# Physics education from unexpected sources

I’m currently spending my time earning a “Scientific Scuba Diver” certification.   For those not in the know, this is a professional qualification, proving that you can collect data and rescue scientists and cope with setting up equipment in cloudy water and navigate and so on.   It’s a 100 hour course and I’m doing it over two weeks, here in San Diego.   It’s fun – both classroom stuff and lots of tasks to complete on various dives.   It is possibly the last place that I expected to learn anything about physics.

Even recreational dive courses contain sections on the physics of diving.   It’s fairly important to understand at least the gas laws and the effect of pressure on solubility, since you breathe air at the pressure of the water around you, thereby ensuring that your lungs don’t collapse when you’re at depth.    I didn’t know that before I started to dive and it’s really pretty cool.    It causes all sorts of problems if you go down deep for long periods of time… but I digress.    The first scuba manuals were written in the fifties and sixties, back when imperial units were especially popular.   And so the dive manual states “There are four temperature scales:  Farenheit, Celsius, Kelvin and Rankine”.   Rankine?   As I rather arrogantly pointed out at some point (although I really didn’t intend it that way), I have 3 degrees in physics and I have never heard of the Rankine scale of temperature.      It turns out that it’s the absolute temperature scale for farenheit.   -459.67 degrees F is 0 R.   I suppose it’s a perfectly obvious analogy, but it had genuinely never occurred to me that it might exist.   Has anyone out there heard of it?

I think that the long-term aim should definitely to be to convert all the dive manuals (and diver thinking) to Centigrade, but I accept that this takes time and that an extra conversion stage when teaching ideal gas laws might confuse some people.   Most people in the US think in farenheit when it comes to practical experience and diving in 50 degrees F water is definitely an experience.  However, I have to give the course credit for having taught me something that I did not know from the history of my subject.

### 5 responses to “Physics education from unexpected sources”

1. I suppose it’s a perfectly obvious analogy, but it had genuinely never occurred to me that it might exist. Has anyone out there heard of it?

I don’t remember where, but I remember knowing of it back in elementary school. Then again, Farenheit is the norm in the states, so maybe it seemed more natural here…

2. I’d heard of it sometime in elementary school, I think from one of my fellow larval-stage science geeks.

3. besu

I had heard of it in high school. It’s also mentioned in a stat-mech book by Schroeder that a lot of colleges in US use.

4. Acleron

I came across it once when it was used in the space shuttle for the maximum temperature of a pump. I’ve often used it as a semi-joke about the units that are used in the US. From your post, it seems it is not employed much, I’ll change the joke. See, I’ve learned something as well.

5. I’ve actually heard of this scale, but could not have defined it (just, “Oh yea, the Rankine scale. I remember that term!”). Definitely has been many (>20) years since I heard it last, though.