Letter to Astronomy Magazine

I recently sent a letter to Astronomy magazine about one of the articles in the April 2013 issue. The article was titled Astro April Fools and was written by the columnist Bob Berman. I didn't like how lightly Bob treated Y2K, so I wrote the following letter:

I have been a subscriber to Astronomy magazine for about 3 or 4 years, since I was about 12. Probably my favorite part of Astronomy magazine is Bob Berman's Strange Universe. However, in the April 2013 issue, Bob seems to treat Y2K a little too lightly. Although not as bad as advertised, there really were dangers; computers really did fail, and bad things did happen.

Caption:A French sign displaying an inaccurate date because of the Y2K bug.
Image taken from Wikipedia.

Think about a normal computer problem, like the one that happened a few weeks ago: an airline's computers were down for only a couple of hours, but it cost them thousands of dollars. When something like this happens, the computer can be reset; once the bad data is gone, everything goes back to normal. Reseting a computer wouldn't work in the Y2K scenario. The date is the bad data, and restarting the computer doesn't help with that. Instead of computers being down for a couple of hours, they could be down for a couple of days.

Why did so little happen during Y2K, then? The bug was more widely advertised than any other in the history of computing. Software companies received worried phone calls from airliners and many other companies asking about the problem; so realizing the danger, they hired whole teams of programmers to ensure nothing happened when we time-warped.

However, not everybody took action, so some bad things did happen as direct results of Y2K bugs. Down's syndrome test results were inaccurate, resulting in 2 abortions after false positives. Radiation-monitoring equipment in Japan failed. An alarm sounded in a nuclear power plant. Not so bad; but that was after preparation. What would have happened had we ignored it?

Skim a Pond

Last Friday I went skiing at Arapahoe Basin. Yes, there's still snow up there - but the warm weather is melting it, resulting in conditions known as Spring skiing. The water from the melted snow collects in valleys and trenches, forming ponds excellent for skimming.

Skimming is skiing on water. To skim a pond, the upward force from the skis must exceed the skier's weight, and it must continue to exceed his weight until the skier gets across the pond. The force is determined by the skier's forward velocity, the surface area of the bottom of his skis, and the angle of his skis.

On Friday when I visited Arapahoe Basin, I skimmed a few ponds. It's lots of fun, as long as you don't slow down too much halfway through the pond. Here's a video from my trip:

Warm Weather

Finally - it's nice and warm outside. The meadowlarks are singing, and cumulus clouds fill the sky. In some places, this kind of weather has been going on for the past couple of months. Where I live, though, we've been having cool weather, so a 70° day seems very warm.

Here are some of the pictures I took today:

Sprout Jar

Photos of seeds from yesterday, to scale.
The onion is the one on the left.

A couple of days ago I planted 3 seeds in a clear glass jar, so I could watch them germinate. 2 of the seeds came from one of my basil plants, and the other came from a green onion plant. This is partly a test on the quality of my home-grown seeds, but also a fun gardening activity; after all, who wouldn't like to sprout  some seeds and watch them grow?

Here's how you can make your own sprout jar:

Halbach Array

Yesterday I learned about something really cool called a Halbach array. It's a special arrangement of magnets that has a magnetic field on one side, but not the other.

The array and its effect were discovered in 1973 by John C. Mallinson, but it was named after physicist Klaus Halbach, who invented the array 7 years later - not knowing someone else had already gone to the trouble.

Halbach array, showing approximate field lines.

The way the Halbach array works is similar to a bunch of lined up horseshoe magnets. There are North and South poles, but they are all on the same side of the row. Horseshoe magnets are clumsy, so in the Halbach array, regular bar magnets are used instead. The magnets are oriented so that their magnetic fields match those of the horseshoe magnets they're replacing; that way, the effect is nearly the same.

A perfect Halbach array is only magnetic on one side, greatly reducing stray magnetic fields that can interfere with other equipment; and since the magnetic field is all on the same side, it is twice as strong as a regular magnet's field. Because of those properties, Halbach arrays are useful in a variety of applications, including:

• Refrigerator magnets
• Inductrack Maglev train system
• Particle accelerators
• Free electron lasers

Then there's the Halbach cylinder, where the magnetic field is in a bore down the center, and the Halbach sphere, where the magnetic field is in an empty spot inside the sphere. They aren't as simple as the array, so I won't explain them in this post.