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Lecture 7

ASTA01H3 Lecture Notes - Lecture 7: Earth'S Rotation, De Revolutionibus Orbium Coelestium, Nicolaus Copernicus

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Kristen Menou

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Lecture 7 ASTA
A Brief History of Ancient Astronomy (Continued)
In 1400 BCE, an exciting event was observed and recorded in China the sudden
righteig ad diig of a guest star.
Although they did not know it at the time, the Chinese had made the earliest known
record of a supernova explosion.
The Chinese also recorded solar and lunar eclipses continuously from the fifth century
In 1054 CE another powerful supernova explosion was recorded by the Chinese
The supernova explosion was powerful enough to be brighter than Venus and visible
during the day for 23 days!
Today, modern telescopes have been used to capture stunning images of the Crab
nebula, which is the remnant of the supernova explosion of 1054 CE
Priests became important members of society thanks to their ability to predict celestial
events, which was viewed as a connection to heavenly deities
The association of celestial objects with one or more gods led to the idea that these
gods could affect individual human lives
This was the birth of astrology the search for influences on human lives based on the
positions of planets and stars in the sky
However, numerous scientific tests have shown that astrological predictions are no
more accurate than we should expect from pure chance
The Geocentric Model of the Universe
The ancient Greeks were interested in building models of nature based on reasoning
and observation
Thales of Miletus, an influential scientist and mathematician, assumed that the world
was understandable and attempted to create models to explain major events in the
It was said that he correctly predicted a solar eclipse in 585 BCE
In 500 BCE, Pythagoras suggested that the Earth was a sphere and not flat, as had been
previously assumed
His model was primarily based on the widely held belief that the sphere is an object of
geometrical perfection
Based o this spherial odel, Eratosthees as ale to alulate the Earth’s
circumference by observing the position of the Sun at noon in two different cities on the
first day of summer. Incredibly, his estimate was accurate to within a few percent of the
currently known value
Ancient Greek philosophers and astronomers accepted without question that heavenly
objects must move on circular paths at constant speeds, and that Earth is motionless at
the centre of the universe
This geocentric (Earth at the centre) model was championed by Aristotle
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