Friday 04 December 1998
Ants can carry up to 50 times their own body weight on their backs, and their pincers can grip something 1,400 times their weight. By contrast, even the strongest humans can lift only a few times their own weight.
Q How does the brain work?
The brain is far more complex than even the biggest supercomputers and there is still a lot we don't know about it. An average brain weighs 3lb (1.4kg) and contains about 100 billion nerve cells - about the same number as there are stars in the Milky Way. Each nerve cell has between 1,000 and 10,000 connections with other nerve cells, which are mediated by special chemicals. The number and pattern of connections in use at any one time depends on what we are doing. After the age of 20, our brains lose about 0.03 ounces (1 gram) in weight per year as nerve cells die and are not replaced. Luckily, some nerve cells duplicate tasks - so we don't lose function at once.
Q How do we hear sound waves?
The outer ear collects sounds which have been carried as pressure waves in the air. These waves make the eardrum (or tympanum) vibrate. Three small bones connected to the eardrum, called the ossicles, amplify the vibrations and pass them on to the cochlea. The cochlea looks like a snail and is filled with liquid and lined by super-sensitive hairs. When vibrations hit the cochlea, the liquid inside starts to move, causing some of the hairs to sway. The movement of the hairs activates nerves attached to their bases, sending electrical signals to the brain where they are decoded into voice patterns, music and so on.
Q What is the smallest bird?
The bee hummingbird, Mellisuga helenau, of Cuba and the Isle of Pines, measures about 2.5 inches long (57mm), half of which is taken up by the bill and tail, and weighs 0.05 ounces (1.6 grams). The females are slightly larger.
Q Why do the tails of comets look curved?
Comets in fact have two tails - ions, formed from charged particles forced off the "dirty snowball" of the surface, and dust, released as the ice melts on the approach to the Sun. The ion tail is straight, and usually points away from the Sun. It is the dust tail that is curved. The particles that comprise it vary in size and velocity of ejection. The smaller ones, about a micron in size, experience the additional effects of radiation pressure, a repulsive force that can change the particle's orbit around the Sun. Rather than being part of the main body of the comet, they are falling independently with their own momentum. The effect is that dust particles making up the tail are moving in different orbits, all similar to the comet's, but subtly different enough to give the characteristic curve.
Visit the Technoquest World Wide Web site at http://www.sciencenet.org.uk Questions and answers by Dial-a-Scientist on 0345 600444
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