[SciShow intro plays]

Hank: Have you been seeing what I’ve been seeing? Like, people walking down the street, staring at their phones... and then stopping, turning around, and going back in the other direction? Or maybe you’ve seen someone suddenly stop in their tracks and fumble with their coffee while they awkwardly try to swipe at something on their screen.

If you’ve been seeing signs like these, then you’ve been seeing people playing Pokémon GO. Or maybe you’ve been one of them like I have been. For those of you who haven’t been consumed by this game yet, a big part of it involves trying to catch as many types of Pokémon as you can.

If you know anything about Pokémon, you know that’s what it’s all about. Literally, ‘gotta catch ‘em all!’ Pokémon appear in different places, and you can catch them by throwing Pokéballs at them. And there’s places, called PokéStops, where you can collect special items, like more balls. You can also battle other players’ Pokémon for control of another type of special location, called PokéGyms.

But here’s the thing: All of those characters, and places, and objects I just mentioned aren’t just features inside the game itself. The reason people are walking into lampposts and spilling their coffee on sidewalks everywhere is that players can interact with those things in the real world! The world where, presumably, you are now! So what makes Pokemon GO... go? Technology does.

Specifically, developers have combined at least three different technologies in a unique way to integrate the game’s characters and objects into our environment. The first key to the tech of Pokemon GO is everyday GPS. Pretty much all of the game is based on your location -- which the game keeps track of using the Global Positioning System.

This system pinpoints your location using a receiver inside of your phone, along with a network of 24 different satellites orbiting Earth. These satellites are always sending out signals, broadcasting their exact location. And the receiver inside of your phone picks up the signal from the satellites that are closest to you, and then uses math to figure out where you are relative to those satellites.

The game uses this information to keep track of your location -- which it needs to know in order to figure out things like whether you’re close enough to a Pokémon to catch it. So, that’s how the game knows where you are. But on the ground, there’s another suite of technology that determines where all of the PokéStops, and gyms can be found.

This is the result of data analysis, which has resulted in a geographical database of pretty much every town and city in the world. And it turns out, developers actually did most of this work a few years ago, when they were programming a different game, called Ingress.

Ingress centers around special locations, too, called Portals. And those Portals were originally placed at real-life historic landmarks. So developers had to build databases of historic landmarks all over the world. Then they had to write a program that would sort through all of the landmarks to turn them into Portal locations.

For a while, Ingress players were also able to suggest new locations for Portals. When it came time to program Pokémon GO, the most popular Portal locations -- that is, the ones used most often by players -- became gyms, and the less popular ones became stops. But, as you might’ve heard in the news, there have been a few issues with this, because the databases they used weren’t always up to date. That’s how a family in Massachusetts, for example, ended up with a gym at their house; their house used to be a church — a landmark that would’ve been on the list for Ingress Portals.

And the last bit of tech that makes the game possible is arguably even more awesome: augmented reality, or AR -- when computer generated elements are added to your environment. This is different from virtual reality, which you can experience using something like the HTC Vive or Oculus Rift. Those devices aim to completely replace your environment with a simulation, but augmented reality builds on top of what’s already there.

AR is still a pretty new technology, but Pokemon GO developers have figured out ways to use it, in order to integrate gameplay into the real world. When you go to catch a Pokémon, for example, the camera on your phone turns on. The game uses the camera to analyze the space around you, and place a sort of projection of the Pokémon in the environment you can see on your screen. Even if you move around a little-- mostly side to side, not like back and forth-- the game compensates, so that the Pokémon stays in the same spot within your environment.

So if you see a Spearow sitting at the base of a tree, it’ll stay at the base of the tree even if you look away from the tree and then come back. It’s still there! It’s- It’s like it’s in the real world and your phone is a portal into this magical land where pocket monsters live! Gym battles also use augmented reality, making it look like the Pokémon are battling on the ground next to you. So it’s this special combination of location-tracking, data analysis, and augmented reality that lets you chase after Pokémon in the real world. And now, if you’ll excuse me, I saw that there was a Vaporeon in my neighborhood earlier, so I must go.

Thank you for watching this episode of SciShow, which is brought to you by The Great Courses Plus, where you can get unlimited access to over 7,000 different video lectures taught by award-winning professors from the Ivy League and other top schools around the world about anything that interests you... science, literature, even How Great Science Fiction Works, like the video from Dr. Gary K. Wolfe of University of Chicago called Science Fiction in the 21st Century. Right now, The Great Courses Plus is offering SciShow viewers a free one-month trial. Go to thegreatcoursesplus.com/scishow, to have access to the 7,000-video lecture library, or click on the link in the description below.