By Morris Jones, METI International Advisory Council
“Archaeology is Rubbish.” Such is the title of a book connected to a well-known television series on the subject. Digging out the buried remains of civilizations past is a wonderful way to learn about them. We can understand their level of technology, their social structure, their potential trade links with other civilizations, their language and their culture. Archaeology has been used to discover and document civilizations that have otherwise left no lasting evidence of their time upon the Earth. Ironically, most of the material that is recovered by these digs is not as elaborate as golden sarcophagi. It’s truly rubbish, at least by the standards of the civilization that produced (and discarded) the material. Yet the knowledge it yields is sometimes priceless.
Rubbish from epochs ago is thus considered valuable, even though it’s from other humans living in areas on the same planet, from times that are not that long in the overall timescale of the cosmos. Imagine, then, how precious we would consider the discovery of rubbish from an extraterrestrial civilization.
The Search for Extraterrestrial Intelligence can be divided into roughly two modes. There is the search for signals or emissions from extraterrestrials, which could be anything from radio transmissions, to laser beams, to gravity waves rippling through space. That’s SETI as it’s usually done. There’s also a smaller but still important wave of searches for extraterrestrial artefacts. Sometimes this is performed with telescopes, looking for grand structures such as Dyson Spheres. These are hypothetical shells built to surround entire solar systems, absorbing most of the energy from the star within. There has also been a smaller quest to find smaller artefacts from extraterrestrials. It doesn’t get much attention, simply because we haven’t found anything. Nobody has found extraterrestrial rubbish on the Earth, the Moon, any nearby planets, or in space. But that doesn’t mean that our first evidence of an extraterrestrial civilization won’t be discovered this way.
Consider planet Earth. We’re a fledgling spacefaring civilization, just probing the edges of our own solar system. But already, we have a problem with space junk. There’s so much material orbiting the Earth that it’s a safety hazard to spacecraft and astronauts. Every time a spacecraft is launched into deep space, it usually carries a small flotilla of discarded parts that fly on the same trajectory. These could be anything from rocket stages to bolts.
Our own potential archaeological “junk” is already percolating into the cosmos. It seems reasonable to assume that other civilizations could also be launching probes into deep space, and filling the cosmos with artefacts big and small. Never mind the spiffy interstellar probes and glittering pictographic plaques that we love. Statistically, we are more likely to encounter trash of various sorts.
True, this isn’t at the top of the wish list for most extraterrestrial hunters. We want an extraterrestrial encyclopedia. We want a starship. We want to meet the extraterrestrials themselves. But right now, we don’t have anything from them at all. A piece of extraterrestrial rubbish would truly be priceless to us.
Like archaeology on Earth, much information could be extracted from even a mundane item produced by extraterrestrials. The most important fact of all would simply be confirming that we are not alone in the universe. We could also analyse the materials and possibly make deductions about the manufacturing. But there would still be a lot of uncertainty. Earth archaeologists can deduce so much from so little precisely because they have the background information to do so. They know all about humans. They know all about consistencies between other civilizations. They know that some things keep getting reinvented. An isolated fragment of junk from deep space would probably not benefit from such knowledge. Sadly, we would probably know very little at all about the species that produced it, assuming we had nothing else to use as references.
This makes the search for extraterrestrial artefacts seem potentially frustrating, but such problems are common across all segments of SETI. We may discover an extraterrestrial transmission. We may confirm that it is artificial, and not a natural astrophysical source. But that could be all we could precisely deduce. We may not understand if there is a language being used, or any sort of encoded information. We would also probably know nothing about who sent the signal, or why.
An intercepted signal would possibly not be a deliberate beacon to the universe. It could simply be a mundane alien radar beam, or an accidental energy emission. The civilization that produced it may not even be trying to contact us. That’s true for most of Earth archaeology as well.
Sometimes, you have to work with whatever you have. The SETI community is not finicky about what it finds. We just want to find some evidence that humanity is not alone in the universe. But whatever we find, we will do our best to ensure that we learn as much as possible from even the faintest blip, or the smallest fragment. The SETI community also has the benefit of drawing on the work of scholars and scientists from a variety of disciplines. This ensures that any evidence will be studied from every angle. With a broad, interdisciplinary approach, a bountiful feast of knowledge will be baked from even small morsels of raw ingredients.