Those who use the metric system are accustomed to measuring temperature with the Celsius scale. Departing from the Fahrenheit system, with its arbitrary assignment of 32 degrees as the freezing point and 212 degrees as the boiling point for water, Celsius is much easier to understand. Water freezes at 0 degrees and it boils at 100 degrees. As easy as that is to understand and remember, it wasn’t always that way.
Swedish astronomer Andres Celsius developed the temperature scale in 1742. The way he originally designed it, 0 degrees was the boiling point and 100 degrees was the freezing point. His rationale was that temperatures frequently get colder than freezing in Sweden, but it will never get above boiling. He envisioned a system that would never have to deal with negative numbers.
His rationale, though sound, was at odds with the way most people think of temperatures. After his death in 1744, people continued to use his temperature scale, but they flipped the numbers around, giving us the system most of the world uses today.
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