Are We Alone in the Universe?

Posted April 30th, 2012 at 10:45 pm (UTC-4)

(Photo: Jeremy Burgin via Flickr/Creative Commons)

(Photo: Jeremy Burgin via Flickr/Creative Commons)

Many of  us believe finding some form of  life beyond our own planet is inevitable,  and the recent discovery of Earth-like planets – in a region where liquid water could exist on a planet’s surface – has renewed excitement about eventually finding extra-terrestrial life.

However,  two Princeton University researchers suggest those expectations may be more based in optimism rather than scientific fact.

Princeton’s Edwin Turner  and David Spiegel wanted to separate fact from expectation.

So they took what science currently knows about the existence, or likelihood of extra-terrestrial life, and performed a Bayesian analysis, which evaluates just how much of what is considered to be a scientific conclusion comes from actual hard scientific fact and what comes from assumptions made by the scientist involved.

What the duo found will disappoint those counting on meeting ET.

In a paper published in Proceedings of the National Academy of Sciences, Turner and Spiegel report finding little supporting scientific evidence that life exists, or could exist, beyond our own planet.

Instead, they found that most of what has been concluded about the possibility of extra-terrestrial life has been taken from what scientists know about the origins or emergence of life on early Earth.  And that our expecting life to be found on Earth-like exoplanets mostly centers on the assumption of what could or would happen if conditions similar to those that allowed life on Earth to flourish were found elsewhere.

Taking what we already know about life on other planets, the researchers say it’s very possible Earth may be an oddity compared to other planets, because life took root quickly and early in our planet’s history.  If this is true, then the chances of Earth-like planets hosting life would be low.

“If scientists start out assuming that the chances of life existing on another planet as it does on Earth are large, then their results will be presented in a way that supports that likelihood,” Turner said. “Our work is not a judgment, but an analysis of existing data that suggests the debate about the existence of life on other planets is framed largely by the prior assumptions of the participants.”

So what do you think?  Are our current expectations of finding life out there in the cosmos based on scientific fact or on mere optimism as suggested by the authors of this study?

Rick Pantaleo
Rick Pantaleo maintains the Science World blog and writes stories for VOA’s web and radio on a variety of science, technology and health topics. He also occasionally appears on various VOA programs to talk about the latest scientific news. Rick joined VOA in 1992 after a 20 year career in commercial broadcasting.

9 responses to “Are We Alone in the Universe?”

  1. Spec. says:

    Guys, If you look outwards into space, you’ll notice that there are a LOT of stars out there and, if you were to inquire a little deeper, you’d discover that main sequence yellow and red dwarf stars are the most COMMON stars in any galaxy, including ours. Therefore the percentages are in favor of life being out there, no matter if it’s intelligent or not.
    Now, I’m just talking about life as we know it based on CARBON and existing on a planet SIMILAR to the one we live on. Therefore, any life we find on a planet similar to our own should also be based on CARBON, exhibit bilateral symmetery and should look something like human beings. The farther from the above template that you go, the more different that life form will probably be. We could potentially discover a life form based on silicon which more than likely would closely adhere to what we would expect from Carbon based life forms.
    I have seen a short film of ” something ” the Russian Cosmonauts saw and supposedly filmed that was moving around OUTSIDE their MIR Space Station. To me, it didn’t have any eyes or openings which would make life in space almost impossible. However, this thing undulated around in ways reminescent of bacteria and parasites so, I had to go back and rethink a few things. My conclusion is simple, since we know for a fact that there are microscopic living things such as Bacteria, Molds, Yeasts, Viruses, Fungi, Ricketsias and even smaller Nanobacteria along with other parasites then, I had to accept the possibility that there could also be MACROSCOPIC forms of the above life forms that could live in space. To my way of thinking, anything less than that is based on pure arrogance or, the complete unwillingness to accept anything that differs from the view points of the so called experts. Remember, they have their reputations at stake and so long as no one can positively proove that alien life of ANY sort exists, then their claims are still viable and they can continue to claim that only their viewpoint is the correct one.
    Remember the arguements not too long ago about free standing water being on the surface of Mars ? Well, I’ve seen photographs taken by our Mars orbiters and some corroborating evidence from our Mars Rovers as to the actual existence of ice on the surface of Mars and even a few examples of what looks to be largish lakes of water there as well.
    Further, if you go on any search engine and type in, ” TREES on MARS ” you’ll discover what certainly looks like TREES are growing there and, if this turns out to be true, well then, we have had our first PROVEN discovery of life existing on another planet.
    Then, there begs the question of, ” Is there life existing under the ice of those water moons of the outer gas giant planets as well ??! ” Who knows. Only by going there will we discover the truth.
    This planet of ours has only so many resources and, once those are used up, there won’t be any more therefore, it behooves us to get into space on a permanent basis as soon as possible and begin to exploit the unlimited amount of resources that we will find out there and by so doing,save the human race from certain extinction.
    Of course, this is only my opinion… What do you think ?! ——- Spec.

  2. igli says:

    What a silly article. Scientific evidence says the opposite. A history reminder:

    Millenia ago lots of folks thought the earth was the center of existence – Wrong. The the sun was a center – Wrong. The earth is one of billions of earths as is the sun one of trillions of suns. Mankind is one of trillions. At least that is where thought starts, not from the opposite view – We are so special. We are alone -. Very silly.

  3. Anil says:

    Even if the odds are extremely low, there are so many galaxies, stars, and planets that even the smallest number of worlds with life would mean the universe has a very large number of them.

  4. Harv Hess says:

    Carl Sagan had it right. He was a smart guy. However, since our ability to communicate with other lifeforms has only been possible during the last seventy five years, other lifeforms on other planets could be a few hundred thousand or more years behind us in their evolution. Other life forms are sure to exist on other planets, but is there intelligent lifeforms is another question. But this is speculation that anyone can play and scientific knowledge and a computer are not required..Our old hangup about wanting to believe we are the center of the universe is also involved here.


  5. Jono says:

    Scientific evidence for life on other worlds extends to relatively recent archeological data as well as astronomy and life sciences. There’s an interesting series on what is called ‘Ancient Aliens’ for example that postulates that life down here began out there. I bet archaeology and the scientific perspectives from that show were not taken into account. If they were, the odds would dramatically sway in favor of life being abundant in the universe. You should also no that the recent analysis of the data from the 1970s Viking lander produced a 99% probability of microbial activity.

  6. Sarah says:

    Plus there is a lot of evidence of extraterrestrial involvement with earth already, but no one wants to come out and say that it’s a fact. I love and support programs like SETI, but I wish they would turn their telescopes toward earth and investigate what’s going on on earth, like crop circles, nuclear weapons being dismantled by UFOs, abductions, etc. I also feel that the way we “prove” things to be true or untrue is very limiting and close-minded. People once thought there was no such thing as microbes too small for the human eye to see or that nothing could ever travel faster than the speed of sound. Perhaps there are ways to travel faster than the speed of light or other ways to travel vast distances quickly but many of our minds cannot grasp this yet.

  7. Risha says:

    even if we do have no scientifical facts prooving that extra-terrestrial life exists, there’s a waterlight theory of probability according to which it DOES exist somewhere in the cosmos.

  8. Salieu Jallow says:

    I just don’t know but do HOPE it exist. Lets keep hoping.

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