-2010, 02:06 PM
Ah, the toy that prompted my "Goofs" entry on IMDb for Iron Man 2.

Which now appears to have been removed. Huh.

Chronos
11-03-2010, 02:22 PM
Bearing friction is probably much more significant for one of those things than air resistance, anyway. So it'd take about as long to stop in a vacuum as it would in normal Earthly conditions. Now, there are some desk-toys which use magnets for most or all of their bearings, and those would probably go much longer in vacuum, but there's still always some dissipative force, from something.

CookingWithGas
11-03-2010, 03:46 PM
I had a desktop toy that was similar (http://www.amazon.com/Westminster-Space-Shuttle-Kinetic-Art/dp/B000Z9C5P4/ref=pd_sbs_op_6) (but costs 1/30 as much!) It has a magnet in the base and requires a battery, I imagine it's a small electromagnet. I think without gravity it would reach equilibrium relatively quickly.

wbeaty
11-03-2010, 09:12 PM
I had a desktop toy that was similar (http://www.amazon.com/Westminster-Space-Shuttle-Kinetic-Art/dp/B000Z9C5P4/ref=pd_sbs_op_6)

Note that all these little gadgets are powered by the H.E. Stockman one-transistor magnetic pendulum motor, http://ajp.aapt.org/resource/1/ajpias/v29/i6/p374_s2 I hear that Stockman never made any money off the invention.

Squink
11-03-2010, 09:31 PM
Not sure if it runs on batteries.
Ideal for conference rooms, medical offices, exhibition areas, waiting rooms, display windows, and foyers, this display provides sophisticated style and unmatched entertainment!

Runs on 4 "AA' batteries (not included).

http://www.scientificsonline.com/swinging-sticks.html

Crafter_Man
11-03-2010, 09:50 PM
People pay \$289 for this (http://www.youtube.com/watch?v=ibFtijBf3zE)?