The Golden Record is a disc, fashioned after vinyl records, made of copper, plated in gold, packaged with a stylus and a needle, and is encased in an aluminum dust sleeve inscribed with basic listening instructions and mounted to the outside of the craft. It was designed and placed there by a team headed by Carl Sagan on the chance that alien civilizations could discover the craft and listen to the record. It is a slim hope, but it provides a time capsule proving the existence of humanity.
The disc contains a selection of recordings of earth sounds, greetings in several languages, and a cross-section of world music (including “Johnny B. Goode” from our country’s own Chuck Berry). Also encoded on the record is a set of rasterized images which, if the aliens decipher and follow the instructions on the dust sleeve, will show them various depictions of our culture and our planet. The first picture is of a circle, matching the circle on the dust sleeve, as a confirmation that they’ve correctly decoded the signal. Also among the pictures are: some primary scientific and mathematical principles to help understand the rest of the images; the location of our solar system in relation to 14 pulsars; the makeup and ordering of our solar system’s planetary bodies; the composition and structure of earth and its land masses; depictions of our basic evolutionary path; images of animals; scenes of human life, fetal development and human physiology. Really cool stuff.
Both probes are now in the thick of what’s called the “heliosheath“, which is an egg-shaped area around the solar system where all the particles that stream from the sun lose their velocity and come to a halt. The heliosheath is essentially where the momentum (which is mass times velocity, remember?) of the lightweight solar particles is not enough to push through the gasses that exist in the near-empty regions of space between stars. Anything that uses this solar wind of particles to accelerate through space will lose the speed assist but, due to Newtonian physics, will keep going forward if it’s heavy enough. Both of the probes are reporting that their velocity isn’t changing much, maybe slowing down a little, and that the compression of the solar particles around them in the sheath is raising the probes’ temperature slightly. Once the probes punch through this cloud in a few years, they will truly be the only man-made objects to go into intergalactic space.
However, although the probes are still powered up and running, 33 years after their 1977 launch (yeah, before we had desktop computers), they cannot remain operational forever. The plutonium fuel in their thermal reactors does have a half-life, and with that radioactive decay comes a reduction in power output. One by one, scientific instruments will have to be shut down in a carefully-planned sequence spanning over the next 15 years. It’s calculated that there will not be enough power to run the inertial gyroscopes, necessary for calibrating locational instruments and for aiming the large radio dish in the direction of Earth, by 2020. In order to keep the main electronics and radio running, the gyros will have to be shut down. It isn’t known how long radio communications will last after that point. The predicted final gasps of power are expected in 2025, when the reactors will cease to provide the power needed by the core electronics.
After a very, very long service life doing exactly what they were designed to do — survey the outer planets of our solar system with never-before-seen detail — with very few problems, they will then sail on into the black. By the time our extra-terrestrial friends find them (the nearest star system is over 4400 light years away) the spacecraft will have become electromagnetically-dark, lifeless metal husks; their reactor cores ice cold and turned into radioactively-stable byproducts. Then, hopefully, the aliens will find the records and hear the words of a hopeful, and hopefully still existent, planet.
“Greetings, from the children of the planet Earth.”