April 11, 2006
Even the most precise clock in the world cannot measure how unlikely your existence really is.
A Sun Halo over Utah
Birthday · April 11, 2006
A little universe, just for you
Your date.
Ready to give.
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APOD published April 11, 2006. Credit: Doug Wilson. A publication-date match, not a photo taken on your date. Independent of NASA.
Have you ever seen a halo around the Sun? This fairly common sight occurs when high thin clouds containing millions of tiny ice crystals cover much of the sky. Each ice crystal acts like a miniature lens. Because most of the crystals have a similar elongated hexagonal shape, light entering one crystal face and exiting through the opposing face refracts 22 degrees, which corresponds to the radius of the Sun Halo. A similar Moon Halo may be visible during the night. The picture was taken in Gunlock, Utah, USA. A flock of birds was caught by chance in the foreground. Exactly how ice-crystals form in clouds remains under investigation. Lecture: APOD editor to give public talk in Princeton tonight (April 11)
Image credit: Doug Wilson