So sharp you won't cut yourself

Yes, I confess, this is a staged photograph. Our kitchen doesn't look like this though, if it were big enough and one of the corners could be veiled off, this is what you might see behind the curtain. It's all to do with that urban (domestic?) myth that you're more likely to injure yourself with a blunt knife than a sharp one. A dull knife means you need to exert more pressure and that pressure may get misdirected.

Our arsenal of sharpeners starts with the steel in the foreground. It was quite expensive and the blade is embedded with diamond dust. It's OK for toning up a knife that has merely lost its edge but it's not the device you'd use if, for urgent reasons, you needed to convert a butter knife into a carver.

To the right is a Carborundum stone held in a wooden frame. This is slowish but eminently controllable and I would use it to transform a really blunt knife if it were also necessary to maintain the appearance of the blade.

Finally the double grinding wheel with the non-optional safety glasses. Brush one side of the knife blade against the wheel for five seconds, then the other side. The device is ugly, surprisingly cheap, belongs in a workshop and is frighteningly efficient.

TECHNO-ART "Rififi" is a French burglary caper film that predates the word caper. Famous for the 15-minute passage without dialogue. It's particularly good on the technology of burglary. Entrance to the target room is made down through the ceiling and the thieves need a method of preventing debris from dropping on to the floor below and starting the burglar alarm. Simple - insert a folded umbrella through an initial small hole then open it up. Immobilise the burglar alarm? Squirt the contents of a fire extinguisher into it.

Don't need it, never have punctures

Can you say - hand on heart - what the pressure is in your car's spare tyre? I can't but then I don't have to. Over a decade ago I was given an electric pump that plugs into the car's cigarette lighter socket. It seemed like a utilitarian gift at the time but down the years I've used it a couple of dozen times.

Because otherwise a spare tyre can be a delusional form of re-assurance. Puncture in the middle of the Massif Central and a half-deflated replacement is only slightly more valuable than no tyre at all. Worse if you're tempted to use it in that state.

The pump has a further benefit. It's easier to bring tyres up to the correct pressure in your own driveway than on a harassed garage forecourt (where you may also have to pay for the privilege). It's not all gravy, however. The pump is noisy, in my case the car engine must be running and it seems to take an inordinate length of time to add 2 - 3 psi. Also, the gauge on the pump is not accurate enough and you need a separate traditional gauge. But it beats thumbing a lift.

Plaudits for a three-hander

TECHNO-ART Normally my Techno-Art bits are appended as two-sentence feuilletons to something bigger. But Michael Frayn's "Copenhagen" deserves a full-scale post.

I don't for a second understand atomic physics but - as with very difficult poetry, Ezra Pound say - I think I love its shape, its size, its sound or its very obscurity. The great thing about "Copenhagen" is that the hard stuff is at the very heart of the story. Bohr and Heisenberg have been wrestling with a third character, the atom, and they get to talk about how many rounds they think they have won. And they do this in the persuasively allusive language one might expect from professionals.

There are moral issues too but these are interwoven with the darkly fascinating study of what was then - perhaps still is - science's last barrier. On the whole, the theatre (other than masterpieces and then mainly Shakespeare) frequently disappoints me but not on this occasion. Nor did it disappoint my sister-in-law, who accompanied my wife and I, and who had never heard of "Copenhagen" before entering the theatre.

To get there, go by way of punctuation

SATNAV - PART TWO The technology may be imperfect but the achievement is huge. Nevertheless familiarity is the key to getting the best out of the system. Especially in France.

I was aiming for Villeneuve-sur-Lot. By the time I'd keyed in "Villen-" the predictive software had come up with Villeneuve. I accepted this, inserted a space and put in the "s" of "sur". Another prediction offered just two Villeneuve variations. Now anyone who knows France is well aware there are lots of Villeneuves. It took me a long time to realise that the machine was waiting for a hyphen.

Having spent most of my working life picking up such punctuative pedanticisms I might have been expected to appreciate this nicety. But the map I was using in conjunction with the satnav (when navigating always use all forms of assistance) spelled out the town name without hyphens.

I have since checked my big Michelin road atlas and hyphens are in. Which means it wasn't the technology that failed, rather the human cartographer who labelled the map. Also all this happened in France. I suspect that any reasonably Cartesian Frenchman would claim to be able to recognise V-s-L pronounced with and without hyphens.

Marvellous mathematical moment

Radios used to depend on valves (tubes in the USA). When switched on these glass cylinders glowed bright red. To the left is a hysteresis curve. Such curves show graphically how valves behave when they are doing their job. I’m flirting with your boredom here, but bear with me.

If you change the electrical values associated with the valve the shape of the curve changes. For me (an unwilling National Serviceman in the RAF) this was a half-opened window on how mathematics – so feared by liberal arts people (like me) – can not only describe the real world but to all intents and purposes is the real world.

Here’s a hint. The initial curve looks like part of a hill and – like a hill – has a gradient. Zoom in to a tiny part of the curve – so tiny it becomes a straight line. Incorporate that tiny line into a right-angled triangle. Does that light up a bulb? Pythagoras? Tall trees? Our long-lost friend trigonometry.

Fiddle with the values (angles, side lengths) of the triangle and the others change in an exact relationship. Simulating the effect of changing the electrical values associated with the valve. Using only paper and pencil (at least in those days – now we’d use a computer) we have designed an electrical circuit which will, for instance, help us amplify the tiny electrical signal picked up by the radio’s antenna so that it agitates a loudspeaker and we hear Messiaen’s Quartet for the End of Time. Or Amy Winehouse

Casserole arrives like royalty

Our Neff double oven (plus ceramic hob) cost a fortune and when we were asked whether we wanted the telescopic extension rails for the oven shelves - at a further £60-plus - we very nearly said no. Which would have been a terrible shame.

Now the pain of writing the enormous cheque has dulled we both feel it was money well spent. The two ovens do exactly what was claimed for them and the hob not only responds as quickly as any gas flame but can be cleaned in 20 secs. Nevertheless the real joy is the way the shelves glide in and out under mere finger pressure even when supporting a full-size Le Creuset filled to the brim with Irish stew. A perfect example of well-studied ergonomics - the science of ensuring an efficient relationship between the worker and his (or her) workplace.

Funny. I only owned one BMW (satisfyingly replaced by a Lexus) and the most memorable detail was the way the windscreen-wiper stalk worked. In a lesser car it would have been simply off and on. But in this case there was a tiny increase in pressure as it was switched. Difficult to explain but a genuine tactile pleasure.

Carving the impossible

To expand Stephen Fry's TV programme about Gutenberg they got a craftsman to build a replica of G's original printing press. This required him to carve a huge screw out of wood and both the end-product and the sawing/chiselling process were a delight to contemplate. But a screw is no use if it has no mirror-image to engage with and even the most adept carpenter would find it difficult to carve a thread on the inside surface of a hole. But those medieval woodsmiths knew a thing or two. Drill a pilot hole and introduce a shaft embedded with three metal blades. Rotate the shaft and, providing the measurements were correct, the female thread emerges. Voila!

TECHNO-ART You may not recall the name of the painting but chances are you'll recognise it when you see it. Totes Meer (Dead Sea) by Paul Nash is a moon-washed seascape cluttered with the wreckage of Luftwaffe planes. It's the authenticity of the latter that gives the painting its power and memorability.

Introducing two mega-stars

In seven very famous words ("Oh my America, my new found land.") Donne evokes the thrill of a distant country, creates a combined pun and metaphor and reports on his progress during a love-making session. Aso, unmistakably, he writes a line of poetry.

Georg Simon Ohm used only three symbols to formulate Ohm's Law: current equals voltage divided by resistance. Concise, easy to understand and still at the heart of virtually all forms of electrical activity. Circuit-breakers pop open (and fuses blow) in obedience to the law which also predicts that electric kettles will heat water. Houses may burst into flames because of a set of circumstances which the law explains.

I read Donne off my own bat (another Northern expression). The RAF forced me to learn the significance of Ohm's law. I'm lucky. Many people turn away from technical stuff thinking it to be too knotty - especially when there's maths in the offing. I did myself until the RAF revealed the range of punishments it kept in store for those who chose not to understand Ohm's law.

As I say, I'm lucky. To me Donne and Ohm are not in competition they're names in the same pantheon. And that's part of the reason for this blog.