of the Universe

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					1     Lecture 1: The Scientific Method/Overview
      of the Universe
    • Read chapter 1 in the textbook

    • Exercises: Do all Review and Discussion and all Conceptual Self-Test; Problems 1),
      2), 3)

1.1    The Scientific Method
    • cornerstone of the modern science – only ∼ 350 years old

    • observation central to the method – emphasis on empirical studies

    • built on a foundation of doubt not on faith or authority

    • scientists weigh evidence to quantify the level of doubt in an idea

    • From observations scientists can build a theory

    • Theory

        – set of ideas to provide a logical framework of explanation for observations
        – makes predictions about future observations
        – usually rooted on a simple principle

    Theories must possess the following characteristics:

    • Testability

        – theories must make specific predictions that can be falsified by observation
        – the strength of a theory rests in its falsifiability not its perceived correctness

    • Continual Testing

        – necessary to constantly challenge theories with new observations – experiments
        – can never prove a theory correct – the best we can say is that the theory fits all
          known observations
        – can never be sure that a future clever experimentalist will not find an observation
          that contradicts the theory

    • Consistency

        – if new phenomena implies the need for a new theory, the new theory must retain
          the good predictions of the previous one
        – logical tightrope act

        – series of approximations

   • Simplicity/Elegance

        – avoid unnecessary complexity – Occam’s razor
        – “simplicity” often results in elegance – complicated theory springs from simple
          underlying principles

Remember – everything in science is just a theory! Weighing evidence gives us the theories
in which we should have the most confidence. Theories that have stood the test of time
(many, many observational tests) have a strong foundation.

Extraordinary claims require extraordinary evidence!

   • theories come with a range or scale of applicability – not a weakness

   • connected to the consistency idea – each theory in a different range “contains” the old
     one as well

   • series of approximations

   • Example:

        – When you play baseball, you do not need to calculate the position or behaviour
          of all the atoms in the baseball or bat in order to determine where a fly ball will

   • we will see examples of this in our studies of astronomy

1.2    Overview of the Universe: A brillant past in front of us
   • The Universe is old, big, and growing

        – light travels at a finite speed, 300, 000 km/s
        – light takes time to get to us from distant objects
        – we see things as they were, not as they are
        – most distant source of light about 1023 km away
        – Hubble discovered that the Universe is expanding – the distance between galaxies
          (large collections of stars) increases with time
        – oldest light we can see is 13.7 billion years old
        – oldest Stars ∼ 10 billion years old
        – natural occurring radiation in the earth rocks suggest 4.5 billion years old fot the
          solar system

   • The Universe is smooth with uniform ingredients

        – on largest scales the universe looks like a smooth “dust” field – (the dust is a
          super large collections of stars
        – all stars and planets in the universe made of the same stuff – we will see how we
          know this in later lectures
        – Cosmological principle - no place is special (super Copernican view, more on this
          in the next lecture)

   • Dark Matter and Dark Energy !?

        – current mysteries – stuff out there not in the periodic table of elements
        – something is accelerating the Universe’s expansion – apparently the vacuum itself
          – we don’t understand nothin’
        – active area of current research

These topics will be discussed more in PHYS 1902, but you will see how some of these ideas
are related to the topics you will study in this course.


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