Voyager and SETI: Looking for Universal Messages


By Steven Gimbel, Ph.D.Gettysburg College

Scientists seem to agree that finding extraterrestrial intelligence is important as they’ve worked in several different ways to try to make this discovery of all discoveries.We can both send out a message, and look for messages that someone else has sent out.The SETI institute’s job is to listen. But what do we listen for?

Orion Nebula M42 with Galaxy, Open Cluster, Globular Cluster, stars, and space dust in the universe and Milky Way.
The Universe is a large place in comparison to our planet, so searching for intelligent life is difficult. (Image: Antares_StarExplorer/Shutterstock)

The Voyager Messages

The first approach to making contact with extraterrestrial intelligence and inviting them to our earthly party is to mail out an invitation. The problem, of course, is that we don’t have their home address. So, we sent out two letters unaddressed in hope that they will somehow find a recipient.

In 1977, when Spielberg had humans making contact with the mother ship in the film Close Encounters of the Third Kind, the U.S. sent out two ships of its own–Voyager 1 and Voyager 2. They were sent out on trajectories with a couple of goals. First, they would pass planets and moons in our own solar system in order to give us a closer look at these places than we had ever had before. Ultimately though they were sent out there with an eye towards their continuing out of our Sun’s neighborhood into the great void of space, and on towards other solar systems where maybe they would be found—like a corked bottle with a note washing up on an interstellar beach somewhere.

The note was a gold record which has on one side recordings of a greeting from United Nations Secretary General Kurt Waldheim and President Jimmy Carter, as well as nature sounds and musical selections ranging from western classical music, to Indian classical music, to early rock and roll. The back of the record is engraved with images that include elements of basic science, like the structure of a hydrogen atom, to establish a sense of commonality in universal understanding.

It includes maps to our Sun and images of human and non-human life and of the double-helical structure of DNA to show the possibly unique elements of our planet. It also includes images demonstrating how to play the record in case the alien life forms find that they only use compact discs or mp3 players.

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A Needle in a Cosmic Haystack

There are several concerns about this approach to finding extraterrestrial life. First, what we really have is a needle in a cosmic haystack. If there is life out there, the odds of hitting it by randomly pointing are next to nothing. The universe is a huge place and we sent a tiny craft out randomly. The odds of hitting the extraterrestrial life lottery are extremely thin.

Second, it requires intelligent life, life that would be able to find the Voyager, extract the record, and make sense of it. Finally, it requires that the life form be careful enough with the record not to scratch it, in which case, all they’d learn about us is, “this is a present, this is a present, this is a present…”

The Sounds of Earth Record Cover.
The golden record on the Voyager space craft contains, apart form the sounds of Earth on it, helpful instructions for any alien intelligence that finds it. (Image: NASA/JPL/Public domain)

So, another means of looking for extraterrestrial intelligence was developed. If we aren’t able to send something out and contact them, maybe they have already sent something out and are trying to contact us. We just need to listen in order to hear them. But exactly what are we listening for and from where would it be sent?

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The SETI Institute

The lead in this project was taken by the SETI Institute, SETI standing for Search for Extraterrestrial Intelligence. The SETI Institute is a non-governmental, non-profit organization dedicated to the search for intelligent life. Founding members include the astronomer and author Carl Sagan, as well as computer pioneers William Hewlett and David Packard, and Nobel laureates Charles Townes and Baruch Blumberg.

The SETI Institute has been determined to bring UFO searching the scientific mainstream. While some of their activities are on a smaller scale and involve individuals with small antennae and personal computers, the most notable facility is The Allen Telescope Array. It is a collection of hundreds of radio telescopes arranged over almost two and a half acres of land. With an array that large, the entire sky can be scanned for signals.

Gathering at the ‘Water Hole’?

But what signals? It’s impossible to monitor every part of the sky for signals at every part of the electromagnetic spectrum. What part to monitor? The decision was made to focus on the so-called ‘water hole’.

Every element has a set of telltale frequencies of light it emits when excited. If you take hydrogen, the strongest line it emits is at 1420 megahertz. If you take the ionic molecule formed by hydroxyl radical its strongest light is radiated at 1666 megahertz. If you combine a hydrogen atom with a hydroxyl radical, you get water. The gap between 1420 and 1666 megahertz was thus dubbed, the ‘water hole’.

The idea is that since life as we know it depends on water; maybe all life does. Hence, this range of frequencies could be considered universal. It could be the sort of thing another intelligent race would see as more than idiosyncratic. It would be a place they would send a message if they wanted other intelligent life forms to find it. Therefore, it might work like a watering hole, a gathering place for animals.

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Looking for Intentional Messages

So, this band of frequencies is scanned with the hopes that a message can be found. There’s always noise out there no matter what part of the spectrum you monitor. Pick a frequency and there’s something in the universe that resonates at that frequency.

The key is to find the intentional messages from the noise. For this, computers check the results for patterns that would be unexpected if they were random. Repetitions, specific modulations that might correspond to meaningful values, anything that could be understood as the result of intelligent intention, that’s what we’re looking for.

SETI strategies have branched out beyond looking at radio waves, looking for other ways to see if somebody’s trying to call us on the phone, but whose ring we need to figure out how to detect. There’s been no success yet, but there is always hope.

Common Questions about Voyager and SETI

Q. How will the Voyager spacecraft communicate with other life in the universe?

In case the Voyager spacecrafts were found by extra-terrestrial, each of them has a gold record on it which has messages, music, and nature sounds. The back of the record is engraved with scientific images, and maps to our Sun. It also includes images showing how to play the record.

Q. What is the SETI Institute?

The SETI Institute is a non-governmental, non-profit organization dedicated to the search for intelligent life. SETI stands for Search for Extra-Terrestrial Intelligence.

Q. In which spectrum is SETI looking for signals from outer space?

SETI searches for signals in the gap between 1420 and 1666 megahertz, dubbed the ‘water hole’, which is a range of frequencies and could be considered universal. It would be a place where other intelligent beings would send a message if they wanted other intelligent life forms to find it.

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