Aristotles World

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Aristotles World

• Joshua Lande

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Aristotle (384 BC 322 BC)

• Born of a well-to-do family in the Macedonian
• In 384 BC.
• At 17 he went to Athens to study at Platos
  Academy.
• He remained for the next 20 years.

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Aristotles Physics

• Is amazingly plausible, coherent, and common
  sense.
• Lacks Mathematical rigor
• Mathematics was concerned with unchanging
  objects that lacked reality, while his natural
  philosophy focused upon changing objects with a
  reality of their own.
• Almost fully accepted until the Copernican
  revolution.

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The Qualities

• Four fundamental quantities
• Hot, cold, dry, wet
• Hot cold are active quantities
• Addition or subtraction will change things
• Wet Dry are result of action of active
  quantities
• Fundamental qualities can be combined in only 4
  ways to create the 4 elements

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Material Science

• Four main elements make up the terrestrial world
• earth, air, water and fire.
• EarthDry Cold
• Water Wet Cold
• Fire Dry Hot
• Air Hot Wet
• Earth is not the same as earth!

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The Periodic Table of the Elements

• 4 elements roughly correspond to 4 states of
  matter
• Solid, Liquid, Gas, Plasma.
• Heavy material like rocks and Iron made up mainly
  of earth
• Lighter objects like wood contain more water and
  air

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This Can Explain Lots of Observations

• Example Boiling
• The addition of heat to a wet object.
• The heat draws the wetness (water/air) out
• The resulting substance is thicker (more earth)
• The separate wetness (water/air) is lighter so
  rises

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Theoretical Issue

• Ice is dryer and colder than water - contain more
  earth.
• But earth is attracted downwards more strongly.
• Strangely ice floats in water?

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Human Biology

• Humans consist of a complex mixture of all the
  elements
• Earth gives strength and weight
• Fire provides warmth
• Water for blood and bodily fluids
• Air fills lungs and breath of life.
• Each human has a different composition making us
  all unique.

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The Universe Has a Cosmic Graph Paper

• In the center of the graph is the geometric
  center of the universe.
• The center of the universe is where all the
  radial lines converge.

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Natural State

• The natural state of objects is at rest
• This is obvious from terrestrial observations
• All things put in motion eventually stop

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Natural Place

• All mater has a natural place it wants to go to
• The natural ordering is Fire, Air, Water, and
  Earth
• Earth wants to go down more than water.
• Lightning is fire in the sky.

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Dynamics

• Natural motion caused by objects seeking their
  natural place
• Motion is straight up / down in radial lines
• Explains why rocks sink in water but air bubbles
  rise up
• Fire rises through air.

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Details

• Natural motion, proportional to weight.
• Explains why rocks fall faster than feathers
• The speed of fall depends inversely on the
  density it falls through.
• Explains water resistance, etc
• Because of this, there can be no vacuum
• Things would move infinitely fast through it

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Why the Earth is Round

• The way for most earthy material to get as close
  as possible to the center.
• The water rest on surface because it wants to be
  further from center.

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The real world is more complicated.

• Our world isnt in equilibrium
• Water somehow gets pulled up into the atmosphere
  for a while (clouds) before eventually falling to
  earth
• Fire trapped in things like trees eventually
  released during burning
• Volcanoes occasionally spew earthy and watery and
  fiery junk into the atmosphere
• It lingers for a while before moving back toward
  its natural place

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Violent Motion

• Only way for an object to move unnatural (in
  non-rectilinear motion up/down) is violently.
• Violent motion happens when one object acts
  directly acts upon another causing it to move.
• So motion only happens when a force is involved.
• This explains pushing a boulder up a hill,
  walking, etc.
• Speed of violent motion proportional to force
• If you push something harder it moves faster

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Impossibility of Heliocentric Universe

• Imagine a bird taking off and flying
• After leaving the ground, it would come to rest
• But rest is moving quickly away from the earth
• So the bird would leave the earth.

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Projectiles

• Hard to explain
• Continues to move in the air instead of
  immediately falling towards earth
• Explanation is that the air in front of the
  object became disturbed by the movement
• Air swirls behind it pushing it along.
• This tendency weakens with time

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Cosmology

• Everything in the sky move round in circles.
• Other than that, it doesnt really change.
• But our terrestrial world is always in flux.
• Therefore, the heavens must be made of an
  entirely different substance.
• This substance is aether, a pure, completely
  different perfect substance

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Aether

• The main difference between aether and matter is
  that aethers natural state is circular motion
• Circles are the most perfect geometric shape
• Aether means always running

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The Moon

• The Moon marks the boundary between the Earth and
  the Heavens
• It is mostly aether.
• Small amounts of earth accounted for the visible
  imperfections on its surface.
• All imperfect celestial objects such as comets,
  nova, and meteors are sublunar.

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Cosmology

• Heavenly objects move in celestial spheres.
• Center is Earth, then moon, then planets, then
  stars.
• Agreement with rough observations.

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Imperfect Planets

• The planets sun drift relative to the stars
• This is an imperfection
• Closer bodies are increasingly corrupt by
  terrestrial elements
• E.g. The sun probably contains some fire in it.

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Dynamical Connection Between Heavens and Earth

• Rotation of the outer sphere of stars
  mechanically responsible for all the other motion
  in the universe.
• The rotation of the stars pulls the planets
  around
• In turn pulls the Sun around
• In turn pulls the Moon around
• In turn communicates motion to sublunar region.
• Plausible
• The tides correlates with the motion of the Moon
  and Sun
• So does the daily warming and cooling of the
  Earth
• And yearly progression through the seasons.

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Questions?