It is a light thing for the shadow to go down. — Because that was the ordinary course of things. As a natural phenomenon, of course, the sudden extension of the shadow would have been as wonderful as its retrogression; but what is in any way a familiar occurrence must needs seem easier than what has never fallen under observation.
To go down. — Rather, to spread. The LXX. has κλῖναι, another use of the Hebrew verb. The Targum, Syriac, and Arabic render “to go forward” (march).