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We report the results of a detailed numerical study designed to estimate both the absolute age and the uncertainty in age (with confidence limits) of the oldest globular clusters. Such an estimate is essential if a comparison with the…
A new solution to the Fermi Paradox is presented: probes or visits from putative alien civilizations have a very low probability until a civilization reaches a certain age (called the Contact Era) after the onset of radio communications. If…
Globular clusters are the oldest objects in the Galaxy whose age may be accurately determined. As such globular cluster ages provide the best estimate for the age of the universe. The age of a globular cluster is determined by a comparison…
Abiotic emergence of ordered information stored in the form of RNA is an important unresolved problem concerning the origin of life. A polymer longer than 40--100 nucleotides is necessary to expect a self-replicating activity, but the…
If advanced civilizations appear in the universe with an ability and desire to expand, the entire universe can become saturated with life on a short timescale, even if such expanders appear rarely. Our presence in an apparently untouched…
It is found that the ages of the most metal-poor Galactic globular clusters are probably around 18 Gyr. On the other hand a Hubble parameter of 82 +/- 8 km/sec/Mpc (in conjunction with the standard Einstein-de Sitter model with an Omega =1…
A habitable zone of a star is defined as a range of orbits within which a rocky planet can support liquid water on its surface. The most intriguing question driving the search for habitable planets is whether they host life. But is the age…
Large telescopes have allowed astronomers to observe galaxies that formed as early as 850 million years after the Big Bang. We predict when the first star that astronomers can observe formed in the universe, accounting for the first time…
It is often suggested that extraterrestial life sufficiently advanced to be capable of interstellar travel or communication must be rare, since otherwise we would have seen evidence of it by now. This in turn is sometimes taken as indirect…
The Anthropocene is a proposed time subdivision of the earth's history correlated to the strong human perturbation of the ecosystem. Much debate is ongoing about what date should be considered as the start of the Anthropocene, but much less…
The history of astronomical discovery shows that many of the most detectable phenomena, especially detection firsts, are not typical members of their broader class, but rather rare, extreme cases with disproportionately large observational…
I summarize in terms of evolutionary population synthesis models our current understanding of stellar populations in different environments, from star clusters in nearby galaxies to distant galaxies in clusters or seen through gravitational…
Given the fact that Earth is so far the only place in the Milky Way galaxy known to harbor life, the question arises of whether the solar system is in any way special. To address this question, I compare the solar system to the many…
The prediction that (due to the limited amount of hydrogen available as fuel in the Sun) the future duration of our favourable terrestrial environment will be short (compared with the present age of the Earth) has been interpreted as…
In this review I will describe a number of recent advances in extragalactic astronomy. First of all I will describe our current best estimates of the star formation history of the Universe. Then I will describe measurements of local…
Analyses of various cosmological probes, including the latest Cosmic Microwave Background anisotropies, the 2dF Galaxy Redshift Survey and Cepheid-calibrated distance indicators suggest that the age of expansion is $13 \pm 3$ Gyr. We…
The globally-averaged star formation rate in the Universe has been steadily declining since at least z~1. This may be due either to very local processes operating within the average galaxy, or to external, environmental effects.…
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…
How long a technological civilization remains active, and what determines whether it collapses or persists, is a central question for both projecting humanity's future and assessing the prevalence of detectable intelligence in the galaxy.…
From a modern perspective cosmology is a historical science in so far that it deals with the development of the universe since its origin some 14 billion years ago. The origin itself may not be subject to scientific analysis and…