The Glass Eye: the story of the telescope 

For as long as humans have been on Earth we’ve been trying to see further. We’ve been up trees, climbed hills, and built a variety of stony highpoints to gaze inquisitively over the landscape. And then we discovered that glass, curved one way or another, could enlarge our view. And we became entranced with the details of distance.

The history of the telescope is a fascinating journey that spans centuries, leading ultimately to remarkable advancements in our understanding of the universe. From its humble beginnings as a simple optical instrument to its modern use in space, the telescope has revolutionised astronomy and opened up new frontiers of exploration.

The history of curiosity

• The earliest evidence of optical devices used for magnifying images dates back to ancient times. The ancient Greeks, including philosophers such as Aristotle and Plato, experimented with curved glass and water-filled bowls to observe distant objects. However, it was in the early 17th century that significant breakthroughs in telescope design occurred, leading to the birth of modern astronomy.

• In 1608, Dutch spectacle maker Hans Lippershey invented the first refracting telescope, which utilised lenses to gather and focus light. These early refracting telescopes suffered from chromatic aberration, causing distortions and colour fringing. Nonetheless, they allowed astronomers to observe celestial objects with much greater detail than ever before.

• In 1609 Galileo Galilei, an Italian astronomer and physicist, constructed his own refracting telescope, turned it towards the sky, and proceeded to make ground-breaking discoveries, including the observation of craters on the Moon, the phases of Venus, and the moons of Jupiter. Galileo's observations provided compelling evidence to support the model proposed by Copernicus that the sun centred the solar system, challenging the view of the time that the Earth was the centre of everything.

•  Over time, astronomers sought to overcome the limitations of refracting telescopes, leading to the development of reflecting telescopes. In the mid-17th century, Sir Isaac Newton constructed the first practical reflecting telescope. Instead of using lenses, Newton's design employed a curved mirror to gather and focus light. Reflecting telescopes eliminated chromatic aberration and offered larger apertures, enabling astronomers to gather more light and observe fainter objects.

• In the 18th and 19th centuries, astronomers continued to refine and improve telescope designs. Notable advancements included the achromatic lens, which reduced chromatic aberration in refracting telescopes, and the equatorial mount, which allowed telescopes to track the motion of celestial objects more accurately. These innovations expanded the capabilities of telescopes and facilitated significant astronomical discoveries, including the discovery of Uranus by William Herschel in 1781.

• The 20th century witnessed further advancements in telescope technology, leading to the emergence of new fields of astronomy. In 1930, Karl Jansky discovered radio waves emanating from space, leading to the development of radio telescopes. Radio telescopes detect and analyse radio waves emitted by celestial objects, providing insights into phenomena such as pulsars, quasars, and cosmic microwave background radiation.

• Another breakthrough in telescope technology came with the advent of space-based observatories. The Earth's atmosphere distorts and blocks certain wavelengths of light, limiting the capabilities of ground-based telescopes. Space telescopes, on the other hand, operate above the Earth's atmosphere, offering clear and uninterrupted views of the cosmos.

The great telescopes peering out on the universe

In 1990, the Hubble Space Telescope (HST) was launched, marking a new era in space-based astronomy. The HST has provided breath-taking images and ground-breaking scientific discoveries, including the capacity to determine the age of the universe. The Hubble has given us the opportunity to observe distant galaxies, explore the formation of stars, and discover new planetary systems. The HST's ability to observe in ultraviolet, visible, and near-infrared wavelengths, has revolutionised our understanding of the cosmos.

Subsequent space telescopes, such as the Chandra X-Ray Observatory and the Spitzer Space Telescope, have focused on specific wavelengths of light, enabling scientists to study phenomena that are invisible or difficult to observe with traditional telescopes. These space observatories have expanded our knowledge of black holes, supernovae, and the structure of galaxies.

In recent years, advancements in technology have allowed for the development of even more powerful and specialised space telescopes. The James Webb Space Telescope (JWST), launched 2021, is the most advanced space telescope to date. The JWST operates in the infrared spectrum and is set to provide unprecedented views of the early universe, exoplanets, and the formation of stars and galaxies.

The history of the telescope is a testament to human curiosity, ingenuity, and the relentless pursuit of knowledge. From a curved glass in a bowl of water, engineers have given us an eye in the vast frontiers of space. Not only are we unravelling the mysteries of the universe with this amazing and constantly evolving technology, but we are pioneering a future where we will be able to contemplate rarefied possibilities and see as far as we like.

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