There is no hope of finding alien life in space because conditions on all other planets are too hostile, according to Howard Smith, a senior astrophysicist at Harvard. Smith made the claim after an analysis of the 500 planets discovered outside out Solar System that showed that extreme conditions are likely to be the norm, and that the hospitable conditions on Earth could be unique.
“We have found that most other planets and solar systems are wildly different from our own. They are very hostile to life as we know it,” he said.
Elsewhere, a team of scientists recently declared the chance of aliens existing on a newly discovered Earth-like planet “100 per cent”. Steven Vogt , of the Carnegie institution in Washington, said he had “no doubt” extraterrestrial life would be found on a small, rocky planet found orbiting the red dwarf star Gliese 581 last September.
Such hopes are likely to be raised further in 2011, when Nasa's Kepler spacecraft is expected to confirm the existence of hundreds more new planets.
Smith dismissed the claims, adding that "Extrasolar systems are far more diverse than we expected, and that means very few are likely to support life. Any hope of contact has to be limited to a relatively tiny bubble of space around the Earth, stretching perhaps 1,250 light years out from our planet, where aliens might be able to pick up our signals or send us their own. But communicating would still take decades or centuries."
The "Rare Earth" hypothesis put forwrad by Smith is the idea that life is a staggeringly unlikely event, and that the reason we haven't seen hide nor hair (nor scale nor weird gel-layer) of aliens is that there aren't any. It's had some time in the spotlight, it makes us sound very important, and it's wrong.
The Rare Earth argument ignores a number of essential factors, the first being how staggeringly huge the numbers involved are. Even the Milky Way has 200 to 400 billion stars, and it's only one of a hundred billion galaxies in the observable universe, and there have been billions of years for things to happen. Countering "it's really unlikely" with "but there are lots of things!" might sound weak, but it's the Rare Earthers who are taking the burden of proof - claiming that nothing happens anywhere else ever. The more places there are, the worse their argument gets.
Geologist Peter Ward and astrobiologist Donald Brownlee, both of the University of Washington have outlined a short list of conditions needed: Right distance from a star; habitat for complex life; liquid water near surface; far enough to avoid tidal lock; right mass of star with long enough lifetime and not too much ultraviolet; stable planetary orbits; right planet mass to maintain atmosphere and ocean with a solid molten core and enough heat for plate tectonics; a Jupiter-like neighbor to clear out comets and asteroids; plate tectonics to build up land mass, enhance bio-diversity, and enable a magnetic field; not too much, nor too little ocean; a large moon at the right distance to stabilize tilt; a small Mars-like neighbor as possible source to seed Earth-like planet; maintenance of adequate temperature, composition and pressure for plants and animals; a galaxy with enough heavy elements, not too small, ellipitcal or irregular; right position the galaxy; few giant impacts like had 65 million years ago; enough carbon for life, but not enough for runaway greenhouse effect; evolution of oxygen and photosynthesis; and, of course, biological evolution.
Claims that there aren't many suitable planets over all these stars are like hiding in a closet and claiming there's no such thing as coffee tables - we're now detecting planets at an ever-increasing rate, because now we have technology actually capable of detecting planets. Almost as soon as we try any new planet-detecting technique it detects a whole bunch of the things. We're even edging into the ability to find Earth-size planets, and what do you know? There they are! And some even have water!
The second slip-up is ignoring the suitability of the laws of physics to life - or rather, the suitability of our form of life to the laws of physics. The idea of someone sitting in pre-existence limbo and tuning the weak nuclear force in order to create bald monkeys is patently ridiculous, as is the idea that only a tiny range of values could give rise to any repeating pattern - our pattern, DNA, is just the one that happened to work for the collection of constants we call reality.
Once life is possible in a universe, expecting it to occur in one place only is like leaving a loaf of bread and expecting exactly one slice to go moldy. Life just happens here - thermodynamic math has shown that amino acids simply will be built anywhere their components can be found. Since those components are on the periodic table, the literal "this is what happens in this universe" list, they're going to be all over. Assuming aliens don't come up with another pattern anyway (increasing the odds again).
Claiming that we're the only life in existence is a combination of ignorance and self-importance that should have a livejournal, not a scientific journal. The important work is getting ourselves out there and seeing who and/or what we can find.
Recent figures place the total number of stars in the Milky way at an astounding three trillion. Which leads to this question, given such a ginormous figure, what does it mean to be rare? Even if the Earth is a one in a million occurrence, that means there are still 3 million Earthlike planets in the Galaxy (assuming one Earthlike planet per star).
On the other hand, if the Earth is a one in a billion occurrence, then there are still 3,000 Earths in the Milky Way.
We also have to keep in mind that the 3 trillion stars only accounts for what exists right now. There have been well over a billion trillion stars in our past Universe. As Charles Lineweaver of the Planetary Science Institute and the Research School of Astronomy and Astrophysics at the Australian National University has noted, planets began forming in our Galaxy as long as 9 billion years ago. We are relative newcomers to the Galaxy.
Recent breakthreoughs in the chemical analysis of the Universe suggests that we live in a universe exceedingly friendly to life. What we see in the physical laws and condition of the universe runs contrary to the expectations of the Rare Earthers.
Indeed, we are discovering that the Galaxy is littered with planets. Scientists have already cataloged well over 500 extrasolar planets -- a number that increases by a factor of 60 with each passing year. Yes, many of these are are so-called "hot Jupiters," but the possibility that their satellites could be habitable cannot be ruled out. Many of these systems have stable circumstellar habitable zones.
And shockingly, the first Earthlike planet was discovered in 2007 orbiting the red star Gilese 581. It's only 20 light-years away, 1.5 times the diameter of Earth, is suspected to have water and an atmosphere, and its temperature fluctuates between 0 and 40 degrees Celsius.
If we are one in a billion, then, and considering that there are only 0.004 stars per cubic light-year, what are the odds that another Earthlike planet is a mere 20 light-years away?
Indeed, given all this evidence, the Rare Earthers are starting to come under attack. Leading the charge these days is Alan Boss who recently published, The Crowded Universe. Boss estimates that there may be billions of Earthlike planets in the Milky Way alone.
"I make the argument throughout the book that we already know that Earths are likely to be incredibly common—every solar-type star probably has a few Earth-like planets, or something very close to it," says Boss. "To my mind, at least, if one has so many habitable worlds sitting around for five billion or 10 billion years, it's almost inevitable that something's going to start growing on the majority of them."