Commentary Par VIII 13-15

Once again the poet allows us to wonder how the protagonist, especially if he is in fact in the body (see [Par I 99]), manages to penetrate the physical matter of the planets.  (For an analysis of the ways in which Dante's poetry assimilates difficult scientific notions of the necessary physics, see Cornish [Corn.1997.1].)

Ragni (Ragn.1989.2), pp. 137-39, points out that the imperfect tense used in the long opening passage ([Par VIII 1-12]) is now replaced by the past definite as we move from the hazy distant pagan times and into the hard-edged recent experience of the reality of the Christian afterworld beheld by the protagonist.

It is notable that the rising into the next planet on its epicyclical sphere is accomplished in a single tercet.  By comparison, the arrivals in the Moon ([Par II 19-30]) and in Mercury ([Par V 86-99]) both take considerably more poetic space.