Category Archives: History of Science & Epistemology

Cosmogenesis (4) : The Creator

Sequel of the preceding post Cosmogenesis (3) : Time and Creation

The Creator

The fundamental theological question about the Creation is: who created the universe? The Christian doctrine of the Holy Trinity asserts that God comprises three Persons: the Father, the Son and the Holy Spirit. Some theologians have regarded God as the first Person of the Trinity, “the omnipotent Father”, Creator of heaven and earth. Others have focused on the image of the “Spirit of God moving upon the face of the waters” and envisaged the Holy Spirit as the Creator. Others again, in an attempt to reconcile these viewpoints, have maintained that the Holy Trinity itself created the world – a reminder of the Vedic belief in a supreme being incarnated as a single body (Trimurti) with three heads: those of Brahma, Vishnu and Siva.

The Hindu Triad. One of the central images of Indian mythology is the Hindu Triad (Trimurti) of Brahma, the creator, Vishnu, the maintainer, and Siva, the destroyer. In this picture they are shown combined into a single body with four arms. Album of paintings of Indian gods and rulers, 1831. Paintings with captions in Tamil and French. BNF, Manuscripts, Indian 744.
The Hindu Triad. One of the central images of Indian mythology is the Hindu Triad (Trimurti) of Brahma, the creator, Vishnu, the maintainer, and Siva, the destroyer. In this picture they are shown combined into a single body with four arms.
Album of paintings of Indian gods and rulers, 1831. Paintings with captions in Tamil and French. BNF, Manuscripts, Indian 744.

These different theological perspectives are reflected throughout the Middle Ages (in fact right up to the 18th century) in religious art, where one or other interpretation of the Genesis story is illustrated in mosaics, paintings, sculptures, stained glass windows, illuminations and engravings.

The most familiar image of the Creator is the patriarchal figure of the Father (the archetypal example being Michelangelo’s fresco on the ceiling of the Sistine Chapel).

God the Father Dividing the Light from the Darkness. In this 16th century engraving, which was clearly influenced by the work of Michelangelo, the Creator, in the form of the first Person of the Holy Trinity, God the Father, is dividing the light (represented by the sun) from the darkness (represented by the moon). Engraving by Raphael Sadeler, in Thesaurus Historia..., 1585
God the Father Dividing the Light from the Darkness. In this 16th century engraving, which was clearly influenced by the work of Michelangelo, the Creator, in the form of the first Person of the Holy Trinity, God the Father, is dividing the light (represented by the sun) from the darkness (represented by the moon).
Engraving by Raphael Sadeler, in Thesaurus Historia…, 1585
Young Christ as Creator. The wonderful fresco adorning the cupola of the baptistery of San Giovanni in Padua is the work of the Florentine artist Giusto Dei Menabuoi, who was active in the second half of the 14th century. It shows God the Son as Creator. Giusto Dei Menabuoi, [The Creation of the World], 14th century.
Young Christ as Creator. The wonderful fresco adorning the cupola of the baptistery of San Giovanni in Padua is the work of the Florentine artist Giusto Dei Menabuoi, who was active in the second half of the 14th century. It shows God the Son as Creator.
Giusto Dei Menabuoi, [The Creation of the World], 14th century.

As the Holy Spirit the Creator is represented by a dove (the ancient Christian symbol of the Divine Spirit) – in the work of Robert Fludd, for example – or by the Hebrew word “Jehova” surrounded by a symbol of fire (recalling the burning bush from which Moses received the word of God). In a few cases the Creator is shown as a young Christ figure – in the 13th century mosaics of the Basilica of San Marco in Venice and the 14th century frescos of Giusto Dei Menabuoi in Padua, for example. Continue reading

Cosmogenesis (3) : Time and Creation

Sequel of the preceding post Cosmogenesis (2) : Chaos and Metamorphosis

Time and Creation

In any discussion of the creation of the world the paradoxical and complex question of temporality inevitably arises. If the Creation is regarded as an event, it must have taken place at some point in time, on a specific date. If time is regarded as a linear phenomenon, as it is in the Western world, this necessarily raises the problem whether anything existed before the Creation and, if so, what. But if time itself existed before the Creation, it cannot be part of the world as we know it – something which is difficult to imagine…

A Treatise on the Hexameron. St Ambrose (c. 339-394), who was bishop of Milan, was a believer in "Platonic Christianity" and one of the first Church Fathers, along with Origen and St Basil, to deliver sermons on the six days of the Creation, which he collected into a treatise. His Hexameron (shown here in an 11th century manuscript copy) is more than an exegesis; it is a veritable encyclopaedia anticipating those of the Middle Ages: the third book is concerned with plants, the fifth with birds and fish, and the second part of the sixth book with the anatomy of the human body. Paris, BNF, Manuscripts, Lat. 1720.
A Treatise on the Hexameron. St Ambrose (c. 339-394), who was bishop of Milan, was a believer in “Platonic Christianity” and one of the first Church Fathers, along with Origen and St Basil, to deliver sermons on the six days of the Creation, which he collected into a treatise. His Hexameron (shown here in an 11th century manuscript copy) is more than an exegesis; it is a veritable encyclopaedia anticipating those of the Middle Ages: the third book is concerned with plants, the fifth with birds and fish, and the second part of the sixth book with the anatomy of the human body.
Paris, BNF, Manuscripts, Lat. 1720.

This paradox was pondered by Medieval scholars, who were forced to conclude that the world and time were created simultaneously. In the fourth century the Bishop of Milan, St Ambrose, wrote in his Hexameron: “In the beginning of time, therefore, God created heaven and earth. Time proceeds from this world, not before the world.”[1]. In the early 13th century the French philosopher and theologian William of Auvergne (also known as William of Paris) pursued a similar line of reasoning in his thinking about time: “Just as there is nothing beyond or outside the World, since it contains and includes all things, so there is nothing before or preceding time, which began with the creation of the World, since it contains all the periods of which it is comprised. This poses the question: What was before the beginning of time? or, since the word ‘before’ implies the existence of time, In the time preceding the beginning of time, did anything exist?”[2]

The same questions continue to be asked today, and scientists who are asked to give public lectures on big bang theory and the expansion of the universe commonly face two kinds of questions: “What was there before the big bang?” and “What is there for the universe to expand into?” – in other words “Did time exist before time began?” and “Is there space beyond the limit of space?” The solution of modern physics to these paradoxes is that the universe consists of space-time and therefore the creation of the world cannot be regarded as a temporal phenomenon. Continue reading

Cosmogenesis (2) : Chaos and Metamorphosis

Sequel of the preceding post Cosmogenesis (1) : From Myth to Myth

Chaos and Metamorphosis

 

The ancient Greeks had a great variety of myths relating to the history of the world. Although they all shared a language and a culture, each village, each tribe had its own beliefs, its own version of the Creation story and its own gods who were responsible for cosmic order.

213 The Birth of the Gods According to Hesiod's Theogony (8th-7th century BC) is a history of the gods. It begins with Gaea, goddess of the Earth, the primordial element from which all the deities emerged. By herself she gave birth to the sea and the sky as well as to the gods Uranus and Pontus; by Uranus she then mothered numerous other deities: the Titans (including Cronos) and Titanesses, the Cyclops and the Giants. The work continues with an account of how Zeus became lord of the universe after decisive battles against the Titans and against the monster Typhoeus. This story of the creation of the world out of the struggle between the forces of order (cosmos) and the forces of disorder (chaos) had a strong influence on Greek cosmological thinking. In this illustration by Georges Braque, Hesiod is seen receiving the torch of Hebrew tradition from Moses. Hesiod, Theogony, Paris, Maeght, 1955.
The Birth of the Gods According to Hesiod’s Theogony (8th-7th century BC) is a history of the gods. It begins with Gaea, goddess of the Earth, the primordial element from which all the deities emerged. By herself she gave birth to the sea and the sky as well as to the gods Uranus and Pontus; by Uranus she then mothered numerous other deities: the Titans (including Cronos) and Titanesses, the Cyclops and the Giants. The work continues with an account of how Zeus became lord of the universe after decisive battles against the Titans and against the monster Typhoeus. This story of the creation of the world out of the struggle between the forces of order (cosmos) and the forces of disorder (chaos) had a strong influence on Greek cosmological thinking.
In this illustration by Georges Braque, Hesiod is seen receiving the torch of Hebrew tradition from Moses.
Hesiod, Theogony, Paris, Maeght, 1955.

Hesiod’s Theogony (8th-7th century BC) was the first attempt to synthesize these traditions, which probably dated back to the Assyrian and Babylonian civilizations. In recounting the stages in the emergence of the gods from primordial chaos Theogony offers an answer to the eternal questions of cosmogony: who created the world; what were the basic materials from which it was made; which came first, the gods, the stars or the elements?

Not only did Theogony have a strong influence on Greek thought, it also anticipated in many ways today’s theories of the origin of the world – particularly the idea of primordial chaos. Since the universe appears to have an ordered structure (albeit an imperfect one), it seems logical to regard the state which preceded the Creation as one of disorder and confusion. This notion has provoked greater controversy than almost any other in the history of cosmogony.

Ovid’s Metamorphoses also trawled Greek mythology, as well as Roman legend, in attempting to reconstruct the series of metamorphoses the world had undergone between the original state of Chaos and Julius Caesar’s supposed transformation into a star:

“Before the sea and the lands and the sky that covers all,
there was one face of nature in her whole orb
(they call it Chaos), a rough unordered mass,
nothing except inactive weight and heaped together
the discordant seeds of unassembled things.” [i] Continue reading

Cosmogenesis (1) : From Myth to Myth

Introduction

Every society has a story, rooted in its most ancient traditions, of how the earth and sky originated. Most of these stories attribute the origin of all things to a Creator -whether god, element or idea.

In the Western world all discussions of the origin of the world were dominated until the 18th century by the story of Genesis, which describes the Creation as an ordered process that took seven days. The development of mechanistic theories in the 18th century meant that the idea of an organized Creation gave way to the concept of evolution, and in the 19th century astrophysicists discovered that stars had their origin in clouds of gas. Big bang theory, conceived at the beginning of the 20th century, was subsequently developed into a more or less complete account of the history of the cosmos, from the birth of space, time and matter out of the quantum vacuum until the emergence of life.

Today sophisticated telescopes show us how the first galaxies were formed, how clouds of hydrogen gave birth to stars and how the planets emerged from swirling dust. We now know that creation is still going on in our universe but the origin of life remains an enigma. How did life forms appear? The universe’s best kept secret continues to baffle scientists.

From Myth to Myth

What are the origins of the universe, of the sky, of the earth, of life, of man? These questions have given rise to many different myths and legends and continue to be the subject of intensive research by astrophysicists, biologists and anthropologists. What were once fanciful stories are now scientific models but, whatever form they take, ideas about the origins of the universe both reflect and enrich the imagination of the people who generate them. Every society has developed its own stories to explain the creation of the world; most of them are ancient myths rooted in religion.

Whereas in monotheistic religions God is believed to have existed before the Creation, in most other kinds of religion the gods themselves are thought to originate from a creative element such as Desire, the Tree of the Universe, the Mundane Egg, Water, Chaos or the Void.

Babylonian Gods. An inscription on the back of this stone carving tells us that it was a gift from the Kassite king Melishishu II to his son. The picture shows the symbols representing the gods carved on the front. On the right the principal deities -Anu, god of the sky, and Enlil, god of the atmosphere - are each shown as a sort of tiara standing on a plinth. Next a ram's head above a creature half-goat half-fish represents Ea, god of the Waters of the Abyss. The symbol on the left might be for the goddess Ninhursag. Above these are the three celestial divinities: a crescent for Sin, god of the moon, a star for Ishatar and an image of the sun for Shamash. Stone from Kassite era (1202-1188 BC). Paris, Louvre.
Babylonian Gods. An inscription on the back of this stone carving tells us that it was a gift from the Kassite king Melishishu II to his son. The picture shows the symbols representing the gods carved on the front. On the right the principal deities -Anu, god of the sky, and Enlil, god of the atmosphere – are each shown as a sort of tiara standing on a plinth. Next a ram’s head above a creature half-goat half-fish represents Ea, god of the Waters of the Abyss. The symbol on the left might be for the goddess Ninhursag. Above these are the three celestial divinities: a crescent for Sin, god of the moon, a star for Ishatar and an image of the sun for Shamash.
Stone from Kassite era (1202-1188 BC). Paris, Louvre.
The Chinese giant Pangu
The Chinese giant Pangu

Ideas like these appear in the Rig-veda, one of the four sacred books of the Brahmins and the oldest surviving written record of Indian culture which were compiled between 2000 and 1500 BC. The Tree of the Universe, symbol of the outward growth of the world and of its organic unity, is mentioned in ancient Indian legends as well as in those of the Babylonians and Scandinavians (who call it Yggdrasil). The anthropomorphic symbol of Desire was invoked by the Phoenicians and by the Maoris of New Zealand. The Mundane Egg, from which the Hindu Prajapatis (lords of all living things) emerged, also gave birth to the gods Ogo and Nommo, worshipped by the Dogon of Mali, and the Chinese giant Pan Gu as well as constituting the celestial vault in the legend of Orpheus.

Birth of Gods and Cosmic Egg according to the Upanishad
Birth of Gods and Cosmic Egg according to the Upanishad

A belief in some such primordial element, of which there are traces in every culture, underlies man’s thinking about the history of the cosmos like a primitive universal symbol buried in the collective subconscious. This may explain the vague links which can always be discerned between this or that creation myth and modern scientific descriptions of the origin of the universe – for example, big bang theory. There is therefore nothing mysterious or surprising about these correspondences other than that certain ways of thinking about the world should be so ingrained in the human mind. Continue reading

My books (2) : Glorious Eclipses

Until now I published as an author 30 books in my native language (French), including 14 science essays, 7 historical novels  and 9 poetry collections (for the interested reader, visit my French blog  here.
Although my various books have been translated in 14 languages (including Chinese, Korean, Bengali…), 4 of my essays have been translated in English.

The second one was :

Glorious Eclipses : Their Past, Their Present, Their Future

Translated from French by Storm Dunlop
Cambridge University Press, 2001 -ISBN 0 521 79148 0

GEclipsesThis beautiful volume deals with eclipses of all kinds – lunar, solar and even those elsewhere in the Solar System and beyond. Bringing together in one place all aspects of eclipses, it is written by the perfect team : Serge Brunier is a life-long chaser of eclipses, and internationally-known astronomy writer and photographer, whilst Jean-Pierre Luminet is a famous astrophysicist with a special interest in astronomical history. Lavishly illustrated throughout, Glorious Eclipses covers the history of eclipses from ancient times, the celestial mechanics involved, their observation and scientific interest. Personal accounts are given of recent eclipses – up to and including the last total solar eclipse of the 20th century : the one on August 11th 1999 that passed across Europe, Romania, Turkey and India. This unique book contains the best photographs taken all along its path and is the perfect souvenir for all those who tried or wished to see it. In addition, it contains all you need to know about forthcoming eclipses up to 2060, complete with NASA maps and data.

 

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EXCERPT : FOREWORD

Why should a theoretical astrophysicist, who has rarely peered through the eyepiece of a telescope, preferring to speculate on the invisible architecture of space-time by means of dry equations, be interested in eclipses, to the extent of writing a book about them?

It is true that Einstein’s general theory of relativity, which has been a constant intellectual delight for me over so many years, was first proved experimentally thanks to a ‘simple’ solar eclipse. That was on 29 May 1919. But such an argument satisfies only the intellect. When it comes to the soul, it demands a greater spectacle, a more tangible emotion.

I was not yet ten on 15 February 1961, when a total eclipse of the Sun crossed the Provence where I was born. All I can recall is preparing smoked glass under the watchful eye of our schoolmistress. Clouds over Cavaillon probably spoilt the spectacle, because I have no memory of the eclipse itself…

Then… then I waited nearly forty years before finally seeing a total eclipse of the Sun. That was on 26 February 1998, in the Sierra Nevada de Santa Maria, in the north of Colombia. Serge Brunier and a few other colleagues, genuine eclipse chasers, had finally convinced me that any astrophysicist worthy of the name should not ‘die a fool’! It is true that, obviously, such a recurrent and ‘nearby’ astronomical event might seem somewhat prosaic to someone who spends his life in abstract research on models of the Big Bang, black holes, and the realms of space-time.

On that day, however, between 10:59 and 11:03, I experienced what John Couch Adams described so well, some 150 years before. The English mathematician-astronomer, less accustomed to handle telescopes than complex equations of celestial mechanics – he predicted the existence of the planet Neptune through calculation – witnessed a total eclipse of the Sun for the very first time in his career during the summer of 1846. He subsequently described the extraordinary emotions he felt as an astronomer – and, moreover, an experienced one – who realized that he was a novice when he discovered this astounding cosmic drama for the very first time.

The darkness that descends suddenly in the very middle of the brilliance of the day; this new light that arises from the obscurity; the planets aligned like a necklace of pearls in a configuration that is never seen by night; and the Sun’s flamboyant corona…

These few minutes in which time seems suspended, create the almost palpable feeling of being, transiently, part of the invisible harmony that rules the universe. It is as if a sudden opening in the opaque veil of space allows our inner vision to reach into the otherwise hidden depths of the cosmos, giving us humans – mere insignificant specks of dust – an all-too-brief instant to see the other side of the picture.

To me, the invisible is not restricted to dark objects that our telescopes cannot detect. It is also, and in particular, the secret architecture of the universe, the insubstantial framework of our theoretical constructs. I have always been moved by black. Not black as in absence, but rather black as revealing light. According to the painter Francois Jacqmin ‘Shadow is an insatiable star-studded watchfulness. It is the black diamond that the soul perceives when the infinite rises to the surface.’ Astrophysics and cosmology team with examples where black is all-important. It is in the black of the night that one sees stars, or, in other words, that one perceives the immensity of the cosmos. This same night-time darkness reveals the whole evolution of the cosmos, and the finite nature of time. The mass of the universe is largely dominated by dark matter; massive, non-luminous objects, which through their gravitational attraction govern the dynamics of the cosmos. As for black holes, the epitome of invisibility, they are perhaps secret doorways opening onto other regions of space-time.

Another aspect of eclipses enthrals me: their historical and cultural dimension. I have always been attracted by the way in which different forms of human invention interact. Science, despite being an effective and rational approach to truth, nevertheless remains incomplete. Art, philosophy, and the comparative study of traditions, myths and religions, are all complementary approaches that are indispensable for anyone who wants to gain a greater insight into where they fit in the cosmic scheme of things.

In unfolding the story of people, their civilizations, and their relationships with heavenly phenomena, one cannot but be fascinated to see how past eclipses have influenced their course. The impression of a supernatural power engendered by the sudden disappearance of the Sun or the Moon has often struck human beings, frightened by an apparently hostile and incomprehensible nature, to the extent of changing their behaviour.

That’s enough. My colleague, Serge Brunier, and I decided to write a book that alternated between these ‘two voices’. After all, the various types of eclipses are created by the Earth and the Moon taking it in turn to pass in front of each other beneath the blazing Sun…

Eclipses are a benign contagious virus, which once it has infected you, recurs at intervals. Which is why, for the eclipse of 11 August 1999, I went deep into the Iranian desert, to be (almost) certain of finding a sky devoid of clouds.

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PRESS REVIEWS

An extrordinarily beautiful book, Glorious Eclipses guides us elegantly through the history of obscurations of the sun and moon – from the ancient Chinese belief that a dragon was devouring the daytime star through current theories and on to celestial events forthcoming in the next six decades. Some of the most startling images come from the days when photography was in its infancy and astronomers still made drawings of eclipses.

Scientific American, June 2001


Darkness at noon

At first sight, this is the ultimate eclipse book. Oversize, well-produced photographs in a large-format book are accompanied by interesting text covering a wide variety of eclipses phenomena. The partnership of an astronomer writer/editor and a professional astronomer, albeit a cosmologist, successfully brings the beauty of total solar eclipses to the fore.

Although the writers alternate, the difference is not jarring, perhaps thanks to the expert translator, Storm Dunlop. In a chapter entitled “The great cosmic clockwork”, Serge Brunier, long-time editor of the French popular astronomy journal Ciel et Espace, discusses the many kinds of eclipses and occultations (when one astronomical body occults, or hides, another). He even includes the eagerly awaited 2004 transit of Venus – the passage of Venus across the face of the Sun. This will be the first transit of Venus visibe from Earth since 1882.

The reproduction of photographs in 25 cm x 35 cm format on heavy stock is outstanding. For example, we see Saturn’s rings extending across a double page for almost half a metre in a Hubble Space Telescope image. The authors justify using this image, which shows the shadow of Saturn’s satellite Titan on Saturn’s clouds, by pointing out that it corresponds to an eclipse of the Sun by Titan as seen from Saturn. It’s a pity, though, that Brunier calls himself an “eclipse chaser” – that common but misleading phrase seemps to imply that people can outrun, or even outfly, eclipses, which has never been done.

Brunier is responsible for some of the most magnificent photographs, such as one from the 1991 total solar eclipse visible from the Mauna Kea Observatory in Hawaii, with a few telescopes in the foreground. But the image I found most arresting is not one of this; it is a wide-angle shot of the 1991 eclipse viewed through a hole in the clouds and showing the front of Reims Cathedral in the left foreground.

In his chapters on the history and cultural significance of eclipses, Jean-Pierre Luminet reproduces a remarkable set of historical images related to solar and lunar eclipses from around the world. These are no doubt related to his work on an exhibition of astronomical atlases held in Paris at the Bibliothèque Nationale in 1998.

It was good to read about myths that cast eclipses in a favourable light rather than as evil omens. Luminet also describes the history of scientific discovery through observations of solar eclipses. One example is the discovery at the 1868 total solar eclipse of the spectrum of the solar chomosphere – the layer of the Sun just above the surface that becomes briefly visible at the beginning and end of totality. The element helium was also discovered at this eclipse.

There is much that is excellent in the book. The charts of future eclipses at the end of the book are redrawn at the highest quality. Lunar eclipses are included in the text, photos and charts, looking almost as dramatic on the page as the solar ecipses, even though they are much less so in reality. As a book of history, myth, literature, photography and expeditionary experiences, Glorious Eclipses is outstanding, despite its omission of the solar research carried out at recent eclipses.

Jay Pasachoff, Nature, vol. 410, 29 march 2001.


Wonder of day turned into light

A total eclipse of the Sun is about as astonishing a treat as nature provides. For a few minutes, the Moon exactly covers the Sun, making night from day and displaying the otherwise invisible solar atmosphere. This book celebrates eclipses of both Sun and Moon (the rather less spectacular sweeping of Earth’s shadow across the lunar surface) from many directions, including the complex history of eclipse observations and their declining but still real scientific value.

Serge Brunier and Jean-Pierre Luminet are respectively a science journalist and photographer, and a senior astronomer. This book, well translated from French by Storm Dunlop, makes the most of their strengths. It displays a deep understanding of history, some gripping science and a wealth of images, both of eclipses and of the many ways in which they have been represented over the years.

(…)

If you want to take up eclipse chasing, the book’s maps of future eclipses will tell you when and where to be, and its illstrations will tell you what to expect and how to observe in safety. There are explanations of the eclipse cycle, or Saros, and of the fact that in the far future, there will be no more solar elipses as the Moon’s distance from the Earth increases.

The book also provides generous coverage of lunar eclipses and of related events such as occultations and transits. There is even space to reveal how planets in other solar systems are being detected as they eclipse their own star as seen from Earth. Eclipses still make cutting-edge science thousands of years after they first caused dismay to our ancestors.

Martin Ince, Deputy Editor, The Times Higher, March 9 2001.


Not in the shade

This attractive and beautifully illustrated book, by two Paris astronomers and dedicated eclipse-chasers, was originally published in French under the title Eclipses, Les Rendez-vous Celestes (Larousse-Bordas/HER, 1999). The present English translation is by Storm Dunlop. This book is a veritable mine of information on eclipses and is suitable for anyone who has an interest in eclipses, be they amateur or professional astronomer, photographer or historian.

The scene is set in the first chapter, which captures much of the appeal of total solar eclipses and leaves the reader in no doubt as to why eclipse chasers will travel vast distances to witness a few minutes of totality.

In chapters two and three, the historical and literary aspects of both solar and lunar eclipses are discussed. Although there is some sound history in the first of these chapters, there is also much speculation – especially with regard to such torical and literary aspects of both such diverse matters as Stonehenge, Thales, and the date of the Crucifixion of Jesus. Regrettably, there are several serious errors. Thus the “Assyrian tablet dating from the

2nd century BC” (p40) is in fact from Babylonia, several centuries after the demise of Assyria. Thucydides reports three eclipses, not just two (p43). “According to the Evangelists,” Jesus was not “crucified on a Thursday,” (p44). Chapter three contains some intriguing literary allusions to eclipses in prose and poetry – both ancient and modern.

Chapters four to seven provide the main substance of this book and are both fascinating and informative. They deal respectively with: the cause of both lunar and solar eclipses; lunar and planetary occultations and also Mercury and Venus transits; total solar eclipse phenomena; and the famous or infamous (depending on the wearher) 1999 eclipse. In particular, it is gond to see a discussion of occultations and transits – which, in a sense, are eclipses in their own right.

The final chapter contains helpful hints for observing and photographing eclipses and also a series of attractive maps showing the visibility of future solar and lunar eclipses – with special emphasis on those over the next 20 years. Unfortunately many of the individual solar eclipse maps (p156–69) are confusing; in each case the maps show “Total eclipse begins at sunrise”, “Path of totality” and “Total eclipse ends at sunset” whether the eclipse was annular or total.

Overall, this is a splendid hook, profusely illustrated.

F Richard Stephenson. Astronomy & Geophysics, 2001 December (Vol.42), 6.33

Doppelmayer-14-P

The Rise of Big Bang Models (5) : from Gamow to Today

Sequel of previous post : Lemaître

In this series of posts about the history of relativistic cosmology, I  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaître, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaître, although his papers remain mostly  unquoted.

First English Edition of The primeval atom
First English Edition of The primeval atom

Lemaître, the "Big bang Man"
Lemaître, the “Big bang Man”
The hot big bang model

By 1950, when Lemaître published a summary, in English, of his theory, entitled The Primeval Atom: An Essay on Cosmogony, it was thoroughly unfashionable. Two years previously the rival theory of a « steady state » universe, supported principally by Thomas Gold in America and by Hermann Bondi and Fred Hoyle in Britain, had met with widespread acclaim. Their argument was that the universe had always been and would always be as it is now, that is was eternal and unchanging. In order to obtain what they wanted, they assumed an infinite Euclidean space, filled with a matter density constant in space and time, and a new « creation field » with negative energy, allowing for particles to appear spontaneously from the void in order to compensate the dilution due to expansion ! Seldom charitable towards his scientific adversaries, Fred Hoyle made fun of Lemaître by calling him « the big bang man ». In fact he used for the first time the expression « big bang » in 1948, during a radio interview.

Thomas Gold, Hermann Bondi and Fred Hoyle, promotors of the steady state theory"
Thomas Gold, Hermann Bondi and Fred Hoyle, promotors of the steady state theory”

The term, isolated from its pejorative context, became part of scientific parlance thanks to a Russian-born American physicist George Gamow, a former student of Alexander Friedmann. Hoyle therefore unwittingly played a major part in popularising a theory he did not believe in; he even brought grist to the mill of big bang theory by helping to resolve the question why the universe contained so many chemical elements. Claiming that all the chemical elements were formed in stellar furnaces, he was contradicted by Gamow and his collaborators Ralph Alpher and Robert Hermann. The latter took advantage of the fact that the early universe should have been very hot. Assuming a primitive mixture of nuclear particles called Ylem, a Hebrew term referring to a primitive substance from which the elements are supposed to have been formed, they were able to explain the genesis of the lightest nuclei (deuterium, helium, and lithium) during the first three minutes of the Universe, at an epoch when the cosmic temperature reached 10 billion degrees. Next they predicted that, at a later epoch, when the Universe had cooled to a few thousand degrees, it suddenly became transparent and allowed light to escape for the first time. Alpher and Hermann calculated that one should today receive an echo of the big bang in the form of « blackbody » radiation at a fossil temperature of about 5 K. Their prediction did not cause any excitement. They refined their calculations several times until 1956, without causing any more interest; no specific attempt at detection was undertaken. Continue reading

The Rise of Big Bang Models (4) : Lemaître

Sequel of previous post : Dynamical solutions

In this series of posts about the history of relativistic cosmology, I  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaître, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaître, although his papers remain mostly  unquoted.

The discovery of expanding space

The 1920’s were precisely the time when the experimental data began to put in question the validity of static cosmological models. For instance, in 1924 the British theorist Arthur Eddington pointed out that, among the 41 spectral shifts of galaxies as measured by Vesto Slipher, 36 were redshifted ; he thus favored the de Sitter cosmological solution while, in 1925, his PhD student, the young Belgian priest Georges Lemaître, proved a linear relation distance-redshift in de Sitter’s solution. The same year 1925, Edwin Hubble proved the extragalactic nature of spiral nebulae. In other words, he confirmed that there existed other galaxies like our own, and the observable Universe was larger than previously expected. More important, the radiation from the faraway galaxies was systematically redshifted, which, interpreted as a Doppler effect, suggested that they were moving away from us at great speed. How was it possible ?

Arthur Eddington (1882-1944)
Arthur Eddington (1882-1944)

Young-Lemaitre
The young Georges Lemaître

It was Lemaître who solved the puzzle. In his 1927 seminal paper Un univers homogène de masse constante et de rayon croissant, rendant compte de la vitesse radiale des nébuleuses extragalactiques, published in French in the Annales de la Société Scientifique de Bruxelles, Lemaître calculated the exact solutions of Einstein’s equations by assuming a positively curved space (with elliptic topology), time varying matter density and pressure, and a non-zero cosmological constant. He obtained a model with perpetual accelerated expansion, in which he adjusted the value of the cosmological constant such as the radius of the hyperspherical space R(t) constantly increased from the radius of the Einstein’s static hypersphere RE at t = – ∞. Therefore there was no past singularity and no « age problem ». The great novelty was that Lemaître provided the first interpretation of cosmological redshifts in terms of space expansion, instead of a real motion of galaxies : space was constantly expanding and consequently increased the apparent separations between galaxies. This idea proved to be one of the most significant discoveries of the century. Continue reading

The Rise of Big Bang Models (3) : Friedmann’s Dynamical solutions

Sequel of previous post : Static Solutions

In this series of posts about the history of relativistic cosmology, I  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaître, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaître, although his papers remain mostly  unquoted.

The Friedmann’s pioneering work

expanding-friedmannIn an article which appeared in 1922, entitled On the Curvature of Space (see Luminet 2004 for reference and translation), the Russian physicist Alexander Friedmann took the step which Einstein had balked at : he abandoned the theory of a static universe, proposing a “dynamic” alternative in which space varied with time. As he stated in the introduction, “the goal of this notice is the proof of the possibility of a universe whose spatial curvature is constant with respect to the three spatial coordinates and depend on time, e.g. on the fourth coordinate.

friedmann-equation
The Friedmann’s Equation. R is the curvature radius of space, rho the mass density, Lambda the cosmological constant, k the sign of the space curvature, G the gravitational constant, c the speed of light

Thus he assumed a positively curved space (hypersphere), a time variable matter density and a vanishing cosmological contant. He obtained his famous “closed universe model”, with a dynamics of expansion – contraction. Continue reading

The Rise of Big Bang Models (2) : Static solutions

Sequel of previous post :  From Myth to Science

In this series of posts about the history of relativistic cosmology, I  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaître, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaître, although his papers remain mostly  unquoted.

The History of Relativistic Cosmology can be divided into 6 periods :

– the initial one (1917-1927), during which the first relativistic universe models were derived in the absence of any cosmological clue.

– a period of development (1927-1945), during which the cosmological redshifts were discovered and interpreted in the framework of dynamical Friedmann-Lemaître solutions, whose geometrical and mathematical aspects were investigated in more details.

– a period of consolidation (1945-1965), during which primordial nucleosynthesis of light elements and fossil radiation were predicted.

– a period of acceptation (1965-1980), during which the big bang theory triumphed over the « rival » steady state theory.

– a period of enlargement (1980-1998), when high energy physics and quantum effects were introduced for describing the early universe.

– the present period of high precision experimental cosmology, where the fundamental cosmological parameters are now measured with a precision of a few %, and new problematics arise (nature of the dark energy, topology of the universe, new cosmologies in quantum gravity theories, etc.)

Let us follow chonologically the rather hectic evolution of the ideas in the field. Continue reading

The Rise of Big Bang Models (1) : from Myth to Science

In this series of posts about the history of relativistic cosmology, I’ll  provide an epistemological analysis of the developments of the field  from 1917 to 2006, based on the seminal articles by Einstein, de Sitter, Friedmann, Lemaitre, Hubble, Gamow and other main historical figures of the field. It appears that most of the ingredients of the present-day standard cosmological model, including the accelation of the expansion due to a repulsive dark energy, the interpretation of the cosmological constant as vacuum energy or the possible non-trivial topology of space, had been anticipated by Lemaitre, although his papers remain mostly  unquoted.

 From Myth to Science

What are the origins of the universe, of the stars, of the earth, of life, of man? These questions have given rise to many different myths and legends, and today they are more than ever the subject of intensive research by astrophysicists, biologists and anthropologists. What were once fanciful stories are now scientific models; but whatever form they take, ideas about the origins of the universe both reflect and enrich the imagination of the people who generate them. Every society has developed its own stories to explain the creation of the world; all of them are ancient myths rooted in religion.

Whereas in monotheistic religions God is believed to have existed before the Creation, in most other kinds of religion the gods themselves are thought to originate from a creative element such as Desire, the Tree of the Universe, the Mundane Egg, Water, Chaos or the Void.

Tiamat-Marduk
Marduk slays the chaos dragon, Tiamat, in the Babylonian creation epic (British Museum, London)

A belief in some such primordial element, of which there are traces in every culture, underlies man’s thinking about the history of the cosmos like a primitive universal symbol buried in the collective subconscious. This may explain the vague links that can always be discerned between this or that creation myth and modern scientific descriptions of the origin of the universe –for example, big bang theory. There is therefore nothing mysterious or surprising about these correspondences other than that certain ways of thinking about the world should be so ingrained in the human mind.

An interesting approach, by the scientist and philosopher Wolfgang Smith (published in 2012)
An interesting approach, by the scientist and philosopher Wolfgang Smith (published in 2012)

In fact scientific and mythical explanations of the origins are neither complementary not contradictory; they have different purposes and are subject to different constraints. Mythical stories are a way of preserving collective memories, which can be verified neither by the storyteller nor by the listener. Their function is not to explain what happened at the beginning of the world but to establish the basis of social or religious order, to impart a set of moral values. Myths can also be interpreted in many different ways. Science, on the other hand, aims to discover what really happened in historical terms by means of theories supported by observation. Often considered to be anti-myth, science has in fact created new stories about the origin of the universe: big bang model, the theory of evolution, and the ancestry of mankind. It is therefore hardly surprising that the new creation stories developed by scientists tend to be regarded by the general public as modern myths.

Continue reading

Quote by Tsiolkovsky

To set foot on the soil of the asteroids, to lift by hand a rock from the Moon, to observe Mars from a distance of several tens of kilometers, to land on its satellite or even on its surface, what can be more fantastic? From the moment of using rocket devices a new great era will begin in astronomy: the epoch of the more intensive study of the firmament. ­

Konstantin E. Tsiolkovsky, Father of Russian Astronautics, 1896