Richard Dunthorne facts for kids

Richard Dunthorne (born 1711 – died 3 March 1775) was a smart English astronomer and surveyor. He worked in Cambridge helping Roger Long with astronomy and science. He also worked for many years as a surveyor for the Bedford Level Corporation.

Richard Dunthorne's Early Life and Work

Richard Dunthorne was born in a small town called Ramsey, Cambridgeshire. He came from a humble family and went to the local free grammar school. There, he caught the eye of Roger Long, who later became the head of Pembroke Hall, Cambridge. Long became Dunthorne's mentor.

Dunthorne moved to Cambridge, where Long first hired him as a "footboy." He got more education there, though it wasn't a regular university degree. Later, Dunthorne managed a school in Coggeshall, Essex. He then returned to Cambridge, where Long helped him get a job as a "butler" at Pembroke Hall. He kept this job for the rest of his life. His main work there was helping Long with important astronomy and science projects.

Dunthorne also worked for the Bedford Level Corporation for several years. This group managed water in the Fens, which are low, marshy lands. He started this work before 1761 and continued into the 1770s. In this role, Dunthorne helped survey the fens in Cambridgeshire. He also oversaw the building of locks near Chesterton on the River Cam.

Dunthorne and Long remained close friends and colleagues throughout their lives. Dunthorne even helped manage Long's will after he passed away.

Understanding the Moon's Movement: Lunar Tables

In 1739, Dunthorne published a book called Practical Astronomy of the Moon. This book contained special tables to help study the Moon's movement. These tables were based on Isaac Newton's ideas about how the Moon moves, which were published in 1702. Dunthorne's goal was to make it easier to test Newton's theories.

In 1746, Dunthorne wrote a letter explaining his work. He said he compared many recent observations of the Moon with Newton's theory. He wanted to see if the tables accurately showed the Moon's average speed and the way its orbit changed over many years.

Based on his careful observations, Dunthorne suggested some small changes to the numbers in Newton's theory.

The Moon's Apparent Speed Change

Dunthorne is especially remembered for his study of how the Moon's apparent speed changes in its orbit. Around 1695, Edmond Halley noticed something interesting. By comparing old records of eclipses with new observations, Halley thought the Moon was slowly speeding up in its orbit.

At that time, scientists didn't know that the Earth's rotation was actually slowing down. This slowing of Earth's spin makes the Moon *appear* to speed up. Dunthorne's calculations, using ancient eclipse records, confirmed this apparent speed increase. He was the first to measure this effect. He calculated it as +10 arcseconds per century squared in terms of the Moon's position. This number was quite close to what later scientists found, even a century later.

Dunthorne's Astronomical Writings

Dunthorne wrote several important papers for a scientific journal called Philosophical Transactions. These included:

• "On the motion of the Moon" (1746)
• "On the acceleration of the Moon" (1749)
• A letter "Concerning comets" (1751)

He also watched the rare events of Venus passing in front of the Sun in 1761 and 1769. In 1762, he published tables about the movement of Jupiter's moons.

Helping Sailors Find Their Way: The Nautical Almanac

On July 18, 1765, a group called the Board of Longitude hired Dunthorne. He became the first "Comparer of the Ephemeris and Corrector of the Proofs" for a new book. This book was called The Nautical Almanac and Astronomical Ephemeris.

The first issue of this Almanac came out with data for the year 1767. It was a big step forward! It gave sailors the tools they needed to use observations of the Moon to figure out their longitude at sea. Longitude tells you how far east or west you are. Dunthorne was the only person checking the first three issues (for 1767–69). After that, he continued as one of several checkers until the issue for 1776.

Dunthorne also created a method to help sailors make their Moon observations more accurate. This method removed errors caused by light bending (refraction) and the way things look from different places (parallax). Nevil Maskelyne included Dunthorne's method in a book called 'Tables requisite to be used with the Nautical Ephemeris.' This book was a companion to the Nautical Almanac.

In 1772, the Board of Longitude gave Dunthorne £50 for his work. This reward was for making the difficult calculations for "clearing the lunar distance" much shorter. Later, improvements were added, and "Dunthorne's improved method" was included in an 1802 edition.

Dunthorne is known for being the first to use advanced math (trigonometry) to solve problems related to lunar distances. He also created helpful tables for this purpose.

Dunthorne's Gifts to Cambridge

In 1765, Dunthorne planned and paid for the building of an observatory. This observatory was located at St. John's College. Dunthorne also gave valuable astronomical instruments to the college. The observatory was used until it closed in 1859.

A person who knew Dunthorne, Rev. William Ludlam, described him as someone "who without the benefit of an Academical education is arrived at such a perfection in many branches of learning, and particularly in Astronomy, as would do honour to the proudest Professor in any University." Ludlam also said Dunthorne was very generous.

Richard Dunthorne passed away in Cambridge. A crater on the Moon, called Dunthorne, is named after him.