Episode: 1443
Title: HPR1443: Fahrenheit 0-100
Source: https://hub.hackerpublicradio.org/ccdn.php?filename=/eps/hpr1443/hpr1443.mp3
Transcribed: 2025-10-18 03:02:34

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Fantastic.
Hello, this is Bill in Michigan, also known as Bill M.I. in various forums and chats.
As a big fan of hacker public radio, I invite everyone that gets an inspiration to make
an episode.
Hey, if I can do it, anyone can.
Yes, I had an inspiration.
It was HPR episode 1432 titled Fahrenheit 212, where Joel and Ken talked about the two
major temperature scales.
As an engineer here in the United States, I work in both Fahrenheit and Celsius scales
with relativities, and at the end I'd like to travel some common temperatures that both
can relate to.
My inspiration comes from the huge gap unsaid about the Fahrenheit scale.
While today its definition may be tied to water, this was not Mr. Fahrenheit's goal.
I think most historians will agree Mr. F wanted temperature units that did the following.
He wanted the typical coldest temperature of the year to be zero.
This is outside temperature now.
He wanted the typical hottest temperature of the year to be 100.
Yep, it's that simple.
Unfortunately, it was defined by a person that was born in 1685 in what's now Gdansk,
and lived throughout the Dutch Republic.
For our Celsius friends, here's the detail on Fahrenheit's zero to 100.
In Celsius, that's minus 17.778 to plus 37.778.
It's probably a good idea to drop decimals.
We'll just call that minus 18 to plus 38.
Now Daniel Gabriel Fahrenheit was the inventor of the Mercury in Glass Thermometer, and we
know how that became the technology to measure temperature for centuries.
It was the thermometer used for a long time.
With his thermometer, he was able to accurately measure things rather repeatedly.
Human body temperature was one of these, outdoor temperature another.
It may be fact or legend, but it was reported Mr. Fahrenheit used the coldest temperature
of the winter of 1708, 1709 in Gdansk as his zero.
He knew what that temperature was on his thermometer, and he wanted that to be zero.
But Mr. Fahrenheit knew he needed a good reference, otherwise his scale would never be valid, because
it couldn't be recreated elsewhere.
He needed some references near his zero and 100 to use his calibration points, or the
world would never use it.
In 1724, he published his scale to the world.
He had come up with a brine solution using ammonium chloride, water, and ice, I guess, and
to create his zero, and today it's not easily reproduced, but he could reproduce it, apparently.
He knew the freezing point on his scale of water was 32.
And he needed something near 100.
Well, we have a pretty good one, it's called human body temperature is very close to 100
Fahrenheit.
Today it's 98.6, but he assigned it to 96.
After tweaks of the Fahrenheit scales to get things in order later on, long after Mr.
Fahrenheit was gone, his 96 became 98.6.
I suspect that he knew that the hottest temperature of the year typically exceeded human body
temperature, and I think he's probably right in that regard.
Now Ken, I can turn around your wonderment in a very Fahrenheit way and say, where in
the world did Celsius get minus 18 and plus 38?
But I won't do that.
It turns out the climate here in Michigan matches Mr. Fahrenheit's scale very well.
Obviously it does depend on where you are in the world.
I'm sure this Scandinavian countries would think it's a little bit biased as would the
African countries or here in the United States, we have the extremes of maybe something
like North Dakota and Florida, they wouldn't think that.
Here in Michigan, the state of Michigan, our climate pretty much is the coldest temperature
of the year is around zero.
And the hottest temperature of the year is around 100 Fahrenheit, of course.
I would say that we have probably the same climate that Mr. Fahrenheit had.
So we're lucky in that regard.
But anyway, think of the Fahrenheit scale as, yeah, if it's above 100, it's pretty darn
hot, maybe an extreme.
Even if it's below zero, it's pretty darn cold, possibly an extreme.
But that's where all this comes from.
I found an interesting fact regarding Mr. Celsius.
Evidently he decided that originally proposed that his zero would be the boiling point
of water and his 100 would be the freezing point of water.
I guess if he had succeeded in getting that approved, that it would have been a quite
a different temperature world today.
Or it's very possible for and I would have nominated it anyway.
I did find that as I was doing.
I did a little bit of research for this just to make sure I wasn't way off in left field.
And Wikipedia is your friend.
Now Joel and Ken, you did get into absolute temperature scale, where there actually is
a temperature that cannot be any colder.
It is zero, where molecular motion, internal energy is in fact zero.
We did a lab experiment in college that basically found absolute zero in a calorimeter, which
is a fancy laboratory thermos at temperature of, I'm not sure what we used and I'm not
sure what we used for the energy, but with no amounts of energy added and subtracted,
you could plot the points of internal energy versus temperature.
What's really interesting is this is a perfectly straight line.
And although we didn't get down there, we could just kind of extend that line and see
where it crossed the axis to discover what was the temperature when energy became zero.
We came pretty close.
A lot of people in the lab have various accuracies, but we were in a laboratory finding what the
value of absolute zero actually is.
And not mentioned in the episode, although the Kelvin scale is well known, that's the
Celsius version, using Celsius degrees in it, of Kelvin.
The Fahrenheit equivalent of the absolute scale is called Rankin.
And I noticed looking it up that they put an E on the end of it in some places.
I never saw it with an E on the end.
I don't think it's Rankine, it's Rankin and represents the absolute zero.
The absolute zero in Celsius is, let me get up my little spreadsheet I made here, minus
273.15 Celsius is absolute zero.
In Fahrenheit, that's minus 459.67.
Now on the Kelvin and Rankin scales, of course, by definition, those values are both zero.
Now let's go up the temperature scale from our absolute zero and see some points of interest.
One of the first things that comes to mind here is minus 40 Celsius, because that's equal
to minus 40 Fahrenheit.
That's where the two common temperature scales cross.
The next point, of course, is where Fahrenheit is equal to a value zero.
Zero Fahrenheit, as we stated earlier, is minus 17.778 Celsius.
Now zero Celsius, as we go up warmer and warmer here, zero Celsius is the freezing point
of water by definition.
And today, the freezing point of water is defined to be Fahrenheit equal 32 degrees.
That's a well-known temperature.
How about, the Fahrenheit scale, remember, is zero to 100 outdoor temperatures, typical
where Mr. Fahrenheit lived and so forth.
Right in the middle is 50 degrees Fahrenheit.
Here in Michigan, that's a spring or a fall day.
It's a nice cool brisk with comfortable 50 degrees Fahrenheit.
What's that in Celsius?
Exactly 10 degrees Celsius.
No decimals hidden or anything.
It's 50 degrees Fahrenheit is equal to 10 degrees Celsius.
Is that about what your spring and fall days are?
Some other temperatures come up next, as we go warmer and warmer.
Let's hit what's typically called room temperature.
In my engineering stuff, I often hit 25 degrees C.
Seems to be the world's definition of room temperature, which is a little bit warmer
than the rooms that I like to be in, but that's 77 Fahrenheit.
I like it more or let down like 72.
And if you want to save energy in the winter, maybe 68, but perhaps the 23 degrees Celsius
is a more accurate room temperature, I see in various specifications, engineering specifications.
73.4 Fahrenheit is often a better idea of room temperature.
Let's go up to the next point is human body temperature.
37 degrees Celsius.
All my Celsius friends probably know that well.
That's 98.6 Fahrenheit.
And originally, Mr. Fahrenheit used 96, but today it's 98.6.
And I think medical science has even changed that a little bit.
I think it's a little bit higher now.
The next thing is Fahrenheit 100.
Well, we stated earlier that in Celsius, the temperature is 37.778.
Let's go warmer and warmer and I find one of those points that for some reason has stuck
with me over the years.
85 degrees Celsius is equal to 185 degrees Fahrenheit.
Don't ask me why I remember that, but you can probably see why.
The next point is the boiling point of water, which is by definition 100 degrees Celsius.
212 degrees Fahrenheit, both by definitions, I believe.
The next temperature I run into as an electrical engineer, the value of 125 degrees Celsius,
is one I run into all the time.
It's the junction temperature of siliconships, usually of a particular grade.
It also happens to be a military temperature.
Anyway, 125 degrees Celsius is 257 degrees Fahrenheit.
And I know that point well because many of our specifications are in Fahrenheit, it turns
out with the job that I have right now.
Anyway, let's keep going.
The next temperature I'll get to is the temperature of a soldering iron tip that is ready to do work
on a computer board.
We usually set that to 700 degrees Fahrenheit.
That's 371 degrees Celsius, just to give you an idea.
This worth mentioning is how the Fahrenheit degree, a change of one Fahrenheit degree,
is a smaller temperature increment than one degree of Celsius.
The ratio is 9.5 or 5.9 depending on which way you're going.
You can see that in the freezing and boiling point of water at 32 and 212, which is a 180
degree change, wherein Celsius, the same change, is 100 degrees.
So 180 over 100 is 9 over 5, and there's that nice ratio.
It was actually defined later that Fahrenheit's scale would have exactly 180 degrees between
those two temperatures.
Well that wraps up my look at the two temperature scales in use today.
And I think the chances of the U.S. converting to Celsius is probably about the same chance
as Brits driving on the right-hand side of the road, instead of the wrong-hand side of
the road.
Oh, I had a lot of fun.
Take care, and thanks for listening all, and thanks again to Hacker Public Radio.
Bye.
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