Metastable: Down the block, along the street, is a steep bank on which trees have taken root and grown, slanting off the bank and over the road, balancing their holds in the ground with increasing height and occasional high winds and of course gravity. One day sooner or later a good rain slightly liquifies the soil, the wind catches the leaves and branches, gravity (which always wins) wins again, and a tree drops like a rock. What had seemed stable was not. It was metastable and had been all along.
Physicists have a little hare-brained model explaining this: a curve with a top, then a slanting hill, then flat ground. A ball poised at the top of the curve is potentially full of energy and unstable. It rolls down the hill until it has nowhere left to roll, until it’s at its minimum energy and is stable. And if the top of the hill has a little dimple in it and the ball sits in the dimple, then the ball is metastable. Give that ball a little flick, and all the ball wants to do is drop to its minimum energy and reach stability. Metastability, according to physicists, is a system above its minimum energy but still stable, waiting for something to happen.
So an avalanche doesn’t happen unless somebody yells. A supersaturated solution doesn’t crystallize until a seed crystal falls into it. Finland putatively has lakes so clear they’re below their freezing points and still liquid until someone throws a rock, and the lakes explode into ice. The secret is all in that little flick.
The point is that the trees, the ball in the dimple, the avalanche, the solution, the lakes, none knew they were metastable, they all thought they were stable. As long as I have the energy, I’d just as soon stay unflicked.
Credit:
trees on cliff: Mila Zinkova
cathedral balloon: Bohringer
Well, ‘physicists’ have accidently got it pretty damn right! I am the metaphorical apotheosis of metastability. (And I bet no-one ever put those three words into the same sentence before…)
In fact, I don’t think anyone’s ever written that sentence before either. Good luck maintaining metastability.
Hmm, don’t want to get too heavily into this – but, is it possible that a metastable system actually contains within itself the germ of that flick? Without the need for any outside influence? I read a book about chaos theory years ago, which I think suggested something like that. And of course the behaviour of the global financial markets bears it out, doesn’t it??
This is way above my pay grade, Tim. It makes intuitive sense. But I suspect a physicist might say that the system needs energy added before it jumps out of metastability, and I wouldn’t know how a system could energize itself. Tell you what, if you’re really interested and can wait a few days, let me ask my husband-the-physicist.
Yes please, I’m genuinely interested, if he wants to engage/enlighten me about this stuff. (no maths though please).
Tim, according to my husband the physicist: in theory a metastable system — a ball sitting in a dimple at the top of a hill — could get itself out of the dimple and down the hill to stability only if somehow energy — a flick — got fed into the system externally.
However #1: since everything is at bottom a matter of quantum mechanics in which energy can just pop right out of nothing and anything that’s possible will sooner or later happen, then on the quantum, subatomic level, a metastable system could with some probability jump into a stable state.
However #2: systems in the real world — i.e., not the world of hare-brained physics models — have so many variables, so many things going on, that of course one of those variables– wind, rain, gravity, whatever — could feed energy into the system and whomp, the tree drops.
This is my translation — is it making sense?
Yes! However#1 was what I think I had in mind. Thanks, Ann and husband!