Sky Crossings

May 21, 2005


Provided by: Rick Stankiewicz
Summary authors & editors: Jim Foster; Rick Stankiewicz

The above photo showing a geometric contrail design was taken from near Peterborough, Ontatio, Canada on December 3, 2000. Do you remember your geometry; acute angles, complementary angles, parallel lines, congruent segments, proportion? Trans-continental and trans-oceanic flights often use similar Great Circle routes with the result that, from a given ground location, contrails generally occur in similar places in the sky. Sufficient moisture at altitudes greater than about 30,000 ft (9,144 m) enabled these contrails to stretch across nearly the entire sky. Note that the older contrails aren't as "tight" -- have begun to spread out and dissipate.

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