We May See Aliens Before We Ever Hear Them

When popular stories reference the SETI project, they normally focus on the search for alien radio signals, but that particular aspect of the search for intelligent life is subject to several technical limitations and big assumptions. One of the biggest is that it requires aliens to use high power radio signals in a spectrum we could pick up on.

There are numerous reasons why this might not be the case; for instance, radio may be impractical for communication in other environments, or it may even be biologically incompatible with other life forms. It is possible life forms in other environments use a broad section of the radio spectrum for biological functions, making it unpleasant or even dangerous to create artificial radio waves.

Another major problem is that powerful radio transmitters may already be outdated to other forms of life. Radio may only be a transitional technology used for roughly a few hundred years, which is a blink of the eye compared to the age of the universe. It could quickly be replaced by fiber optics, lasers, multiple low-power relays or some advanced technology we have yet to discover. Aliens could of course go out of their way to build a giant radio station to randomly blast a signal, out of the slim hope some extremely primitive species very far away might possibly hear it, but it is easy to imagine many reasons why aliens would consider that wasteful or stupid.

What potentially will prove more fruitful is actually “looking” for the engineering projects of alien civilizations instead of trying to listen for them. Structures like a ring world or Dyson sphere that would be built to encircle an entire star could be detected with our current telescope technology. Such structures are almost unimaginable with our current level of technology, but they would potentially make sense for an advanced civilization to build for their own use. It would allow them to make use of a large percentage of a star’s massive energy output. 

In other words, there's no need to count on aliens trying to randomly communicate.

While theoretically only a fraction of alien civilizations that are advanced enough to build a radio would ever eventually reach the point that they could engage in massive celestial engineering, anything they did build would likely be built to last. A very long-lived alien civilization may only use powerful radio signals for a few centuries early in its history on a single planet, but there is the possibility they would engage in massive engineering projects across several star systems that would last for millions of years. It is longevity over quantity.

We may literally “see” an alien civilization before we ever hear from one. It would, though, be a shocking way to find out we are not alone in the universe. It would mean there is a species out there with powers beyond our comprehension and technology at least thousands of years more advanced than our own. Compared to such a structure, modern Tokyo and a Bronze Age farming village would appear to be equally advanced. 

(Image credit: NASA/CXC/JPL-Caltech/STScI/NSF/NRAO/VLA)