Astronomy for GCSE






Astronomy... 3. Through the Ages

In this section:
Page 1:
  • Aristotle
  • Eratosthenes
  • Aristarchus
  • Hipparchus
  • Ptolemy
  • Caliph Al-Mamun
  • Ulugh Beigh
  • Mikolaj Kopernik
  • Giordano Bruno
  • Tycho Brahe
  • Johannes Kepler
  • Galileo Galilei
  • Sir Isaac Newton
Page 2:
  • Robert Hooke
  • John Flamsteed
  • Edmond Halley
  • Christopher Wren
  • John Gadbury
  • William Lilly
  • Jeremiah Horrocks
  • Giovanni Cassini
  • Ole RÝmer
  • William Herschel
  • John Herschel
  • John Goodricke
  • John Couch Adams
  • Urbain Le Verrier
  • Lick Observatory
Page 3:
  • Meudon Observatory
  • Yerkes Observatory
  • Mount Wilson
  • Observatory
  • Edwin Hubble
  • George Ellery Hale
  • Royal Observatory
  • Siding Spring
  • Mauna Kea
  • Cerro Tololo Inter-American Observatory
  • Kitt Peak
  • BTA-6
  • Mstislav Keldysh

This page:

  • Whipple Observatory
  • Wyoming Infrared Observatory
  • United Kingdom Infra-red Telescope
  • Thirty Meter Telescope
  • Karl Jansky
  • Jodrell Bank
  • Five-hundred-meter Aperture Spherical Telescope
  • RATAN-600
  • and more

Obviously large mirrors pose problems. The modern trend is to use mirrors made in segments which can be fitted together to produce the correct optical curve. An example was at the Whipple Observatory on Mount Hopkins in Arizona, USA, in the form of the MMT (Multiple Mirror Telescope) Observatory which had six 183-cm mirrors operating together, making a telescope equivalent to a single 442-cm. However, due to improved mirror technology the smaller mirrors were replaced in 2000 with a single large mirror (the telescope kept its original name).

The MMT in 1981 showing its six primary mirrors.

Another major development has been the "Electronic Revolution"; just as the photographic plate replaced the human eye over a century ago, CCDs (Charge-Couple Devices) have now superseded those. No longer does an astronomer have to stare for hours at photographic plates in the dome; everything is computerised - the observer can be anywhere in the world.

Moving on to the topic of 'invisible astronomy'...

William Herschel (previously mentioned) was the first to prove that the Sun sends out infra-red radiation as well as visible light, and now infra-red astronomy is highly important. It is essential to observe from high altitudes because much of the infra-red radiation is blocked out by the Earth's air, particularly by water-vapour content. Thus we have such infra-red telescopes as the Wyoming Infrared Observatory (the largest functional such telescope from 1977 to around 1980) and, the United Kingdom Infra-red Telescope (UKIRT) which is on the summit of Mauna Kea, Hawaii and now funded by NASA. This one is set to be replaced the Thirty Meter Telescope (TMT) which is designed for near-ultraviolet to mid-infrared observations, although progress has been hampered by those 'Mauna Kea' oppositions mentioned above.

A computer/artistic rendering of the TMT.

Radio astronomy began in 1931 when an American radio engineer, Karl Jansky, using an improvised aerial to study 'static' found he was picking up long-wavelength radiations from the Milky Way.

"Who has not heard of the Jodrell Bank radio telescope in Cheshire, England?" asks Patrick Moore. Or the now destroyed Arecibo radio telescope in Puerto Rico (featured in my Einstein@home section)? The former is now named the Lovell Telescope in honour of its creator, Sir Bernard Lovell (1913-2012). The world's largest 'filled-aperture radio telescope' is the Five-hundred-meter Aperture Spherical Telescope (FAST) (五百米口径球面射电望远镜) in China, nicknamed Tianyan (below).

My photograph, taken in 2016, of Jodrell Bank

The largest 'sparsely-filled radio telescope' is RATAN-600 in Russia. In 2015 it dected a strong signal that closely matched what would be expected for a distant source and a SETI candidate and unusual for a natural source. However, the same artificial appearance also makes a terrestrial source likely, such as from a military satellite, secret/reconnaissance, or from a faulty satellite in a slow spin. Other observatories have failed to corroborate the signal.


In 1957 came the start of the Space Age with the launch of Sputnik 1. Since then there have been thousands of satellites and probes launched. We have the Hubble Space Telescope (HTT) launched in 1990, a 239-cm reflector, which has revolutionised our outlook. We have X-ray telescopes, and others that carry out their work entirely above the screening layers of our air.

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This concludes Chapter 3 in the book. You can subject yourself to the set of questions from the book here:

Click here to proceed to Chapter 4.

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