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The Big Bang Theory

The Big Bang Theory. The Big Bang Theory. Another Cosmological Model. 2 nd Century: Physics of Aristotle Earth is at the center of everything Earth and space have different laws governing them 16 th Century: Physics of Newton Sun is at the center of everything

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The Big Bang Theory

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  1. The Big Bang Theory

  2. The Big Bang Theory

  3. Another Cosmological Model • 2nd Century: Physics of Aristotle • Earth is at the center of everything • Earth and space have different laws governing them • 16th Century: Physics of Newton • Sun is at the center of everything • Same laws for Earth and space • 20th Century: Physics of Einstein • Sun is just one star, not at the center of anything except the solar system • Universe is changing / evolving

  4. Theory • A well-established idea that is supported by scientific evidence.

  5. Evidence 1: The Universe Is Expanding • Observation: Galaxies are moving apart from each other • How do we know?? • The pictures show the spectrum for hydrogen and the spectra from the Orion Nebula and Galaxy UGC12508. • You can see that the H-lines are present but shift towards the longer wavelengths… Redshifting.

  6. Conclusion… • Galaxies are traveling away from us. The speed, or recessional velocity, can be calculated based on the redshift of the hydrogen lines.

  7. Evidence 2: Background Radiation • Observation: There is left-over heat (radiation) from the early universe. • Penzias & Wilson discovered it in 1965. • The WMAP (Wilkinson Microwave Anisotropy Probe) shows the unequal distribution of matter (temperature & density) in the universe. • Red: more dense, higher temperature • Dark Blue: less dense, lower temperature

  8. Comparison of the level of detail of fluctuations in the CMBR • CMBR: Cosmic Microwave Background Radiation

  9. Evidence 3: Hydrogen & Helium are the main 2 elements • Observation: The universe contains about 75% hydrogen and about 25% helium. • Astronomers analyze the spectra from stars, nebulae, and galaxies to determine what elements and in what amounts exist in space. • Heavier elements, up to iron, are formed in the core of a massive star due to nuclear fusion. Even heavier elements are formed during supernova explostions.

  10. Evidence 4: The universe is evolving over time • Observation: Distant (older) galaxies are both physically and chemically less evolved than younger galaxies • The light we see from galaxies may be from millions to billions of years ago. The picture shows galaxies at different ages. • The older galaxies are more spread out, smaller, and contain fewer heavy elements. • Scientists analyze the spectrum to determine what elements are present.

  11. 90% of Matter is in an Unknown Form • A new and unknown form of matter exists. Its gravity works the same as the gravity for “normal” matter. • Fritz Zwicky first detected dark matter between galaxies in 1933. • Vera Rubin found that dark matter exists in galaxies in 1978. • Normal matter would not be able to clump together to form stars and galaxies without dark matter.

  12. Expansion is Accelerating • There must be extra energy to allow the universe to speed up rather than slow down. • Einstein’s theory of gravity accounted for “energy of space”, which turns out to be Dark Energy. • About 70% of energy is dark energy, 26% is dark matter, and only 4% is normal matter.

  13. Supernovae Used as Distance Indicator • All Type Ia supernova produce the same amount of energy and therefore have the same absolute magnitude. • Combining that with the apparent magnitude, brightness as seen from Earth, the distance can be calculated.

  14. Creating a White Dwarf • Lower mass stars, like our Sun, make white dwarfs at the end of their life. • The Sun will run out of nuclear fuel in about another 5 billion years. • Binary stars are pairs of stars and are fairly common. They make up about 2/3 of all the stars in a galaxy.

  15. White Dwarfs Adds Mass • A white dwarf in a binary star system “steals” gas from its companion star.

  16. Supernova Explosion!! • Again… explosion has a predictable and reproducible brightness. • Knowing the absolute magnitude and the apparent magnitude allows astronomers t calculate distance. • Kepler saw type Ia supernova in the Milky Way galaxy in 1604.

  17. The image is a composite using • Hubble (yellow), • Chandra (blue & green), • Spitzer (red).

  18. Detecting Supernovae • Computer software analyze images to find supernovae in distant galaxies. • Notice the circled area has increased in brightness in the 2nd image. • The 3rd image is the difference in brightness from the first 2 images. • Helps astronomers calculate distance.

  19. Detecting Dark Energy • Astronomers use the rate of expansion in the universe to determine how much dark energy exists. • Recall that Einstein’s Theory of Gravity relates the expansion rate of the universe to the total amount of all forms of mass or energy in the universe.

  20. Big Bang Model • Strong, well-supported model • Incorporates all observed evidence. • No evidence has been found to contradict it. • Many questions still remain…

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