The reflective alloy that powered Newton's first telescope
Discover the history of speculum, a unique metal alloy that served as the primary mirror for Sir Isaac Newton's original reflecting telescope. Professor Martyn Poliakoff explores this small but significant disc of metal at the Royal Society in London.
Speculum is a brittle bronze alloy composed of copper and tin, with some arsenic added to the mixture. Beyond its role in 17th-century astronomy, variations of this metal have appeared in ancient economies. In the 2nd century BCE, small cast pieces of speculum—containing 20 percent tin—were used to create coins in Ancient Britain that mimicked the bronze of Massilia. These coins circulated primarily in southeastern Britain during the early 1st century BCE.
Source: Amazing piece of metal (speculum)
