Equinox Disparity

Paul Hewitt's April Figuring Physics column (pp. 198, 214) asks the reader to determine what accounts for the seven- day difference between the 179 days from the autumnal to vernal equinox and the 186 days from the vernal to autumnal equinox. His answer—Earth moves faster during the shorter period—is the only one of the offered choices that conceivably could account for the difference. Alas, it doesn't because it implicitly and incorrectly assumes that the distances traveled during the two periods are the same.