Tense agreement?

[Cooliegirly]

I always thought that the verbs in one sentence have to stay constant, but can anyone explain why the following sentences are supposed to be grammartically correct sentences?

"Numerous collections of short stories include works by Isaak Bashevis Singer who, despite living in the United States for more than fifty years, continued to write primarily in Yiddish."

"The ancient concept that states that the sun revolves around Earth was questioned by Copernicus in the sixteenth century."

Why? Why？Why?

[Yankee]

Hi Cooliegirly

There is no grammar rule that I'm aware of stating that all the verbs in one sentence have to be in the same tense. Naturally, that will often be the case, but it simply depends on what you want to talk about.

I think if you take your two sentences apart and turn them into separate, shorter sentences, you can see more easily that the various verb tenses are not only logical but also correct:

[Cooliegirly]

Yes, that helped a lot. Thanks, Amy.