People used to think that the world was/is flat

People used to think that the world was/is flat

Jsou možné obě varianty a nebo pouze was? Google umí najít texty v obou případech… Děkuji

Hi zizak. As a native I would naturally say ‘was’. Is would sound strange.

Google umí najít spoustu nesmyslů. To, že je něco na internetu, znamená pouze fakt, že to někdy někdo napsal.
Zrovna u téhle věty – když použijete “used to”, říkáte, že to tak bývalo, tedy už to není. Když to tak už není, nemůžete použít “is”.

Single sentence, no context . Obě varianty jsou teoreticky možné. “Was” (podle sequence of tenses in reported speech) je vždy správné a určitě lepší. Unfortunately we don't have the wider context, because that would influence the choice.

People used to think the world was flat, but they have been proven wrong . People used to think the world is flat, but they have been proven wrong . People used to think the world is flat, because when we look into the distance we can't see over the horizon . People used to think cancer was untreatable . People used to think cancer is untreatable  .

People used to think the world is flat, because when we look into the distance we can't see over the horizon.

To je opravdu gramaticky správně? Chápu, že takhle lidi občas mluví, ale mně celá ta věta přijde nelogická.

People used to think (in the past) that the world is flat (now) because when we look into the distance (now), we can't see the horizon (now) .  ?

Pochopil bych věty:
People used to think the world was flat, because when they looked into the distance they couldn't see over the horizon.

Some people think the world is flat, because when we look into the distance we can't see over the horizon.

It's ok. English isn't always logical. Although we can't see over the horizon when we look into the distance, we know that the world isn't flat. But that is what people used to think ( – that the world is flat).