The United States of America known as the United States or America, is a country composed of 50 states, a federal district, five major self-governing territories, various possessions. At 3.8 million square miles, the United States is the world's third or fourth largest country by total area and is smaller than the entire continent of Europe's 3.9 million square miles. With a population of over 327 million people, the U. S. is the third most populous country. The capital is Washington, D. C. and the largest city by population is New York City. Forty-eight states and the capital's federal district are contiguous in North America between Canada and Mexico; the State of Alaska is in the northwest corner of North America, bordered by Canada to the east and across the Bering Strait from Russia to the west. The State of Hawaii is an archipelago in the mid-Pacific Ocean; the U. S. territories are scattered about the Pacific Ocean and the Caribbean Sea, stretching across nine official time zones. The diverse geography and wildlife of the United States make it one of the world's 17 megadiverse countries.
Paleo-Indians migrated from Siberia to the North American mainland at least 12,000 years ago. European colonization began in the 16th century; the United States emerged from the thirteen British colonies established along the East Coast. Numerous disputes between Great Britain and the colonies following the French and Indian War led to the American Revolution, which began in 1775, the subsequent Declaration of Independence in 1776; the war ended in 1783 with the United States becoming the first country to gain independence from a European power. The current constitution was adopted in 1788, with the first ten amendments, collectively named the Bill of Rights, being ratified in 1791 to guarantee many fundamental civil liberties; the United States embarked on a vigorous expansion across North America throughout the 19th century, acquiring new territories, displacing Native American tribes, admitting new states until it spanned the continent by 1848. During the second half of the 19th century, the Civil War led to the abolition of slavery.
By the end of the century, the United States had extended into the Pacific Ocean, its economy, driven in large part by the Industrial Revolution, began to soar. The Spanish–American War and World War I confirmed the country's status as a global military power; the United States emerged from World War II as a global superpower, the first country to develop nuclear weapons, the only country to use them in warfare, a permanent member of the United Nations Security Council. Sweeping civil rights legislation, notably the Civil Rights Act of 1964, the Voting Rights Act of 1965 and the Fair Housing Act of 1968, outlawed discrimination based on race or color. During the Cold War, the United States and the Soviet Union competed in the Space Race, culminating with the 1969 U. S. Moon landing; the end of the Cold War and the collapse of the Soviet Union in 1991 left the United States as the world's sole superpower. The United States is the world's oldest surviving federation, it is a representative democracy.
The United States is a founding member of the United Nations, World Bank, International Monetary Fund, Organization of American States, other international organizations. The United States is a developed country, with the world's largest economy by nominal GDP and second-largest economy by PPP, accounting for a quarter of global GDP; the U. S. economy is post-industrial, characterized by the dominance of services and knowledge-based activities, although the manufacturing sector remains the second-largest in the world. The United States is the world's largest importer and the second largest exporter of goods, by value. Although its population is only 4.3% of the world total, the U. S. holds 31% of the total wealth in the world, the largest share of global wealth concentrated in a single country. Despite wide income and wealth disparities, the United States continues to rank high in measures of socioeconomic performance, including average wage, human development, per capita GDP, worker productivity.
The United States is the foremost military power in the world, making up a third of global military spending, is a leading political and scientific force internationally. In 1507, the German cartographer Martin Waldseemüller produced a world map on which he named the lands of the Western Hemisphere America in honor of the Italian explorer and cartographer Amerigo Vespucci; the first documentary evidence of the phrase "United States of America" is from a letter dated January 2, 1776, written by Stephen Moylan, Esq. to George Washington's aide-de-camp and Muster-Master General of the Continental Army, Lt. Col. Joseph Reed. Moylan expressed his wish to go "with full and ample powers from the United States of America to Spain" to seek assistance in the revolutionary war effort; the first known publication of the phrase "United States of America" was in an anonymous essay in The Virginia Gazette newspaper in Williamsburg, Virginia, on April 6, 1776. The second draft of the Articles of Confederation, prepared by John Dickinson and completed by June 17, 1776, at the latest, declared "The name of this Confederation shall be the'United States of America'".
The final version of the Articles sent to the states for ratification in late 1777 contains the sentence "The Stile of this Confederacy shall be'The United States of America'". In June 1776, Thomas Jefferson wrote the phrase "UNITED STATES OF AMERICA" in all capitalized letters in the headline of his "original Rough draught" of the Declaration of Independence; this draft of the document did not surface unti
Robert Grant Aitken
For others named, see the Robert Aitken navigation pageRobert Grant Aitken was an American astronomer. Born in Jackson, Aitken attended Williams College in Massachusetts and graduated with an undergraduate degree in 1887. From 1887–1891, he worked as a mathematics instructor at Livermore, California received his M. A. from Williams College in 1892. He became a professor of mathematics at the College of another liberal arts school, he was offered an assistant astronomer position at Lick Observatory in California in 1895. He began a systematically study of double stars, measuring their positions and calculating their orbits around one another. From 1899, in collaboration with W. J. Hussey, he methodically created a large catalog of such stars; this ongoing work was published in Lick Observatory bulletins. In 1905, Hussey left and Aitken pressed on with the survey alone, by 1915, he had discovered 3,100 new binary stars, with an additional 1,300 discovered by Hussey; the results were published in 1932 and entitled New General Catalogue of Double Stars Within 120° of the North Pole, with the orbit information enabling astronomers to calculate stellar mass statistics for a large number of stars.
For his work in cataloguing binary stars, he was awarded the prestigious Bruce Medal in 1926. During his career, Aitken measured positions and computed orbits for comets and natural satellites of planets. In 1908 he joined an eclipse expedition to Flint Island in the central Pacific Ocean, his work Binary Stars was published in 1918, with a second edition published in 1935. After joining the Astronomical Society of the Pacific in 1894, Aitken was elected to serve as president in 1899 and 1915 of the Astronomical Society of the Pacific. From 1898 to 1942, Aitken was an editor of the Publications of the Astronomical Society of the Pacific. In 1932, he delivered the Darwin Lecture before the Royal Astronomical Society, where he was an associate member. From 1918 to 1928, he was chair of the double star committee for the International Astronomical Union. Aitken was deaf and used a hearing aid, he married Jessie Thomas around 1888, had three sons and one daughter. Jessie died in 1943, his grandson, Robert Baker Aitken, was a known Zen Buddhist teacher and author.
His granddaughter Marjorie J. Vold was a noted chemist specializing in colloids. AwardsLalande Prize of the French Academy Bruce Medal Gold Medal of the Royal Astronomical Society Rittenhouse Medal Honorary Sc. D. from College of the Pacific, Williams College, University of Arizona, an honorary LL. D. from the University of CaliforniaNamed after himMinor planet 3070 Aitken Lunar crater Aitken, part of the large South Pole-Aitken basin Bruce Medal page Awarding of Bruce Medal Awarding of RAS gold medal Biographical Memoir by Van Den Bos at the National academy of Sciences Double Star Observer, Cataloguer and Observatory Director Additional Photos from the Emilio Segre Visual Archive, American Institute of Physics Portrait of Robert G. Aitkin from the Lick Observatory Records Digital Archive, UC Santa Cruz Library's Digital Collections Digital version of The Binary Stars published by Dover in 1964 IrAJ 2 27 JO 35 25 JRASC 46 28 MNRAS 112 271 PASP 64 5
The Astronomical Journal
The Astronomical Journal is a peer-reviewed monthly scientific journal owned by the American Astronomical Society and published by IOP Publishing. It is one of the premier journals for astronomy in the world; until 2008, the journal was published by the University of Chicago Press on behalf of the American Astronomical Society. The reasons for the change were given by the society as the desire of the University of Chicago Press to revise its financial arrangement and their plans to change from the particular software, developed in-house; the other two publications of the society, the Astrophysical Journal and its supplement series, followed in January 2009. The journal was established in 1849 by Benjamin A. Gould, it ceased publication in 1861 due to the American Civil War, but resumed in 1885. Between 1909 and 1941 the journal was edited in New York. In 1941, editor Benjamin Boss arranged to transfer responsibility for the journal to the American Astronomical Society; the first electronic edition of The Astronomical Journal was published in January, 1998.
With the July, 2006 issue, The Astronomical Journal began e-first publication, an electronic version of the journal released independently of the hardcopy issues. 2005–2015 John Gallagher III 1984–2004 Paul W. Hodge 1980–1983 N. H. Baker 1975–1979 N. H. Baker and L. B. Lucy 1967–1974 Lodewijk Woltjer 1966–1967 Gerald Maurice Clemence 1965–1966 Dirk Brouwer and Gerald Maurice Clemence 1963–1965 Dirk Brouwer 1959–1963 Dirk Brouwer and Harlan James Smith 1941–1959 Dirk Brouwer 1912–1941 Benjamin Boss 1909–1912 Lewis Boss 1896–1909 Seth Carlo Chandler 1849–1861, 1885–1896 Benjamin A. Gould, Jr; the Astronomical Almanac The Astrophysical Journal Official website Dudley Observatory, The Astronomical Journal Scanned issues from ADS
The Solar System is the gravitationally bound planetary system of the Sun and the objects that orbit it, either directly or indirectly. Of the objects that orbit the Sun directly, the largest are the eight planets, with the remainder being smaller objects, such as the five dwarf planets and small Solar System bodies. Of the objects that orbit the Sun indirectly—the moons—two are larger than the smallest planet, Mercury; the Solar System formed 4.6 billion years ago from the gravitational collapse of a giant interstellar molecular cloud. The vast majority of the system's mass is in the Sun, with the majority of the remaining mass contained in Jupiter; the four smaller inner planets, Venus and Mars, are terrestrial planets, being composed of rock and metal. The four outer planets are giant planets, being more massive than the terrestrials; the two largest and Saturn, are gas giants, being composed of hydrogen and helium. All eight planets have circular orbits that lie within a nearly flat disc called the ecliptic.
The Solar System contains smaller objects. The asteroid belt, which lies between the orbits of Mars and Jupiter contains objects composed, like the terrestrial planets, of rock and metal. Beyond Neptune's orbit lie the Kuiper belt and scattered disc, which are populations of trans-Neptunian objects composed of ices, beyond them a newly discovered population of sednoids. Within these populations are several dozen to tens of thousands of objects large enough that they have been rounded by their own gravity; such objects are categorized as dwarf planets. Identified dwarf planets include the trans-Neptunian objects Pluto and Eris. In addition to these two regions, various other small-body populations, including comets and interplanetary dust clouds travel between regions. Six of the planets, at least four of the dwarf planets, many of the smaller bodies are orbited by natural satellites termed "moons" after the Moon; each of the outer planets is encircled by planetary rings of dust and other small objects.
The solar wind, a stream of charged particles flowing outwards from the Sun, creates a bubble-like region in the interstellar medium known as the heliosphere. The heliopause is the point at which pressure from the solar wind is equal to the opposing pressure of the interstellar medium; the Oort cloud, thought to be the source for long-period comets, may exist at a distance a thousand times further than the heliosphere. The Solar System is located in the Orion Arm, 26,000 light-years from the center of the Milky Way galaxy. For most of history, humanity did not understand the concept of the Solar System. Most people up to the Late Middle Ages–Renaissance believed Earth to be stationary at the centre of the universe and categorically different from the divine or ethereal objects that moved through the sky. Although the Greek philosopher Aristarchus of Samos had speculated on a heliocentric reordering of the cosmos, Nicolaus Copernicus was the first to develop a mathematically predictive heliocentric system.
In the 17th century, Galileo discovered that the Sun was marked with sunspots, that Jupiter had four satellites in orbit around it. Christiaan Huygens followed on from Galileo's discoveries by discovering Saturn's moon Titan and the shape of the rings of Saturn. Edmond Halley realised in 1705 that repeated sightings of a comet were recording the same object, returning once every 75–76 years; this was the first evidence that anything other than the planets orbited the Sun. Around this time, the term "Solar System" first appeared in English. In 1838, Friedrich Bessel measured a stellar parallax, an apparent shift in the position of a star created by Earth's motion around the Sun, providing the first direct, experimental proof of heliocentrism. Improvements in observational astronomy and the use of unmanned spacecraft have since enabled the detailed investigation of other bodies orbiting the Sun; the principal component of the Solar System is the Sun, a G2 main-sequence star that contains 99.86% of the system's known mass and dominates it gravitationally.
The Sun's four largest orbiting bodies, the giant planets, account for 99% of the remaining mass, with Jupiter and Saturn together comprising more than 90%. The remaining objects of the Solar System together comprise less than 0.002% of the Solar System's total mass. Most large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic; the planets are close to the ecliptic, whereas comets and Kuiper belt objects are at greater angles to it. All the planets, most other objects, orbit the Sun in the same direction that the Sun is rotating. There are exceptions, such as Halley's Comet; the overall structure of the charted regions of the Solar System consists of the Sun, four small inner planets surrounded by a belt of rocky asteroids, four giant planets surrounded by the Kuiper belt of icy objects. Astronomers sometimes informally divide this structure into separate regions; the inner Solar System includes the asteroid belt. The outer Solar System is including the four giant planets.
Since the discovery of the Kuiper belt, the outermost parts of the Solar Sys
A supercluster is a large group of smaller galaxy clusters or galaxy groups. The Milky Way is part of the Local Group galaxy group, which in turn is part of the Laniakea Supercluster; this supercluster spans over 500 million light-years, while the Local Group spans over 10 million light-years. The large size and low density of superclusters means they, unlike clusters, expand with the Hubble expansion; the number of superclusters in the observable universe is estimated to be 10 million. The existence of superclusters indicates that the galaxies in the Universe are not uniformly distributed; those groups and clusters and additional isolated galaxies in turn form larger structures called superclusters. Their existence was first postulated by George Abell in his 1958 Abell catalogue of galaxy clusters, he called them clusters of clusters. Superclusters form massive structures of galaxies, called "filaments", "supercluster complexes", "walls" or "sheets", that may span between several hundred million light-years to 10 billion light-years, covering more than 5% of the observable universe.
These are the largest known structures to date. Observations of superclusters can give information about the initial condition of the universe, when these superclusters were created; the directions of the rotational axes of galaxies within superclusters may give insight and information into the early formation process of galaxies in the history of the Universe. Interspersed among superclusters are large voids of space. Superclusters are subdivided into groups of clusters called galaxy groups and clusters. Freedman, Roger. "Galaxies". Universe. New York: W. H. Freedman. ISBN 978-1-319-04238-7. Media related to Superclusters of galaxies at Wikimedia Commons Overview of local superclusters The Nearest Superclusters Universe family tree: Supercluster Superclusters - Large Scale Structures
Simon Newcomb was a Canadian–American astronomer, applied mathematician and autodidactic polymath, Professor of Mathematics in the U. S. Navy and at Johns Hopkins. Though he had little conventional schooling, he made important contributions to timekeeping as well as other fields in applied mathematics such as economics and statistics in addition to writing a science fiction novel. Simon Newcomb was born in the town of Nova Scotia, his parents were Emily Prince, the daughter of a New Brunswick magistrate, itinerant school teacher John Burton Newcomb. John moved around teaching in different parts of Canada in different villages in Nova Scotia and Prince Edward Island. Emily was a daughter of Thomas Prince and Miriam Steeves, making Simon a great-great-grandson of Heinrich Stief, a not-too-distant cousin of William Henry Steeves, a Canadian Father of Confederation. Newcomb seems to have had little conventional schooling other than from his father and from a short apprenticeship to Dr. Foshay, a charlatan herbalist, in New Brunswick in 1851.
His father provided him with an excellent foundation for his future studies. Newcomb's apprenticeship with Dr. Foshay occurred, they entered an agreement that Newcomb would serve a five-year apprenticeship during which time Foshay would train him in using herbs to treat illnesses. For two years he was an apprentice but became unhappy and disillusioned with his apprenticeship and about Foshay's unscientific approach, realizing that the man was a charlatan, he made the decision to break their agreement. He walked the 120 miles to the port of Calais in Maine where he met the captain of a ship who agreed to take him to Salem, Massachusetts so that he could join his father. In about 1854, he joined his father in Salem, the two journeyed together to Maryland. After arriving in Maryland, Newcomb taught for two years from 1854 to 1856. In his spare time he studied a variety of subjects such as political economy and religion, but his deepest studies were made in mathematics and astronomy. In particular he read Newton's Principia at this time.
In 1856 he took up a position as a private tutor close to Washington and he travelled to that city to study mathematics in the libraries there. He was able to borrow a copy of Bowditch's translation of Laplace's Traité de mécanique céleste from the library of the Smithsonian Institution but found the mathematics beyond him. Newcomb studied mathematics and physics and supported himself by teaching before becoming a human computer at the Nautical Almanac Office in Cambridge, Massachusetts in 1857. At around the same time, he enrolled at the Lawrence Scientific School of Harvard University, graduating BSc in 1858. Newcomb studied mathematics under Benjamin Peirce and the impecunious Newcomb was a welcome guest at the Peirce home. However, he was said to develop a dislike of Peirce's son, Charles Sanders Peirce and has been accused of a "successful destruction" of C. S. Peirce's career. In particular, Daniel Coit Gilman, president of Johns Hopkins University, is alleged to have been on the point of awarding tenure to C. S. Peirce, before Newcomb intervened behind the scenes to dissuade him.
About 20 years Newcomb influenced the Carnegie Institution Trustees, to prevent C. S. Peirce's last chance to publish his life's work, through a denial of a Carnegie grant to Peirce though Andrew Carnegie himself, Theodore Roosevelt, William James and others, wrote to support it. In the prelude to the American Civil War, many US Navy staff of Confederate sympathies left the service and, in 1861, Newcomb took advantage of one of the ensuing vacancies to become professor of mathematics and astronomer at the United States Naval Observatory, Washington D. C.. Newcomb set to work on the measurement of the position of the planets as an aid to navigation, becoming interested in theories of planetary motion. By the time Newcomb visited Paris, France in 1870, he was aware that the table of lunar positions calculated by Peter Andreas Hansen was in error. While in Paris, he realised that, in addition to the data from 1750 to 1838 that Hansen had used, there was further data stretching as far back as 1672.
His visit allowed little serenity for analysis as he witnessed the defeat of French emperor Napoleon III in the Franco-Prussian War and the coup that ended the Second French Empire. Newcomb managed to escape from the city during the ensuing rioting that led up to the formation of the Paris Commune and which engulfed the Paris Observatory. Newcomb was able to use the "new" data to revise Hansen's tables, he was offered the post of director of the Harvard College Observatory in 1875 but declined, having by now settled that his interests lay in mathematics rather than observation. In 1877 he became director of the Nautical Almanac Office where, ably assisted by George William Hill, he embarked on a program of recalculation of all the major astronomical constants. Despite fulfilling a further demanding role as professor of mathematics and astronomy at Johns Hopkins University from 1884, he conceived with A. M. W. Downing a plan to resolve much international confusion on the subject. By the time he attended a standardisation conference in Paris, France, in May 1896, the international consensus was that all ephemerides should be based on Newcomb's calculations—Newcomb's Tables of the Sun.
A further conference as late as 1950 confirmed Newcomb's constants as the int
An astronomer is a scientist in the field of astronomy who focuses their studies on a specific question or field outside the scope of Earth. They observe astronomical objects such as stars, moons and galaxies – in either observational or theoretical astronomy. Examples of topics or fields astronomers study include planetary science, solar astronomy, the origin or evolution of stars, or the formation of galaxies. Related but distinct subjects like physical cosmology. Astronomers fall under either of two main types: observational and theoretical. Observational astronomers analyze the data. In contrast, theoretical astronomers create and investigate models of things that cannot be observed; because it takes millions to billions of years for a system of stars or a galaxy to complete a life cycle, astronomers must observe snapshots of different systems at unique points in their evolution to determine how they form and die. They use these data to create models or simulations to theorize how different celestial objects work.
Further subcategories under these two main branches of astronomy include planetary astronomy, galactic astronomy, or physical cosmology. Astronomy was more concerned with the classification and description of phenomena in the sky, while astrophysics attempted to explain these phenomena and the differences between them using physical laws. Today, that distinction has disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are educated individuals who have a Ph. D. in physics or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although they quite have other duties such as teaching, building instruments, or aiding in the operation of an observatory; the number of professional astronomers in the United States is quite small. The American Astronomical Society, the major organization of professional astronomers in North America, has 7,000 members; this number includes scientists from other fields such as physics and engineering, whose research interests are related to astronomy.
The International Astronomical Union comprises 10,145 members from 70 different countries who are involved in astronomical research at the Ph. D. beyond. Contrary to the classical image of an old astronomer peering through a telescope through the dark hours of the night, it is far more common to use a charge-coupled device camera to record a long, deep exposure, allowing a more sensitive image to be created because the light is added over time. Before CCDs, photographic plates were a common method of observation. Modern astronomers spend little time at telescopes just a few weeks per year. Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time. Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities have outreach programs including public telescope time and sometimes planetariums as a public service to encourage interest in the field.
Those who become astronomers have a broad background in maths and computing in high school. Taking courses that teach how to research and present papers are invaluable. In college/university most astronomers get a Ph. D. in astronomy or physics. While there is a low number of professional astronomers, the field is popular among amateurs. Most cities have amateur astronomy clubs that meet on a regular basis and host star parties; the Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations. Like any hobby, most people who think of themselves as amateur astronomers may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to the ambitious, who own science-grade telescopes and instruments with which they are able to make their own discoveries and assist professional astronomers in research.
List of astronomers List of women astronomers List of Muslim astronomers List of French astronomers List of Hungarian astronomers List of Russian astronomers and astrophysicists List of Slovenian astronomers Dallal, Ahmad. "Science and Technology". In Esposito, John; the Oxford History of Islam. Oxford University Press, New York. ISBN 0-300-15911-0. Kennedy, E. S.. "A Survey of Islamic Astronomical Tables. 46. Philadelphia: American Philosophical Society. Toomer, Gerald. "Al-Khwārizmī, Abu Jaʿfar Muḥammad ibn Mūsā". In Gillispie, Charles Coulston. Dictionary of Scientific Biography. 7. New York: Charles Scribner's Sons. ISBN 0-684-16962-2. American Astronomical Society European Astronomical Society International Astronomical Union Astronomical Society of the Pacific Space's astronomy news