Are We Alone In the Universe? New Analysis Says Maybe

For decades I have been intrigued by the idea that human beings from planet earth are the only sentient beings in the universe.  It is all up to us.  We are indeed "The Crown of Creation" and the populating of the universe is up to us, one planet at a time.  We have the power to civilize the entire universe, or if we fail and our species becomes extinct, all creation will be nothing but animal, vegetable or mineral.

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Are We Alone In the Universe? New Analysis Says Maybe

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. [10 Alien Encounters Debunked]
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.
While it's true that life arose quickly on Earth (within the planet's first few hundred million years), the researchers point out that if it hadn't done so, there wouldn't have been enough time for intelligent life — humans — to have evolved. So, in effect, we're biased. It took at least 3.5 billion years for intelligent life to evolve on Earth, and the only reason we're able to contemplate the likelihood of life today is that its evolution happened to get started early. This requisite good luck is entirely independent of the actual probability of life emerging on a habitable planet.
"Although life began on this planet fairly soon after the Earth became habitable, this fact is consistent with … life being arbitrarily rare in the Universe," the authors state. In the paper, they prove this statement mathematically.
Their result doesn't mean we're alone — only that there's no reason to think otherwise. "[A] Bayesian enthusiast of extraterrestrial life should be significantly encouraged by the rapid appearance of life on the early Earth but cannot be highly confident on that basis," the authors conclude. Our own existence implies very little about how many other times life has arisen.
Two data points rather than just one would make all the difference, the researchers say. If life is found to have arisen independently on Mars, then scientists would be in a much better position to assert that, under the right conditions, the genesis of life is inevitable.
This article was provided by Life's Little Mysteries, a sister site to SPACE.com.
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Are planets that support life, such as Earth, rare?

Hat Tip to Bad Touch

In planetary astronomy and astrobiology, the Rare Earth hypothesis argues that the emergence of complex multicellular life (metazoa) on Earth required an improbable combination of astrophysical and geological events and circumstances. The term "Rare Earth" comes from Rare Earth: Why Complex Life Is Uncommon in the Universe (2000), a book by Peter Ward, a geologist and paleontologist, and Donald E. Brownlee, an astronomer and astrobiologist. Their book is the source for much of this article.
The rare earth hypothesis is the contrary of the principle of mediocrity (also called the Copernican principle), advocated by Carl Sagan and Frank Drake, among others.^[1] The principle of mediocrity concludes that the Earth is a typical rocky planet in a typical planetary system, located in an unexceptional region of a common barred-spiral galaxy. Hence it is probable that the universe teems with complex life. Ward and Brownlee argue to the contrary: planets, planetary systems, and galactic regions that are as friendly to complex life as are the Earth, the solar system, and our region of the Milky Way are very rare.