Well, I have and here is what I have learned. The standard tracks are 8' 4" apart. Each track or rail is 6 ¼ - 7 5/16 inches high and 7 inches wide. They are 39 or 78 feet long. And, since the trains' wheels must mate up with the track to keep the trains on the tracks, even at their highest speeds, the top of the track has a "crown" which means that is higher in the middle than on the sides. That crown is critical when the train is traveling at high speeds.
However, the friction caused by the wheels travel over the rails, especially at high speeds, causes the crown to wear down over time. Usually it takes a few years, but, eventually, the crown begins to "flatten" and is no longer safe for travel and must be replaced.
That is bad news because new rail is expensive. The good news is that the worn out rail isn't worthless as one may imagine. Of course, it could be sold a scrap metal for recycling, but it turns out that there is a market for used rails even though their crowns have been worn down.
Who would want them? My brother-in-law is retired from A&K Railroad, the largest U.S. railroad company, and his job was to sell used tracks and switching equipment to companies in 3rd world countries whose factories were near railroads. They needed "sidings", or short-distance tracks, that could be used to transport their products to the main track for shipment. Since those distances were relatively short and the trains would travel slowly, the used track works just fine. Hence, the market for used track.
The next time you ride a train, say to Chicago to shop on the Miracle Mile, think about the rails upon which you train is moving and take comfort in their design.