The BBC go out of their way to avoid having to express any factual measurements. The space the miners are sheltering in is described as ‘the size of a 1 bedroom apartment (its described on their news website as 50 square metres). The escape tunnel that is being drilled is described on the TV news as being ‘the size of a bicycle wheel’! in fact its 65 cm!

This dumbing down of facts is endemic on the BBC. It doesn’t have an official view on metric any more, leaving presenters to use what they feel is appropriate and that they feel comfortable with. One of the flagship programmes is ‘Top Gear’ with the straight talking Jeremy Clarkson and his chums frequently referring to the Imperial system – any reference to metric is usually with some snide comment about Napolean!

I do believe that all factual broadcasting should use metric measurments and was most pleased to hear metric used throughout a programme on trains by Dan Cruickshank on Channel 5. The Discovery Channel use metric throughout – even on a broadcast last night explaining how weighing machines were made. The footage that was being referred to was by the metric narrative was actually regarding the assembly of USC weighing machines in the USA!

Finally, my partners’ 21 year old cousin has recently had a baby, and was asking today how much 110g was in lbs! I do despair of this obsession with babies weight in Imperial measures – but fear its because its the only way that people feel that they can make their babies measurements understood and ‘meaningful’ to others.

Some criticise the metric system by suggesting that its simplicity has the same deskilling effect as calculators alledgedly do for mental arithmetic. This can be countered by pointing out that its logical simplicty has the effect of improving understanding by reducing the concept to its essentials. This is not the same as masking it by using a device to do the work for you.

We all want to see changes to tackle the problems referred to in earlier comments. But getting rid of the unnecessary two-systems muddle is a simple and practicable first step. There is no excuse for ignoring it.

We should definitely take advantage of the coherence of the SI to promote a deeper and genuine understanding of the physical world.

I think you have hit on a key, but it is not just calculators.

When I was educated, we had to write out the work and it had to include units. Including the units allowed “units analysis” which helped greatly in knowing when to divide and when to multiply.

Calculators only handle the numeric part of a quantity, and are part of the problem. However the problem has at least two more elements:
*Improper instruction (and checking of the student’s work)
*At least in the US, the pressure for national or standardized testing has pushed most tests to multiple choice. Method doesn’t count, only the answer, because only the answer is seen (by a computer looking at spots on a paper).

I learned in the slide rule era, and had to rough out a problem to “almost one significant figure” to get the order of magnitude. The slide rule would then give me three figures. Still, I DON’T want to go back to that, but something has been lost from the methods of instruction.

In my opinion, though, a major part of the problem is nothing to do with units themselves, but simply overuse of calculators. Students are now so dependent on them that they will often use them for absurdly simple calculations: on one occasion, I watched in bemusement as one A-Leve chemistry student searched futilely in their bag for their calculator when a question required them to divide 240 by 40. Because of this calculator-dependence, they’re not in the habit of writing out solutions to numerical questions step-by-step, even though this would ensure full method marks in exams (and it’s all about exams these days!). Not only does this allow rounding errors to creep in, but students don’t become properly proficient at manipulating units, and often fail to spot barn-door mistakes like unit inconsistencies in their equations.

The irony is that SI units are so simple to manipulate that this sort of problem should never arise – and I don’t think it would arise so often if students had to write out their calculations.