Whence significant figures?

Significant digits can arise out of less significant data, right? For instance, you probably learned in ninth-grade science that a number rounded to one significant figure can be magically turned into one with three significant figures simply by changing measurement systems, right?

Well…I hope that’s not what you learned. It’s fake precision (not to be confused with fake news). But the Associated Press blithely converts “1 trillion tons” to “1.12 trillion tons” by switching to U.S. measurements:

The iceberg is described as weighing 1 trillion tons (1.12 trillion U.S. tons).

But wait…that’s not all! The very next sentence claims that “a 5,800-square-kilometer (2,240-square-mile) section broke away.” Maybe that’s not quite so egregious, since we have no way of knowing whether the SI measurement really has two or three (or even four) significant figures when it’s written in this conventional manner.

Categories: Math, Teaching & Learning