Eli5: I’m trying to find the best way to word this but how does one measure “negative degrees”, like in temperature, like how do you quantify the absence of something that isn’t tangible?
In: Chemistry
Fun fact: the opposite of heat isn’t heat but the absence of heat. “Cold” isn’t really a thing, it’s a construct for helping us compare various temperature points. Temperature is a way of measuring energy. What’s being measured isn’t an absence of something but instead a reduction on a fixed scale with an arbitrarily defined zero point.
The problem is that we need common points of reference. As early scientists developed the ability to consistently measure and quantify temperatures and built thermometers to measure those temperatures reliably and repeatedly, they had to define what we were measuring it and the steps we were measuring it in. The first common scale was the Fahrenheit temperature scale, developed by a Dutch physicist named (shockingly) Fahrenheit. Per the official paperwork, he defines the zero point of his scale as the temperature which a mixture of water and ammonium chloride freezes, which really makes little sense as a zero point until you consider the unofficial reason of zero being the lowest temperature his hometown reached while he built his thermometers and then having to backwards justify a repeatable value. He defined 32 degrees as the temperature at which pure water freezes because why not, and 96 degrees as the temperature of the human body because at this point he was still developing a foundation on which temperatures would be measured in the first place.
After a while people realized that Fahrenheit was, well, very arbitrary in the values it set so they developed another scale – Celsius. It set the zero point at the freezing temperature of water with steps of 1 resulting in 100 being the boiling point of water, which is very useful in science but odd for daily use because half of the scale is very inhospitable for human life, but it gained traction due to its scientific adaptation and has been adopted in much of the world.
There’s also the Kelvin scale, which uses the same degree increments as Celsius but defines the 0 point as the point in which there is no heat energy to measure. In Kelvin there are no negative values because nothing gets colder than 0 Kelvin, and water freezes at 273.15 degrees.
Basically, there isn’t a singular correct way to measure temperature so various decisions were made to build a consensus on how we as a society would have common scales to measure temperatures, each with its advantages and disadvantages.
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