Sunday, June 07, 2020

Back To Our Starting Point

If you traveled in a straight line for far enough, would you come back to where you started?

Ethan Siegel
Ethan Siegel
May 26 · 8 min read
If you were to set out on a journey from anywhere on Earth’s surface, and traveled in a straight line for far enough, you’d eventually wind up right back where your journey began. After traversing approximately 40,000 kilometers (25,000 miles) — crossing mountains, oceans, deserts, etc. — you’d have completed one entire journey around the surface of our planet. The eventual destination you’d arrive at would be unambiguous: it’s the same as your starting point.
Could it work the same way in space? If you got into a starship, set off in one direction, and traveled as far as you liked, would you eventually return to your starting point? It’s a fascinating question to explore. Even though all signs seem to point towards “probably not,” there are actually two ways that the answer might turn out to be yes, after all.

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