Kids of any age love to read fairy tales because the storyline never limits the possibility that anything could happen. Curses, spells, and handsome princes reign in worlds beyond the reader's imagination.

    But are the most magical moments from some of our favorite stories actually possible? Basic physical principles and recent scientific research suggest that what readers might mistake for fantasies and exaggeration could be rooted in reality.

    So suspend your imagination for a moment, and look at the following fairy tales as a hard-core scientist might.

    Rapunzel

    In the Brothers Grimm story of Rapunzel, a witch holds a beautiful young woman captive in a tower. Rapunzel is blessed with a lovely singing voice and long, long blond hair. One day, her voice enchants a prince passing through a nearby forest. They fall in love, and Rapunzel lets down her hair so that the prince may use it to climb the tower to meet her. This chain of events begs readers to ask a question. Can human hair support the weight of another person?

    On average one strand of hair can support about three and one-half ounces, or about the weight of two candy bars. Each strand of dark hair is generally thicker, and therefore stronger, than blond hair.

    But, alas, Rapunzel must make do with blond locks. Given that blondes generally have about 140,000 hairs on their heads, her hair should easily support the weight of many, many princes. However, there is more to this story.

    If Rapunzel simply let down her hair and the prince started climbing immediately, her hair would not break, but it might rip out. Also, the rest of her body might not be able to support the weight. Thankfully, there are strategies that she can use to help reduce the strain on her head and body.

    Nathan Harshman, Assistant Professor of Physics at American University in Washington, DC, suggests Rapunzel would be safer and more secure if she tied her hair around something before lowering it. "The whole idea is that you can use the friction of the hair against itself in the knot, and whatever it is tied around will support the weight of the prince." That is a much better idea than making Rapunzel's scalp the anchor point.

    The Little Mermaid

    In the Disney version of Hans Christian Andersen's The Little Mermaid, Ariel （the mermaid） asks a witch to make her human because she has fallen in love with a human prince. The witch bargains with Ariel and takes her voice in exchange for performing the transformation. For a considerable part of the story Ariel cannot speak, which is a problem because the prince can only recognize her by her incredibly beautiful singing voice. Later, she recovers her voice and wins the love of the prince （sorry to spoil the ending）.

    In the story, Ariel loses her voice because of a curse. However, a less skilled sorceress could use a different method to silence a singing mermaid. Scientists have figured out a way to bend sound waves around an object and, can even prevent the escape of all sounds created inside a given area （important for keeping a transformed, singing mermaid from being heard）.

    Recently, Steve Cummer, Associate Professor of Electrical and Computer Engineering at Duke University announced that it is theoretically possible to create such a sound shield. Building on research demonstrating how light waves can be bent around an object to make it appear invisible, Cummer and his collaborators used mathematical analysis to show how to do the same thing with sound. They established that it is possible to create a material that bends sound waves around walls, pillars, or any enclosed area, where the sound waves emerge as if nothing had been in their way. It would be like someone in the bedroom being able to hear what someone in the living room said, but as if there were no wall between them.

    A side effect of this discovery is that sound waves generated inside the enclosed area would never escape. If the witch had been extremely clever, she could have built this material, and there would have been no need for a curse. Or maybe she did, and a transparent sound shield based on these principles was what enveloped Ariel until her love for the Prince melted it away, finally releasing her melodious voice for the Prince to hear.

    1,001 Arabian Nights

    One of the most exciting objects found in fairy tales is the flying carpet. In tales from a wide variety of cultures, including 1,001 Arabian Nights, these tangled tapestries take flight to carry people vast distances. Flying carpets are clearly impossible, right?

    Three scientists recently published a paper in the journal Physical Review Letters showing that there are conditions under which a carpet could fly. They used the basic laws of physics to show that a small, thin carpet could fly if the air were vibrating at the right frequency, much like how a piece of tissue paper floats softly to the ground when it is dropped. Their calculations showed that small waves of air in repeated fast pulses could steer a carpet at a speed of around one foot per second.

    Don't expect to see Aladdin flying by anytime soon, but the scientists write that all of their conditions "are within the realm of possibilities in nature and in technology. Making a heavy carpet fly would, of course, require a much more powerful engine, and our

    [calculations] suggest it will remain in the magical, mystical, and virtual realm as it has existed for millennia."

    Perhaps some fairy tales are more grounded in reality than others. Or maybe these precious stories are exactly what we thought they were. An idea is fertilized by the imagination and expanded beyond what seems possible. Or maybe science has come so far over the years that scientists are looking beyond the problems of the physical world and into the imaginations of children for their inspiration.

    What could be next? Perhaps a scientific debate over the temperature at which porridge is considered "just right."

    任何年龄的儿童都会被天马行空的童话所吸引。诅咒、魔法、还有英俊的王子充满了童话世界。

    但是那些经典童话中的魔法在现实中真的可能上演吗？基本物理学原理和最近的研究表明，读者们认为虚幻的童话故事其实都源于现实生活。

    所以暂时停下你的想象，以一个核心科学家的角度审视下面几个童话故事。

    长发公主

    格林童话中有一个故事叫《长发公主》。一个女巫将一名美丽的少女囚禁在高塔中。那名少女就是长发公主。她拥有一副好嗓子，更有长长的金发。一天，一个恰好经过树林的王子听见了她的歌声。他们坠入了爱河。长发公主放下她那长发，让王子顺着长发爬到塔的顶端与她相见。这一连串的事件使读者心生疑问。人类的头发真的能承受一个人的重量吗？

    一缕头发平均能承受3.5盎司的重量，那相当于两根棒棒糖的重量。暗色的头发往往要比金发更厚，因而也更加坚韧。

    但是，遗憾的是，长发公主必须用她的金发。考虑到金发者一般有14万根头发，她的头发应该可以轻而易举地承受很多很多个王子的重量。然而，这个问题还没有结束。

    如果长发公主刚将她的头发放下王子就立刻攀爬的话，她的头发就不会断，但是，它很有可能会被拔掉。而且，她身体的其它部分也承受不了那么大的重量。值得庆幸的是，她有办法减轻加在她头上还有身体上的重量。

    美国大学华盛顿校区物理系助理教授Nathan Harshman表示，如果长发公主在头发上绑上一些东西，那么她就会更安全。"基本想法就是，无论你绑上什么，你都可以利用头发自身的摩擦力来承受王子的重量。"这比那长发公主的头皮当锚点要好多了。

    小美人鱼

    在迪士尼版的安徒生童话故事《小美人鱼》中，爱丽儿（小美人鱼）爱上了一位人类王子，请求女巫将自己变成人类。女巫同意了，但前提是爱丽儿献出她的声音。故事的很大一部分内容中，爱丽儿都不能说话。这造成了极大的麻烦，因为王子无法利用她迷人的声音认出她来。后来，她恢复了自己的声音并赢得了王子的爱。（与原着结局不同。）

    在故事中，爱丽儿因为一道诅咒而失去了声音。但是，一个技术拙劣的女巫会用另外一种方法来使小美人鱼沉默。科学家们发现了一种让声音在物体边绕行的方法，这也能够将声音束缚在有限空间中。（这可以有效地阻止小美人鱼的声音被人听到。）

    近日，杜克大学电子信息工程学院副教授Steve Cummer声称，从理论上这种声音屏障是可造的。受到柏松亮斑的启发，Cummer和他的合作者利用数学分析证明了声波也能产生同样的现象。他们证实了透声波材料的存在性，利用这种材料，声波能像未受任何阻挡一样传播，在卧室里的人可能轻而易举地听清客厅的对话，就像没有墙存在一样。

    一千零一夜

    飞毯是童话故事中最令人称奇的物品之一。在很多童话中，包括一千零一夜，那些交错纵横的毯子让人们穿行千里。飞毯是不可能存在的，是吧？

    三个科学家最近在《物理评论快报》日刊中发表了一篇文章。文中描述了一些毯子可以飞翔的条件。他们利用物理学基本原理来证明一块毯子在空气振荡频率合适的情况下是可以飞起来的，就像一张薄纸在掉落的时候缓缓飘落到地面一样。他们的计算表明，快速而持续的微小空气波动可以使毯子达到每秒一英尺（译者：30.48厘米）的飞行速度。

    不要指望在近期看见阿拉丁非过你的头顶，但是科学家们说他们所描述的条件是"在自然和技术允许范围之内的".让一张重毯子飞起来必定需要一个更强的发动机，我们的计算表明，飞毯将像千百年来一样，继续保持神秘，神奇和虚幻。

    也许一些童话故事更符合实际一些。也或许这些珍贵的故事都是按我们认为合理的方式发展的，只不过增加了想象的成分。也或许随着科学近些年的快速发展，科学家们正在探寻物理世界以外的问题，有时也在孩子们的想象空间中寻找灵感。

    接下来会发生什么？科学家们或许会就什么温度的粥最好喝引发一场辩论吧。