Voyager II's Gold Disc "Sounds of Earth"

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Voyager II's Gold Disc "Sounds of Earth"

Photograph

Date: August 20, 1977

Source: Voyager II's Gold Disc "Sounds of Earth." Time Life Pictures/Getty Images, 1977.

About the Author: Carl Sagan (1934–1996) was the producer of "Sounds of Earth." An astronomer, author, and educator, Sagan made exceptional contributions to the advancement of science education, public policy/government regulation of science and the environment, planetary exploration, Earth history, and exobiology. As the David Duncan Professor of Astronomy and Space Sciences and Director of the Laboratory for Planetary Studies at Cornell University, Sagan played an important role in the Mariner, Galileo, Viking, and Voyager spacecraft missions to the neighboring planets of Earth. During his professional career, Sagan was commonly considered the best science educator of the twentieth century. He casually but effectively communicated the intricacies of science so laypersons could easily understand.

INTRODUCTION

Voyager I and Voyager II are the names of two 1,820-pound (825-kilogram) U.S. spacecrafts that were launched from the National Aeronautics and Space Administration (NASA) Kennedy Space Center at Cape Canaveral, Florida on September 5, 1977 and August 20, 1977, respectively. Launched from Titan 3E-Centaur expendable rockets by NASA Mission Control flight controllers, each spacecraft was originally sent to explore (under the direction of scientists at the Jet Propulsion Laboratory in Pasadena, California) the planets of Jupiter and Saturn. However, due to enhanced reprogramming of its software, both probes were endowed with greater capabilities, so that Voyager II was able to research the other two giant outer planets (Neptune and Uranus). Both probes were given the ability to communicate while traveling into the interstellar space beyond the solar system.

A time capsule-like message, called "Sounds of Earth," was placed aboard both spacecrafts in order to communicate to any extraterrestrial civilization that might come across the spacecraft as they travel through the solar system and out to interstellar space. The message, which was contained within two identical 12-inch (30-centimeter) "golden records" made of a gold-plated copper, was carried onboard each spacecraft. Each record, along with a cartridge and needle, was protected in an aluminum jacket. A sample of uranium-238 was electroplated onto the cover in order to provide a reference for the extraterrestrials as to the time of manufacture (the half-life of uranium-238 is about 4.5 billion years).

The two-hour record contained many messages that described the diversity of life on Earth. The record, produced by Dr. Carl Sagan and a committee of associates, contained 115 images such as those of a seashore, Earth, tree toad, family, and chemical definition; and a variety of natural sounds such as those made by a bird, cricket, human kissing, brainwave, volcanic eruption, surf, thunder, whale-song, elephant, automobile gears, footsteps, heartbeats, and wind.

The record also included ninety-five minutes of musical selections from different societies and time periods, spoken greetings from people in fifty-five different languages representing most of the human population, and printed messages from U.S. President Jimmy Carter and United Nations Secretary-General Kurt Waldheim. The musical selections included a variety of selections such as the Bach Brandenberg Concerto Number Two, First Movement; an Australian Horn and Totem song; a Bulgarian Shepherdess Song "Izlel Delyo Hajdutin"; and Chuck Berry's "Johnny B. Goode." The spoken greetings included Akkadian (spoken in Sumer about six thousand years ago), Wu (a modern Chinese dialect), and Latin (the still-used language of ancient Rome).

PRIMARY SOURCE

VOYAGER II'S GOLD DISC "SOUNDS OF EARTH"

See primary source image.

SIGNIFICANCE

Upon exploration of the four large outer planets, along with their multiple moons, ring systems, and magnetic fields, the two Voyager spacecraft have significantly expanded the scientific knowledge of the solar system, specifically the knowledge of how Earth was formed and developed over time. The twin probes found that Jupiter has complicated dynamics within its twisting, turbulent atmosphere, including auroras, lightning, and storms three times the size of Earth itself. Voyager also discovered three new satellites (it has four large and many small moons). It was also learned that Jupiter has rings around it, with one thin, dusty ring that altered how scientists viewed the origins and mechanics of planetary ring systems. It was also discovered that Io, Jupiter's innermost major moon, has nine volcanoes—with eight of them still erupting—which dramatically affect the magnetosphere of its parent planet.

With regard to Saturn, an already-known ringed planet, Voyager found that it is encircled with a complex series of magnificent rings that contain kinks, spokes, and braids (which also forced scientists to rewrite theories about rings). In addition, both probes discovered four regular satellites and three shepherd satellites, which were predicted to exist (but never seen) in order to maintain ring stability. According to Voyager, Saturn has giant jet streams in its atmosphere, but its weather is relatively calm when compared with Jupiter's weather. Its satellite Titan has a smoggy atmosphere, while another satellite, Mimas, contains a gigantic impact crater.

Voyager II extended its planetary voyage and visited Uranus and Neptune, where ring systems around both planets—which were barely visible from Earth observations—were detected in great detail. Surprising to scientists was Uranus' highly slanted magnetic axis, which is nearly parallel to its axis of rotation, thus giving it an unusual magnetosphere. Its satellites of Ariel and Miranda contain icy channels that showed up like a weird patchwork. Voyager II discovered ten new regular satellites around Uranus (it currently has fifteen regular satellites), along with one new ring.

Neptune was found by Voyager II to contain very active weather, complete with abundant cloud features within its atmosphere. Voyager II showed dynamic weather (which was contrary to theories that showed passive weather since the planet received little sunlight) with winds blowing westward (opposite to the direction of rotation) and with speeds faster than winds on any other planet. Neptune also revealed for the first time what is now called its Great Dark Spot, a storm system similar to Jupiter's Great Red Spot but different in that it is smaller in size, eastwardly traveling, and circling the planet every sixteen hours. Voyager also found six new satellites (now bringing the total number of moons to eight, along with Nereid and Triton). Blue in color, the probe found that Neptune is encircled with scattered, dusty rings, finding two new rings around the planet. Voyager II found that Neptune's magnetic axis was also slanted.

As of 2005, Voyager I is expected to possess sufficient fuel to maintain contact with scientists on Earth until 2040, while Voyager II should have enough fuel until 2034. However, the extended missions of Voyager I and II have already rewritten much of the scientific knowledge of planetary astronomy. The mission of the twin probes has helped to resolve critical questions about the origin and evolution of the planetary systems within the solar system—including the Earth and her Moon—while modifying former elementary ideas of the formation and development of the solar system. The Voyager mission also raised new questions that will undoubtedly be answered with future missions within the solar system. Because of its ability to analyze four planets, Voyager also initiated a new field in science, that of the study of comparative planetology.

As of 2005, both spacecraft are flying near the outer boundary of the solar system—at a distance of between about 5 billion and 14 billion miles (8 billion and 23 billion kilometers) beyond the Sun. The Voyagers should reach the boundary sometime in the first twenty-five years of the twenty-first century. Voyager's last photographs of the solar system were a reverse look at the planets of the solar system, showing the emptiness that lies between the tiny planet called Earth and the gigantic expanse of the universe.