as an australian canadian the fahrenheit temperature scale hasalways seemed a bit arbitrary to me. i mean why does waterfreezes at 32 degrees? why that integer and what exactly does 0 represent? according to many sources the fahrenheit scale wasdefined by setting 0 degrees equal to the temperature ofthe ice salt and water mixture and a hundred degrees beingroughly equal to human body temperature. but that isn't true.
the real story is much moreinteresting and scientific. august 14th, 1701 wasalmost certainly the worst day in the life of 15 year-olddaniel gabriel fahrenheit. on that day, both of his parentsdied suddenly from mushroom poisoning. and he was sent from polandwhere he lived to amsterdam to becomean apprentice bookkeeper. but fahrenheit couldn'tstand his apprenticeship and ran away so many times that his employerput out a warrant for his arrest. traveling from city to city around europe,
he became fascinated withscientific instruments and in particular, thermometers. in 1708, possibly seeking helpwith the warrant, fahrenheit met withthe mayor of copenhagen, who happened to bethe famous astronomer ole rã¸mer. rã¸mer is known for observingthe eclipses of jupiter's moons and realizing that variationsin the timing of those eclipses was caused by the timeit took light to reach earth. in other words, he found a way
to accurately measurethe finite speed of light. but, more pertinent to this story, in 1702, rã¸mer was houseboundafter breaking his leg. and to pass the time, he devised abrand-new temperature scale with the freezing point of waterat 7.5 degrees and body temperature at 22.5 degrees. now, this might seem odduntil you consider that rã¸mer wanted the boiling point ofwater to be 60 degrees. as an astronomer, he hadexperience dividing things by 60.
so if you take this scale, divide it in half, in half againand in half once more, you find the freezing point of waterone eighth up the scale, and human body temperaturethree eighth up the scale. so at their meeting in 1708 fahrenheit learned of rã¸mer's temperaturescale and adopted it as his own, adjusting it slightly because he found it "inconvenient and inelegant onaccount of fractional numbers". so he scaled them up to 8 and 24.
and this is the original fahrenheit scale. he produced thermometersfor some time using this scale. but then at some later point, fahrenheit multiplied all numberson the scale by 4 setting freezing point to the now-familiar32 and body temperature to 96. it's unclear exactly why he did this. he may just have wantedfiner precision in his measurements. but i think there was a better reason. you see, fahrenheit was anexcellent instrument maker.
his thermometers agreedwith each other precisely at a time when that was unheard of. he pioneered the use of mercuryas a measuring liquid, which has the benefit of a much higherboiling point than the alcohol used in most otherthermometers at the time. and for these accomplishments he was inducted intothe british royal society. and we know that he readthe works of newton, boyle, and hook, in which he would have come across the idea
that one degree increase intemperature could correspond to a specific fractional increase inthe volume of the measuring liquid. and today, a one degree fahrenheitincrease in temperature increases the volume ofmercury by exactly one part in 10,000. is this just a coincidence? well, we'll probably never knowfor sure because as an instrument maker fahrenheitwas very secretive about his methods. but i think the data stronglysuggest that this was the case. so, what exactly did zero represent onthe scales of fahrenheit, and rã¸mer?
by many accounts, it's the temperature ofsalt ice and water mixture. the only problem is there are differentdescriptions of these mixtures and none of them actually producesthe temperature they're supposed to. more likely, i think they picked thecoldest temperature in winter set that as zero and later used ice and brine tocalibrate new thermometers. in his day, the fahrenheit thermometerwas the best you could get. but now his scale is onlyused regularly in the cayman islands, bahamas, belize— oh, andthe united states of america.
so maybe it's time we alladopted the global scale of temperature: celsius, which by the way,wasn't invented by celsius at all. hey! so that was somethinga little bit different. this video was animated by marcello ascani. i've got a link to his channel inthe description. you know, i became really fascinatedwith temperature scale after i saw the originalcelsius thermometer. you can see that video here. now, this video was supported in part byviewers like you on patreon,
and by audible.com, a leading provider of audiobookswith hundreds of thousands of titles in all areas of literature, including fiction nonfictionand periodicals. and for viewers of this channel, audible offers a free 30-day trial where you can downloadany book of your choosing. just go to audible.com/veritasium. and i have a book thati would recommend to you.
it is called the structure of scientific revolutionsby thomas s. kuhn. this is a classic in the history andphilosophy of science. and it'll make you see sciencein a different way because it shows us thatscience is not just one process but there are actuallyrevolutions that take place when big discoveries are made. and that really changedmy thinking about science when i first read this bookten years ago. so you can check it out by going toaudible.com/veritasium
downloaded for free andtry out the audible service. i want to thank audible for supportingme and i want to thank you for watching.
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