Is there a fundamental flaw in why we have not received a signal from an advanced alien civilization? How do we decode an alien message –alien is alien so it might be impossible. What if they communicate chemically? Will they use the language of math and science signaling at 1420 megahertz? What if we are too primitive to comprehend a message or the technology of its signal that may exist in a form beyond matter? What if it’s a message from an extinct civilization astrophysicist such as Harvard’s Avi Loeb believes exist in our galaxy? Or, as John Gertz suggests for Scientific American, maybe the aliens are already in our solar system, probably in the form of robotic probes.
In contrast to Harvard astrophysicist Avi Loeb’s optimism that extraterrestrials are less speculative than dark matter or extra dimensions, a study posted in September of 2018 conducted by three scholars from the Future of Humanity Institute (FHI) at Oxford University, suggesting that although we exist in a universe with a potential 50 quintillion habitable planets, the expectation that life — from inorganic to bacteria to sentient beings —abiogenesis– has or will develop on other planets as it has on Earth, might be based more on optimism based on a sample of one.
It is conceivable that a civilization advanced enough to see itself in a cosmological context would think of a way to make itself known to the universe. In “The Messenger: A Galactic Center Gravitational-Wave Beacon” pre-print on Arxix, an international team of researchers have proposed a hypothetical alien craft, a beacon at the Milky Way’s Galactic Center, “The Messenger”, that emits gravitational waves that are “unambiguously artificial”.