Breakdown of Ela explicou que a rotação do planeta acontece pelo seu eixo.
ela
she
de
of / from / by (means of transport) / wearing (attire)
por
through / by / for / because of
explicar
to explain
Questions & Answers about Ela explicou que a rotação do planeta acontece pelo seu eixo.
Why is acontece in the present tense when the first verb, explicou, is in the past?
This is the exact exception you are learning in this lesson! Usually, a past tense reporting verb like explicou forces the reported verb to step back into the past too (which would be the imperfect acontecia). But because the planet's rotation is a universal scientific truth, this backshift is skipped. We keep acontece in the present tense because it remains an absolute fact today.
Why does the sentence use pelo (por + o) instead of no (em + o) to mean "on its axis"?
While English uses "on" for an axis, Portuguese uses the preposition por (which combines with the article o to make pelo). Por is the go-to preposition for describing movement along, through, or around a pathway or physical reference point.
Could I say pelo eixo dele instead of pelo seu eixo for "its axis"?
Yes, you absolutely could. In everyday speech, Portuguese speakers often prefer dele or dela to avoid the ambiguity of seu (which can mean his, hers, its, or your). However, seu works perfectly in this sentence because the context is highly specific and it clearly points back to the planet.