Sometimes errors in articles inspire great mental images. For example, this Nature News article describes a pair of satellites that orbit "several hundred metres from Earth." If I worked on an upper floor of the Sears Tower I might apply for relocation right about now. I picture Doc Edgerton’s famous bullet-through-the-apple photo, with glass instead of pulp. (Satellites in low Earth orbit go about 18,000 mph, 10 times faster than Doc’s bullet.)
The gaff resembles an announcement I’ve rehearsed in my head for many years: "We’ve now reached our cruising altitude of 20 feet." The question that plagues me is: What altitude in that scenario produces the greatest comedic effect? For now, I’ve settled on 20 feet. (9/11 has rendered the absurdity much darker, but I retain the right to muse innocently. I don’t go beyond cutting off treetops in my imaginary thrill ride.)
For the record, the two satellites mentioned in the Nature News article orbit at 300-500 kilometers (not meters.) They are part of a NASA program called GRACE (Gravity Recovery and Climate Experiment.) GRACE’s most recently published findings reveal that Antarctica is melting. The sat duo can measure the distribution of Earth’s mass by comparing subtle changes in their orbital speeds as they fly over. Mapping the results onto a globe and amplifying the results produces pictures of a lumpy Earth like these.
One might call the technique terrestrial phrenology. A shrinking bump on the bottom means an unstable Gaia. Apparently Mother Earth has more than just seasonal affective disorder.
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