The Invention and Advance of Scientific Instruments

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The Invention and Advance of Scientific Instruments

Overview

The study of the heavens produced the earliest surviving scientific instruments, and the need for accurate astronomical sightings and calculations provided the stimulus for technological and theoretical innovation that would allow mechanization and development in many other fields. However, the history of scientific instruments is patchy at best, as most devices were constructed of cheap materials such as wood, or even paper, and consequently have not survived. Only the most permanent structures or the most grand and expensive, made from metals or stone, have survived.

Background

Some of the earliest scientific instruments were markings on rocks that showed the position of the sunrise on a certain day of the year. Later, astronomical constructions were made that ranged from simple sundials to complex structures such as Stonehenge. In ancient Mesopotamia mudbrick buildings were designed specifically for observation of the stars and planets. The Egyptian pyramids were built with perfectly aligned north-south and east-west positions. Such accurate construction was achieved using a star-sighting tool called a merkhet, which enabled the direction of the north star to be found with a plumb line. Water clocks were used by the Egyptians and the Babylonians as far back as 1500 b.c. Such clocks were used for ceremonial purposes, and in the Greek and Roman legal systems for timing the speeches of those in court.

The Greeks used the study of mathematics to improve on earlier tools. Ptolemy (second century a.d.) modified the sundial so that it marked out equal hours throughout the year by angling the pointer (or gnomon) parallel to the earth's axis of rotation. The Greeks also introduced new tools in astronomy, from sophisticated spheres that demonstrated the motion of the heavens to small handheld devices.

However, the collapse of the Roman Empire saw much of the knowledge of the ancients destroyed, lost, or scattered. Little of the ancient Greek learning was preserved in Europe, and only a fraction was translated into simple Latin texts. The medieval European audience was not interested in the complex mathematics and mechanical sophistication of the ancient writings, and so the complexity of ancient astronomy and mathematics was lost.

Impact

Elsewhere, however, there was a growing demand for more complex learning, especially in the fields of mathematics and astronomy. Chinese, Hindu, and Arab scholars actively sought out new knowledge, resulting in cross-cultural exchanges of ideas. Arabic scholars were especially well located, with access to the knowledge of the Babylonians, Indians, Chinese, and Greeks. They procured texts by any means they could, the most important example being the acquisition of Ptolemy's Algamest in a peace treaty with the Byzantines. This single work contained sophisticated geometry and descriptions of a number of astronomical instruments.

Arab astronomers and timekeepers modified the instruments they found and created many new ones. The sundial was modified along the lines suggested by Ptolemy, and this method and its geometry perfected. Eventually this information was translated into Latin, and the sundial became the simplest and most popular method of timekeeping, at least when the sun was shining.

Less susceptible to interruption were water clocks, which used the steady release of water to display the hours. In India and China many complex and ornamental designs were constructed, some of immense scale. In 1086 a Chinese diplomat and administrator, Su Sung (c. 1086), began work on a giant astronomical clock powered by water. It reproduced the movements of the Sun, Moon, and Earth, and weighed many tons, occupying a tower over 40 ft (12.2 m) high. Su Sung's astronomical clock represents the best and worst of Chinese technology. The clock was a magnificent wonder, yet did not function well over extended periods. In Chinese science the pretence of accuracy was more important than mechanical precision itself. Astronomy was extremely important in Chinese life, so important that political considerations overrode scientific ones. Chinese official astronomers contrived their results, and relied on old texts, rather than actual observations using their instruments. Much of Chinese learning was destroyed in political purges, and their mighty instruments and clocks decayed and ceased to function.

Islamic water clocks were common in large towns beginning in the ninth century. In 1050 a large water clock was constructed in Toledo, Spain, which told the hours of day and night and the phases of the Moon. Larger and more sophisticated models were later developed.

European water clocks may have been copied from either Arabic models or from the Roman tradition. The earliest date from around the tenth century. By the end of the twelfth century there was a guild of clockmakers established in Cologne, and water clocks became more common. However, it is the development of the mechanical clock for which Europe is famous. Some mechanical developments were already obvious in complex water clocks throughout the world. In Europe, however, there emerged a conscious drive to develop a weight-driven clock during the middle of the thirteenth century. Richard of Wallingford (1291?-1336?) appears to have been the first to solve the problems of keeping regular time with a weight-driven device, constructing a working piece in 1327. Shortly after, Giovanni Dondi (1318-1389) constructed a sophisticated astronomical clock using a similar mechanism. Mechanical clocks quickly spread across Europe, and most major towns built a civic clock out of local pride and a desire to regulate the hours of the day.

Astronomical clocks were based on a device known as an armillary sphere. This was an instrument for representing the motion of the stars, made from a number of rings that could be rotated around an axis. On the rings were drawn various bright stars, and these could be sighted relative to a fixed horizon. Such instruments were described in the writings of Ptolemy and other Greek astronomers. Islamic astronomers developed complex and accurate spheres, and used them for both demonstration purposes and as an aid to observation. A related instrument was the equatorium, which allowed the user to calculate the position of a planet for a given time. The earliest written description of an equatorium dates from the late eleventh century. European universities introduced them as teaching aids in the twelfth century.

By far the most common and versatile astronomical instrument of the period was the astrolabe, a two-dimensional representation of the night sky. The origins of the instrument are now lost, but an anecdote from the medieval period playfully suggests that, while riding on a donkey one day, Ptolemy dropped an armillary sphere, which the donkey stood on, thereby creating the first astrolabe. Essentially the astrolabe was a flat model of the universe that could be held in the hand, although some Arab instruments were made very large in order to improve their accuracy. An astrolabe consists of a movable framework with markings representing various bright stars, and a fixed plate that acts as the horizon for the observers latitude, combined with pointers and a scale on the back. The astrolabe could be used to show the time, or when a star would rise, set, or be an its highest point in the night sky, as well as a number of other uses.

Astrolabes were originally only useful for a specific latitude, but this was solved by making many discs for different latitudes. Later, a more intricate solution was found by al-Zarqali (1028-1087), whereby a single disc could represent any given latitude. Arab astronomers made many other modifications and expanded the usefulness of the astrolabe. For example, they were able to make it capable of telling the time of day as a function of solar latitude. These daytime markings are found on all early European astrolabes, even though the method used does not give accurate results for northern latitudes. This reveals the reliance Europeans had on Arab technology, slavishly copying every detail, even when unnecessary.

Slowly, however, European instrument-makers improved their skills and developed new innovations. The mariner's astrolabe was introduced by Portuguese sailors in the fifteenth century in order to help them explore and map the African coast with some safety and accuracy. This device was a simplified version of the astronomer's astrolabe, and was used to calculate latitude by observations of the Sun at local noon, or by sighting bright stars. Such astrolabes were still in use in the eighteenth century.

Another common astronomical instrument was the quadrant (or quarter-circle), which calculated the angle of a star or the Sun. Islamic astronomers improved upon the design of ancient quadrants, making them bigger and more versatile.

Collections of instruments were gathered together in observatories in China and the Arab world. The most famous observatory of the period was at the Arab town of Maragha (in modern Iran), which flourished in the thirteenth century. It contained large and accurate instruments, and attracted many Muslim, Christian, Jewish, and Chinese astronomers.

The measurements made at observatories were used to improve existing knowledge of the heavens, to calculate astronomical tables listing the positions of planets, the lunar phases, when eclipses would occur, and other events. The most popular of these tables were also some of the earliest, calculated by al-Battani (858-929). His astronomical tables were adopted by Europeans and used until the middle of the fifteenth century. Many tables, almanacs, and calendars were written by Islamic, Chinese, Indian, and European scholars, and often these scientific writings became embroiled in political arguments. European astronomers of the period were almost exclusively concerned with calendar reform, and the debates over the "correct" dates had a strong religious tone, especially in the computation of when Easter should be celebrated.

The development and innovation in time-keeping and astronomical instruments had wide implications in many other areas. Navigation benefited directly from both astronomical and timekeeping devices, enabling the European explorers of the fifteenth century to estimate their position with some degree of accuracy. Mechanical developments in other fields also developed from the pioneering work of early instrument-makers. From the ingenious automata, designed for the entertainment of rich patrons, to the practical developments in later centuries of complex engineering tools in industry, the beginnings of precision devices and machinery can be found in the efforts of early clockmakers and astronomers to make their instruments more accurate and versatile.

DAVID TULLOCH