should we move large dense heavy objects to very high elevations in order to slow the earth's rotation and lengthen the day?
alternatively
should we move large dense heavy objects to very low elevations in order to speed up the earth's rotation and shorten the day?
odds the former, evens the later
dubs we build enormous, nuclear powered funiculars in geographically advantageous locations so that large dense heavy objects can be rapidly cycled between very high and very low elevation in order to create an amusing lurches in the earth's rotation.