Related papers: Too Damned Quiet?
We propose a search for sources of directed energy systems such as those now becoming technologically feasible on Earth. Recent advances in our own abilities allow us to foresee our own capability that will radically change our ability to…
The long-term habitability of Earth-like planets requires low orbital eccentricities. A secular perturbation from a distant stellar companion is a very important mechanism in exciting planetary eccentricities, as many of the extrasolar…
The search for habitable planets, and even for ``Earth 2.0'', is a major driver in contemporary astronomy. However selecting target fields to prioritise for such searches presents a challenge. Here we establish a statistical analysis of the…
We use a probability theory framework to discuss the search for biosignatures. This perspective allows us to analyse the potential for different biosignatures to provide convincing evidence of extraterrestrial life and to formalise…
The concept of a system-wide measure of the sustainment of life (habitability) for space-faring interplanetary species is introduced and explored. Although largely agnostic to the details of how interplanetary life might operate (e.g., via…
The claim that life is an emergent phenomenon exhibiting novel properties and principles is often criticized for being in conflict with causal closure at the microscopic level. I argue that advances in cosmological theory suggesting an…
The habitable zones of low-mass stars are characterized by escape speeds that can be a few times higher than the Earth's orbit around the Sun. Owing to the exponential dependence of the required fuel mass on the terminal speed for chemical…
The coupled interior-atmosphere system of terrestrial exoplanets remains poorly understood. Exoplanets show a wide variety of sizes, densities, surface temperatures, and interior structures, with important knock-on effects for this coupled…
The oft-repeated claim that life is written into the laws of nature are examined and criticized. Arguments are given in favour of life spreading between near-neighbour planets in rocky impact ejecta (transpermia), but against panspermia,…
The habitability of the surface of any planet is determined by a complex evolution of its interior, surface, and atmosphere. The electromagnetic and particle radiation of stars drive thermal, chemical and physical alteration of planetary…
The discovery of exoplanets has both focused and expanded the search for extraterrestrial intelligence. The consideration of Earth as an exoplanet, the knowledge of the orbital parameters of individual exoplanets, and our new understanding…
No present observations suggest a technologically advanced extraterrestrial intelligence (ETI) has spread through the galaxy. However, under commonplace assumptions about galactic civilization formation and expansion, this absence of…
The Search for Extraterrestrial Intelligence (SETI) has heretofore been a largely passive exercise, reliant on the pursuit of technosignatures. Still, there are those that advocate a more active approach. Messaging Extraterrestrial…
Cosmology seems extremely remote from everyday human practice and experience. It is usually taken for granted that cosmological data cannot rationally influence our beliefs about the fate of humanity -- and possible other intelligent…
It is often presumed, that life evolves relatively fast on planets with clement conditions, at least in its basic forms, and that extended periods of habitability are subsequently needed for the evolution of higher life forms. Many planets…
The search for extraterrestrial intelligence by looking for signals from advanced technological civilizations has been ongoing for some decades. We suggest that it could possibly be made more efficient by focusing on stars from which the…
A simple stochastic model for evolution, based upon the need to pass a sequence of n critical steps (Carter 1983, Watson 2008) is applied to both terrestrial and extraterrestrial origins of life. In the former case, the time at which humans…
Current evidence suggests that the cosmological constant is not zero, or that we live in an open universe. We examine the implications for the future under these assumptions, and find that they are striking. If the Universe is cosmological…
An astrophysical model is proposed to answer Fermi's question. Gamma-ray bursts have the correct rates of occurrence and plausibly the correct energetics to have consequences for the evolution of life on a galactic scale. If one assumes…
The Search for Extraterrestrial Intelligence (SETI) has thus far failed to provide a convincing detection of intelligent life. In the wake of this null signal, many "contact pessimistic" hypotheses have been formulated, the most famous of…