Why haven't we found aliens yet? Maybe they're all dead
The number of stars in the universe is uncountable. The number of planets potentially even higher. Earth is just one small, pale blue dot orbiting a very average star. The probability that life is abundant in the universe should be high, yet we have located no undeniable signs of life beyond Earth.
This is what is known as Fermi's Paradox. One hypothetical solution is the Great Filter, which proposes that the conditions required for the evolution of intelligent life are rare. According to the hypothesis, at some point during the evolution of life, a wall or filter prevents it from progressing any farther. There may, this hypothesis proposes, be life out there, but it stopped at the bacterial stage (for example).
Aditya Chopra and Charley Lineweaver, astrobiologists from the Australian National University propose a modification on this scenario. Most life, they say, would become extinct before it gets very far along the evolutionary process at all.
Their research has been published in the journal Astrobiology and can be downloaded here (PDF) .
"The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens," said lead author Chopra.
"Early life is fragile, so we believe it rarely evolves quickly enough to survive. Most early planetary environments are unstable. To produce a habitable planet, life forms need to regulate greenhouse gases such as water and carbon dioxide to keep surface temperatures stable."
The hypothesis, which the team has called the Gaian Bottleneck, proposes that, while many planets may have good conditions for the emergence of life, at some point they become unsustainable. As an example, Venus, Earth and Mars may all have had similar conditions 4 billion years ago, when microbial life began to emerge on Earth.
At some point, perhaps up to around a billion years after that, Venus grew too hot to sustain life, and Mars lost its atmosphere and water. Any life that had emerged would have failed to adapt to the rapid changes and become extinct. But it's a little more complex than that. Evidence shows that life on Earth was able to successfully emerge because life itself was making the planet habitable, such as the oxygenisation of the atmosphere caused by cyanobacteria photosynthesising.
To date, the Kepler mission has located some 1,039 confirmed candidate planets, those that meet the rough basic conditions for supporting life. They are rocky, like Earth, and orbit around their star in the Goldilocks zone, not so close that they'd be too hot, like Venus, and not so far that they'd be too cold. Life has yet to be observed on any of these planets. That does not mean it's not there, but The Gaian Bottleneck hypothesis suggests that its presence is unlikely, that extraterrestrial global extinction level events are the norm, not the exception.
"The mystery of why we haven't yet found signs of aliens may have less to do with the likelihood of the origin of life or intelligence and have more to do with the rarity of the rapid emergence of biological regulation of feedback cycles on planetary surfaces," Chopra explained.
NASA believes that extraterrestrial life within the solar system, if there is any, is likely to be microbial. The space agency is looking to Jovian ice moon Europa, the crust of which conceals a vast ocean. If there are hydrothermal vents spewing heat deep beneath the ocean on Europa, there's a chance microbial life has grown and propagated.
This general idea, co-author Lineweaver said, can be extrapolated throughout the universe in many different environments.
"One intriguing prediction of the Gaian Bottleneck model is that the vast majority of fossils in the universe will be from extinct microbial life, not from multicellular species such as dinosaurs or humanoids that take billions of years to evolve," he said.
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I wish people would start coming to the same conclusion about gods. If they (or it) ever existed, they don't anymore, because nothing lives forever.
It is an interesting article. It's not improved by theophobic rhetoric.
Well, a thumbs down to you too, Mr. I Have To Give Every Comment Hal Makes A Thumbs Down.
Hal,
I am unsure what this has to do with gods.
Just an observation.
The hypothesis is flawed. It assumes 1. That all life is carbon based. 2. That life evolves at the same rate. 3. That life in other galaxies have been able to overcome the issue of long distance space travel 4. That they have already been here and found us not particularly interesting.
No offense, but I think these guys do a whole lot more complex research in this area than members of Newstalkers. Calling their conclusions flawed seems a little glib.
Tax carbon based life !
If this "existence" is eternal , in other words did not begin at some point but has always been, why couldn't it be that earth is the only inhabited place within this existence (the universe) ? Neither of those possibilities is more odd than the other.
The existence that has "always been" is considered by the brightest scientific minds to not resemble this current existence at all. Empty space, teeming with the un-coalesced and most basic building blocks of matter, suddenly flashed into the Big Bang - spewing superheated matter across the universe, and instigating the notion of time as we know it. The two environments cannot be compared.
Empty space, teeming with the un-coalesced and most basic building blocks of matter
If it was "teeming with the un-coalesced and most basic building blocks of matter" it wasn't empty. I don't know why people keep misstating that.
It is not empty space. If it were "empty space" , this existence would not have come into being.
Can't get nothing from nothing.
We are so arrogant. Our continual and blatant disregard for the sanctity of life would be enough for me to stay as far away from Earth as possible if I were an alien. Also, there is a lot of evidence that suggest that life on Earth may very well have sprung from cosmic material that landed here on this planet. We have just begun to dig deep into the mysteries of life, and yet we think we are capable of knowing whether life exists in places we can't even visit. I firmly believe that we could have life staring us straight in the face, and we may not even know it. Arrogance and ignorance are not a good combination.
Fermi's Paradox is great fun. It starts so-o-o many unsolvable debates!
My own take is that it would be a very "happy" probabilistic happenstance for us to meet a neighbor. On Earth, it took about three billion years to evolve from bacteria to thinking. (Yes, I know, the use of that word is debatable, but I insist!)
Our own species's history is about three millions years, or one tenth of one percent of the total "life period". In the next three hundred years (an additional one hundred-thousandth of a percent of the total time), we will either destroy ourselves, or reach the stars. By then, our communications will be by gravity waves, or neutrinos, or God knows what... but surely not Marconi's simple radio.
So... if we assume that our own timeline is roughly "standard" for developing species in our galaxy... where other stars may be thirteen billion years old or only a few million... Our tiny window of radio communications has almost zero chances of falling opposite a similar window for some other species... that just happens to be close enough to pick up our weak-kneed signals...
The galaxy probably has millions of intelligent species... but the odds are that they are all either too advanced or not advanced enough to be able to speak to us.
Bad joke, hmmm??
When Fermi's Paradox is considered in conjunction with your theory, the chances of extraterrestrial intelligent life existing and making contact with earthlings becomes something like a Powerball jackpot winner that already won the Powerball jackpot a dozen times. Yet, when you consider the vastness and richness of the universe, it's still a real possibility.
Yet, when you consider the vastness and richness of the universe, it's still a real possibility.
Unless faster-than-light travel is somehow possible, the likelihood of our species being a technological and geographical neighbor to another is vanishingly small. Your argument says that somewhere there will be two species who will meet, and in that, I think you are right.
They have taken over congress...Yes, it's true.
Think ''Manchurian Candidate''.