Galilean telescope shakes off dust

EDMONTON (CUP) – The telescope of Galileo was an elegant device of the Enlightenment, turning astrological conjecture into the science of astronomy.

Its day in the sun was the topic of a lecture by Professor Albert Van Helden of Houston’s Rice University last week at the University of Alberta, in which he fondly summed up Galileo’s device as having a brief-but-glorious career.

“What intrigued me was how quickly the Galilean telescope had reached its potential, and how quickly – in terms of discovery, in terms of power – it had become obsolete,” Van Helden began.

The telescope had a simple construction of convex and concave glass lenses. Indeed, that simplicity of Galileo’s telescope design evidently incited claims that his was not the first.

“Would it be an act of genius for a spectacle maker, to put together a concave and convex lens and invent a telescope?” Van Helden inquired. “That is the sort of thing you’d expect a spectacle-maker to know . . . But if you make a counter-intuitive move, and restrict the aperture [of view], then, all of a sudden, we get a clear image.”

This was the genius of Galileo’s telescope. Prior telescopes offered a large-but-fuzzy image. When Galileo restricted the aperture, this delivered an image that was enlarged and clean for the first time.

Not only was the design groundbreaking, but Van Helden added that Galileo polished and ground lenses to get the clarity needed for the telescope’s range.

Interspersing 16th- and 17th-century sepia illustrations and photos of artifacts, Van Helden gave a personal, as well as professional, resumé of Galileo, mentioning previous instruments and patents, family life and professional appointments, and recalling handwritten manuals with familiarity.

Van Helden also explained the practical limitations on Galileo’s design, in that one can only take in a small part of the telescope’s field of view.

“In the Galilean telescope, the exit pupil . . . is larger than the pupil of your eye,” he said. “That means, if you move your eye laterally, the field moves with you . . . That is one of the great limitations of the Galilean telescope.”

Galileo made this first spyglass in June 1609, and began methodical observation for a scientific publication of his findings.

“What [Galileo] observed first was, of course, the moon,” Van Helden said, noting that the astronomer charted the varied topography of its surface.

This seemingly innocuous discovery had earth-shattering implications for the age’s philosophers and scientists. Under the Aristotelian astronomy of the day, Earth was understood as geocentric, and the surfaces of the planets surrounding as flawlessly smooth.

Van Helden also showcased Galileo’s mathematical approach and his enthusiasm for accuracy. Despite stubbornness and speculative inconsistency from colleagues, Galileo’s findings with this telescope forever changed the cosmological beliefs of our galaxy into a scientific and open-eyed sphere of understanding, Van Helden concluded.

“There were people who wished him ill, lots of people. You loved the guy, you [hated] the guy. Galileo was a person about whom you would not tend to be neutral.”

By Arah Slack

The Gateway (University of Alberta)

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