echoes

Have you ever spoken to the mountains, and received an answer in return? In Greek mythology, Echo is the name of an Oread, or mountain nymph, who was cursed by the goddess Hera to only repeat the words of others. An echo is a phenomenon of sound reflecting off a distant surface. The farther away the object, the more time it takes for the sound to return.

Many nocturnal and marine animals are sensitive to sound, and navigate, hunt, and forage by echolocation. Bats, dolphins, and whales emit sounds in a variety of ways and use echoes to identify the shape and location of different elements and creatures in the darkness of night and depths of the oceans. Sound travels faster through water than air, which makes “biological” sonar an efficient process.

Sonar, radar, and lidar are all contemporary technologies that use echoes to map things on earth that we can’t see, in essence giving a voice to the landscape. Sonar (Sound Navigation and Ranging) measures echoes from sound waves and is used to map the ocean floor. “Active” sonar has been known to cause acoustic trauma to whales, prompting legislation to curtail its use in certain regions. Radar uses radio waves to measure the size, quantity, speed, and direction of moving objects. Meteorologists predict weather patterns based on radar data from the interior of clouds. Lidar measures light reflected from laser pulses to accurately map the three-dimensional structure of the earth’s surface. Lidar can sense topographic features below a forest canopy and is an effective tool for environmental planning and landscape management.

Since time immemorial we call out to the land and listen for its wise response.