  Krasinsky and Brumberg (2004 Celest. Mech. Dyn. Astron., 90, 267) reported a
secular increase of the astronomical unit (AU) of 15 meters per century.
Recently, Miura et al. (2009, PASJ, 61) proposed that a possible angular
momentum transfer from the rotation of the Sun to the orbital motion of the
solar system planets may explain the observed increase of the AU. They assumed
that the tidal effect between the planets and the Sun is the cause of this
transfer. Here we claim that tidal effect cannot be a cause of this type of the
transfer to explain the increase of the AU.
