  We analyze Euclidean spheres in higher dimensions and the corresponding orbit
equivalence relations induced by the group of rational rotations from the
viewpoint of descriptive set theory. It turns out that such equivalence
relations are not treeable in dimension greater than $2$. Then we show that the
rotation equivalence relation in dimension $n \geq 5$ is not Borel reducible to
the one in any lower dimension. Our methods combine a cocycle superrigidity
result from the works of Furman and Ioana with the superrigidity theorem for
$S$-arithmetic groups of Margulis. We also apply our techniques to give a
geometric proof of the existence of uncountably many pairwise incomparable
equivalence relations up to Borel reducibility.
