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Weird Stuff
Mon May 09, 2005
Listen in RealAudio 
Hi, I’m Bryan Yeaton, and this is The Weather Notebook.
Now, if you have ever looked up at the sky (and if you haven’t, you really should try it!), you have probably at sometime seen a halo around the moon or the sun. And by halo, we think of a big circular ring. According to physics as we understand it, this circle is the only form such haloes can take. However, there are several documented cases of definitely non-circular haloes.
Most of these form ellipses rather than circles, like the one seen on the SS Brisbane in 1958. The axis of this halo, viewed over the North Atlantic, was around 40 degrees by 30 degrees from the moon, with the long axis perpendicular to the horizon.
A small, teardrop-shaped halo was seen from the MV Patroclus, cruising to the Canal Zone in 1976. It lasted for about 20 minutes before resolving into a more standard 14 degree halo.
There are theories as to why some haloes choose a somewhat different career than their siblings, such as differently-shaped crystals at different levels of the atmosphere, or perhaps an apparent squeezing caused by different temperature gradients. However, most of these aberrant optics are seen well above the horizon, which makes this less plausible.
Sometimes, we can just shake our heads at what we see. On January 21, 1913, an observer on the deck of the RMS Balmoral Castle spotted a dull yellow halo around the moon. Well, maybe halo isn’t the right word: it was square with sharply defined corners, and it lasted throughout the entire night. As science writer William Corliss put it: “There is nothing in meteorological optics that can account for such a strange apparition.
The Weather Notebook is online at www.weathernotebook.org. We are squarely funded by Subaru of America.
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