astro-ph.CO Archives

[LEFT] Best value of the minimum probability for each cosmology scenario-habitability condition pair mentioned in the text. For each element in this chart, the minimum probability of the best combination of habitability conditions of all those which include the one mentioned is displayed. The top row includes combinations of up to 8 habitability conditions; the rest are capped at 5.[RIGHT] Same - but comparing against origin of life scenarios. -- astro-ph.CO

Astrochemistry, Atmospheres, Climate, Weather, Biochemistry & Organic Chemistry, Biogeochemical Cycles & Geobiology, Biophysics, Biosignatures & Paleobiology, Habitable Zones, Status Report

Multiverse Predictions for Habitability: Fundamental Physics and Galactic Habitability

by Keith CowingSeptember 15, 2025September 14, 2025

In the multiverse hypothesis, a range of universes exist with differing values of our physical constants.

A comparison of state-of-the-art geometric distances that serve to anchor the distance scale and their current relative uncertainties. Additional candidate (≲1 Mpc) eclipsing binary hosts to target in future are also pictured. Current EB distances to M31 and M33 rely on early-type stars and are not precise enough to be included in H0 determination (Vilardell et al. 2010; Bonanos et al. 2006), but we expect this will improve with more sensitive moderate- to high-resolution spectroscopy capable of characterizing late-type EB systems. -- astro-ph.CO

Astronomy & Telescopes, Biosignatures & Paleobiology, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Interstellar, Status Report, Stellar Cartography

Envisioning The Distance Ladder In The Era Of The Habitable Worlds Observatory

by Keith CowingJuly 5, 2025

The current state-of-the-art cosmic distance ladder requires three rungs–geometric distances, primary indicators, and Type Ia Supernovae–to achieve a 1% measurement of the Hubble constant H0.

Oops a primordial black hole just wen through me. Grok via astrobiology.com

Astronomy & Telescopes, Space Physiology & Medicine, Status Report

Gravitational Effects of a Small Primordial Black Hole Passing Through the Human Body

by Keith CowingFebruary 18, 2025February 18, 2025

The gravitational effects of a primordial black hole (PBH) passing through the human body are examined, with the goal of determining the minimum mass necessary to produce significant injury or […]

Gaia - Planetary Perspectives, Habitable Zones, Intelligence & Language, Origin & Evolution of Life, Panspermia, SETI & Technosignatures, Status Report

Percolation Of ‘Civilisation’ In A Homogeneous Isotropic Universe

by Keith CowingDecember 29, 2024December 29, 2024

In this work, we consider the spread of a ‘civilisation’ in an idealised homogeneous isotropic universe where all the planets of interest are habitable.

Upper panels: Cosmic star formation rate density, as computed with our extension of the SP21 model (dashed black line) and as given by the original SP21 model (dot-dashed red line). In the left panel, we further show with the empirical fit (dotted black line) to a compilation of observational data provided by Madau & Dickinson (2014) (grey data points). The right panel shows the behaviour of the SP21 model and our extended formalism in the future of the universe. As future times correspond to negative redshifts, and the cosmic star formation rate density becomes asymptotically null at arbitrarily large times, both axes switch from logarithmic to linear scale when moving from the left to the right panel. The grey hatched shaded area in the right panel excludes the non-physical region corresponding to 𝜌¤∗ < 0. Lower panels: Relative difference between the two models showed above (dashed black line), and between our formalism and the fit from Madau & Dickinson (2014) (dotted black line). The latter comparison is available only for positive redshifts (i.e., past cosmic times), as the fit represents a purely empirical fit to the data, and not a predictive theoretical model. The SP21 model agrees well with the improved method introduced in this work at high redshift, but overestimates the cosmic star formation rate density at lower redshift and in the future. In the redshift range 0 < 𝑧 < 10, both the original SP21 model and our updated formalism agree with the empirical fit within a factor of ∼ 2. -- astro-ph.CO

Astronomy & Telescopes, Status Report, Stellar Cartography

The Impact Of The Cosmological Constant On Past And Future Star Formation

by Keith CowingNovember 23, 2024November 23, 2024

We present an extended analytic model for cosmic star formation, with the aim of investigating the impact of cosmological parameters on the star formation history within the ΛCDM paradigm.

Microlensing magnification, in magnitudes, as a function of the source position for the positive parity image A. The right column assumes that all mass is in stellar-mass objects while the left includes a contribution from planetary-mass (nano-) lenses. The top row is for a point (or, more precisely, pixel-sized) source while the maps in the middle are convolved with a Gaussian disc of half-light radius 𝑅𝑠 = 3 × 1015 cm.-- astro-ph.CO

Astronomy & Telescopes, Exoplanets, -moons, -comets, Imaging & Spectroscopy, Status Report

Free-floating “Planets” In The Macrolensed Quasar Q2237+0305

by Keith CowingJanuary 12, 2024January 12, 2024

It has been claimed that the variability of field quasars resembles gravitational lensing by a large cosmological population of free-floating planets with mass of about 10 Earths.

On the left panel, we have Himmelblau’s function, while the center panel displays its contour diagram. The red points on the contours represent the global minima of the function. On the right panel, we can observe the application of the genetic algorithm with niching and sharing, specifically for Himmelblau’s function. -- astro-ph.CO

AI - Data - Apps - Cybernetics, Astronomy & Telescopes, Genomics, Proteomics, Bioinformatics, Status Report

Cosmological Parameter Estimation With Genetic Algorithms

by Keith CowingNovember 14, 2023November 14, 2023

The search for the optimal values, maxima or minima, of a complex function is an essential task in several fields where mathematical modeling is required. Genetic algorithms (GAs) are a […]

Simplified illustration for the occupation of cells or ‘planets’ in a static universe. The centremost cell is occupied first and ‘life’ or ‘civilisation’ propagates towards neighbouring cells following the order (1) → (2) → (3) → (4). -- astro-ph.CO

Astronomy & Telescopes, Habitable Zones, SETI & Technosignatures, Societal Issues, Status Report

Percolation of ‘Civilisation’ in a Homogeneous Isotropic Universe

by Keith CowingSeptember 14, 2023

In this work, we consider the spread of a ‘civilisation’ in an idealised homogeneous isotropic universe where all the planets of interest are habitable. Following a framework that goes beyond […]

Astrobiology (general), SETI & Technosignatures, Status Report

The TAP Equation: Evaluating Combinatorial Innovation In Biocosmology

by Keith CowingJanuary 16, 2023January 16, 2023

We investigate solutions to the TAP equation, a phenomenological implementation of the Theory of the Adjacent Possible.

SETI & Technosignatures

Implications of a search for intergalactic civilizations on prior estimates of human survival and travel speed

by Keith CowingJune 28, 2021

We present a model where some proportion of extraterrestrial civilizations expand uniformly over time to reach a cosmological scale. We then ask what humanity could infer if a sky survey […]