Biology Reference
In-Depth Information
CHAPTER
12
Those Magnificent Flying Machines: How Birds Fly
Who among us hasn't wondered at, and perhaps even envied, the shape-shifting robin
that one moment is hopping, two-legged, on the lawn and then suddenly jumps up,
opens its wings, pulls in those legs, and flies! In eighth-century Spain, Abbas Ibn
Firnas studied the dynamics of bird flight and carried out his own flying experiments.
In sixteenth-century Italy, Leonardo da Vinci invented several flying machines, again
closely studying the movements of birds.
Now we can take a jet to just about anywhere in the world, a feat impossible but
for the inspiration and understanding of physics that came from looking at birds. But
well over a millennium after the first human efforts at flight, we still watch flying
birds with wonder.
How Do They
Do
That?
Q How can birds stay up without flapping their wings?
A
Depending on the shape of the wings, some birds must flap to stay aloft whereas some
can glide or soar without flapping at all for many minutes or even hours.
Bird wings are shaped to form an
airfoil.
When a bird moves forward through the air,
the shape and curve of the wing cause the air to flow faster above the wing than below it.
Thefasterairabovelowersthepressure(drawingthebirdupward)whiletheslowerairbe-
low raises the pressure (pushing the bird upward). This force holding the bird up is called
lift
, and it requires that the bird be moving forward or facing into a fairly stiff wind.
