1. Making observations
Image credit: Fredrik, (C0)

2. What is the Big Bang Theory?
Image credit: Fredrik, (C0)

3. What is the Big Bang Theory?
George Lemaitre (a priest and physics professor) proposed the theory of the expanding universe.
13.82 billion years ago, violent expansion occurred from a single point, the size of an atom.
All matter and space were created; first quarks, electrons, protons, neutrons, atoms and larger elements.
For every million photons, 1 proton was made
*The “Big Bang” was a name (mockingly) given to Lemaitre’s idea – and it stuck 
Image credit: Fredrik, (C0)

4. Astronomy Notes The Universe ©Mark Place, 2009-2010

5. Big Bang Animation

6. What did the Big Bang sound like?
Forget the big bang, tune in to the big hum
THE big bang sounded more like a deep hum than a bang, according to an analysis of the radiation left over from the cataclysm. Physicist John Cramer of the University of Washington in Seattle has created audio files of the event which can be played on a PC. "The sound is rather like a large jet plane flying 100 feet above your house in the middle of the night," he says. Giant sound waves propagated through the blazing hot matter that filled the universe shortly after the big bang.
These squeezed and stretched matter, heating the compressed regions and cooling the rarefied ones. Even though the universe has been expanding and cooling ever since, the sound waves have left their imprint as temperature variations on the afterglow of the big bang fireball, the so-called cosmic microwave background. Cramer was prompted to recreate the din- last heard13.7 billion years ago- by an11-year-old boy who wanted to know what the big bang sounded like for a school project.
To produce the sound, Cramer took data from NASA's Wilkinson Microwave Anisotropy Probe. Launched in 2001, the probe has been measuring tiny differences in the temperature between different parts of the sky. From these variations, he could calculate the frequencies of the sound waves propagating through the universe during its first 760,000 years, when it was just 18 million light years across. At that time the sound waves were too low in frequency to be audible. To hear them, Cramer had to scale the frequencies 100,000 billion billion times.
Nevertheless, the loudness and pitch of the sound waves reflect what happened in the early universe. During the 100-second recording ( the frequencies fall because the sound waves get stretched as the universe expands. "It becomes more of a bass instrument," says Cramer.
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Author: Marcus Chown

7. What is the Big Bang Theory?
The universe started as a single point.
That point was extremely dense.
It became unstable and exploded outward.
Today the universe continues to expand.

8. The Doppler Effect

9. Evidence for the Big Bang
light from distance
galaxies all shift toward red

10. Shifts in the Electromagnetic Spectrum
Red Shift = away
Blue Shift = toward

11. Evidence for the Big Bang
Cosmic Background Radiation

12. Cosmic Microwave Background Radiation (CMB)
CMB is the “after glow” or “leftovers” from the big bang that permeates (spreads) in all directions of the universe.
Physicists agreed that CMB was leftover ‘heat’ in the form of microwave radiation, which was still cooling from the Big Bang.
Original temperature of the universe: 3000 Kelvin
Today, universe is approximately 3 Kelvin
The amount of cooling says how far the light has travelled, which determined the age of the universe: billion years.
Image credit: NASA, (C0)

13. Cosmic Microwave Background Radiation
The first sound of microwave radiation was thought to be pigeon droppings! :) Their detection of this CMB was made from a Horn Antenna!
COBE (Cosmic Background Explorer) was launched in miles from Earth. Detected the near perfect blackbody spectrum in 1992.
WMAP launched in In 2003, the WMAP satellite gave a better resolution of the small fluctuations of temperature
(WMAP = Wilkinson Microwave Anisotropy Probe)
Image credit: NASA, (C0)

14. Cosmic Microwave Background Radiation, continued
Image credit: NASA, (C0)
Planck satellite was a space observatory operated by the European Space Agency (ESA) from to 2013, providing us with the most accurate and detailed readings of Cosmic Microwave Background Radiation.

15. Evidence for the Big Bang
Expansion/red shift

16. Redshift of Galaxies
*Remember, red color has a longer wavelength than blue – therefore, it is moving away!
Image credit: NASA, (C0)

17. Evidence for the Big Bang
Quasars

18. 3. Quasars - super large (solar system size) galactic cores that put out more light than whole galaxies
Only found billion light years away
Found nowhere else
Nothing exists past them

19. Mixture of Elements
The matter in the universe is about 75% hydrogen & 25% helium.
•The abundance of H & He supports a particular process of past atomic creation, where the larger elements formed from the smaller elements.
Image credit: Cmglee, (CC BY-SA 3.0)

20. Summary
The big bang theory states the universe began the size of an atom and violently exploded outwards, eventually cooling and creating larger atomic elements.
Hubble's galaxy redshift observations shows that most galaxies are moving away from each other.
The distribution of cosmic microwave background radiation extends in all directions of the universe, which verifies predictions of universe cooling from a titanic, rapid expansion.
The abundance of lighter elements in the Universe, which suggests that these first elements (hydrogen and helium) were formed at the Big Bang and are the precursors for all other elements.

21. Review Questions (on a separate sheet of paper)
1. Write down three pieces of evidence that supports the Big Bang Theory.