Thursday, September 26, 2002

A Matter of Scale

I recently read a beautiful little piece on Biological Scaling.

Your average cat weighs about 100 times more than your average mouse. It also lives 100 to the 1/4 power, or roughly 3 times as long. Curiously, this same power ratio equation applies for most species. It's one example of biological scaling.

There is a wide variety of scaling relationships:

Metabolic rate to body mass - scales to the ¾ power
Animal size, to number of species – scales to the ¼ power.
Mass to strength - scales to the 2/3 power (which explains why an ant can carry twigs many times their body weight, yet a man can lift only a few hundred pounds).
Population density, average number of offspring, the time until reproduction – ALL scale to body mass, to the ¾ power.

Clearly, something fundamental is going on here. But what? Why do these relationships exist? Scaling relationships even show up between plants and animals.

‘It’s something to do with…. metabolism.’ For decades, that was basically as far as the biologists could take it. However not too long ago, two rather clever biologists realized ‘hey, a physicist might know more about discovering core fundamentals. We’re good at seeing and interpreting diversity, life. Lets team up and see what we can figure out together.’

Sure enough, together they came up with some answers. And yes, it did have ‘something’ to do with metabolism. But at its core, it had more to do with the nature of circulatory systems. There, the physics and mathematics of fractal networks was seen to apply.
Elegantly.

What I personally think is wonderful about this is - fractal networks have chaos as a fundamental attribute.

From chaos, order. From randomness, life. From uncertainty, elegance.
All part of theoretical physics current embracement of…paradox.

It's 10 o'clock. Do you know where your Zen master is?

Post script:

Did you know all animal species use up roughly the same number of heartbeats in a lifetime?
Regardless of average lifespan?
It’s true – about 1 billion beats.
It's tied to the above metabolic rate/body mass scaling symmetry.
Kool? no?

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