Explained: The Physics-Defying Flight of the Bumblebee
A bumblebee cannot fly? That is what so many quotes say but it is a lie
according to Live science.
No, bumblebees can fly. The idea that they can't is a myth that
originated in the 1930s. Here are some reasons why bumblebees can fly:
Bumblebees flap their wings back and forth while also rotating them in a
figure-8 motion. This creates a dynamic stall above their wings that
produces lift. The angle of the bumblebee's wings creates vortices in the
air, similar to small hurricanes. The lower pressure in the eyes of these
vortices lifts the bumblebee upwards. Bumblebees have a special joint in
their wings that allows them to bend them in flight. When researchers
immobilized this joint, the amount of weight bumblebees could carry was
reduced by 8.5%. Bumblebees can rotate their wings up to 200 times per
second. This rotary motion is similar to the principle used by helicopters.
Bees have surprisingly fast colour vision, about 3 to 4 times faster
than that of humans depending on how it's measured, a new study finds. Short
and stubby, the bumblebee doesn't look very flight-worthy. Indeed, in the
1930s, French entomologist August Magnan even noted that the insect's
flight is actually impossible, a notion that has stuck in popular
consciousness since then. Now, you don't need to be a scientist to raise an
eyebrow at this assertion, but it sure is easier to explain the bumblebee's
physics-defying aerodynamics if you're Michael Dickinson, a professor of
biology and insect flight expert at the University of Washington.
"The whole question of how these little wings generate enough force
to keep the insect in the air is resolved," Dickinson told Life's Little
Mysteries. "There are details remaining, but it's just not an enigma
anymore." Dickinson published a 2005 study in the journal Proceedings of
the National Academy of Sciences on the flight of the bumblebee after
gathering data using high-speed photography of actual flying bees and force
sensors on a larger-than-life robotic bee wing flapping around in mineral
oil. He says the big misconception about insect flight and perhaps what
tripped up Magnan is the belief that bumblebees flap their wings up and
down. "Actually, with rare exceptions, they flap their wings back and
forth," Magnan said. Take your arm and put it out to your side, parallel to
the ground with your palm facing down. Now sweep your arm forward. When you
reach in front of you, pull your thumb up, so that you flip your arm over
and your palm is upwards. Now, with your palm up, sweep your arm back. When
you reach behind you, flip your hand over again, palm down for the forward
stroke. Repeat. If you gave your hand a slight tilt (so that it's not
completely parallel to the ground), Dickinson said, you'd be doing
something similar to a bug flap.
The fluid dynamics behind bumblebees' flight are different from
those that allow a plane to fly. An airplane's wing forces air down, which
in turn pushes the wing (and the plane it's attached to) upward. For bugs,
it isn't so simple. The wing sweeping is a bit like a partial spin of a
"somewhat crappy" helicopter propeller, Dickinson said, but the angle to
the wing also creates vortices in the airlike small hurricanes. The eyes of
those mini-hurricanes have lower pressure than the surrounding air, so
keeping those eddies of air above its wings helps the bee stay aloft.
Other studies have confirmed that bees can fly in one of the more
colourful projects, in 2001, a Chinese research team led by Lijiang Zeng of
Tsinghua University glued small pieces of glass to bees and then tracked
reflected light as they flew around in a laser array. But now, Dickinson
says, researchers are more interested in the finer points of how insects
control themselves once they're in the air. Those studies will be
especially important for a fleet of robotic insects in development,
including robot-bees created by a team at Harvard University.
K Rajaram IRS 151224
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