Readers letters

How much should we care about SI units?

PE

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Surely the bottom line is that engineers need to understand systems for units

Why were Imperial Units used as regards article on Bloodhound Supersonic car? (PE January)

Reasons: 

  1. It's their car
  2. PE is no arbiter on these matters
  3. Massive US presence in aerospace
  4. Common sense 

Professor Escudier may well have read the article "with interest", with its regression to Imperial times, but to indicate that he "was horrified" seems to stretch the point a bit.

How much should we really care? Are we not overwhelmed by too much centralisation?

That TESCO is fully metric is no great surprise particularly as it is duty bound by boiler plate amounts of European Directives; non compliance for TESCO on any front, anywhere, would be tantamount to heresy and easy pickings for Trans-National Food / Safety / Health / Standards Agencies.

However, SAINSBURY'S reliably informs me on its designated TWO pint milk cartons that it is also 1.136 LIT. Clearly only partially metric cows. 

If Universities use SI; well jolly good. To be heroic now about Imperial Units would be too much. But to be stoic as regards SI is just plain tiresome.

As I can just about recall, the engines for the Anglo / French Concord(e) were designed / manufactured / tested in TWO sets of units - ostensibly

Imperial and SI, operating in parallel, all the time. That aeroplane was subject to truly ferocious coverage - political / economic / financial / technical / environmental / safety / social / accounting even? -  at that time. But the dual system of units appeared to escape all the odium. And the general public was quite impressed with the result.

Surely the bottom line is that Engineers need to understand systems for units. Clearly they have to understand SI. An Engineer - Pilot I know automatically thinks SI for the features - characteristics of jet engines, and equally automatically thinks Imperial whilst flying. Height is still in ft. And thrust can still be thought of in lbf.

William Ralph, Oxford

Next letter: The solar elephant

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