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The Big Bang Evidence

The Big Bang Evidence. The Science of Creation. Cosmological Principle. Isotropy – The view from here is the same in all directions. (observation) Homogeneity – We live in an average place the same as any other. (statistics) This is the cosmological principle . Implies:

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The Big Bang Evidence

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  1. The Big Bang Evidence The Science of Creation

  2. Cosmological Principle • Isotropy – The view from here is the same in all directions. (observation) • Homogeneity – We live in an average place the same as any other. (statistics) • This is the cosmological principle. • Implies: • Universe has no edge! • Universe has no center!

  3. Olbers’ Paradox • Why is it dark at night? • In an infinite and unchanging universe: Every line of sight should end at the surface of a star. • Either: • Universe has edge. • Universe has a beginning.

  4. Concept Test • Olbers’ paradox asks why the night sky is dark, when every line of sight must eventually fall on a star. Which of the following reasons would best explain the darkness at night? It is because the universe is: • Infinite and mostly empty. • Clumpy, so not every sightline intercepts a star. • Expanding, so distant stars are red-shifted. • Young, so there are only stars to a finite distance. • None of the above.

  5. Scientific Evidence • A scientific model must do two things: • Explain what is seen. • Predict what will happen accurately. • Or, predict what can be seen before one thinks to look.

  6. Cosmic Microwave Background • The Big Bang: • Massive amount of energy. • Very high temperature  thermal radiation • As Universe expands: • Temperature cools  thermal radiation gets redder. or • Cosmological redshift  same thing.

  7. Origin of the CMB Once cool enough for atoms, radiation could move freely through space.

  8. The Temperature of Space • After 500,000 yrs: T=3000K lpeaka 1/T lpeak= near infrared. • The Universe was red. • After 16 billion yrs: Universe 1000x bigger. lpeak = 1000x longer. lpeak= microwaves (radio). T = 3K!

  9. Where do you look? • Recall Lookback time. • Universe is a time machine. • Look beyond the youngest galaxies. • Look everywhere.

  10. What We See

  11. Cosmic Microwaves • Big Bang theory predicted cosmic microwave background. • In 1965: discovery of radio waves (microwaves) from sky. • Prediction confirmed.

  12. COBE • Early 1990s: NASA Cosmic Background Explorer • Measure the intensity of radiation at many wavelengths. • 3K thermal emission! lpeak= (3 x 10-3 m/K) / 3 K = 0.001m = 1mm

  13. COBE cont. • Also measure the (temperature) intensity and wavelength in various directions. • Look for fluctuations out of which galaxies came. V = 600 km/s

  14. WMAP Large Scale Structure

  15. Concept Test • The cosmic background radiation is visible in every direction because: • We are at the center of the universe. • It is just now passing by us at the speed of light. • It pervades all space. • It has reflected in every direction over the age of the universe. • All of the above.

  16. Evidence of Eras • Can’t see what happened before origin of CMB. • Can estimate given change of temperature and density with time. • Look for Proof. • CMB (Age of Nuclei) • Ratio of H/He and Li (Age of Nucleosynthesis) • Weak Bosons (Electroweak Era)

  17. A Good Theory? • The Big Bang is a very successful theory. • Makes predictions: • CMB. • Hydrogen, Helium, Lithium abundances. • Formation of structure. • Expansion of Universe. • Are other Creation theories: • Scientific? • Successful?

  18. Homework #19 • For Monday, read NY Times article plus WMAP website: http://map.gsfc.nasa.gov/m_mm.html • Answer the following: • What is the inflation theory? • What new observations support the theory? • How does this theory change/help/augment the Big Bang theory?

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