"The Great Silence" -A Galaxy Insight

"The idea that we are the only intelligent creatures in a cosmos of a hundred billion galaxies is so preposterous that there are very few astronomers today who would take it seriously. It is safest to assume therefore, that they are out there and to consider the manner in which this may impinge upon human society."

Arthur C. Clarke, physicist and author of 2001: A Space Odyssey

One of the greatest philosophical and scientific challenges that currently confronts humanity is the unsolved question of the existence of extraterrestrial intelligence.

The Fermi paradox is the apparent contradiction between high estimates of the probability of the existence of extraterrestrial civilizations and the lack of evidence for or contact with such civilizations.

The 14-billion-year age of the universe and its 130 billion galaxies and a Milky Way Galaxy with some 400 billion stars suggest that if the Earth is typical, should be common. Nobel laureate Enrico Fermi, discussing this observation with colleagues over lunch in 1950, asked, logically: "Where are they?" Why, if advanced extraterrestrial civilizations exist in our Milky Way galaxy, hasn't evidence such as probes, spacecraft, or radio transmissions been found?

As our technologies become ever more sophisticated and the search for extraterrestrial intelligence continues to fail, the "Great Silence" becomes louder than ever. The seemingly empty cosmos is screaming out to us that something is amiss. Or is it?

Using a computer simulation of our own galaxy, the Milky Way, Rasmus Bjork, a physicist at the Niels Bohr Institute in Copenhagen, proposed an answer to the Fermi Paradox. Bjork proposed that an alien civilization might build intergalactic probes and launch them on missions to search for life.

He found, however, that even if the alien ships could hurtle through space at a tenth of the speed of light, or 30,000km a second, - NASA's current Cassini mission to Saturn is gliding along at 32km a second - it would take 10 billion years, roughly half the age of the universe, to explore a mere four percent of the galaxy.

Like humans, alien civilizations could shorten the time to find extra-terrestrials by picking up television and radio broadcasts that might leak from colonized planets. "Even then," he reported in the New Scientist, "unless they can develop an exotic form of transport that gets them across the galaxy in two weeks it's still going to take millions of years to find us. There are so many stars in the galaxy that probably life could exist elsewhere, but will we ever get in contact with them? Not in our lifetime."

The problem of distance is compounded by the fact that timescales that provide a "window of opportunity" for detection or contact might be quite small. Advanced civilizations may periodically arise and fall throughout our galaxy as they do here, on Earth, but this may be such a rare event, relatively speaking, that the odds of two or more such civilizations existing at the same time are low.

In short, there may have been intelligent civilizations in the galaxy before the emergence of intelligence on Earth, and there may be intelligent civilizations after its extinction, but it is possible that human beings are the only intelligent civilization in existence "now." "Now" assumes that an extraterrestrial intelligence is not able to travel to our vicinity at faster-than-light speeds, in order to detect an intelligence 1,000 light-years distant, that intelligence will need to have been active 1,000 years ago.

There is also a possibility that archaeological evidence of past civilizations may be detected through deep space observations — especially if they left behind large artifacts such as Dyson spheres.

Perhaps...but in our search for life and intelligence we have to keep in mind that the Milky Way Galaxy is two or three times the age of our Solar System, so there are going to be some societies out there that are millions of years, maybe more, beyond ours, which may have proceeded beyond biology—that have invented intelligent, self-replicating machines and it could be that what we first find is something that's artificially constructed if we have the ability to recognize it as such. It may very well be that our greatest discovery will be that the very nature of alien communication will prevent our being able to communicate with it.

Posted by Casey Kazan.

Comments

Un - manned / crewed space probes like Pioneer, Voyager would perhaps be more successful at gathering data & sending it back to whatever civilization ( s ) sent them. I remember reading a Star Trek novel " Strangers From The Sky " where the ubiquitous Vulcans observed us with automated probes - apparently using tachyon transmissions somehow - before sending living observers, that way, no cultural contamination is involved.

Also, even if extra - terrestrial civilizations were out there just pumping out radio transmissions every hour of every day, how would we recognize them, especially when time, distance, & interference from other interstellar phenomena would garble them ? How many civilizations out there would recognize transmissions from the early days of 20th century radio, the Apollo 11 landing, Martin Luther King's " I Have a Dream " speech, the razing of the Berlin Wall, any of earth history's high points ? Uncounted trillions & trillions of miles & several hundred thousand light years would possibly garble any message to or from earth.

Just a few thoughts.

Posted by: Daniel Appleton | September 07, 2007 at 03:04 AM

I think the concept of the Singularity explains the Fermi paradox. Specifically, civilizations that survive their "adolescence" develop technologies which allow them to transfer their consciousness to media other than biological. Computer circuitry is the obvious first step, possibly followed by transference of consciousness to photons (light) or a similar subtle medium.

Basically, we don't see or hear anybody because the biological period of an intelligent civilization is relatively short. At any given time we choose to look, we will find that everyone else blew themselves up or took it to "the next level."

Posted by: Naturyl | October 21, 2007 at 05:03 PM