Francis Baily

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Francis Baily
Francis Baily (The Royal Astronomical Society).jpg
Royal Astronomical Society portrait
Born(1774-04-28)28 April 1774
Died30 August 1844(1844-08-30) (aged 70)
London, England
Resting place St Mary's Church in Thatcham
Citizenship British
Known for Baily's beads
President of the Royal Astronomical Society
Awards Gold Medal of the Royal Astronomical Society (1827 & 1843)
Scientific career
Fields Astronomy

Francis Baily (28 April 1774 30 August 1844) was an English astronomer. He is most famous for his observations of "Baily's beads" during an eclipse of the Sun. Baily was also a major figure in the early history of the Royal Astronomical Society, as one of the founders and president four times.

Astronomer Scientist who studies celestial bodies

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, planets, moons, comets, 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, which studies the Universe as a whole.

The Baily's beads effect, or diamond ring effect, is a feature of total and annular solar eclipses. As the Moon covers the Sun during a solar eclipse, the rugged topography of the lunar limb allows beads of sunlight to shine through in some places while not in others. The effect is named after Francis Baily, who explained the phenomenon in 1836. The diamond ring effect is seen when only one bead is left, appearing as a shining "diamond" set in a bright ring around the lunar silhouette.

Eclipse astronomical event where one body hides another

An eclipse is an astronomical event that occurs when an astronomical object is temporarily obscured, either by passing into the shadow of another body or by having another body pass between it and the viewer. This alignment of three celestial objects is known as a syzygy. Apart from syzygy, the term eclipse is also used when a spacecraft reaches a position where it can observe two celestial bodies so aligned. An eclipse is the result of either an occultation or a transit.



Baily was born at Newbury in Berkshire in 1774 to Richard Baily. [1] After a tour in the unsettled parts of North America in 1796–1797, his journal of which was edited by Augustus de Morgan in 1856, Baily entered the London Stock Exchange in 1799. The successive publication of Tables for the Purchasing and Renewing of Leases (1802), of The Doctrine of Interest and Annuities (1808), and The Doctrine of Life-Annuities and Assurances (1810), earned him a high reputation as a writer on life-contingencies; he amassed a fortune through diligence and integrity and retired from business in 1825, to devote himself wholly to astronomy. [2]

Newbury, Berkshire civil parish and town in Berkshire, England

Newbury is a market town in Berkshire, England, which is home to the administrative headquarters of West Berkshire.

London Stock Exchange Stock exchange in the City of London

London Stock Exchange is a stock exchange located in the City of London, England. As of April 2018, London Stock Exchange had a market capitalisation of US$4.59 trillion. It was founded in 1571, making it one of the oldest exchanges in the world. Its current premises are situated in Paternoster Square close to St Paul's Cathedral in the City of London. It is part of London Stock Exchange Group (LSEG).

Astronomical work

By 1820, Baily had already taken a leading part in the foundation of the Royal Astronomical Society, [3] and he received its Gold Medal in 1827 [4] for his preparation of the Society's Catalogue of 2881 stars (Memoirs R. Astr. Soc. ii.). [2] Later, in 1843, he would win the Gold Medal again. [4] He was elected as President of the Royal Astronomical Society four times, with two-year terms each (1825–27, 1833–35, 1837–39 and 1843–45). [3] [5] No other person has served in the position more than Baily's four times (a record he shares with George Airy), whilst his eight years in the post are a record. [5]

Royal Astronomical Society learned society

The Royal Astronomical Society (RAS) is a learned society and charity that encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science. Its headquarters are in Burlington House, on Piccadilly in London. The society has over 4,000 members, termed Fellows, most of them professional researchers or postgraduate students. Around a quarter of Fellows live outside the UK. Members of the public who have an interest in astronomy and geophysics but do not qualify as Fellows may become Friends of the RAS.

Gold Medal of the Royal Astronomical Society award

The Gold Medal of the Royal Astronomical Society (RAS) is the highest award given by the RAS. The RAS Council have "complete freedom as to the grounds on which it is awarded" and as such it can be awarded for any reason. Past awards have been given for "outstanding personal researches in the fields of astronomy and geophysics" as well as general contributions to astronomy and geophysics "that may be made through leadership in research programmes, through education and through scientific administration". It has been awarded both for research that has taken a lifetime and for specific pieces of research.

The President of the Royal Astronomical Society chairs the Council of the Royal Astronomical Society (RAS) and its formal meetings. They also liaise with government organisations, similar societies in other countries, and the International Astronomical Union on behalf of the UK astronomy and geophysics communities. Future presidents serve one year as President Elect before succeeding the previous president.

The reform of the Nautical Almanac in 1829 was set on foot by his protests. He was elected a Foreign Honorary Member of the American Academy of Arts and Sciences in 1832. [6] He recommended to the British Association in 1837, and in great part executed, the reduction of Joseph de Lalande's and Nicolas de Lacaille's catalogues containing about 57,000 stars; he superintended the compilation of the British Association's Catalogue of 8377 stars (published 1845); and revised the catalogues of Tobias Mayer, Ptolemy, Ulugh Beg, Tycho Brahe, Edmund Halley and Hevelius (Memoirs R. Astr. Soc. iv, xiii.). [2]

American Academy of Arts and Sciences United States honorary society and center for independent policy research

The American Academy of Arts and Sciences is one of the oldest learned societies in the United States. Founded in 1780, the Academy is dedicated to honoring excellence and leadership, working across disciplines and divides, and advancing the common good.

Tobias Mayer German astronomer

Tobias Mayer was a German astronomer famous for his studies of the Moon.

Ptolemy 2nd-century Greco-Egyptian writer and astronomer

Claudius Ptolemy was a Greco-Roman mathematician, astronomer, geographer and astrologer. He lived in the city of Alexandria in the Roman province of Egypt, wrote in Koine Greek, and held Roman citizenship. The 14th-century astronomer Theodore Meliteniotes gave his birthplace as the prominent Greek city Ptolemais Hermiou in the Thebaid. This attestation is quite late, however, and, according to Gerald Toomer, the translator of his Almagest into English, there is no reason to suppose he ever lived anywhere other than Alexandria. He died there around AD 168.

His observations of "Baily's Beads", during an annular eclipse of the sun on 15 May 1836, at Inch Bonney in Roxburghshire, started the modern series of eclipse expeditions. The phenomenon, which depends upon the irregular shape of the moon's limb, was so vividly described by him as to attract an unprecedented amount of attention to the total eclipse of 8 July 1842, observed by Baily himself at Pavia. [2]

Roxburghshire Historic county in Scotland

Roxburghshire or the County of Roxburgh is a historic county and registration county in the Southern Uplands of Scotland. It borders Dumfriesshire to the west, Selkirkshire to the north-west, and Berwickshire to the north. To the south-west it borders Cumberland and to the south-east Northumberland, both in England.

Pavia Comune in Lombardy, Italy

Pavia is a town and comune of south-western Lombardy in northern Italy, 35 kilometres south of Milan on the lower Ticino river near its confluence with the Po. It has a population of c. 73,000. The city was the capital of the Kingdom of the Lombards from 572 to 774.

Baily's beads four seconds before totality August 21 2017 solar eclipse baily beads TLR2.jpg
Baily's beads four seconds before totality

In other work, he completed and discussed H. Foster's pendulum experiments, deducing from them an ellipticity for the earth of 1/289.48 (Memoirs R. Astr. Soc. vii.). This value was corrected for the length of the seconds-pendulum by introducing a neglected element of reduction, and was used, in 1843, in the reconstruction of the standards of length. His laborious operations for determining the mean density of the earth, carried out by Henry Cavendish's method (1838–1842), yielded the authoritative value of 5.66. [2]

Henry Foster was a British naval officer and scientist who took part in expeditions to both the Arctic and Antarctic, and made various notable scientific observations.

Henry Cavendish British natural philosopher, scientist, and an important experimental and theoretical chemist and physicist

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Baily died in London on 30 August 1844 and was buried in the family vault in St Mary's Church in Thatcham. His Account of the Rev. John Flamsteed (1835) is of fundamental importance to the scientific history of that time. It included a republication of the British Catalogue. [2]

The lunar crater Baily was named in his honour, as was the rigid and thermally insensitive alloy used to cast the 1855 standard yard (Baily's metal, 16 parts copper, 2.5 parts tin, 1 part zinc) and a local primary school in his home town of Thatcham (Francis Baily CofE Primary School).[ citation needed ]

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  1. Hockey, Thomas (2009). The Biographical Encyclopedia of Astronomers. Springer Publishing. ISBN   978-0-387-31022-0 . Retrieved 22 August 2012.
  2. 1 2 3 4 5 6 Wikisource-logo.svg One or more of the preceding sentences incorporates text from a publication now in the public domain : Chisholm, Hugh, ed. (1911). "Baily, Francis"  . Encyclopædia Britannica . 3 (11th ed.). Cambridge University Press. p. 221. This also cites
    • J. Herschel's Memoir of F. Baily, Esq. (1845), also prefixed to Baily's Journal of a Tour, with a list of his writings (see Further reading).
    • Month. Not. R. Astr. Soc. xiv. 1844.
  3. 1 2 Dreyer, John L. E.; Turner, Herbert H. (1923). History of the Royal Astronomical Society, 1820–1920. 1. London: Royal Astronomical Society.
  4. 1 2 "Gold Medal Winners" (PDF). RAS. 2014. Retrieved 9 January 2015.[ permanent dead link ]
  5. 1 2 "List of Presidents and Dates of Office". A brief history of the RAS. Royal Astronomical Society. Retrieved 10 September 2012.
  6. "Book of Members, 1780–2010: Chapter B" (PDF). American Academy of Arts and Sciences. Retrieved 5 May 2011.

Further reading