Thursday, February 18, 2010

How Can A Bumblebee Fly? - New Insights

Almost everyone has heard the story (probably meant to discredit science) of how scientists have calculated that the bumblebee cannot fly. All bumblebees, as everyone knows, can actually fly quite well.

Explanations of the origin of this humorous story vary, but it may be based on the principles of flight that apply to the earliest fixed-wing aircraft. In those early planes the weight that could be lifted was roughly proportional to the surface area of the wings. Now bumblebees, when compared to butterflies or locusts have rather small wings in proportion to the size of their bodies. Obviously, any comparison to a fixed wing aircraft is misleading.

Instead, bumblebee wings, as it turns out, seem to have more in common with helicopter blades than with airplane wings. Watch this short YouTube slow motion video to see the bee using its wings to fly up, down, sideways and even backwards as it navigates around a flower blossom - The wings beat, or oscillate at high frequency and those oscillations create a vortex (like a mini-tornado) in the air above the wing. The vortex produces considerably more lift than a fixed wing, thus allowing the bumblebee to escape the limitations of the Wright brothers' craft.

Like all bees, bumblebees have two wings on each side of the body. But the two wings on the same side are coupled together with a row of microscopic hooks so that they move as one. Using a wind tunnel and smoke streams, biologists at Oxford University have recently demonstrated that in flight the wings on one side operate independently of those on the other side - This means that the bee beats its way through the air, rather than gliding forward with a smoothly coordinated rowing or gliding motion.

The flight of the bumblebee may be inefficient, but it probably makes the insect much more manoeuverable, allowing it to turn quickly from one blossom to the next, and weave its way among flowers dangling close to each other. And they seldom fly far. Most foraging flights are less than 500 metres from the nest.

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