The Astronomer

Astronomers

THE MAIN DIFFERENCE BETWEEN ASTRONOMERS and most other scientists is that astronomers can only conduct direct experiments in the solar system-by sending spacecraft. They cannot experiment on stars and galaxies. The key to most astronomy is careful and systematic observing. Astronomers must watch and wait for things to happen. Early astronomers could do little more than plot the positions of the heavenly bodies, follow their movements in the sky, and be alert for unexpected events, such as the arrival of a comet. From the 19th century, astronomers began to investigate the physics of the universe by analyzing light and other radiation from space. But the sorts of questions astrophysicists still try to answer today are very similar to the questions that puzzled the earliest Greek philosophers-what is the universe, how is it shaped, and how do I fit into it?

Fashionable Amateurs

By the 18th century the science of the stars became an acceptable pastime for the rich and sophisticated. The large number of small telescopes that survive from this period is evidence of how popular amateur astronomy had become.

The Nautical Almanac

First published in 1766, The Nautical Almanac provides a series of tables showing the distances between certain key stars and the Moon at three-hour intervals. Navigators can use the tables to help calculate their longitude at sea, when they are out of sight of land (p.27).

First Astronomer Royal

England appointed its first Astronomer Royal, John Flamsteed (1646-1719), in 1675. He lived and worked at the Royal Observatory, Greenwich, built by King Charles II of England in the same year.

In the Family

When the Observatoire de Paris was founded in 1667, the French King Louis XN called a well-known Bolognese astronomer, Gian Domenico Cassini (1625-1712), to Paris to be the observatory's director. He was followed by three generations of Cassinis in the position: Jacques Cassini (1677-1756); Cesar-Fran~ois Cassini de Thury (1714-1784), who produced the first modern map of France; and Jean-Dominique Cassini (1748-1845). Most historians refer to this great succession of astronomers simply as Cassini 1, Cassini II, Cassini III, and Cassini N.

Astronomy in Russia

The Russian astronomer Mikhail Lomonosov (1711-1765) was primarily interested in problems relating to the art of navigation and fixing latitude and longitude. During his observations of the 1761 transit ofVenus (pp.46-47), he noticed that the planet seemed "smudgy," and suggested that Venus had a thick atmosphere, many times denser than that of Earth.

Star Clock (1815)

One of the primary aspects of positional astronomy is measuring a star's position against a clock. This ingenious clock has the major stars inscribed on the surface of its rotating face. Placing pegs in the holes near the stars to be observed causes the clock to chime when the star is due to pass the local meridian.

Napier's Bones

One of the problems that has always faced astronomers is the seemingly endless calculation that is needed to pinpoint the true positions of the stars and the planets. In 1614 John Napier (1550-1617), Laird of Merchiston in Scotland, published the first full set of logarithmic tables. In 1617 he invented a series of rods engraved with numbers in such a way that they could be set side by side and used for doing complex multiplications and divisions. The rods, usually made of ivory or bone, were soon known as "Napier's bones".

Family Loyalty

Caroline Herschel (1750-1848) was astronomical assistant and housekeeper to her brother, the great observational astronomer Sir William Herschel (p.54). While he was busy grinding mirrors-a delicate task that could take up to 16 hours- Caroline would spoon-feed him as he worked to keep up his strength. As an astronomer of note in her own right, she discovered eight comets and was an influence on her brilliant nephew John (1792-1871), who became famous for his survey of the southern hemisphere.

Astronomical Calculator

In the 19th century, instrument makers began to construct mechanical calculators for complex, often repetitive, mathematical functions. With one turn of the handle, this calculator can produce a figure with up to 42 places.

The Astronomical Chair

The astronomical chair is quite a late invention. When astronomers worked with big mural quadrants (p.25), they needed a pair of steps to run up and down in order to reach the eyepiece of the telescope. It was not until the invention of the transit instrument in the late 17th century that astronomers could lie back and look at the stars. Chairs with padding on them did not appear for another 50 years.

Keeping Warm

Being an astronomer was not a glamorous life. Before the advent of the camera, the job involved spending long hours in a roofless observatory, peering through an eyepiece at the stars, and making copious notes of obselvations. Suitable warm clothing would have been essentiaL