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Rare Earths and Life in the Universe
Feb. 23rd, 2006 07:09 pmIn the book, Rare Earth: Why Complex Life Is Uncommon in the Universe, authors paleontologist Peter Ward and astronomer Donald Brownlee put forth the hypothesis that Earthlike planets are rare, almost unique. Lots of critiques have been leveled against their work, some accusing them of "intelligently designing" their hypothesis, to the fact that they were saying that you won't find another world exactly like the Earth, (ignoring all the other possible worlds that could harbor multicellular life).
I think the biggest problem with their hypothesis is that they ignore how persistent and resilient life is. They make the claim that if there is life, it will be pond scum, not very evolved pond scum at that.
Why? Because the world it spawned on will not be stable, either due to a lack of a large moon to stabilize the planet's axis, to a large Jovian to sweep the junk out of the system.
Sounds like it could be true doesn't it?
Trouble is if you look at the history of life on Earth, for most of its four and half billion years of existence, life on the Earth has been... pond scum. Now some of that pond scum made oxygen, and some of that pond scum was capable of surviving in an oxygen atmosphere, but for the most part, it was unicellular and was pond scum.
Why? Because for most of life's existence on Earth, there were no major environmental pressures to evolve. In fact the only time life changes, evolves, is when there is pressure, there is change in the environment. Six times after the formation of the moon, the Earth was hit by Earth sterilizing impacts: the surface of the Earth was scoured by intense heat. But life survived, deep in the surface of the Earth, where the surface temperatures never reached.
The Earth froze over twice in its history, after the first, eukaryotes evolved, after the second, we had the Cambrian explosion of life after the second. Every time life on Earth is shoved into the corner and forced to survive or die, it survives and comes out swinging when the pressure is gone.
What does this mean for life on a moonless world for instance? It means that life on that world is shoved into the corner on a regular basis, forced to evolve or die. Life on that world will be very hardy, more than likely multicellular, and more diverse than life is on Earth. It means we shouldn't be surprise when we find that other habitable worlds out there are full to the bursting with life.
Rare Earth? Yes, our world is rare, life had it easy here, and took its time to evolve. Life elsewhere grew up in the streets of evolution, and it's raring for a fight.
I think the biggest problem with their hypothesis is that they ignore how persistent and resilient life is. They make the claim that if there is life, it will be pond scum, not very evolved pond scum at that.
Why? Because the world it spawned on will not be stable, either due to a lack of a large moon to stabilize the planet's axis, to a large Jovian to sweep the junk out of the system.
Sounds like it could be true doesn't it?
Trouble is if you look at the history of life on Earth, for most of its four and half billion years of existence, life on the Earth has been... pond scum. Now some of that pond scum made oxygen, and some of that pond scum was capable of surviving in an oxygen atmosphere, but for the most part, it was unicellular and was pond scum.
Why? Because for most of life's existence on Earth, there were no major environmental pressures to evolve. In fact the only time life changes, evolves, is when there is pressure, there is change in the environment. Six times after the formation of the moon, the Earth was hit by Earth sterilizing impacts: the surface of the Earth was scoured by intense heat. But life survived, deep in the surface of the Earth, where the surface temperatures never reached.
The Earth froze over twice in its history, after the first, eukaryotes evolved, after the second, we had the Cambrian explosion of life after the second. Every time life on Earth is shoved into the corner and forced to survive or die, it survives and comes out swinging when the pressure is gone.
What does this mean for life on a moonless world for instance? It means that life on that world is shoved into the corner on a regular basis, forced to evolve or die. Life on that world will be very hardy, more than likely multicellular, and more diverse than life is on Earth. It means we shouldn't be surprise when we find that other habitable worlds out there are full to the bursting with life.
Rare Earth? Yes, our world is rare, life had it easy here, and took its time to evolve. Life elsewhere grew up in the streets of evolution, and it's raring for a fight.
