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What Makes Spider Webs Tough As Steel
sciencehabit writes "A new analysis reveals the intricacies of spider web design, showing how the unique properties of its silk turn webs into flexible yet strong traps. Computer simulations reveal that heavy forces spread over the entire net rather than stay local. Real spider silk can be either stretchy or stiff at different times, which produces threads that flex and then snap in just the right way to avoid wrecking nearby spokes."
I always thought Dragonforce was the hardest metal known to man.
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Not to deny the amazing properties of spider silk, but the article mentions, "In fact, such self-sacrificing by a unit is highly unusual among natural materials, Buehler notes."
I find this highly inconsistent with biology in general. In the human body, one such system we call skin. As a specific example, callouses are groupings of skin cells which die and harden to protect areas of the hands and feet frequently engaged by stresses, such as shoes and using hand tools (normally skin sloughs off). Continuing just with skin, note the way that even when cleaved, skin puts significant friction against the object cleaving (watch a piercing in slow motion some time). To overcome this, physicians are taught to cut along skin grains, which also reduces scarring.
Other sacrificial organic materials, well tree bark is frequently harder than the material inside. Hair on various animals prevents predators from getting a firm grip. Salamander tails come off once a tension threshold is crossed. Cell membranes flex, usually right up to the point contents would be damaged by the intrusion anyway. Cell walls work like bricks, giving plants firm structure, and making them difficult if not impossible to slice up for electron microscopy (not sure if that barrier has been crossed). Trees and plants lose branches in the wind and tumbleweed completely detaches from its roots. Fruit has skins just strong enough to prevent spoiling several days before being eaten by animals, thus spreading seeds. Seeds and nuts have cleavage lines to make them strong, but allow the bud to break out.
There are many other examples, but functional, purpose built tissues and substances in organic materials are very common.
chemistry is hard
So erm... under what possible conditions can carbon ever change it's atomic structure and chemical behavior to become a metal ? Short of nuclear transmutation - in which case the result is NOT carbon. Please, do explain as I would love to know.
Sure thing.
First, let's go beyond your high-school level description of what a metal is. There is no "specific set of elements" that are metallic. Rather, a metal is something that, owing to delocalized electrons, has no band gap at the Fermi level and thus is a good conductor of electricity and heat. This can be achieved in many elements, not necessarily those that are typically thought of as metals, by using fancy conditions, such as extreme pressures and/or temperatures.
Take, for instance, this report on metallic carbon in Phys. Rev. Lett: http://prl.aps.org/abstract/PRL/v102/i5/e055703
or the infamous metallic hydrogen, http://lt26.iphy.ac.cn/abstract/pdf/B1488.pdf
Every end has half a stick.