The sounds of Earth
“How could you make an alien understand what it is like to be a human being on the planet earth?” This was the question posed to a committee of experts in 1977 before the launching of Voyager 1 and 2. The two American spacecraft were going to carry messages of greeting to any intelligent life form they might meet.
To many people’s surprise, experts decided that one of the best ways to communicate with an alien would be with music. So, they devoted 87 minutes of the Voyager video message discs to a selection of “the earth’s greatest hits”. Why choose music? Firstly, because the structure of music is based on numbers and musical harmony is easily analysed in mathematical terms. The scientists argued that as mathematics is the most universal of languages, aliens were more likely to understand the mathematical structure of our music than anything else about us. But the experts also felt that music expressed human feelings better than anything else and could represent the variety of human cultures best. There has never been a society without its own distinctive music to express its sadness and pain, its happiness and tranquillity.
The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. The selection of content for the record took almost a year. Sagan and his associates assembled 116 images and a variety of natural sounds, such as those made by surf, wind, thunder and animals (including the songs of birds and whales). The committee chose among other pieces, Aborigine songs from Australia, the Navaho Indians’ Night Chant and panpipes from Peru. They added Javanese music, bagpipes from Azerbaijan, a raga from India, bamboo flutes from Japan and percussion from Senegal. There were songs from Georgia, Zaire, Mexico, New Guinea and Bulgaria. There was also the jazz trumpeter Louis Armstrong performing Melancholy Blues and rock’n’roller Chuck Berry singing Johnny B. Goode. From the western classical tradition, they chose Renaissance music, three examples of Bach, two of Beethoven, an aria from Mozart’s The Magic Flute and Stravinsky’s The Rite of Spring. Were these really the earth’s greatest hits? At least they are some of the longest-lasting.
To this they added spoken greetings in 55 ancient and modern languages, and printed messages from U.S. president Jimmy Carter and U.N. Secretary-General Kurt Waldheim. The record also includes the inspirational message “Per aspera ad astra” in Morse code.
The disc, which was made of gold-plated copper, was built to last one billion years…
Images were also included. The collection of images includes many photographs and diagrams both in black and white, and color. The first images are of scientific interest, showing mathematical and physical quantities, the Solar System and its planets and human anatomy and reproduction. Care was taken to include not only pictures of humanity, but also some of animals, insects, plants and landscapes. Images of humanity depict a broad range of cultures. These images show food, architecture, and humans in portraits as well as going about their day-to-day lives. Some images contain indications of chemical composition. All measures used on the pictures are defined in the first few images using physical references that are likely to be consistent anywhere in the universe.
Voyager 1 was launched in 1977, passed the orbit of Pluto in 1990, and left the solar system in November 2004. In about 40,000 years, it and Voyager 2 will each come to within about 1.8 light-years of two separate stars. In March 2012, Voyager 1 was over 17.9 billion km from the Sun, while Voyager 2 was over 14.7 billion km away. Voyager 1 has entered the heliosheath. Of the eleven instruments carried on Voyager 1, five of them are still operational and continue to send back data today. It is expected that there will be insufficient energy to power any of the instruments beyond 2025. After that, the spacecraft will continue to traverse the Milky Way galaxy. On September 12, 2013, NASA announced that Voyager 1 had left the heliosheath and entered interstellar space, although it still remains within the Sun's gravitational sphere of influence.