Structure and Evolution of the Universe Workshop.
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Transcript of Structure and Evolution of the Universe Workshop.
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Structure and Evolution of the Universe Workshop
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2nd Century: Claudius Ptolemy (physics of Aristotle)
View: Geostatic cosmology
Big Idea: Different laws for Earth and the cosmos
We can describe a model as a Paradigm, or our “World View”Astronomy has seen 3 major paradigms.
16th Century: Nicolaus Copernicus (physics of Newton)View: Heliocentric cosmology
Big Idea: Universal physics; same laws everywhere
20th Century: Edwin Hubble (physics of Einstein)View: Big Bang Cosmology
Big Idea: universe is changing, evolving
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Model
Observation
Success!Prediction
Failure!
Refine
How to use your model of the Universe:
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Model
Observation
Success!Prediction
Failure! Crisis!
How to use your model of the Universe:
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“The heavens are perfect and unchanging in Time.”
Aristotle
Claudius Ptolemy 100-170 AD Geostatic cosmology
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Prediction: Future planetary positions
Observation: retrograde motion of planets
Refine: epicycles
Success! For 1500 years
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Prediction: Phases of Venus
Observation: Full set of phases (Galileo) Crisis!
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Nicolaus Copernicus 1473-1543 Heliocentric cosmology
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Prediction: Future planetary positions
Observation: No better than Ptolemy
Refine: elliptical orbits (Johannes Kepler 1571-1630)
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Prediction: Observed shift in position of stars (parallax) as the earth Moves around the Sun.
Observation: No shift.
Crisis? No, but we had to wait until 1838 (Friedrich Bessel)
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Prediction: Sun at center of Cosmos
Observation: Sun is not at center of universe (1918)
The galaxy is not the entire universe (1923)
The universe is expanding (1929)
Crisis!
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Albert Einstein (1879-1955) Big Bang Cosmology
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Prediction: If denser, hotter, in past, should see evidence of left-over heat from early universe. Observation: Left-over heat from the early universe.
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Prediction: A dense, hot expanding universe, should be predominantly hydrogen, helium.
The Sun: 74.5% H, 24% He by mass Cecelia Payne 1900-1979
Observation: universe is ~75% hydrogen, ~25% helium by mass
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Prediction: An expanding universe is evolving over time. If we look at the early universe, it should appear different.
Observation: Distant galaxies less evolved, physically and chemically.
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Observation: 90% of matter is an unknown form: Dark Matter.
Refine: A new and unknown form of matter exists. But its gravity works the same way, and its presence is needed to explain how the universe looks.
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Observation: Expansion is accelerating.
Refine: Extra energy content (dark energy). A recent discovery and of unknown origin,the concept of dark energy is actually an integral part of Einstein’s theory of gravity.
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Conclusions• Big Bang model is our current paradigm or
“world view” of the universe.
• Anomalies, such as dark matter and accelerating expansion (dark energy), lead us to refine our model, but there is no crisis (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.