Ancient Astronomy (03:36)
Early civilizations believed in a flat Earth within a limited universe; the sky was thought a dome over it, marking its borders. The Greek mythology of Odysseus included a venture to the Land of the Dead at the world's edge.
Global World (02:55)
Ancient astronomers determined Earth's curvature by observing lunar and horizon events; early sailors made lengthy voyages and did not find its end. Phoenicians influenced Greek scientific perspectives with a story of circumventing Africa and crossing the equator.
Finding Size (03:27)
Eratosthenes first calculated the circumference of the Earth; he headed the Alexandrian Library, aspiring to collect the world's catalog of knowledge. He used shadow observations and geometry to measure the globe at roughly 29,000 miles round.
Fixed Planet Theory (06:04)
Claudius Ptolemy first mapped the round world on a flat surface; he used geometry to map the cosmos, but his representation of the universe revolved around the Earth. A crystalline celestial dome was believed to keep stars in place.
Enduring Ideas (04:11)
Ptolemy added epicycles to his model to account for retrograde motions, and used an equant to enable envisioning planetary movements. His theory was functional, used 1,500 years, and turned into Armillary Spheres to teach astronomy and time organization.
Cosmic Control (02:57)
Ptolemy believed that movements of celestial bodies impacted life on Earth; he wrote a book on astrology, and studied astronomy to scientifically improve predictions. The fall of Rome triggered the Dark Ages; much of his work was lost to Europe.
Importing Data (05:10)
During the Dark Ages, the Islamic world grew, adopting religion, art, and classical knowledge from other civilizations; they established observatories and created astrolabes using Ptolemy's model. They added information to his accumulated knowledge, but some wanted to simplify his theory.
Regaining Astronomy (05:09)
Islamic knowledge spread west to religiously transformed Europe; Ptolemy's model had endured, fitting Christian beliefs that God created the universe and encompasses it. Return of his written work solidified their ideas of a mathematically perfect cosmos.
Ignored Science (04:57)
During the 14th century, Western Europe experienced the Renaissance; Nicholas Copernicus learned Islamic astronomy and set up his own observatory. He replaced Ptolemy's model with a Heliocentric one; his discovery went unnoticed until the telescope's invention.
Extensive Discoveries (05:17)
In 1608, Hans Lippershey invented the Dutch Spyglass; Galileo Galilei immediately improved it. He crafted his own convex and concave lenses to ensure image quality, creating a devise capable of 20 times magnification, and changing astronomy permanently; the Ptolemaic model was proved incorrect.
Clashing with Religion (05:32)
The Roman Catholic Church had aligned itself to the Ptolemaic model when Galilei's discoveries spread through Europe. They were threatened by his heliocentric theories; they forbade him from teaching them and banned Copernicus's writings.
Revolutionary Era (02:47)
For ten years, Galilei did not share his heliocentric discoveries, but when his friend was appointed Pope, he published dialogue featuring both Ptolemaic and Copernican models. He was found guilty of Heresy and arrested; he enlisted other scientists to prove the physics behind his theory.
Credits: Finding the Center (00:29)
Credits: Finding the Center
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