grammaticality - "He didn't know where New Jersey was"

I know the past tense carries the past tense in every dependent clause, but referring specifically to places or to things that are eternal, like the Earth, seems a bit weird and therefore we sometimes (I believe incorrectly) say

He didn't know that New Jersey was actually on the East Coast.

Because it still is. Or

He thought the Earth was round.

So is it square now?

Logically speaking, would you consider the use of past tense here a bit confusing in a day-to-day speech in these examples? Would you instinctively opt for using the present tense?

Answer

Both tenses are OK, but I believe the past tense is a bit more common: it may be somewhat contrary to logic, but it sounds better. Harmony of tenses (if that's what it's called) is a linguistic phenomenon that is not always very logical.