This is the key take away. As a modern human you obviously reason “how they hell could there NOT be vacuum?” , but in those times you had islands of knowledge (

This is the key take away. As a modern human you obviously reason “how they hell could there NOT be vacuum?” , but in those times you had islands of knowledge (no email, mail if you are lucky) and you always reason from what you know at that point. Just like future readers might shake their head “how did they not know warp drives work like this?”