Thursday, July 30, 2009

Fermi Paradox Points to Fewer Than 10 Extraterrestrial Civilizations

The absence of alien probes visiting the solar system places severe limits on the number of advanced civilizations that could be exploring the galaxy.

The Fermi paradox focuses on the existence of advanced civilizations elsewhere in the galaxy. If these civilizations are out there–and many analyses suggest the galaxy should be teeming with life–why haven’t we seen evidence of them?

Today Carlos Cotta and Álvaro Morales from the University of Malaga in Spain add another angle to the discussion. One consideration is the speed at which a sufficiently advanced civilization could colonize the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, a colonization wave could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain why we have yet to spot extraterrestrials.

Cotta and Morales take a different tack by studying how automated probes sent ahead of the colonization could explore the galaxy. Obviously, this could advance much faster than the colonization wave front. The scenario involves a civilization sending out eight probes, each equipped with smaller subprobes for studying the regions that the host probe visits.

This is not a new scenario. One previous calculation suggests that in about 300 millions years, those eight probes could explore just 4 percent of the galaxy. The question that Cotta and Morales ask is this: what if several advanced civilizations were exploring the galaxy at the same time? Surely, if enough advanced civilizations were exploring simultaneously, one of their probes would end up visiting the solar system. So that fact we haven’t seen one places a limit on how many civilizations can be out there.

The numbers that Cotta and Morales come up with depend crucially on the life span of the probes doing the exploring (and obviously on the number of probes each civilization sends out). They say that if each probe has a life span of 50 million years, and if evidence of their solar-system visits lasts about a million years, there can be no more than about 1,000 advanced civilizations out there now. If, instead, these probes can leave longer-lasting evidence of a visit–evidence that remains for 100 million years–then there can be no more than about 10 civilizations out there.

Of course, we may not have discovered the evidence yet. But if we finally find a black obelisk on the Moon, the paradox will be resolved.

Ref: http://arxiv.org/abs/0907.0345: A Computational Analysis of Galactic Exploration with Space Probes: Implications for the Fermi Paradox

The old assumption, popularized by Carl Sagan, was that the galaxy was probably teeming with such civilizations but they hadn’t contacted us because they haven’t been able to detect us yet. However with recent advances in Astronomy we can safely assume that any advanced civilization within a few thousand light years of earth should be able to take high resolution images of our planet.

I think it’s reasonable to assume that any highly advanced civilizations in our galaxy know about us assuming that they a)develop advanced technology and b) are curious.

So it seems probable that if any technologicaly advanced civilizations exsist in our galaxy they’ve chosen not to contact us.

Thanks for providing the above reference to your post on February 5th at 21:02 in Centaury Dreams.

I am personally fascinated by the concept of artificial evolutionary processess and how ETI might have used such to augment their species and how we humans are starting to do such, or may be about to do so for our species.

In a way, we already have some modern scientifically created emplements to alter the human central nervous system and human psychological characterists. One has to simply review the vast numbers of psychotropic pharmacological agents used to treat major mental/emotional disorders, as well as the agents being researched to mitigate developmental disorders such as autism, and the new treatments for Alziemer’s such as the prescription drug under the trade name Aricept.

Stem cell R&D promises to produce even more profound degrees of medical intervention, and perhaps, genetic engineering, or in the case where genetic engineering will not be palitable to the general public because of faith based ethics, post birth genetic intervention, will permit still more profound medical advancements.

It will be interesting to somehow know how future human settlements or colonies such as might be developed on the Moon, on Mars, and on words beyond will evolve in their unique biospheric habitats. I supposed that travel between these colonies will act to provide some genetic homogeneity among the future human ciivilization.

Thanks;

Jim

well, regarding Cambrian explosion – I think that today evolutionists start to agree that it was not such an explosion as it seemed to be. More and more evidence on complex life before Cambrian perion are found – so called Ediacara organisms for instance.

Leaving it aside I would say that Fermi Paradox is puzzling enough to treat rare-Earth rare-(complex)Life hypothesis seriously. Certainly the arguments you mentioned should not be neglected easily.

If this has ever happened it should be reflected in the genetic and other biochemical signature of life on various planets, which will in that case show a striking similarity that cannot be explained exclusively by natural selectively driven evolution. Somewhat similar to the way that we can see that the dingo did not originate in Australia, but at a more fundamental biochemical level.

If we ever find and are able to investigate planets that show this remarkable similarity, that may raise an interesting future discussion about the mechanisms of evolution, panspermia and even ID (meaning Intelligent Dissemination, pun intended).

“once only one to a few species within a galaxy becomes capable of intragalactic travel, the whole story changes in regards to the number of inhabited planets within a given galaxy and the formation of new species from both natural and artificial processes”.

Accurate conclusion James!

On February 5th at 21:02 in Centaury Dreams commentaries on ‘New Angles on the Drake Equation I wrote:

“A point to consider in future improvements of this modelling is not only ‘interstellar panspermia’ but very fundamentally ‘Interstellar Colonization’:

The intelligence timescale is calculated in [Forgan's] model by stochastic process: life does evolve on a planet by evolution stages that are randomly sampled. The resetting events (catastrophic life destroying events) are placed uniformly throughout each of the stages. If Nresets > Nstages, then any
given stage may suffer several reset events. The model compute that if a reset occurs and if that reset results in annihilation, life is exterminated, and the process ends; otherwise the evolutive process decreases.

If we permit strictly darwinian “Dawkins’Intelligent Designers” (interstellar interveners) in the eons of life’s evolution on colonizated targets then this stochastic ‘designer events’ must be included in [this(these)] model(s): any
given evolutionary stage may ’suffer’ several ‘designer’ events and the model must compute that if a novel design is seeded and if that design results in life (intelligence)’s improvement then the target planet’s evolutionary path is changed for the better; otherwise the evolutive process in it is left to extremaly slow (classical) local darwinian stages”.