I guess I'm assuming we'd be able to magically communicate across languages. If we can only speak in languages I know and they knew when they were alive then the right answers are 15th to 18th century scientists.

But why would you ever pick someone who has hours of video in which they explain their perspective on a variety of things? Why would you pick someone alive who you probably could meet if you tried hard enough?

Even picking someone who is 100% an actual historical figure seems like a vague mistake. Why not Moses or Pythagoras?