Are we alone in the universe? Or are there other intelligent species in our galaxy? This is one of the greatest mysteries facing humankind.
Given the >100 billion stars in our galaxy, many have argued that it is statistically unlikely that life, including intelligent life, has not emerged anywhere else. The Milky Way is >13 billion years old and our Solar System less than half as old, meaning that extraterrestrial civilizations in older star systems are likely much older and more advanced than ours. Because the estimated time for an intelligent civilization to colonize, or at least explore, the 100,000 light year diameter galaxy is <100 million years, one would expect older intelligent species to have reached us by now. The lack of any sign of extraterrestrial intelligence, even though on a cosmic timescale extraterrestrial civilizations would have enough time to cross the galaxy, is known as Fermi's Paradox.
Many explanations have been put forward to explain this mysterious “Great Silence”, including various barriers to the formation and survival of civilizations and of life itself. Perhaps very few systems harbor planets suitable for life or interstellar space travel is very challenging, even for advanced civilizations. Ongoing research in astrophysics and astrobiology may shed light on which explanations to Fermi's Paradox are more likely to be correct. Search for extraterrestrial intelligence (SETI) efforts that have been ongoing for over half a century have so far been unsuccessful, yet have only monitored a tiny fraction of detectable star systems for very small amounts of time. Lastly, efforts in Active SETI, also known as METI (messaging to extraterrestrial intelligences), aim to send messages to outer space in hope of engaging with extraterrestrial civilizations. Our own proposal is one of such efforts.