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In economics, there is a term called "path dependence," which is similar to "inertia" in physics. Once a path is chosen (whether "good" or "bad"), one may become dependent on it. The following story about American railroad tracks might help us understand this concept and deepen our impression of its consequences.
The standard distance between two railroad tracks in the United States is 4.85 feet. This is a very strange standard. Where did it come from?
It turns out that this is the British railway standard, because the earliest American railways were designed and built by the British. So why did the British use this standard?
It turns out that the British railways were designed by those who built tram tracks, and this 4.85 feet was the standard used for trams. Where did the tram track standard come from?
It turns out that the first people to build trams were previously carriage makers. And they used the wheel width of carriages as the standard. So why did carriages use this specific wheel distance standard?
Because if carriages at that time used any other wheel spacing, the wheels would quickly be damaged on the old roads of Britain. Why?
Because the ruts on these roads were 4.85 feet wide. Where did these ruts come from?
The answer is that they were set by the ancient Romans. 4.85 feet was the width of Roman chariots. If anyone used a different wheel width on these roads, their wheels would not last long. We ask again: Why did the Romans use 4.85 feet as the wheel spacing for chariots?
The reason is simple: it was the width of the two horses' behinds pulling the chariot. The story should end here, but in fact, it doesn't.
Next time you see the American space shuttle standing majestically on the launch pad on TV, take a closer look. There are two rocket boosters on either side of its fuel tank, provided by a factory in Utah. If possible, the engineers at this factory would like to make these boosters a bit fatter to increase capacity, but they can't. Why?
Because after these boosters are made, they need to be transported by train from the factory to the launch site, passing through some tunnels along the way. The width of these tunnels is only slightly wider than the width of the train tracks. However, we must not forget that the width of the train tracks is determined by the width of a horse's behind.
Therefore, we can assert that the design of perhaps the most advanced transportation system in the world today was determined by the width of two horses' behinds two thousand years ago. This is path dependence, which seems somewhat paradoxical and humorous, but it is a fact.
Origin of U.S. Railroad Gauge
The standard distance between two railroad tracks in the United States is 4.85 feet. This is a very strange standard. Where did it come from?
It turns out that this is the British railway standard, because the earliest American railways were designed and built by the British. So why did the British use this standard?
It turns out that the British railways were designed by those who built tram tracks, and this 4.85 feet was the standard used for trams. Where did the tram track standard come from?
It turns out that the first people to build trams were previously carriage makers. And they used the wheel width of carriages as the standard. So why did carriages use this specific wheel distance standard?
Because if carriages at that time used any other wheel spacing, the wheels would quickly be damaged on the old roads of Britain. Why?
Because the ruts on these roads were 4.85 feet wide. Where did these ruts come from?
The answer is that they were set by the ancient Romans. 4.85 feet was the width of Roman chariots. If anyone used a different wheel width on these roads, their wheels would not last long. We ask again: Why did the Romans use 4.85 feet as the wheel spacing for chariots?
The reason is simple: it was the width of the two horses' behinds pulling the chariot. The story should end here, but in fact, it doesn't.
Next time you see the American space shuttle standing majestically on the launch pad on TV, take a closer look. There are two rocket boosters on either side of its fuel tank, provided by a factory in Utah. If possible, the engineers at this factory would like to make these boosters a bit fatter to increase capacity, but they can't. Why?
Because after these boosters are made, they need to be transported by train from the factory to the launch site, passing through some tunnels along the way. The width of these tunnels is only slightly wider than the width of the train tracks. However, we must not forget that the width of the train tracks is determined by the width of a horse's behind.
Therefore, we can assert that the design of perhaps the most advanced transportation system in the world today was determined by the width of two horses' behinds two thousand years ago. This is path dependence, which seems somewhat paradoxical and humorous, but it is a fact.