Everyday Stuff: Telescopes
There are few more awe-inspiring activities than simply lying back on a clear night and gazing through unfathomable distances at the stars. Yet in our 24-hour world of bright lights and big cities, how often do we stop to take a look?
Throughout history the night sky has fascinated and inspired entire cultures the world over. The advent of the telescope, which can be traced back over seven hundred years, profoundly affected not only the way we look at the stars, but the way we look at ourselves.
The first breakthrough in optical technology came with the simple lens. No one is very sure when lenses were first invented; the earliest reports seem to date them at around 424BC.
However, it wasn’t until the late 11th century that they started to be used to help vision with the invention of spectacles in Italy. It took yet another 300 years or so for people to realise lenses’ far-reaching implications. The man credited with producing the first device capable of magnifying distant objects is Hans Lipperhey, a Dutch spectacle maker. He allowed children to play with the lenses in his shop, and noticed they were able to see a distant church up close.
Lipperhey applied for a patent in 1608, but to no avail, the authorities deciding that the idea could not be kept a secret. However, Lipperhey made several binocular telescopes for the States General of the Netherlands, and was paid handsomely for his services.
Telescopes rapidly became very popular and the idea had soon raced across mainland Europe to Venice, where it was described to a local instrument maker by the name of Galileo, who made a perfect replica.
It was Galileo who was the first to point a telescope at the night sky and record his findings.
Whilst the majority of the European intelligentsia were rather disdainfully regarding telescopes as nothing more than a way of producing optical illusions, Galileo was busy writing The Starry Messenger.
Containing drawings of the moon’s surface showing mountains and craters, the sun complete with sunspots and the moons of Jupiter, this was the book that proved Copernicus’ theory that the Earth travelled around the Sun.
The book not only landed Galileo in a spot of bother with the Inquisition, but altered our very perception of humans’ place within the universe.
Roughly sixty years later Isaac Newton took an interest in telescopes, noting that the lens was a round prism and as such was limited as to how strongly it could magnify an image. This led Newton to favour a new design that used mirrors instead of lenses to concentrate the light. These new reflective telescopes, which used mirrors to gather and focus light from distant objects, vied for popularity with refractive telescopes, those that use lenses, for the next 200 years as the designs were refined and improved.
In 1824 German physicist Joseph Fraunhofer unveiled the Great Dorpat Refractor, the most powerful refracting telescope of its time, which contained a timing device allowing the telescope to automatically track stars across the night sky.
Fraunhofer’s design became the standard for refractors and provided the template for George Hale’s mammoth telescope built at the Yerkes Observatory, which contained a 1-metre lens - still the largest in the world.
But that really was the end of the road for refracting telescopes, Newton’s predictions were realised - refractors just couldn’t get any better. Consequently attention turned back to reflective telescopes.
As advances in mirror-making technology increased, telescope sizes grew and grew as each observatory out-competed the next; the Mount Wilson observatory’s 1.5 metre mirror was superseded by the Texas 2.3m, only to win it’s crown back with a 2.5m mirror.
This was all before they were blown out of the water by an observatory on Mount Palomar, California completing a telescope in 1948 which housed a 5m mirror. The world-record is currently held by the twin Keck telescopes standing at the summit of Hawaii’s Mauna Kea, a dormant volcano.
Each telescope houses a 10m mirror made up of 36 hexagonal segments which operate in unison with nanometre precision. The next plan is to produce ELTs (extra large telescopes) with huge hundred metre diameter mirrors, which would have specialist equipment that would reduce and adjust for atmospheric disturbances.
These ground-based telescopes work extremely well, especially when situated above the cloud line like those in Hawaii. However, the best views can only be obtained away from disruptive influence of the Earth’s atmosphere - in space.
Work began on what was to become the Hubble Space Telescope in the 1970s; twenty years and $1.5bn later it was launched into orbit some 375 miles above the Earth’s surface. After a few teething troubles the Hubble telescope beamed back incredible images from all over our Universe.
The farthest object recorded so far is an, as yet unidentified, object peeking out from behind a cluster of galaxies called Abell 2218, over thirteen billion light years away. We are seeing it when the universe was only 750 million years old. At the maximum speed of the space shuttle, it would take almost 500 million million years to get there… better leave soon!
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