Seeing the Natural World With a Physicist’s Lens
Serge Bloch
By NATALIE ANGIER
Published: November 1, 2010
If you’ve ever stumbled your way through a newly darkened movie theater, unable to distinguish an arm rest from a splayed leg or a draped coat from a child’s head, you may well question some of the design features of the human visual system. Sure, we can see lots of colors during the day, but turn down the lights and, well, did you know that a large bucket of popcorn can accommodate an entire woman’s shoe without tipping over?
Yet for all these apparent flaws, the basic building blocks of human eyesight turn out to be practically perfect. Scientists have learned that the fundamental units of vision, the photoreceptor cells that carpet the retinal tissue of the eye and respond to light, are not just good or great or phabulous at their job. They are not merely exceptionally impressive by the standards of biology, with whatever slop and wiggle room the animate category implies. Photoreceptors operate at the outermost boundary allowed by the laws of physics, which means they are as good as they can be, period. Each one is designed to detect and respond to single photons of light — the smallest possible packages in which light comes wrapped.
“Light is quantized, and you can’t count half a photon,” said William Bialek, a professor of physics and integrative genomics at Princeton University. “This is as far as it goes.”
So while it can take a few minutes to adjust to the dark after being fooled by a flood of artificial light, our eyes can indeed seize the prize, and spot a dim salting of lone photons glittering on the horizon.
Photoreceptors exemplify the principle of optimization, an idea, gaining ever wider traction among researchers, that certain key features of the natural world have been honed by evolution to the highest possible peaks of performance, the legal limits of what Newton, Maxwell, Pauli, Planck et Albert will allow. Scientists have identified and mathematically anatomized an array of cases where optimization has left its fastidious mark, among them the superb efficiency with which bacterial cells will close in on a food source; the precision response in a fruit fly embryo to contouring molecules that help distinguish tail from head; and the way a shark can find its prey by measuring micro-fluxes of electricity in the water a tremulous millionth of a volt strong — which, as Douglas Fields observed in Scientific American, is like detecting an electrical field generated by a standard AA battery “with one pole dipped in the Long Island Sound and the other pole in waters of Jacksonville, Fla.” In each instance, biophysicists have calculated, the system couldn’t get faster, more sensitive or more efficient without first relocating to an alternate universe with alternate physical constants.
The tenets of optimization may even help explain phenomena on a larger scale, like the rubberiness of our reflexes and the basic architecture of our brain.
For Dr. Bialek and other biophysicists, optimization analysis offers the chance to identify general principles in biology that can be encapsulated in an elegant set of equations. They can then use those first principles to make predictions about how other living systems may behave, and even test their predictions in real-life, wetware settings — an exercise that can quickly mount in quantitative complexity for even the seemingly simplest cases.
On Wednesday, Dr. Bialek will discuss his take on biological optimization at the Graduate Center of the City University of New York, in a public lecture fetchingly titled “More Perfect Than We Imagined: A Physicist’s View of Life.” Dr. Bialek is a visiting professor at the graduate school, where he has helped establish an “initiative for the theoretical sciences” devoted to the grand emulsification of mathematics, neuroscience, condensed-matter physics, quantum computation, computational chemistry and the occasional seminar on the physics of mousse and marshmallows.
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Read more here/Leia mais aqui: The New York Times
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William Bialek, professor de Física e Genômica Integrativa na Universidade Princeton
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NOTA DESTE BLOGGER:
Quer saber mais sobre o que é a vida? Não pergunte aos biólogos, pois eles enxergam as formas bióticas com os antolhos darwinianos que os impede de ver a complexidade irredutível dos sistemas biológicos e da informação complexa especificada como o DNA, e não aceitam que essas evidências quebraram o processo evolutivo darwiniano gradualista no contexto de justificação teórica.
A quem perguntar então? Pergunte aos físicos e aos químicos. Eles sabem mais de biologia do que os próprios biólogos, e fazem perguntas fora do paradogma de Down...
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NOTA DESTE BLOGGER:
Quer saber mais sobre o que é a vida? Não pergunte aos biólogos, pois eles enxergam as formas bióticas com os antolhos darwinianos que os impede de ver a complexidade irredutível dos sistemas biológicos e da informação complexa especificada como o DNA, e não aceitam que essas evidências quebraram o processo evolutivo darwiniano gradualista no contexto de justificação teórica.
A quem perguntar então? Pergunte aos físicos e aos químicos. Eles sabem mais de biologia do que os próprios biólogos, e fazem perguntas fora do paradogma de Down...
