system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5:How were modern day scholars able to translate works written in archaic English (e.g. The Canterbury tales) so accurately when the language used is so different from the English today?
gpt
You have a lot of texts written in Old English, Middle English, Early Modern English, Victorian English, etc., so you can trace the evolution of the language and backtrack. By now, Old English is an easy language to learn since we know so much about it. 

Things that help:

* Having the same text in multiple periods (the Bible)

* Having translations of earlier texts done in different times (English doesn't rely on this as much, but for example we know a lot about Japanese and its evolution thanks to people adapting Genji Monogatari every 50 years or so starting the 12th century)

* Having repetitive texts drawn out over the centuries (census data, tax books, etc.)

* Having a fairly straightforward evolution that you can explain using historical context (Sudden French loanwords? Go figure, it was after France became a cool place. Sudden Latin influence? Go figure, it was around the time that the church had a say in written language)

* Having a lot of text to work with

You can also figure out pronounciation based on linguistic analysis and old songs which use rhymes (Ever notice that Shakespeare sometimes randomly doesn't rhyme? That's recorded language change right there, and you can figure out the pronunciation of old words based on the fact that, in Shakespeare's time, they used to rhyme)

It's harder with languages that don't have as much data to work with, but fortunately English started writing down things pretty early.