Why, you may wonder, should spiders be our friends? Because they destroy so many insects, and insects include some of the greatest enemies of the human race. Insects would make it impossible for us to live in the world; they would devour all our crops and kill our flocks and herds, if it were not for the protection we get from insect-eating animals. We owe a lot to the birds and beasts who eat insects but all of them putting together just kill only a fraction of the number destroyed by spiders. Moreover, unlike some of the other insect eaters, spiders never do the harm to us or our belongings.
Spiders are not insects, as many people think, nor even nearly related to them. One can tell the difference almost at a glance, for a spider always has eight legs and insect never more than six.
How many spiders are engaged in this work on our behalf? One authority on spiders made a census of the spiders in grass field in the south of England, and he estimated that there were more than 2,250,000 in one acre; that is something like 6,000,000 spiders of different kinds on a football pitch. Spiders are busy for at least half the year in killing insects. It is impossible to make more than the wildest guess at how many they kill, but they are hungry creatures, not content with only three meals a day. It has been estimated that the weight of all the insects destroyed by spiders in Britain in one year would be greater than the total weight of all the human beings in the country.
Indeed, the experiments have left many specialists unconvinced. The evidence for kite-lifting is non-existent, says Willeke Wendrich, an associate professor of Egyptology at the University of California, Los Angeles.
Others feel there is more of a case for the theory. Harnessing the wind would not have been a problem for accomplished sailors like the Egyptians. And they are known to have used wooden pulleys, which could have been made strong enough to bear the weight of massive blocks of stone. In addition, there is some physical evidence that the ancient Egyptians were interested in flight. A wooden artefact found on the step pyramid at Saqqara looks uncannily like a modern glider. Although it dates from several hundred years after the building of the pyramids, its sophistication suggests that the Egyptians might have been developing ideas of flight for a long time. And other ancient civilisations certainly knew about kites; as early as 1250 BC, the Chinese were using them to deliver messages and dump flaming debris on their foes.
The experiments might even have practical uses nowadays. There are plenty of places around the globe where people have no access to heavy machinery, but do know how to deal with wind, sailing and basic mechanical principles. Gharib has already been contacted by a civil engineer in Nicaragua, who wants to put up buildings with adobe roofs supported by concrete arches on a site that heavy equipment can not reach. His idea is to build the arches horizontally, then lift them into place using kites. We have given him some design hints, says Gharib. We have just waiting for him to report back. So whether they were actually used to build the pyramids or not, it seems that kites may make sensible construction tools in the 21 st century AD.
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The Egyptians had wooden pulleys which could lift large pieces of stones.
The evidence of kite-lifting is truly existent.
They knew how to use the energy of the wind from their skill as sailors.
The discovery on one pyramid of an object which resembled a glider suggests that they may have experimented with making flying machine.
5. The Chinese were using kites to deliver messages and dump flaming debris on their foes.
6. There are plenty of places around the world where people can not get heavy machinery.