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."

    任何年齡的兒童都會被天馬行空的童話所吸引。詛咒、魔法、還有英俊的王子充滿了童話世界。

    但是那些經典童話中的魔法在現實中真的可能上演嗎？基本物理學原理和最近的研究表明，讀者們認為虛幻的童話故事其實都源于現實生活。

    所以暫時停下你的想象，以一個核心科學家的角度審視下面幾個童話故事。

    長發公主

    格林童話中有一個故事叫《長發公主》。一個女巫將一名美麗的少女囚禁在高塔中。那名少女就是長發公主。她擁有一副好嗓子，更有長長的金發。一天，一個恰好經過樹林的王子聽見了她的歌聲。他們墜入了愛河。長發公主放下她那長發，讓王子順著長發爬到塔的頂端與她相見。這一連串的事件使讀者心生疑問。人類的頭發真的能承受一個人的重量嗎？

    一縷頭發平均能承受3.5盎司的重量，那相當于兩根棒棒糖的重量。暗色的頭發往往要比金發更厚，因而也更加堅韌。

    但是，遺憾的是，長發公主必須用她的金發。考慮到金發者一般有14萬根頭發，她的頭發應該可以輕而易舉地承受很多很多個王子的重量。然而，這個問題還沒有結束。

    如果長發公主剛將她的頭發放下王子就立刻攀爬的話，她的頭發就不會斷，但是，它很有可能會被拔掉。而且，她身體的其它部分也承受不了那么大的重量。值得慶幸的是，她有辦法減輕加在她頭上還有身體上的重量。

    美國大學華盛頓校區物理系助理教授Nathan Harshman表示，如果長發公主在頭發上綁上一些東西，那么她就會更安全。"基本想法就是，無論你綁上什么，你都可以利用頭發自身的摩擦力來承受王子的重量。"這比那長發公主的頭皮當錨點要好多了。

    小美人魚

    在迪士尼版的安徒生童話故事《小美人魚》中，愛麗兒（小美人魚）愛上了一位人類王子，請求女巫將自己變成人類。女巫同意了，但前提是愛麗兒獻出她的聲音。故事的很大一部分內容中，愛麗兒都不能說話。這造成了極大的麻煩，因為王子無法利用她迷人的聲音認出她來。后來，她恢復了自己的聲音并贏得了王子的愛。（與原著結局不同。）

    在故事中，愛麗兒因為一道詛咒而失去了聲音。但是，一個技術拙劣的女巫會用另外一種方法來使小美人魚沉默。科學家們發現了一種讓聲音在物體邊繞行的方法，這也能夠將聲音束縛在有限空間中。（這可以有效地阻止小美人魚的聲音被人聽到。）

    近日，杜克大學電子信息工程學院副教授Steve Cummer聲稱，從理論上這種聲音屏障是可造的。受到柏松亮斑的啟發，Cummer和他的合作者利用數學分析證明了聲波也能產生同樣的現象。他們證實了透聲波材料的存在性，利用這種材料，聲波能像未受任何阻擋一樣傳播，在臥室里的人可能輕而易舉地聽清客廳的對話，就像沒有墻存在一樣。

    一千零一夜

    飛毯是童話故事中最令人稱奇的物品之一。在很多童話中，包括一千零一夜，那些交錯縱橫的毯子讓人們穿行千里。飛毯是不可能存在的，是吧？

    三個科學家最近在《物理評論快報》日刊中發表了一篇文章。文中描述了一些毯子可以飛翔的條件。他們利用物理學基本原理來證明一塊毯子在空氣振蕩頻率合適的情況下是可以飛起來的，就像一張薄紙在掉落的時候緩緩飄落到地面一樣。他們的計算表明，快速而持續的微小空氣波動可以使毯子達到每秒一英尺（譯者：30.48厘米）的飛行速度。

    不要指望在近期看見阿拉丁非過你的頭頂，但是科學家們說他們所描述的條件是"在自然和技術允許范圍之內的".讓一張重毯子飛起來必定需要一個更強的發動機，我們的計算表明，飛毯將像千百年來一樣，繼續保持神秘，神奇和虛幻。

    也許一些童話故事更符合實際一些。也或許這些珍貴的故事都是按我們認為合理的方式發展的，只不過增加了想象的成分。也或許隨著科學近些年的快速發展，科學家們正在探尋物理世界以外的問題，有時也在孩子們的想象空間中尋找靈感。

    接下來會發生什么？科學家們或許會就什么溫度的粥最好喝引發一場辯論吧。