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Science (from Latin scientia 'knowledge') is a systematic enterprise that builds and organizes knowledge in the form of testable explanations and predictions about the universe.

The earliest roots of science can be traced to Ancient Egypt and Mesopotamia in around 3000 to 1200 BCE. Their contributions to mathematics, astronomy, and medicine entered and shaped Greek natural philosophy of classical antiquity, whereby formal attempts were made to provide explanations of events in the physical world based on natural causes. After the fall of the Western Roman Empire, knowledge of Greek conceptions of the world deteriorated in Western Europe during the early centuries (400 to 1000 CE) of the Middle Ages, but was preserved in the Muslim world during the Islamic Golden Age. The recovery and assimilation of Greek works and Islamic inquiries into Western Europe from the 10th to 13th century revived "natural philosophy", which was later transformed by the Scientific Revolution that began in the 16th century as new ideas and discoveries departed from previous Greek conceptions and traditions. The scientific method soon played a greater role in knowledge creation and it was not until the 19th century that many of the institutional and professional features of science began to take shape; along with the changing of "natural philosophy" to "natural science."

Modern science is typically divided into three major branches that consist of the natural sciences (e.g., biology, chemistry, and physics), which study nature in the broadest sense; the social sciences (e.g., economics, psychology, and sociology), which study individuals and societies; and the formal sciences (e.g., logic, mathematics, and theoretical computer science), which deal with symbols governed by rules. There is disagreement, however, on whether the formal sciences actually constitute a science as they do not rely on empirical evidence. Disciplines that use existing scientific knowledge for practical purposes, such as engineering and medicine, are described as applied sciences.

New knowledge in science is advanced by research from scientists who are motivated by curiosity about the world and a desire to solve problems. Contemporary scientific research is highly collaborative and is usually done by teams in academic and research institutions, government agencies, and companies. The practical impact of their work has led to the emergence of science policies that seek to influence the scientific enterprise by prioritizing the development of commercial products, armaments, health care, public infrastructure, and environmental protection. (Full article...)

Featured article -

Cscr-featured.png  Featured articles are displayed here, which represent some of the best content on English Wikipedia.

Selected image

A Tesla coil lightning simulator
Credit: Fir0002
A Tesla coil is a category of disruptive discharge transformer coils, named after their inventor, Nikola Tesla. Tesla coils are composed of coupled resonant electric circuits. Nikola Tesla actually experimented with a large variety of coils and configurations, so it is difficult to describe a specific mode of construction that will meet the wants of those who ask about "Tesla" coils. "Early coils" and "later coils" vary in configuration and setup. Tesla coils in general are very popular devices among high-voltage enthusiasts.

Selected biography

Claudius Galenus of Pergamum
Claudius Galenus of Pergamum (129-200 AD), better known in English as Galen, was an ancient Greek physician. His views dominated European medicine for over a thousand years. From the modern viewpoint, Galen's theories were partially correct and partially flawed: he demonstrated that arteries carry blood rather than air, and conducted the first studies of nerve, brain, and heart function. He also argued that the mind was in the brain, not in the heart as Aristotle had claimed.

However, much of Galen's understanding is flawed from the modern point of view. For example, he did not recognize blood circulation and thought that venous and arterial systems were separate. This view did not change until William Harvey's work in the 17th century.

More did you know...


  • ...that silica aerogel (pictured) holds 15 entries in the Guinness Book of Records for material properties, including best insulator and lowest-density solid?
  • ...that acoustic levitation is a method for suspending matter in a fluid by using acoustic radiation pressure from intense sound waves in the medium?
  • ...that the genus Entomocorus includes a catfish species that lives only one year?
  • ...that a successful experimental system must be stable and reproducible enough for scientists to make sense of the system's behavior, but unpredictable enough that it can produce useful results?
  • ...that Abbott Lawrence Rotch established the Blue Hill Meteorological Observatory in 1885, which maintains the longest-running meteorological record of any observation site in the United States?

Topics and categories

See the portal's Topics and categories page for a comprehensive overview.

Science News

4 April 2022 – Discoveries of exoplanets
Astronomers announce the discovery of K2-2016-BLG-0005Lb, an exoplanet that is said to resemble Jupiter. The discovery was made using the now-retired Kepler space telescope. (ScienceAlert)
31 March 2022 –
Scientists sequence the complete human genome for the first time, more than three decades after the Human Genome Project was first commenced. (CNN)
30 March 2022 –
The Hubble Space Telescope observes the most distant single star ever. The star, named Earendel by astronomers, is 28 billion light-years away. It is the farthest detection of a star, dating back 900 million years after the Big Bang. This discovery surpasses Hubble's record from 2018, when it discovered a star that existed when the universe was roughly four billion years old. (CNN)
21 March 2022 – Discoveries of exoplanets
NASA announces that they have discovered their 5000th exoplanet since 1992, when astronomers Aleksander Wolszczan and Dale Frail announced the discovery of two exoplanets orbiting PSR B1257+12. (Science News)
7 March 2022 – Russo-Ukrainian War
The International Atomic Energy Agency confirms that the Kharkiv Institute of Physics and Technology in Kharkiv, which holds a neutron generator, has been destroyed by Russian shelling. The IAEA says that no radiation release has been detected from the facility, which housed a "small inventory of radioactive material". (Bloomberg)
3 March 2022 – 2022 in archosaur paleontology
A new research published in the Journal of Vertebrate Paleontology shows that the stegosaur Bashanosaurus, also known as the Bashanosaurus primitivus, is the oldest dinosaur species to be discovered in Asia. (Phys.org)

General images -

The following are images from various science-related articles on Wikipedia.



Activities Culture Geography Health History Mathematics Nature People Philosophy Religion Society Technology Random portal

Media files used on this page

Su Song Star Map 1.JPG
This is a star map for the celestial globe of Su Song (1020-1101), a Chinese scientist and mechanical engineer of the Song Dynasty (960-1279). It was first published in the year 1092, in Su's book known as the Xin Yi Xiang Fa Yao (Wade-Giles: Hsin Yi Hsiang Fa Yao). On this star map there are 14 xiu (lunar mansions) on Mercator's projection. The equator is represented by the horizontal straight line running through the star chart, while the ecliptic curves above it. Note the unequal breadth of the lunar mansions on the map.

Su Song's star maps had the hour circles between the xiu (lunar mansions) forming the astronomical meridians, with stars marked in quasi-orthomorphic cylindrical projection on each side of the equator, and thus was in accordance to their north polar distances. Not until the work of Gerard Mercator in 1569 was a celestial map of this projection created in the Western world (Needham, Volume 4, Part 3, 569).

This picture appears on page 277 of Joseph Needham's book Science and Civilization in China: Volume 3, Mathematics and the Sciences of the Heavens and the Earth.
Portrait of Johannes Kepler.
Wegener Expedition-1930 008.jpg
Photograph of the German expedition and overwintering in Greenland
Diagram showing the position of the pancreas CRUK 356.svg
Author/Creator: Cancer Research UK, Licence: CC BY-SA 4.0
Diagram showing the position of the pancreas.
Boyle air pump.jpg
Drawing of Robert Boyle's air pump
Author/Creator: Walkerma, Licence: CC BY-SA 3.0
Senior undergraduate student Jon Diamond pours a liquid from a graduated cylinder.
Portrait of Isaac Newton (1642-1727). This is a copy of a painting by Sir Godfrey Kneller (1689).
Author/Creator: Isaac Newton, Licence: CC BY-SA 2.0

Sir Isaac Newton's own first edition copy of his Philosophiae Naturalis Principia Mathematica with his handwritten corrections for the second edition.

The first edition was published under the imprint of Samuel Pepys who was president of the Royal Society. By the time of the second edition, Newton himself had become president of the Royal Society, as noted in his corrections.

It has been digitised by Cambridge University Library and can be seen in the Cambridge Digital Library [1] along with other original works by Isaac Newton [2].

The book can be seen in the Wren Library of Trinity College, Cambridge.
Linecons big-star.svg
Author/Creator: Designmodo http://www.designmodo.com/, Licence: CC BY 3.0
Linecons by Designmodo
Gilbert De Magnete Illo044.jpg

Illustration from De Magnete, etc. by William Gilbert (1600, translated 1900), showing

iron wires standing on a terrella
Author/Creator: Casliber, Licence: CC BY-SA 4.0
Pending confirmation - I think these are Pacific blue-eyes (Pseudomugil signifer)
Author/Creator: Users CanadianCaesar, Protarion, Cool Cat, Harrisonmetz, Alkivar, Jon Harald Søby, Optimager, CyberSkull, ClockworkSoul on en.wikipedia, Licence: LGPL

Shrunken and colored version created for ClockworkSoul's Coffee Roll template theme.


part of the featured stars series

if anyone is interested in the original vector/3d files you may contact en:User:Avsa.
Sirocco full length portrait.jpg
Author/Creator: Department of Conservation, Licence: CC BY 2.0
A full length parrot portrait. Sirocco the kakapo poses for the camera. Photo: Mike Bodie.
The inner Solar System, from the Sun to Jupiter. Also includes the asteroid belt (the white donut-shaped cloud), the Hildas (the orange "triangle" just inside the orbit of Jupiter), the Jupiter trojans (green), and the near-Earth asteroids. The group that leads Jupiter are called the "Greeks" and the trailing group are called the "Trojans" (Murray and Dermott, Solar System Dynamics, pg. 107)
This image is based on data found in the en:JPL DE-405 ephemeris, and the en:Minor Planet Center database of asteroids (etc) published 2006 Jul 6. The image is looking down on the en:ecliptic plane as would have been seen on 2006 August 14. It was rendered by custom software written for Wikipedia. The same image without labels is also available at File:InnerSolarSystem.png.
Lactarius torminosus (cropped).jpg
Author/Creator: Tocekas, Licence: CC BY-SA 3.0
Lactarius torminosus. Karmėlava forest, Lithuania.
Profile of Adam Smith. The original depiction of Smith was created in 1787 by James Tassie in the form of an enamel paste medallion. Smith did not usually sit for his portrait, so a considerable number of engravings and busts of Smith were made not from observation but from the same enamel medallion produced by Tassie, an artist who could convince Smith to sit.
Author/Creator: unknown, Licence: CC-BY-SA-3.0
Painting of Volta by Bertini (photo).jpeg
Picture of a painting by Giuseppe Bertini of Alessandro Volta demonstrating his battery to Napoleon in 1801
-200 Sternenliste aus Uruk star list anagoria.JPG
Author/Creator: Anagoria, Licence: CC BY 3.0
Star list with distance information, Uruk (Iraq), 320-150 BC, the list gives each constellation, the number of stars and the distance information to the next constellation in ells. Special exhibition "Beyond the Horizon - Space and Knowledge in the Old World cultures" at the Pergamon Museum (22.06 -. 30.09.2012); Source: Vorderasiatisches Museum SMB Inv. VAT 16436
Sceptical chymist 1661 Boyle Title page AQ18 (3).jpg
Title page from The sceptical chymist : or Chymico-physical doubts and paradoxes, touching the spagyrist's principles commonly call'd hypostatical, as they are wont to be propos'd and defended by the generality of alchymists. Whereunto is praemis'd part of another discourse relating to the same subject / by the Honourable Robert Boyle, Esq. by Robert Boyle, 1627-1691. London : Printed by J. Cadwell for J. Crooke, 1661. Robert Boyle directed his skepticism at the gaggle of common chemists who hawked medicines and deliberately obfuscated their writings. But he worked untiringly on the problem of transmutation and believed there was an alchemical elite who could instruct him. This book is in part an attempt to silence the former and prompt the latter to reveal themselves.
Nuvola apps edu science.svg
Author/Creator: David Vignoni / ICON KING, Licence: LGPL
Icon from Nuvola icon theme for KDE 3.x / GNOME 2.

Kes47 (?)

, Licence: CC BY 3.0
Stylized and exaggerated picture of the precession of the orbit of a planet around the sun.
William Harvey ( 1578-1657) Venenbild.jpg
William Harvey (1578-1657) Image from Harvey's Exercitatio, showing that the blood circulated. When a vein was blocked with a tourniquet, it swelled up, the blood unable to escape back towards the heart.
Lepus europaeus (Causse Méjean, Lozère)-cropped.jpg

Jean-Jacques Boujot from Paris, France

, Licence: CC BY-SA 2.0
Lepus europaeus (Causse méjean, Lozère - France)
Test for ketonuria using Bayer Ketostix reagent strips.
Alpine Chough by Jim Higham.jpg
Author/Creator: Jim Higham from UK, Licence: CC BY 2.0
An Alpine Chough on Schilthorn, Bernese Alps, Switzerland.
Divinatory livers Louvre AO19837.jpg
Divinatory livers, clay models for the training of soothsayers. The one in the middle is interpreted as fortelling the destruction of small cities. Baken clay, 19th–18th centuries BC, found in the royal palace at Mari (now in Syria).
Archimedes pi.svg
Pi approximation
This is hardly how Archimedes approximated Pi, he didn't go from regular pentagon to hexagon to octagon,
but started with a regular hexagon and doubled the number of sides.
PEbers c41-bc.jpg
Author/Creator: , Licence: CC BY-SA 3.0
Papyrus Ebers, column 41
Oxyrhynchus papyrus with Euclid's Elements.jpg
Oxyrhynchus papyrus (P.Oxy. I 29) showing fragment of Euclid's Elements
Darkgreen flag waving.svg
Author/Creator: TristanBomb, Licence: CC0
A dark green flag.
Nuvola apps display.png
Author/Creator: David Vignoni / ICON KING, Licence: LGPL
Icon from Nuvola icon theme for KDE 3.x.
CMS Higgs-event.jpg
Author/Creator: Lucas Taylor / CERN, Licence: CC BY-SA 3.0
An example of simulated data modeled for the CMS particle detector on the Large Hadron Collider (LHC) at CERN. Here, following a collision of two protons, a Higgs boson is produced which decays into two jets of hadrons and two electrons. The lines represent the possible paths of particles produced by the proton-proton collision in the detector while the energy these particles deposit is shown in blue. More CMS events at CMS Media
Lightning simulator questacon02.jpg

flagstaffotos [at] gmail.com
Canon 20D + Tamron 28-75mm f/2.8
Cut out view 04.png
Cut out view 03.png
Cut out view 01.png
, Licence: GFDL 1.2
Lightning Simulator - Questacon, Canberra
Template from Crick and Watson’s DNA molecular model, 1953. (9660573227).jpg
Author/Creator: Science Museum, London / Science and Society Picture Library, Licence: CC BY-SA 2.0
This aluminium template representing the base thymine (T) is part of Crick and Watson’s model of DNA. Bases are those groups of atoms that make up DNA's twin strands. The bases in each of the strands combines to spell out the organism's genetic code. This structure of DNA was discovered by Francis Crick (b 1916) and James Dewey Watson (b 1928) whilst working in the Medical Research Council Unit at the Cavendish Laboratory in Cambridge and after having seen X-ray diffraction pattern photographs of DNA by Rosalind Franklin. In 1953 Watson and Crick constructed a molecular model of the complex genetic material deoxyribonucleic acid (DNA). Their analysis of the double helix shape of DNA explained how genetic information could be copied and passed from one generation to the next. They were awarded the Nobel Prize for medicine and physiology in 1962.
Islamic MedText c1500.jpg

Illuminated opening of the fourth book of the Kitab al-Qanun fi al-tibb (The Canon on Medicine) by Ibn Sina (Avicenna). Undated; probably Iran, beginning of 15th century. The illumination is typical of products from Timurid workshops of the en:15th century.

Source: https://www.nlm.nih.gov/hmd/arabic/E8.html

U.S. National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894

en:Category:Illuminated manuscript images
Ricci Guangqi 2.jpg
Author/Creator: Kircher, Athanasius, 1602-1680., Licence: CC BY-SA 3.0
Matteo Ricci and Paul Xu Guangqi From La Chine d'Athanase Kirchere de la Compagnie de Jesus: illustre de plusieurs monuments tant sacres que profanes, Amsterdam, 1670. Plate facing p. 201.

(Translation of: Athanasii Kircheri e Soc. Jesu China monumentis ... Amstelodami, 1667).

Digital Scan from Villanova University, Falvey Memorial Library, Digital Library.
Stylised atom with three Bohr model orbits and stylised nucleus.svg

SVG by Indolences.

Recoloring and ironing out some glitches done by Rainer Klute., Licence: CC-BY-SA-3.0
Stylised atom. Blue dots are electrons, red dots are protons and black dots are neutrons.
Darwin tree.png
Charles Darwin's 1837 sketch, his first diagram of an evolutionary tree from his First Notebook on Transmutation of Species (1837) on view at the Museum of Natural History in Manhattan.

Interpretation of handwriting: "I think case must be that one generation should have as many living as now. To do this and to have as many species in same genus (as is) requires extinction . Thus between A + B the immense gap of relation. C + B the finest gradation. B+D rather greater distinction. Thus genera would be formed. Bearing relation" (next page begins) "to ancient types with several extinct forms". Text in Darwin's format:

I think 
(tree graph) 
D C 
1 A
(text on the side)
Case must be that one
generation then should be
as many living as now.
To do this & to have many species in
same genus (as is) requires extinction.
(text below tree graph)
Thus between A & B immense
gap of relation. C & B the 
finest gradation, B & D
rather greater distinction.
Thus genera would be
formed. — bearing relation
(The text continues outside the image:)(page 37) to ancient types. — with several extinct forms for if each species an ancient (1) is capable of making 13 recent forms, twelve of the contemporarys must have left no offspring at all, so as to keep number of species constant. — With respect to extinction we can easy see that variety of ostrich, Petise may not be well adapted, and thus perish out, or on other hand like Orpheus being favourable (page 38) many might be produced. — This requires principle that the permanent varieties produced by inter confined breeding & changing circumstances are continued & produced according to the adaptation of such circumstances, & therefore that death of species is a consequence (contrary to what would appear from America). Source of this text: User fileunderwater at https://biology.stackexchange.com/questions/46481/darwins-first-sketch-of-a-phylogenetic-tree , consulted on 26 April 2021.
Nuvola apps edu mathematics-p.svg
Author/Creator: David Vignoni (original icon); Flamurai (SVG convertion), Licence: GPL
Square root of x formula. Symbol of mathematics.
Gresham College from Record of RS.jpg
View from above of Gresham College, London, as it was in the eighteenth century

Model for the Three Superior Planets and Venus from Georg von Peuerbach, Theoricae novae planetarum.
Image enhanced for legibility.
The abbreviations in the center of the diagram read:

  • C[entrum] æquantis (Center of the equant)
  • C[entrum] deferentis (Center of the deferent)
  • C[entrum] mundi (Center of the world)
Sea island survey.jpg
Sea Island survey diagram 窥望海岛之图, first written of by the Chinese mathematician Liu Hui during the Three Kingdoms era (220–280 CE).
Aerogel nasa.jpg
Aerogel cube & Peter Tsou, JPL Scientist, Stardust Deputy Principal Investigator.
Author/Creator: unknown, Licence: CC-BY-SA-3.0
One of two illustrations of 7 physicians from the Vienna Dioscurides.
Banksia sceptrum chris email.jpg

Banksia sceptrum inflorescences, near Jarrahdale Dec 2004

photo Cas Liber
Antikythera mechanism.svg
This is an SVG version of the schematic for the Antikythera mechanism based on the file:Meccanismo_di_Antikytera.jpg
DNA tetrahedron white.png
Author/Creator: Antony-22, Licence: CC BY-SA 3.0
A model of a DNA tetrahedron. Each edge of the tetrahedron is a 20bp DNA duplex, and each vertex is a three-arm junction. In this model each basepair is represented by five pseudo-atoms, representing the two sugars, the two phosphates, and the major groove. The scale bar is 1 nm.
Sir Isaac Newton by Sir Godfrey Kneller, Bt.jpg
This set of images was gathered by User:Dcoetzee from the National Portrait Gallery, London website using a special tool. All images in this batch have been confirmed as author died before 1939 according to the official date listed by the NPG.
фото Дмитрия Ивановича Менделеева
Albert Einstein (Nobel).png
Albert Einstein, official 1921 Nobel Prize in Physics photograph.
Galen detail.jpg
Galen of Pergamon (Claudius Galenus, or in French, Claude Galien), the most famous medical researcher of classical antiquity. Lithograph by Pierre Roche Vigneron. (Paris: Lithograph by Gregoire et Deneux, ca. 1865).
Author/Creator: en:user: Kowloonese, Licence: CC-BY-SA-3.0
A replica of an ancient Chinese Seismograph from Eastern Han Dynasty (25-220 CE).
This picture is taken from an exhibition at Chabot Space & Science Center in Oakland, California.
The plaque of the exhibit said:
Detecting a Quake
In 132 CE, after several earthquakes in China, astronomer Zhang Heng invented this instrument to warn people of the next one. When the ground shook, it moved a pendulum inside the jug. The pendulum pushed a lever that opened one dragon's mouth. A ball rolled out and into the toad's mouth below, sounding an alarm. The open dragon mouth pointed in the direction of the earthquake, notifying the Emperor.
Vesalius Fabrica p190.jpg
Vesalius' Fabrica contains many detailed drawings of human dissections, some of them in allegorical poses.
Guericke Sulfur globe.jpg
Figure V and VI from Ottonis De Guericke Experimenta Nova (ut vocantur) Magdeburgica De Vacuo Spatio, Amstelodami: Janssonius, 1672, p. 148, showing Guericke's experiments with the sulfur globe.
EscherichiaColi NIAID.jpg
Escherichia coli: Scanning electron micrograph of Escherichia coli, grown in culture and adhered to a cover slip.
The iron pillar in the Qutb complex near Delhi, India.
Trinity Test Fireball 25ms.jpg
The 1945 TRINITY nuclear explosion. Rapatronic picture taken 25ms after detonation.
Galileo manuscript.png
This is an image of a draft letter written by Galileo Galilei in August 1609 to Leonardo Donato, Doxe de Venexia, and currently held in the University of Michigan Harlan Hatcher Graduate Library's Special Collections. The University of Michigan states the following about its history:

"In 1609 [Galileo] received a description of a telescope which had been developed the year before in the Dutch town of Middelburg by an optician, one Jan Lippershey. Applying his knowledge of optical science, Galileo built such a glass or telescope for himself, and in the draft letter shown above offers his new "occhiale" to the Doge of Venice for use in warfare. The final letter, revised from this draft, was sent on August 24, 1609. It is in the State Archives in Venice.

The lower part of this sheet shows the use to which Galileo put this optical device: as he viewed the skies on successive evenings in January, 1610, he noted his first observations of the planet Jupiter and four of Jupiter's moons."

This item is cataloged in the collections as:

  • Galileo Galilei (1564-1642).
  • Draft of a letter to Leonardo Donato, Doge of Venice.
  • Circa August, 1609. Gift of Tracy W. McGregor, 1938.

According to Scientific American, when it was donated it was known to be a draft of the letter in the Venice State Archives, but the significance and meaning of the material on the lower half was unrecognized. Only in the late 1970s was it determined that these "doodles" in fact depict the positions of the Galilean moons on the nights in early January when Galileo first observed them, thus proving that this document contains the original notes he took on the nights he made his observations. (See Scientific American article, Date late 70s or early 80s.)

The University of Michigan translates the upper half thus:

"Most Serene Prince.

Galileo Galilei most humbly prostrates himself before Your Highness, watching carefully, and with all spirit of willingness, not only to satisfy what concerns the reading of mathematics in the study of Padua, but to write of having decided to present to Your Highness a telescope that will be a great help in maritime and land enterprises. I assure you I shall keep this new invention a great secret and show it only to Your Highness. The telescope was made for the most accurate study of distances. This telescope has the advantage of discovering the ships of the enemy two hours before they can be seen with the natural vision and to distinguish the number and quality of the ships and to judge their strength and be ready to chase them, to fight them, or to flee from them; or, in the open country to see all details and to distinguish every movement and preparation."
The Scientific Method.svg
Author/Creator: Efbrazil, Licence: CC BY-SA 4.0
Diagram showing the steps of the scientific method, arranged in a circle for rendering as a thumbnail or on small screens
Napier's Bones.JPG
Author/Creator: Kim Traynor, Licence: CC BY-SA 3.0
An ivory set of Napier's Bones from around 1650. An exhibit in the National Museum of Scotland.
Savery Steam Engine, 1698
Sir Mark Oliphant.jpg
Photograph of Sir Mark Oliphant AC KBE
Complex adaptive system.svg
Author/Creator: , Licence: CC0
A way of modeling a Complex Adaptive System. A system with high adaptive capacity exerts complex adaptive behavior in a changing environment.
David Deutsch.jpg
Author/Creator: Simon Benjamin, Licence: CC BY 3.0
David Deutsch
Taken by Apollo 8 crewmember Bill Anders on December 24, 1968, at mission time 075:49:07 [8] (16:40 UTC), while in orbit around the Moon, showing the Earth rising for the third time above the lunar horizon. The lunar horizon is approximately 780 kilometers from the spacecraft. Width of the photographed area at the lunar horizon is about 175 kilometers. [9] The land mass visible just above the terminator line is west Africa. Note that this phenomenon is only visible to an observer in motion relative to the lunar surface. Because of the Moon's synchronous rotation relative to the Earth (i.e., the same side of the Moon is always facing Earth), the Earth appears to be stationary (measured in anything less than a geological timescale) in the lunar "sky". In order to observe the effect of Earth rising or setting over the Moon's horizon, an observer must travel towards or away from the point on the lunar surface where the Earth is most directly overhead (centred in the sky). Otherwise, the Earth's apparent motion/visible change will be limited to: 1. Growing larger/smaller as the orbital distance between the two bodies changes. 2. Slight apparent movement of the Earth due to the eccenticity of the Moon's orbit, the effect being called libration. 3. Rotation of the Earth (the Moon's rotation is synchronous relative to the Earth, the Earth's rotation is not synchronous relative to the Moon). 4. Atmospheric & surface changes on Earth (i.e.: weather patterns, changing seasons, etc.). Two craters, visible on the image were named 8 Homeward and Anders' Earthrise in honor of Apollo 8 by IAU in 2018. [10]
Author/Creator: Andrew Dunn, Licence: CC BY-SA 2.0
An 18th Century Persian astrolabe – maker unknown. The points of the curved spikes on the front rete plate, mark the positions of the brightest stars. The name of each star being labeled at the base of each spike. The back plate, or mater is engraved with projected coordinate lines. From the Whipple Museum of the History of Science in Cambridge.
Oryzomys distribution S America.png
Author/Creator: , Licence: CC BY-SA 3.0
Distribution of the genus en:Oryzomys in Panama and northwestern South America. Red: O. couesi; brown: O. gorgasi.