Ernest William Brown
Encyclopedia
Ernest William Brown FRS (29 November 1866 – 22 July 1938) was a British
mathematician
and astronomer
, who spent the majority of his career working in the United States
.
His life's work was the study of the Moon
's motion (lunar theory
) and the compilation of extremely accurate lunar tables. He also studied the motion of the planet
s and calculated the orbits of Trojan asteroid
s.
, England
, the only son of William and Emma (Martin) Brown. He was educated at Hull and East Riding College
. After leaving school, he entered Christ's College
, Cambridge
, where he graduated with first-class honours in mathematics in 1887. He continued with post-graduate studies at Cambridge and worked under the direction of George Howard Darwin. In the summer of 1888, Darwin suggested that Brown study the papers of George William Hill
on the lunar theory. As it turned out, this idea for a line of research was to have a major impact on the remainder of Brown's life.
Brown was made a fellow of Christ's College in 1889, and received his Masters degree in 1891. He then left England to take up a place as a mathematics instructor at Haverford College
, Pennsylvania
. There, he rose rapidly to the position of Professor of Mathematics in 1893.
and Hansen
. His mastery of the field was shown by the publication of his first great work, An Introductory Treatise on the Lunar Theory
, in 1896, when Brown was still less than 30 years of age. As Brown's work progressed, he gradually evolved a plan to create a completely new lunar theory. This was eventually published as a series of papers in the Memoirs of the Royal Astronomical Society
between 1897 and 1908.
In 1907, Brown was appointed Professor of Mathematics at Yale University
. He secured an agreement with Yale for funding the massive task of calculating detailed tables of the Moon's motion, based on his lunar theory. After a period of 12 years and a cost of over $34,000, Brown's magnum opus
, Tables of the Motion of the Moon, was published in 1919.
of the Moon, based purely on gravitational theory. For the 'main problem' of the Earth-Moon-Sun system, he calculated terms in longitude and latitude down to an uncertainty of 0.001 arcseconds. He also included perturbations due to the other planets (principally Jupiter
and Venus
) and also accounted for the more difficult problem of the non-spherical nature of the Earth and Moon.
Observations showed that Brown's tables were indeed superior to those of Hansen, which had been in use since 1857, but there was still a large unexplained fluctuation in the Moon's mean longitude of the order of 10 arcseconds. A 'great empirical term', of magnitude 10.71 arcseconds and period 257 years, was introduced to eliminate this as far as possible. Given the precision of Brown's calculations, it must have come as a great disappointment to have to introduce this arbitrary adjustment.
It had been discovered by Edmond Halley
over two centuries previously that the Moon's motion appeared to be gradually speeding up. This 'secular acceleration' could not be explained by gravitational theory alone, and it had been suggested by Simon Newcomb
that it was in fact due to a gradual deceleration of the Earth's rate of rotation, due to friction generated by the tide
s. In other words, the Moon was not speeding up – it was time (as measured in terms of Earth's increasingly long day) that appeared to be slowing down. Brown devoted much study to this problem and eventually concluded that, not only was the Earth's rate of rotation slowing, but there were also random, unpredictable fluctuations. Later work has shown this to be true, and astronomers now make a distinction between Universal Time
, which is based on the Earth's rotation, and Terrestrial Time
(formerly Ephemeris time
), which is a uniform measure of the passage of time (see also ΔT).
already became an instructor at Columbia University
while finishing his PhD under Brown. Eckert would improve the pace of astronomical calculation by automating them with digital computers.
Brown retained his professorship at Yale until he retired in 1932. As well as continuing his work on the Moon, he also worked on the motion of the planet
s around the Sun
. He co-wrote the book, Planetary Theory, with Clarence Shook, which contained a detailed exposition of resonance
in planetary orbits and examined the special case of the Trojan asteroid
s.
A heavy smoker, Brown suffered from bronchial trouble for much of his life. He was afflicted by ill-health during most of the six years of his retirement, and died in New Haven, Connecticut
in 1938.
s, Brown's original trigonometrical expressions, given in the introduction to his 1919 tables (and from which the tables had been compiled), began to be used for direct computation instead of the tables themselves. This also gained some improvement in precision, since the tables themselves had embodied some minor approximations, in a trade-off between accuracy and the amount of labor need for computations using the tables in those days of manual calculation. By mid-century, the difference between Universal and Ephemeris Time had been recognised and evaluated, and the troublesome empirical terms were also removed. Further adjustments to Brown's theory were then also made in a later stage, arising from improved observational values of the fundamental astronomical constants used in the theory, and from re-working Brown's original analytical expansions to gain more precise versions of the coefficients used in the theory.
It was only as recently as in the ephemerides for 1984 that Brown's work was superseded: it was replaced by results gained from more modern observational data (including data from lunar laser ranging) and by altogether new computational methods for calculating the Moon's ephemeris.
British people
The British are citizens of the United Kingdom, of the Isle of Man, any of the Channel Islands, or of any of the British overseas territories, and their descendants...
mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....
and astronomer
Astronomer
An astronomer is a scientist who studies celestial bodies such as planets, stars and galaxies.Historically, 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...
, who spent the majority of his career working in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...
.
His life's work was the study of the Moon
Moon
The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...
's motion (lunar theory
Lunar theory
Lunar theory attempts to account for the motions of the Moon. There are many irregularities in the Moon's motion, and many attempts have been made over a long history to account for them. After centuries of being heavily problematic, the lunar motions are nowadays modelled to a very high degree...
) and the compilation of extremely accurate lunar tables. He also studied the motion of the planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s and calculated the orbits of Trojan asteroid
Trojan asteroid
The Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of the planet's two Lagrangian points of stability, and , that respectively lie 60° ahead...
s.
Education
Brown was born in HullKingston upon Hull
Kingston upon Hull , usually referred to as Hull, is a city and unitary authority area in the ceremonial county of the East Riding of Yorkshire, England. It stands on the River Hull at its junction with the Humber estuary, 25 miles inland from the North Sea. Hull has a resident population of...
, England
England
England is a country that is part of the United Kingdom. It shares land borders with Scotland to the north and Wales to the west; the Irish Sea is to the north west, the Celtic Sea to the south west, with the North Sea to the east and the English Channel to the south separating it from continental...
, the only son of William and Emma (Martin) Brown. He was educated at Hull and East Riding College
East Riding College
East Riding College is a further education college located in the East Riding of Yorkshire, England. It was formed in March 2002, by the merger of Beverley College and East Yorkshire College, Bridlington.-Campuses and locations:...
. After leaving school, he entered Christ's College
Christ's College, Cambridge
Christ's College is a constituent college of the University of Cambridge.With a reputation for high academic standards, Christ's College averaged top place in the Tompkins Table from 1980-2000 . In 2011, Christ's was placed sixth.-College history:...
, Cambridge
Cambridge
The city of Cambridge is a university town and the administrative centre of the county of Cambridgeshire, England. It lies in East Anglia about north of London. Cambridge is at the heart of the high-technology centre known as Silicon Fen – a play on Silicon Valley and the fens surrounding the...
, where he graduated with first-class honours in mathematics in 1887. He continued with post-graduate studies at Cambridge and worked under the direction of George Howard Darwin. In the summer of 1888, Darwin suggested that Brown study the papers of George William Hill
George William Hill
George William Hill , was an American astronomer and mathematician.Hill was born in New York City, New York to painter and engraver John William Hill. and Catherine Smith Hill. He moved to West Nyack with his family when he was eight years old. After attending high school, Hill graduated from...
on the lunar theory. As it turned out, this idea for a line of research was to have a major impact on the remainder of Brown's life.
Brown was made a fellow of Christ's College in 1889, and received his Masters degree in 1891. He then left England to take up a place as a mathematics instructor at Haverford College
Haverford College
Haverford College is a private, coeducational liberal arts college located in Haverford, Pennsylvania, United States, a suburb of Philadelphia...
, Pennsylvania
Pennsylvania
The Commonwealth of Pennsylvania is a U.S. state that is located in the Northeastern and Mid-Atlantic regions of the United States. The state borders Delaware and Maryland to the south, West Virginia to the southwest, Ohio to the west, New York and Ontario, Canada, to the north, and New Jersey to...
. There, he rose rapidly to the position of Professor of Mathematics in 1893.
Work on the motion of the Moon
At Haverford, Brown continued with his studies of the lunar theory, and made a thorough review of the work of earlier researchers, such as Hill, DelaunayCharles-Eugène Delaunay
Charles-Eugène Delaunay was a French astronomer and mathematician. His lunar motion studies were important in advancing both the theory of planetary motion and mathematics.-Life:...
and Hansen
Peter Andreas Hansen
Peter Andreas Hansen was a Danish astronomer, was born at Tønder, Schleswig.-Biography:The son of a goldsmith, Hansen learned the trade of a watchmaker at Flensburg, and exercised it at Berlin and Tønder, 1818–1820...
. His mastery of the field was shown by the publication of his first great work, An Introductory Treatise on the Lunar Theory
Lunar theory
Lunar theory attempts to account for the motions of the Moon. There are many irregularities in the Moon's motion, and many attempts have been made over a long history to account for them. After centuries of being heavily problematic, the lunar motions are nowadays modelled to a very high degree...
, in 1896, when Brown was still less than 30 years of age. As Brown's work progressed, he gradually evolved a plan to create a completely new lunar theory. This was eventually published as a series of papers in the Memoirs of the Royal Astronomical Society
Royal Astronomical Society
The Royal Astronomical Society is a learned society that began as the Astronomical Society of London in 1820 to support astronomical research . It became the Royal Astronomical Society in 1831 on receiving its Royal Charter from William IV...
between 1897 and 1908.
In 1907, Brown was appointed Professor of Mathematics at Yale University
Yale University
Yale University is a private, Ivy League university located in New Haven, Connecticut, United States. Founded in 1701 in the Colony of Connecticut, the university is the third-oldest institution of higher education in the United States...
. He secured an agreement with Yale for funding the massive task of calculating detailed tables of the Moon's motion, based on his lunar theory. After a period of 12 years and a cost of over $34,000, Brown's magnum opus
Masterpiece
Masterpiece in modern usage refers to a creation that has been given much critical praise, especially one that is considered the greatest work of a person's career or to a work of outstanding creativity, skill or workmanship....
, Tables of the Motion of the Moon, was published in 1919.
Discrepancies between theory and observation
Brown's objective had been to produce an accurate ephemerisEphemeris
An ephemeris is a table of values that gives the positions of astronomical objects in the sky at a given time or times. Different kinds of ephemerides are used for astronomy and astrology...
of the Moon, based purely on gravitational theory. For the 'main problem' of the Earth-Moon-Sun system, he calculated terms in longitude and latitude down to an uncertainty of 0.001 arcseconds. He also included perturbations due to the other planets (principally Jupiter
Jupiter
Jupiter is the fifth planet from the Sun and the largest planet within the Solar System. It is a gas giant with mass one-thousandth that of the Sun but is two and a half times the mass of all the other planets in our Solar System combined. Jupiter is classified as a gas giant along with Saturn,...
and Venus
Venus
Venus is the second planet from the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus, the Roman goddess of love and beauty. After the Moon, it is the brightest natural object in the night sky, reaching an apparent magnitude of −4.6, bright enough to cast shadows...
) and also accounted for the more difficult problem of the non-spherical nature of the Earth and Moon.
Observations showed that Brown's tables were indeed superior to those of Hansen, which had been in use since 1857, but there was still a large unexplained fluctuation in the Moon's mean longitude of the order of 10 arcseconds. A 'great empirical term', of magnitude 10.71 arcseconds and period 257 years, was introduced to eliminate this as far as possible. Given the precision of Brown's calculations, it must have come as a great disappointment to have to introduce this arbitrary adjustment.
It had been discovered by Edmond Halley
Edmond Halley
Edmond Halley FRS was an English astronomer, geophysicist, mathematician, meteorologist, and physicist who is best known for computing the orbit of the eponymous Halley's Comet. He was the second Astronomer Royal in Britain, following in the footsteps of John Flamsteed.-Biography and career:Halley...
over two centuries previously that the Moon's motion appeared to be gradually speeding up. This 'secular acceleration' could not be explained by gravitational theory alone, and it had been suggested by Simon Newcomb
Simon Newcomb
Simon Newcomb was a Canadian-American astronomer and mathematician. Though he had little conventional schooling, he made important contributions to timekeeping as well as writing on economics and statistics and authoring a science fiction novel.-Early life:Simon Newcomb was born in the town of...
that it was in fact due to a gradual deceleration of the Earth's rate of rotation, due to friction generated by the tide
Tide
Tides are the rise and fall of sea levels caused by the combined effects of the gravitational forces exerted by the moon and the sun and the rotation of the Earth....
s. In other words, the Moon was not speeding up – it was time (as measured in terms of Earth's increasingly long day) that appeared to be slowing down. Brown devoted much study to this problem and eventually concluded that, not only was the Earth's rate of rotation slowing, but there were also random, unpredictable fluctuations. Later work has shown this to be true, and astronomers now make a distinction between Universal Time
Universal Time
Universal Time is a time scale based on the rotation of the Earth. It is a modern continuation of Greenwich Mean Time , i.e., the mean solar time on the Prime Meridian at Greenwich, and GMT is sometimes used loosely as a synonym for UTC...
, which is based on the Earth's rotation, and Terrestrial Time
Terrestrial Time
Terrestrial Time is a modern astronomical time standard defined by the International Astronomical Union, primarily for time-measurements of astronomical observations made from the surface of the Earth....
(formerly Ephemeris time
Ephemeris time
The term ephemeris time can in principle refer to time in connection with any astronomical ephemeris. In practice it has been used more specifically to refer to:...
), which is a uniform measure of the passage of time (see also ΔT).
Later work
Wallace John EckertWallace John Eckert
Wallace John Eckert was an American astronomer, who directed the Thomas J. Watson Astronomical Computing Bureau at Columbia University which evolved into the research division of IBM.-Life:...
already became an instructor at Columbia University
Columbia University
Columbia University in the City of New York is a private, Ivy League university in Manhattan, New York City. Columbia is the oldest institution of higher learning in the state of New York, the fifth oldest in the United States, and one of the country's nine Colonial Colleges founded before the...
while finishing his PhD under Brown. Eckert would improve the pace of astronomical calculation by automating them with digital computers.
Brown retained his professorship at Yale until he retired in 1932. As well as continuing his work on the Moon, he also worked on the motion of the planet
Planet
A planet is a celestial body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.The term planet is ancient, with ties to history, science,...
s around the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...
. He co-wrote the book, Planetary Theory, with Clarence Shook, which contained a detailed exposition of resonance
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
in planetary orbits and examined the special case of the Trojan asteroid
Trojan asteroid
The Jupiter Trojans, commonly called Trojans or Trojan asteroids, are a large group of objects that share the orbit of the planet Jupiter around the Sun. Relative to Jupiter, each Trojan librates around one of the planet's two Lagrangian points of stability, and , that respectively lie 60° ahead...
s.
Private life
Brown never married, and for most of his adult life lived with his younger unmarried sister, Mildred, who kept house for him. A capable pianist fond of music, he also played chess to a high standard. He loved travelling, hill walking, and detective stories.A heavy smoker, Brown suffered from bronchial trouble for much of his life. He was afflicted by ill-health during most of the six years of his retirement, and died in New Haven, Connecticut
New Haven, Connecticut
New Haven is the second-largest city in Connecticut and the sixth-largest in New England. According to the 2010 Census, New Haven's population increased by 5.0% between 2000 and 2010, a rate higher than that of the State of Connecticut, and higher than that of the state's five largest cities, and...
in 1938.
Legacy
Brown's Tables were adopted by nearly all of the national ephemerides in 1923 for their calculations of the Moon's position, and continued to be used, eventually with some modification, until 1983. With the advent of digital computerComputer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
s, Brown's original trigonometrical expressions, given in the introduction to his 1919 tables (and from which the tables had been compiled), began to be used for direct computation instead of the tables themselves. This also gained some improvement in precision, since the tables themselves had embodied some minor approximations, in a trade-off between accuracy and the amount of labor need for computations using the tables in those days of manual calculation. By mid-century, the difference between Universal and Ephemeris Time had been recognised and evaluated, and the troublesome empirical terms were also removed. Further adjustments to Brown's theory were then also made in a later stage, arising from improved observational values of the fundamental astronomical constants used in the theory, and from re-working Brown's original analytical expansions to gain more precise versions of the coefficients used in the theory.
It was only as recently as in the ephemerides for 1984 that Brown's work was superseded: it was replaced by results gained from more modern observational data (including data from lunar laser ranging) and by altogether new computational methods for calculating the Moon's ephemeris.
Awards
- Gold Medal of the Royal Astronomical SocietyGold Medal of the Royal Astronomical Society-History:In the early years, more than one medal was often awarded in a year, but by 1833 only one medal was being awarded per year. This caused a problem when Neptune was discovered in 1846, because many felt an award should jointly be made to John Couch Adams and Urbain Le Verrier...
(1907) - Bruce MedalBruce MedalThe Catherine Wolfe Bruce Gold Medal is awarded every year by the Astronomical Society of the Pacific for outstanding lifetime contributions to astronomy. It is named after Catherine Wolfe Bruce, an American patroness of astronomy, and was first awarded in 1898...
(1920) - James Craig Watson MedalJames Craig Watson Medalthumb|right|400px|James Craig Watson MedalThe James Craig Watson Medal was established by the bequest of James Craig Watson, and is awarded by the U.S. National Academy of Sciences for contributions to astronomy.The recipients have been:-External links:*...
(1936)
Named after him
- The crater BrownBrown (crater)Brown is a lunar impact crater that is located in the southeast part of the Moon, to the southwest of the prominent ray crater Tycho. Northwest of Brown is the crater Wilhelm, and to the west is Montanari....
on the MoonMoonThe Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more... - AsteroidAsteroidAsteroids are a class of small Solar System bodies in orbit around the Sun. They have also been called planetoids, especially the larger ones...
1643 Brown1643 Brown1643 Brown is a main-belt asteroid discovered on September 4, 1951 by Reinmuth, K. at Heidelberg.- External links :*... - Brown lunation numberLunation NumberLunation Number is a number given to each lunation beginning from a certain one in history. There are several series of lunation numbers in use....
External links
- Bruce Medal page
- Awarding of Bruce Medal: PASP 32 (1920) 85
- Awarding of RAS gold medal: MNRAS 67 (1907) 300