No Man's Sky is a game about exploring massive universes on your own. As two players discovered in an ongoing Twitch stream, that means it's not possible for multiple travelers to group up or even meet up, if they ever actually manage to happen across the same planet.
After discovering that a planet he'd landed up had been found by a user called Psytokat, a player by the name of TheGalacticCactus messaged his fellow space traveler to stage a meet-up. Recognizing that that's a rare occurrence in No Man's Sky, with its quintillions of planets, the pair decided to stream their endeavor. It's recommended that you watch their adventures side-by-side on a multi-stream viewer, as doing so emphasizes that, despite Psytokat and TheGalacticCactus' calculated, best efforts, the two never cross paths.
Throughout the stream, viewers have seen the players stand in the same space stations, speak with the same planetary denizens and stop by identical waypoints, only to never actually see each other. Also of note is that one player's planet is experiencing daytime while the other is venturing during the night. It's possible that they're on different servers — but it's also likely that the procedurally generated game is rendering identically named planets in unique ways.
The encounter seems to suggest there's no multiplayer in the game, as lead designer Sean Murray of Hello Games has often said. In a recent tweet, he told players that the chance of seeing one another in-game was "pretty much zero."
The game doesn't require a PlayStation Plus subscription, as Sony and the developer think of it as a single-player experience due to the great improbability of players being able to interact. That's different from what Murray said in 2014, when he told GameSpot that No Man's Sky would feature "traditional" multiplayer elements.
We've reached out to Hello Games about how and why these two players aren't able to connect, and if there's still hope for other No Man's Sky travelers out there to make their journeys any less solitary. In the meantime, check out our FAQ to answer your other questions about what is possible in the game, now on PlayStation 4.
Update: In a series of tweets, Sean Murray reacted to the "mind-blowing" meet-up, suggesting that the unexpected number of people playing at once might have expedited this happening.
"We added a 'scan for other players' in the Galactic Map to try to encourage [players finding each other] happening," he wrote. "We wanted it to happen — but the first day?"
He clarified that all players are sharing a universe, and that could lead to some exciting discoveries — perhaps not actually seeing other players, but finding Easter eggs. But Murray remains concerned that "too many" people are sharing that universe all at once, right after No Man's Sky's launch.
"It is a testament to how amazing our network coders are that Discoveries are still working at all," he wrote. "For instance over night we hit 10 million species discovered in NMS... that's more than has been discovered on earth."