Bats are not the only creatures to face this difficulty today.
Fireflies and some fish have the power to manufacture their own light, but the process seems to consume a large amount of energy.
However, using light to find one’s own way around requires vastly more energy, since the eyes have to detect the tiny fraction of the light that bounces off each part of the scene.
Plenty of other modern animals make their living in conditions where seeing is difficult or impossible.
Blind people, without even being aware of the fact, are actually suing echoes of their own footsteps and of other sounds, to sense the presence of obstacles.
The Sonar and ‘Radar’ pioneers didn’t know it then, but all the world now knows that bats, or rather natural selection working on bats, had perfected the system tens of millions of years earlier, and their radar achieves feats of detection and navigation that would strike an engineer dumb with admiration.
The American zoologist Donald Griffin, who was largely responsible for the discovery of sonar in bats, coined the term ’echolocation’ to cover both sonar and radar, whether used by animals or human instruments.
Only after the mysterious mass extinction of the dinosaurs about 65 million years ago were our ancestors able to emerge into the daylight in any substantial numbers.
As towns gradually expanded, water was brought from increasingly remote sources, leading to sophisticated engineering efforts such a dams and aqueducts.
Unprecedented construction of tens of thousands of monumental engineering projects designed to control floods, protect clean water supplies, and provide water for irrigation and hydropower brought great benefits to hundreds of millions of people.
Nearly one fifth of all the electricity generated worldwide is produced by turbines spun by the power of falling water.
There is a dark side to this picture: despite our progress, half of the world’s population still suffers, with water serviced inferior to those available to the ancient Greeks and Romans.
The consequences of our water policies extend beyond jeopardizing human health.
Nevertheless, it may be the only way to address successfully the pressing problems of providing everyone with clean water to drink, adequate water to grow food and a life free from preventable water-related illness.
As a result, the pressure to build new water infrastructures has diminished over the past two decades.
Although population, industrial output and economic productivity have continued to soar in developed nations, the rate at which withdraw water from aquifers, rivers and lakes has slowed.
On the other hand, dams, aqueducts and other kinds of infrastructure will still have to be built, particularly in developing countries where basic human needs have not been met.
Educating Psyche by Bernie Neville is a book which looks at radical new approaches to learning, describing the effects of emotion, imagination and the unconscious on learning.
One theory discussed in the book is that proposed by George Lozanov, which focuses on the power of suggestion.
Lozanov’s instrumental technique is based on the evidence that the connections made in brain through unconscious processing are more durable than those made through conscious processing.
Such methods are not unusual in language teaching.
What is distinctive in the suggestopedic method is that they are devoted entirely to assisting recall.
The teacher’s task is to assist the students to apply what they have learned paraconsciously, and in doing so to make it easily accessible to consciousness.
It was only thirty years ago that the building industry felt confident enough to erect office blocks of steel and reinforced concrete hat had more than a dozen floors.
With its special shock absorbers to dampen the effect of sudden sideways movements form an earthquake, the thirty-six-storey Kasumgaseki building in central Tokyo-Japan’s first skyscraper- was considered a masterpiece of modern engineering when it was built in 1968.
Yet in 826, with only pegs and wedges to keep his wooden structure upright, the master builder Kobodaishi had no hesitation in sending his majestic Toji pagoda soaring fifty-five metres into the sky- nearly half as high as the Kasumigaseki skyscraper built some eleven centuries later.
The best way to understand the shinbashira’s role is to watch a video made by shuzo Ishida, a structural engineer at Kyoto Institute of Technology.
The bigger the mass at each end of the pole, the easier it is for the tightrope walker to maintain his or her balance.
Mr. Ishida, known to his students as ‘Professor Pagoda’ because of his passion to understand the pagoda, has built a series of models and tested them on a ‘shake-table’ in his laboratory.
In a land swept by typhoons and shaken by earthquakes, how have Japan’s tallest and seemingly flimsiest old buildings-500 or so wooden pagodas- remained standing for centuries?