Secret of Dolphins' Speed Disclosed

Scientists have finally determined how dolphins reach such great speeds. Researchers at the Rensselaer Polytechnic Institute of the United States have observed the movement of water around swimming dolphins. As a result of this investigation, they proved that dolphins can produce 400lb of force with the help of their tails.

This conclusion refutes completely the statement made by Sir James Gray, British zoologist who said in 1936 that dolphins were not strong enough to swim at high speeds as they couldn't overcome the drag. His theory didn't correspond to reality and was called "Gray's Paradox". As he explained it, the skin of dolphins contained certain properties that reduced the drag and allowed them to swim fast.

Professor Wei managed to find the missing part of this puzzle due to a new method that he initially worked out for measuring speed of Olympic swimmers. The method is based on Digital Particle Images Velocimetry showing the speed of water vibration around a dolphin or a human as they swim. This video-based technique is able to make about 1,000 frames per second.

"For the first time, I think we can safely say the puzzle is solved," said Tim Wei, head of the research. As he noted, dolphins have greater strength than Gray or other scientists could imagine.

Primo and Puka were the two dolphins that participated in the research. They were videotaped while swimming through a water area full of tiny bubbles. With the help of advanced computer software Wei managed to track the movement of bubbles. Each bubble was assigned a definite color which gave the possibility to determine not only their speed, but also direction. Thus researchers could measure the force produced by each dolphin. Scientists calculated that in the upright position when dolphins stayed above water they produced 400lb of force.

In order to create this technology, Professor Wei modified force measurement concepts from aerospace studies and combined them with the technique of water measurement, BBC News reports.

Gray's Paradox has been solved, but Professor Wei is not going to stop. Now he will continue studying other species of sea animals.

Source: http://news.bbc.co.uk/2/hi/science/nature/7748754.stm
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