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Hurricanes
[Also see: Weather, and fog in a bottle] The year 2005 had the most extreme hurricane season on record, with Katrina devatating New Orleans, and the National Hurrican Center running out of names, the first hurricane in history hitting Spain and Portugal, and hurricane Epsilon still active past the official end of the hurricane season. Naturally there were some questions about hurricanes.
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How does the VLA work?
The Very Large Array is located not too far from here (on Google Earth go to 34°04'32.85"N 107°36'35.83"W), so I was asked about it. Besides explaining simple parabolic mirrors, I wanted to make 2 points: 1) why are they so big, and 2) why do you chain them together? 
I made a parabolic shape out of a piece of aluminum flashing (30x12 cm or so), and some cardboard. You can see a cork in the focal point. Off to the right out of the picture is a lamp (same one I used for the soap bubbles). You can see the light rays converging and lighting up the cork. In addition, I had a laser pointer, you can also see the reflected laser light. All the light that fall on the mirror gets collected in the focal point, and that
Links:
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February 98: Where do all the animals come from?
Time for a break from all the space stuff. There had been some
other vague questions about animals and plants, so here was an
opportunity to talk about evolution, one of the great pillars of science
that the kids should be familiar with. I decided to make up a game that could be played in class that would show evolutionary pressure, drift, divergence and all that good stuff. Here is how it went: First I set the scene: We have a small green valley, with brush, trees and grass, all drawn on the board, and we are going to play at being these medium-sized herbivores. They live for 4 years, then they die.
In the next phase, we're going to throw in some random variation. In addition to the age-cards, I had made up 14 simple tape measures
Then evolutionary pressure strikes: the climate in our little valley changes, and it turns into a a plain with a little grass and trees, but no more brush. There is not enough food for the medium-sized brush eaters, and they die off. The taller animals get to munch on the trees, and a few of the smallest animals get to survive on the grass. After a few rounds/years/generations it becomes clear that we now have two different types of animals where we started with one type. Just throwing the dice and some environmental pressure led to emergence of new species. That's just about all we got done in one hour. The next week, I reviewed the game, and put the proper names to various things we had done. While we were playing the game the week before, I had had no time to introduce the terminology ('evolution', 'survival of the fittest' etc.), or any of the names (Darwin, Wallace). By coincidence, I had just received the Feb 98 issue of Scientific American, in which there was an article about the emergence of antibiotic resistance - a prime example of evolution in real-time action in our world, and I used that to stress that evolution is not just a thing of the past. Also, that under current circumstances, that the human race can no longer evolve. Of course, while we were on the subject, I had to mention DNA,
stepping down in scale from my fingertip to cells, then nuclei and
finally DNA. I had made up some new covers for a set of paperback books
of various thicknesses, a fat one titled 'How to make a Person', an
equally thick volume 'How to make a Monkey', a thinner one 'How to make
a Frog, and a single sheet titled 'How to make Bacteria'. These codebooks
are supposed to be written with only the letters C,G,T and A. Another
important point about these codebooks is that they contain many almost
identical chapters and pages between them, even between the 'Person' code
and the 'Bacteria' code. (Feb 16 98)
Finally, a collection
of related links:
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← 
The second thing to explain is why hurricanes rotate in the first place, and why
they go counterclockwise in the Northern Hemispere and clockwise in the Southern
hemispere. For this purpose I made a flat rotating earth (hey, if Intelligent
Design can be
called 'science', I can claim that the earth is flat), so that I could show
that a rolling ball on a rotating disk does not follow a straight ground path,
but curves to the right in the Northern hemisphere.
