Cosmology and the Origin of Life

Formulation of a Cosmological Model:

The Rules:

Making Models:

Early Cultures were curious and motivated to explore the world no one was ignorant because everything was new but the process of learning can begat ignorance through the death of imagination

The First Cosmology:

The Second Cosmology: Evolving Towards the Hierarchical Viewpoint

Some Example Myths as Cosmological Models

ORIGINAL IDEA:

Everything was created in a Single Event Everything was created in a Single Event Everything was created in a Single Event

The Third Cosmology:

Geometric Universe:

• Sky Observations Motion
• Mythological Figures Constellations
• Planetary Motions
• Calendars
• Lunar Eclipses

All of this started about 4000 years ago

Greeks refined the geometric universe (and stole a lot of th e math from the Babylonians).

They defined Four Primal Beings as being dominant in their cosmological model:

• Chaos (the limitless Void)
• Gaea (the Earth)
• Tartarus (the lower world)
• Eros (spirit of love)

Now we have various combinations of gods and sub-gods getting together to help populate the earth:

• Gaea + Uranus (sky god) Titan s
• Titans = first RULERS of the Earth
  Prometheius molds humans from clay and then breathes into them the spirit of life

  Pandora Releases Evil Secrets that Prometheius had locked away

  World is Doomed ( again )
  Moving Towards a Geocentric Cosmology
  
  

  A Scientific Perspective:

  Three biases from this perspective:

  Scientific models are only validated through observation and prediction

  Science itself is a process which maps out the unknown. It is not a process that converts the unknown to the known nor is it a method to discover the "truth".

  There is nothing perfect about SCIENCE. Its beauty and truth lie in its intrinsic uncertainty.

  So lets' start around 600 BC. By this time Greek Culture was quite well defined and the idea of Law, as a means of establishing order was firmly in place. If society itself could be "governed" by a set of rational laws, then clearly Nature must be similarly governed.

  Hellenistic Culture(~600 B.C.):

  The ancient Greeks inherited astronomical records from the Babylonians and applied the data to construct a cosmological framework. Data was not just used for practical goals, such as navigation, but also to think of new experiments = natural philosopher.

  Fine Tuning the Cosmos: Identifying its essential Ingredients

  600 BC Greeks start to dissect the world into component pieces:

  ORIGINAL IDEA ALERT:
  • All the world can be understood as an interaction between 4 primal elements (variation on the earlier theme)

  • Air, Earth, Fire, Water

    • Thales Water: world floats in primordial sea
    • Anaximenes Air is ultimate: stars are fires in the sky

  Now we have CAUSE and EFFECT and the first hints of the physical nature of the Universe.

  There are three components to cause and effect:

  • contiguity in space
  • temporal priority of the cause (i.e. its first)
  • necessary connection

  

  An Alternative to the idea that something is most important:

  500 BC:

  Democritus: The Universe consists of atoms and the Void; all else is opinion and illusion

  Collisions between atoms formed the Universe

  The Universe runs by Itself

  ORIGINAL IDEA ALERT

  Quantum Mechanics has just been expressed. That is, the universe can exist without anyone in it

  The Greeks constructed their whole theory of the Universe on the concepts of numbers and shape, arithmetic and geometry. An example of this was when Empedocles discovered that there exist only 5 regular solids. This ultimately leads to Plato's Theory of Forms .

  Plato, so impressed by the elgence of this discovery, then proposed that four of these solids correspond to the four atomic elements in the Universe (earth, water, air and fire). The fifth element corresponds to the Cosmos:

  

  Now comes geometry and the concepts of perfection. Culturally this seems like a natural harmonious meld with the Cosmos:

  Pythagoras Geometry! a² + b² = c²

  • Earth is a sphere (which is a perfect figure)
  • Planetary Motion is governed by geometric laws
  • Geometry begets Harmony

  To Plato, making a model for Astronomy seemed relatively simple. All one had to do was to provide an explanation which would account for the highly ordered motions of the planets as observed from the Earth.

  Over time this lead to Aristotle's Cosmology of the Crystalline Spheres:

  Aristotle and Plato:
  

  In the center of the painting are Aristotle and Plato, Aristotle's hand level to the Earth symbolizing his realism view of Nature; Plato's hand pointed towards the heaven symbolizing the mystical nature to his view of the Universe.

  Aristotle stands in the Greek philosophical tradition which asserts that nature is understandable. This tradition, opposed to the idea that nature is under the control of capricious deities which are to be appeased rather than understood, is one of the roots of science.

  However, one must be careful to assert that nature is not completely understandable

  Aristotle constructed his view of the Universe based on a intuitive feeling of holistic harmony. Central to this philosophy was the concept of teleology or final causation. He supposed that individual objects (e.g. a falling rock) and systems (e.g. the motion of the planets) subordinate their behavior to an overall plan or destiny.

  His theory of motion flows from his understanding of matter as constituted of four elements: air, earth, fire, and water. Objects, being solid like earth, would tend to clump together with other solids (earth), so objects tend to fall to earth, their natural place. Thus, falling is a natural motion.

  To avoid the idea that their is an infinite chain of causes, Aristotle argued that there must be an "unmoved mover," something which can initiate motion without itself being set in motion today we might call this gravity!

  Aristotle introduces the Two Sphere Universe. This is a FINITE Universe that you can now draw the Universe on a piece of paper!

  We have come a long way from the world view that everything had a common origin (e.g. the Cosmic Womb in the Mythic Universe):

  The Earth lies at the Center of the Two Sphere Universe and everything revolves around it Huge Cultural Bias.

  Furthermore, Aristotle tells us that the Universe is perfect and unchanging.

  Clearly, imagination has now vanished. We have a deterministic model of the Universe (e.g. two spheres) and we think that all is figured out!

  Now all is in harmony, the earth is at the center of the universe and the cosmos revolves around us in perfect contentment

  Elements of the Universe at this time (Aristotle):

  • Geocentric Cosmology and the Earth is Immobile.
  • Stars and planets on perfect crystalline spheres that rotate around the Earth.
  • Universe is perfect and Changeless

  But there are observational problems:

  • observed transient phenomena (comets, novae, variable stars) attributed to disturbances in the upper atmosphere of the earth

  • Periodic changes in the brightness of the planets this had to be attributed to something intrinsic to the planet because the earth - planet distance did not vary under the the crystalline sphere model.

  • Aristotelian model makes a definite prediction all planets and stars should move in the same direction . But Mars was known at that time to sometimes move in the opposite direction for a brief period of time (this is known as retrograde motion)

  • So Ptolemy builds an incredible complicated machine to preserve the geocentric model and account for retrograde motion ( like this )

  • The correct explanation for retrograde motion
    
    • Java Applet for Retrograde Motion
    • Applet Showing the Relative orbits or Earth and Mars

  There was, however, a competing model:

  Aristarchus (270 B.C.) developed the heliocentric theory

  

  Problems for heliocentric theory:

  • Earth in motion??? can't feel it
  • no parallax seen in stars

    

  • geocentric = ego-centric = more "natural"

  Measuring the Circumference of the Earth:

  Eratosthenes (220 B.C.) - The early Greeks knew the Earth was a sphere based on the shadow of Earth on the Moon during lunar eclipses. Eratosthenes proceeded to use this information to measure circumference of Earth in the following manner; he knew that on a certain date that a stick placed in the ground at Syene cast no shadow. Whereas, a stick at Alexandria has a small shadow. Using simple ratios he showed the following:

  

  Geocentric model was so popular that it stood for 1500 years.

  Back to the Original Idea Alert:

  Cardinal Nicholas of Cusa (15th Century) through a lot about cosmology and came up with the following;

  • Every direction is relative
  • The Universe has its center everywhere
    The above two means there can be no UNIQUE place in the Universe
  • The Earth may not be stationary
  • Wherever one stood in the Universe, the same pattern of stars would be strewn out before them (homogeneity)

  Thus for the first time we see the ideas of relativity, homogeneity and non-uniqueness expressed.

  Copernicus embraces the non-uniqueness idea and then asks why should the earth be at the center - lets put the SUN there

  This is the First Heliocentric Cosmology

  Evolving Models of the Solar System and The Scientific Method:

  Galileo sees a mini solar system around Jupiter

  Tycho searches for stellar parallax sees none Aarogant rejection of Copernicun Model

  Tycho publishes data Kepler makes Geometrical Model

  • Summary of Kepler's Laws

  • Animated summary of Kepler's Laws

  Kepler's laws are only empirical they have no dynamical basis. Therefore, they would appear to be magic as they have no physical explanation (yet). (see page 16 in the book).

  Newton invents gravity, calculus but forgets about the speed of light

  Einstein invents causality and gravity as curved spacetime

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