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Rare Earth? Plausible or not?

Willmark

Well-Known Member
Original Poster
(Mods: I posted this here as there seemed to be no other places for a topic of this nature. Please move as needed if you feel otherwise).

First background: I'm NOT approaching this from a philosophic or religious matter; thats a different thread if someone wants to start it. I usually start this thread on various other forums I've frequented over the decades to gain insight into how others view our origins.

For a long time like most people who graduated high school and/or college the Copernican model of the universe and the fact that Carl Sagan solidified this in the 90s meant that this has been the prevailing planetary/galaxy/universe theory. I.e we are not that remarkable, not that special, not that unique. For along time I thought that made the most sense.

But what if the reverse is true? What if the Earth is just that, especially when you follow the path that leads to us. What if the Earth is freakishly rare to the point of being a statical improbability? Unfortunately, it gets lumped into religion, but that is not where I'm going. So for those not in the know this is theory and where it really gained momentum:

https://en.wikipedia.org/wiki/Rare_Earth_hypothesis
https://en.wikipedia.org/wiki/Rare_Earth_(book)

Before getting into the reasoning I'd like to point out this is talking about higher life forms, not-single celled which I would suspect is quite common in the universe; its the idea that the Great Filter is what prevents life from leaping forward and also ties into the Fermi Paradox. This is hardly controversial given the scope of the galaxy let alone the universe.

Some Rare Earth prerequisites:
1. Life in single celled form is probably very common across the cosmos.
2. The universe is filled with billions of galaxies which represent untold millions? billlions? of possibilities for life to arise.
3. However simply because the numbers are so large that doses not neccisarily mean complex life is common.
4. Time on a galactic scale (more on that at the very end).

So consider the formation of the Earth and to why it might be mind staggeringly rare:
1. In a mature fairly stable galaxy: the Milky Way.
2. Positioned just right in the galaxy (i.e "Galactic Goldilocks") not too far out relative to the center and not too close in where stars death (super novas) and star formation means dense areas and more gamma ray bursts and the like.
3. No super nova potential or capable stars within 30 light years of Earth over the last 100 million or so years. especially during the last few millions years as hominids starting evolving to us. If there were gamma ray output would have laid waste to the Earth.
4. A main sequence star with just the right temperatures and very stable relative to its galactic counterparts. let alone a single star as evidence suggests that binary star groups are the norm.
5. The Solar system in a largely uninhabited area of our galaxy. We're in the galactic suburbs with no real neighbors, at least in high concentrations relative to the galactic core.
6. The path of the solar system near the galactic ecliptic with very little protuberances in a galactic revolution of Sun nor do we pass through too much galactic medium during said relation for the most part.
7. A main sequence star that rarely has major variations in it's output.
8. A terrestrial planet with an immense iron/rocky core relative to its size enabling a strong magnetic field for the deflection radiation.
9. An active hot inner core producing plate tectonics.
10. A large moon relative to the size of the Earth to slow down the rotation of the Earth and especially in the early billion or so years of the Earth's existence producing massive tides which may have caused the leap from single cell to multi cellular life.
11. An axial tilt caused by the same collision that produced the Moon (i.e the Theia collision) thereby producing seasons. This gives enough variation to help the evolutionary process.
12. Planet with large amounts of liquid water.
13. A largely stable path within the habitable zone of its parent star. The Earth is not perfectly in this zone but close enough (we're almost too close).
14. The presence of large gas giant(s) in the outer solar system to attract planetismals, meteors and asteroids. One criticism of the rare Earth hypothesis is this is not required. That may be true but Juptier's massive gravity, second only to the sun in the solar system is boon mostly for the Earth.
15. Seasonal changes that are neither too long nor too short.
16. A "relatively" low number of mass extinctions on Earth (as far as we can tell). Although we can't know just how common this is.
17. The "right" extinction at the right time to allow for mammals to becomes the ascendant animals on Earth.
18 The right climatic conditions to get our ape ancestors out of the trees and onto the savanna.
19. The fact that we used to be tree dwelling with means we needed good hand-eye coordination, spatial reason and dexterity leading to a larger brain.
20. Walking bipedal and opposable thumbs. Again the moon helps with the first as wind conditions on an Earth with no moon would mean it would be very unlikely that trees let alone animals would grow very tall.
21. A large brain relative to the body of said primates. A large brain is an expensive thing develop when considering claws, sharp teeth and speed for survival being more important; we have none of those in relation other animal species.
22. The right amount of proteins to enable the feeding of said brain which is very hungry in terms of calories.
23. A relatively stable environment during the divergence of hominids from the apes.
24. A upheaval in the environment that put stress on the hominids a million years ago to spread out, but not enough to wipe them out.
24. The ability of communication and speech.
25. Discovering fire and harnessing it at just the right time.

There are more, but these are the main ones that had to happen at just the right time to get to us. So when you look at the Rare Earth hypothesis against the Great Filter it leaves us with the very real possibility that despite the mind-staggering scale of the galaxy, let alone the universe; what if complex life is likewise mind staggeringly rare? In other words the conditions for life are probably extremely common in the universe but the confluence of events that gives rise to the possibilities of complex life just aren't that common. That gives us pause and it seems to make certain segments of the scientific community uneasy because of what that implies: the reverse of we are not unique as a possibility.

Next compare the Fermi Paradox and the Great Filter: https://en.wikipedia.org/wiki/Great_Filter

Ideally, we would hope (as a species) that we are through most if not all of the barriers presented, but that also leads us to another part of this whole idea I alluded to in the first part of the post: time, as in a galactic or universal scale. Often it seems that time is the factor that is often forgotten. If the universe is as teeming with life we should have seen signs of it by now (the Fermi Paradox) given the age of the galaxy. The lack of signs suggest that either there aren't any civilizations right now, they are extinct or we are indeed the first. The last part I think is where scientists and laymen alike struggle with because that has some very deep concerns for us as species: fairly primitive hominids that can barely contain their more destructive tendencies. But speaking galatically as a whole that would be very good for us meaning that there would be no advanced civilizations that are far ahead of us.

Now all of this could be argued that all these unlikely events only applied to the evolution of upright apes but life in the universe is bound to be similar in origin if for no other reason than chemical as very few other elements have the ability that carbon does in terms of life.

So where does that leave me? To me I think the conditions for life (in various forms) is probably very common in the universe, but the conditions for complex life at least as we know the likelihood of is so mind-staggering remote that we just can't wrap our brains around it. Then add the element of time? Lets say that yes there is life out there as postulated by the Drake equation with even "average" numbers plugged in, but given the vast timescale we're talking about, what if were the only ones RIGHT NOW?

I'd also like to add the qualifier of life in our galaxy as the main part to this line of reasoning/post. For all intents and purposes, life in other galaxies (excepting our Local Group) even if there in massive numbers isn't really going to matter as its so far away (and getting farther). That is unless some civilization has technology that allows worm-hole/warping of space-time so prevalent in science-fiction because then all bets are off ;)

I'd like to hear others thoughts on this.
 
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Willmark

Well-Known Member
Original Poster
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Bump since this is now in the correct forum.
 

Willmark

Well-Known Member
Original Poster
I should add since I posted this in the Fall I've read a lot more about it and a lot more podcasts/videocasts on the subject. Some scientists have offered up a theories as to why certain parts I listed above are false or are actually harmful (Jupiter). But there is truly no way to fully discount the theory.

As I get older I also find this statement by Sagan to put his ideas on the Mediocrity Principle into a contradiction: "Faith is belief in the absence of evidence". There are no signs of intelligent life other than us (and that’s debatable) so isn’t his backing of the mediocrity principle... faith?

The Milky Way is old enough that it should have been colonized many times over in a relatively small time scale (millions rather than billions of years). Yet it's not.

Add to the fact that a civilization that might have existed if it were but say 500 years ahead of where we are now in terms of technology? The galaxy should be swarming with Von Neumann probes, yet its not.

Lastly I am aware of Sagan's "the absence of evidence is not the evidence of absence" quote but I think to a degree that he could be just as rigid in his own way as those he decried.
 
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scorp16

Well-Known Member
I mean - is it plausible? Sure. No one has the correct answer (or at least cannot scientifically prove it). I've done a lot of reading/watching/learning about a number of theories along these lines. Not that I necessarily buy into any one of them as "yeah, this is the one." But they're interesting nonetheless. Some seem "way out there" until you start understanding the concepts a bit better.

Whether its Kaku and/or Brian Greene on string theory. Everett's Many World's Interpretation, and associated offshoots like Tegmark's Quantum Suicide or Quantum Immortality. Bostrom's Simulation argument which has buy in from DeGrasse-Tyson, James Gates and others. Or a number of other T.O.E's (or partial T.O.E's) by accredited and respected physicists and theoretical physicists.

Then we get into entanglement and superposition (the basis for quantum computing), the work being conducted at CERN (the discovery of Higgs Boson a/k/a The God Particle), double slit experiment (which defied logic). And you get back to the place you started and say "I haven't a clue."
 
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Willmark

Well-Known Member
Original Poster
I mean - is it plausible? Sure. No one has the correct answer (or at least cannot scientifically prove it). I've done a lot of reading/watching/learning about a number of theories along these lines. Not that I necessarily buy into any one of them as "yeah, this is the one." But they're interesting nonetheless. Some seem "way out there" until you start understanding the concepts a bit better.

Whether its Kaku and/or Brian Greene on string theory. Everett's Many World's Interpretation, and associated offshoots like Tegmark's Quantum Suicide or Quantum Immortality. Bostrom's Simulation argument which has buy in from DeGrasse-Tyson, James Gates and others. Or a number of other T.O.E's (or partial T.O.E's) by accredited and respected physicists and theoretical physicists.

Then we get into entanglement and superposition (the basis for quantum computing), the work being conducted at CERN (the discovery of Higgs Boson a/k/a The God Particle), double slit experiment (which defied logic). And you get back to the place you started and say "I haven't a clue."
Ha indeed.

The thing that has been most on my mind is “what if Sagan is wrong, as in 180 degrees wrong” and the Rare Earth hypotheses is indeed correct?

That the possibility of “intelligent life” aka us (although I don’t really think we’re that much more advanced than our simian ancestors in a lot of ways) is mind staggeringly rare. As in so rare, our primate brains can’t comprehend it.

It seems to me Sagan was basing his theories on “law of large numbers” as it were; that it’s improbable that we’re alone simply because the sample size is so large (aka the universe).

Asimov said it best:
“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”
 
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Willmark

Well-Known Member
Original Poster
I should also add that the Universe is old enough that if it’s possible to have FTL tech/worm hole jumping tech that it should have been invented by now.

It also speaks to that without such tech we’re only realistically ever talking about our own galaxy and Andromeda as it gets closer over the next four billion years due to all the other galaxies moving “away from us.”
 
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scorp16

Well-Known Member
Ha indeed.

The thing that has been most on my mind is “what if Sagan is wrong, as in 180 degrees wrong” and the Rare Earth hypotheses is indeed correct?

That the possibility of “intelligent life” aka us (although I don’t really think we’re that much more advanced than our simian ancestors in a lot of ways) is mind staggeringly rare. As in so rare, our primate brains can’t comprehend it.

It seems to me Sagan was basing his theories on “law of large numbers” as it were; that it’s improbable that we’re alone.

Asimov said it best:
“Two possibilities exist: either we are alone in the Universe or we are not. Both are equally terrifying.”
Asimov is correct. Assuming ours is the only universe.

The truly terrifying one for me is Nietzsche's Eternal Recurrence. If ever proven time was cyclical and not linear I'll feel a little uneasy.

Speaking of Asimov. The Asimov debates are really good if you haven't watched them. I like 2016 and 2018.
 
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