Listen to me kid, this is important...

September 18, 2009 4:53 PM

"There are only two types of motion in the universe: oscillation or rotation and you can't have exclusively one without a trace of the other. That's the reason machines wear out." Does this statement statement have any basis in fact and can you tell me where it might have originated?

I heard that from an in-law's father many years ago. He was an old, old guy who'd been a car mechanic and blacksmith. He said it with the sort of intensity that people usually reserve for things they've cooked up themselves but I always wondered if it was original.

posted by bonobothegreat to science & nature (17 comments total)

I don't see how this statement disregards acceleration, and forward motions, maybe it was meant of something more specific, like wave motion.
posted by Benzle at 4:59 PM on September 18

This article suggests that the statement has some basis in fact:

Diagnostics of Rotating Machines Prior To Balancing

One of the conclusions: The vibration of a machine on the rotation frequency may be caused, not only by the rotor unbalance, but also by a number of different oscillation forces appearing with certain defects as well.

As to being only two types of motion in the universe, well that sounds like an overgeneralization. It seems there must be some way for an object to be translated through space where no rotation nor oscillation takes place.
posted by Roger Dodger at 5:06 PM on September 18

While it's true that when a car drives down the road its wheels rotate and the pistons int he engine oscillate, the car itself does neither.

And there is no causitive relationship between those kinds of motions and equipment wear. Equipment wear comes from friction.

It reads like nonsense to me.
posted by Chocolate Pickle at 5:07 PM on September 18 [1 favorite]

oscillation is a form of translation.

A mechanical assembly by its very connectedness can only oscillate or rotate.
posted by Palamedes at 5:12 PM on September 18

you can't have exclusively one without a trace of the other

Assuming that we're applying this to a mechanical assembly, as Palamedes notes, then this part strikes me as true - no parts are mathematically perfect in shape thus no parts can be perfectly balanced. A spinning thing will always have some amount of wobble, and an oscillating thing will impart equal-and-opposite-reaction to it's housing, which in turn will rotate slightly back and forth around it's center of mass, (or if it is connected loosely to something, that joint will act as a pivot).

Everyone has their own way of understanding things in a way that makes sense to them. It sounds to me like this is the way of thinking about machine vibrations that made sense to this mechanics.
posted by -harlequin- at 5:19 PM on September 18

Atoms' electrons rotate about their nucleus. All matter is comprised of atoms.

Therefore...
posted by dfriedman at 5:24 PM on September 18

Those neat little pictures of electrons rotating around the nucleus like planets around the sun? Wrong, I'm afraid, for nearly a century.

As for the in-law's pronouncement, it seems to deny straight-line motion, which is odd. What does he think a piston does? But perhaps he meant that minor wobbles are common troubles in machines, which sounds like a good rule of thumb.
posted by zompist at 5:49 PM on September 18 [1 favorite]

Since the context is "why machines wear out" then I'd say it's true. Any machine meant to be used more than once (i.e. has time to wear out) has to return to some initial state to be used again. That implies either an oscillation or a rotation, otherwise how do you return to the base state?

As others have mentioned, it's seems more or less plausible that it's hard to have one without the other in practice.

That said, this is not why machines wear out. If your "machine" were a block sliding on an infinitely long plane, it would have neither oscillation nor rotation but would still wear out. Friction is the main foe of mechanics.
posted by DU at 5:52 PM on September 18 [1 favorite]

What does he think a piston does?

Well, a piston certainly oscillates. I'm sure its motion would look like a nice little closed loop in phase space.
posted by mr_roboto at 6:14 PM on September 18 [1 favorite]

Zompist: Maybe it's not as pretty or predictable as Bohr suggested, but this seems to prove him mostly right.

The piston oscillates- up and down.
posted by gjc at 6:16 PM on September 18

Um, that's a picture of benzene rings, i.e. a complex molecule, not an atom. Nothing to do with the pre-QM models of the atom.
posted by zompist at 6:30 PM on September 18

Pistons were a lousy example, though, sorry. :)
posted by zompist at 6:30 PM on September 18

Sounds like a truism for his particular field and not meant to be extrapolated into academic-level quantum physics, as some seem to be doing here. The fact that he was a mechanic and not a professor of quantum physics is the tip-off for me.

It sounds reasonable when talking about car parts breaking, as long as you are not counting parts that break due to heat, friction, and chemical corrosion.

IANAM.
posted by cj_ at 8:00 PM on September 18

Well, there are some obvious exception to this as a hard-and-fast rule:

1. A bullet fired from a gun
2. Any object falling after being dropped

...but he was probably generalizing about machines, not about physics, so for his frame of reference it makes perfect sense.
posted by mmoncur at 9:59 PM on September 18

A bullet oscillates, but very slowly and only for half of a cycle before it hits the ground. (Or less if it hits a target.) But that's gravity, so maybe not exactly.

Now, if you fired a bullet in space, I don't know. The object has an inherent resonance, I don't know if it would oscillate at that frequency or not.



(Benzene rings- right, but we can see the electron cloud behaving mostly how he predicted. The pretty orbits and orderly valence scheme is more of a tool to understand than it is a reflection of reality.)
posted by gjc at 7:46 AM on September 19

Sounds like a truism for his particular field and not meant to be extrapolated into academic-level quantum physics

...so it doesn't sound like any principle that he read in a science text, I guess.

I wondered just how far it could be extrapolated because I later was reading an introductory astronomy book about how an object on a trajectory is actually "falling" towards any nearby gravitational fields (ie. a bullet fired from gun is falling towards the earth, it's path being part of an ellipse, which could be seen as a type of rotation or oscillation)
posted by bonobothegreat at 8:57 AM on September 19

I guess if you believe that the universe will eventually stop expanding and start collapsing in on itself, one day shrinking to nothing, then in a sense every motion (even acceleration) is either part of that overall oscillation from big bang to big crunch or rotation around the universe's centre of mass.

As far as I know the current belief is that the universe will continue to expand indefinitely, but maybe your saying was first said when it was seen as more likely that the expansion would not be infinite.
posted by A Thousand Baited Hooks at 5:08 PM on September 19