5.30591 Olympic swimming pools

It’s been a while since the last entry in my series on length measurements, so I thought it was about time for another.  Since I’ve been thinking about ancient Greece recently, it seemed appropriate to go for an ancient Greek unit of measure.  However, apart from one of a number of different cubit measures (which I’m planning to write about later), there were no  Greek units amongst the list of measurements that I prepared from the Google maps DMT when I first planned the series. Checking back with the DMT, it seems that this was because there weren’t any to choose from rather than just that I didn’t pick any for my list.

Employing a bit of lateral thinking, the closest I could come up with from my list was the Olympic swimming pool.  I suspect that if swimming featured in the ancient Olympic Games (it’s not mentioned in the Wikipedia article, but that doesn’t necessarily mean it was never contested) they didn’t use a standard size pool.  A swimming pool used for the modern Olympics, though, is supposed to have a standardised length of 50m.  It also has other details (such as width, water temperature, number of lanes and minimum depth) standardised according to the FINA specification, but it is the length (the greater of the two horizontal dimensions) that is used when an Olympic swimming pool features in Google’s DMT.  As far as I’m aware, it’s not a particularly common unit of length for measuring things other than swimming pools (the other common size of pool for competetive use being 25m, or half Olympic size).

As the title of this post indicates, the span of the Menai Suspension Bridge is about 5.3 Olympic swimming pools.  I suppose that means that swimming across the straits would be equivalent to doing 5 lengths of the pool (ignoring the added difficulties imposed by the strong currents and the distinctly sub-spec water temperature).  In any case, I think I’ll stick to cycling across the bridge rather than swimming under it.

I was interested to note that the Google DMT’s list of units didn’t include the σταδιον (stadion, plural: stadia; usually anglicised as stadium or stade), which is one of the better known ancient Greek distance units.  The problem could be that there is no single authoritative conversion factor from metres to stadia: although a stadion was defined as 600ft (according to Herodotus), there were several conflicting definitions of a foot in use at the time (dependent on geographical location) and hence a stadion in one place could be longer or shorter than one somewhere else.

Apparently the stadion unit was named after a running race over that distance, and the race in turn was named after the building in which it took place; as you might expect, this building also gave rise to the modern word “stadium” as a sports venue.  Wikipedia is slightly confusing as the stadion unit page says an Olympic stadion was about 176m, while the stadion race page says that the stadion race track at Olympia was about 190m long.  It could be that the stadion unit began life as the length of the race track and later standardised as 600ft and that the definition of a foot in use at Olympia was 1/600 of 176m, thus leaving the race track slightly longer than the new definition of a stadion.

Taking the definition of 1 stadion = 176m, the Menai Suspension Bridge measures about 1.5 stadia.  Using the length of the Olympic racetrack (1 stadion = 190m), it is about 1.4 stadia.

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