And in the same, er, vein: from bottom detectors to whiffy chips. Another defence research lab, this time in the US, has announced the world's most sensitive scales. Capable of measuring amounts of stuff down to femptograms by wobbling nanotech rods around, they can also be made sensitive to particular compounds. Tiny scales may not sound very nasal, but that's exactly what noses do -- detect, isolate and measure minute amounts of airborne compounds. This might sound very twee, invoking images of robots skipping merrily along a rose-lined path, stopping from time to time to delicately inhale the heady scents of an English garden in full bloom. But for all their high-tech gee-wizardry, defence labs are there to do the work of governments. And governments want to sniff us to make sure we haven't been doing anything displeasing to them: explosives, drugs, DNA from the wrong place, that sort of thing. With automated noses this sensitive, you might think we'd be heading for an age where naughty powders and things that go bang will no longer be able to pass any sort of checkpoint. Experience suggests it won't work: there are plenty of tales of drug smugglers wandering down the aisle of the plane surreptitiously shedding small amounts of contraband either side so that everyone triggers the sniffer dogs. And then there are the playing cards that smell like explosives. All that will happen is that the powers of law and order will get into an expensive and futile arms race with the big boys, with plenty of collateral damage among the hapless and innocent. And this will happen: I'd put money on it. Ten dollars, in fact. That one there, the one I brought back from San Francisco which -- like most banknotes in the US -- probably has detectable amounts of cocaine on it. I'm going to use my own nanotechnology nose for a far more acceptable drug: this weekend is to be spent in Edinburgh and Glasgow, with a fair amount of sniffing, schooshing and swallowing some of Scotland's more famous product. Chin-chin! Click here to see more of Rupert's diaries.