The initial magnitude scale was established by Greek astronomer Hipparchus around 135 B.C.E., categorizing approximately 850 stars into six ranges from 1st (brightest) to 6th (faintest) magnitude.

If someone asks you, “How bright is that star?” and your answer is “Pretty bright,” that isn’t very useful. And, of course, it’s worthless for any type of comparative research. So for centuries, ...