How to Solve a Four Dimensional Space Time Problem

In theory, GPS works anywhere if you've got five or more satellites. But the bigger problem is that your GPS device probably won't work. It's trying to locate itself in four dimensional space time - for which it needs five satellites. And there's some regions in space where you're outside the earth. So a GPS can sometimes still work out where you are with only four satellites If you start off by assuming that you're on earth. In reality, you're more likely to be connected to like eight or nine satellites at a time. They all look very close together and so far away from each other they don't show up as being near one another. This makes it easier to pick