I remember Asimov’s conclusion that technological civilization may too widely spread out in time and space for them to get in contact with one another.
Python, as always:
So remember, when you’re feeling very small and insecure,
How amazingly unlikely is your birth;
And pray that there’s intelligent life somewhere out in space,
'Cause there’s bugger all down here on Earth!
Ocean worlds and ice giants are overrepresented in the data at the moment, probably because of the limitations of our observations.
If we just look at the supposedly rocky worlds, it is difficult to find any that seem likely to support both open water and regions of dry land. The candidates I’ve looked at are too massive (which probably means they retain more volatiles, and have total ocean cover) or are tidally locked, which means they have one side covered in ice and the other baked dry). Of all the planets discovered so far, Mars and Venus are among the most Earth-like: and that does not bode well for habitability.
I recommend Andrew LePage’s habitability Reality Check website,
which shows that a lot of the worlds regarded as habitable really aren’t, and that some of the ones regarded as inhospitable may be better candidates (but many of these better candidates would require thick atmospheres of greenhouse gases, that would kill any Earth biota). Maybe there are planets with multicellular organisms on these worlds, but they couldn’t look up and see the stars like we can.
One thing that gives me hope is the apparent fact that a planet with a biosphere like Earth may develop some kind of homeostasis, so that the lifeforms on that world adapt to a changing environment and are capable of changing the environment to suit themselves. This is the well-known Gaia hypothesis developed by James Lovelock (101 years old this month), but extrapolated to other worlds. So a planet may appear quite inhospitable when considering its known parameters, but the presence of life could alter those characteristics sufficiently to make the environment much more hospitable.
For instance the Early Earth received much less insolation than nowadays, but was warmed by carbon dioxide and methane; both of these gases now exist only as traces because of biological activity. Have we been lucky, or can the presence of a biosphere make even inhospitable worlds habitable?
Yes, that’s exactly the point; the worlds we can detect so far are mostly close to the parent star or huge, because detecting planets is hard and these are the easiest to detect.
Your inference that small rocky worlds are rare is baseless. You may as well declare that obviously the stars more than a couple thousand light years from us are sterile because we have not detected planets beyond that (IIRC).
On your specific points, I see no reason to rule out ocean worlds or tidally locked planets (an atmosphere would help to smooth out the temperature gradient a lot).
Finally, in recent years our technology has advanced such that we have detected around 100 worlds the same or smaller size than earth. Given the small number of stars where such a detection is feasible right now, the implication is that such worlds are common. See [NASA’s exoplanet catalog](http://NASA’s exoplanet catalog)
Finally finally; I am not at all saying earthlike conditions are common, or that life is, let alone intelligent life. (If I had to guess, I’d say that multicellular life must be extremely rare as that’s the best fermi solution we have right now).
I’m just saying that some of the claims you’ve made are not supported by the data.
Ocean worlds might support macrobiotic life in the depths, but they would find it difficult to build rockets to get off the planet. I have high hopes of finding solitary water-based civilisations in the oceans of such worlds, but they would be unlikely to come and find us.
Tidally locked worlds could, in theory, gave very strong circulatory winds, especially where the planet’s year length is comparable to the day length on Earth. This could extend the temperate zone and allow complex life to develop. But (once again) the presence of moisture-carrying damp air from the dark side would generally cause overcast skies, making astronomy difficult. A worse problem is that red dwarfs tend to flare, so the lifeforms on such a world would be stressed by radiation, often into extinction. The flaring could convert a habitable world into a deadly desert.
That was the basis of an idea put forward by sf writer and actual scientist David Brin. Earth might be right at the inner edge of the habitable zone, and dry enough to have continents, while most habitable planets will be water-worlds, where technology will be much more difficult to get up and running.
This idea is also scary, because global climate change might push us those extra few inches out of the habitable zone.
Brin has written an overview of the Fermi Paradox, which is worth reading.
https://www.researchgate.net/publication/234496344_The_‘Great_Silence’_The_Controversy_Concerning_Extraterrestrial_Intelligent_Life/link/5468f0e30cf20dedafd0d529/download
There are a few possibilities he’s missed, including some which have been formulated since he wrote that paper, but it is pretty good.
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One reason that Earth isn’t a water world may be that we had a late collision that formed the Moon; big collisions like that can spray a lot of volatiles into interplanetary space, and we won’t get them all back afterwards.
There’s basically no way for life to emerge. A biotic origin of life is usually assumed.
In creation myths, indeed, or other scenarios that are regarded as non-scientific. Such a claim should “basically” be supported by arguments, cites, etc.
Scientific views take a different approach: abiogenesis (the natural process by which life has arisen from non-living matter).
Which doesnt happen, and has never come close to meaningfully being demonstrated for organelles so it can be thrown out given the overwhelming odds. The Improbability of Abiogenesis.
Maybe, but the conversation here is not about whether life can arise from non-living matter or not.
If you are interested in this debate, you can initiate a different discussion in Great Debates or some other forum.
Nevermind; I gave a long reply to Dershowitz but then I saw UY_Scuti’s post, and I agree it would be off-topic to go there.
This article suggests that Earth could have formed differently from what current models show. It is possible that only planets with a certain chemical composition should be able to spark life.
Yeah, you have to remember that astronomers are people that consider anything other that hydrogen or helium, like the air your breathe, to be ‘metals’. There are a lot of astronomy terms that just don’t line up with common usage.
There are three things to consider.
- Our primary search for ET has been through SETI, and their search is through a very primitive technology. I have to believe that highly advanced civilizations that have mastered interstellar space travel are using forms of communication that are beyond anything we have developed.
Example: I have decided that there is no life in California because I have been spending 12 hours a day sending up smoke signals from the top of the highest peak in the Rockies, and I have never received a single reply. No one is out there.
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The assumption is that they want to be found and they want to interact with us. That’s pretty damn arrogant. Were I observing humanity from space over time, I would be horrified with the human race. It is a race that is constantly at war. It is a race that is destroying its own environment. It is a race whose population is out of control. It is a primitive race that was throwing spears and shooting crossbows just 1,000 years go. Hell, I AM human, and even wouldn’t want to have anything to do with you!
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We are sure we aren’t being observed now, which is yet another arrogant assumption.
So I think its fair to say we are never going to have actual numbers for all the numbers in Fermi’s equation (until a starship turns up from a Dyson sphere, and even then we just increased the minimum number of interstellar species from from 0 to 1).
But that’s not the point, we can easily come up with perfectly tenable values for the terms in the equation that yield a value of less than one. To me, saying the odds of life forming on a planet (or the odds of life on a planet developing viable interstellar travel) is roughly the same as the odds of a particular arrangement of a shuffled deck of cards is a pretty sensible “finger in the air” estimate. And right there you have a number (10e-68) that would yield a final value of less than zero. There is no paradox.
In fact to me the paradox is why Enrico Fermi, one of the greatest geniuses of an era with a lot of competition for maths/physics genius, and no stranger to very large/small numbers, called this a paradox. When it so clearly is not, and its pretty straight forward to come up with plausible values for the equation that match the observed number of Alein spacecraft (zero).
Agreed. This is a widely-acknowledged issue with SETI but we’re doing the best with what we have.
I am not aware of anyone making such an assumption.
The Fermi paradox simply notes the lack of evidence of ETs; that’s not the same thing at all as expecting them to want to contact us. The lack of evidence is significant, as it seems that a species with technology already plausible to us would be capable of producing detectable probes or megaprojects.
Again, I have not heard anyone make such an assumption. I have only heard people being dismissive of close encounter stories, which is reasonable given the lack of evidence.
But sure, a super advanced species could be sat beside us right now, in the 8th spatial dimension or whatever.
It’s not a solution to the paradox because there are already a plethora of plausible hypotheses of why we don’t see ETs, but the point is, we don’t know which, if any, of these hypotheses is correct.
A common assertion is that a lack of response equates with “not out there”. To me, that’s what it saying.