Did you know: "echolocation"? This term was first introduced by Donald Redfield Griffin in 1944 when he demontrated the existence of the echolocation in bats. It is also called "biosonar" or active sonar. It is used by certain animals, such as: bat and dolphin. Bats and dolphins use echolocation to navigate in the dark when hunting preys. They use the echoes to locate, range and identify the objects in various environtments.

Echolocation employed not only in animals, but there is also human echolocation. It has been known and formally studied  at least since 1950s. It is the ability of humans to sense objects in their environtment by hearing echoes from those objects.This ability is used by some blind people to navigate within their environment by interpreting the sound waves reflected by nearby objects.
Echoes can give detailed information about location (where objects are), dimension (how big they are and their general shape), and density (how solid they are). Location is generally broken down into distance from the observer and direction (left/right, front/back, high/low). Dimension refers to the object's height (tall or short) and breadth (wide or narrow).

The Story of Ben Underwood - the boy who sees without eyes

Ben was born in Riverside California on January, 26th, 1992. At the age of two, he was diagnosed with Bilateral Retnoblastoma (retinal cancer in both his eyes). At the age of three, he had his eyes removed. 

But, destiny is a destiny. This young marvelous boy who has inspired so many people should leave us forever. At January 16th, 2009 he passed away in 16 years old because of cancer.
From him, we can learn how expensive and important are our eyes and our life. From him, we can get inspiration that we should never surrender and give up of any kinds of condition. From this video, we should learn something more ......