Armagh Observatory, College Hill, Armagh BT61 9DG, +44 (0)28 3752 2928

Section I - Items illustrating the background to the problem.

Click on image to enlarge.

1. Portrait of Nicholas Copernicus (1473-1543) who many regard as
the founder of modern astronomy. Born in Poland he studied in
Cracow and Bologna. Though made without the aid of a telescope,
his careful observations together with those of others and his
physical intuition, lead to a revolution in our understanding of
the mechanics of the solar system. The new heliocentric theory
which he propounded maintained that the Earth moved around the
Sun once per year and rotated on its own axis once per day.
(Univ. of Nicholas Copernicus, Torun)

2. Tycho Brahe (1546-1601), the greatest of the pre-telescopic
astronomers, whose precision observations made it possible to test
the new heliocentric hypothesis and allowed his successor,
Johannes Kepler to derive his famous laws of planetary motion.

3. Tycho's Observatory built in 1584 at
Uraniborg in Denmark.

4. Johannes Kepler (1571-1630) who formulated a set of laws which
could be expressed in simple equations to describe the motions of
the planets about the Sun. His famous third law, stated that the
the square of the period of a planet is proportional to the cube
of its distance from the Sun. As the periods of all the planets
were known, it was only necessary for the distance of one of them
to be measured to derive the distance from the Sun of all. (High Altitude
Observatory)

5. The Rudolphine Tables compiled by Kepler and Tycho which were
published in 1627. These tables gave the positions of the planets
with an accuracy many times better than any previous rivals and
were instrumental in establishing the superiority of the new
heliocentric picture of the solar system. They were named after
the Emperor Rudolf II who commissioned the calculations on which
they were based in 1601.

6. An Orrery by Gilkerson These models of the solar system were
designed to illustrate the relative simplicity of the Copernican
system and to convince people of its authenticity. They received
their name from Charles Boyle, 4th Earl of Cork and Orrery, for whom the
first such device was made in 1705 by John Rowley.

7. Galileo (1564-1642) whose defence of the Copernican
heliocentric solar system lead to a bitter conflict with the
establishment and the Catholic Church. Galileo's observations of
spots on the Sun and craters on the Moon, made with the recently
invented telescope, showed them not to be the flawless heavenly
bodies people had previously believed. (Courtesy of the High Altitude Observatory)

8. Frontispiece to Opere di Galileo Galilei (1656) The works of
Galileo which gave robust support for the Copernican system.

9. Sir Isaac Newton (1642-1727) was one the greatest scientists
of all time. His theory of universal gravitation provided the
physical and mathematical basis for our understanding of planetary
motions. He was able to show that the force of gravity that draws
a falling apple to the ground is the same force that holds the
Moon in its orbit about the Earth and the
planets in their orbits around the Sun. This painting by Sir Godfrey
Kneller shows Newton in
1702 shortly before he became President of the Royal Society.
(Courtesy of the National Portrait Gallery)

10. Principia Mathematica (1687) Newton's masterpiece; the most
important treatise in the history of science. In this book, Newton
showed how mathematics could be used to describe the behaviour of
the universe; an idea which is fundamental to modern science.
Here, he postulated his laws of motion and of universal
gravitation which provided the basis of our understanding of the
mechanics of the solar system for the next two centuries. It was
not until Einstein's theory of General Relativity was developed
that it became apparent that Newton's theory represented a
simplification of the true situation.