Those Numbers at the End of the Runway Have a Hidden Meaning
Have you ever looked out the airplane window on takeoff or landing to spot the big numbers painted on the end of the runway. Yes, they help pilots tell one runway from another, but they also tell them something more.
As Atlas Obscura explains, the numbers that runways have aren't arbitrary. A runway always has a number between 1 and 36, and that number isn't just the runway's nickname, but also indicates how many degrees away that runway is from magnetic north, rounded to the tens. So runway 24 is 240 degrees from magnetic north, and runway 36 runs right along it.
Why? It can be a valuable way to double check where you are. A pilot preparing for takeoff can make sure he's about to head down the right runway by just taking a look at his compass.
The problem is that magnetic north tends to move-at rates of up to 1 degree per year as far north as Alaska-so sometimes you have to get out there and actually change the numbers now and then, and the airports have to repaint. After all, you want all the data you can get when you're coming in for a tough landing.
Source: Atlas Obscura via Digg
