In the 1590s, Johannes Kepler said to himself that God’s design for the universe must be aesthetically pleasing, regular, and logical. Kepler trusted God to have wanted His universe to have these properties.
Following this line of thinking, Kepler reasoned that since the sun is by far the largest body in the solar system, God would have centered the solar system on it.
Half a century earlier, Nicolaus Copernicus said the sun was at the center of the solar system, but he made no claims about how the sun’s enormous size would affect the surrounding planets.
Unlike Copernicus, Kepler believed he could figure out how God used the sun to govern the movements of the planets.
Later, Kepler would write to a friend:
For a long time I wanted to become a theologian; for a long time I was restless. However, see now how through my effort God is being celebrated through astronomy.
Kepler became obsessed with understanding God’s design. He asked:
- Why did God make six planets? Unlike most astronomers of his time, Kepler did not count the sun or the moon as planets, although he included the earth as one.
- Why did God separate the planets in the way He did?
- Why are there regularities in the way the planets move? For example the conjunctions of Saturn and Jupiter every 20 years.
Saturn and Jupiter’s conjunctions plotted by Kepler in Mysterium Cosmographicum, first published in 1596.
Kepler sought an explanation of God’s creation in mathematics. He was not the first to do so: even in Kepler’s time, it was over a thousand years since the Pythagoreans first claimed that numbers were the basis of the universe.
Kepler’s solution was inspired by the Ancients in the form of the Platonic solids – the five perfectly regular polyhedra whose symmetry permits their use as dice.
The Platonic Solids – Kepler believed these shapes determined how far each of the six known planets lay from the sun.
Kepler began by assuming that each planet’s orbit was located on a sphere. He found that the 6 spheres could be nested so that the spaces between them perfectly accommodated the five perfect polyhedrals. Kepler believed he had uncovered the hand of God in the design of the solar system. (Of course, his scheme would have never seen the light of day if Kepler had known about Uranus and Neptune.)
In Kepler’s model the solar system’s planets orbited the sun in circular paths whose sizes were determined by an arrangement of the five Platonic Solids.
In the end, Kepler’s proposal did not work, but he had taken a huge step that Copernicus had not: Kepler said that the motion of the planets must be determined by the physical effects of the sun.
Although Kepler was unsuccessful in answering his first two questions, his mathematical pursuit of the third question – his search for the underlying reasons for the planets’ movements and the laws he discovered – were the foundation of Isaac Newton’s discoveries about gravity and indeed all of modern physical science.
Science is full of failed ideas. The few big ideas that work out are what we tend to remember.
Few scientific ideas have been as big as Kepler’s and perhaps even fewer have come from a certitude about God’s design of the universe.
Author of this page: The Doc
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Further Reading
Owen Gingerich
The Eye of Heaven: Ptolemy, Copenicus, Kepler
The American Institute of Physics, 1993
“When Kepler found his long-cherished belief did not agree with the most precise observation, he accepted the uncomfortable fact. He preferred the hard truth to his dearest illusions, that is the heart of science.” – Carl Sagan