Galileo Telescope Reaches 400th Anniversary

This is a reconstruction of the Galileo telescope

The telescope was the first instrument to extend human senses, revolutionising our view of the heavens and our place in the world.
Exactly 400 years ago on 25 August 1609, the Italian astronomer, mathematician, physicist and philosopher Galilei Galileo showed Venetian merchants a new creation, a telescope, the instrument that was to bring him both scientific immortality and, more immediately, a whole lot of trouble.

Portrait of Galileo Galilei

The earliest known working telescopes appeared in 1608 and are credited to Hans Lippershey. Among many others who claimed to have made the discovery were Zacharias Janssen, spectacle-maker in Middelburg, and Jacob Metius of Alkmaar. The design of these early refracting telescopes consisted of a convex objective lens and a concave eyepiece. Galileo used this design the following year. Galileo who made the instrument famous. He constructed his first three-powered spyglass in 1609, presented an eight-powered instrument to the Venetian Senate in August, and turned a twenty-powered instrument to the heavens in October or November.

The telescope was one of the central instruments of what has been called the Scientific Revolution of the seventeenth century. It revealed hitherto unsuspected phenomena in the heavens and had a profound influence on the controversy between followers of the traditional geocentric astronomy and cosmology and those who favored the heliocentric system of Copernicus.