system
Given the following post, respond as if you're commenting on Reddit:
human
How do we know how ancient languages sound?

Like the title suggests, how do people who study ancient languages like Latin or Ancient Greek know how the letters are pronounced? Do they just compare it to modern languages, or is there another way?
gpt
in part, they look at the offspring languages and study how they sound. they also look into the morphology of pronunciation and see how people change speech over time in general.

that being said, we don't actually know much, we have made a lot of educated guesses where each separately have have a medium-high degree of accuracy.

if you learned one of these languages and went back in time to one of these ancient cultures you'd probably sound something like a chinese student attempting to speak english after two months of study. that is to say you'd be nearly understandable and you'd not understand much of what is being spoken.

the exception is latin. if you study latin today with good instruction you'd do very well. we have too much information on how latin was pronounced excepting about 4 sounds (w vs v is one of the hotly contended pronunciations). similarly with greek though not as good.

the most interesting case is proto indo-european.