Exploring the Universe

							       Exploring the Universe




"Astronomy compels the soul to look upwards
and leads us from this world to another."  -
                     Plato
  What’s in Our Solar System?


• Our Solar System consists of a
  central star (the Sun), the eight
  planets orbiting the sun, moons,
  asteroids, comets, meteors,
  interplanetary gas, dust, and all
  the “space” in between them.
The Relative Size of the Planets in
        the Solar System
How Big are these Objects?




  How Big is the universe?

What makes up the universe?
Galaxies
Stars
  Twinkle Twinkle, Little Star
• Twinkle, twinkle, little star,
  How I wonder what you are!
  Up above the world so high,
  Like a diamond in the sky.
  Twinkle, twinkle, little star,
  How I wonder what you are!
• When the blazing sun is gone,
 When the nothing shines upon,
  Then you show your little light
   Twinkle, twinkle all the night
    Twinkle, twinkle, little star,
   How I wonder what you are!
• In the dark blue sky you keep,
And often thro' my curtains peep,
   For you never shut your eye,
      Till the sun is in the sky.
• Twinkle, twinkle, little star,
 How I wonder what you are!
 Up above the world so high,
  Like a diamond in the sky.
  Twinkle, twinkle, little star,
 How I wonder what you are!
What is Cosmology?




 The Study of the Universe: its structure, origin, evolution, and destiny
Cosmology through the ages…




                 Universe models formed in many cultures
• Twinkle, twinkle, little star,
I found out just what you are.
You’re a fusing nuclear mass,
Made of Hydrogen and Helium
              gas.
   Twinkle, twinkle, little star,
 I found out just what you are.
Twinkle, Twinkle, Little Star (a
         new version)

  • Twinkle, twinkle, little star,
    I know what you really are:
     Giant ball of glowing gas,
     One of billions in a mass!
     Twinkle, twinkle, little star,
   Oh, how big you really are!
• Twinkle, twinkle, giant star,
 Larger than the Earth by far!
  Since your distance is a lot,
    You look like a tiny dot.
  Twinkle, twinkle, giant star,
   Very bright, yet very far!
• Stars are twinkling, everyone,
 Some are bigger than the sun!
    Just a twinkle in the sky,
Just because you're oh, so high!
   Twinkle, twinkle, little star,
   Oh, how big you really are!
Our View of the Universe- the story of scientific models

Astronomy has seen 3 scientific revolutions in cosmology

2nd Century: Claudius Ptolemy (Physics of Aristotle)
  Model: Earth-centered Cosmology



16th Century: Nicolaus Copernicus (Physics of Newton)
       Model: Sun-centered Cosmology



20th Century: Edwin Hubble (Physics of Einstein)
        Model: Big Bang Cosmology
               Big Idea: Universe is changing, evolving
Earth-centered Cosmology: Claudius Ptolemy, 100-170 AD




…“the natural motion of the Earth ….is towards the center of the universe;
that is the reason it is now lying at the center.”
                                                 Aristotle, On the Heavens
Sun-centered Cosmology: Nicolaus Copernicus 1473-1543




           “At rest, however, in the middle of everything is the Sun.”
                                   Nicholaus Copernicus, de Revolutionibus
•directions.
The Life Cycle of Stars…
    Poll Question:
What chemical elements
were created by the Big
        Bang?
   Use a stamp “X” to select the most
    abundant element in the universe.

neon      nitrogen   hydrogen    oxygen




helium     carbon     sodium       iron
    The Most Abundant Chemical
Elements  in the Universe and in Life

 In the Universe       In Life

     •   H              •   H
     •   He             •
     •   O              •   O
     •   C              •   C
     •   N              •   N
Testing the Big Bang model

Prediction:    The universe is expanding
Observation:    Galaxies are moving apart from each other (1929)
Testing the Big Bang model

Prediction: If the universe was denser, hotter, in past, we should see
evidence of left-over thermal energy from early universe.
Observation: Left-over thermal energy from the early universe.
(Penzias and Wilson, 1965)
Testing the Big Bang model

Prediction: A hot, dense expanding universe, should be
predominantly hydrogen, helium.
Observation: Universe is ~75% hydrogen, ~25% helium by mass




         The Sun: 74.5% H, 24% He by mass
Properties of the Universe
           • The Universe is
             expanding and
             continues to
             expand at an
             increasing rate
           • Almost all galaxies
             are moving away
             from us
           • Approximately 12-
             15 billion years old
       On a 1 year scale…
• each month equates to a billion years

• Solar System forms sometime in
  September

• Modern humans evolved 2 minutes
  ago!!! (December 31,11:58 pm)
Conclusions

• Big Bang model describes our current understanding
  of the universe.

• New discoveries, such as dark matter and accelerating
  expansion (Dark Energy), lead us to refine our model,
  but there is no crisis in our understanding (yet).

• Science is an ongoing process - forcing us to test
  our model through prediction and observation. The
  more tests it passes, the greater is our confidence in it.