So I was doing a calculation at work today that involved everyone's favourite unit, the British Thermal Unit (BTU) and it got me thinking about us humans and the way we measure things. More specifically I became interested in the methodology we use for defining certain units of measurement.
For example, the temperature scales of Fahrenheit and Celsius are the two most popular in normal, everyday use today. At first glance there appears to be very little in common between the two except for the fact that, the higher the number, the warmer something is.
In layman's terms, Celsius seems a reasonably logical scale to us in that there are two major points on the scale which are easily definable and have easy to remember values. By which I mean of course 0 degrees for the freezing point of water and 100 degrees for the boiling point of water. These constitute two well defined points with the range in between split into 100. We like values of 10, 100, 1000 etc.. because we are happily decimalised, a fact no doubt down to our ten fingers which constituted some of the earliest methods of counting.
(An interesting footnote here relates to why we use 60 as our base for time, angles and geographic co-ordinates but I don't quite have the time to go into that right now. Basically, blame the Sumerians and check out here for more info - http://en.wikipedia.org/wiki/Sexagesimal). Also, a lot of countries used a non-decimalised form of currency until as late the 1970s. But trust me, we generally prefer base 10).
Anyway back to temperature. 0 degrees Fahrenheit (by contrast to 0 Celsius) doesn't seem to be anything particularly interesting, neither does 100 degrees Fahrenheit. The freezing and boiling points of water in Fahrenheit are 32 and 212, seemingly meaningless. But in actual fact, Daniel Fahrenheit defined his scale in EXACTLY the same way as Anders Celsius did, he just chose different points for his 0 and 100 definitions. For those of you interested in this he chose 0 degrees as the "lowest temperature to which he could reproducibly cool brine" and 100 degrees as the "average human core body temperature".
This type of phenomenon is in evidence all over the place. Every single unit on this planet was defined by humans and so every unit has a logic behind it. However we are often woefully ignorant of why some units are what they are.
For example, most people know that the unit of "1 foot" is, unsurprisingly the average length of a human foot in Roman or Greek times (but not Egyptian as they tended to use the "cubit" which is the length from your elbow to the tip of your middle finger). This is actually quite an intuitive unit which you could approximate if needed to. But how many of you know where the "metre" came from? Or indeed, the kilogram? I'll let you find out yourself.
It really is fascinating that we have so many different units for things (such as temperature and length) that sometimes it seems like complete overkill. Yet it turns out they were all defined for a specific purpose and so are actually all very relevant in their own right.
I wasn't really making a point with any of this, more sharing a bit of an interest of mine regarding units, measurement and the human way of trying to define measurements to make them as easy to understand as possible. I often dismiss units like yards, Fahrenheit and the like but they actually come in very useful in the right context. Astronomical Units (AUs) for example, no use to a chemist really but cracking for astronomy.
And for those of you who were wondering from before, 1 BTU is the amount of energy needed to change the temperature of one pound of water by 1 degree Fahrenheit. Pretty nonsensical these days but it made perfect sense when it was defined.
Today's #randomfactoftheday - Currently the kilogram is the only S.I. Unit defined by an object rather than a fundamental physical property
Today's #badjokeoftheday - Q: Where does bad light end up? A: In a prism
Today's #websiteoftheday - The world's longest running experiment - The Pitch Drop Experiment (http://www.theninthwatch.com/feed/)
On this day; 1473, birth of Nicolaus Copernicus - one of the greatest astronomical minds of all time.
Till next time,
DT
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