Evening the score
When Ai, mother of the chimp Amuyu, whose mental feats you reported in "Chimp Champ: Ape aces memory test, outscores people" (SN: 12/8/07, p. 355), appeared in a television documentary a few years ago, I reproduced for myself the number-sequence test she performed and found that, after practice, I could easily outperform her. After reading about Amuyu, I tried the number-recall tests that he and the Kyoto students did. With five digits exposed for 210 milliseconds, I had about a 70 percent success rate—not quite as well as Amuyu, but better than the students. I conclude that conditioning plays a large role in performance.
Merlijn van Veen
Westervoort, The Netherlands
In "North by Northwest" (SN: 12/22 & 29/07, p. 392), I believe that the term declination was used in error. On any nautical navigation chart the difference between magnetic and true north is called "variation." Declination has always been the angle from the horizon to a point higher into the sky.
King and Queen Court House, Va.
While navigators use the term variation to avoid confusion with declination (which indeed has astronomical meanings), some groups of geologists use declination to describe the angle between true north and magnetic north.—Sid Perkins
The article might have noted that compasses are used for aligning photovoltaic modules and solar-heating panels. If the actual declination at time of placement is not correctly implemented, the output of these valuable renewable-energy resources is negatively impacted.
The statement that the North Celestial Pole "lies within 0.5° of Polaris" is incorrect, at least at this time. In 2008 the angular separation is closer to 42 arcminutes, and it will be after 2060 before the separation is under 30 arcminutes (0.5°).
Polaris, the North Star, is almost, but not quite, within 0.5° of the Earth's rotational axis, as we reported. The separation between the two actually is 42 arcminutes, or 0.7°.—S.P.