[ep29/en] Improve initial translation

I tried to keep the changes as minimal as possible to prevent conflicts, since I'm sure Craig is already hard at work on his version 😉 I only found very few things I feel confident enough to improve, I'll leave the instances where it's a bit more tricky to make it sound natural to Craig's judgement.

Notable changes:

• Using the common way of writing light-years
• Preferring double quotes (") over single ones (') like it's usually done in American writing
• Making a few expressions sound a bit more natural