It’s a Bluesky link but he use adult tags as de facto “spoiler” tags. The problem is that content is hidden if you’re not logged into Bluesky. Here’s a Bluesky mirror site to show the entire thread…
https://subium.com/profile/c0nc0rdance.bsky.social/post/3kpkcq2ecws22
A huge hint…
Straight line? That’s a great circle!
(It’s not possible to do it in a straight line on this projection)
((It’s also not possible to do it in real life because you’re tunneling through the planet then, and not really sailing))