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No one knows exactly how the pyramids were built. Marcus Chown reckons the answer could be 'hanging in the air'.

没有人知道金字塔到底是怎么建成的。Marcus Chown料想答案可能是“悬空而造”。

The pyramids of Egypt were built more than three thousand years ago, and no one knows how. The conventional picture is that tens of thousands of slaves dragged stones on sledges. But there is no evidence to back this up. Now a Californian software consultant called Maureen Clemmons has suggested that kites might have been involved. While perusing a book on the monuments of Egypt, she noticed a hieroglyph that showed a row of men standing in odd postures. They were holding what looked like ropes that led, via some kind of mechanical system, to a giant bird in the sky. She wondered if perhaps the bird was actually a giant kite, and the men were using it to lift a heavy object.

埃及的金字塔是在3000多年前建造的，但是没有人知道它们是以何种方式建造的。传统的描述是由成千上万的奴隶拖动载有石头的雪橇来建造的。但是没有证据证明这一观点。加利福尼亚的软件顾问 Maureen Clemmom前提出在金字塔的建造过程中可能使用了风筝。在翻阅一本有关埃及古迹的书时，她发现一个象形文字描述的是一群人以奇怪的姿势站立。他们手里拉着类似绳索的东西，通过某种机械连着空中的一只巨鸟。她想知道那只巨鸟是否可能就是一只巨大的风筝，而那些人正用它来举起重物。

Intrigued, Clemmons contacted Morteza Gharib, aeronautics professor at the California Institute of Technology. He was fascinated by the idea. 'Coming from Iran, I have a keen interest in Middle Eastern science,' he says. He too was puzzled by the picture that had sparked Clemmons's interest. The object in the sky apparently had wings far too short and wide for a bird. 'The possibility certainly existed that it was a kite,' he says. And since he needed a summer project for his student Emilio Graff, investigating the possibility of using kites as heavy lifters seemed like a good idea.

好奇心驱使下的Clemmons联系了加州理工学院的航空学教授Morteza Gharib。后者对她的想法很感兴趣。他说：“我来自伊朗，对中东的科技有浓厚的兴趣。”他同样也对令Clemmons感兴趣的图片感到疑惑。悬在空中物体的两翼对于鸟类来说明显太短太宽。“是风筝的可能性确实是存在的，”他说。因为他刚好需要给学生Emilio Graff布置一项暑假研究计划，调查用风筝做起重器的可能性是一个好主意。

Gharib and Graff set themselves the task of raising a 4.5-metre stone column from horizontal to vertical, using no source of energy except the wind. Their initial calculations and scale-model wind-tunnel experiments convinced them they wouldn’t need a strong wind to lift the 33.5-tonne column. Even a modest force, if sustained over a long time, would do. The key was to use a pulley system that would magnify the applied force. So they rigged up a tent-shaped scaffold directly above the tip of the horizontal column, with pulleys suspended from the scaffold's apex. The idea was that as one end of the column rose, the base would roll across the ground on a trolley. Earlier this year, the team put Clemmons's unlikely theory to the test, using a 40-square-metre rectangular nylon sail. The kite lifted the column clean off the ground. We were absolutely stunned,' Gharib says. 'The instant the sail opened into the wind, a huge force was generated and the column was raised to the vertical in a mere 40 seconds.'

Gharib和Graff尝试只借助风力(除此之外没有其他能源)来把一块水平放置的4.5米长的石柱直立起来。最初的计算以及风洞模型实验让他们相信不用太强的风力就能举起这块33．5吨重的石柱。甚至只要风力适度，如果能维持一定的时间就能做到。关键是要用一个滑轮系统把使用的风力扩大。因此他们在横放的石柱顶部正上方搭了一个帐篷形的支架，在支架的顶部悬挂了滑车。理论是当石柱的一端被吊起，另一端就能顺着下面的手推车翻转过来。今年早些时候，他们用一块40平方米的方形尼龙风帆把Clemmons的空头理论付诸实验。最终风帆把石柱完全抬离地面。“我们完全目瞪口呆”Gharib说。“风帆在风中展开那一刻产生一股巨大的风力，仅花了40秒石柱就被抬离地面。”

The wind was blowing at a gentle 16 to 20 kilometres an hour, little more than half what they thought would be needed. What they had failed to reckon with was what happened when the kite was opened. 'There was a huge initial force- five times larger than the steady state force,' Gharib says. This jerk meant that kites could lift huge weights, Gharib realised. Even a 300-tonne column could have been lifted to the vertical with 40 or so men and four or five sails. So Clemmons was right: the pyramid builders could have used kites to lift massive stones into place. 'Whether they actually did is another matter,' Gharib says. There are no pictures showing the construction of the pyramids, so there is no way to tell what really happened. 'The evidence for using kites to move large stones is no better or worse than the evidence for the brute force method,' Gharib says.

当时的风力时速仅为16到2睨公里，还不足他们预想所需风力的一半。他们没有想到的是当风筝打开时会发生什么。“巨大的初始风力比恒稳状态风力大五倍，”Gharib说。他意识到这种猛然的拉力意味着风筝能够举起巨大的重量。只需40个左右的人力加上四五个风帆就能把一根300吨的石柱直立起来。所以 Clemmons是对的，金字塔的建造者们可能使用了风筝把巨大的石块抬升至指定位置。“他们是否真的使用了风筝是另外一回事，”Gharib说。没有图画描述金字塔的建造情况，所以没有办法知道真正发生的事情。“使用风筝搬运巨石的证据和使用强力法的证据不相上下，”Gharib说。

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.

事实上，这些实验许多专家并不信服。洛杉矶加州大学的埃及古物学副教授Willcke Wcndrich就说：“支持风筝搬运的证据并不存在”。

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.

其他人则认为支持该理论的实例不在少数。对像埃及人这样熟练的水手来说驾驭风力不是问题。而且我们都知道他们制造了坚同的木质滑车用以承运大块巨石。此外，有物证表明古埃及人对飞翔很感兴趣。在塞加拉的阶梯金字塔上发现的一块木制加工品就酷似现代的滑翔机。尽管它出现在金字塔建成儿百年后，但是它的精密程度却显示埃及人想要飞翔的想法已经非常久远。而其他古文明确实也了解风筝；早在公元前1250年，中国人就用它们来传递信息或向敌人倾倒燃烧的碎片。

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't reach. His idea is to build the arches horizontally, then lift them into place using kites. 'We've given him some design hints,' says Gharib. 'We're 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.

甚至现在这一实验可能还具有实用性。全世界很多地方的人们没有大型机械，却知道如何利用风能、航海和基本的机械原理。一位尼加拉瓜的土木工程师就联系了Gharib，想要在一个没有重型机械的地方建造用混凝土拱支持土坯屋顶的房子。他的想法是先在地平线上建造拱顶，然后用风筝抬升拱顶到预定位置。“我们给了他一些设计建议，还在等待他的反馈。”Gharib说。所以不管风筝有没有被用来建造金字塔，似乎它们在公元21世纪却可能是实用的建筑工具。