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.
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