Durham E-Theses

Total Page:16

File Type:pdf, Size:1020Kb

Durham E-Theses Durham E-Theses First visibility of the lunar crescent and other problems in historical astronomy. Fatoohi, Louay J. How to cite: Fatoohi, Louay J. (1998) First visibility of the lunar crescent and other problems in historical astronomy., Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/996/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk me91 In the name of Allah, the Gracious, the Merciful >° 9 43'' 0' eji e' e e> igo4 U61 J CO J: lic 6..ý v Lo ý , ý.,, "ý J ýs ýºý. ur ý,r11 Lýi is' ý9r ZU LZJE rju No disaster can befall on the earth or in your souls but it is in a book before We bring it into being; that is easy for Allah. In order that you may not grieve for what has escaped you, nor be exultant at what He has given you; and Allah does not love any prideful boaster. (The Holy Qur'an, 057: 022-023) Io 1, ýtý ; äýLm}I1ý I19 Li. Jea J1 ; ýý'=pLu9 dýýsa§ dýl doý419 stq ..4ný1 #a" t; aM May Allah send blessings on our Master whose quality, revelation, message, and wisdom are praised [Muhammad], and on his lineage and companions, and salute him with a perfect salutation First Visibility of the Lunar Crescent and Other Problems in Historical Astronomy The copyright of this thesis rests with the author. No quotation from it should be published without the written consent of the author and information derived from it should be acknowledged. by Louay J. Fatoohi July 1998 A thesis University submitted to the of Durham for the degree of Doctor of Philosophy ýý 11 x., res c5- JJ c5`. ccJ ýjJ JI tl oJJ ýI11wig .;, ýI j ii .s, ý. v _11 ý,:,Iýý511 ý, Ix11d. 9. ý11 ýLý. ýý1.9]Iý, ý, ýý For My Sufi Master and spiritual guide Shaikh Muhammad al-Casnazani al-Husseini The Master of Tariqa `Aliyyah Qadiriyyah Casnazaniyyah A Abstract The first part of this dissertation investigates methods of predicting the first visibility of the lunar crescent: an astronomical problem that has attracted the interest of man since ancient times. Many early nations used lunar calendars, the months of which began on the evening of the first sighting of the lunar crescent after conjunction. In modern times, the resolution of this is astronomical problem of special importance - both for historians who need to determine ancient dates exactly and for Muslims around the world, whose religious calendar is lunar. The interest in this matter over the centuries has resulted in the appearance of a number of solutions by a variety of authors for predicting the first visibility of the lunar crescent. The purpose of the first part of this dissertation is to assess the accuracy of these prediction models using ancient, mediaeval and modern observational data and to explore possible improvement. The study concludes that the concept of a "zone of uncertainty" must be incorporated into any lunar visibility criterion; it further applies this conclusion to the widely used modern criterion of true lunar altitude versus azimuthal difference between the sun and moon. The observational data show that developing a "zone of uncertainty" in this particular criterion yields the best results of all. The second part of the dissertation is an investigation of six problems in historical astronomy. These are: (i) assessing the accuracy of solar eclipse observations made by Jesuit astronomers in China; (ii) assessing the accuracy of lunar eclipse observations made by Jesuit astronomers in China; (iii) dating the solar eclipse of Thales; (iv) determining the modern equivalent of the Babylonian angular units of measurement; (v) dating the eclipses of Thucydides; and (vi) dating the solar eclipse of Plutarch. All papers have been published or are currently in press. -i- Contents Abstract i Contents 11 Part 1. The First Visibility of the Lunar Crescent 1 Introduction 1 1.1 Overview 1 1.2 Literature Review 2 1.3 Abbreviations 3 1.4 Acknowledgement 4 2 The Observational Data 5 2.1 The Babylonian "Astronomical Diaries" 5 2.2 Conversion of Dates from the Babylonian to the Julian Calendar 9 2.3 The Babylonian Data 10 2.4 Determination of the Julian Dates of First Visibility of the Lunar Crescent for 12 Babylonian Observations 2.5 The Medieval Data 19 2.6 The Modern Data 24 3 The Computations 26 3.1 Computation of the Dates of New Moons 26 3.2 Computation of Solar, Lunar and Other Astronomical Parameters 28 3.3 Computation of Planetary Coordinates 30 3.4 Conversion of the Babylonian Dates into Julian Dates 31 3.5 Results of Computations 33 -11- 4 The Babylonian Criterion of First Visibility of the Lunar Crescent 54 5 The Islamic Calendar and First Visibility of the Lunar Crescent 61 62 5.1 Characteristics of the Islamic Calendar 65 5.2 The Controversy of Crescent Visibility in the Islamic World 69 5.3 Versions of the Islamic Calendar 6 The Criterion of First Visibility Of the Lunar Crescent in the 79 Medieval and Later Arab World 6.1 The (Xm, AX) Criterion of al-Khawarizmi 79 6.2 The (Xm, AX) Criterion of al-Qallas 82 6.3 The (Xm, AX) Criterion of al-Lathiqi 84 6.4 The (Xs, AX, ß) Criterion of al- Sanjufini 85 6.5 The (S, L, Vm) Criterion of ibn Yunus 87 6.6 The (S, L) Criteria 90 6.7 Maimonides' (Xm, AX, S) Criterion 91 7 Modern Criteria of First Visibility of the Lunar Crescent 94 7.1 The Danjon Visibility Limit 94 7.2 The Lunar Altitude-Azimuthal Difference Criterion 102 7.3 Bruin's Physical Criterion 107 7.4 Ilyas' CompositeCriterion 111 7.5 The Lunar Age Criterion 114 7.6 The Moonset Lagtime Criterion 117 7.7 Schaefer's Criterion 120 7.8 Yallop's Empirical Criterion 121 8 Discussion and Conclusion 127 Bibliography 137 -111- Part 2. Problems in Historical Astronomy 1 Accuracy of Solar Eclipse Observations made by Jesuit Astronomers in China. (published paper) 2 Accuracy of Lunar Eclipse Observations made by Jesuit Astronomers in China. (published paper) 3 Thales's Prediction of a Solar Eclipse. (published paper) 4 Angular Measurements in Babylonian Astronomy. (paper in press) 5 The Eclipses Recorded by Thucydides. (paper in press) 6 The Total Solar Eclipse Recorded by Plutarch. (paper in press) Additional Published Studies Referenced in this Dissertation 1 Lunar Eclipse Times Recorded in Babylonian History. 2 Accuracy of Early Estimates of Lunar Eclipse Magnitude. 3 The Babylonian Unit of Time. -lv- Part One The First Visibility of the Lunar Crescent 1 Introduction The problem of predicting the first visibility of the lunar crescent attracted attention throughout history from many nations who used lunar calendars to regulate their activities. The in date back oldest available records which reveal organised interest this matter almost three first lunar thousand years to the time of the Babylonians. Predicting the visibility of the largely because crescent received great interest from medieval Muslim astronomers, timings of beginning fasting Ramadhan religious practices in Islam - such as the and end of the month of - are determined by a lunar calendar. has In modern times, scientific interest in understanding the visibility of the lunar crescent dates historical been motivated mainly by two factors: (i) the need to accurately convert of records of nations that used the lunar calendar; (ii) the need of Muslims to ascertain when the hence lunar crescent may be visible for the first time after conjunction with the sun - and to following how look for it, and also to know when it cannot be seen. The quotation expresses first lunar one of the contemporary investigators of the question of visibility of the crescent described its present cultural and religious significance: With roughly lx109 people of the Islamic faith following the Islamic calendar, this problem is likely to be the one (non-trivial) problem in astronomy that has the greatest impact on our modern world (Schaefer, 1996: 759). 1.1 Overview Predicting the earliest visibility of the lunar crescent after conjunction is a matter of factors considerable complexity. It is a problem where astronomical, atmospheric and human (especially visual acuity) are all at work. The fact that even modern astronomers cannot agree on the best criterion for determining the first visibility of the lunar crescent only attests to the complex nature of this matter. 5 -i- Throughout history, each attempt to put forward a criterion has followed either an empirical or theoretical approach. The empirical approach, which is more frequently employed, is based on analysing a collection of observational data and then formulating a criterion that best fits the observations. On the other hand, the theoretical approach is embodied in attempts to resolve the problem through considering the various factors affecting crescent visibility and designing a descriptive mathematical model. While the Babylonian criterion was empirical, the Arab astronomers took mostly a theoretical approach.
Recommended publications
  • Astronomie in Theorie Und Praxis 8. Auflage in Zwei Bänden Erik Wischnewski
    Astronomie in Theorie und Praxis 8. Auflage in zwei Bänden Erik Wischnewski Inhaltsverzeichnis 1 Beobachtungen mit bloßem Auge 37 Motivation 37 Hilfsmittel 38 Drehbare Sternkarte Bücher und Atlanten Kataloge Planetariumssoftware Elektronischer Almanach Sternkarten 39 2 Atmosphäre der Erde 49 Aufbau 49 Atmosphärische Fenster 51 Warum der Himmel blau ist? 52 Extinktion 52 Extinktionsgleichung Photometrie Refraktion 55 Szintillationsrauschen 56 Angaben zur Beobachtung 57 Durchsicht Himmelshelligkeit Luftunruhe Beispiel einer Notiz Taupunkt 59 Solar-terrestrische Beziehungen 60 Klassifizierung der Flares Korrelation zur Fleckenrelativzahl Luftleuchten 62 Polarlichter 63 Nachtleuchtende Wolken 64 Haloerscheinungen 67 Formen Häufigkeit Beobachtung Photographie Grüner Strahl 69 Zodiakallicht 71 Dämmerung 72 Definition Purpurlicht Gegendämmerung Venusgürtel Erdschattenbogen 3 Optische Teleskope 75 Fernrohrtypen 76 Refraktoren Reflektoren Fokus Optische Fehler 82 Farbfehler Kugelgestaltsfehler Bildfeldwölbung Koma Astigmatismus Verzeichnung Bildverzerrungen Helligkeitsinhomogenität Objektive 86 Linsenobjektive Spiegelobjektive Vergütung Optische Qualitätsprüfung RC-Wert RGB-Chromasietest Okulare 97 Zusatzoptiken 100 Barlow-Linse Shapley-Linse Flattener Spezialokulare Spektroskopie Herschel-Prisma Fabry-Pérot-Interferometer Vergrößerung 103 Welche Vergrößerung ist die Beste? Blickfeld 105 Lichtstärke 106 Kontrast Dämmerungszahl Auflösungsvermögen 108 Strehl-Zahl Luftunruhe (Seeing) 112 Tubusseeing Kuppelseeing Gebäudeseeing Montierungen 113 Nachführfehler
    [Show full text]
  • Mathématiques Et Espace
    Atelier disciplinaire AD 5 Mathématiques et Espace Anne-Cécile DHERS, Education Nationale (mathématiques) Peggy THILLET, Education Nationale (mathématiques) Yann BARSAMIAN, Education Nationale (mathématiques) Olivier BONNETON, Sciences - U (mathématiques) Cahier d'activités Activité 1 : L'HORIZON TERRESTRE ET SPATIAL Activité 2 : DENOMBREMENT D'ETOILES DANS LE CIEL ET L'UNIVERS Activité 3 : D'HIPPARCOS A BENFORD Activité 4 : OBSERVATION STATISTIQUE DES CRATERES LUNAIRES Activité 5 : DIAMETRE DES CRATERES D'IMPACT Activité 6 : LOI DE TITIUS-BODE Activité 7 : MODELISER UNE CONSTELLATION EN 3D Crédits photo : NASA / CNES L'HORIZON TERRESTRE ET SPATIAL (3 ème / 2 nde ) __________________________________________________ OBJECTIF : Détermination de la ligne d'horizon à une altitude donnée. COMPETENCES : ● Utilisation du théorème de Pythagore ● Utilisation de Google Earth pour évaluer des distances à vol d'oiseau ● Recherche personnelle de données REALISATION : Il s'agit ici de mettre en application le théorème de Pythagore mais avec une vision terrestre dans un premier temps suite à un questionnement de l'élève puis dans un second temps de réutiliser la même démarche dans le cadre spatial de la visibilité d'un satellite. Fiche élève ____________________________________________________________________________ 1. Victor Hugo a écrit dans Les Châtiments : "Les horizons aux horizons succèdent […] : on avance toujours, on n’arrive jamais ". Face à la mer, vous voyez l'horizon à perte de vue. Mais "est-ce loin, l'horizon ?". D'après toi, jusqu'à quelle distance peux-tu voir si le temps est clair ? Réponse 1 : " Sans instrument, je peux voir jusqu'à .................. km " Réponse 2 : " Avec une paire de jumelles, je peux voir jusqu'à ............... km " 2. Nous allons maintenant calculer à l'aide du théorème de Pythagore la ligne d'horizon pour une hauteur H donnée.
    [Show full text]
  • Explore the Universe Observing Certificate Second Edition
    RASC Observing Committee Explore the Universe Observing Certificate Second Edition Explore the Universe Observing Certificate Welcome to the Explore the Universe Observing Certificate Program. This program is designed to provide the observer with a well-rounded introduction to the night sky visible from North America. Using this observing program is an excellent way to gain knowledge and experience in astronomy. Experienced observers find that a planned observing session results in a more satisfying and interesting experience. This program will help introduce you to amateur astronomy and prepare you for other more challenging certificate programs such as the Messier and Finest NGC. The program covers the full range of astronomical objects. Here is a summary: Observing Objective Requirement Available Constellations and Bright Stars 12 24 The Moon 16 32 Solar System 5 10 Deep Sky Objects 12 24 Double Stars 10 20 Total 55 110 In each category a choice of objects is provided so that you can begin the certificate at any time of the year. In order to receive your certificate you need to observe a total of 55 of the 110 objects available. Here is a summary of some of the abbreviations used in this program Instrument V – Visual (unaided eye) B – Binocular T – Telescope V/B - Visual/Binocular B/T - Binocular/Telescope Season Season when the object can be best seen in the evening sky between dusk. and midnight. Objects may also be seen in other seasons. Description Brief description of the target object, its common name and other details. Cons Constellation where object can be found (if applicable) BOG Ref Refers to corresponding references in the RASC’s The Beginner’s Observing Guide highlighting this object.
    [Show full text]
  • Young Super-Neptune Offers Clues to the Origin of Close-In Exoplanet 21 June 2016, by Rebecca Johnson
    Young super-Neptune offers clues to the origin of close-in exoplanet 21 June 2016, by Rebecca Johnson planets in the same planetary system, or with more distant stars. These scenarios can be tested observationally by searching for young planets and studying their orbits. If the close-in population formed in place or migrated in through interactions with the natal disk, they reach their final orbital distances early on and will be found close in at young ages. In comparison, migrating a planet inward through interactions with other planets or more distant stars is effective on much longer timescales. If the latter processes dominate, planets will not be found close to their K2-33 b, shown in this illustration, is one of the youngest stars when they are young. exoplanets detected to date. It makes a complete orbit around its star in about five days. These two characteristics combined provide exciting new directions for planet-formation theories. K2-33b could have formed on a farther out orbit and quickly migrated inward. Alternatively, it could have formed in situ, or in place. Credit: NASA/JPL-Caltech A team of astronomers has confirmed the existence of a young planet, only 11 million years old, that orbits very close to its star (at 0.05 AU), with an orbital period of 5.4 days. Approximately 5 times the size of the Earth, the new planet is a "super-Neptune" and the youngest such planet This image shows the K2-33 system, and its planet known. The discovery lends unique insights into K2-33b, compared to our own solar system.
    [Show full text]
  • Livre-Ovni.Pdf
    UN MONDE BIZARRE Le livre des étranges Objets Volants Non Identifiés Chapitre 1 Paranormal Le paranormal est un terme utilisé pour qualifier un en- mé n'est pas considéré comme paranormal par les semble de phénomènes dont les causes ou mécanismes neuroscientifiques) ; ne sont apparemment pas explicables par des lois scien- tifiques établies. Le préfixe « para » désignant quelque • Les différents moyens de communication avec les chose qui est à côté de la norme, la norme étant ici le morts : naturels (médiumnité, nécromancie) ou ar- consensus scientifique d'une époque. Un phénomène est tificiels (la transcommunication instrumentale telle qualifié de paranormal lorsqu'il ne semble pas pouvoir que les voix électroniques); être expliqué par les lois naturelles connues, laissant ain- si le champ libre à de nouvelles recherches empiriques, à • Les apparitions de l'au-delà (fantômes, revenants, des interprétations, à des suppositions et à l'imaginaire. ectoplasmes, poltergeists, etc.) ; Les initiateurs de la parapsychologie se sont donné comme objectif d'étudier d'une manière scientifique • la cryptozoologie (qui étudie l'existence d'espèce in- ce qu'ils considèrent comme des perceptions extra- connues) : classification assez injuste, car l'objet de sensorielles et de la psychokinèse. Malgré l'existence de la cryptozoologie est moins de cultiver les mythes laboratoires de parapsychologie dans certaines universi- que de chercher s’il y a ou non une espèce animale tés, notamment en Grande-Bretagne, le paranormal est inconnue réelle derrière une légende ; généralement considéré comme un sujet d'étude peu sé- rieux. Il est en revanche parfois associé a des activités • Le phénomène ovni et ses dérivés (cercle de culture).
    [Show full text]
  • A Spectroscopic Study of the Scorpio-Centaurus Association
    PranllQa. Vol. 7, No.3, 1976, pp 160-\ 80. © Prmted in India. A spectroscopic study of the Scorpio-Centaurus association R RAJAMOHAN Indian Institute of Astrophysics, Bangaiore 560034 MS recehcl 5 April 1976 • I' Abstract. Rotational .... elocities as well as hydrogen and he Jlum Ine I'ntensities of .' have been one hundred. and twelve members of the Scorplo-Centaurus aSSOclatlO~ . b h derived. For stars with M~ < 0'0, the distribution of rotational velocitieS of °lt are SJlnlar the upper Scorplus subgroup and the upper Centaurus-Lupus Su b grou P 1 . I and closely resemble those of the field stars. Stars with M, > O' 0, all of w lie 1 are found in th.e dense upper Scorpius region, rotate much faster than their counter­ parts amongst field stars, the Pleiades and Alpha-Persei cluster members. The measured equivalent width of H'Y for 77 stars provide a distance nlOd~\U~ of 6·0±0·09 magnitudes for the association. Evolutionary effects in the del1;~e hydrogen line intensities are found between the two subgroups. The hydrogen- me intensities at all spectral types in the upper Centaurus-Lupus subgroup are systematically smaller than thOse of members in the upper Scorpius subgrouP. Analysis of high dispersion spectra of five members of the association y.ield a helium abundance of Nae(N. = 0·096 ± 0 004. Along with data available In the literature, the mean helium abundance of thirteen stars of this association is found to be 0·098 :±: O· 004 by number. For the two main subgroups of this association, we deflve a value of 0 105 ± 0 001 for the upper Centaurus-Lupus group from three stars and 0·096 ± 0·005 for the upper Scorpius group from ten stars.
    [Show full text]
  • Educator's Guide: Orion
    Legends of the Night Sky Orion Educator’s Guide Grades K - 8 Written By: Dr. Phil Wymer, Ph.D. & Art Klinger Legends of the Night Sky: Orion Educator’s Guide Table of Contents Introduction………………………………………………………………....3 Constellations; General Overview……………………………………..4 Orion…………………………………………………………………………..22 Scorpius……………………………………………………………………….36 Canis Major…………………………………………………………………..45 Canis Minor…………………………………………………………………..52 Lesson Plans………………………………………………………………….56 Coloring Book…………………………………………………………………….….57 Hand Angles……………………………………………………………………….…64 Constellation Research..…………………………………………………….……71 When and Where to View Orion…………………………………….……..…77 Angles For Locating Orion..…………………………………………...……….78 Overhead Projector Punch Out of Orion……………………………………82 Where on Earth is: Thrace, Lemnos, and Crete?.............................83 Appendix………………………………………………………………………86 Copyright©2003, Audio Visual Imagineering, Inc. 2 Legends of the Night Sky: Orion Educator’s Guide Introduction It is our belief that “Legends of the Night sky: Orion” is the best multi-grade (K – 8), multi-disciplinary education package on the market today. It consists of a humorous 24-minute show and educator’s package. The Orion Educator’s Guide is designed for Planetarians, Teachers, and parents. The information is researched, organized, and laid out so that the educator need not spend hours coming up with lesson plans or labs. This has already been accomplished by certified educators. The guide is written to alleviate the fear of space and the night sky (that many elementary and middle school teachers have) when it comes to that section of the science lesson plan. It is an excellent tool that allows the parents to be a part of the learning experience. The guide is devised in such a way that there are plenty of visuals to assist the educator and student in finding the Winter constellations.
    [Show full text]
  • Fy10 Budget by Program
    AURA/NOAO FISCAL YEAR ANNUAL REPORT FY 2010 Revised Submitted to the National Science Foundation March 16, 2011 This image, aimed toward the southern celestial pole atop the CTIO Blanco 4-m telescope, shows the Large and Small Magellanic Clouds, the Milky Way (Carinae Region) and the Coal Sack (dark area, close to the Southern Crux). The 33 “written” on the Schmidt Telescope dome using a green laser pointer during the two-minute exposure commemorates the rescue effort of 33 miners trapped for 69 days almost 700 m underground in the San Jose mine in northern Chile. The image was taken while the rescue was in progress on 13 October 2010, at 3:30 am Chilean Daylight Saving time. Image Credit: Arturo Gomez/CTIO/NOAO/AURA/NSF National Optical Astronomy Observatory Fiscal Year Annual Report for FY 2010 Revised (October 1, 2009 – September 30, 2010) Submitted to the National Science Foundation Pursuant to Cooperative Support Agreement No. AST-0950945 March 16, 2011 Table of Contents MISSION SYNOPSIS ............................................................................................................ IV 1 EXECUTIVE SUMMARY ................................................................................................ 1 2 NOAO ACCOMPLISHMENTS ....................................................................................... 2 2.1 Achievements ..................................................................................................... 2 2.2 Status of Vision and Goals ................................................................................
    [Show full text]
  • INAUGURAL – DISSERTATION Dipl.-Phys. Alexander A. Schegerer
    INAUGURAL – DISSERTATION zur Erlangung der Doktorwurde¨ der Naturwissenschaftlich-Mathematischen Gesamtfakult¨at der Ruprecht - Karls - Universit¨at Heidelberg vorgelegt von Dipl.-Phys. Alexander A. Schegerer, geboren in Kaufbeuren Tag der mundlichen¨ Prufung:¨ 17. Oktober 2007 II Struktur- und Staubentwicklung in zirkumstellaren Scheiben um T Tauri-Sterne Analyse und Modellierung hochaufl¨osender Beobachtungen in verschiedenen Wellenl¨angenbereichen Gutachter: Prof. Dr. Thomas Henning Prof. Dr. Wolfgang Duschl IV Meinen Eltern, Maria-Christa und Wolfgang Schegerer, gewidmet. VI Thema Im Zentrum dieser Doktorarbeit steht die Untersuchung der inneren Strukturen zirkumstella- rer Scheiben um T Tauri-Sterne sowie die Analyse zirkumstellarer Staub- und Eisteilchen und ihres Einflusses auf die Scheibenstruktur. Unter Zuhilfenahme von theoretisch berechneten Vergleichsspektren gibt der Verlauf der 10 µm-Emissionsbande in den Spektren junger stellarer Objekte Hinweise auf den Entwick- lungsgrad von Silikatstaub. Die Silikatbanden von 27 T Tauri-Objekten werden analysiert, um nach potentiell vorliegenden Korrelationen zwischen der Silikatstaubzusammensetzung und den stellaren Eigenschaften zu suchen. Analog erlaubt das Absorptionsband bei 3 µm, das dem Wassereis zugeschrieben wird, eine Untersuchung der Entwicklung von Eisk¨ornern in jungen stellaren Objekten. Erstmals ist es gelungen, kristallines Wassereis im Spektrum eines T Tauri-Objektes nachzuweisen. Unser wichtigstes Hilfsmittel zur Analyse der Temperatur- und Dichtestrukturen zirkum- stellarer
    [Show full text]
  • La Photosynthèse Serait Apparue Chez Certains Organismes Primitifs Entre 2.800 Et -2.400 Millions D’Années Si L’On En Croit Certaines Archives Géologiques Terrestres
    La photosynthèse serait apparue chez certains organismes primitifs entre 2.800 et -2.400 millions d’années si l’on en croit certaines archives géologiques terrestres. Mais certains la font remonter bien plus tôt en faisant l’hypothèse que les stromatolites que l’on retrouve dans des couches plus anciennes encore sont bien le produit d’une activité biologique. Actuellement, nous n’en sommes sûrs que pour ceux datant de -2.724 millions d’années mais des stromatolites existaient déjà sur Terre il y a 3,5 milliards d’années environ. Quoiqu'il en soit, une certitude demeure, concernant les immenses dépôts de fer du bassin de Hamersley en Australie. Ils datent de l’époque du Sidérien alors que la surface des continents était devenue suffisamment importante pour que se forment des mers peu profondes entourées de grande plates-formes continentales. Les conditions étaient remplies pour que de grands tapis de bactéries construisent des stromatolites en quantités importantes et dégagent massivement de l’oxygène par photosynthèse. Ce gaz corrosif a alors pu oxyder le fer en solution dans les océans et entraîner sa précipitation sous forme d’hydroxyde de fer, de carbonate de fer, de silicate ou de sulfures, selon des variations de l’acidité et du degré d’oxydoréduction de l’eau de mer. C’est ce qu’on appelle la Grande oxydation ou la Catastrophe de l’oxygène. Vers -1.900 millions d’années, la presque totalité du fer présent dans les océans avait précipité et il se retrouve aujourd’hui dans les grands gisements de minerai mondiaux tels que ceux de Hamersley.
    [Show full text]
  • September 2020 BRAS Newsletter
    A Neowise Comet 2020, photo by Ralf Rohner of Skypointer Photography Monthly Meeting September 14th at 7:00 PM, via Jitsi (Monthly meetings are on 2nd Mondays at Highland Road Park Observatory, temporarily during quarantine at meet.jit.si/BRASMeets). GUEST SPEAKER: NASA Michoud Assembly Facility Director, Robert Champion What's In This Issue? President’s Message Secretary's Summary Business Meeting Minutes Outreach Report Asteroid and Comet News Light Pollution Committee Report Globe at Night Member’s Corner –My Quest For A Dark Place, by Chris Carlton Astro-Photos by BRAS Members Messages from the HRPO REMOTE DISCUSSION Solar Viewing Plus Night Mercurian Elongation Spooky Sensation Great Martian Opposition Observing Notes: Aquila – The Eagle Like this newsletter? See PAST ISSUES online back to 2009 Visit us on Facebook – Baton Rouge Astronomical Society Baton Rouge Astronomical Society Newsletter, Night Visions Page 2 of 27 September 2020 President’s Message Welcome to September. You may have noticed that this newsletter is showing up a little bit later than usual, and it’s for good reason: release of the newsletter will now happen after the monthly business meeting so that we can have a chance to keep everybody up to date on the latest information. Sometimes, this will mean the newsletter shows up a couple of days late. But, the upshot is that you’ll now be able to see what we discussed at the recent business meeting and have time to digest it before our general meeting in case you want to give some feedback. Now that we’re on the new format, business meetings (and the oft neglected Light Pollution Committee Meeting), are going to start being open to all members of the club again by simply joining up in the respective chat rooms the Wednesday before the first Monday of the month—which I encourage people to do, especially if you have some ideas you want to see the club put into action.
    [Show full text]
  • Instrumental Methods for Professional and Amateur
    Instrumental Methods for Professional and Amateur Collaborations in Planetary Astronomy Olivier Mousis, Ricardo Hueso, Jean-Philippe Beaulieu, Sylvain Bouley, Benoît Carry, Francois Colas, Alain Klotz, Christophe Pellier, Jean-Marc Petit, Philippe Rousselot, et al. To cite this version: Olivier Mousis, Ricardo Hueso, Jean-Philippe Beaulieu, Sylvain Bouley, Benoît Carry, et al.. Instru- mental Methods for Professional and Amateur Collaborations in Planetary Astronomy. Experimental Astronomy, Springer Link, 2014, 38 (1-2), pp.91-191. 10.1007/s10686-014-9379-0. hal-00833466 HAL Id: hal-00833466 https://hal.archives-ouvertes.fr/hal-00833466 Submitted on 3 Jun 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. Instrumental Methods for Professional and Amateur Collaborations in Planetary Astronomy O. Mousis, R. Hueso, J.-P. Beaulieu, S. Bouley, B. Carry, F. Colas, A. Klotz, C. Pellier, J.-M. Petit, P. Rousselot, M. Ali-Dib, W. Beisker, M. Birlan, C. Buil, A. Delsanti, E. Frappa, H. B. Hammel, A.-C. Levasseur-Regourd, G. S. Orton, A. Sanchez-Lavega,´ A. Santerne, P. Tanga, J. Vaubaillon, B. Zanda, D. Baratoux, T. Bohm,¨ V. Boudon, A. Bouquet, L. Buzzi, J.-L. Dauvergne, A.
    [Show full text]