This unusual trike proves that square wheels can roll smoothly over a row of inverted catenaries (a series of half-circles, to you and me). It was built by professor of mathematics and computer science, Stan Wagon.
If you want to try it out you’ll need to head over to Macalester College, where any vistitors can hop on and have a go. The odometer shows that it covers just over 15 miles each year.
But how could this ever be useful? According to the college website, it may have made life easier for ancient Egyptians.
Near some ancient pyramids in Egypt various pieces of wood cut into quarter-circles have been found. One theory is that they were used so that large blocks of marble with square cross-sections could be easily rolled. Indeed, a quarter-circle is close enough to a catenary that this would work. In more modern terms, if you had a multi-ton cube over a catenary road, then you could roll it in much the same way that you can roll a multi-ton car over a flat road.
More information on the college’s website here.