Chance of alien life? Not likely..

David S. Spiegel , Edwin L. Turner  y


Dept. of Astrophysical Sciences, Princeton Univ., Princeton, NJ 08544, USA, and yInstitute for the Physics and Mathematics of the Universe, The Univ. of Tokyo, Kashiwa Japan

Submitted to Proceedings of the National Academy of Sciences of the United States of America


Life arose on Earth sometime in the first few hundred million years
after the young planet had cooled to the point that it could support
water-based organisms on its surface. The early emergence of life
on Earth has been taken as evidence that the probability of abiogen-
esis is high, if starting from young-Earth-like conditions. We revisit
this argument quantitatively in a Bayesian statistical framework. By
constructing a simple model of the probability of abiogenesis, we
calculate a Bayesian estimate of its posterior probability, given the
data that life emerged fairly early in Earth's history and that, billions of years later, sentient creatures noted this fact and considered its implications.

We find that, given only this very limited empirical information, the choice of Bayesian prior for the abiogenesis probability parameter has a dominant influence on the computed posterior probability.

Thus,although life began on this planet fairly soon after the Earth became habitable, this fact is consistent with an arbitrarily low intrinsic probability of abiogenesis for plausible uninformative
priors, and therefore with life being arbitrarily rare in the Universe.

Our conclusion that the early emergence of life on Earth
is consistent with life being very rare in the Universe.

http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.3835v1.pdf

Another take...

Scientists engaged in the search for extraterrestrial intelligence (SETI) work under the assumption that there is, in fact, intelligent life out there to be found. A new analysis may crush their optimism.

To calculate the likelihood that they'll make radio contact with extraterrestrials, SETI scientists use what's known as the Drake Equation. Formulated in the 1960s by Frank Drake of the SETI Institute in California, it approximates the number of radio-transmitting civilizations in our galaxy at any one time by multiplying a string of factors: the number of stars, the fraction that have planets, the fraction of those that are habitable, the probability of life arising on such planets, its likelihood of becoming intelligent and so on.

The values of almost all these factors are highly speculative. Nonetheless, Drake and others have plugged in their best guesses, and estimate that there are about 10,000 tech-savvy civilizations in the galaxy currently sending signals our way — a number that has led some scientists to predict that we'll detect alien signals within two decades.

Their optimism relies on one factor in particular: In the equation, the probability of life arising on suitably habitable planets (ones with water, rocky surfaces and atmospheres) is almost always taken to be 100 percent. As the reasoning goes, the same fundamental laws apply to the entire universe, and because those laws engendered the genesis of life on Earth — and relatively early in its history at that — they must readily spawn life elsewhere, too. As the Russian astrobiologist Andrei Finkelstein put it at a recent SETI press conference, "the genesis of life is as inevitable as the formation of atoms."

But in a new paper published on arXiv.org, astrophysicist David Spiegel at Princeton University and physicist Edwin Turner at the University of Tokyo argue that this thinking is dead wrong. Using a statistical method called Bayesian reasoning, they argue that the life here on Earth could be common, or it could be extremely rare — there's no reason to prefer one conclusion over the other. With their new analysis, Spiegel and Turner say they have erased the one Drake factor scientists felt confident about and replaced it with a question mark.

Their result doesn't mean we're alone — only that there's no reason to think otherwise.

http://www.space.com/12421-alien-life-rare-universe-extraterrestrials-seti.html

These people are all barking up the wrong trees. Ha Ha Ha.

Recent conclusions are that aliens are coming through to our space time reality from another dimension.

This stuff is sooo five minutes ago. ha ha ha.

It actually doesn't make sense that scientists would assume that with all the space of the universe that there wouldn't be other life.

I would say that the scientist who do these assumptions are really scared of aliens...lol

But I do not believe that they would be anymore advanced then we are basically so they are sitting in their living room wondering what we look like over here too.

They don't assume there is no life they are saying that something in close proximity to what has happened on earth is a very rare event.

I think you should write some scripts and maybe they can launch a modern version of the twilight zone.

Aliens traveling from other dimensions get off on mutilating cows and creating pretty pictures in someones cornfield.

Now that is movie material.

You wouldn't happen to have an extra tachyon amplifier would you?

The twilight zone? Look around, you are living in it.

UFO's have been seen and video taped coming and going. Moving faster than physics allows, appearing and disappearing.

Do a little reading on the details of crop circles and tell me how they are done and who does them.

Unconvince me please.

If you could solve these mysteries with believable and plausible explanations.... every single one of them, I would be extremely happy. I could join the group of people who think they are the only intelligent life in the universe.

I would feel much better.