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October 19, 2011

How do woodpeckers not get concussions or launch their eyeballs out of their heads?

Esther Inglis-Arkell has the answers for you. They involve a different kind of brain cushion, strong neck muscles, and an extra eyelid that acts as a seatbelt for the eyeballs. The eyelid seatbelt, and what it means for you
. . . In 2006, ornithologists Ivan R. Schwab and Philip May set out to study the apparently unbreakable heads of woodpeckers. These birds hammer their beaks into tree trunks searching for insects about, with about 500 strikes a day being typical. During the mating season, when males want to show off their, ah, drilling skills, they will slam their heads into a tree about 12,000 times a day. Each slam has a deceleration force of about 1200 g. A human will concuss themselves at 100 g. How does the woodpecker do it? Mostly, it seems, by going against what most people assume about concussion prevention. Humans have hard heads, supposedly to ward off shocks, and a layer of fluid around the brain, supposedly to cushion it. Although humans do benefit from their hard skulls and the fluid, the woodpecker takes a different approach. It has a spongy skull that surrounds the brain neatly, with no fluid cushion. The brain can't splash around, moving freely through fluid if the hit is hard enough, the way it can with humans. The bird has a softer beak than would probably be expected, and strong neck muscles that engage to absorb the shock of the blow. But the woodpecker can't just protect its brain. It has to add a layer of protection for other organs in its head. While most of the structures are tough (the woodpecker's tongue is more a tactical tool than a sensitive organ), there is the perpetually vulnerable eyeball to worry about. It is half inside the head, half exposed to the world, and that can lead to big problems. To stave these off, the woodpecker has a third eyelid, which slams down in front of the eyeballs just before the bird strikes the wood. These eyelids function as seatbelts, keeping the eyes from popping out of its skull from the sheer force of deceleration. (I didn't know eyeballs could do this, and I now want another eyelid to make sure this never ever happens to me.) . . .

October 16, 2011

Faster-than-light neutrino problem solved with Special Relativity

Faster-than-light neutrino puzzle claimed solved by special relativity | KurzweilAI
The relativistic motion of clocks on board GPS satellites exactly accounts for the superluminal effect in the OPERA experiment, says physicist Ronald van Elburg at the University of Groningen in the Netherlands, The Physics arXiv Blog reports. “From the perspective of the clock, the detector is moving towards the source and consequently the distance travelled by the particles as observed from the clock is shorter,” says van Elburg. By this he means shorter than the distance measured in the reference frame on the ground. The OPERA team overlooks this because it assumes the clocks are on the ground not in orbit. Van Elburg calculates that it should cause the neutrinos to arrive 32 nanoseconds early. But this must be doubled because the same error occurs at each end of the experiment. So the total correction is 64 nanoseconds, almost exactly what the OPERA team observed.

Did Columbus cause the Little Ice Age?

Did Columbus Cause Europe's Little Ice Age? | Informed Comment
This story is irresistible for a world historian interested in climate change. Richard Nevle, a geochemist at Stanford, argues that the European advent in the New World, which killed 90% of the 80 million native Americans, caused the Little Ice Age. The native peoples of the New World burned a lot of wood. When they largely didn’t exist anymore, because they suffered high mortality from a host of European diseases to which they had no immunity, they stopped putting carbon dioxide in the atmosphere. Instead, forests grew rapidly since they weren’t being chopped down anymore, and land wasn’t being cleared for agriculture. Forests take in carbon dioxide and exhale oxygen, plus they fix some carbon dioxide in the soil. They are what is called a “carbon sink,” though not a really efficient one, since much of the carbon they take out of the atmosphere eventually finds its way back there. I suspect the dramatic fall-off in the burning of fossil fuels was the much more important cause here. Less carbon dioxide in the atmosphere reduces the ‘greenhouse effect’ whereby the atmosphere traps heat generated by sunlight and interferes with it radiating back out into space. Mars is so cold because it has a very thin atmosphere and almost no greenhouse effect. But if you get too much carbon dioxide in the atmosphere, it traps quite a lot of heat, and you get Venus, where lead runs in molten streams on the surface. The current dumping of massive amounts of carbon dioxide into the atmosphere by industrial nations is taking us toward the Venus scenario if it remains unchecked. . . .