A fly can do one thing extremely well: fly. Recently a team of British scientists de?鄄clared that the common housefly is the most talented aerodynamicist1 on the planet, superior to any bird, bat, or bee. A housefly can make six turns a second; hover; fly straight up, down, or backward; do somersaults2; land on the ceiling; and perform various other show-off maneuvers3. And it has a brain smaller than a sesame seed.
Michael Dickinson, who studies fly flight in his lab at Caltech, says the housefly isn’t actually the best flier. “Hoverflies are the be-all and end-all4,” he says. They can hover in one spot, hurtle through the air to another location, and then race back to their original hovering point—precisely.
Scientists, engineers, and military researchers want to know how creatures with such small brains can do that. Maybe they could reverse-engineer a fly to make a robotic device that could reconnoiter5 dangerous places, such as earthquake zones or collapsed mines.
Dickinson’s laboratory works with fruit flies. Re?鄄searchers put them in chambers and manipulate the visual field, filming the flies in super-slow motion, 6,000 frames a second. Dickinson is interested in knowing how flies avoid collisions. He has found that certain patterns, such as 90-degree turns, are triggered by visual cues and two equilibrium6 organs on their backs that function like a gyroscope7.
Flies have only a dozen muscles for maneuvering, but they’re loaded with sensors. In addition to their compound eyes, which permit panoramic imagery and are excellent at detecting motion, they have wind-sensitive hairs and antennae. They also have three light sensors, called ocelli, on the tops of their heads, which tell them which way is up. Roughly two-thirds of a fly’s entire nervous system is devoted to processing visual images. They take all this sensory data and boil it down to8 a few basic commands, such as “go left” and “go right.”
Imagine if you didn’t utter an opinion until you had read hundreds of books, magazines, newspaper articles, and blogs, and then issued a statement based on a few basic notions. That’s how a fly approaches flying. Only the fly is a speed reader. The information processing takes a fraction of a second9. Researcher Rafal Zbikowski of Cran?鄄field University in England, calls this mode of operation a “sensor-rich feedback control paradigm.”
Given that flies have evolved for hundreds of millions of years (and that they were the first animals to take to the air), we shouldn’t be surprised that they’re such good fliers. “They just don’t have brains like ours. Studying flies,” says Dickinson, “is like traveling to another planet.”
苍蝇最在行的就是飞行。最近有一组英国科学家宣称，普通家蝇是地球上最有天分的空气动力学家，没有任何一种鸟类、蝙蝠或蜜蜂可望其项背。家蝇可在一秒钟内转弯六次，能在空中盘旋、直上直下、向后飞、翻筋斗、停在天花板上，还能表演各种各样的耍帅动作，而它的大脑却不如一粒芝麻大。
加州理工学院在实验室研究苍蝇飞行的迈克尔•狄更生说，其实家蝇还不是最厉害的飞行家。他说：“食蚜蝇才是天下无敌。” 它们能定点盘旋，在空中直飞向另一个定点，再精确地冲回原来盘旋的地方。
科学家、工程师和军事研究人员都想知道，大脑如此之小的生物怎么能做到这些。也许他们能以还原工程的方式来解析苍蝇，进而制造出一种机器人装置，用来勘察地震区或塌陷矿场之类的危险区。
狄更生实验室的实验对象是果蝇。研究人员把果蝇放进隔间里，操控果蝇的视野，并以每秒6000格的超慢速度拍摄果蝇的动作。狄更生感兴趣的是苍蝇如何避免碰撞。他发现某种飞行模式，例如90度转弯，是由视觉信号以及背上两个功能类似陀螺仪的平衡器官触发的。
苍蝇能利用的肌肉只有12条，但感应器遍布全身，除了具有全景视角、侦查动作功能绝佳的复眼之外，还有对风敏感的毛与触角；此外，苍蝇头顶上还有三个作为光感应器的单眼，能辨别哪边是上面。苍蝇的整个神经系统大概有三分之二专门用来处理视觉影像。它们将收集到的全部感官数据归结为一些基本指令，譬如“向左”、“向右”。
想象一下，你要读过几百本书、杂志、新闻报道、博客之后，才根据一些基本概念发表意见。苍蝇就是这样处理飞行的，只不过它们懂得速读，处理信息只需一瞬间。英格兰克兰菲尔德大学的研究人员拉法尔•兹比考斯基把这种运作模式叫做“感应丰富的回馈控制典范”。
苍蝇已经演化了几亿年(也是第一种会飞的动物)，其飞行功力如此高超就不足为奇了。狄更生说: “它们只是没有像我们那样的大脑。研究苍蝇简直就像是到另一个星球上旅行。”
摘自 National Geographic， June 6, 2006
Notes:
1. aerodynamicist 空气动力学家
2. somersault 筋斗
3. maneuver 机动动作
4. be-all and end-all 最重要的部分，要义，主旨
5. reconnoiter 侦察，勘察
6. equilibrium 平衡，均衡
7. gyroscope 陀螺仪
8. boil ... down to 把……归结为
9. a fraction of a second 一秒钟的若干分之一, 一转眼的工夫 |
