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THE LAST WORD

Strike actionIf I am swimming in an outdoor pool surrounded by tall trees, and a tropical thunderstorm breaks out, am I at an increased risk of being struck by lightning in the pool? And will it harm me?

n Lightning normally strikes tall objects, particularly when they stand on an otherwise flat and featureless landscape.

The base of a storm cloud is generally negatively charged, which, by repelling electrons, induces a positive charge on the ground below. An electric field is thus set up in the air sandwiched between the cloud and the ground. Lightning will take the path of least resistance but, if the cloud base and the ground are both flat, there is no obvious route for an electrical discharge.

Given that a tall object should increase the local electrical field strength, one might naively expect surrounding trees to act as decoys for a lightning strike. However, there are many other variables, not least the shape and height of the cloud base.

Water is a good electrical conductor so, when lightning strikes, the current tends to be confined to the surface and spreads out in all directions. This puts swimmers at risk and there are plenty of documented incidences of injury and death. For example, two out of a group of nine swimmers were seriously injured in waters off Chiba Prefecture, Japan, in 2005, after

a lightning strike. Perhaps they were far enough away from the point of impact to escape with their lives.

A typical swimming pool might not be sufficiently big to dissipate the energy associated with a lightning strike. In July 2006, Michael Haffenden was standing by the metal steps of the pool of a hilltop villa he had rented in Tuscany, Italy, for a family holiday. Tragically he was killed when lightning struck the pool, even though there would undoubtedly have been taller objects close by. Given that lightning is known to travel through plumbing, some experts even recommend staying out of indoor pools, baths or showers during electrical storms.

Leaving the pool is the best option when a storm is approaching. The trees would probably reduce the chances of the pool being struck but, given the finite size of a pool, a swimmer would be too close to the strike to avoid serious injury or death. If a storm arrived out of the blue and I could feel my hair standing on end, I would be tempted to duck under water and swim submerged to the edge of the pool, as far away as possible from any ladders that extend above the poolside.Mike FollowsWillenhall, West Midlands, UK

Turning to mushWhen I fry mushrooms in oil they quickly absorb all the liquid, making the pan quite dry. But after a couple of minutes they suddenly start to release it all again. What’s going on?

n In fields, mushrooms seemingly appear overnight, generally following damp conditions. This is because the mushroom, or fruiting body, draws in water rapidly from its mycelium within the soil to expand and appear above the surface as a mushroom. This means mushrooms contain about 90 per cent water and have very few calories.

What’s more, unlike plants, which have cell walls containing cellulose, the cell walls of fungi contain chitin. When mushrooms are fried in fat, the fat is initially absorbed into the chitin wall which, because of the heat, then ruptures to release the water that has been contained within the cells.

How one overcomes this problem of mush is a matter of debate. I have drained off the fluid and added double cream to the pan. A friend who teaches domestic science told me that one should immerse the mushrooms in a hot stock for a few seconds and then fry them. This way they do not go mushy. I tried this and she is correct. I assume that the hot stock causes the chitin wall to become more flexible so that it does not crack and release the internal fluid within at the time it is being fried.

Finally, if you are lucky enough to come across a giant puffball (Calvatia gigantea) while foraging, a slice fried in butter out-tastes any mushroom and never becomes mushy.Gillian CoatesAnglesey, UK

As ever with fungi, we advise readers to be absolutely sure of the species they have brought home before consuming it – Ed

“A typical swimming pool might not be sufficiently big to dissipate the energy associated with lightning”

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This week’s questions

LAne chAngerIn multi-lane traffic jams on the motorway, I often seem to move into the faster-moving lane just as it becomes stationary and the lane of traffic I just left starts moving. Assuming that other drivers experience the same, or are not deliberately trying to stymie me, what is the best strategy for getting through multi-lane traffic jams as quickly as possible? Peter SlessengerReading, Berkshire, UK

Ink bLobI’ve often noticed that after a biro pen has seen regular use, ink seems to coagulate at the nib, leaving thick deposits on paper that are easily smudged especially when you start using it again after a period of disuse. What is it that causes this to happen? Is it related to any of the chemicals used in the ink?R. Casterton By email, no address supplied

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