Of course, people can fly in an airplane, but I guess you wonder why we can't fly like birds.
First of all, we don't have wings. Even if we built some wings and strapped them to our arms, we wouldn't be strong enough to flap the wings and fly.
bird's body is very specialized for flying. It is extremely light and most of the muscles are for flying. We have strong legs for walking but they wouldn't help for flying. A bird has tiny little legs compared to the rest of it's body.
Even the bones in a bird are special. The bones are light in weight. Many of them are hollow and filled with air. In large soaring birds some of the hollow bones have internal braces like the struts in airplane wings. The frigate bird's wings measure 7 feet (2 meters) from tip to tip yet its skeleton weighs only 4 ounces (113 grams). This is less than the weight of its feathers.
A bird's skeleton must be light so it doesn't weigh the bird down, yet strong enough to stand the strain of flying.
- The bones are thin and hollow, making them very lightweight.
- The hollow wing bones of large birds have inner braces called struts that keep the bone strong, yet light.
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