Over the years archaeologists have been discovering greater numbers of ancient lenses, and historians more and more references to their use in ancient times, so that inevitably it is being asked if they were then able to use them for astronomy purposes.
History Of The Lens
According to Roman historian Pliny, glass-making was discovered accidentally by the Phoenicians around 5000 BC, while cooking on the desert sand. However, the earliest man-made glass objects were found later around 3500 BC in Egypt and Mesopotamia, with lenses no doubt being made soon after the discovery.
The earliest known lens currently unearthed is the Nimrud lens (750 BC) found at the Assyrian palace of Nimrud in modern-day northern Iraq. It is believed to have been used as a magnifying glass, or as a burning-glass to start fires. Lenses were certainly well known by the time of the Greeks, with even the dramatist, Aristophanes, referring to them in his Comedy of the Clouds in 424 BC:
Strepsiades: “Have you ever seen a beautiful, transparent stone at the druggists’, with which you may kindle fire?”
Socrates: “You mean a crystal lens.”
Uses of these early lenses included starting fires and cauterizing wounds, although their magnifying properties would obviously have been known. However, in the 1st century AD we find the first written record of magnification with the Roman Seneca the Younger explaining:
“Letters, however small and indistinct, are seen enlarged and more clearly through a globe or glass filled with water.”
The most powerful ancient lens yet discovered was found in Crete dating back to the 5th century BC and had the ability to magnify clearly up to seven times and even as much as twenty times, albeit with considerable distortion.
It has even been suggested that a piece of Greek pottery discovered dating back to 4th century BC depicts a man using an early telescope and that ancient people were able to connect two lenses inside a simple tube to make an early, crude telescope. However, making lenses and a telescope useful for astronomy purposes requires a level of expertise and precision probably undiscovered by the ancients, although it is good to keep an open mind on the subject.
Telescopes are generally accepted to have been invented in the 16th century by Dutch spectacle-makers, although there is evidence of the instrument being conceived of much earlier. English philosopher Roger Bacon, (1214–1294), for instance, gave a proposal for a telescope in his masterpiece Opus Majus:
“For we can so shape transparent bodies, and arrange them in such a way with respect to our sight and objects of vision, that the rays will be reflected and bent in any direction we desire, and under any angle we wish, we may see the object near or at a distance … So we might also cause the sun, moon and stars in appearance to descend here below.”
Bacon was subsequently imprisoned for his heretical views and indulging in magical practices. Hence, it was only towards the end of the Renaissance era in 17th century Europe and the Scientific Revolution which ensued that modern telescopes started being used to study the night sky.