Astronomy - Mechanical Astronomical Instruments

 

 

Antikythera Mechanism

The movements of the stars and the planets have been studied in many cultures, to develop calendars and divide time into meaningful units.

Knowledge of the regular repeating cycles of the Sun and stars similarly provided a means of determining direction.

Accurate knowledge of time and direction is crucial in many cultures, and this need has driven people to harness their knowledge of the skies and invent precise instruments to measure and record it.

The Antikythera mechanism is an ancient Greek analogue computer used to predict astronomical positions and eclipses for calendar and astrological purposes decades in advance.

This artefact was retrieved from the sea in 1901, among wreckage retrieved from a wreck off the coast of the Greek island Antikythera.

The instrument is believed to have been designed and constructed by Greek scientists and has been variously dated to about 87 BC, or between 150 and 100 BC, or to 205 BC.

 

       

           Computer Graphic of Front                                     Computer Graphic of Rear

It is a complex clockwork mechanism composed of at least 30 meshing bronze gears.

A team led by Mike Edmunds and Tony Freeth at Cardiff University used modern computer x-ray and high resolution surface scanning to image inside fragments of the crust-encased mechanism and read the faintest inscriptions that once covered the outer casing of the machine.

Detailed imaging of the mechanism suggests that was able it to follow the movements of the Moon and the Sun through the zodiac, to predict eclipses and even to model the irregular orbit of the Moon.

All known fragments of the Antikythera mechanism are now kept at the National Archaeological Museum in Athens, along with a number of artistic reconstructions and replicas of the mechanism to demonstrate how it may have looked and worked.

The knowledge of this technology was lost at some point in antiquity, works with similar complexity did not appear again until the development of mechanical astronomical clocks in Europe in the fourteenth century.

 

An astrolabe is an elaborate inclinometer, historically used by astronomers and navigators to measure the altitude above the horizon of a celestial body, day or night. It can be used to identify stars or planets, to determine local latitude given local time.

An early astrolabe was invented in the Hellenistic civilization between 220 and 150 BC. The astrolabe was a marriage of the planisphere and effectively an analogue calculator capable of working out several different kinds of problems in astronomy.  

 

Astrolabe of Jean Fusoris, made in Paris, 1400

 

A spherical astrolabe from medieval Islamic astronomy, c. 1480, most likely Syria or Egypt, in the Museum of the History of Science, Oxford

 

An astronomical clock, is a clock with special mechanisms and dials to display astronomical information, such as the relative positions of the sun, moon, zodiacal constellations, and sometimes major planets.

In the 11th century, the Song dynasty Chinese horologist, mechanical engineer, and astronomer SuSong created a water-driven astronomical clock for his clock-tower of Kaifeng City.

Muslim astronomers and engineers also constructed a variety of highly accurate astronomical clocks for use in their observatories.

The early development of mechanical clocks in Europe is not fully understood, but there is general agreement that by 1300–1330 there existed mechanical clocks (powered by weights rather than by water and using an escapement).

Which were intended for two main purposes: for signalling and notification (e.g. the timing of services and public events), and for modelling the solar system.

 

Prague Astronomical Clock

The clock was first installed in 1410, making it the third-oldest astronomical clock in the world and the oldest clock still operating.

 

An orrery is a mechanical model of the Solar System that illustrates or predicts the relative positions and motions of the planets and moons, usually according to the heliocentric model.

It may also represent the relative sizes of these bodies; but since accurate scaling is often not practical due to the actual large ratio differences, a subdued approximation may be used instead.

Though the Greeks had working planetaria, the first orrery that was a planetarium of the modern era was produced in 1704, and one was presented to Charles Boyle, 4th Earl of Orrery – hence the name.

They are typically driven by a clockwork mechanism with a globe representing the Sun at the centre, and with a planet at the end of each of the arms.

In 1348, Giovanni Dondibuilt the first known clock driven mechanism which displays the ecliptical position of Moon, Sun, Mercury, Venus, Mars, Jupiter and Saturn according to the complicated Ptolemaic planetary theories.

The clock itself is lost, but Dondileft a complete description of the astronomic gear trains of his clock.

 

An orrery made by Robert Brettell Bate, circa 1812

Now in Thinktank, Birmingham Science Museum.

 

The Analytical Engine was a proposed mechanical general-purpose computer designed by English mathematician and computer pioneer Charles Babbage.

It was first described in 1837 as the successor to Babbage's difference engine, a design for a simpler mechanical computer.

The Analytical Engine is one of the most successful achievements of Charles Babbage.

 

Charles Babbage 26 December 1791 to 18 October 1871

He was an English polymath. A mathematician, philosopher, inventor and mechanical engineer,

The Analytical Engine incorporated an arithmetic logic unit, control flow in the form of conditional branching and loops, and integrated memory, making it the first design for a general-purpose computer that could be described in modern terms as Turing-complete.

Babbage was never able to complete construction of his Analytical Engine due to conflicts with his chief engineer and inadequate funding.

Late in his life, Babbage sought ways to build a simplified version of the machine, and assembled a small part of it before his death in 1871.

Babbage was instrumental in founding the Royal Astronomical Society in 1820, initially known as the Astronomical Society of London.

Its original aims were to reduce astronomical calculations to a more standard form, and to circulate data.

These directions were closely connected with Babbage's ideas on computation, and in 1824 he won its Gold Medal, cited "for his invention of an engine for calculating mathematical and astronomical tables".

In 1878, a committee of the British Association for the Advancement of Science described the Analytical Engine as "a marvel of mechanical ingenuity", but recommended against constructing it.

The committee acknowledged the usefulness and value of the machine, but could not estimate the cost of building it, and were unsure whether the machine would function correctly after being built.

Parts of Babbage's incomplete mechanisms are on display in the Science Museum in London.

In 1991, a functioning difference engine was constructed from Babbage's original plans.

Built to tolerances achievable in the 19th century, the success of the finished engine indicated that Babbage's machine would have worked.

 

The Science Museum's Difference Engine No. 2, Built From Babbage's Design

 

Augusta Ada King, Countess of Lovelace

10 December 1815 to 27 November 1852

Augusta Ada King, Countess of Lovelace (née Byron); was an English mathematician and writer, chiefly known for her work on Charles Babbage's proposed Analytical Engine.

She was the first to recognise that the machine had applications beyond pure calculation, and published the first algorithm intended to be carried out by such a machine.

Lovelace was the only legitimate child of poet Lord Byron and his wife Lady Byron. All of Byron's other children were born out of wedlock to other women.

Byron separated from his wife a month after Ada was born and left England forever four months later.

On 8 July 1835, she married William, 8th Baron King, becoming Lady King.

Her educational and social exploits brought her into contact with scientists such as Andrew Crosse, Charles Babbage, Sir David Brewster, Charles Wheatstone, Michael Faraday and the author Charles Dickens

Ada described her approach as "poetical science" and herself as an Analyst.

When Ada was twelve years old, this future "Lady Fairy", as Charles Babbage affectionately called her, decided she wanted to fly. Ada Byron went about the project methodically, thoughtfully, with imagination and passion. Her first step, in February 1828, was to construct wings. She investigated different material and sizes. She considered various materials for the wings: paper, oilsilk, wires, and feathers. She examined the anatomy of birds to determine the right proportion between the wings and the body.

When she was a teenager, her mathematical talents led her to a long working relationship and friendship with fellow British mathematician Charles Babbage, who is known as "the father of computers".

She was in particular interested in Babbage's work on the Analytical Engine. Lovelace first met him in June 1833, through their mutual friend, and her private tutor, Mary Somerville.

In 1840, Babbage was invited to give a seminar at the University of Turin about his Analytical Engine. Luigi Menabrea, a young Italian engineer and the future Prime Minister of Italy, transcribed Babbage's lecture into French.

Babbage's friend Charles Wheatstone commissioned Ada Lovelace to translate Menabrea'spaper into English. She then augmented the paper with notes, which were added to the translation.

Ada Lovelace spent the better part of a year doing this, assisted with input from Babbage.

Ada Lovelace's notes were considered to be the first published algorithm ever specifically tailored for implementation on a computer, and Ada Lovelace has often been cited as the first computer programmer for this reason.