I grew up in England where the atmospheric condition forecasters informed the states what to wait temperature-wise in units of degrees Celsius (°C). I vaguely think that, when I was a kid, we also talked about degrees Centigrade (°C). In fact, nosotros used the terms Celsius and Centigrade interchangeably and I never wondered why.

When I moved to America, information technology was a flake of a stupor to my organisation to run into the weather forecast being presented in units of degrees Fahrenheit (°F). For quite some time, I had to perform a °F to °C calculation in my head to piece of work out whether it was going to be hot or cold (I've now been in America so long that I have to perform °C to °F calculations in my head when I return to England to visit my beloved former mom).

Recently, I saw a funny skit that purported to be a conversation between the German physicist Daniel Gabriel Fahrenheit (1686–1736) and the Swedish astronomer Anders Celsius (1701–1744). It was Fahrenheit who proposed the original temperature scale upon which what we at present call the Fahrenheit scale was based, while Celsius created a temperature calibration that evolved into what we now call the Celsius scale.

The thought behind the skit was that Daniel Fahrenheit and Anders Celsius are at a cocktail political party having a cozy chat. We tin imagine their conversation every bit being something like the following:

C: "Greetings Daniel one-time chap. I hear you've created a new temperature scale. Funnily plenty, I've been working on something like myself."
F: "Felicitations Anders my dear beau. You're looking well. Yes, I have indeed devised a new temperature calibration."
C: "Then, upon what did you base your nil-degree signal?"
F: "I used the freezing temperature of a solution of brine made from equal parts of ice, water and a salt (ammonium chloride)."
C: "Hmmmm" (said in a dubious tone).
F: "Why are you 'hmmmming' similar that? Can y'all recall of anything meliorate?"
C: "What about something anybody is familiar with, similar the freezing bespeak of water, for example?"
F: "Well, I suppose that would be an culling" (said in a begrudging way).
C: "And what value does the boiling signal of water have in your scale."
F: "Ah, that's the clever part, h2o boils at 212 degrees on my scale."
C: "Hmmmm" (said in a dubious tone).
F: "You are 'hmmmming' over again. Can you think of something better?"
C: "What nigh a nice round number like 100?"
F: "Well, I suppose that could accept been some other possibility" (said in a somewhat curt tone).

Of class, nothing similar this actually took identify, but it'southward still amusing the retrieve about. The thing is, as we shall come across, nothing about temperature is simple, to the lowest degree of all measuring it.

What is Temperature?

The simplest definition of temperature is that information technology's a measure out of how hot or cold something is, but that really doesn't help us as much as nosotros might wish. Equally Piotr Małek and Álvaro Díez say on OmniCalculator.com: "[To define temperature] we have to turn to physics, in particular to thermodynamics and statistical physics, which is like thermodynamics meets quantum physics."

Now, I love thermodynamics and statistical physics as much equally the next man, which is to say, "Non a lot," so I think we volition boot this particular question down the road for a future give-and-take.

Why Measure Temperature?

Every bit to why nosotros want to measure temperature, different people take different reasons. Chemists demand to know the temperature to control their reactions, scientists need to be able to measure out temperature as part of their experiments, and so on and so forth.

For most of us, in addition to cooking (i.eastward., setting the desired temperature on the oven), our main involvement in measuring temperature is in knowing what to expect weather-wise so we tin can make an informed decision as to whether shorts and a T-shirt are a good thought, or if woolen undergarments and furry hats (or furry undergarments and woolen hats) will be the guild of the day.

Thermoception

If you enquire most people how many senses they accept, their articulatio genus-jerk reaction volition be to answer, "Five of grade: Sight, Hearing, Touch, Gustatory modality, and Smell." Would you believe that these are the same 5 senses that were get-go described past the ancient Greek philosopher and scientist, Aristotle (384–322 BC), but nosotros now know that humans take at to the lowest degree ix senses, and possibly as many as twenty or more.

In particular, in the context of our discussions hither, as I wrote in How Many Senses Do Humans Have?: "Thermoception, likewise known every bit thermoreception, is the sense by which nosotros perceive temperature. Even if you are blindfolded, for example, if you concur your hand close to something hot, y'all tin feel the heat in the form of infrared (IR) radiation. Similarly, if y'all hold your manus over a block of ice, you can find the lack of oestrus."

Easy Peasy Lemon Squeezy

Manifestly, the "official" antonyms to "like shooting fish in a barrel peasy lemon squeezy" are "hard hard lemon hard" and "difficult difficult lemon difficult," merely I find both of these to be less than satisfying. I prefer "stressed depressed lemon zest," but this in no way relates to what we are talking nearly here.

To exist honest, the sad thing about measuring temperature is that — outside of laboratories with specialist equipment — we really don't seem to be tremendously adept at it.

Recently, for instance, items of food in our fridge didn't feel as cool as I was expecting, so I decided to purchase a special fridge/freezer thermometer from Walmart. In fact, I concluded up buying two because (a) I no longer trust a single thermometer reading and (b) there were only two on the shelf.

The reason I no longer trust a single thermometer is that, a couple of years ago, our HVAC organization died and nosotros had to purchase a new one. Every bit function of this, we ended up with a new thermostat. Even though we set the new thermostat to the same temperature as the previous unit of measurement, the house felt hotter.

In order to wrap my head around this conundrum, I ambled downwards to The Home Depot to pick up an outside thermometer. On the bright side, they had almost 30 of the lilliputian rascals. On the downside, fifty-fifty though these devices were on a shelf nether a shaded area of the garden center, they all presented different readings with a spread of well-nigh 10 degrees. As a result, I spent a happy few minutes adding all the readings together, taking the average, and then determining which of the thermometers was closest to that average.

The only reason I mention this hither is that I was surprised to discover that, almost ane/5th the mode through the 21st century, it appears that we still find it less than easy peasy lemon squeezy to tell the temperature.

Who Invented the Get-go Thermometer?

This is a bit of a catchy question considering there have been so many people stomping through history with hob-nailed boots. First, let's define what a thermometer is. For this, I quite like the Wikipedia definition, which reads as follows:

A thermometer is a device that measures temperature or a temperature gradient. A thermometer has two of import elements: (1) a temperature sensor (due east.thou., the bulb of a mercury-in-glass thermometer or the pyrometric sensor in an infrared thermometer) in which some alter occurs with a change in temperature; and (2) some ways of converting this change into a numerical value (e.m., the visible scale that is marked on a mercury-in-drinking glass thermometer or the digital readout on an infrared model).

The precursor to the thermometer was the thermoscope, which is essentially a thermometer without a scale. Although a thermoscope couldn't indicate a specific temperature, it could be used to show differences in temperature, thereby allowing its users to determine if something was getting hotter or colder. Ii contenders for the creator of the beginning thermoscope are Hero of Alexandria (10–70 AD) and Galen of Pergamon (129– ~208 AD).

Work on thermoscopes continued all the style to the early 1600s, with the near famous practitioner being the Italian astronomer, physicist, and engineer, Galileo Galilei (1564–1642). Somewhere around 1610, the first person to put a calibration on a thermoscope, thereby turning information technology into a thermometer, may have been Francesco Sagredo (1571–6620), who was a Venetian mathematician and close friend of Galileo, or it might take been the Venetian physiologist, physician, and professor Santorio Santorio (1561–1626), or it could accept been someone else — who really knows?

What the FAQ is Fahrenheit?

This is a fleck of a tortuous tale, merely we can summarize it every bit follows. Sometime circa the 1700s, the famous Danish astronomer Ole Christensen Rømer (1644–1710) came up with his own temperature calibration. As an aside, there were nearly 30 other temperature scales in utilise at that time, 1 of which was based on the melting betoken of butter (I'm going to take a wild guess that the proponent of this one was French).

The ancient Babylonians have a lot to answer for, non least that there are 6 10 sixty = 360 degrees in a circle, threescore seconds in a degree, 60 minutes in an hour, and 60 seconds in a infinitesimal Since, as an astronomer, Rømer was used to dividing things by 60, he decided to use lx as the temperature of the boiling point of h2o.

By dividing this into eighths, Rømer ended up with values of 0, vii.five, xv, 22.v, 30, 37.5, 45, 52.ii, and sixty. For reasons I don't fully understand, he set seven.5 as representing the freezing point of water. If you are interested, you can observe out more than in this excellent video by Veritasium.

The bottom line is that Fahrenheit met Rømer and was introduced to his temperature scale. Since he didn't like all the fractions, Fahrenheit made a number of adjustments, eventually ending upwardly with the values of 32 °F and 212 °F for the freezing and boiling points of water, respectively.

Now, these values may seem a little capricious, but there are all sorts of hidden tidbits of trivia and nuggets of knowledge here, such every bit the fact that 212 – 32 = 180 (half the number of degrees in a circle). Also, that Fahrenheit was using mercury in his thermometers, and a alter of ane degree in the Fahrenheit calibration results in a 1/10,000th change in the book of mercury. Coincidence? I recall non!

What the FAQ is Celsius?

Most people presume that Anders Celsius took the temperature at which h2o freezes and said, "permit'southward phone call this 0 degrees." Also, that he took the temperature at which h2o boils and said, "let's telephone call this 100 degrees."

In reality, although Celsius did come upward with the idea of separating the freezing and humid points of water by 100 degrees, he initially started off with 0 °C representing the humid point of water, while 100 °C represented the freezing point of water. It wasn't until a twelvemonth afterward his decease that other users decided to swap them over. The reasoning behind all of this is presented in some other awesome video past Veritasium.

The really interesting affair is that, in 1743, a twelvemonth before Celsius died, the French physicist, mathematician, astronomer and musician Jeane-Pierre Christin (1683–1755) also came up with the idea of using 0 and 100 degrees to stand for the freezing and boiling points of water, respectively. And so, why don't we say things like "100 degrees Christin"?

In reality, for the longest fourth dimension, neither Celsius nor Christin'due south names were used. Instead, based on the fact that there were 100 steps between the freezing and boiling points of water, most people used the term "Centigrade."

The problem here is that the discussion "centigrade" has multiple meanings in different languages. Thus, in 1948, the International Bureau of Weights and Measures decided to rename this calibration afterwards a scientist like other temperature scales, and Celsius "won the toss," as information technology were.

Instance Values

In addition to the freezing and boiling points of h2o, another value in which people are often interested is that of normal human torso temperature. Also known as normothermia or euthermia, this is the typical temperature range institute in humans, which is 36.5 to 37.v °C (with an boilerplate of 37 °C) or 97.7 to 99.5 °F (with an boilerplate of 98.half-dozen °F).

Comparing of Celsius and Fahrenheit (Click image to run across a larger version — Image source: Max Maxfield)

Only to provide a sense of scale (no pun intended), the sublimation temperature of a block of dry water ice is –78.v °C (–109.3 °F), while the humid point of liquid air is –194.35 °C (–317.83 °F).

The everyman limit of the thermodynamic temperature scale, a state at which the enthalpy and entropy of a cooled ideal gas reach their minimum value, is known as absolute zero. This occurs at –273.15 °C (–459.67 °F).

Conversion Formulas

Fahrenheit to Celsius: Subtract 32, then multiply by 5, then divide by 9.

Celsius to Fahrenheit: Multiply by 9, split by 5, then add 32.

Every bit a point of interest, the Celsius and Fahrenheit scales converge at minus 40 degrees, so –twoscore °C and –twoscore °F correspond the same temperature.

Merely Which is Best?

Everyone thinks that whatever they grow up with is the best manner to do things, and this applies to measuring things in Celsius and Fahrenheit, but tin can nosotros really say that 1 is improve than the other?

On the 1 hand, dividing the span betwixt the freezing and boiling points of water into 100 degrees is like shooting fish in a barrel to wrap our brains effectually, simply do we really care? The vast bulk of u.s. are interested in expressing temperature only in regard to our condolement, for which purpose we use the temperature of the surrounding air. When inside our homes, offices, or other buildings, we set the temperature we desire; when exterior, nosotros use temperature as one criterion in our controlling process every bit to what apparel to wear.

Humans are very sensitive to temperature; a small departure in temperature tin have a large effect on one'southward comfort level. In the case of the Fahrenheit temperature scale, we have 1.8x the integer resolution to express and communicate temperature without being obliged to use fractional values. On this basis, i could contend that the Fahrenheit temperature scale is meliorate suited to our everyday requirements.

Only Look, There's More

Some people say that 0 °C (32 °F) is divers equally the temperature at which water freezes; others say it's defined as the temperature at which water ice melts. Is there a difference?

In fact, the terms "freezing point" and "melting point" describe the same intermediate point in the transition of thing from liquid to solid (freezing) or from solid to liquid (melting). While h2o is in the process of freezing or melting, its temperature is not changing – information technology remains at 0 °C (32 °F) throughout the entire freezing or melting procedure.

Similarly, when the temperature of water rises, information technology will commencement to boil at 100 °C (212 °F), and it will remain at this temperature until all the water has boiled abroad.

Having said this, the freezing, melting, and boiling points of h2o are divers at a pressure of one standard atmosphere, which itself is divers as being the mean atmospheric pressure at sea level. The thing is that the boiling point of water is the point at which vapor pressure level equals atmospheric pressure, and atmospheric pressure decreases every bit elevation increases.

This means that, if you are climbing a mountain, for example, so equally your elevation increases and the atmospheric force per unit area decreases, so too volition the humid bespeak of water decrease. Every bit a result, a cup of tea brewed on pinnacle of mount Everest won't be nearly every bit hot and tasty as one brewed in the awesomely beautiful dales of Yorkshire, England, which — by some strange quirk of fate — happens to be the county of my birth (what are the odds?).

Over to You

Did you already know all the above, or did you lot larn something new? Either mode, I'd dearest to hear what you think (at the very least you could say something nice about my spiffy thermometer diagram, which took a lot longer to draw than yous might remember). Also, it would be great if you have whatsoever additional nuggets of knowledge or tidbits of trivia regarding temperature in general, Celsius (Centigrade), or Fahrenheit that you'd care to share.