FINAL THOUGHTS FROM SYENNA

Dear Reader,

This month I have somehow become sensitised to something that I will call dimensional blindness.

It all started when I had a home charger point installed for my electric car. We only have a 60A fuse for our mains electricity supply and, believe it or not, no mains isolator switch. I phoned up the infrastructure owner to say that I needed a bigger fuse and an isolator.

“Oh yes”, they said, “you need more Volts”.

“Really?” says I, “I was thinking more Amps”.

“Oh yes, I’m always getting those mixed up” came the reply.

If the infrastructure owner doesn’t know the difference between potential difference and current, we have quite a long way to go on our low carbon transition projects.

A more endemic problem is a blindness to the distinction between mass and weight, leading to a happy-go-lucky use of “kg” and “lb” where “N” and “lbf” would sometimes be more satisfactory.

In order to reduce our carbon footprint, we are looking to get rid of our home gas boiler, and I’ve found the heating profession to be fuzzy on the difference between energy (typically measured in kWh) and power (typically in kW). The brochure for a new kind of hot water tank quoted its heat loss rate as “Kw/hour”. The supplier was “an expert in all types of heating systems, with a particular interest in the transition to low carbon solutions”.

The same disease seems to affect the electric car population: “100 kWh rate of charge is the max (ish) you can expect under ideal conditions”.

The next example is probably an oversight rather than a lack of understanding: a prestigious journal quoted the cruising altitude of an aircraft as “30,000 lb”. Presumably, that should have been “lbf”.

Lastly, I have an example that goes back to my teens. I remember my physics teacher insisting that instruments should be labelled so as to be non-dimensional. Examples: a speedometer should be labelled “speed/kmh-1” and a range-finder as “range/m”. He asserted that every car tachometer in the universe has been mis-labelled (although they were only present on exotic cars back then). Mostly they say “rpm x 1000” instead of “engine speed/1000rpm”).

My father told the story of his friend who went to pick up a brand-new luxury car from the dealer – a journey of about 100 miles each way. The tachometer was labelled as “rpm x 100” (we know what that means) and marked out as “0”, “10”, “20” etc. The dealer told the friend not to exceed 50 miles per hour for the first 100 miles, otherwise the engine could be damaged. When the friend got home, there were burning smells and steam escaping from the engine, with alarming noises as it started to cool down. The friend had driven all the way home with the tachometer on 50.