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Researchers Say The Aliens Are Silent Because They Are Extinct (theconversation.com)
HughPickens.com writes: The Conversation reports that according to research by Dr. Charles Lineweaver and Dr. Aditya Chopra, a plausible solution to Fermi's paradox is near universal early extinction of life on exoplanets, which they have named the Gaian Bottleneck. "The universe is probably filled with habitable planets, so many scientists think it should be teeming with aliens," says Chopra. "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." According to the researchers, 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. About four billion years ago, Earth, Venus and Mars may have all been habitable. However, a billion years or so after formation, Venus turned into a hothouse and Mars froze into an icebox. Even if wet rocky Earth-like planets are in the "Goldilocks Zone" of their host stars, it seems that runaway freezing or heating may be their default fate. Large impactors and huge variation in the amounts of water and greenhouse gases can also induce positive feedback cycles that push planets away from habitable conditions. The difference on Earth may be that as soon as life became widespread on our planet, the earliest metabolisms began to modulate the greenhouse gas composition of the atmosphere. "The emergence of life's ability to regulate initially non-biological feedback mechanisms could be the most significant factor responsible for life's persistence on Earth, conclude Lineweaver and Chopra. "Even if life does emerge on a planet, it rarely evolves quickly enough to regulate greenhouse gases, and thereby keep surface temperatures compatible with liquid water and habitability."
"Even if life does emerge on a planet, it rarely evolves quickly enough to regulate greenhouse gases......"
Rarely? What is the sample size for the statistics?
Yep, it's the distance.
And whatever constitutes "teeming with aliens". Is that 10 planets per galaxy? 100? 1,000?
And the time involved. How long ago did life start on Earth? How many mass extinctions have there been? Would ANY of those have been detected by aliens on their home planet using technology equivalent to ours?
The Fermi "paradox" is based upon alien expansion. Which is, in turn, based upon tech advances that we don't have.
The galaxy could be "teeming with aliens" that we cannot detect and that we cannot reach with our technology. Nor can they detect us or reach us.
Just some of the things that had to happen for us to be where we are now:
1) Life had to evolve
2) Multicelluar life had to evolve (this took a billion years after life itself arose so is probably not a forgone conclusion)
3) Life had to climb out of the oceans (dolphins might be smart but they won't be building any rockets with their flippers anytime soon)
4) Suitable intelligence had to evolve. Had it not been for the asteroid the dinosaurs would still be in charge.
5) Humans had to survive numerous climate changes and if the genetics is to be believed we almost died out and everyone today comes from a very small population who made it.
6) Farming had to be created to allow people to do something other than hunting and gathering.
7) For the industrial revolution plenty of freely available energy had to be lying around near the surface - ie coal. You can't melt iron with wood fires.
8) Someone had to invent radio.
I'm sure there are dozens of other things that could fit inbetween those points but my basic point is that a technological civilisation than can broadcast information out from his own planey is very VERY unlikely. IMO we could well be the only one surrounded by planets full of the equivalents of bacteria and jellyfish but little more.
For four billion years, life on Earth was microscopic blobs of goo.
Then 600 million years ago - BAM - complex life emerged pretty much in the blink of an eye.
We have no idea how likely that transition to complex life 600 million years ago was - we have a sample size of ONE.
Now go back an read my first sentence: For four billion years, life on Earth was microscopic blobs of goo.
That four billion years was about half the expected lifetime of the Earth. The probability that complex life evolves may very well be infinitesimally small. WE DON'T KNOW.
Believing the universe must be teeming with intelligence is based on nothing more than faith.
All speculation about alien life tends to founder on the issue of small sample size, but already we observe that our machines 'like' space and extraterrestrial surface environments much better than our squishy carbon-based bodies do. So perhaps the leading candidate for LNAWKI would be something like our silicon-based emissaries. If the same process has been going on elsewhere we may find that (a) the most likely aliens we encounter will be machines, and (b) the encounter will be by our own machines.
Even if there were advanced civilizations on only 1% of all the planets, that would still be millions or more.
To believe there are no other advanced civilizations out there, that they are somehow obligated to come pay us a visit, or that they blew themselves up, is pretty fucking arrogant of us.
When you move into a new neighborhood and the neighbors don't come to visit you, that doesn't mean they don't exist
When Fascism comes to America, it will call itself Anti-Fascism, and tell you to give up your guns.
The universe is still very young by cosmological time scales.
The evolutionary timescale is the one that matters for the development of life and based on our sample of one this seems to be a lot, lot shorter than cosmological timescales although getting to the multi-cellular stage took a while so it is possible we were just lucky.
True but usually you can see some signs that there are neighbours there such as hearing their car or the music they are playing. In our case we have not heard anything so either we are not listening in the right way, they make practically no 'noise' or they don't exist at least close by.
When humans first invented radio, we broadcast strong simple signals because our technology was primitive. These signals would be detectable from very long distances away. But we are rapidly moving to much weaker and complex transmissions. This has the benefit of using far less power, and has much greater bandwidth. But it also makes the signal harder to detect and almost indistinguishable from background noise. There was only a 150 year window from when we started to transmit, and when our transmissions became indistinguishable from static. Compared to the age of the Universe, that window was a very tiny blip.
wild, speculation like this is a waste of time
Wasting time on wild speculation is the whole point of Slashdot.
Space nutter detected. Evidence: "Suggests dismantling our moon".