Some animals, like horses or cows, are actually buoyant on Earth—they float upside down. Birds are a different story. They can’t float but they can fly. A species of bird called the American Robin can float in water to more than 50 feet. But these are very small birds—just over the size of a pinhead.
When do levitation take place? The mechanism of levitation takes place by pushing the body down. The head moves downward because its upper wing is positioned lower than the lower wings—a phenomenon called vertical thrust. The entire body descends. Gravity is the force that holds the body in the air. If the body hits the ground faster than the velocity of sound, the bird is pulled up and upward until the body is horizontal and the speed of sound falls below zero and the animal floats. (Voltage is the force needed to keep the body in contact with the ground.) A pigeon that has just flown straight up can be pulled up so high for a few seconds that it is not visible on the sky.
The mechanism of how birds land is different. Instead of falling forward, the body is “stabilized” in a “tug of war” with gravity. For birds, as the gravity against the body does not change, it is not necessary to lift the body at high speeds until it hits the ground. “But,” says Dr. Tippett, “they have to stay airborne.”
Levitation makes birds very unique among terrestrial mammals
If that reasoning doesn’t convince your reader, this video, which the researchers described in the paper, can do just that. (The video is the second most viewed image on YouTube and gets more than 3.5 million views per month.) It shows birds being launched in free fall and then pulled up so high that their entire beaks touch the ground and their backs are turned. It’s not the most impressive, but it is entertaining and a fun look at the forces at play.
How does a bird make it so far up the tree? It’s a complicated process
When all is said and done, levitation is a big subject in terms of physics (as well as biology). “It’s not easy—it’s not rocket science. You really need somebody—a scientist with a physics background who comes up with some really interesting concepts and then you have to try it out. I don’t know anybody, personally,” says Dr. Tippett.
As far as how an
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