There Probably Have Been Aliens
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1 in 10 billion trillion at first seems like such an incomprehensibly low probability that our first gut reaction is, "Well then of course there's no way it could be the case."
But then we must bear in mind that abiogenesis (the creation of life from non-life) might consist of a series of independent events, each of which is improbable. And guess how you figure out the probability of all of those events occurring:
P(A and B) = P(A) * P(B)
So, what's 1 in 10 billion trillion? 10^-22?
Well, if you have a mere eight improbable things that must all occur, and each has a probability of 1 in 1,000, the total probability is now at 10^-24.
Hmm, 10^-22 doesn't seem quite as incomprehensibly low anymore, does it?
Aside from that, we really have to think hard about what probability means in the context of the snippet quoted above.
As statistician to the stars William M. Briggs points out, "There just is no such thing as unconditional probability, or probability without respect to any evidence."
Because we have insufficient evidence to establish what the frequency of abiogenesis is, the quoted snippet basically could be rephrased:
For all we know, the probability of evolving a civilization on a habitable-zone planet could be 10^-22 or 10^-222 or 10^-2222, and if it's less than 10^-22 then we are not the first.
Isn't it strange that in a certain sense, the probability of each of those probabilities being correct is essentially the same, given our current insufficient level of evidence?
It's one thing to say there might have been abiogenesis elsewhere that created something like the simple self-reproducing energy machines that bacteria and archaea are. It's another to claim that there is some inevitable progression from that to complex multicellular life. In my opinion this is a very teleological, very 'progressivist' notion of evolution that implies that one inevitably follows from another, and it is not borne out in the reality of what we know so far about happened on earth and what follows from first principles.
There may be a lot of complex, self-reproducing systems in the universe. It's arrogant to assume that any of them have to look anything like what we call "life" unless by life we mean the simplest single cell organisms. [edit: In fact it looks like simple prokaryotes evolved _twice_ on earth a "short" distance in time apart].
Now, highly complex multicellular life seems to share common descent. But that likely has more to do with predation than anything else. Further single called organisms preform horizontal gene transfer to both other single called life and multicellular life, making things impossible to trace back.
Of note life showed up very close to as soon as possible on early earth. So, similar events may have happend 30+ times. However, the first time life shows up it can spread easily, the second time it's likely food.
Now, 36 basis is extremely short. I don't think anybody believes there's anything that size that able to reproduce. Last time I checked, the smallest known self-reproducing chromosome had around 160 basis. That is, it had a probability of ~10^-96 of appearing between all 160 basis chromosomes. (And remember, there are ~10^80 atoms on the observable Universe...)
So, really the question is how many possible ways can you get self replication not how complex is the first example.
You will need a huge amount of self-replicating chromosomes between 180 and 160 basis to make up for the increased size - it's known that self replication is not common, but I don't think we know that to a 10^-22 certainty either, so all that can still be wrong.
Anyway, there isn't a lot to argue about self-replicating on that context. It means that this chromosome is able to create copies of itself in a RNA-rich ocean. It can require light for that, or a big thermal gradient, but not both. The exact conditions of the ocean are, AFAIK, unknown, but things like your example do not fit.
However, life showed up on earth at a very early stage which suggest it has a relatively high probability over a planets lifespan. Without other information to go on earth is probably topical and life generally shows up within the first 500 million years watter shows up.
> However, life showed up on earth at a very early stage which suggest it has a relatively high probability over a planets lifespan.
1 - That's a good explanation. As good as any other.
2 - Alternatively, life's appearance depends on something that only existed in that short timespan (both light and a big temperature gradient at the same place is a great candidate).
3 - Or life requires some time to evolve so intelligence can only appear on planets that life was early.
4 - Or, you can mix #2 and #3 at varying amounts.
Nucleic acid replication involve them being both dual and single base sequences on different stages. So the difference between "bases" and "base pairs" is meaningless.
But, as you say, with respect to life (or at least complex multi-cellular life), we just don't know. But the Drake Equation encourages thinking like, even it's it's a 1 in a trillion chance effectively zero!, we'd have all these aliens running around. Because 1 in a trillion = 0 is pretty much what we're informed by day-to-day usage and intuition.
Avogadro's constant is 6.022 x 10^23 [1]. There are a hundred billion sets of a trillion constituent particles in ever mol of anything. A reaction that happens to water once in a trillion years would occur 20,000 times a second for each 18 mL of water.
The other big question is how long technological civilizations last. Ours is less than 200 years old. (A useful starting date is 1830, when the Liverpool and Manchester Railway started carrying paid passengers. That's when powered technology got out of beta.) How long before we run out of cost-effective nonrenewable resources? Probably a few hundred years, tops.
I'd consider as the reasonable starting date, when we discuss about the alien civilizations on the distant planets, the day the radio communication starts to exist.
So we're some just for some 110 years capable of sending and receiving any radio message. If we move to the "capable of receiving the faint message from the big distance" it's more like just some 60-something years.
Also note that as we move to using the digital, high-density, compressed and especially encrypted messaging, the transmitted messages look more like the noise than the signal.
I made that point to a SETI guy who was giving a talk. They were looking for "carriers". Nobody uses carriers much any more. It's a huge waste of power and bandwidth. There are much more efficient ways to get synchronization. Everything later than analog TV is low-carrier or no-carrier. Unless you have some idea of what to look for, the signal looks like white noise.
Which doesn't have to be cleverest thing to do, and maybe we should also be worried enough to care.
To make a computing analogy, maybe taking part in the "galactic internet" without the latest "firewalls" and "spam filters" can be really the matter of life and death for the whole planet ("what you didn't know that we send the 'energy beam of death' to those who don't respect the protocol, well the whole galaxy knows, and you won't do it again, heh, heh" even if we avoid other trivial issues like a galaxy "superhighway" which has to be constructed in our neighborhood or simply that humans are maybe very good to be used as food or work animals from the point of the possible invaders). So we should learn about the others but really try to stay as undetected as we can until we know more. And maybe other aliens think like this paragraph argues too.
That's a religious argument. It's unprovable and unknowable.
Aition: a tale devised to explain the origin of a religious observance
Even from the perspective of fundamentalist Christianity, which I'd hazard a guess many people would tend to assume to be the most hostile to the idea, there's no reason to believe there aren't aliens somewhere out there. It gets more complicated if fallen humanity is allowed to interact with those other species, but even then you can argue either way within that axiom set.
Really, I'd say the reason that most of us, religious or otherwise, believe "we are the only life in the universe" (or "observable universe") is because that's the simplest explanation that fits the facts. It may well be wrong, but at the moment, there's not even a whiff of convincing evidence that we are not alone, even as we must also all acknowledge there's plenty of room in the "gaps" for alien life, even intelligent alien life, even intelligent alien life that spans several star systems. It depends on how far away we're talking, but even fairly close to home it could take a Kardashev level 2.3-ish at a minimum for us to be sure. No matter what your ideological disposition may be, there's just a huge "NO DATA" out there right now.
So? Why would these Christians be shaken in their belief, when there were already written considerations about the "original sin" and "Gospel" for the aliens?
I don't understand what your disagreement is.
Note: the "World" of the Bible is just a piece of the Mediterranean Sea and the piece of the Near East. Ditto for Quran. Even the whole continent (America) is not known among the people of these books, so these apparently "eternal" books don't know about that fruitful continent either.
But these faiths survived the discovery of the America. And interestingly, the more "fundamentalist" believers actually left Europe and kept their fundamentalism in America and the effects of that we feel even now.
At least the result was that the modern science (trust what is, not what's in the "eternal" books) progressed in the lands that used the "new" resources.
Well, if at first you don't succeed, try, try again. Right?
We have to assume that any creation-capable deity has to be patient enough to try the cosmic life-evolving minigame at least twice before quitting forever, right?
"This game sucks. I never should have programmed it. After a couple billion years, I always get the atheist bad ending, no matter what I try. One star."
https://www.scientificamerican.com/article/are-we-living-in-...
http://www.bbc.co.uk/earth/story/20160901-we-might-live-in-a...
DNA
With regards to aliens - i see the Bible as exactly historical document of such an unplanned/unauthorized contact by an alien observer gone rogue. Contains all elements, like medical nanobots, [food]replication, specific lessons that violence is the main obstacle of civilization development, blue light sterilizing the cave with decontamination workers in white overalls and some devices on their backs (angels :), etc... Hunt for the lost sample of the alien's DNA - Holy Grail- which also contains those nanobots.
The probes reached their replication limit, then went into hibernation when they phoned home, and subsequently failed to receive a reset signal. Or perhaps they simply propagate too slowly. Imagine if the Morris worm spread only half as fast as the growth of the Internet itself.
The explanation I have heard repeatedly goes something like:
"This equation shows that there should be [massive number] of alien civilizations in the universe. But where are they?"
This seems to assume that, given the density of civilizations throughout the galaxy we can determine from [massive number], we should be able to observe other advanced civilizations. But is that true? If there was a civilization as advanced as we are somewhere in e.g. Alpha Centauri, would we be able to detect them?
The usual response I think is that the timescales and distances involved are simply still too big / spread out that we're still searching for the metaphorical needle in the haystack.
Its also worth mentioning that FTL travel probably isn't in the cards and even if we consider exploratory advanced civilizations working for billions of years, they most likely would not get far by the time they hit their extinction event anyway. Even an incredible case of E.T. exploring an entire galaxy would be an achievement without peer, but ultimately would leave 2 trillion other galaxies unexplored. Even that would be a stretch considering a galaxy is 100,000 long/wide and in 3 dimensions. Even if you could have a practical 1/10th lightspeed ship, you're looking at 1bn years right there. The universe is only 13bn years old so this civilization could explore maybe 3 or 4 galaxies at most considering inter-galaxy distances.
Another possibility is that we've simply explored in the wrong directions.
___________________________________________
| Us --> Exploring this direction
|
| [Millions of lightyears of space between Us and Them]
|
| Them
| |
| |
| |
| v
| Exploring this directionThe observable universe has an estimated diameter of 93 billion light-years. A few million years might be enough to explore nearby galaxies. For example, to explore just our Local Supercluster you would need approximately 65,000,000 years [0]. Travelling at the speed of light.
E: Virgo is further than Ursa Major. Updated 55,000,000-->65,000,000.
E2: I always refer people to this video in regards to aliens, space, and time. I forgot to in this post, so here it is now: https://www.youtube.com/watch?v=HPl10L40pBM
[0] https://upload.wikimedia.org/wikipedia/commons/e/e2/Local_su...
What about the people who ride on ships from Southport to the Americas to plant crops or cotton?
But most expansion beyond the solar system would be inter-generational anyway, so it's more like people who are born on a spaceship and told by their parents they're a pioneer to an uninhabited world, and can't turn around.
I don't think we have enough information to tune the values in the Drake equation to make meaningful predictions. We'd need observations to do that, but the observations are, as you point out, difficult enough that we don't know if they're absent or we just can't see them yet.
UPDATE We have had computers for less than a 100 years, and with i2p we hav already created a technoligy that would hide us from other aliens
Is there a term in the Drake Equation for our level of certainty that the Drake Equation isn't missing some terms?
There are good reasons to believe that intelligent civilizations are short lived (compared to cosmological time scales). So the absence of radio signals from nearby planets doesn't mean it's not worthwhile to send a probe there to see if there are ruins or something.
Whoa there... The SETI people whom are only occasionally telecom engineers have a thing about scanning for the simplest carrier waves and that's it.
Note that we only broadcast vestigial sideband amplitude modulated video signals which had a lovely strong stable carrier for oh maybe 50 years and we don't broadcast analog TV anymore. Lets be honest that the future for broadcast radio/TV doesn't look particularly bright so even if the aliens had the bright idea to use 8VSB modulation when the USA is in view or OFDM when the euros are in view then they still would see total radio silence from us in "a couple years". Terrestrial broadcasting is pretty much done.
You need to add a term to the SETI equation that your average civilization is only going to broadcast "SETI@HOME" compatible radio signals for maybe a century, probably less.
There's a section of Kraus classic radio astronomy textbook indicating that detecting Earth during the peak of the analog TV era would still have been pretty tricky if the aliens used our own "SETI@HOME" modulation.
You feed a baseband thru the wrong demod and you just get distorted noise.
Broadcast seems kinda dead as a concept in a packet switched social media era. The aliens and us are not going to understand each other on some rather fundamental levels making USA 2050 compared to USA 1950 look fairly trivial. Wait... you still use radio waves for communication instead of high frequency short range gravitic waves? You broadcast to a significant fraction of your unified population instead of social media via low power point to point systems? How... retro.
Earth has made several intentional transmissions (https://en.wikipedia.org/wiki/Active_SETI) but it's unclear if we'll send any more, because they might attract hostile aliens.
This could be a relativistic effect, just like the speed of light appears the same irrespective of frame of reference.
The speculation is moot as long as the record of evidence cannot support within a reasonable confidence interval that only one or more alien civilizations could have produced it.
Guessing with the Drake equation only helps to determine just how much time and funding you would like to provide to projects like SETI, that actually watch for and listen for evidence that would refute the null hypothesis (viz. no civilizations anywhere outside of Sol System).
All the article really says is that if SETI has enough resources to watch the entire sky at maximum resolution for an infinite timespan, it will eventually find something. But I'm certainly not going to sink that much time and money into it. I'd rather put that money into generation ships, sleeper ships, robotic seed ships, permanent space habitats, or some combination thereof.
But I think it stands to reason and always has. After all, this place is old and huge, so...
Obviously, astronomy theories don't know much about these things, as the sheer number of stars with planets, and planets in the habitable zones, have come as a big surprise to everyone.
But still, can we say or guess anything about the age distribution of these stars and planets, compared to our earth and sun? Is our sun among the oldest or youngest of those stars which have earth-like planets?
On some far away planet, a circle of far-travelled pulsing light razes with 30 km/s over the clouds, and is interpreted as a answer to the "Where is everybody?" question, missing the grammatically correct point of a decent interstellar conversation. The Question is.. "Where was everybody (when we where around?)"
AKA "Yes, there might have been aliens". Interesting article, sensationalist headline.