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0 pointschriswarbo11y ago0 comments

> In a fluid, we have vortices... because they allow material and energy to be moved much more efficiently than any of the other structures we don't tend to see in stable systems.

As a Physicist, I am wary of making such statements since they put the cart before the horse ( http://en.wikipedia.org/wiki/Teleology ). I'd be more comfortable saying "In a fluid, we have vortices... as a consequence of the movement of material and energy."

In your case I'm assuming it's just a turn of phrase, but there are some hypotheses which actually attribute abstract "goals" to nature, without providing any explanation in terms of mechanical processes; for example http://www.lawofmaximumentropyproduction.com

In constrast, Darwin explained the theory of evolution using the mechanical process of natural selection. The principle of least action can be explained either physically, using quantum interference (eg. in optics), or mathematically, due to the mixture of inductive steps with deductive ones.

In constrast, the existence of vortices in fluids because of their efficiency would be like claiming crater lakes can't exist because water flows downhill.

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blueprint11y ago

Electrostatic forces keep the surface of a liquid as taut as they can. Undisturbed, and notwithstanding internal vibrations, a spherical droplet of liquid will tend to stay in a sphere because not to do so would require an additional expenditure of energy, that is, in order to counteract those electrostatic forces. So the way I used the term efficient before is in the same way as how it's less costly in energy expenditure, i.e. more efficient, for a droplet to stay spherical. It's the same reasoning behind a number of other things we find in physics. So I'm not convinced that my statement about efficiency leading to appearance of natural structures is incorrect -- maybe more so a difference in how such an observation is commonly phrased.

chriswarboOP11y ago

I was only commenting on the goal-attributing phrasing you'd used, not the Physics.

Compare your electrostatic sphere example to my crater-lake example: lakes at a high gravitational potential are inefficient, it's less costly for the water to flow up the sides of a crater and down into the ocean. The reason that doesn't happen is because there is no mechanism for it to do so. If we look at liquid helium, there is a mechanism which allows it (the Onnes Effect) so it does happen.

> Electrostatic forces keep the surface of a liquid as taut as they can

Yes, but the interesting part of the sentence is "as they can"; we can't just assume that a liquid's surface will be at minimal energy, since that would allow us to solve NP-complete problems with soap bubbles ( www.scottaaronson.com/papers/npcomplete.pdf ) :)

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