The Voyager Golden Records are phonograph records which were included aboard both Voyager spacecraft, which were launched in 1977. They contain sounds and images selected to portray the diversity of life and culture on Earth, and are intended for any intelligent extraterrestrial life form, or for future humans, who may find them.
As the probes are extremely small compared to the vastness of interstellar space, the probability of a space-faring civilization encountering them is very small, especially since the probes will eventually stop emitting electromagnetic radiation meant for communication.
The contents of the record were selected for NASA by a committee chaired by Carl Sagan of Cornell University. 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). To this they added musical selections from different cultures and eras, spoken greetings in 55 ancient and modern languages, and printed messages from US president Jimmy Carter and U.N. Secretary-General Kurt Waldheim.
The record is constructed of gold-plated copper. The record's cover is aluminium and electroplated upon it is an ultra-pure sample of the isotope uranium-238. Uranium-238 has a half-life of 4.468 billion years. It is possible (e.g. via mass-spectrometry) that a civilisation that encounters the record will be able to use the ratio of remaining uranium to daughter elements to determine the age of the record.
