My lovely bride pointed out to me yesterday that I was wrong. This is not news around here. She keeps records of things like low temperatures and she showed me at least two instances where we were well below the ten degrees Fahrenheit I mentioned.
In December of 2013 we had back-to-back nights of -5 ºF and in January of 2017 we bottomed out at -10 ºF.
A negative ten degrees, or ten degrees below zero, would be -23 on the Celsius scale!
Our Founding Fathers did not know about negative numbers, or if they did, they considered them nonsensical. Negative numbers had been around for a thousand years and had been used by Indian and Arabic mathematicians for centuries but did not really gain much traction in the West until the 18th century.
Numbers are more than just quantities. When you put them on a number line you now have something more than just size or magnitude, you now have direction.
A negative number has the same magnitude but it is the opposite of a positive number. On a temperature scale the change in direction is up or down and on a number line it is left or right but the concept is the same.
Beyond that, negative numbers occur in algebraic solutions (remember the quadratic formula?) and along with imaginary (complex) numbers are essential in engineering and science. You just can’t do enough stuff if you only have positive, real numbers.
The obvious use of negatives to represent debts, losses, and outflows in accounting did not become a common practice until modern times.
My sister-in-law pointed out to me that the new vaccine from Pfizer for COVID-19 has to be stored at -80 ºC (-112 ºF). Brrr! Imagine if we could not talk about such things like eighty degrees below the freezing point of water or that such notions were not a commonplace part of a child’s education. That’s weird to think about. Many of the profoundest minds in our history would have been bewildered by something we teach in elementary school! As a race, humanity is a hell of a lot smarter now than we were in the past. That’s not to say we’ll always act smart, just that we are smarter.