Star Globes

Star Globes

Some historians regard early star globes or celestial spheres as forerunners of the modern planetarium. This is reasonable enough, since the motion of the seven wanderers (the Greek name for the Sun, the Moon and the five planets we can see naked-eye from the ground) can best be studied in relation to the background of “fixed” stars. The earliest extant star globe is that of the Atlante Farnesiano, a marble statue in the National Museum, Naples, Italy. The statue shows a kneeling figure of Atlas, some six feet high, whose broad shoulders support a celestial globe 26 inches in diameter.

Instead of showing stars, the globe has 42 constellation figures carved on its surface and raised lines for the celestial equator and the ecliptic, or apparent path of the sun. The arrangement of the figures relative to the lines suggests that the globe was made about 300 B.C.

A similar emphasis on constellation figures is found on later star globes, and also on star charts. To most early astronomers, constellation figures were an essential part of cosmography, or the charting of the heavens. The great Danish astronomer Tycho Brahe spared no expense to have them drawn on his large star globe, completed about 1595. They decorated the famous star atlas which John Flamsteed prepared in the following century, and almost overwhelm the stars in Bode’s large atlas of 1801. Indeed, they appeared on most popular star globes and charts right up to modern times.

Gottorp Globe. Gottorp Celestial and Terrestrial Globe, reconstructed. The Atwood Star Globe in the Museum of the Chicago Academy of Sciences

The Gottorp Globe

A bid disadvantage of a celestial globe is that any stars marked on it are seen from the outside and therefore in mirror-reverse to those seen in the real sky. Adam Oeschlager, court mathematician and librarian to Duke Frederick of Holstein-Gottorp, designed a hollow globe large enough for several people to sit inside and see objects painted on the inner surface. The globe made of copper and eleven feet in diameter, was prepared between 1654 and 1664 by Andreas Busch of Limberg, and assembled in the Duke’s castle of Gottorp.

The outer surface of this globe showed a map of the then-known world, and a wide horizontal circle enabled visitors to walk around the globe and examine the map in detail. The inner surface, lit by two oil lamps, showed gilded stars and constellation figures. Inside, a circular platform suspended from the axis of rotation held as many as ten people, and as the globe rotated, many stars and constellations drifted across the artificial sky in a way similar to that of the real sky.

In 1715 the globe was sent as a present to Czar Peter the Great, who in turn presented it to the Academy of Sciences of St. Petersburg. In 1747 it was so badly damaged by fire that only the axis and a few bars of a framework remained. It was rebuilt in 1778, given more up-to-grade features on both surfaces, and is now on display at the Lomonosov Museum, St. Petersburg.

The globes of Weigel, Long and Atwood

The next globes of this type were made by Erhard Weigel who, from 1653 until his death in 1699, was professor of mathematics in the University of Jena. One of them is said to have had a diameter of about eleven feet and to have been made of iron sheets. Weigel was proud of the fact that his artificial sky could be seen at all hours of the day and night, in sunshine and in rain. In the middle of the globe, above the observing platform, a small model earth added a nice touch of realism. The model earth contained working models of Aetna and Vesuvius which gave out steam, flames and “pleasant odours”. Meteors, rain, hail wind, thunder, and lighting could also be reproduced. If spectators experienced all these in succession they must have emerged with a greater sense of appreciation of the world outside.

One of Weigel’s smaller globes is now in the Franklin Institute, Philadelphia. It is about 18 inches in diameter and its stars are formed by little holes pierced in the globe. To see them the observer looks into the dark interior through one of several larger holes cut in comparatively starless areas.

Another similar globe was designed by Roger Long, Lowndes’ professor of astronomy at Cambridge, and erected in 1758 at Pembroke College, Cambridge, England. It had a diameter of 18 feet, could carry about thirty people on its platform, and had star represented by holes of various appropriate sizes. The whole device could be rotated by which and rackwork.

Long hoped that his “Uranium”, as he called it, would encourage popular interest in astronomy but attendances were poor and although a keeper was paid six pounds a year to keep the apparatus in good running order, it gradually fell into a state of disrepair. In 1874, no longer in use, it was broken up and sold as scrap metal.

A far more successful project was the globe constructed in 1911 for the Chicago Academy of Sciences after a design by W. W. Atwood, president of Clark University. This has a diameter of 15 feet and is still in a good state of preservation in the Academy building in Lincoln Park. Made of thin galvanized sheet-iron, it weighs only 500 pounds and rests at its equator on electrically driven rollers. The stars are formed by numerous holes, all carefully graded in size and properly positioned, and the sun is represented by a small electric light, movable along the ecliptic.