Related papers: A biotic cosmos demystified?
We model the settlement of the galaxy by space-faring civilizations in order to address issues related to the Fermi Paradox. We explore the problem in a way that avoids assumptions about the intent and motivation of any exo-civilization…
In this paper, we analyze a new possible biological surface feature for habitable worlds orbiting other stars: biofluorescence. High ultraviolet (UV) and blue radiation fluxes drive the strongest biofluorescence in terrestrial fluorescent…
We investigate the dependence of elemental abundances on physical constants, and the implications this has for the distribution of complex life for various proposed habitability criteria. We consider three main sources of abundance…
Planets like the Earth cannot form unless elements heavier than helium are available. These heavy elements, or `metals', were not produced in the big bang. They result from fusion inside stars and have been gradually building up over the…
The stability of Earth's climate on geological timescales is enabled by the carbon-silicate cycle that acts as a negative feedback mechanism stabilizing surface temperatures via the intake and outgas of atmospheric carbon. On Earth, this…
A massive particle decaying into neutrinos in the early Universe is known to be less constrained than if it was decaying into other standard model particles. However, even if the decay proceeds into neutrinos, the latter still inevitably…
To be habitable, a world (planet or moon) does not need to be located in the stellar habitable zone (HZ), and worlds in the HZ are not necessarily habitable. Here, we illustrate how tidal heating can render terrestrial or icy worlds…
Current observations of the fraction of dark energy and a lower limit on its tension, coupled with an assumption of the non-convexity of the dark energy potential, are used to derive a lower limit of 26 billion years for the future age of…
The Kepler data show that habitable small planets orbiting Red Dwarf stars (RDs) are abundant, and hence might be promising targets to look at for biomarkers and life. Planets orbiting within the Habitable Zone of RDs are close enough to be…
This study examines the hypothesis that the rapid development of Artificial Intelligence (AI), culminating in the emergence of Artificial Superintelligence (ASI), could act as a "Great Filter" that is responsible for the scarcity of…
Water is crucial for the emergence and evolution of life on Earth. Recent studies of the water content in early forming planetary systems similar to our own show that water is an abundant and ubiquitous molecule, initially synthesized on…
Recently, many Earth-sized planets have been discovered around stars other than the Sun that might possess appropriate conditions for life. The development of theoretical methods for assessing the putative habitability of these worlds is of…
The universe is found to have undergone several phases in which the gravitational constant had different behaviors. During some epochs the energy density of the universe remained constant and the universe remained static. In the radiation…
It is usually assumed that relic neutrinos possess a Fermi-Dirac distribution, acquired during thermal equilibrium in the Early Universe. However, various mechanisms could introduce strong distortions in this distribution. We perform a…
The Gaia hypothesis postulates that life regulates its environment to be favorable for its own survival. Most planets experience numerous perturbations throughout their lifetimes such as asteroid impacts, volcanism, and the evolution of…
It is generally argued that the present cosmological observations support the accelerating models of the universe, as driven by the cosmological constant or `dark energy'. We argue here that an alternative model of the universe is possible…
We consider some consequences of the presence of a cosmological lepton asymmetry in the form of neutrinos. A relic neutrino degeneracy enhances the contribution of massive neutrinos to the present energy density of the Universe, and…
A hard difficulty in Astrobiology is the precise definition of what life is. All living beings have a cellular structure, so it is not possible to have a broader concept of life hence the search for extraterrestrial life is restricted to…
ecent observations of type Ia supernovae indicate that the Universe is in an accelerating phase of expansion. The fundamental quest in theoretical cosmology is to identify the origin of this phenomenon. In principle there are two…
Ongoing and future space missions aim to identify potentially habitable planets in our Solar System and beyond. Planetary habitability is determined not only by a planet's current stellar insolation and atmospheric properties, but also by…