Second Life is very much like a slowly dying star. It's not as active and engaging as it used to be, but for a 12-year-old game, it's still active enough to be worth keeping the lights on, with 900,000 monthly active users, according to Linden Lab CEO Ebbe Altberg. And much like a slow-dying star, it's huge.
This video, made by YouTube user Luca Grabacr, dives into some of the numbers to show just how big the game is in real-world measurements. Second Life has 25,029 regions, each of which has 65,536 square meters of space (that's the highest 16-bit integer, by the way: 2^16). That area in total covers 1,640.3 square kilometers of space, which is about 1019 square miles, which would take over 23 days walking to cover, assuming Second Life avatars walk 3.2 meters per second.
Luca Grabacr said these statistics were pulled from publicly available information, and they seem accurate based on what Linden Lab has said about the size of Second Life. We sent the video to the company for confirmation and will update when they respond.
If these numbers are correct, it would take some 23 days of walking to get from end to end if all the regions were laid flat. As you can imagine, that pales in comparison to the Earth's girth, which measures 24,901 miles. To walk around the Earth, assuming it's all flat land and you're walking non-stop at an average 3 mph, it would take about 345 days.
Still, for an in-game world that's not Minecraft, Second Life is fairly huge for a mostly settled, mostly player-created universe.