There’s no reason to think that life exists only on earth. There are 100 billion or more stars in the Milky Way, and possibly one to two trillion galaxies in addition to our own. We’re now able to detect planets around many of the stars in our galaxy by observing subtle shifts in a star’s position (attributed to the gravitational pull of a planet) and by noting changes in a star’s brightness (attributed to a planet passing in front of it). About one in five of these stars, 20 billion, are similar in size to our sun, and have an earth-size planet where life could evolve.
We should assume the same conditions in other galaxies, making possible locations for life at least 20 billion times a trillion. As far as we know, the only essential ingredients for life are water, nitrogen, phosphorus, and sulfur, which resulted in life on earth only a few hundred million years after water appeared on its surface. Was the beginning of life on earth a freak accident, or something that anyone who has a few hundred million years to kill should expect to happen? We don’t know.
A Mars rover is investigating rock formations on Mars to determine if they contain the fossil remains of microbial Martian life two billion years ago. Evidence of such life will suggest that life commonly begins wherever conditions are appropriate, because it will mean that of the two planets in our solar system known to be capable of developing life, both did so. This suggests that many other appropriate planets in the universe have done so as well, as we have no reason to think that they lack the necessary chemicals.
However, life on trillions of planets in the universe doesn’t make it likely that we’ll be able to communicate with extraterrestrials. Microorganisms are very poor conversationalists, especially dead ones like those that may have existed on Mars. For communication, we need life forms that are intelligent and that have used their intelligence to construct highly sophisticated means of communicating at a great distance.
A widely attested astronomical observation made in 2017 has been interpreted by some accredited astronomers as suggesting the presence in the universe of such a sophisticated life form. Astronomers agree that it was an interstellar object, that is, one originating outside our solar system, and that instead of rounding the sun in a parabola, as a comet would, it was accelerating directly away from the sun. This can happen to comets when they emit gases from their tails (suppress your inner 10-year-old), but no gases were detected.
According to some astronomers, the object, which they named Oumuamua (pronounced oh-mooah-mooah, the Hawaiian word for scout) was cigar-shaped and its movements something of a mystery. Harvard astrophysicist Avi Loeb, however, believes that Oumuamua was shaped like and served as a sail that was accelerating away from the sun under the force of solar radiation. We can’t follow up because Oumuamua is now too far away. If it is a sail, it was manufactured by some intelligent form of extraterrestrial life. But how does that help with communication? What message does a sail convey? We’re not talking about “Please pass the ketchup.”
Another problem with communication concerns distance. Our galaxy is about 100,000 light years across, so the average distance from earth to a star is about 30,000 light years. If we were to send a radio signal to intelligent extraterrestrials on a planet near a star of average distance, it would take 60,000 years to get a reply, as no communication can exceed the speed of light. Will anyone on earth know what message was originally sent? How many 60,000-year-old human messages can we interpret today? A return message from a different galaxy would take billions of years.
Will intelligent life on other planets exist at the same time that we exist? Our existence at this time depends on an asteroid hitting earth 65 million years ago and wiping out dinosaurs. Without that accidental collision, human-like intelligence on earth may never have developed, or may have been delayed 50 or 100 million years.
Our window of opportunity for communicating with extraterrestrials is probably small. We started using radio signals only about 100 years ago. Our technical sophistication has resulted in nuclear weapons and climate change, which don’t bode well for our species persisting for millions of years. If the timing and longevity of other intelligent life with sophisticated technology is similarly precarious, the chances are poor that we and they will exist at the same time, and continue to exist for the amount of time that long-distance communication requires.
In sum, the prospects for a good heart-to-heart with extraterrestrials are extremely poor. E.T may have phoned home, but don’t expect him to phone us.
Commenti