Related papers: How Rare Are Extraterrestrial Civilizations and Wh…

One of the most interesting unsolved questions in science today is the question of life on other planets. At the present time it is safe to say that we do not have much of an idea as to whether life is common or exceedingly rare in the…

Is life most likely to emerge at the present cosmic time near a star like the Sun? We consider the habitability of the Universe throughout cosmic history, and conservatively restrict our attention to the context of "life as we know it" and…

A number of years ago the estimates of astronomers and astrophysicists were that the earliest galaxies took about 2.5 to 3 billion years to form, that is, that they did not appear until 2.5 to 3 billion years after the Big Bang. Those…

Is life most likely to emerge at the present cosmic time near a star like the Sun? We address this question by calculating the relative formation probability per unit time of habitable Earth-like planets within a fixed comoving volume of…

We devise and exploit a data-driven, semi-empirical framework of galaxy formation and evolution, coupling it to recipes for planet formation from stellar and planetary science, to compute the cosmic planet formation rate, and the properties…

Here, we ask a simple question, i.e. "at what cosmic time, at the earliest, did life first appear in the universe?" Given what we know about the universe today, there may be some partial answers to this question, but much will still have to…

The history of life on Earth and in other potential life-bearing planetary platforms is deeply linked to the history of the universe. Since life as we know it relies on chemical elements forged in dying heavy stars, the universe needs to be…

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…

Life emerged on the Earth within the first quintile of its habitable window, but a technological civilization did not blossom until its last. Efforts to infer the rate of abiogenesis, based on its early emergence, are frustrated by the…

In this work, we explore constraints on the emergence and longevity of technologically intelligent civilizations in our Galaxy, considering the Fermi paradox. We argue that under optimistic assumptions about the probability of life and…

The ease of interstellar rocket travel is an issue with implications for the long term fate of our own and other civilizations and for the much-debated number of technological civilizations in the Galaxy. We show that the physical barrier…

At this point in time, there is very little empirical evidence on the likelihood of a space-faring species originating in the biosphere of a habitable world. However, there is a tension between the expectation that such a probability is…

In this article I review the main methods for determining the age of the Universe. I describe how to determine the age of the oldest known systems at z=0, the system of galactic globular clusters, using different techniques. I also describe…

What is the chance we start a conversation with another civilization like our own? Our technological society produced signals that could be received by other extraterrestrial civilizations, within a sphere around us with a radius of $\sim…

The link between black holes and star formation allows us to draw a connection between black holes and the places and times extraterrestrial intelligences (ETIs) had a greater chance of emerging. Within the context of the gap paradigm for…

There are three independent techniques for determining the age of the universe: via cosmochronology of long-lived radioactive nuclei, via stellar modelling and population synthesis of the oldest stellar populations, and via the precision…

An extrapolation of the genetic complexity of organisms to earlier times suggests that life began before the Earth was formed. Life may have started from systems with single heritable elements that are functionally equivalent to a…

The early start to life naively suggests that abiogenesis is a rapid process on Earth-like planets. However, if evolution typically takes ~4Gyr to produce intelligent life-forms like us, then the limited lifespan of Earth's biosphere…

Despite great advances in our understanding of the formation of the Solar System, the evolution of the Earth, and the chemical basis for life, we are not much closer than the ancient Greeks to an answer of whether life has arisen and…

If life on Earth had to achieve n 'hard steps' to reach humanity's level, then the chance of this event rose as time to the n-th power. Integrating this over habitable star formation and planet lifetime distributions predicts >99% of…