Reporting Universal Truths
Usually, when reporting what someone said in the past, you shift the verb tense backwards in Portuguese (for example, changing a present tense statement into the imperfect). However, there is a major exception to this rule: universal truths and persisting realities.
If you are reporting a scientific fact, a geographic absolute, or something that is still undeniably true right now, the verb in the reported clause stays in the present tense. This applies even if the introductory verb (like afirmou or explicou) is in the past tense.
| The teacher stated that the globe spins on its axis. | O professor afirmou que o globo gira no seu eixo. |
| The student explained that the equator separates the north hemisphere from the south hemisphere. | O aluno explicou que o equador separa o hemisfério norte do hemisfério sul. |
Geographic Facts and Coordinates
This exception is perfectly suited for talking about geography, maps, and coordinates, as these are permanent facts. Notice how the introductory verbs are in the past tense (li, afirmou), but the facts themselves remain anchored in the present.
| I read that the pole's latitude is the highest of the globe. | Eu li que a latitude do polo é a mais alta do globo. |
| The guide stated that this meridian indicates the longitude of zero degrees. | O guia afirmou que este meridiano indica a longitude de zero graus. |
Persisting Realities
This lack of backshifting applies to any persisting reality, such as the mechanics of the globe or how map coordinates function. Because the information is just as true today as it was when the person originally said or discovered it, the present tense remains correct.
| We saw that the geographical pole is located in the ocean. | Nós vimos que o polo geográfico fica no oceano. |
| She explained that the rotation of the planet happens along its axis. | Ela explicou que a rotação do planeta acontece pelo seu eixo. |
| The teacher said that the latitude and the longitude give the exact coordinate. | O professor disse que a latitude e a longitude dão a coordenada exata. |
| We read that the rotation of the planet causes the day. | Nós lemos que a rotação do planeta causa o dia. |