Content Listing

Summary

A new synthesis: the Biological Universe

A remarkable shift in our scientific world picture is taking place, potentially as fundamental in its consequences as the new views put forth by Copernicus in the sixteenth century, or by Darwin in the nineteenth. Although astronomers have long been involved with the prospects for extraterrestrial life, their fundamental task since Newton has been to apply physics to a lifeless Universe. On the other hand, biologists have pursued their studies for centuries in cosmic isolation, meaning that biology considered life on Earth, with no attention paid to its cosmic context. Today, however, both camps are recognizing fruitful and exciting avenues of research created by a new synthesis. Biology is vastly enriched when attention is paid to a broader context for life as we know it, as well as the possibilities for other origins of life. And astronomy is coming to realize that the themes of cosmic, galactic, stellar, and planetary evolution, which have become central over the past century, must now also incorporate biological origin(s) and evolution(s). Historian of science Steven Dick (1996) has hailed this new synthesis as the Biological Universe. Although astronomy and biology are its two primary poles, many other disciplines are also vital components, in particular Earth and planetary sciences.

Summary

White men think of ice as frozen water, but Inuit think of water as melted ice. To us, ice is the natural state.

Nuka Pinguaq, nineteenth-century native Arctic hunter (Kobalenko, 2002)

Introduction

Ice is the “natural state” or predominant form of water in our Solar System. The surfaces of most planets and moons are currently at temperatures well below the freezing point of pure water, including two of the more promising sites in the search for traces of extraterrestrial life, Mars and Europa. The amount of water-ice on Europa exceeds the volume of liquid water on Earth. Comets, considered potential vectors for precursors or early stages of life, are also icy bodies (Chapter 3). Even Earth may have undergone a series of complete (or near-complete) glaciations in its recent history, earning the title “Snowball Earth” (Section 4.2.4).

The presence of the liquid phase of water, however, is essential to the prospering of life as we know it. In order to study where liquid water can occur, we must understand scales ranging from the structure of the water molecule to the temperatures possible on a planetary surface or subsurface. In our Solar System, only Earth allows for a planetary surface with abundant liquid water (Chapter 4). Mars, however, may well have some liquid water in permafrost (perennially frozen soil) beneath its surface today (Section 18.4.1), and the evidence is strong that Europa and perhaps other moons of Jupiter have water oceans below their icy crusts (Chapter 19).

Summary

Overview

Why history?

The core questions of astrobiology are not new. They have always been asked and are central to Western intellectual history. How did life begin? How has it changed? What is the relation of humans to other species? Does life exist elsewhere? If so, where might it be and what is it like? Although these questions are ancient, what is new are the tools at hand to search for answers, ranging from robotic spacecraft to genome sequencing, from electron microscopes to radio telescopes. These tools and other factors (see the Prologue and Chapter 2) appear to have brought astrobiology to a point where it is gelling into something qualitatively different – our first sound attack on these questions. But is this so? Or is today no different from any other time in the past few centuries?

In every era, including our own, scientists can do no more than tackle questions with the best tools available, apply the best insight they can muster, and struggle to fashion a consensus as to the nature of the world. In this manner our understanding has progressed, for example, from the “animalcules” that van Leeuwenhoek described three hundred years ago to the richness of contemporary microbiology. To understand such a thread as it meanders through history, we need to document more than the accumulation of facts. When evaluating a given episode, historians of science look carefully at evidence of not only the science itself, but also of the larger enveloping context.

Summary

Introduction

Europa, one of the four large satellites of Jupiter, is nearly the size of Earth's Moon. Tidal flexing driven by Jupiter's gravity and sustained by an orbital resonance with two other jovian satellites, Io and Ganymede, results in significant heat dissipation within Europa. Calculations indicate that this tidal heating is sufficient to maintain liquid water beneath Europa's ice crust. Moreover, observational evidence suggests that it is indeed probable, but not yet completely certain, that Europa harbors a subsurface ocean of liquid water whose volume is about twice that of Earth's oceans. The likely presence of abundant liquid water places Europa among the highest priority targets for astrobiology.

To support life, Europa would also require an inventory of biogenic elements and a source of sufficient free energy. The ability to support life does not of course guarantee that the origin of life took place on Europa, or that life is present today; answering these questions will require further exploration. This chapter considers Europa in an astrobiological context, distinguishing among what is known, what is supported by evidence but still uncertain, and what remains more speculative. We conclude with a discussion of future missions that will be needed to address current geological and astrobiological questions.

Jupiter and its satellites

The planet Jupiter, orbiting the Sun at 5.2 AU, is more massive than the other planets in the Solar System combined; it is 3.3 times more massive than Saturn and 318 times more than the Earth.

Summary

Introduction and summary

In the original Star Trek series, Episode 26 (“The Devil in the Dark”), Mr. Spock uses a hand-held tricoder to remotely detect a silicon-based lifeform known as a “Horta.” Unfortunately, NASA engineers have not yet invented the tricoder to aid in our own search for life on Mars or Europa. In fact they are not even close to understanding the principle by which a tricoder is able to distinguish lifeforms, either carbon or silicon, from non-living matter. Even The Physics of Star Trek (Krauss, 1995) is notably silent on the operating physics behind the tricoder. How then do we achieve the Prime Mission of Astrobiology: to boldly go and seek out new lifeforms on distant worlds? The answer, not surprisingly, is that we base our search for life elsewhere on what we know about life on Earth. The basic elements of this approach can be summarized as follows.

Summary

Introduction

The frequency of animal life in the Universe must be some function of how often it arises, and then how long it survives after evolving. Both of these factors may be significantly influenced by the frequency and intensity of mass extinctions, brief intervals of time when significant proportions of a planet's biota are killed off. They are killed by one or some combination of too much heat or cold, not enough food or nutrients, too little (or too much) water, oxygen, or carbon dioxide, excess radiation, incorrect acidity in the environment, or environmental toxins. Based on the history of Earth's life, mass extinctions seemingly have the potential to end life on any planet where it has arisen.

Mass extinctions do more than threaten biota. They may also play a large part in evolutionary novelty. On Earth there have been about 15 such episodes during the last 500 Myr, five of which eliminated more than half of all species then inhabiting our planet. These events significantly affected the evolutionary history of Earth's biota: for example, if the dinosaurs had not been suddenly killed off following a comet collision with the Earth 65 Ma, there probably would not have been an Age of Mammals, since mammals were held in evolutionary check so long as dinosaurs existed. The wholesale evolution of mammalian diversity took place only after the dinosaurs were swept from the scene. Mass extinctions are thus both instigators as well as foils to evolution and innovation.

Summary

Introduction

Solon's visit to Croesus (translated from Herodotus Histories 1.29–33)

When Sardis was at its most prosperous, all the teachers (σοϕισταί) of the Greek world paid a visit, including Solon the Athenian … On arrival, he was entertained by Croesus in the palace, and after three or four days slaves at Croesus' command showed him around the treasury in all its greatness and magnificence. When he had dutifully examined and admired everything as best he could, Croesus asked him, ‘Guest from Athens, we have frequently been told of your wisdom and of the sight-seeing journeys you have undertaken all over the world to foster it. Now then, I find myself quite unable to resist asking you if you have ever seen anyone who is the happiest (ὄλβιος) man in the world.’ He asked this hoping that he himself was the happiest. Solon did not flatter him, but spoke the plain truth. ‘Yes, O King, Tellos the Athenian.’ Croesus, astonished at this reply, acidly asked the reason for his judgment. Solon replied, ‘First, Tellos’ city was prosperous, and he had fine sons, and he saw children born to them all, and all of them survived; second, he was as well off as a man can expect, and his death was glorious. For in a battle between the Athenians and their neighbours in Eleusis, it was he who rescued the situation, routed the enemy and died gloriously.

Summary

This book is written to be used in step with Reading Greek (Text) of the Joint Association of Classical Teachers' Greek Course. In it will be found:

A: Section-by-section grammatical explanations and exercises to support the reading of the twenty sections of the Text (pp. 1–368). While we recommend that the Text is tackled before students turn to the grammar and exercises, no harm will be done by taking a different view.
B: A Reference Grammar, which summarises and sometimes expands upon the essential features of the grammar met in the Course (pp. 369–464).
C: A number of Language Surveys which look in detail at some of the more important features of the language (pp. 465–496).
D: A Total Vocabulary of all words that should have been learnt – this has been appended to the Text as well – followed by a list of proper names (pp. 497–520).
E: A vocabulary for the English-Greek exercises (pp. 521–528).
F: Indices to the grammar and to Greek words (pp. 529–543), originally constructed by Professor W. K. Lacey and his students at the University of Auckland, New Zealand and here revised.

It would be impracticable to produce an exhaustive grammar of the whole Greek language. We have therefore concentrated attention on its most common features. Students and teachers should bear in mind that the first aim of this grammar is to help students to translate from Greek into English.

Summary

Introduction

The reason that Euelpides gave for leaving Athens was that he and Peisetairos had been unjustly found guilty in a law-suit. Whatever the actual rights and wrongs of the matter, the Athenians' reputation for litigiousness was notorious throughout the Mediterranean. Pericles (Περικλῆς) had introduced pay for dikasts (δικασταί, jurors) in c. 461 BC, so that even the poorest might be encouraged to take part in the democratic process of judging their fellow-man, and it would appear that some men were happy to scrape a living out of serving as dikasts. The courts handled not only judicial business, but political cases as well: their power was, potentially, enormous, and could be wielded to deadly effect. There was little ‘procedure’ in the courts; certainly no judge to guide dikasts and clarify the law; no question of the dikasts (usually 501 Athenian males) retiring to discuss what they had heard; few rules of evidence; and no cross-questioning of witnesses. The dikasts listened to both sides, and voted on the issue at once. In such an atmosphere, the law could easily be abused.

In Wasps, Aristophanes presents his vision of the ‘typical’ Athenian dikast, and leaves us to ponder its implications for the administration of justice in Athens.

In World of Athens: the law-courts 6.39ff.

Law-court mania in Athens

It has been estimated that, when allowance is made for festivals, ἐκκλησίαι and so on, juries might sit on between 150 and 200 days in the year … If we are to believe Aristophanes' Wasps of 422, some elderly Athenians had a passion to serve.

Textbooks

Refine search

Refine search

Actions for selected content:

37983 results in Cambridge Textbooks

Prologue

Summary

Index

PART VII - Future of astrobiology

15 - Life in ice

Summary

PART V - Potentially habitable worlds

1 - History of astrobiological ideas

Summary

19 - Europa

Summary

PART IV - Life on Earth

22 - How to search for life on other worlds

Summary

17 - Mass extinctions

Summary

Acknowledgements

Section Four A–D: Lawlessness in Athenian life

Section Two A–D: The glorious past

Frontmatter

Section Nineteen A–F: The story of Adrastos

Summary

Preface

Summary

Section Eleven A–C: Aristophanes' Akharnians

Section Nine A–J: Aristophanes' Wasps

Summary

Contents

Notes on illustrations

Textbooks

Refine search

Refine search

Actions for selected content:

Save Search

37983 results in Cambridge Textbooks

Summary

Summary

Summary

Summary

Summary

Summary

Summary

Summary

Summary