In the physical world, a runway is a takeoff strip for airplanes. If you were in charge of designing an airport, you’d have to figure out the ideal runway length that would allow all planes to take off and land safely. How long should your runway be? It turns out 1.25 - 2.5 miles is a typical length. You could save money by building a 1-mile version, but that’s too short to be useful. On the other hand, you could build a 4-mile behemoth, but that would cost a lot more without providing additional benefits.