The search for extra-terrestrial life has a long and imaginative history and we have come a long way since we imagined alien civilizations building great channel systems on Mars. Nowadays, the Seti program (which actually just means the Search of Extra-Terretrial Intelligence) linking millions of computers, exemplifies how fascinated we as a civilization are with finding alien life, but for all our technological advances, we have yet to find any sign of extra-terrestrial life, let alone of extra-terrestrial intelligence.
This may be about to change.
Several methods are underway in attempting to discern whether planets hold life and/or if they hold intelligent life. Recently, Breakthrough Listen got a 100 million cash injection from a Russian billionaire, with it a 100 meter wide dish will observe the 1 million nearest stars, next to looking at the core and disc of the Milky Way as well as looking at a hundred other galaxies. When scanning, it will not scan for one radio channel, but some 10 billion simultaneously. It will be 50 times more sensitive than any previous effort.
Our vision of space is simultaneously a vision back in time, a place we observe one hundred light-years away, would be an observation of that place one hundred years ago. I’ll call that virtual sphere of our vision our space horizon.
If my hypothesis to explain the Fermi paradox holds true, that is, life elsewhere is maximally just as advanced as it is here, how big would our space horizon than be with different detection methods?
The Breakthrough Listen project aims to detect deliberately sent signals, something we have been capable of some 50 years, so I predict a space horizon for this method of ~50 light-years in which we will find intelligence life.
We might also be able to detect leaking radiomagnetic signals, the sort we have been producing since say the start of the last century. If we get this technology right, which we might not be able to for a while, I predict that we will detect civilization within a space horizon of about a 120 light-years, plus all the additional years before we master the technology that enables us to catch those signals.
Much detection is focused on atmosphere. Most molecules are not indicative of life per se, O2-O2 is reckoned to be a sure sign of photosynthetic life. For this method I predict it to be able to find life within a 3.4 billion light-year space horizon (when photosynthetic life evolved on Earth), meaning that if our detection capability would be sensitive enough, we could detect life in other galaxies.
A more out of the box method attempts to determine the spectral signature of CFC’s from the planets’ atmosphere. CFC’s rose to infamy due to their detrimental effects on our atmosphere. Its artificial nature, together with its extremely long half-live decay time of a 100,000 years, make it a reasonably sure sign of an advanced civilization. Measurements should be sensitive enough to be able to detect concentrations that are tenfold our current concentration, estimated to be a 1000 years more advanced than we are. I predict then that this method in its current form will not find any signs of intelligent life, since no civilization would be ahead of us by a 1000 years.
Dyson spheres, the theoretical setting of solar panels fully encapsulating a star to capture all its sunlight, a feat envisioned to be able by a so-called Kardashev type II civilization and detectable due to a lack of light combined with an excess of infrared, I predict we will not find anywhere.
Finally, I predict we will find no physical evidence within our solar system of aliens that came here.