Solution: Number of days it takes Mercury to orbit the sun - NYT Crossword

There’s a gorgeous symmetry here between this entry, whose clue references “days,” and its mirrored entry at 64A. Mercury is the closest planet to the sun, and its year — the amount of time it takes for it to fully orbit the sun — is short, only EIGHTY EIGHT 24-hour cycles. The planet is wildly eccentric in its temperature and speed — hot and fast when near to the sun, frigid and slow when farther away — which helps explain the term “mercurial,” but the rotation of the planet as it whooshes wildly around the sun is extremely (and once immeasurably) slow. This means that a day on Mercury, defined as the time it takes for the Sun to return to the same place in the sky, can be up to twice the length of one of its years. Lots of ramifications for modern science, but the data knocks me out in about six and a half minutes (nighty-night!).