This article was originally published in the conversation (opens in a new tab) The publication contributed the article to Space.com Expert Voices: Commentary and Insights.
Alice Gorman (opens in a new tab)Associate Professor of Archeology and Spatial Studies, Flinders University
On August 20, 1977, 45 years ago, an extraordinary spacecraft left this planet on a journey like no other. Voyager 2 was going to show us, for the first time, what the outer planets of the solar system looked like close up. It was like sending a fly to New York City and asking for a report.
Voyager 1 was launched after Voyager 2 on September 5. On the flank of each Voyager was a golden disk that carried greetings, sounds, images and music from Earth.
The ships were more or less twins, but had different trajectories and different scientific instruments. While they both flew by Jupiter and Saturn, Voyager 1 advanced into interstellar space. Voyager 2 lingered to pay the only visit to the ice giants, Uranus and Neptune.
Gallery: Celebrate 45 years of Voyager with these amazing images of our solar system
The worlds of many colors
Upon arriving at Uranus in 1986, Voyager 2 mapped pale blue-green clouds and a possible “dark spot,” which was later confirmed by the Hubble Space Telescope. There was an unexpected magnetic field (opens in a new tab), which trailed a trail of corkscrew particles behind the planet as it orbited. ten new moons (opens in a new tab) were discovered, including Gray Puck and Crater (opens in a new tab)and two new carbon black rings.
Three years later, Voyager 2 reached Neptune and sent home images of cobalt-green clouds swirled by winds of up to 11,000 mph (18,000 km/h). A slate-colored “great dark spot” indicated a storm about the diameter of the Earth. The largest moon, Triton, was pink with methane ice and emitted geysers of frozen nitrogen (opens in a new tab).
No spacecraft has returned since.
Messages for the future
Even more than these glimpses of distant icy planets, what fascinates the people of the Voyager mission are the famous golden records. (opens in a new tab). A committee led by the visionary astronomer Carl Sagan worked for more than a year (opens in a new tab) to gather materials to represent planet Earth. The music gets the most attention as a “mixtape for the universe,” but it’s not the only standout.
One of the sounds of the Earth is the manufacture of stone tools (opens in a new tab), or “cut”. This is the most enduring technology that humans and their ancestors have devised, in use for about 3 million years (opens in a new tab) to this day. For most of human existence, the sound of stone striking stone to separate a sharp-edged cutting flake was heard daily in every community.
On the disc, you can hear the blows of the stone against the sound of the heartbeat.
In one of the 116 images, a black scientist in a lab coat bends over a microscope, tiered earrings falling gracefully from his ears. The earrings were the subject of some debate: would a future alien viewer recognize the concept of “jewelry”? This image was expected, along with the photomicrograph (opens in a new tab) of dividing cells in picture 17, would help viewers to find out that the science of microscopy was known on our planet.
People recorded messages in 55 languages (opens in a new tab). Some are ancient languages, like Akkadian (opens in a new tab) and Hittite, which was not heard on Earth for thousands of years. The most used words are “greetings”, “peace” and “friend”. The Portuguese greeting, spoken by Janet Sternberg, simply reads “Peace and happiness to all.”
The long goodbye
Finally, in 2018, Voyager 2 joined Voyager 1 beyond the heliopause, where the winds of interstellar space push back the solar wind. Our galaxy is 100,000 light-years across, and Voyager 2 is now just under 18 light-hours from Earth.
Both ships send reed signals that climb between the planets to the three antennas that are still listening: Tidbinbilla (opens in a new tab)Goldstone and Madrid.
Before they can actually leave, the Voyagers will have to travel through the Oort cloud, a vast, dark sphere of icy objects that surrounds the solar system, for another 20,000 years.
Voyager 2’s systems are slowly shutting down (opens in a new tab) to draw power as long as possible. But sometime in the 2030s there won’t be any left.
Even after Voyager 2 stops transmitting, it won’t be completely dead. The half-life of plutonium-238 in its nuclear power source is 87.7 years, while that of the small coating patch of uranium-238. (opens in a new tab) on the gold disc is 4.5 billion years. Both elements are slowly turning into lead.
The radioactive transmutation of the elements is a kind of reverse alchemy on a cosmic time scale. This transformation process will not end until there is nothing left on Voyager 2 to transform.
The constant bombardment of dust particles will gradually erode the surfaces of Voyager 2, probably at a higher rate than Voyager 1 because it is traveling through different regions of interstellar space. However, its gold record should be at least partially readable after 5 billion years.
The Earth portrayed on the Golden Discs will probably be unrecognizable even 100 years from now. The spacecraft and records will remain as a fragmentary archaeological record for the unknowable future.
While the gold records are endlessly fascinating, the true cultural significance of the Voyagers lies in their location. Spaceships are boundary markers that show the physical extent of human engagement with the universe.
When the Voyagers stop transmitting, it will be like losing your mind. Telescopes can only show us so much – there’s no substitute for being there.
Who will follow his path?
This article is republished from the conversation (opens in a new tab) under a Creative Commons license. read the original article.
Follow all Expert Voices topics and discussions (and be part of the discussion) on Facebook and Twitter. The views expressed are those of the author and do not necessarily reflect the views of the publisher.
#years #Voyager #billionyear #legacy #beginning