Science: Technoquest - Ant death/Whale breath/Hot glass/ Hairy hearing

Questions for this column may be submitted via e-mail to sci.net@campus .bt.com

Q When I squash ants on the kitchen shelf and drop them on the floor, they are cleared away by other ants.Why? Are they eaten? (asked by Luela Palmer)

Most social insects have a well-documented behaviour called necrophoresis which involves the recognition and removal from the nest of dead nest- mates and other decomposing materials. Worker ants recognise the corpses by a number of chemical breakdown products: research by E.O. Wilson, the famous myremecologist (studier of ants), showed that if the "dead ant" chemical is sprayed on a live ant, workers will quickly carry it out of the nest, just as they would a corpse. The live ant then cleans itself off quickly and re-enters the nest - sometimes to be removed a second or third time if they haven't cleaned themselves properly!

Q Why don't whales get the bends?

The simple answer is that they are breath-hold divers, and do not breathe compressed gas at depth like scuba divers. Hence there is less nitrogen available for absorption and what there is was taken in at atmospheric pressure. However, it is more complicated than that. Human breath-hold divers can get the bends through repeated, relatively shallow (20-metre) dives. Dolphins diving below about 70 metres are protected by alveolar collapse - the tiny sacs in the lungs purposely shrink - which prevents gaseous exchange taking place. But the mechanism by which whales avoid the bends on shallower diving schedules is not completely understood.

Q Is it true that swimming pool water can make bleached hair go green?

Yes, it is possible. The peroxide used to bleach hair damages it which makes it more susceptible to collecting impurities such as iron and copper ions from the water. These ions can cause discolouration of the hair.

Q How long does it take for the alcohol in a drink to reach your bloodstream?

On average it takes 20 minutes for alcohol to reach the bloodstream after the first drink, and then approximately 1 hour per unit after this. This varies per person depending on their tolerance to alcohol, of course.

Q How many hairs are there in a human cochlea?

The cochlea, a bit of the ear that helps us hear, has about 15, 500 separate tiny hairs that wave from side to side sending signals to our brains.

Q How is ovenproof glass made?

To make glass tough enough to withstand the high temperatures in cookers, a chemical called boron oxide is added. This also makes the glass resistant to fast temperature changes.

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