1543
Mikolaj Kopernik (Nicholas Copernicus)
Polish priest, Mikolaj Kopernik (known in the West as Nicholas Copernicus),
publishes a book suggesting that the Sun is the centre of the Universe with the Earth orbiting around it and rotating daily on its axis. The idea
does not explain all the astronomical observations as he, also, insists on circular motion.
His opponents counter with several arguments. The Earth could not carry the Moon around with it if it was moving. Winds would blow us off if the
Earth was rotating. The stars should show a parallax (i.e they would change relative position as our vantage point changed).
Helocentric (Sun-Centred) System
Copernicus has few answers but suggests that the stars fail to show a parallax because they are very distant. The book is later banned by the
(Christian) Catholic Church until the late 20th Century.
The new Sun-centred system is less cumbersome than Ptolemy's and can be used for predicting the positions and
movements of the planets.
1572
Tycho Brahe
The Danish astronomer, Tycho Brahe, studies a brilliant new star that appears in the sky. The star is later
known to be a type of exploding star. Brahe names the star a nova.
Brahe finds no parallax indicating that it is a real stellar object and not something close to the Earth. The star fades after a couple of years.
This is an indication that the starry heavens do change.
He also studies a comet and shows that it is moving in an elongated orbit amongst the planets. This indicates that comets are not atmospheric
phenomena and that there are no crystal spheres holding the planets since objects can move freely between the planets. It also shows that not all
heavenly motion is circular.
This is the first observational evidence that Aristotle and Ptolemy's ideas
may be flawed. Brahe disagrees with Copernicus, however, and writes that the planets do indeed go around the Sun
but that the Sun (carrying all the planets) orbits the Earth. This half-way idea is not taken seriously. He measures the year to an accuracy of one
second. This helps promote the introduction of the
Gregorian
Calendar (now the international standard) in 1582.
Tycho Brahe is the last of the European naked-eye astronomers. His detailed and accurate observations of the motion of Mars would lead to a better
understanding of planetary orbits after his death.
Omicron Ceti or Mira (Wonderful)
1596
David Fabricius discovers that the star, Omicron Ceti, varies its brightness over several months. This is
another blow to the idea of the unchanging heavens.
1600
Giordano Bruno
In Italy, Giordano Bruno believes and teaches that the Universe is infinite, the Earth is moving around the Sun,
the stars are other suns with planets around them, and life is not confined to the Earth.
He is eventually burnt at the stake for heresy!
[Astronomy History: Indian and Arabic]
[Astronomy History: Galileo to Newton]
KryssTal Related Pages
An easy-to-understand scaling of the Universe in space. Distances in space are represented by the time light takes to travel there.
An easy-to-understand scaling of the Universe in time. The chronology of the Universe is compared to a real year.
A listing of the 20 brightest stars as well as explanations of the terms used.
Information about the planets and satellites of the Solar System with explanations of the terms used.
A historical account of the discovery of the electromagnetic spectrum and its uses in Astronomy. Radio waves, infra-red, visible light, ultra violet, X-rays and gamma rays are explained.
An account of how various properties of stars can be measured by studying starlight. Includes brightness, distance, luminosity, temperature, mass, radius, density and an introduction to the H-R Diagram.
An account of how stars evolve and change the chemistry of the Universe.
The force that moves apples and planets. A short introduction to the ideas of Kepler and Newton that culminated with the theory of Universal Gravitation.
This looks at the history of inventions and the various civilisations of the world.
Selected biographies of people from around the world including scientists and astronomers.
External Links
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History of Science
A large collection of resources looking at the history of astronomy, physics, chemistry and mathematics.
