https://www.sciencedirect.com/science/article/abs/pii/S0094576518314000 JavaScript is disabled on your browser. Please enable JavaScript to use all the features on this page. [1690066898] Skip to main content Skip to article Elsevier logo * Journals & Books * * Search RegisterSign in * Access through your institution * Purchase PDF Search ScienceDirect[ ] Article preview * Abstract * Introduction * Section snippets * References (102) * Cited by (9) * Recommended articles (6) Elsevier Acta Astronautica Volume 155, February 2019, Pages 118-130 Acta Astronautica Using predictive Bayesian Monte Carlo- Markov Chain methods to provide a probablistic solution for the Drake equation Author links open overlay panelFrederick Bloetscher Show more Share Cite https://doi.org/10.1016/j.actaastro.2018.11.033Get rights and content Abstract Are we alone in the universe? It is an age-old question that continues to encourage interest and controversy among the public as well as academics. Development of explanations for life elsewhere ranges widely, but few mathematical models have been developed to measure the likelihood of concurrent, intelligent life, and those that exist are widely speculative due to the lack of information. However, with the addition of information from Kepler explorations for new solar systems within our galaxy, and calculation of the potential number of stars in the expanse of the universe, data for a useful probabilistic model to determine the likelihood of life beyond Earth may be possible with the use of predictive Bayesian statistics. Predictive Bayesian statistical methods are designed to use limited, uncertain data, to develop results. The result provides a probability curve of the likelihood of life in the universe that includes both uncertainty and potential variability within the result to provide a means to define the probability of life in the galaxy as well as life within proximity to earth. That said, the results indicate that the probability we are alone (<1) in the galaxy is significant, while the maximum number of contemporary civilizations might be as few as a thousand. With so few concurrent civilizations, and such large distances, it is little surprise that the SETI project has not found that alien signal. Our nearest neighbor is 4 light years away, and there are under 100 stars within 50 light years, the total of the project's existence. Introduction July 14-15, 2015 was the closest fly-by of the New Horizons probe to former "planet" Pluto and its moon Charon, completing its 10 year journey to explore the surface of these two bodies. This is the last planetary object in the solar system that the United States had not visited, and it will be the last new planetary body surface that will be seen during the lifetimes of those currently alive as a result of the extensive distances and therefore time required to reach other worlds. The moment created an opportunity to assess what we know about that age-old question, "are we alone?" A number of people have suggested answers to this question (see Table 1). St Albertus Magnus asked whether "there exist many worlds, or is there but a single world. This is one of the most noble and exalted questions in the study of Nature?" [1]. Aristotle [2] and Plato [3] suggested that life would not exist elsewhere. St. Thomas Aquinas argued against the plurality of worlds, as do many fundamentalist religions today, while Epicurus (341-270 BC) suggested that there are infinite worlds both like and unlike this world of ours. Hart [4] suggested that we will not find life because the distance cannot be overcome. Cox [5] argued that the time restrictions may not permit any extraterrestrials to reach us. Circovic and Bradbury [6] suggested that the failure of SETI to detect alien life so far may be related to the strategies employed, which is eerily similar to the suggestion 7 years later by Shostak [7] that if we detect alien life we may have no way to understand that we have done so. Forgan [8] notes that the solution of the Fermi paradox is they are here, but hiding, contact with us is forbidden, they were here, but now are gone, or they are coming. Over the years, numerous researchers attempted to explore this questions including Annis [9], Brin [10], Circovic [11], Crawford [12], Freeman and Lampton [13], Gowdy [14], Keyes [15], Kinouchi [16], Landis [17], Papagiannis [18], Scheffer [19], Schostak [20], Smart [21], Soter [22], Tipler [23] and Wesson [24]. The question that this paper attempts to respond to is Fermi's question "if we are not alone, where is everyone?" [25], by identifying a means to estimate the likely number of civilizations in the galaxy. Our arrival on the moon on July 20, 1969 did not provide an answer. Nor did any of the Voyager expeditions, the Mars rovers, the Hubble telescope, SETI or any number of space flights after 1970. Exploring Pluto was just the latest visit to a site in our solar system, but so far, no luck with life. However, since 1990, over 700 confirmed and 3500 suspected planets have been found circling other stars. But planets, do not translate to finding life, even when they are earthlike [41]. Since 1959, SETI has yet to find an alien signal. The question is then two fold - what is the probability of there being life in the galaxy, and why haven't we received a response to our transmissions? As will be shown, these two questions are related. Unanswered is whether we will recognize a signal if one is received. In 1959, a US astronomer, Frank D. Drake, a NASA employee who carried out the first SETI radio telescope experiments, outlined an equation for finding communicable civilizations [42,43]:N = RLwhere N is the number of galactic communities at or beyond out level of technical capability and able to communicate with us, R is the rate of appearance of such communities and L is the longevity of same [[42], [43], [44]]. Since that time a variety of people have used Drake's initial equation to develop factors of importance in creating a model that can assign numerical values on the parameters of Drake's equation. Bracewell [33] suggested that this simple equation be modified to:N = Sum(R[j] L[j]) To incorporate variability in the types of civilizations that could communicate at any given time and suggested that proximity is random [33]. Jones [44] noted that more recent iterations of Drake's original equation include 6 parameters that would be of interest in determining the number of communicable civilizations in the Milky Way galaxy today [45]:N = R f[p] n[e] f[i] f[t] f[c] Lwhere N is the number of communicable civilizations, R is the rate which stars are born in the galaxy, f[p] is the fraction of stars with planetary systems, n[e] is the number of planets that might hold life, f[t] is the fraction of planets with life, f[i] is the fraction of planets with life that have evolved, f[c] is the number of civilizations of evolved civilizations with the ability to communicate, and L is the length of time over which the communication is possible. An additional factor named C is a recent suggestion for colonization [46]. This author suggests that the factor n[e] is actually comprised of four factors: planet size, presence of a moon, location within the Goldilocks zone and the correct star type. None of these factors is fully known and so while the known unknowns that exist within the universe make it difficult to analyze the probability of life elsewhere, there may be unknown unknowns we have yet to contemplate. As a result, statistical methods that can employ both uncertainty and variability in opinion would seem appropriate for used in providing a probabilistic answer to Drake's equation. Section snippets Methodology There are statistical methods that are useful in dealing with uncertain or incomplete information. Kreifeldt [30] and Maccone [39,40] suggested that distributions could be applied to the variables in the Drake equation. Maccone [39,40] proposed such solutions related to a log-normal distribution, but the results do not permit adjustments based on new information without reconstructing the statistical parameters - basically starting the analysis over with the new data. Determining the relevant R - rate of star formation in the galaxy The first parameter of the equation involves the rate of star formation in the galaxy. The rate of star formation adds the time element that is important is finding contemporary civilizations. While there are billions of stars, they have evolved over 13 billion years so many may not be at the same stage of evolution. Jones [44] estimated that this number is 10 per year. This assumed the galaxy is increasing in star population. Other disagree with that point given the black hole in the center of Results and discussion No specific answer on the likelihood of intelligent life on another planet communicating with Earth is possible despite attempts to create models that provide such answers. However, using predictive Bayesian methods, a probability distribution can be created to accomplish same. This approach involves the assignment of probability distributions to the underlying factors. When little or no data are available to specify the parameters of these distributions, probability distributions can then be Conclusions Despite major progress in the detection of other planets in the galaxy, humans have only scratched the surface of space exploration. The answer to the famous Fermi-paradox ("Where is everybody?") is also missing because the distances across the galaxy are large and the factors that may be present are largely still uncertain [101,102]. There is emerging data that can be useful in a probabilistic model to determine the likelihood of life beyond Earth using Predictive Bayesian statistics, which Dr. Frederick Bloetscher is a Professor and Associate Dean at Florida Atlantic University in Boca Raton, FL. He received his Ph.D. from the University of Miami, Master's degree from the University of North Carolina at Chapel Hill and his BS from the University of Cincinnati. His work includes the use of statistical methods for evaluating problems with limited data. References (102) * M.M. Cirkovic et al. Galactic gradients, post-biological evolution and the apparent failure of SETI N. Astron. (2006) * J.G. Kreifeldt A formulation for the number of communicative civilizations in the galaxy Icarus (1971) * B.M. Oliver Proximity of galactic civilizations Icarus (1975) * R.N. Bracewell An extended Drake's equation, the longevity separation relation, equilibrium, inhomogeneities and chain formation Acta Astronaut. (1979) * C. Maccone SETI and SEH (statistical equation for habitables) Acta Astronaut. (2011) * C. Maccone The statistical drake equation Acta Astronaut. (2010) * F. Drake The radio search for intelligent extraterrestrial life * C. Walters et al. Interstellar colonization: a new parameter for the drake equation Icarus (1980) * Z.-N. Wu et al. Scaling relations on log normal type growth process with an extremal principle of entropy Entropy (2017) * W.A. Fowler et al. Nuclear cosmo-chronology Ann. Phys. (1960) D.A. Russell Exponential evolution: implications for intelligent extraterrestrial life Adv. Space Res (1983) S. Seager The search for extrasolar earth-like planets Earth Planet Sci. Lett. (2003) M.H. Hart Habitable zones around main sequence starts Icarus (1979) J.F. Kasting et al. Habitable zones around Main sequence stars Icarus (1993) K. Kobayashi et al. Formation of bioorganic compounds in simulated planetary atmospheres by high energy particles or photons Adv. Space Res. (2001) S.J. Dick The post-biological universe and our future in space Futures (2009) D.W. Schwartzman Absence of extraterrestrials on earth and the prospects for SETI Icarus (1977) E.M. Jones Colonization of the Galaxy Icarus (1976) G. McColley Ann. Sci. (1936) Aristotle, nd. De Caelo, v1: p... Plato, nd. Time, v... M.H. Hart An explanation for the absence of extraterrestrials on earth Q. J. Roy. Astron. Soc. (1975) L.J. Cox An explanation for the absence of extraterrestrials on earth - correspondence Q. J. Roy. Astron. Soc. (1976) S. Shostak What Happens when we detect alien life? Astronomy (2012) D.H. Forgan A numerical test bed for hypotheses of extraterrestrial life and intelligence International Journal of Astrobioology (2009) J. Annis An astrophysical explanation for the great silence Glen David Brin The 'great silence': the controversy concerning extraterrestial intelligent life Q. J. Roy. Astron. Soc. (1983) M.M. Cirkovic The temporal aspect of the drake equation and SETI Astrobiology (2004) I.A. Crawford Where Are They? Maybe We Are Alone in the Galaxy after All (2000) J. Freeman et al. Interstellar archeology and the prevalance of intelligence Icarus (1976) Robert H. Gowdy SETI: Search for ExtraTerrestrial Intelligence. The Interstellar Distance Problem (2008) B. Keyes SETI: The Drake Equation (2000) O. Kinouchi Persistence Solves Fermi Paradox But Challenges SETI Projects (2009) G. Landis The Fermi paradox: an approach based on percolation theory J. Br. Interplanet. Soc. (JBIS) (1998) M.D. Papagiannis Are we all alone, or could they be in the asteroid belt? Q. J. Roy. Astron. Soc. (1978) L.K. Scheffer Machine intelligence, the cost of interstellar travel and fermi's paradox Q. J. Roy. Astron. Soc. (1994) S. Shostak Our galaxy should Be teeming with civilizations, but where are they?. Space.com J. Smart Answering the Fermi paradox: exploring the mechanisms of universal transcension J. Evol. Technol. (June 2002) S. Soter SETI and the cosmic quarantine hypothesis. Astrobiology magazine. Space.com F.J. Tipler A brief history of the extraterrestrial intelligence concept Q. J. RAS (1981) P. Wesson Cosmology, extraterrestrial intelligence, and a resolution of the Fermi-Hart paradox. Royal Astronomical Society Quarterly Journal (1990) E.M. Jones Where Is Everybody? an Account of Fermi's Question, Los Alamos Technical Report LA-10311-MS, March, 1985 (1985) C. Sagan Direct contact among galactic civilizations by relativistic interstellar space flight Planetary Space Sci v (1962) S. von Hoerner S. von Hoerner The search for signals from other civilizations Science (1961) I.S. Shklovskii et al. Distribution of technical civilizations in the galaxy C. Sagan S.G. Wallenhorst The drake equation Re-examined Q. J. Roy. Astron. Soc. (1981) F. Drake et al. Is Anyone Out There? (1991) L. Klaes SETI the drake equation (sagan: a carl sagan WebSite) View more references Cited by (9) * Monte Carlo estimation of the probability of causal contacts between communicating civilizations 2020, International Journal of Astrobiology * Artificial versus biological intelligence in the Cosmos: clues from a stochastic analysis of the Drake equation 2020, International Journal of Astrobiology * Technosignatures: Frameworks for Their Assessment 2023, Astrophysical Journal * The Number of Possible CETIs within Our Galaxy and the Communication Probability among These CETIs 2022, arXiv * The Number of Possible CETIs within Our Galaxy and the Communication Probability among These CETIs 2022, Astrophysical Journal * Estimating survival probability using the terrestrial extinction history for the search for extraterrestrial life 2020, Scientific Reports View all citing articles on Scopus Recommended articles (6) * Research article Effects of total pressure on mode transition in a dual-mode combustor Acta Astronautica, Volume 155, 2019, pp. 55-62 Show abstract The mode transition experiments of the dual-mode combustor were carried out under the conditions that the total pressure was 600 kPa, 700 kPa, 800 kPa and 900 kPa, the total temperature was 810 K, and the Mach number was 2.0. According to the wall pressure of the combustor measured in the experiment, the distribution of other airflow parameters of the combustor were obtained through the one-dimensional performance calculation method. The processes of mode transition of the combustor under different total pressures were studied. The study show that the dimensionless peak pressure of the combustor increased with the increase of the entrance total pressure under the same fuel equivalence ratio; the larger the total pressure, the smaller the fuel equivalence ratio required to reach the same dimensionless peak pressure. The results show that there were pure scramjet mode, dual-mode scramjet mode, dual-mode ramjet mode and the combustion state that the pressure disturbance had spread to the entrance of the isolator with the increase of the fuel equivalence ratio. The dimensionless peak pressures of the combustor when mode transition occurred were 0.25, 0.41, and 0.5, and did not change with the change of the total pressure of the incoming flow. * Research article Seismic investigation of icy crust covering subsurface oceans of Europa and Ganymede: Preliminary assessment of hypothetical experiment using impactor Acta Astronautica, Volume 155, 2019, pp. 170-178 Show abstract Jupiter's satellite Europa is believed to harbor a global ocean beneath its ice-covered surface. But the thickness of this ice, despite its significance to the habitability of this moon, is unknown: estimates range from as thin as hundreds of meters to as thick as tens of kilometers. In this paper, we investigate the feasibility of a hypothetical experiment in which the ice's thickness is measured via seismic analysis. The assumed scenario calls for a seismometer to be placed on the satellite's surface to detect the ice surface's seismic response induced by an artificial impact event. Our hypothetical experiment could be applied at Europa as well as at Ganymede. For both satellites, two impact scenarios are considered: a low-energy-impact case, in which an orbiter probe impacts the ice at the end of the mission, and a high-energy-impact case, in which a spent upper rocket stage impacts the ice upon Jupiter arrival. We find that an impactor-induced seismic investigation is a promising add-on experiment in future missions to the icy moons of Jupiter. * Research article Space collision probability computation based on on-board optical cues Acta Astronautica, Volume 155, 2019, pp. 33-44 Show abstract This paper presents a novel on-board space collision analysis method for space situational awareness. The framework is developed under the following assumptions: 1) A satellite can be equipped with on-board sensors for space object recognition. 2) No a-priori knowledge of the space objects is provided. A space object size and relative state estimation method is firstly proposed, wherein optical cues acquired from onboard sensors are utilized to achieve the estimation. Then, the unscented transform approach is employed to calculate the probability density function (PDF) of collision probability based on the estimate information. Monte Carlo simulations and an experimental test demonstrate that the proposed approach can achieve high-precision on-board collision probability estimation with an error less than 3%. * Research article Study on electrons conduction paths in Hall thruster ignition processes with the cathode located inside and outside the magnetic separatrix Acta Astronautica, Volume 155, 2019, pp. 153-159 Show abstract A high speed charged coupled device (CCD) camera was used to examine the plume features over time when the cathode was located inside and outside the magnetic separatrix. Due to the different positions of the cathode, there are obvious differences in the electron impact excitation process, the characteristics of the plasma bridge, and the transition process from the end of ignition to the steady-state discharge process. The main reason for these differences may be due to the different conduction paths followed by emitted electrons into the acceleration channel. The CCD images method can be used as a technique to characterize the ignition process of Hall thruster. * Research article Power system analysis and optimization of a modular experiment Carrier during an analog lunar demo mission on a volcanic environment Acta Astronautica, Volume 155, 2019, pp. 200-210 Show abstract The ROBEX (Robotic Exploration of Extreme Environments) alliance, as formed by the German Helmholtz association, aims to explore synergies and bring together technological challenges and scientific questions between two, up to now unrelated, fields: space and deep sea. The final goal of the alliance targets field tests for available and newly developed instrumentation for the deep sea and on a terrestrial lunar analogue. In this regard, two different test campaigns were conducted, one in the area of Svalbard, Norway and one on mount Etna in Sicily, Italy. The volcano environment served as a lunar analogue, enabling seismic scientific experiments and testing of robotic mobility algorithms. The complete field mission infrastructure consists of a stationary lander, a mobile element and instrument carriers. The modular instrument carrier, commonly referred as Remote Unit (RU), was developed accounting for two different mass requirements: 3 kg (RU3) and 10 kg (RU10). While developed in the frame of ROBEX resumes the idea of a lightweight instrument carrier as developed for the MASCOT (Mobile Asteroid surface scout) mission. The RU houses the instrument, shelters it and provides all essential support functions such as rudimentary thermal control (via foil covering), power provision, data acquisition and handling and data transmission to the control centre. This paper presents theoretical and experimental results of the RU3 power subsystem analysis during the mount Etna field campaign. Drawing upon this analysis, necessary adjustments and revisions to further develop the system towards a more power efficient structure for terrestrial and extraterrestrial usage can be concluded. * Research article Special issue on Space Situational Awareness from the 1^st International Academy of Astronautics Conference on Space Situational Awareness or ICSSA 2017 Acta Astronautica, Volume 155, 2019, pp. 367-368 [1-s2] Dr. Frederick Bloetscher is a Professor and Associate Dean at Florida Atlantic University in Boca Raton, FL. He received his Ph.D. from the University of Miami, Master's degree from the University of North Carolina at Chapel Hill and his BS from the University of Cincinnati. His work includes the use of statistical methods for evaluating problems with limited data. View full text (c) 2018 IAA. Published by Elsevier Ltd. All rights reserved. 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