From: David A Gabel, ENN
Published January 24, 2012 09:23 AM

Finding Nature's Speed Limit

The speed of light is considered to be the limit at which no object can go faster. But here on Earth, nature has its own speed limit which affects its fastest creatures every day. The speed at which an animal can go, and human aircraft for that matter, is directly dependent upon how far that animal can see. Using complex mathematical equations, researchers at the Massachusetts Institute of Technology (MIT) have effectively quantified nature's speed limit. They found that given a certain density of obstacles, there exists a speed at which a bird can reasonably fly without collision.


The bird which was examined for the study was the northern goshawk, an insanely fast bird of prey. It speeds through dense forest canopies as it hunts small mammals and other birds. It has short broad wings and a long tail. Combined with razor sharp reflexes, it is able to avoid obstacles at very high speeds. The researchers aimed to find the theoretical speed limit for the goshawk to avoid crashing.

Of course, birds do not need a paper from MIT to tell them how fast they can go. Their instincts, shaped by thousands of years of evolution, can suffice. What the paper will affect is the development of aircraft, particularly unmanned aerial vehicles or UAV. The goal is to create a UAV that is fast and agile through cluttered environments such as forests, canyons, or cities.

At present, UAVs fly at low speeds because they are programmed to react to objects which their sensors detect. The northern goshawk flies in a much different way. Instead of reacting purely on objects it sees, it gauges the density of the trees or other obstacles. Using intuition, it knows the maximum speed allowable to successfully navigate through the openings.

The MIT researchers, led by Emilio Frazzoli, associate professor of aeronautics and astronautics, began by creating an equation to represent the bird's position at a given speed. They also created a model of a forest, representing various densities of trees. Through complex mathematical analysis, they found a critical speed at which a bird is sure to crash. Below this speed, the bird can reasonably fly without collision.

To further this line of research, Frazzoli is planning to test the human capacity for a natural speed limit. He and his students are developing a first person video game in which the people fly through a simulated forest at high speeds. Will man ever be able to match the reaction time of a hawk?

The MIT study has been accepted into the IEEE International Conference on Robotics and Automation.

For more information and video of goshawk in flight:

Goshawk image via Shutterstock

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