A History Of The Telescope – How Lenses Changed Science

This article forms part of the IFLScience exciting editorial calendar for 2023.

There’s much that we take for granted in our modern world. For example, have you ever considered the history of lenses, and how they have extended our view of the universe? The development of this subtle technology not only allows us to examine the very small or to peer into the vastness of space, but they also play an important role in our everyday lives, such as in our cameras, on cinema projectors, or simply as the glass in our spectacles. Lenses are extremely valuable, and they have played an important role in the History of Science, not least in the development of modern telescopes.

The birth of the telescope

Telescopes are arguably one of the most iconic scientific instruments ever invented. Few other objects are so easily identifiable, both in appearance and in terms of their intended use. Telescopes – those wondrous optical tubes – have changed the way we understand our world and its place in the cosmos. To be sure, their development would not have been possible without far older advances in lens technologies and accompanying theories of optics, but this deeply fascinating and detailed history is too expansive to be captured here. Nevertheless, we can start to think about the story of telescopes, an instrument brought into existence by this history, as starting in the late 16th and early 17th centuries. 

As with other early technologies involving lenses, we are not certain who their first inventor was, but we do know that in 1608, a Dutch spectacle maker called Hans Lipperhey announced a new instrument that used lenses to make distant objects appear closer. This seems to be the first evidence of a telescope in historical record. Lipperhey applied for a patent for his new device, which circulated across Europe allowing other early “scientists” to experiment with their own versions. One such experimenter was the Italian polymath Galileo Galilei who heard about Lipperhey’s invention while in Venice in June 1609.

The early history of the telescope is tightly bound with the career of Galileo, whose work had lasting consequences for our understanding of the universe. Often remembered as a heroic figure who challenged the established worldview of his day, Galileo’s story is actually an important example of how concurrent developments in scientific thinking, technological development, and networks of knowledge come together. 

Following Lipperhey’s example, Galileo decided to make his own telescope and to turn its vision-enhancing powers to the heavens. Although he was not the only astronomer to do this at the time, the success of his telescope won him a lifetime lectureship. He then set about refining his instrument. The original telescope, like Lipperhey’s, offered three times magnification, but his subsequent versions first offered eight times and eventually 30 times magnification. This provided unprecedented views of celestial objects and changed everything. Ultimately, Galileo was not alone in utilizing telescopes for this purpose, but he was very quick at publishing his results and understanding their implications.

 His most crucial observations included the revelation that, contrary to Aristotelian principles, the Moon was not a smooth sphere but a rough textured object like the Earth, with its own depressions and mountains. He also identified the existence of four previously unknown moons orbiting Jupiter, which was the first-time objects had ever been seen to orbit another body besides the Earth or Sun. Then there were the phases of Venus, which could not be accommodated by the traditional Earth-centric model of the universe. 

This led Galileo to champion the Copernican heliocentric model, which had been published by the Polish polymath in 1543. Like a few others at the time, Galileo also observed sunspots on the surface of the Sun and interpreted them as blemishes that moved due to its rotation – this was another nail in the coffin for the Aristotelian view of a perfect unchanging cosmos.  

 Refining things   

In 1611, Johannes Kepler, inspired by Lipperhey and Galileo’s work, designed and built his own telescope – the famous Keplerian Telescope. This device was developed independently of its predecessor’s designs and used convex lenses that allowed viewers to see far larger fields of view (though it also inverted the image). Kepler’s telescope is noteworthy because it achieved a much greater level of magnification than Galileo’s versions, which enabled him to not only confirm many of the Italian’s observations but to make his own. He recorded these in his Conversation with the Starry Messenger. 

Today, Kepler is remembered for his contributions to astronomy, but he was also extremely influential in the field of optics. In fact, his groundbreaking Astronomiae Pars Optica has earned him the title of “Father of Modern Optics”. His work would go on to have important implications for subsequent discoveries by individuals like Isaac Newton, who continued to develop and improve these early telescopes as well as the laws of optics that underpinned them. 

 Bigger is better, right?

One of Newton’s important contributions to the development of telescopes had significant implications for traditional refraction devices. Instead of using lenses, Newtonian Telescopes (the first of which was built in 1668) relied on mirrors instead. Essentially, a large concave mirror would focus light onto a smaller one, which then projected the image onto an eyepiece on the side of the instrument. This alteration overcame a persistent issue that occurred in traditional refraction telescopes, what is known as chromatic aberration – an effect that occurs when a lens cannot correctly refract all the wavelengths of color in the same point.  

To be sure, Newton was not the first person to consider reflective telescopes, but his version had some important advantages. It was cheaper, did not produce the chromatic aberration, and was both easier to put together and to carry. However, Newton’s view that reflective telescopes were the only way around the aberration issues was soon proven wrong by Chester Moore Hall, who, in 1729, developed a new lens that consisted of two types of glass that were cemented together. This modification overcame the same issue and proved that refraction telescopes were still viable. 

Now, a kind of arms race kicked off within astronomy and telescope manufacturing communities, where individuals competed to create bigger and bigger versions of these devices. One of the most famous was William Herschel’s 12-meter (40-foot) reflector telescope that was built in 1789. Over the next century, other larger devices were built until 1897, when the Yerkes Observatory in Wisconsin, US, opened with a massive 100-centimeter (40-inch) refractive lens that was, at the time, the largest of its kind in the world. This telescope is very much still in use today, but eventually, as we moved into the 20th century, the race for bigger and better telescopes was largely won by reflective versions. 

Today, most telescopes used within observatories or on space stations rely on mirrors rather than lenses and the race to build the biggest devices is very much over. Nevertheless, the significant advances made in optics and accompanying lens-making practices that were developed and honed in previous centuries have provided the grounds upon which our current efforts to explore the universe rest.  

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.

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