In the United States, the standard distance between the rails of railroad tracks is 4 feet 8.5 inches, and has been since the first railroads were built in this country more than 170 years ago. Why such an odd distance?

These first tracks were made by railroad pioneers from England, and that's the distance between their rails. Why? Because the people who made the first railway cars were carriage makers, and the wheels on their carriages were 4 ft. 8.5 inches apart, so their manufacturing equipment was set up to make railway cars that wide.

Why were their carriages that wide? Because the dirt roads in England at the time had ruts that were 4 ft. 8.5 in. wide. Why were their ruts this wide? The original roads in England were laid out by the Romans after they conquered the country in Julius Caesar's day. The Roman war chariots were 4 ft. 8.5 inches wide, so two war horses could be hitched to them side-by-side.

Now the story gets even more involved. You'll remember seeing the launch of a space shuttle, and the two large round rockets strapped to its side to help blast it into space. These are the Solid Rocket Boosters, or SRBs. They are made at a plant in Utah, then shipped by rail to Cape Canaveral, where they are strapped to the shuttle.

Their manufacturer would like to make the SRBs bigger than they are, but there's a problem: a railroad tunnel along the only feasible route to Florida. The tunnel is just a little bigger than the width of the railroad rails, and the rails are the width of two war horses' rear ends.

So the size of the major booster rockets on the world's most advanced transportation system is the result of ruts made by Romans twenty centuries ago. And that's how the past affects the present, and the present affects the future.

We all want our lives to matter. We want to know that what we do today will have a legacy tomorrow. But there's only one way to be guaranteed that your legacy will matter. We'll discover it today.