How many intelligent extraterrestrial civilizations are there , and when will they send us a message.
According to a paper published by The Astrophysical Journal , the answers are 42,777 and sometime within the next 2,000 year. This is a reasonable explanation for the Fermi Paradox. It asks why we haven’t received messages from other civilizations, despite their existence being highly probable.
It estimates the number of possible CETIs–communicating extraterrestrial intelligent civilizations–within our Milky Way galaxy. It estimates how likely it is for one of them to contact us, and when.
These seemingly precise estimates are not perfect and there are many unknowns that, if they were known, would make a huge difference in the final results.
- There is a high chance of life appearing on rocky worlds, and eventually evolving into civilizations capable of communicating with another.
- What stage would such advanced civilizations emerge from?
The optimistic side of the 42,777 figure (which has an error rate a few hundred per side) is therefore positive. This figure is based on the assumption that 0.1% civilizations would be advanced enough to communicate with one another. This is where the Great Filter helps.
It also considers the fact that civilizations would have to survive for at least three million years to reach this point.
The question of whether we can survive long enough for an alien message to reach us is still open, even if it does come from an advanced civilization somewhere else in the Milky Way. According to the authors, we may need to wait up to 2,000 years before receiving an alien signal.
These are the optimistic calculations. Pessimistic estimates by the authors are that only 0.001% civilizations (about 111) will be advanced enough to communicate with another.
That would mean that humans would have to wait for 400,000 year to receive a message.
The authors of the paper, Wenjie Song at Beijing Normal University’s Department of Astronomy, write that “The minimum value (0.001%),” may be exaggerated. “If this were true, the number CETIs could be even smaller and communication between CETIs might become very difficult.”
The Wow! is the only possible message that was ever sent to Earth by an extraterrestrial intelligence. The signal was received at the Big Ear radio telescope in Ohio in 1977. It was heard for 72 seconds, which was the maximum time possible at that time. It was never repeated.
Although the source of this signal is unknown, a paper recently found one Sun-like star (called 2MASS 19281982-2640123 in a sample from 66 in the area of the night sky called Wow! It is not known where it came from. It’s 18,000 light-years away.
A paper in 2012 estimated that the nearest civilization to the sun was 1,933 light-years away.
Let’s get back to you. Yes, it’s possible. However, there is one problem. It would take 1,800 years for any radio or laser transmission to reach the destination.
The authors point out that Arecibo radio telescope collapsed in 1974 was used by astronomers to send the “Arecibo messages” to the Great Hercules Globular Cluster (M13). It wasn’t very good. The authors write that if there are CETIs in M13 their detection capability must be 21 orders higher than ours to detect the signal. In reverse, if they transmit the same signal, then we must improve our detection capability by 21 orders.
Space is huge, really big. Even in-galaxy messaging can be impossible. It’s unlikely that we will ever discover the truth, even if we aren’t alone.
We are still looking for Earth-like exoplanets in the 2MASS 19281982-2640123 area.