Would your plane really crash if you switched on your mobile? And can a fork blow up a microwave? Simon Usborne puts technology myths to the test

Mobile phones can cause planes to crash, life-support machines to fail and petrol stations to blow up

For as long as mobile phones have existed, we have been told that there are certain places where we must not – under any circumstances – use them. We were told that mobiles could interfere with the computers that keep planes in the air, and that a simple call to say "we're just taking off" could trigger a disaster. Yet, last week, the UK telecoms regulator, Ofcom, confirmed it would allow mobiles to be used on UK-registered planes. So were those disastrous possibilities made up? And what does this mean for the other mobile phone bans? After all, we're also told that making calls on petrol station forecourts can trigger explosions, and that if we use them in hospitals, sensitive equipment, such as life-support systems, could fail.

"There is practically no evidence to say mobile phones pose a risk," says Dr Adam Burgess, sociology lecturer at Kent University and the author of Cellular Phones, Public Fears and a Culture of Precaution. In the case of hospitals, Burgess cites a 10-year-old study that found mobiles affected only 4 per cent of hospital equipment, only 0.1 per cent of it seriously. "And technology has moved on since then, so the risk today is even lower." What about exploding petrol stations? Are we really doomed if we send a text or make a call while filling up? Don't panic, says Dr Burgess, who believes the culture of precaution in the petroleum industry dates back to the 1988 Piper Alpha disaster. "But the risk from phones was always hypothetical," he says. "In America, there have been claims that explosions at petrol stations were down to mobiles. But the explosions have since been found to be caused by sparks from the static on peoples' clothes as they get out of their cars. The claims against mobiles are based on no evidence."

Verdict: myth – as far as we can tell. But don't go calling your stockbroker from the intensive care ward just yet.

Flatscreens are worse for your eyes than traditional monitors

It pains me to do the maths, but it's quite easy for an office worker to notch up 60 hours a week staring at a computer screen, whether deleting spam, fielding unwanted Facebook pokes at home or even getting something useful done. The College of Optometrists estimates each of us spends, on average, an astonishing three and a half months a year in front of one sort of screen or other.

"Our eyes were never designed to look at one thing for so long," says Keith Holland, an optometrist in Cheltenham. "They are built to move, change focus, and take in the periphery." It's no surprise, then, that too much screen time isn't great for your eyes. "Your blink rate goes down, which can lead to discomfort and spasms of the focal muscles," Holland explains. "In people with a family history of myopia, intensive screen work can bring on short-sightedness faster."

But what about claims that flat screens, which have all but consigned the old bulky cathode-ray tube monitors to the great scrapheap in the sky, can pose greater health risks? That's the message given out by one online firm, which is selling protective "office glasses". Flat-screen monitors, the company says, "radiate mercury frequencies... which make vision more difficult and show a damaging effect on metabolic processes in cell experiments." Should we be worried?

"It's a 100 per cent con," says Holland. "There's no evidence to back up these claims whatsoever – flat screens are not inherently dangerous."

Tim Hunter, an optometrist at a Leeds teaching hospital, says that, in fact, flatscreens are less damaging than many older cathode-ray monitors, which worked by redrawing the screen many times a second. Most people's minds had no problem putting the images together to form moving pictures, but some saw a flickering, which could lead to head-aches and, in extreme cases, even epileptic fits.

Verdict: it's a myth – flatscreens are generally better for you.

Airport security scanners cause pacemakers to malfunction

Removing our shoes and emptying our pockets as we're herded through airport security checks is a hassle. But what if your life depends on a metal gadget you can't throw into a little plastic tray? Are scanners potentially deadly to those who have artificial pacemakers?

In 2003, a German study published in the Journal of the American College of Cardiology showed no interference when 200 participants with pacemakers walked through standard airport security equipment.

But the British Heart Foundation tells patients not to pass through metal detectors. Cardiac nurse Judy O'Sullivan explains why: "Magnetic interference from airport scanners can change the speed setting of a pacemaker, which means it needs to be reset. It might make its wearer feel dizzy or could lead to palpitations." Pacemaker patients are advised to request a wand search, which should avoid the chest.

Verdict: It's true!



It's extremely dangerous to put any metal object into a microwave

Video-sharing websites are awash with clips of reckless youths loading the ubiquitous ovens with, variously, a light bulb (which lights up, then explodes), a propane-filled balloon (which blows both microwave and table to pieces) and a singing Furby toy (which ignites, goes quiet, then dies). But why do microwave manuals tell us never, ever, to stick metal in the microwave?

"The absorption of microwaves by metal is much higher than by food or liquid. That means metal gets very hot and an electric current builds up. These currents can lead to high voltages which can cause sparks to fly from the object to the microwave casing," says Damian Hampshire, a physics professor at Durham University. "The sparks can damage the electronic components in the magnetron – the device that turns mains electricity into microwaves."

Verdict: It may kill your microwave, but you will probably survive.

Even Apple Macs can catch viruses

As a loyal Windows user, I find there are few things more boring than listening to Apple evangelists harping on about the merits of their smarter, prettier Macs. In a recent ad, a smug Robert Webb, playing a Mac alongside David Mitchell's dowdy PC, made this claim: "I run Mac OS X, so you don't have to worry about the viruses and spyware [as] PCs do." The ad led to several complaints.

Clive Longbottom, a director at the IT analysts Quocirca, says it's wrong to say Macs don't get viruses. "They could; it's just that nobody can be bothered to write them. Worldwide, only about 3 per cent of desktop computers are Macs. At that level, it's not financially viable for hackers to write viruses for Macs."

Macs used to be more resistant, but times have changed and Mac users are complacent at their peril. As more PC users install antivirus software and Microsoft ups its game, hackers might turn their attention to Macs. It's probably time for Mac users to start thinking about antivirus software, such as McAfee.

Verdict: it's true – Mac fans beware.

Crooks can read bank details off your old PC, even if you've deleted them

Hit "delete" on an embarrassing photo, or your bank details, and they're erased from your computer for ever, right? Well, no – at least, not according to recent news reports warning that identity thieves can access deleted files from the hard drives of discarded computers.

Files are stored on a hard disk drive (HDD) – a spinning disk coated in magnetic material. A read-and-write arm passes over the disk, detecting the direction of the magnetic material, which is divided into tiny sections. One direction equals "0", the other equals "1" – and the binary codes represent all your files and photos. Hitting "delete" doesn't actually erase that code; it merely tags the disk space as available for new data. So data-recovery experts – or identity thieves – can still read the "deleted" information.

So how can we delete sensitive information? "By taking out your hard drive and hitting it with a hammer," says Rob Winter of data recovery firm Kroll Ontrack. "Another option is to use software that overwrites a random pattern of zeros or ones." Mac OS X lets you choose a "secure empty trash" option, which does exactly this. On a PC, software such as Wipe Drive will do the trick. The US Department of Defense orders that HDDs are shredded – or "degaussed", a process in which a magnet wipes the disk.

Verdict: It's true – but a hammer can solve the problem nicely.

You won't get the best sound from a CD unless you put it in a freezer first

Are CDs perfect? Can their sound quality be improved? One belief commonly held is that putting a CD in a freezer will make even the most mediocre popstrel sound better. Perhaps my ears deceive me, but when I stuck a colleague's copy of Passion, Geri Halliwell's fifth and least successful album, in the freezer overnight, she still sounded terrible the next morning.

Paul Drayson, a manager at a Japanese electronics firm's UK CD factory, is also sceptical. "It is possible that a poorly made plastic layer at the bottom of the disc could cause birefringence, or refraction of the light that hits the data layer, scrambling the sound. In theory, cooling the disc could improve the alignment of the plastic's polymer chains, making it clearer. But even if you did that, you would be making a bad disc good – you can't make a good disc better." Let's lay some other CD myths to rest, too. Can covering the surface in green ink improve sound? "Utter rubbish," Drayson says. Polishing it with a banana skin? "Well, standard polishing agents work better."

Verdict: myth – unless your CD's a dud.

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