Cosmology
Cosmology is the study of the universe. What is it s structure? How did it originate? How is it evolving? What is its eventual fate?
ANCIENT COSMOLOGIES
The Ptolemaic Universe Claudius Ptolemy (100-170 AD) A geocentric model Different rules govern the terrestrial and celestial spheres Heavily influenced by Aristotelian philosophy
Testing the Earth-Centered Model Prediction: Future planetary positions Observation: Retrograde motion of planets Refine: Epicycles
Testing the Earth-Centered Model Prediction: Phases of Venus Observation: Venus has a full set of Phases
The Copernican System Nicolaus Copernicus (1473-1543) in the midst of all stands the Sun. A heliocentric For who model could in this most beautiful temple place this lamp in another or better Physics is universal Supported by place observations than that of from Tychowhich Brahe it and can at Galileo the same Galilei time illuminate the whole?
The Copernican System and Retrograde Motion The Motion of Mars
Laws of Planetary Motion Johannes Kepler (1571-1630) Orbits of planets are not perfect circles. (1602) Orbits are ELLIPTICAL. Allows more accurate prediction of planetary position.
Laws of Planetary Motion Johannes Kepler (1571-1630) FIRST: Law of Ellipses SECOND: Law of Equal Areas THIRD: Law of Periods
Failures of the Copernican System The sun is NOT the center of the universe. The Milky Way is not the WHOLE universe. The universe is not in steady state
Big Bang Cosmology Albert Einstein (1879-1955) Universe is changing, evolving through time Stephen Hawking
Evidence for an expanding universe Hydrogen lamp The spectrum of hydrogen gas
Evidence for an expanding universe Orion Nebula When we see a repeat of the pattern we saw in the lab, we know hydrogen is present
Evidence for an expanding universe Galaxy UGC 12915 Recession Velocity: 4350 km/s We see the same repeating pattern of lines in a galaxy, but displaced to the red
Evidence for an expanding universe Galaxy UGC 12508 Recession Velocity: 9100 km/s The further away the galaxy, the more the shift to the red
Evidence for an expanding universe Galaxy KUG 1750 Recession Velocity: 15400 km/s The greater the red shift, the faster the galaxy is receding
Evidence for an expanding universe Galaxy KUG 1217 Recession Velocity: 31400 km/s The red shift is caused by the expansion of space.
Testing the Big Bang Model Prediction: If the universe was denser, hotter, in the past, we should see evidence of left-over heat from early universe Observation: Left-over heat from the early universe (Penzias and Wilson, 1965) with the use of WMAP (Wilkinson Microwave Anisotropy Probe)
Testing the Big Bang Model Prediction: A hot, dense expanding universe, should be predominantly hydrogen and helium Observation: Universe is ~ 75% hydrogen, ~ 25% helium by mass The Sun: 74.5% H, 24% He by mass
Testing the Big Bang Model 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
Testing the Big Bang Model Prediction: 90% of matter is an unknown form: Dark Matter Observation: 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 Vera Rubin
Testing the Big Bang Model Observation: Expansion is accelerating Refine: Extra energy content A recent discovery and of unknown origin, the concept of Dark Energy is actually an integral part of Einstein s theory of gravity.
Evidence of Dark Matter A Supernova A dying star becomes a white dwarf. (Ring Nebula, Messier 57)
Evidence of Dark Matter A Supernova The white dwarf strips gas from its stellar companion.
Evidence of Dark Matter A Supernova Seen by Johannes Kepler in 1604, 5 years before the invention of the telescope..and uses it to become a hydrogen bomb. Bang! Image is a composite from 3 space telescopes Hubble (yellow), Chandra (blue and green) and Spitzer (red)
Evidence of Dark Matter A Supernova The explosion is as bright as an entire galaxy of stars.
Evidence of Dark Matter A Supernova..and can be seen in galaxies across the universe.
Dark Energy 73%
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.