What paper talks about resolving the fermi paradox using monte carlo methods on probability distributions instead of point estimates 
https://arxiv.org/abs/1806.02404
Dissolving the Fermi Paradox
2018-06-06
Sandberg; Anders; Drexler; Eric; Ord; Toby
<div><div>
 
 
 
 
 
 
 <p><a href="/pdf/1806.02404">Download PDF</a></p><blockquote>
 Abstract: The Fermi paradox is the conflict between an expectation of a high {\em ex
ante} probability of intelligent life elsewhere in the universe and the
apparently lifeless universe we in fact observe. The expectation that the
universe should be teeming with intelligent life is linked to models like the
Drake equation, which suggest that even if the probability of intelligent life
developing at a given site is small, the sheer multitude of possible sites
should nonetheless yield a large number of potentially observable
civilizations. We show that this conflict arises from the use of Drake-like
equations, which implicitly assume certainty regarding highly uncertain
parameters. We examine these parameters, incorporating models of chemical and
genetic transitions on paths to the origin of life, and show that extant
scientific knowledge corresponds to uncertainties that span multiple orders of
magnitude. This makes a stark difference. When the model is recast to represent
realistic distributions of uncertainty, we find a substantial {\em ex ante}
probability of there being no other intelligent life in our observable
universe, and thus that there should be little surprise when we fail to detect
any signs of it. This result dissolves the Fermi paradox, and in doing so
removes any need to invoke speculative mechanisms by which civilizations would
inevitably fail to have observable effects upon the universe.
 </blockquote>
 
 
 </div><div>
 <h2>Submission history</h2><p> From: Anders Sandberg [<a href="/show-email/b6c84768/1806.02404">view email</a>]
 <br /><strong>[v1]</strong>
Wed, 6 Jun 2018 19:51:21 UTC (2,186 KB)<br /></p></div>||||I|||| Skip to main content
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 arXiv:1806.02404 (physics)
 [Submitted on 6 Jun 2018]

 Title: Dissolving the Fermi Paradox

 Authors: Anders Sandberg, Eric Drexler, Toby Ord
 Download PDF
 Abstract: The Fermi paradox is the conflict between an expectation of a high {\em ex ante} probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference. When the model is recast to represent realistic distributions of uncertainty, we find a substantial {\em ex ante} probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.
 Comments: Submitted to Proceedings of the Royal Society of London A; 4 supplements
 Subjects: Popular Physics (physics.pop-ph) 
 Cite as: arXiv:1806.02404 [physics.pop-ph] 
 (or arXiv:1806.02404v1 [physics.pop-ph] for this version) 
 https://doi.org/10.48550/arXiv.1806.02404 
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 arXiv-issued DOI via DataCite 
 

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 From: Anders Sandberg [view email]
 [v1] Wed, 6 Jun 2018 19:51:21 UTC (2,186 KB)
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Dissolving the Fermi Paradox
Date Published: 2018-06-08
Authors:
Anders  Sandberg, Oxford University
Eric  Drexler, Oxford University
Toby  Ord, Oxford University
Abstract
The Fermi paradox is the conflict between an expectation of a high ex ante probability of intelligent life elsewhere in the universe and the apparently lifeless universe we in fact observe. The expectation that the universe should be teeming with intelligent life is linked to models like the Drake equation, which suggest that even if the probability of intelligent life developing at a given site is small, the sheer multitude of possible sites should nonetheless yield a large number of potentially observable civilizations. We show that this conflict arises from the use of Drake-like equations, which implicitly assume certainty regarding highly uncertain parameters. We examine these parameters, incorporating models of chemical and genetic transitions on paths to the origin of life, and show that extant scientific knowledge corresponds to uncertainties that span multiple orders of magnitude. This makes a stark difference. When the model is recast to represent realistic distributions of uncertainty, we find a substantial ex ante probability of there being no other intelligent life in our observable universe, and thus that there should be little surprise when we fail to detect any signs of it. This result dissolves the Fermi paradox, and in doing so removes any need to invoke speculative mechanisms by which civilizations would inevitably fail to have observable effects upon the universe.
1 Introduction
While working at the Los Alamos National Laboratory in 1950, Enrico Fermi famously asked his colleagues: "Where are they?" [1] . He was pointing to a discrepancy that he found puzzling: Given that there are so many stars in our galaxy, even a modest probability of extraterrestrial intelligence (ETI) arising around any given star would imply the emergence of many such civilizations within our galaxy. Further, given modest assumptions about their ability to travel, to modify their environs, or to communicate, we should see evidence of their existence, and yet we do not. This discrepancy has become known as the Fermi paradox, and we shall call the apparent lifelessness of the universe the Fermi observation.
Many hypotheses have been suggested in efforts to resolve the Fermi paradox, for example, that all other civilizations are deliberately concealing themselves, or that they all annihilate themselves before successfully traveling or communicating at interstellar distances. A major difficulty for such hypotheses is that the putative mechanism must be extremely reliable: If only 99 % of other civilizations annihilated themselves, this would do little to resolve the paradox. These hypotheses are thus highly speculative, relying on strong implicit claims about universal alien motivations or social dynamics, when we cannot claim similar knowledge of our own world. These hypotheses are entertained not out of independent scientific plausibility, but because they are seen as potential explanations of he Fermi observation.
Our main result is to show that proper treatment of scientific uncertainties dissolves the Fermi paradox by showing that it is not at all unlikely ex ante for us to be alone in the Milky Way, or in the observable universe. Our second result is to show that, taking account of observational bounds on the prevalence of other civilizations, our updated probabilities suggest that there is a substantial probability that we are alone. Our third result is that pessimism for the survival of humanity based on the Fermi paradox is unfounded.
1.1 The Drake Equation
The key assumption of the Fermi paradox is that the number of sites where alien civilizations could emerge is so large that for any reasonable probability of emergence, some would have emerged and we should expect to have detected one or more of them. This sites × probability approach fits within the well-known Drake equation framework, which we shall take to be the paradigm example of this form of reasoning about the prior probability of ETI.
The Drake equation was intended as a rough way to estimate of the number of detectable/contactable civilizations in the Milky Way (N ) [2] , phrased as a product of seven factors1 :
N = R * f p n e f l f i f c L
Where: R * is the rate of star formation per year, f p is the fraction of stars with planets, n e is the number of Earth-like (or otherwise habitable) planets per system with planets, f l is the fraction of such planets with life, f i is the fraction with life that develop intelligence, f c is the fraction of intelligent civilizations that are detectable/contactable, and L is the average longevity of such detectable civilizations in years.
The Drake equation has been a mainstay in the SETI debate, sometimes being used to directly estimate the number of civilizations in the galaxy, but perhaps more often being used as an analysis tool. For example, it has played a prominent role in debating the rationality of SETI efforts. This approach to the Drake equation is well summed up by Jill Tarter, who said "The Drake Equation is a wonderful way to organize our ignorance" [3] .
But while the equation is often invoked as a way of reasoning about uncertainties and ignorance, the actual practice is often considered to be somewhat suspect. Many papers state that some of their parameter choices are just their best guesses, though this fails to provide an appropriate framework for interpreting the result. It is common to see carefully estimated astrophysical numbers multiplied by these ad hoc guesses. It has been noted that the final results seem to depend heavily on the pessimism or optimism of the authors, falling into the "N ≈ L" and "N ≈ 1" schools respectively. Steven J. Dick provides a typical statement of this worry: "Perhaps never in the history of science has an equation been devised yielding values differing by eight orders of magnitude. ... each scientist seems to bring his own prejudices and assumptions to the problem." [4] Nevertheless, an equation showing the degree of divergence in estimates can be very valuable. The problem is when systematic biases and assumptions dominate the results. As we will see, the fact that answers only span eight orders of magnitude appears to be due to overconfidence -the range should be substantially wider.
While all practitioners acknowledge the great uncertainty around the parameters of the Drake equation, very few incorporate this into their quantitative models. The Drake equation (and related models) are almost always used with point estimates for each parameter, rather than ranges or probability distributions. If the result is used to estimate the chance of ETI in our galaxy (as is common when introducing the Fermi paradox), this can be extremely misleading. It is not enough to claim that the output of the equation is just an order of magnitude estimate: scientific uncertainty about the parameters does not constrain the output to one or even a handful of orders of magnitude. In our view the practice of using point estimates in Drake equation-like frameworks is largely responsible for the continued puzzlement about the Fermi paradox.
1.2 Knowledge claims of point estimates
It is instructive to ask what knowledge claims about the parameters are implicit in the use of point estimates. The answer is that they implicitly claim complete certainty about all the parameters. We shall see that it is this presupposition of certainty that is creating the appearance of a paradox (by falsely representing how certain we are that there are many civilizations out there). In this paper we provide a principled approach to assessing the reasonable uncertainty in each parameter via consideration of what knowledge is being claimed, and to tracking this uncertainty through the calculation, showing how this proper management of our uncertainties dissolves the apparent paradox.
To quickly see the problems point estimates can cause, consider the following toy example. There are nine parameters (f 1 , f 2 , . . .) multiplied together to give the probability of ETI arising at each star. Suppose that our true state of knowledge is that each parameter could lie anywhere in the interval [0, 0.2], with our uncertainty being uniform across this interval, and being uncorrelated between parameters. In this example, the point estimate for each parameter is 0.1, so the product of point estimates is a probability of 1 in a billion. Given a galaxy of 100 billion stars, the expected number of life-bearing stars would be 100, and the probability of all 100 billion events failing to produce intelligent civilizations can be shown to be vanishingly small: 3.7 × 10 -44 . Thus in this toy model, the point estimate approach would produce a Fermi paradox: a conflict between the prior extremely low probability of a galaxy devoid of ETI and our failure to detect any signs of it.
However, the result is extremely different if, rather than using point estimates, we take account of our uncertainty in the parameters by treating each parameter as if it were uniformly drawn from the interval [0, 0.2]. Monte Carlo simulation shows that this actually produces an empty galaxy 21.45 % of the time: a result that is easily reconcilable with our observations and thus generating no paradox for us to explain. That is to say, given our uncertainty about the values of the parameters, we should not actually be all that surprised to see an empty galaxy. The probability is much higher than under the point estimate approach because it is not that unlikely to get a low product of these factors (such as 1 in 200 billion) after which a galaxy without ETI becomes quite likely. In this toy case, the point estimate approach was getting the answer wrong by more than 42 orders of magnitude and was responsible for the appearance of a paradox.
In this paper, we shall look at two different ways of extending this approach beyond a toy model -generating probability distributions for the parameters of the Drake equation based on the variation in historical estimates and doing so based on the authors' best judgment of the scientific uncertainties for each parameter. In both cases, we see an effect like the one in this toy model, making a galaxy (or observable universe) without ETI quite plausible ex ante and thus dissolving any apparent paradox.
It should be noted that there do exist some cases in the literature using estimated uncertainties rather than point estimates, such as treating each factor as uniformly distributed in an uncertainty interval and then convolving them into a final distribution [5] , or treating the system as a stochastic process [6] or Monte Carlo simulation [7] . The probability of life emerging has also been studied in a Bayesian framework [8] . While these papers aim at improving the precision of the Drake equation they do not apply their conclusions directly at resolving the Fermi paradox. It is also possible to use the Drake equation to derive bounds on the parameters using the Fermi observation [9] .
2 Using variation in point estimates to model uncertainty
The literature on the Drake equation contains dozens of point-estimate based calculations for N (the number of detectable civilizations in our galaxy). 2 These estimates span 11 orders of magnitude: from 3 × 10 -4 to 1 × 10 8 . While each estimate does not contain information about its uncertainty, one could use the variation in the estimates as a proxy for uncertainty in the result. We can do even better if we decompose these estimates into the estimates for each of the parameters and then recombine them in different ways. This gives us a feeling for how likely we should find it that new estimates would fall outside the range of existing estimates, and how far outside this range they might fall.
We do this by generating synthetic point estimates for N by randomly sampling each parameter from the set of estimates for that parameter, and then multiplying these together. Doing this many times produces the following picture of the 'collective' view of the research community's uncertainty about N , shown in Fig. 1 .
Of the raw literature estimates for N , 64 % have N > 100. As we saw in the toy model, such values of N correspond to probabilities of less than 3.7 × 10 -44 that we are alone in our galaxy. So if we took any of those estimates at face value, we would face a serious discrepancy with our observations and thus a Fermi paradox.
However, adjusting for the implicit uncertainty in the literature changes this story dramatically. While most of the synthetic estimates of N are above 1 and the peak of the distribution is on the optimistic side (mean 53 million, median 100), there exists a pessimistic tail due to the existence of some very low parameter estimates. This tail is extremely broad, spanning more than 30 orders of magnitude.
Given this synthetic distribution for the community's uncertainty, the total credence for N  1 when taking non-terrestrial environments like icy moons into account. Hence it can be argued that LU[n e ] > 12, although the post-2000 literature estimates only covers 6 orders of magnitude. Much of the disagreement is about what requirements go into the n e term and which ones go into the f l term. For our purposes we will take an earth-like planet to be be little more than a rocky planet in a habitable zone and thus assume that LU[n e ] ≈ 2.
f l and f i are highly uncertain, and will be examined in the next section. Similarly there are no clear arguments for the range of uncertainty of f c : the range of estimates in the literature from 10 -2 to 1 give LU[f c ] = 2, but it is clear a broader range is intended.
The final L factor ranges between 50 50 %.
While it is rarely considered in the literature, if intergalactic travel is possible, this could also greatly increase the effective detection range and the bound.
References
[1]Jones EricM. Where is everybody? an account of fermi's question.  1985;:.
[2]Drake Frank, Vakoch DouglasA, Dowd MatthewF. The Drake Equation: Estimating the Prevalence of Extraterrestrial Life through the Ages.  2015;8:.
[3]Achenbach J. Life beyond earth. National Geographic 2000;197:.
[4]Steven J, Dick , Seti . History of Astronomy: An Encyclopedia, chapter SETI.  1997;:.
[5]Maccone Claudio. Seti and seh (statistical equation for habitables). Acta Astronautica 2011;68:63--75.
[6]Glade Nicolas, Ballet Pascal, Bastien Olivier. A stochastic process approach of the drake equation parameters. International Journal of Astrobiology 2012;11:103--108.
[7]Duncan H Forgan . A numerical testbed for hypotheses of extraterrestrial life and intelligence. International Journal of Astrobiology 2009;8:121--131.
[8]David S, Spiegel EdwinL, Turner . Bayesian analysis of the astrobiological implications of lifes early emergence on earth. Proceedings of the National Academy of Sciences 2012;109:395--400.
[9]Prantzos Nikos. A joint analysis of the drake equation and the fermi paradox.  None;:.
[10]Carter Brandon, Mccrea WilliamH. The anthropic principle and its implications for biological evolution [and discussion]. Philosophical Transactions of the Royal Society of London A: Mathematical, Physical and Engineering Sciences None;310:347--363.
[11]Lambert Jean-François. Adsorption and polymerization of amino acids on mineral surfaces: a review. Origins of Life and Evolution of Biospheres 2008;38:211--242.
[12]Bruce Martin. Free energies and equilibria of peptide bond hydrolysis and formation. Biopolymers 1998;45:351--353.
[13]Luigi Pier,  Luisi. Chemistry constraints on the origin of life. Israel Journal of Chemistry 2015;55:906--918.
[14]Levinthal Cyrus. Are there pathways for protein folding. J. Chim. phys 1968;65:44--45.
[15]Zwanzig Robert, Szabo Attila, Bagchi Biman. Levinthal's paradox. Proceedings of the National Academy of Sciences 1992;89:20--22.
[16]Harold S, Bernhardt . The rna world hypothesis: the worst theory of the early evolution of life (except for all the others) a. Biology direct 2012;7:.
[17]Aaron E, Engelhart NicholasV, Hud . Primitive genetic polymers. Cold Spring Harbor perspectives in biology 2010;2:.
[18]Karri Phaneendrasai, Punna Venkateshwarlu, Kim Keunsoo, Krishnamurthy Ramanarayanan. Base-pairing properties of a structural isomer of glycerol nucleic acid. Angewandte Chemie 2013;125:5952--5956.
[19]Vitor B, Pinheiro Philipp, Holliger . The xna world: progress towards replication and evolution of synthetic genetic polymers. Current opinion in chemical biology 2012;16:245--252.
[20]Francis HC, Crick . The genetic codeyesterday, today, and tomorrow. Cold Spring Harbor symposia on quantitative biology 1966;31:3--9.
[21]Hohsaka Takahiro, Sisido Masahiko. Incorporation of non-natural amino acids into proteins. Current opinion in chemical biology 2002;6:809--815.
[22]Pavel V Baranov Maxime, Venin Gregory, Provan . Codon size reduction as the origin of the triplet genetic code. PLoS One 2009;4:.
[23]. Eavesdropping on galactic civilizations. Science 1978;:.
[24]Billingham John, Tarter Jill. Detection of the earth with the seti microwave observing system assumed to be operating out in the galaxy. Acta astronautica 1992;26:185--188.
[25]Chela-Flores Julian, Lemarchand GuillermoA, Oró John. Astrobiology: Origins from the Big-Bang to Civilisation Proceedings of the Iberoamerican School of Astrobiology Caracas.  1999;:.
[26]Tarter Jill. The search for extraterrestrial intelligence (seti). Annual Review of Astronomy and Astrophysics 2001;39:511--548.
[27]James M Cordes T, Joseph W Lazio Carl, Sagan . Scintillation-induced intermittency in seti. The Astrophysical Journal 1997;487:.
[28]Roger L Griffith JasonT, Wright Jessica, Maldonado MatthewS, Povich Steinn, Sigurdsson Brendan, Mullan . The ĝ infrared search for extraterrestrial civilizations with large energy supplies. iii. the reddest extended sources in wise. The Astrophysical Journal Supplement Series 2015;217:.
[29]Jones EricM. Colonization of the galaxy. Icarus 1976;28:421--422.
[30]William I, Newman Carl, Sagan . Galactic civilizations: Population dynamics and interstellar diffusion. Icarus 1981;46:293--327.
[31]Jones EricM. Discrete calculations of interstellar migration and settlement. Icarus 1981;46:328--336.
[32]Fogg MartynJ. Temporal aspects of the interaction among the first galactic civilizations: The interdict hypothesis. Icarus 1987;69:370--384.
[33]Wright B, Mullan S, Sigurdsson , Povich . The ĝ infrared search for extraterrestrial civilizations with large energy supplies. i. background and justification. The Astrophysical Journal 2014;792:.
[34]Tegmark Max. Our mathematical universe: my quest for the ultimate nature of reality.  2014;:.
[35]Lacki BC. The Log Log Prior for the Frequency of Extraterrestrial Intelligences.  2016;:.
Dissolving the Fermi Paradox
https://arxiv.org/abs/1806.02404