April 03, 2005

The senses, part two

Yesterday's couldn't comprise descriptions of all the senses, and some fun information got left out, which I will write about here.

(Reminds me of a period when I subscribed to one of the Copenhagen newspapers, Berlingske Tidende. They had a standing feature known as The Backside where they printed fictive news and children's puzzles. At the top of the feature they wrote something like this: Have you ever wondered why exactly enough things happen each day to fill up the newspaper? Some of our brighter readers may have realized that this is because we are forced to leave some things out. We have created The Backside to give some of these stories a chance, too. Subscribing to this paper allowed us to compare the quality of the weather forecasting done by the Swedish and Danish meteorological services, since we also were getting Sydsvenska Dagbladet, the south-Sweden daily paper. The Swedish forecasts were almost always wrong and the Danish almost always right. My theory was, why should a state-run agency care what the weather is like in the southernmost province where we live? As long as they get it right for Stockholm, where the politicians live, everything is fine. But Copenhagen is right across the sound, so of course the Danish forecast is better. (Not better weather, but more accurate.) And, since Denmark consists of a long thin peninsula and a lot of islands, I think the Danes are better at forecasts that involve the effects of the ocean.)

OK, back to business. Some animals have senses that humans don't have. First off are the animals that can sense electrical fields: sharks, rays, some fish, and unlikely as it may seem, the platypus. Some of these animals can generate their own electrical fields of hundreds of volts (like the electric eel), which they use for communication and to stun their prey. I was told a story once about a guy who stored his credit cards in an eel-skin wallet, and the magnetic strips all got erased. Urban legend?? I was impressed that one of my students could translate 'platypus' into Danish for me: 'naebdyr', which means 'beak animal'.

Just recently a guy at Caltech discovered that some animals and bacteria can sense magnetic fields. These beneficiaries of millions of years of evolution have a special cell that deposits a crystal of haematite and acts as a tiny compass. Bees and some birds apparently have this sense-- the bees use it to find their way between flowers and hive, and it helps the birds migrate. Nobody has asked the bacteria what they use the sense for.


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