Optical Illusions

Thu, 19 Jan 2006 22:01:57 GMT

Michael Bach collected 61 Optical Illusions and Visual Phenomena and provided explanations for most of them. There are many amazing illusions, but I especially liked the one that is shown on the right side of this post.

»Optical illusion« sounds pejorative, as if exposing a malfunction of the visual system. Rather, I view these phenomena as bringing out particular good adaptations of our visual system to standard viewing situations. These adaptations are »hard-wired« into our brains, and thus under some artificial manipulations can cause inappropriate interpretations of the visual scene.

Theory of Animal Locomotion

Tue, 10 Jan 2006 06:05:27 GMT

From the Duke University news release:

A single unifying physics theory can essentially describe how animals of every ilk, from flying insects to fish, get around, researchers at Duke University’s Pratt School of Engineering and Pennsylvania State University have found.

The researchers show that so-called "constructal theory" can explain basic characteristics of locomotion for every creature -- how fast they get from one place to another and how rapidly and forcefully they step, flap or paddle in relation to their mass.

“From simple physics, based only on gravity, density and mass, you can explain within an order of magnitude many features of flying, swimming and running,” added James Marden, professor of biology at Penn State. “It doesn’t matter whether the animal has eight legs, four legs, two, even if it swims with no legs.”

First conceived by Bejan and published in 1996, the constructal law arises from the basic principle that flow systems evolve so as to minimize imperfections – energy wasted to friction or other forms of resistance – such that the least amount of useful energy is lost.

The theory applies to virtually everything that moves, Bejan said. For example, his earlier work has examined how the law explains traffic flows, the cooling of small-scale electronics and river currents

For more information about this theory see the original paper The constructal law of organization in nature: tree-shaped flows and body size.

[via primidi]

Zero Brane

Optical Illusions

Theory of Animal Locomotion