If you measure two identical items, one in feet, and another in centimeters, there's no difference, right? Just do the conversion, and you'll see that the two objects are the same size, in both feet and inches. Right? No. Bad. Wrong. What?
Minute Physics — in one of its longer, many minute editions — explains why the differences in measurements at difference places in the universe, and in different ways, is what makes everything work. This is one of the more complicated Minute Physics clips you'll come across, but as always, it's as concise as possible, and very easy to digest for dummies with a BA in English. [YouTube]