A stochastic process approach of the drake equation parameters

Glade, Nicolas; Ballet, Pascal; Bastien, Olivier

doi:10.1017/s1473550411000413

Cited by 53 publications

(34 citation statements)

References 28 publications

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“…There is nothing inherently special about where we live and thus a civilization emerging a few hundred light years should not have any particular reason to live longer or shorter than ourselves. Extending further afield, where effects such as galactic chemical gradients (Gonzalez et al 2001), supernovae rates (Lineweaver et al 2004), active galactic nuclei (Balbi and Tombesi 2018;Lingam et al 2019), stellar encounter rates (McTier et al 2020) may vary, would indeed require formally building a model which described this covariance. Accordingly, the results of our work should be understood to be formally only applicable to cases where L is not expected to be intrinsically linked to location, such as our local stellar neighbourhood.…”

Section: A Note On Distancementioning

confidence: 99%

Contact inequality: first contact will likely be with an older civilization

Kipping

Frank

Scharf

2020

International Journal of Astrobiology

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First contact with another civilization, or simply another intelligence of some kind, will likely be quite different depending on whether that intelligence is more or less advanced than ourselves. If we assume that the lifetime distribution of intelligences follows an approximately exponential distribution, one might naively assume that the pile-up of short-lived entities dominates any detection or contact scenario. However, it is argued here that the probability of contact is proportional to the age of said intelligence (or possibly stronger), which introduces a selection effect. We demonstrate that detected intelligences will have a mean age twice that of the underlying (detected + undetected) population, using the exponential model. We find that our first contact will most likely be with an older intelligence, provided that the maximum allowed mean lifetime of the intelligence population, τmax, is ≥ e times larger than our own. Older intelligences may be rare but they disproportionately contribute to first contacts, introducing what we call a ‘contact inequality’, analogous to wealth inequality. This reasoning formalizes intuitional arguments and highlights that first contact would likely be one-sided, with ramifications for how we approach SETI.

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Section: A Note On Distancementioning

confidence: 99%

Contact inequality: first contact will likely be with an older civilization

Kipping

Frank

Scharf

2020

International Journal of Astrobiology

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“…However, the equation does not take account of the evolution of the physical properties of the Milky Way. The factors of the equation do not have a temporal dependence (Ć irković, 2004) or deal with the inherent parameter uncertainties through the application of probability distributions (Maccone, 2010;Glade et al, 2012). In terms of temporal considerations and the prioritization of spatial search regions, the Drake equation can, therefore, provide little guidance to SETI.…”

Section: Introductionmentioning

confidence: 99%

Extending Galactic Habitable Zone Modeling to Include the Emergence of Intelligent Life

Morrison

Gowanlock

2015

Astrobiology

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Previous studies of the galactic habitable zone have been concerned with identifying those regions of the Galaxy that may favor the emergence of complex life. A planet is deemed habitable if it meets a set of assumed criteria for supporting the emergence of such complex life. In this work, we extend the assessment of habitability to consider the potential for life to further evolve to the point of intelligence--termed the propensity for the emergence of intelligent life, φI. We assume φI is strongly influenced by the time durations available for evolutionary processes to proceed undisturbed by the sterilizing effects of nearby supernovae. The times between supernova events provide windows of opportunity for the evolution of intelligence. We developed a model that allows us to analyze these window times to generate a metric for φI, and we examine here the spatial and temporal variation of this metric. Even under the assumption that long time durations are required between sterilizations to allow for the emergence of intelligence, our model suggests that the inner Galaxy provides the greatest number of opportunities for intelligence to arise. This is due to the substantially higher number density of habitable planets in this region, which outweighs the effects of a higher supernova rate in the region. Our model also shows that φI is increasing with time. Intelligent life emerged at approximately the present time at Earth's galactocentric radius, but a similar level of evolutionary opportunity was available in the inner Galaxy more than 2 Gyr ago. Our findings suggest that the inner Galaxy should logically be a prime target region for searches for extraterrestrial intelligence and that any civilizations that may have emerged there are potentially much older than our own.

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“…Notice that in the simplified picture presented here, it is assumed that all civilizations have similar values of L, that is, the dispersion ∆L is ∆L ≤ L. This need not be the case. Statistical treatments, considering ∆L ∼ L, and canonical distributions have been studied (Maccone 2010;Glade et al 2012). However, in any case, the unknown mean value of L plays a more important role than the equally unknown form of its distribution.…”

Section: A Fresh Look At Drake's Formulamentioning

confidence: 99%

A probabilistic analysis of the Fermi paradox in terms of the Drake formula: the role of the L factor

Prantzos

2020

Monthly Notices of the Royal Astronomical Society

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In evaluating the number of technological civilizations N in the Galaxy through the Drake formula, emphasis is mostly put on the astrophysical and biotechnological factors describing the emergence of a civilization and much less on its the lifetime, which is intimately related to its demise. It is argued here that this factor is in fact the most important regarding the practical implications of the Drake formula, because it determines the maximal extent of the "sphere of influence" of any technological civilization. The Fermi paradox is studied in the terms of a simplified version of the Drake formula, through Monte Carlo simulations of N civilizations expanding in the Galaxy during their space faring lifetime L. In the framework of that scheme, the probability of "direct contact" is determined as the fraction of the Galactic volume occupied collectively by the "spheres of influence" of N civilizations. The results of the analysis are used to determine regions in the parameter space where the Fermi paradox holds. It is argued that in a large region of the diagram the corresponding parameters suggest rather a "weak" Fermi paradox. Future research may reveal whether a "strong" paradox holds in some part of the parameter space. Finally, it is argued that the value of N is not bound by N=1 from below, contrary to what is usually assumed, but it may have a statistical interpretation.

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A stochastic process approach of the drake equation parameters

Cited by 53 publications

References 28 publications

Contact inequality: first contact will likely be with an older civilization

Contact inequality: first contact will likely be with an older civilization

Extending Galactic Habitable Zone Modeling to Include the Emergence of Intelligent Life

A probabilistic analysis of the Fermi paradox in terms of the Drake formula: the role of the L factor

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