David Sinclair Stevenson

Carlton le Willows · Science

Bayesian models have been used to infer the prevalence of life and intelligence elsewhere in the universe for several decades. In most, the emergence of intelligent life is judged against the time it took to emerge following the emergence of life as whole. However, such approaches are flawed in that they do not relate the emergence of “intelligent...

We present a novel mode of cultural evolution whereby some forms of transmission may be modelled as quasispecies. The model incorporates the effect of high rates of error in certain forms of communication; while also building on the structural similarities between biological molecules and written language. Firstly, both written language and key bio...

This manuscript illustrates some aspects of the transfer of information in a cultural context. The quasispecies concept relates to the error-prone transfer of information, particularly in RNA viruses. However, error rates in some aspects of human discourse are comparably high or higher than in these viruses. Therefore, we model such discourse as qu...

The hypothesis article in Astrobiology considers the temporal link between the emergence of continental crust in the meso- to neo-Archaean and the emergence and subsequent expansion of oxygenic photosynthesis ahead of the GOE. There is growing evidence from the geological record suggesting that the expansion of cyanobacteria (or their oxygenic anc...

In this hypothesis article, we propose that the timing of the evolution of oxygenic photosynthesis and the diversification of cyanobacteria is firmly tied to the geological evolution of Earth in the Mesoarchaean to Neoarchaean. Specifically, the diversification of species capable of oxygenic photosynthesis is tied to the growth of subaerial (above...

Biological evolution may be measured by the growth in the complexity of the genetic information present, manifest as an increase in biological diversity in ecosystems. Likewise, we suggest that cultural evolution occurs through the evolution of its “genome” – its language. Biological evolution may be measured as growth in the Shannon entropy of the...

Plate tectonics drives variation in sea-level, over intervals of approximately10 7-10 8 years. These variations may have significant effects on the pace of (biological) evolution through the elimination of terrestrial niches and the expansion of shallow-water marine niches. However, within the solar system, only the Earth experiences this kind of t...

In this article, we partially quantify the biological potential of an exoplanet. We employ a variety of biogeographical analyses, placing biological evolution in the context of the geological evolution of the planet as a whole. Terrestrial (as in Earthly) biodiversity is tightly constrained in terms of species richness by its environment. An organi...

In this chapter we explore the processes that sculpt the long-term evolution of a planet’s surface. These are integral to developing a deeper understanding of what controls the long-term habitability of planets.

Terrestrial life emerged in a murky and violent period of history that has left little trace of its existence. Astrobiologists have been left to infer its likely origins from what meager and indirect evidence nature has left for us to decipher. We know, for example, that one of the building blocks of cells—a group of chemicals called amino acids—ar...

To state the obvious, this chapter represents a moving target. Although one can, for example, blithely state that of the end of December 2017, a total of 3605 planets had been confirmed, of which 1414 were Neptune-like; by the time this book goes to press that figure will, most likely, be out of date. Therefore, consider this chapter as an incomple...

As above, so below. Although the fervor of research builds over the impact of the geosphere on planetary habitability, considerably more research is going into understanding how planetary atmospheres may influence the same property. This chapter expands upon, improves the accuracy of, and produces viable models of atmospheres for planets with diffe...

Although life may be ubiquitous, the ultimate question is whether intelligent (or even complex multicellular) life is equally abundant. Moreover, given a few certainties, such as an energy and nutrient source, will life inevitably follow a path to complexity? Although Chaps. 8 and 9 deal with some specifics, this chapter will focus on developing so...

In the last decade two new planetary systems have emerged from radial velocity data, those of Proxima Centauri and TRAPPIST-1. Proxima is a 0.12 solar mass red dwarf and the closest star to our Sun, making it a particularly attractive target for further investigation. Meanwhile, the older TRAPPIST-1 system has seven planets, several of which could...

Possibly the most important consequence of plate tectonics is the cycling of materials into and out of the mantle. Such a conveyor belt delivers carbon dioxide into the interior in the form of carbonate rock and returns this gas to the atmosphere, thereby modulating the planetary greenhouse effect. One of the more subtle and poorly understood proce...

You cannot consider life on other worlds before first considering their host star. This determines their orbital period, the intensity of the radiation the planet receives and the distribution of wavelengths over which meaningful intensities of radiation are emitted. This chapter is dedicated to the two most abundant classes of stars in the univers...

When the first edition of this book was written there were only two plausible candidate systems that might host planets in their stars’ habitable zone, Gliese 581 and Gliese 667C. Both systems hosted a number of super-terrans, whose numbers varied often by the month as radial velocity data was interpreted, reinterpreted, discarded, recovered—only f...

The concept of exoplanetary habitability is evolving. The driving force is a desire to define the biological potential of planets and identify which can host complex and possibly intelligent life. To assess this in a meaningful manner, climate models need to be applied to realistic surfaces. However, the vast majority of climate models are develope...

The maximum height trees can grow on Earth is around 122–130 m. The height is constrained by two factors: the availability of water, and where water is not limiting, the pressure available to drive the column of water along the xylem vessels against the pull of gravity (cohesion tension). In turn the height of trees impacts the biodiversity of the...

This thought-provoking book looks at the nature of red dwarf systems as potential homes for life. Realistically, what are the prospects for life on these distant worlds? Could life evolve and survive there? How do these planetary surfaces and geologies evolve? How would life on a planet orbiting a red dwarf differ from life on Earth? And what are t...

Planets that orbit M-class dwarf stars in their habitable zones are expected to become tidally-locked in the first billion years of their history. Simulations of potentially habitable planets orbiting K and G-class stars also suggest that many will become tidally-locked or become pseudo-synchronous rotators in a similar time frame where certain cri...

‘Where is everybody?’ remarked Enrico Fermi, leading to the famous, and as yet unanswered ‘Fermi's Paradox’ as this remark has come to be known. While there are a number of possible solutions that vary from the distances are too great; the cost prohibitive or civilizations naturally decline or eliminate themselves before interstellar travel becomes...

A planet may be defined as habitable if it has an atmosphere and is warm enough to support the existence of liquid water on its surface. Such a world has the basic set of conditions that allow it to develop life similar to ours, which is carbon-based and has water as its universal solvent. While this definition is suitably vague to allow a fairly b...

A speculative idea to use atmospheric gravity waves to detect volcanic activity on the planet Venus - and conceivably elsewhere. I also question whether the same technique could be used to detect earthquake activity on Venus given the likely rigidity of the Venusian crust. Just to update this file, I never pursued this as research, however, I note...

Throughout this book we’ve presented life as something of an inevitability. Life began on Earth not because of a series of random, rare events but because there was a high probability that its chemistry would naturally produce systems that we would recognize as living organisms. The chemicals used by life on Earth are ubiquitous in the universe, an...

What forms might life take elsewhere in the universe, and would we recognize it if we saw it? Those are the questions posed by this chapter. Although many of the cases examined may simply be variants of life on Earth, we’ll ask whether the truly fantastic is possible, given the constraints on what it means to be alive.

Now that we’ve explored some scenarios for life’s emergence and evolution—and seen how tenacious life really is—we can begin to examine the flip side of creation: extinction. Now, it may come as something of a surprise, but this book was initially constructed around the premise that life could be eliminated. Although this may sound a tad brutish, t...

Over the last few chapters we’ve examined the development, elaboration and potential we or our surroundings have to eliminate life. It’s now time to consider how life must, inevitably, be defeated, not by us or the random collision of Earth with another object, but by the death of the universe. The universe, as a vessel for the creation of life, ha...

On the face of it what life is seems fairly obvious. If you think about humans, their pet animals or an animal on a farm, then you know that living things run around, breathe, are conscious (we like to think to varying extents) and are very much tangible things.

Chapter 1 introduced the broad themes of life. This chapter examines how nature supports its precious cargo.

Chapters 1 and 2 defined what we might consider living and non-living—and refined ideas of how life might acquire some of these characteristics. However, we did not look at how life might have emerged.

There is a myth that is utterly entrenched in society. This myth serves to misinform many of the reality of evolution. This myth is taught widely in schools, on television and sadly pervades much of the Internet. The myth concerns entropy and equates entropy with disorder. Since the word “disorder” became synonymous with entropy, its use to discred...

Let’s imagine that we actively wanted to wipe out life on Earth—or simply to eliminate the dominant species, us. Given what we already know about how life has weathered the various storms nature has thrown at it, exterminating life might seem rather tricky. However, sterilizing a planet can be done, albeit with far greater difficulty than it would...

This book looks at the persistence of life and how difficult it would be to annihilate life, especially a species as successful as humanity. The idea that life in general is fragile is challenged by the hardiness of microbes, which shows that astrobiology on exoplanets and other satellites must be robust and plentiful. Microbes have adapted to virt...

This chapter illustrates the fluid nature of planetary weather and climate. Climate is a dynamic creature that changes with the activity of the planet’s central star, the Sun, and with other dynamic forces that operate on and within planets. The climate of the Earth has repeatedly changed dramatically over the eons since it has formed.

The East Asian Monsoon is perhaps the most important climatic feature of the Earth. Across 60° of latitude and around 80° of longitude, winds reverse direction from summer to winter and back again, year after year. The cycle brings rains to two continents: Asia in the northern summer and northern Australia in the southern summer. The present monsoo...

Titan, Triton and Pluto form a triad of similar icy bodies in the outer solar system. Each has a diameter around 2500–3500 km across with an interior dominated by ice and rock. Each plays host to an atmosphere dominated by nitrogen. Here, however, the similarity ends. The atmospheres of Triton and Pluto are tenuous affairs, a thin veil of gases tha...

In principle this chapter concerns luminous phenomena, some of which are natural, while others might well be tricks of the light. Around 2000 thunderstorms are active within the Earth’s atmosphere at any one time. Most of these occur in the afternoon when the land or sea is at its hottest. Although almost anyone reading this book will be familiar w...

Take two planets of roughly the same mass and composition and place them at similar distances from their parent star. You’d clearly expect them to end up as near twins. However, what the Solar System shows is that it doesn’t take much of a butterfly to drastically alter the fate of worlds.

Superficially the ice giants, Uranus and Neptune, are simply smaller cousins of the gas giants, Jupiter and Saturn, but it doesn’t take much examination to realize that this analogy is only skin deep. Aside from their smaller size and much lower tropospheric temperature, the interiors of these worlds are composed chiefly of the ices ammonia and wat...

Mars was born unlucky. Thanks to an unfortunate proximity to the proto-Jupiter, the debris from which Mars coalesced was severely depleted in mass. This left Mars something of an undersized runt, setting the tone for its future evolution and ultimate atmospheric demise. Unlike the Earth and Venus, Mars has a relatively slight gravitational pull, wh...

Saturn and Jupiter have more in common than they have in isolation, thus Chap. 7 compares and contrasts the two giant masters of the Sun’s planetary realm. Despite some issues of scale, the broad brush strokes of each planet are rather similar. Within this broad canvas there are specific differences in the appearance of each world and the behavior...

Since 1992 astronomers and planetary scientists have been able to feast upon a bewildering variety of planets that lie outside our parochial system of eight, and a bit, worlds. We now have planetary systems orbiting white dwarfs, red giants, neutron stars, as well as a bewildering array of more mundane main sequence stars.

Weather is such a ubiquitous part of our lives that most of us take it completely for granted. Yet it controls nearly every aspect of our life, from our route to and from work to the food we eat and more. The weather is the talking point for the random meeting, or the casual chat on the Metro. The weather is something that we all have an opinion on...

There now exists a number of computer models that show some success in predicting the meteorological conditions in the ensuing winter in the northern hemisphere. These examine the Arctic Oscillation (AO) and are successful up to two months in advance of the beginning of meteorological winter. Other models, which are based upon the North Atlantic Os...

Open clusters have played as much of a central role in astronomer’s understanding of stellar evolution as globular clusters have. For instance, by examining the overall population of the stars in open clusters, astronomers have learned how stars of different masses go from their stable hydrogen-burning phase to red giants and beyond (Fig. 5.1). Sta...

Variable stars and star cluster go together like cheese and wine. In Chap. 1, we saw how Shapley used RR Lyrae variable stars to map out the general scale of the galaxy; and later how Hubble used Cepheids to show that M31, the Andromeda galaxy, lay distant to our galactic shores. Stellar variability is integral to our understanding of how stars wor...

Star clusters are glorious objects to look at. The closest, such as the youthful Pleiades or the more mature Hyades, form little villages of light woven amongst the constellations and naturally attract the eye. With binoculars the six or seven stars of the Pleiades that are visible to the naked eye resolve into dozens of stars encased in a wispy ne...

Within the heart of an open cluster stars are spaced perhaps 1 light year apart. Nine trillion kilometers is a long way between stars, particularly if those stars are only moving at a few kilometers per second. What are the chances that they would ever encounter one another given their apparent distance? You’d think an encounter would be unlikely,...

When a star cluster forms, all of its constituent stars are moving relative to one another. The interstellar froth from which they formed was in constant motion and this continued as individual cloud cores (Chap. 2) continued to collapse into protostars then stars. For clusters with masses in the range of 100,000 to 1 million stars, the speeds are...

Stars shredded into pieces and nearby planets boiling away are among the images conjured up by the word “supernova.” Shockwaves pound outwards and turn rocky asteroids into cometary fluff, driving planetary shards from their orbits and showering neighboring star systems with waves of deadly radiation. It’s dramatic stuff. But what really happens in...

We have already seen that some supernovae can falter when large amounts of the shocked outgoing material achieve insufficient velocities to escape the developing neutron star. However, can this be so extreme that the supernova fails completely and the star dies alone in the dark?

What have some stars got in common with gamblers? Admittedly the answer may not seem obvious at first. However, the clue to solving this riddle lies with the fate of a class of transitional stars. These celestial bodies demarcate an evolutionary fence, separating the core-collapse supernovae and the formation of planetary nebulae. They present huge...

The taxonomic scheme devised in the 1950s has held up remarkably well, considering the dramatic growth in supernovae detection. In 1998 20 supernovae were discovered, but by 2007 this figure had risen to over 500 per year. With a vast array of automated medium-sized ‘scopes and a sizable army of dedicated astronomers, supernovae are pouring out of...

The basic tenant of the Type Ia supernova paradigm is that these explosions happen when a carbon-oxygen white dwarf gets to (or more precisely gets close to) a tipping point – the Chandrasekhar mass limit. It then ignites its store of inert carbon and oxygen. The resulting explosion decimates the white dwarf, leaving an expanding cloud of radioacti...

What’s blue, distant and very, very brilliant? With a growing litany of supernovae, one might imagine the discovery of another bright supernova in 2005 would simply add another chapter to this expanding tome, one which would soon fall into line with at least one of those already characterized. However, SN 2005ap proved to be a very troublesome supe...

Until the discovery of the bright and peculiar core-collapse supernovae, described in earlier chapters, Type Ia supernovae were the brightest known explosions in the universe. Astronomers had a pretty good idea about where these explosions arose. However, establishing the precise mechanism by which the explosions occurred, or the type of system tha...

At the heart of the majority of core-collapse supernova explosions lies a young neutron star. This is formed through the collapse of the 1.44–3 solar mass iron core left behind at the end of silicon fusion. When this body of iron grows sufficiently in mass, it becomes unstable to gravity and implodes, forming a remnant star composed primarily of ne...

We begin our journey with chance observations by the Vela spy satellite in 1973. A well-trodden path begins with the discovery of short bursts of high energy radiation. Fortunately for us these were not the signature of nuclear detonations on Earth but instead marked the violent destruction of something other-worldly. What that something was remain...

The fate of the most massive stars is an area fraught with uncertainty and is not without controversy. The stakes are high when it comes to this area of astrophysics, as some of the universe’s most exciting and violent phenomena are associated with these rarest of objects. Like ephemeral diamonds, these singular stars provoke intense emotions among...

Can a white dwarf, filled with carbon and oxygen, be more massive than the Chandrasekhar limit of 1.382 solar masses? In theory – and this is a very reliable theory – no. At this limit, or indeed somewhat less than this limit, the conditions in the core should turn carbon into iron and other elements, with disastrous consequences. However, in 2003...

Prior to the early part of the last decade, there were two rival theories for the formation of massive stars. In one model massive stars were produced by the merger of lower mass protostars within dense clusters of nascent stars. In the second model massive stars formed in exactly the same way as their lower mass brethren – through steady accretion...

An older book called Secrets of Space (Abacus books) was one of the first to split supernovae into different classes and more impressively describe the phenomenon of pair instability supernovae in all but name. It took another 20 years to see mention of this again, such was the uncertainty surrounding their existence. Indeed, they remained theoreti...

Not all stellar explosions are associated with the death of stars. Astronomers are familiar with novae, the explosive but non-fatal eruptions associated with white dwarf stars in binary systems (Chap. 13). They are also increasingly aware of temporary eruptions in very massive supergiant and LBV stars (Chaps. 3 and 8).

Stars begin as clouds of gas and dust, called nebulae, with temperatures hovering a few degrees Kelvin above absolute zero (−273 °C). If there is sufficient mass present within the cloud, gravity may overcome resistive forces and cause the cloud to collapse. Resistance against collapse is provided by the internal kinetic energy of the gas and dust...

What happens at the end of the life of massive stars? At one time we thought all these stars followed similar evolutionary paths. However, new discoveries have shown that things are not quite that simple. This book focuses on the extreme –the most intense, brilliant and peculiar– of astronomical explosions. It features highly significant observati...

To the human eye life seems a delicate, even an ephemeral, thing. After all, we occupy such a short, whimsical fraction of astrophysical time. We are so much less than the candy sprinkles on the universal cake. Yet our common perception of living organisms belies a deeper understanding of life itself. Although organisms expire with the same apparen...

The formation of stars and planets was until recently shrouded in dust, both literally and metaphorically. The basic underlying principle had been understood for over two centuries, having been proposed by the French mathematician Pierre Simon-Laplace and the Dutch philosopher Emmanuel Kant. The proposition was that stars were born from clouds of g...

Early on the morning of Boxing Day, 2004, the day following Christmas, a portion of Earth’s crust nearly 1,000 km long broke off the coast of Indonesia. One side of the fracture bounced up 15 m while the other slipped down towards Earth’s interior along a fault known as a megathrust. Nearly 300,000 people lost their lives in countries spanning the...

Skulking in the shadows of nearby brighter stars lies the 581st member of the Wilhelm Gliese’s catalog of nearby dim stars. The catalog contains nearly 1,000 stars organized according to their position and stellar properties. Gliese 581 is a low mass, red dwarf star weighing in at a little under one third the mass of our Sun with a surface temperat...

Carbon dioxide is regarded as a dirty chemical at present. The molecule conjures up images of melting ice caps, flooded cities, and animals and plants pushed to the edge of extinction. However, recent bad press hides carbon dioxide’s fundamental role in creating living worlds. Carbon dioxide is both a protective blanket and nurturer of complex life...

A star is a factory with a fixed supply of raw materials. The nature of its life is dictated by the amount of mass, and to a lesser extent, the nature of the materials bequeathed at birth. In essence the lower the mass, the cooler the star and hence the more sedately the star burns its fuel. This book is dedicated to the coolest stars in the univer...

Spinning wildly, with hundreds of revolutions per second, is the millisecond pulsar PSR B1257 + 12. Not the most glamorous-sounding object in the known universe. Yet any millisecond pulsar has led an extraordinary life. Its first breath is taken in the multi-billion-degree plasma generated in the heart of a collapsing star. As the star falls apart,...

Red dwarfs pose some unique challenges to any life that attempts to take a foothold on one of their worlds. The bulk of the radiation received at any orbiting planet’s surface is low energy infrared, rather than the dominantly visible wavelengths received at the surface of Earth. Water needs a critical input of energy if its bonds are to be broken....

According to military legend, German gunners encountered a strange phenomenon while attempting to shell Paris in 1918. They aimed their super-gun of the day, the 210 mm Long Max, at Paris from 70 miles to the northeast. It was said that despite a dogged determination on the part of the German military, the projectiles continually missed, curving aw...

Lying 22.1 light years from Earth is Gliese 667. Unlike Gliese 581, the Gliese 667 system is a far more interesting construct. For one thing there are three stars, not one. Two of these stars, 667A and 667B, are low mass, K-class orange dwarfs (Chap. 3) orbiting their common center of gravity. The orbit of both K-stars is very eccentric, with their...

Widespread antibiotic resistance is a major public health concern, and plants represent an emerging antibiotic exposure route. Recent studies indicate that crop plants fertilized with antibiotic-laden animal manure accumulate antibiotics; however, the molecular mechanisms of antibiotic entry and subcellular partitioning within plant cells remain un...

Recent studies have provided major new insights into the mechanism by which eukaryotic organisms initiate heterochromatin formation. Surprisingly, RNA appears to be a central component of the chromatin silencing machinery.

Transposon insertion mutagenesis is a powerful tool for understanding cereal gene function. Previous work has shown that Mutator-amplified fragment length polymorphism is an efficient and reproducible technique for amplifying sequences from individual plants, which flank the Mutator element. In this report, we show that by screening arrays of bacte...

The origin of translation has stimulated much discussion since the basic processes involved were deciphered during the 1960s and 1970s. One strand of thought suggested that the process originated from RNA replication in the RNA world (Weiner & Maizels, 1987, 1994). In this paper I seek to extend this model. The mRNA originates as a replication inte...

The origin of translation has stimulated much discussion since the basic processes involved were deciphered during the 1960s and 1970s. One strand of thought suggested that the process originated from RNA replication in the RNA world (Weiner & Maizels, 1987, 1994). In this paper I seek to extend this model. The mRNA originates as a replication inte...

We have used a universal adaptor amplification procedure to isolate random Mutator-tagged fragments from Mutator-active maize plants. Direct sequence characterization of 761 Mutator-tagged fragments indicated that a significant number were homologous to sequences within the public databases. The ability of Mutator-tagged fragments to detect homolog...

The immutans (im) mutant of Arabidopsis shows a variegated phenotype comprising albino and green somatic sectors. We have cloned the IM gene by transposon tagging and show that even stable null alleles give rise to a variegated phenotype. The gene product has amino acid similarity to the mitochondrial alternative oxidase. We show that the IM protei...

The immutans (im) mutant of Arabidopsis shows a variegated phenotype comprising albino and green somatic sectors. We have cloned the IM gene by transposon tagging and show that even stable null alleles give rise to a variegated phenotype. The gene product has amino acid similarity to the mitochondrial alternative oxidase. We show that the IM protei...