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Lecture

Lecture 1, Intro Introduction to the course -History of astronomy and science -Definition of life -Scientific model


Department
Astronomy & Astrophysics
Course Code
AST251H1
Professor
Harald Pfeiffer

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Darwinian definition of life
-a system capable of evolution of natural selection
History
-Babylonians & Mayans 2500 BCE predicted eclipses and other astronomical phenomena
-Early Greeks 500 BCE: life extends beyond earth
-600 BCE: Thales asks what the universe is made of
-450 BCE Anaxagoras: panspermia (seeds of life) are ubiquitous in universe
(really just a take on abiogenesis)
-Democritus 400 BCE: atomic theory lead to belief in extraterrestrial life
-Aristotle 350 BCE: four elements on Earth and quintessence in heavens
-Western and Christian thought: Earth and Man are “special”
-Bruno 1600: burned for heretical beliefs
-Copernicus 1500-1700: heliocentric “principle of mediocrite”
-Brahe, Kepler and Newton made careful observations and developed rules
-Tesla sends radio to space
-Marconi listens for radio signals for Mars, on a boat in the ocean
-“canals” on Mars are thought to imply a culture
Geocentric Model
-Anaximander (600 BCE), Pythagoras and Aristotle (350 BCE)
-Eratosthenes (240 BCE) estimated radius of spherical earth
-eclipses placed a role in their understanding of relative sizes
Scientific model
-a model is a set of rules to explain observations
-model theory law
-make rules, test them, revise rules
-Occam’s Razor
-repeatability
Kepler’s laws
-elliptical orbit with sun at one focus
-equal areas swept in equal time
-square of Period is proportional to cube of average distance
New Discoveries
-explanation of Venus phases
-explanation of Mars and Neptune retrograde
-four moons of Jupiter
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