Man has always looked to the skies for answers … as if a celestial blueprint that tells the story of humanity’s journey in time and space. Creation myths connect god with the heavens, often the constellations, sometimes with a link to ancient aliens who came to Earth to seed humanity and will one day return. As the millennia progressed, so too did the use of telescopes to find answers to many of these age-old questions. That quest continues today with new and more advanced technologies as we venture into space.
A telescope is an instrument that aids in the observation of remote objects by collecting electromagnetic radiation (such as visible light). The first known practical telescopes were invented in the Netherlands at the beginning of the 17th century, using glass lenses. They found use in terrestrial applications and astronomy.
Within a few decades, the reflecting telescope was invented, which used mirrors. In the 20th century many new types of telescopes were invented, including radio telescopes in the 1930s and infrared telescopes in the 1960s. The word telescope now refers to a wide range of instruments detecting different regions of the electromagnetic spectrum, and in some cases other types of detectors.
The word “telescope” was coined in 1611 by the Greek mathematician Giovanni Demisiani for one of Galileo Galilei’s instruments presented at a banquet at the Accademia dei Lincei. In the Starry Messenger Galileo had used the term “perspicillum”.
History of Telescopes
The earliest recorded working telescopes were the refracting telescopes that appeared in the Netherlands in 1608. Their development is credited to three individuals: Hans Lippershey and Zacharias Janssen, who were spectacle makers in Middelburg, and Jacob Metius of Alkmaar. Galileo heard about the Dutch telescope in June 1609, built his own within a month, and greatly improved upon the design in the following year.
The idea that the objective, or light-gathering element, could be a mirror
instead of a lens was being investigated soon after the invention of the
refracting telescope. The potential advantages of using parabolic mirrors –
reduction of spherical aberration and no chromatic aberration – led to many
proposed designs and several attempts to build reflecting telescopes. In 1668,
Isaac Newton built the first practical reflecting telescope, of a design which
now bears his name, the Newtonian reflector.
The invention of the achromatic lens in 1733 partially corrected color
aberrations present in the simple lens and enabled the construction of shorter,
more functional refracting telescopes. Reflecting telescopes, though not
limited by the color problems seen in refractors, were hampered by the use of
fast tarnishing speculum metal mirrors employed during the 18th and early 19th
century a problem alleviated by the introduction of silver coated glass mirrors
in 1857, and aluminized mirrors in 1932. The maximum physical size limit for
refracting telescopes is about 1 meter (40 inches), dictating that the vast
majority of large optical researching telescopes built since the turn of the
20th century have been reflectors. The largest reflecting telescopes currently
have objectives larger than 10 m (33 feet).
The 20th century also saw the development of telescopes that worked in a wide range of wavelengths from radio to gamma-rays. The first purpose built radio telescope went into operation in 1937. Since then, a tremendous variety of complex astronomical instruments have been developed.
