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How does the world work? You can debate and discuss about biology and chemistry, but ultimately its physics that explains everything.
How do we know this? Well, it all began with the night sky... |
“What are ye orbs? The words of God? The Scriptures of the skies?” - Philip James Bailey, "Festus" (1813)
Imagine if you were back in the nights when there was literally nothing to do. Your forefathers had discovered fire and with that freed your mind from the last worries for survival. Where would your mind dwell on then?
Our ancestors had the same predicament, and took to amazement what we had taken for granted: the night sky. The first attempts to decode the mysterious lights up there took the form of religious myths and legends. It took some time for them to notice that there was a pattern to these lights; some seem to coincide with the planting season and others during harvest time.
Early 'astronomers' (if you can call them that) tied these signs with local gods, and thought to be responsible for seasonal events such as floods and droughts, powerful signs of the gods’ temperaments. They took it seriously enough to align monuments according to celestial paths, celebrate festivals and present sacrifices.
Our ancestors had the same predicament, and took to amazement what we had taken for granted: the night sky. The first attempts to decode the mysterious lights up there took the form of religious myths and legends. It took some time for them to notice that there was a pattern to these lights; some seem to coincide with the planting season and others during harvest time.
Early 'astronomers' (if you can call them that) tied these signs with local gods, and thought to be responsible for seasonal events such as floods and droughts, powerful signs of the gods’ temperaments. They took it seriously enough to align monuments according to celestial paths, celebrate festivals and present sacrifices.
As our ancestors came to their senses, they find that the paths of these heavenly bodies are quite predictable, which precludes them from being divine, although others seem to wander off from their anticipated positions. The Greeks called these “planetes”, meaning “wanderers”, and their unpredictable nature sparked what probably is the first significant scientific debate – the astronomical model of the universe.
Contrary to popular belief the Greeks have several conflicting theories on the structure of the solar system, depending on who you ask. Early in the debate the philosophers split into two sides; the Anaximanderists believe in a geocentric system whereby the lights from celestial objects are actually holes from invisible wheels that moves along a cylindrical Earth. Pythagoreans led by Philolaus who is a student of Pythagoras himself, on the other hand, by observing eclipses, believe that the earth is spherical and orbits around a “central fire” along with other objects including the sun and moon, explaining night and day as well as seasonal variances.
Contrary to popular belief the Greeks have several conflicting theories on the structure of the solar system, depending on who you ask. Early in the debate the philosophers split into two sides; the Anaximanderists believe in a geocentric system whereby the lights from celestial objects are actually holes from invisible wheels that moves along a cylindrical Earth. Pythagoreans led by Philolaus who is a student of Pythagoras himself, on the other hand, by observing eclipses, believe that the earth is spherical and orbits around a “central fire” along with other objects including the sun and moon, explaining night and day as well as seasonal variances.
Close Philolaus, but no cigar...
Later these two hypotheses were synthesized by Plato and Aristotle into a geocentric system with a spherical earth. This only partially answers the movements of the “wanderers”, which sometimes appear to reverse their orbits. After puzzling astronomers for a couple of centuries, finally an enduring model was formed by none other than the great Ptolemy, in which orbiting wanderers (centred on the Earth rather than a ‘central fire’) may have a lesser orbit along their paths.
The Return of Heliocentrism
For almost a thousand years since the fall of the Roman Empire, Ptolemy’s model became official doctrine; it was perfect, it explains everything elegantly and fits the social model of the time. Everyone is happy with it, the religious authorities as it is in accordance to scripture (humanity is special), the crown as it provides justification for their reign (the state revolves around the king), and the intellectuals as there are no other viable alternatives.
The Platonic model is (then) a valid scientific hypothesis, explained by observation. However science is not static, unlike dogma, it changes with every discovery of new observations.
The first to seriously challenge this official standard was Aristarchus of Samos, who was the first to propose a heliocentric model, as opposed to those centred on a ‘central fire’ or the Earth. Although his work is considered fringe science then and was left forgotten, the idea later resurfaced, independently, in the 16th century through Nicolaus Copernicus in his magnum opus: De Revolutionibus Orbium Coelestium.
The problem with Copernicus’ system is that it is no more accurate as Ptolemy’s. Copernicus still relies on a the idea of circular ‘perfection’ as espoused by the Greeks. This does not resolve the problem of discrepancies between the planets’ predicted positions and what is actually observed.
Revolution: Hypotheses and Theories, Observations and Evidences
This problem results in the birth of a new approach to science: evidential support. Anyone can propose a hypothesis; you can for example, suggest that people evolved from slugs, but as they say “extraordinary claims require extraordinary evidence.”
The Return of Heliocentrism
For almost a thousand years since the fall of the Roman Empire, Ptolemy’s model became official doctrine; it was perfect, it explains everything elegantly and fits the social model of the time. Everyone is happy with it, the religious authorities as it is in accordance to scripture (humanity is special), the crown as it provides justification for their reign (the state revolves around the king), and the intellectuals as there are no other viable alternatives.
The Platonic model is (then) a valid scientific hypothesis, explained by observation. However science is not static, unlike dogma, it changes with every discovery of new observations.
The first to seriously challenge this official standard was Aristarchus of Samos, who was the first to propose a heliocentric model, as opposed to those centred on a ‘central fire’ or the Earth. Although his work is considered fringe science then and was left forgotten, the idea later resurfaced, independently, in the 16th century through Nicolaus Copernicus in his magnum opus: De Revolutionibus Orbium Coelestium.
The problem with Copernicus’ system is that it is no more accurate as Ptolemy’s. Copernicus still relies on a the idea of circular ‘perfection’ as espoused by the Greeks. This does not resolve the problem of discrepancies between the planets’ predicted positions and what is actually observed.
Revolution: Hypotheses and Theories, Observations and Evidences
This problem results in the birth of a new approach to science: evidential support. Anyone can propose a hypothesis; you can for example, suggest that people evolved from slugs, but as they say “extraordinary claims require extraordinary evidence.”
So far all the astronomers from Ptolemy to Copernicus had only been proposing hypotheses, although hard data exists, they were either incomplete or inaccessible. Granted that the latter is completely justified as calculating astronomical data is labour-intensive (and therefore expensive) in terms of number-crunching, and this was before trigonometry and calculus were invented.
In a way, we should thank two people for transcending their personal interests and fears, Tycho Brahe and Johannes Kepler. Brahe used his position and resources from being the court mathematician for Enperor Rudolf II of the Holy Roman Empire (a position that includes those of court astrologer and weatherman), to record what was probably the most comprehensive catalogue of astronomical recordings of the time; everything from stellar and planetary positions to the sightings of supernovas and comets.
In contrast to the passive Brahe, Kepler became the active interpreter of the former’s observations. With Brahe’s data, Kepler came to conclude that planetary motions follow a set of mathematical rules, which turns out into the first laws in physics.
For the first time in history prediction became a science rather than something mystical or miraculous.
In a way, we should thank two people for transcending their personal interests and fears, Tycho Brahe and Johannes Kepler. Brahe used his position and resources from being the court mathematician for Enperor Rudolf II of the Holy Roman Empire (a position that includes those of court astrologer and weatherman), to record what was probably the most comprehensive catalogue of astronomical recordings of the time; everything from stellar and planetary positions to the sightings of supernovas and comets.
In contrast to the passive Brahe, Kepler became the active interpreter of the former’s observations. With Brahe’s data, Kepler came to conclude that planetary motions follow a set of mathematical rules, which turns out into the first laws in physics.
For the first time in history prediction became a science rather than something mystical or miraculous.
Ponder this
Why did multiple models arise amongst the Greek philosophers, and later only Ptolemy's version survived into the Middle Ages? Is having a consensus or standardised 'truth' a good thing? Who determines what is the 'truth'?
Why did Brahe never go beyond formulating a prediction based on his observations? He is clearly smart enough to think independently, rather than simply accepting Ptolemy's model.
Discuss
A lot of the discoveries in physics are circumstantial, Kepler working with Brahe, a long lineage of Greek philosophers. In an alternate history, would the truth have been discovered nonetheless? Could these principles of physics be independently discovered in East Asia or India, Africa or the Americas?
Further readings
Java simulation of the Ptolemaic System, at Paul Stoddard's Animated Virtual Planetarium, Northern Illinois University
Philolaus, at the Stanford Encyclopedia of Philosophy
The Church and Copernicus, a look at Nicolaus Copernicus' struggles against religious dogma.
Johannes Kepler and Tycho Brahe, at Journey Through the Galaxy
