Sunday, October 02, 2011

Quote of the Day

J.L. Austin asked, “Where and what exactly is the surface of a cat?”


Cheryl Rofer said...

Let me put on my full nerd suit and attempt a response.

The link quotes a computer scientist who thinks he is thinking like a philosopher and who obviously knows nothing of surface science.

the surface is two-dimensional; it can’t contain any quantity of gold.

That is certainly one definition of surface, familiar to mathematicians. For whatever it may be worth, that surface is curved through three dimensions, so one may ask whether it is only two-dimensional.

But there is a surface layer of gold atoms, which can be observed by various sorts of microscopy. I have no idea what this means:

We can’t say it’s the outermost layer of gold atoms, for that’s a film with two surfaces.

It's possible that that is a philosopher with no knowledge of chemistry of metals speaking.

So one might treat the question about the cat as worthless, coming after two apparently brainless statements.

But, by the conventions of surface science (and all answers to this question will depend on the conventions of something-or-other), the surface of a cat consists of the outermost atoms of nose, fur, skin, and everything exposed to the outside.

Where this definition will get tricky is that every organism with a digestive tract is in face topologically equivalent to a donut, and the digestive tract is exposed to the outside as well. You may include the surface of the digestive tract as surface according to your preferences.

Or, according to cat conventions, the surface is what you are allowed to pet and scratch. This varies somewhat among cats.

And another question: why always cats?

Anonymous said...

*&*^&%%. I left a long thoughtful and authoritative comment which is gone now. In short, the material surface is electrons, and it's exact position is a quantum mechanical probability, which has to do with the thing approaching it. See Rutherford's exceptional revolutionary gold foil experiment by which a nucleus was touched for the first time. Molecular modellers calculate surfaces all the time--typically based on where the electrons of water molecule are, say, 98% likely to run into the electrons of the enzyme or other molecule whose surface is being calculated. Ditto for cats. (MT)

Anonymous said...

Note it's the same issue for maps and coastlines, which are quasi-fractal.

Anonymous said...

"its exact position" not "it's" duh

Anonymous said...

I'm talking about surfaces in terms of what is optimally physically possible, for instance by quantum tunneling microscope. For ships and coastlines, cats and hands, there's a coarser scale we're interested in, which muddles the matter. A cat's skin is part of its surface if you're probing with a needle, but not if you're petting with your hand, hairless cats notwithstanding. Is this a philosophical question or just a way to wind up the people who know some science?