Monday, August 24, 2009

Sand and imagination

Here is a review from last week's Nature of a fascinating book about sand (yes - sand!): Sand - A journey through science and imagination by geologist Michael Welland (its American title is a bit bland: Sand: The never-ending story) Apart from the regular bit about the physics of sand etc. this is the bit that caught my attention:
Welland asks how sand grains have helped humans to conceive the Universe and the infinite. He begins with Archimedes who, in the third century BC, calculated that 1063 grains of sand would fill the Universe to the outermost sphere of the fixed stars.
Now this is pretty cool - though we now know that the universe is a waaaaay bigger than that. But, of course, this provides me with a perfect excuse to bring Sagan's Cosmos in:
A handful of sand contains about 10,000 grains, more than the number of stars we can see with the naked eye on a clear night. But the number of stars we can see is only the tiniest fraction of the number of stars that are. What we see at night is the merest smattering of the nearest stars. Meanwhile the Cosmos is rich beyond measure: the total number of stars in the universe is greater than all the grains of sand on all the beaches of the planet Earth.
(check here for more specific sand grains - star numbers estimates. Apparently the two are close in the observable universe. Oh and a handful of sand actually contains 100,000 grains).

Ok - back to the book - which apparently lives up to its bit about imagination:

A personal epilogue provides the reader with a genuine mystery. In 1922, the discovery of Tutankhamun's tomb in Egypt yielded a famous necklace with a scarab beetle carved from a glowing, yellow-green, gem-like material, which its discoverer Howard Carter did not recognize. In the 1990s, the material was shown to be a unique silica glass, 28 million years old and 98% pure, from a particular part of the Libyan desert.

Welland travels to this desolate spot and cherishes the glassy samples he finds glittering on the dunes. But, he muses, what could have produced heat that was intense enough to fuse silica? A strike from a meteorite or lightning can be ruled out because of the lack of visible impact craters or hollow fulgurite tubes, respectively. He speculates that the cause might have been an air burst from the impact of an asteroid with the atmosphere, similar to that at Tunguska in Siberia, Russia, in 1908.
This is fascinating. Even if it turns out to be wrong, I like the out of box thinking here.

With irresistible ideas such as this, Welland provides an appealing blend of science and the imagination, worthy of the famous vision of the poet William Blake: "To see a world in a grain of sand".

Very cool.


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