The Evolving Universe and the Origin of Life

The Evolving Universe and the Origin of Life Pekka Teerikorpi • Mauri Valtonen • Kirsi Lehto • Harry Lehto • Gene Byrd • Arthur Chernin The Evolving Universe and the Origin of Life The Search for Our Cosmic Roots 123 Dr Pekka Teerikorpi University of Turku Department of Physics and Astronomy Tuorla Observatory FI-21500 Piikki¨o Finland pekkatee@utu.fi Dr Mauri Valtonen University of Turku Department of Physics and Astronomy Tuorla Observatory FI-21500 Piikki¨o Finland mavalto@utu.fi Dr Kirsi Lehto University of Turku Department of Biology Laboratory of Plant Physiology FI-20014 Turku Finland klehto@utu.fi Dr Harry Lehto University of Turku Department of Physics and Astronomy Tuorla Observatory FI-21500 Piikki¨o Finland hlehto@utu.fi Dr Gene Byrd University of Alabama Department of Physics and Astronomy P.O Box 870324 Tuscaloosa AL 35487-0324 USA byrd@bama.ua.edu Dr Arthur Chernin Sternberg State Astronomical Institute Universitetskiy Prospect 13 Moscow Russia 119899 chernin@sai.msu.ru ISBN 978-0-387-09533-2 e-ISBN 978-0-387-09534-9 Library of Congress Control Number: 2008930766 c 2009 Springer Science+Business Media, LLC All rights reserved This work may not be translated or copied in whole or in part without the written permission of the publisher (Springer Science+Business Media, LLC, 233 Spring Street, New York, NY 10013, USA), except for brief excerpts in connection with reviews or scholarly analysis Use in connection with any form of information storage and retrieval, electronic adaptation, computer software, or by similar or dissimilar methodology now known or hereafter developed is forbidden The use in this publication of trade names, trademarks, service marks, and similar terms, even if they are not identified as such, is not to be taken as an expression of opinion as to whether or not they are subject to proprietary rights Cover illustration: Printed on acid-free paper springer.com Preface A golden thread runs through the history of humanity – even in prehistory, when writing was unknown, there was the need to understand, that restless spark within us We have written this book for anybody interested in the quest of knowledge – at least to the extent that he or she wishes to appreciate the main results of science, which has changed our way of thinking about the world Born in a society filled with applications of science and engineering, we often take all this for granted and not stop to think of the steps, invisible as they are in the distant past, that had to be taken before our world emerged We take our readers on a voyage from the treasures of the past to the frontiers of modern science which includes physics, cosmology, and astrobiology We divide the presentation into four parts, which approximately correspond to the major waves of scientific exploration, past to present The first wave, The Widening World View arose in Antiquity and re-emerging at the end of the Middle Ages, was based on visual observations of the world Quite a lot was accomplished with the naked eye, together with simple devices and reasoning Both Ptolemy and Copernicus belonged to this great era Around 1600, when the new sun-centered worldview was advancing and the telescope was invented, Galileo followed by many others, could see deeper and deeper in space This led, among other things, to determination of the distance to the Sun and to the other stars faintly glimmering in the sky In the twentieth century, remote galaxies were reached and observing windows other than optical were opened to astronomers A parallel wave we call Physical Laws of Nature was powered by the experimental/mathematical approach to physics, started by Galileo as well, and accelerated by the work of Newton toward modern physics This wave took us to the realm of atoms and elementary particles, and together with the parallel astronomical work finally led to the modern wave of exploration, the Universe, describing the earliest processes in its origin and expansion from a superdense state 14 billion years ago to our universe of galaxies today In our own times a new and fascinating wave of exploration of the universe began which we call Life in the Universe, when humanity learned to launch devices and even people beyond the Earth One is reminded of the words by Tsiolkovski “The v vi Preface planet is the cradle of intelligence, but you not live in the craddle for ever.” Up to now only the Moon has been visited by humans, but numerous space probes have delivered new and impressive information about the planets, asteroids, and comets of the Solar System, and about the Sun itself Astrobiology, the new interdisciplinary field of science, has thus received a strong boost forward, as now it has become possible to map in detail the wide range of conditions inside our planetary system and to see where life might have originated in addition to the Earth At the same time, thanks to the advancements in telescopes, astronomers have been able to discover other planetary systems and the count of known extrasolar planets now reaches hundreds These developments have given new perspectives for the role of life and the human race in the universe Two decades ago two of the authors (P.T., M.V.) wrote a book in Finnish, published by the Ursa Astronomical Association (“Cosmos – the developing view of the world”) The present book owes to that one for its general outline and spirit, but its contents reflect the team of writers with diverse specialties and the many new, even revolutionary developments in cosmology, space research, and astrobiology during these years In writing the text, we have had in mind a wide range of audience, from laymen interested in science to students of both humanities and sciences in universities Even professional scientists in physics or astronomy may find the historical parts and astrobiological excursions interesting, while for biologists it may be useful to refresh their knowledge of other sciences We write on an accessible level, avoiding mathematics and detailed explanations But the fact remains that some subjects of modern science, in physics, cosmology, and biology as well, are inherently complicated and difficult to describe “simply.” We have either skipped such topics or have given descriptions requiring some attentive reading We conclude some chapters with brief excursions to interesting “frontier” topics, in order to convey the reader a feeling of what kinds of things fascinate scientists today (strange phenomena of the microworld, many dimensional worlds, cosmological dark energy, the origin of life, the greenhouse effect, ) Finally, teachers may find this book useful for undergraduate college courses, particularly those who recognize that it is now difficult to divide science into traditional subjects or those who recognize the connections between humanities and the sciences To this purpose we provide a Web site document with a listing of interesting Web sites covering the parts of the text plus a collection of short multiple choice questions divided by subject: http://bama.ua.edu/∼byrd/Evolving UniverseWeb.doc We wish to thank several persons who have read parts of the manuscript or have in other ways helped this project, e.g., by allowing the use of illustrations We mention Yuri Baryshev, Andrej Berdyugin, Svetlana Berdyugina, Anthony Fairall, Andrea Gabrielli, Ismael Gognard, Jennifer Goldman, Sethanne Howard, Pekka Hein¨am¨aki, Janne Holopainen, Tom Jarrett, Andreas Jaunsen, Michael Joyce, Hannu Karttunen, Perttu Kein¨anen, Bill Keel, Tapio Korhonen, John Lanoue, JeanPierre Luminet, Seppo Mattila, Chris Mihos, Seppo Mikkola, Markku Muinonen, Sami Niemi, Kari Nilsson, Pasi Nurmi, Jyri N¨ar¨anen, Georges Paturel, Saul Preface vii Perlmutter, Luciano Pietronero, Laura Portinari, Travis Rector, Rami Rekola, Shane D Ross, John Ruhl, Allan Sandage, Markku Sarimaa, Aimo Sillanp¨aa¨ , Francesco Sylos Labini, Leo Takalo, Gilles Theureau, Malene Thyssen, Luc Viatour, Iiro Vilja, and Petri V¨ais¨anen We are grateful to Harry Blom, Christopher Coughlin, and Jenny Wolkowicki of Springer-Verlag, New York for very good collaboration and patience during the preparation process of this book Similarly, we thank Prasad Sethumadhavan of SPi Technologies India August 2008 The authors Contents List of Tables xvii Part I The Widening World View When Science Was Born Prehistoric Astronomy: Science of the Horizon Writing on the Sky Vault and on Clay Tablets Constellations and Horoscope Signs The Ionian Way of Thinking Pythagoras Invents the Cosmos 10 Science in Athens Anaxagoras Makes the Celestial Bodies Mundane The Atomic Doctrine Plato Establishes the Academy The Universe of Aristotle 13 13 14 15 18 Planetary Spheres and the Size of the Universe The Theory of Concentric Spheres The Epicycle Theory Hipparchus Discovers the Slow Wobbling of the Celestial Sphere Ptolemy The Size of the Spherical Earth Aristarchus of Samos – The Copernicus of Antiquity Enlarging the Universe On the Road Toward the Solar System 23 23 26 26 28 29 31 34 Medieval Cosmology Treasures of the Past The Cosmology of the Middle Ages Scholasticism: The Medieval Science 37 38 38 40 ix 506 space telescopes (cont.) Relikt-1 315 SOHO 72, CS Fig Spitzer 460 Uhuru 233 WMAP (Wilkinson Microwave Anisotropy Probe) 302, 305, 316–317, CS Fig & 25 Spallanzani, L 411 spectroscope 127–128, 130, 262, 447, 466 spectral classes 217–219 spectral lines 128–131, 187–188, 218–219, 245, 263–264, 273, 338–339, 340, 342–343, 349, 365 spectrum of gas 128–130, 189 of a planet 447, 451, 473 of a quasar 342–343, 349, of the Sun 127–129 of a star 131, 217–219, 262, 468 of blackbody radiation 132–133, 185, 312–314 Speusippos 32 spin 194, 338 Spitzer, L 340 stadium (unit of length) 29–30 Standish, M 114 star counts 240–244, 247–249 stars, individual Aldebaran 8, 89, 90, 218 alpha Centauri 87, 99, 152 Arcturus 220 Barnard’s star 87, 463 Betelgeuse 8, 90, 217, 218, 220, 221, 253 Castor 86 delta Cephei 244, 245 Eltanin 81–84 Polaris 17, 227, 245 Procyon 8, 90, 218 Proxima Centauri 87, 99 Rigel 8, 90, 218 Sirius 3, 8, 87, 89, 90, 91, 217, 218, 221, 226, 253, 264, 273, 325 Sirius B 91, 226, 273, 325 Vega 87, 218, 221 61 Cygni 87 stars, properties element abundances 128–131, 218–119, 222, 230, 311, 330, 358, 360, 363–364 energy generation 222–224, 395 formation 354, 358, 400 CS Fig 13 & 24 Main Sequence stars 220–224, 227, 360, 361, 463, 469, 472 Index red giant stars 220–221, 361 star model 220, 222 Stefan, J 132 Stefan’s law 133 stellar magnitude 27, 242, 244–247, 264, 302 St John, C 273 Stockton, A 349 Stoney, G 178 string theory 213 strings (cosmic) 356 Stromatolites 425 Struve, F 87, 88 stellar populations 252–251, 359–363 stoic philosophers 292 summer solstice 3, 29 Sun age 222–223, 395–396 distance 30, 32–34, 91, 93–97 energy source & luminosity 223–224, 317, 344, 408, 450, 471, 484, CS Fig movement in the sky 27, 49, 50 movement in space 243, 250, 264, 313 physical properties 222–223, 232, 408, 450, 471 temperature 222, 232, CS Fig 12 Sundman, K 118–119 supernova 54, 58, 78, 152, 225–231, 263, 275, 300–302, 311, 324, 331, 339, 358–361, 464, 472, CS Fig 23 supernova remnant 225, 229–230, 339, CS Fig 22 synchrotron 204, 206 synchrotron radiation 337 synodic period 23–26, 447 Swedenborg, E 116 T Takalo, L 343 Tammann, G 275–276 tauon 208, 209 Tayler, R 311 Taylor, F.E 398 tectonic plate motions 397–399, 406–407, 414, 426, 442, 449–450, 457 telegraph 139 telescope (see also: radio telescopes; space telescopes; Keck; VLT) Cassegrain type 77 invention of 44, 54, 68, 70, 71 Keplerian telescope 75, 81 reflecting telescope 76–78 Index resolution 75, 78, 345, 347, 437, 443, 448, 466 Schmidt telescope 283–284 zenith telescope 81 Thales 9–10, 18, 29 Thatte, N 466 Theaetetos 15 Theano 10 Theon 37 Theophilus 37 Theophrastus 236 theory of concentric spheres 23, 25 thermodynamics, laws of 171–172, 367–368 Theureau, G 225 third motion of the Earth 52 Thirring, H 167 Thomas Aquinas (St.) 38 Thomson, J.J 144, 178–180 Thomson, W 132–133, 141, 394–396 three body problem 116–119, 121, 203, 326, 359–360 threshold temperature 318 Thyssen, M Tian, F 417 tidal phenomena 116–117, 283, 340, 352, 402, 406, 425, 436, 452, 454–455, 470–472 Ting, S 208 time in relativity theory 151–154, 166–167 Titius, J (von Wittenberg) 113 Titius-Bode law 113–114, 461 Tombaugh, C 114 Toktaga 230 topology 304–307 transits of Venus 95–97 Tremain, S 469 trivium 47 Trumpler, R 249–250 T Tauri star 402 tunneling 191–192, 195 Tycho (Brahe) 50, 54–55, 57–60, 62, 63, 95, 236, 339 U Udry, S 468 Ultra Deep Field (HST) 295 unification 210–214 Uranus 23–24, 98, 111–114, 240–241, 402, 435–436, 450, 458–462, 468, 471 Urey, H 203, 207, 415–416 Ussher, J 393 Utzschneider, J von 85, 87 507 V Valenti, J 468 Vall´ee, J.P 254 Valtonen, M 348 van de Hulst, H 338 van Maanen, A 265–266, 278 Vaucouleurs, G de 275–276, 284, 439 Venus 7, 24–25, 51, 53–54, 58, 64, 70–71, 95–98, 113, 116, 273, 407–448, 433, 435–436, 447–452, 460, 462, 471, 473, 482 vernal equinox 7, 27–28, 40, 52, Very, F 263 Viatour, L 232 VIRGO 169 vitalism 369 VLBI (Very Long Baseline Interferometry) 347–348 VLT (Very Large Telescope) 347, CS Fig 21 Voigt, W 153 volcanoes on Earth 405–406, 414, 425, 429–430, 442 on other planets 439–440, 442, 446, 449, 452, 457, 458 Volkoff, G 228 Volta, A 137, 140 Vulcan 115, 438 V¨ais¨al¨a, Y 114, 284 V¨ais¨anen, P CS Fig 21 W Walker, G 289 Walker, G.A.H 464 Wallace, A 381, 438 Walsh, D 348 Walton, E 204–205, 207 water properties 385–388, 485 necessity for life 367, 385, 423–425, 427–428, 442, 471, 483 elsewhere in the universe 442–447, 450, 453–455, 457, 460, 471, 483 Ward, W 403 Watselrode, L 47 Watson, J 374 Watson, W 136 Waymann, R 349 Weber, J 168–169 Weber, W 139, 160 Wedgewood, T 132 Wegener, A 398, 400 Weinberg, S 210, 289, 321, Weinberg-Salam theory 210, 321–322, 356 508 Weismann, A 382 Wells, H.G 438 Westall, F 425 Westerhout, G 338 white dwarfs 221, 225–228, 230, 231, 233, 273, 325, 330, 362 Wideroe, R 204 Wien, W 132 Wien’s displacement law 132–133 Wilberforce, S 382 Wilkins, M 374 Wilkinson, D 302 Wilson, R 312 WMAP: see space telescopes winter solstice 4–5 Woese, C 383–384 Wollaston, W 128 Wolszczan, A 464 world model: see cosmological model Wren, C 105 Wright, T 237–240 Index X Xenocrates 32 x-rays 78, 133, 145, 176, 180, 231–233, 327–329, 330, 374, 390, CS Fig 20 Y Yang, S 464 year sidereal, tropical 27–28 Gregorian, Julian 28 Haab & Tzolkin 447 Yukawa, H 200–201 Young, T 125–127 Z Zeldovich, Ya 290, 323–324, 353 zenith 29, 81, 97 Zenon 292 Zweig, G 208 Zwicky, F 228–229, 325, 328 COLOR PLATES Fig The Very Large Telescope (VLT) of the European Southern Observatory in Chile is currently the largest optical ground based telescope It actually consists of four telescopes, each with a 8.2-m mirror, which can be used either separately or together (credit: ESO) Fig The Nanc¸ay radio telescope in France operates in the decimetric wavelength range, studying a wide range of subjects from comets and pulsars to galaxies and cosmology For example, it can measure the 21-cm line radiation emitted by the neutral hydrogen gas which is abundant in our Milky Way and in many other galaxies Courtesy of I Cognard, CNRS Fig The Hubble Space Telescope orbits the Earth at a height of 600 km above the atmosphere and can thus make sharper images than ordinary telescopes (credit: NASA) Fig The WMAP space observatory measured with a high precision the cosmic thermal background radiation, allowing cosmologists to study the geometry and composition of our universe The European Space Agency PLANCK observatory will complement and improve these observations This artist’s depiction shows the WMAP’s location a million miles from the Earth in the direction away from the Sun (credit: NASA) Fig An ultraviolet image of our Sun taken by the SOHO space observatory in 1999 Our Sun is an ordinary star, about five billion years old Despite short term activity such as the eruptive prominence shown, our Sun’s long stable phase of development has allowed life to exist on the Earth for a large fraction of its age The huge mass of the Sun (over 300 000 earth masses) holds its planetary system circling around it (credit: SOHO-EIT Consortium, ESA, NASA) Fig Valles Marineris (the Valleys of Mariner) on the Tharsis plateau in Mars This huge (200 km wide and 4,500 km long) canyon is a spectacular example of former geologic activity (credit: NASA) Fig A close view of a rough portion of the Martian landscape was obtained by the Spirit Mars Exploration Rover The nearby dark volcanic boulder is about 40 cm high (credit: NASA/JPLCaltech/Cornell/NMMNH) Fig On its way to Jupiter in 1993 the Galileo Probe took this photo of the asteroid 243 Ida orbiting about 440 million km from the Sun Being only about 50 km in length, Ida’s weak gravity cannot even pull it into a round shape making it an asteroid rather than a dwarf planet In this picture, we see also Ida’s small moon Dactyl (credit: NASA/JPL) Fig The comet Shoemaker- Levy broke into over 20 pieces before it collided with Jupiter in 1994 This Hubble Space Telescope image shows gigantic dark spots where four pieces of the comet penetrated the atmosphere Similar impacts like this may have affected the early environment of life on Earth and may be a hazard for life today (credit: HST Comet Team & NASA) Fig 10 Images of two different moons of Jupiter from the Galileo Probe show: a Mountains and volcanic calderas on the geologically active Io b The icy world of Europa where liquid water oceans beneath the ice may provide a habitat for life (credit: NASA/JPL) Fig 11 This 2004 Hubble Space Telescope combined visual and ultraviolet image shows a huge auroral display in Saturn’s southern polar region (credit: NASA, ESA, J Clarke (Boston University) & Z Levay (STScI)) Fig 12 This photograph of the Sagittarius star cloud illustrates the huge amounts of stars inhabiting our Milky Way galaxy All stars are not like our Sun, but may differ considerably e.g in mass, temperature, and luminosity In this picture you can easily discern red (cool), yellow (sun-like), and bluish (hot) stars (credit: Hubble Heritage Team (AURA/STScI/NASA/ESA)) Fig 13 The region of the Eagle nebula in the constellation Serpens, 7000 light-years away, offers striking scenes of cold gas and dust where new stars are actively born in the Milky Way Energy from massive, hot, and young stars works as sculptor carving ghostly shapes from interstellar matter This “tower” has a length of about 9.5 lightyears, roughly a million times the diameter of the Earth’s orbit around the Sun (credit: NASA, ESA, & The Hubble Heritage Team STScI/AURA) Fig 14 This beautiful planetary nebula (NGC 6751) in the constellation Aquila is a shell of gas ejected thousands of years ago from the hot star visible in the middle Such glowing nebulae tell about the forthcoming death of stars roughly similar as our Sun The “planetary” nebulae have actually nothing to with planets or planetary systems In fact, this nebula’s diameter is almost light year, 700 times the size of our Solar System (credit: NASA, The Hubble Heritage Team STScI/AURA) Fig 15 Extrasolar planetary system 55 Cancri as sketched on the basis of observations and compared with the Solar System It consists of five known planets on orbits around the central, sun-like star (credit: NASA) Fig 16 Artist’s view of the multitude of earth-like planets expected to be in our Milky Way, each individuals in their detailed surface structure, water cover, and atmosphere It is a great question of astrobiology, whether a fraction of them carry some kind of life (credit: NASA) Fig 17 Fig 21.15 Our neighboring large “island” in the universe, the Andromeda galaxy M31, and its small companion galaxies M32 and M110 This spiral galaxy, which can be dimly seen with naked eye, lies at a distance of 2.5 million light-years (credit: John Lanoue www.bedfordnights.com) Fig 18 The structure of the Local Group: The MilkyWay and the Andromeda galaxy, surrounded by their smaller companion galaxies Courtesy of Rami Rekola Fig 19 The spiral galaxy M81 is a member of a nearby galaxy group in the constellation Ursa Major It is about five times farther away than the Andromeda galaxy At this distance it recedes from us at a speed of about 250 km s−1 , participating in the expansion of the universe (credit: NASA, ESA & The Hubble Heritage Team STScI/AURA) Fig 20 Many spiral galaxies have a bar-like structure with the spiral arms starting out of its ends This beautiful barred spiral is called NGC1300 It is impressive to think that what we see as starlight and glowing gas is just a fraction of mass within a larger lump of invisible mysterious dark matter (credit: NASA, ESA, & The Hubble Heritage Team STScI/AURA) Fig 21 This rare system, known as IRAS 19115-2124 and dubbed “The Bird” or even “The Tinker Bell” by astronomers, consists of two large spiral galaxies and one irregular galaxy which are merging together Observations using an adaptive optics system on the Very Large Telescope (ESO) at near-infrared wavelengths revealed this dramatic cosmic collision The image combines nearinfrared data with optical images from the Hubble Space Telescope (credit: ESO & Henri Boffin and Petri V¨ais¨anen & Seppo Mattila) Fig 22 The supernova that exploded in 1604 (and was observed e.g by Kepler) left behind it a shell of gas expanding at a speed of 2,000 km s−1 , shown here in a composite picture based on different wavelengths from infrared to x-rays Located 13,000 light-years away in the constellation Ophiuchus, this was the last supernova thus far observed in our own Galaxy (credit: NASA, ESA/JPLCaltech/R.Sankrit & W Blair (John Hopkins University)) Fig 23 A supernova explosion in the outskirts of a galaxy called NGC 4526 Supernovae occur about once in a century in a typical galaxy Certain types of supernovae are “standard candles.” Their observations at very large distances have revealed that the expansion of the universe is accelerating due to a mysterious antigravitating “dark energy” (credit: NASA/ESA, The Hubble Key Project Team, and The High-Z Supernova Search Team) Fig 24 Our current view of the development of our universe during its about 14 billion years of existence starting from the mysterious Big Bang When the temperature decreased, during the first second various elementary particles including hydrogen nuclei (protons) were formed, through the first minutes helium nuclei were created, and about 400 000 years later first atoms were formed and the thermal background radiation started wandering in space During billions of years stars and galaxies were gathered by gravitation from the expanding cosmic matter (credit: NASA) Fig 25 An all-sky picture of the infant universe as observed in the thermal cosmic background radiation This is based on data gathered by the WMAP space observatory The effect of the motion of the Earth, moving in space at a speed of about 350 km s−1 , has been cleaned away from this map The 14 billion year old slight temperature fluctuations (shown as color differences) are caused by the seeds that grew to become the galaxies (credit: NASA/WMAP Science Team) Fig 26 An all-sky view of the local galaxy universe based on about 1.5 million galaxies from the 2MASS galaxy survey The MilkyWay is shown in the middle The redshifts (distances) of the galaxies are coded by color (the red ones are most distant) Some galaxies, galaxy clusters, and superclusters are identified in this picture where one can discern complex large scale structures Courtesy of Tom Jarrett (IPAC/Caltech) [...]... close the Orion, was worshipped in ancient Egypt The appearance of the “Dog Star” in the morning sky heralded the beginning of the flood of the river Nile Just across the band of the Milky Way there is Procyon, the brightest star of the Little Dog (Canis Minor) For today’s stargazers those brilliant points are material objects in space, and we wonder: How far away are they? What makes them shine? The. .. ascends higher in the sky The day when the sunrise and sunset points are farthest to the north in the horizon and the Sun ascends highest in the sky is the summer solstice (solstice meaning “Sun stand still” P Teerikorpi et al., The Evolving Universe and the Origin of Life c Springer Science+Business Media, LLC 2009 3 4 1 When Science Was Born Fig 1.1 Stonehenge is an impressive monument of Bronze Age... Pythagorean Theorem The area of the square drawn on the hypotenuse of a right-angled triangle is equal to the sum of the areas of the squares on the other two sides You may try to prove this ancient theorem – there are many ways to do it A=B+C C B True cosmic motions inhabit the world of ideas as “true velocities” and “true periods,” and these make themselves felt in the observed motions of celestial bodies,... (or their ratios), which were the only type of numbers known at the time, may measure everything in the world For example, they thought that a line is formed by a large number of points, like atoms put side by side, and hence the ratio of the lengths of any two line segments would always be rational It was a shock to find, using the very√theorem of Pythagoras, that the ratio of the diagonal and the. .. our feet Philolaus is said to have theorized that we cannot see the central fire, because the Earth always turns with the same half toward it (like the Moon does relative to the Earth) Pythagoras founded number theory and proved the famous theorem of Pythagoras about the areas of the squares drawn on the sides of a right-angled triangle Integer numbers were the basis of the Pythagorean worldview Those... summer in the eastern sky before dawn The day of each year when it was viewed the first time, the so-called heliacal rising above the horizon, marked the start of the calendar year in Egypt This very important event heralded the longed for flood of the Nile, on which agriculture and life depended The horizon was a fascinating thing for ancient people They viewed it as a sort of boundary of the world... Ionian Way of Thinking 9 astronomers observe the sky to understand what the celestial bodies are, how they are born and evolve (Fig 1.4) The Ionian Way of Thinking The seeds of our science were sowed on the western coast of Asia Minor, where the Ionian Greeks lived in their flourishing colonies In the seventh century BC Ionian cities, among them Miletus and Ephesus, were centers of Greek culture and economy... based on the time of birth appeared (among the Greeks) The astrologers noted that the planets followed the same general route as the Sun in the ecliptic, but now and then they slowed down, even stopped altogether and went back a few steps in the sky before again continuing their normal way from east to west This retrograde motion of the planets was a major feature that needed explanation both for the Greeks... events at the horizon (photograph by Harry Lehto) in Latin) Similarly, there is a day, the winter solstice, when the day is the shortest, and the sunrise happens closest to the south These and other points on the horizon had both practical and ritual significance For example, the ancient Hopi people, living in their pueblos in Arizona, used (and still use) the horizon with its sharp peaks and clefts... when the thin sickle of the growing Moon was first seen after sunset Nowadays, the solar calendar (which is consistent with the seasons) dominates everyday life, but the lunar calendar is still important for religious purposes Because of the yearly cycle of the Sun, different constellations are visible in the evening at different seasons The appearance of the sky today is almost the same as thousands of