Author: David

The Scientific rationale

The expectation that Alien/Extraterrestrial intelligence exists derives from two facts and one assumption: (1) The universe is vast, with approximately 1011 galaxies (a total of about 1022 stars) within the reach of telescopes. This number is so large that even if the emergence of intelligence is improbable, such intelligence could still have arisen frequently.

(2) The physics and chemistry of the universe are everywhere the same. This is known from astronomical observation.

(3) Habitable, Earth-like planets of the type that might spawn intelligence, with thick atmospheres and liquid water on their surface, are not extraordinarily rare. This is a hypothesis, sometimes called the principle of mediocrity. According to this principle, the Earth is not extraordinary in any of its important properties. The principle dates, in its modern form, to Nicolaus Copernicus (1473–1543), who dethroned the Aristotelian idea of an Earth-centered cosmos.

In addition to these general arguments, research gives support to the idea that extraterrestrial biology (not necessarily intelligent) might be plentiful. Since 1995, astronomers have detected planets around other, Sun-like stars. At minimum, 10–20% of such stars are now thought to have a solar system consisting of at least one orbiting body.

The discovery technique is to measure the small motions of the star induced by the planet, a scheme that is most sensitive to massive worlds in tight orbits. It is still unknown what fraction of stars have small, rocky planets similar to Earth, but the Kepler and Darwin space-based telescopes, now being planned, should decide this question.

The possibility that some other worlds in the solar system could have spawned life has also increased. There is good photographic evidence that Mars once had lakes and possibly oceans, and may still harbor liquid water hundreds of meters below its surface. Direct evidence for ancient Martian life, claimed to have been found in a meteorite that is known to have come from the Red Planet, is highly controversial.

A surprising discovery has been the growing indication for enormous oceans beneath the surface crust of several of Jupiter’s satellites (Europa in particular, but also Callisto and Ganymede). Even Titan, a large satellite of Saturn swathed in a thick, hydrocarbon-laced atmosphere, is considered a possible (albeit unlikely) habitat for simple life.

Whereas Earth was once thought to be the only solar system body that could support life, there are now several other candidates. If any of these has spawned indigenous life, it would demonstrate that biology is a commonplace occurrence.

Fermi paradox

Enrico Fermi is said to have posed the question “Where is everybody?” in 1950. His remark was intended to point out that, while humans are in no position to colonize other star systems, advanced extraterrestrials—if they exist—might do so. Even if they require thousands of years to travel from one star to the next, an ambitious society could spread itself throughout the entire Milky Way Galaxy in only a few tens of millions of years.

Since this is far less than the age of the Galaxy (about 12 billion years), it suggests that, if sophisticated and ambitious societies arose in the past, evidence of their presence should now be everywhere. Since that evidence is lacking, the implication is that the Galaxy is inhabited solely by humans.

There are many suggestions of how this paradox might be resolved; in other words, how the failure to see local evidence of alien activity could be reconciled with a Galaxy that we think might house many sophisticated societies. For example, it could be that interstellar colonization is so daunting that no one ever undertakes it.

Perhaps humans are incapable of recognizing the widespread presence of intelligence. Or the extraterrestrials could know about humans, but have arranged for a “one-way mirror,” whereby they can watch, but humans cannot detect them (the “zoo hypothesis”). The Fermi paradox, while intriguing, remains a point of discussion rather than a key to new knowledge.

Consequences of discovery

If a signal or other verifiable proof of extraterrestrial intelligence is discovered, what would be the effects on human society? Clearly, this depends on how distant the intelligence is, and whether (in the case of a signal) an embedded message can be deciphered. It is possible that any intelligence that is found will be hundreds or even thousands of light-years distant, in which case two-way conversation or direct, physical contact would be exceedingly difficult.

In the case of a SETI detection, it is quite likely that the transmitting intelligence will be far more advanced than our own. This is because there is a good chance of detection only if L is large (at least thousands of years), and it is unlikely that the first signal received would be from a society that is only a few hundred years beyond us.

(Of course, signals will not be found from societies that are not at least as accomplished as ours.) If such advanced beings wish to transmit useful information, human society would be greatly altered.

On the other hand, it may be that humans would never be able to decode the transmissions from such a sophisticated civilization. Even in that case, merely learning that intelligence has developed elsewhere in the cosmos would be a profound event.

About the Author:

The author, StunnerCold (Alias), is an Electrical engineer specializing in cutting edge semiconductor technology with an eye out for the long overdue galactic rendezvous.