1. Chapter 30-4 The Big Bang Theory

2. Chapter 30-4 Objectives Chapter 30-4 vocabulary
E5.1b – Describe how the Big Bang theory accounts for the formation of the universe.
E5.1c – Explain how observations of the cosmic microwave background have helped determine the age of the universe.
E5.1d – Differentiate between the cosmological and Doppler red shift.
Chapter 30-4 vocabulary
Cosmology – study of the origin, structure, properties, processes, and future/evolution of the universe
Big Bang theory – theory stating that all matter and energy that exists in the universe was compressed into an extremely small volume that exploded 13 to 15 billion years ago
Cosmic background radiation – low levels of energy evenly distributed throughout the universe; this was discovered in 1965 and astronomers think it formed shortly after the big bang

3. Chapter 30-4 vocabulary cont.
Absolute zero – minus 273 oC, the coldest temperature possible; cosmic background radiation has a temperature that is 3 oC warmer
Dark matter – a form of matter that makes up 23% of all matter in the universe; it gets its name because it does not give off light but we can detect its gravity (the matter that we know of that makes up the stars, planets and the matter between the stars only accounts for about 4% of all matter within the universe
Dark energy – astronomers think that most of the universe is composed of material that we know almost nothing about; they think it is a force that opposes gravity;

4. Cosmology shows that over time, in an expanding universe, all galaxies move away from each other. This expansion and moving apart will continue until even the closest galaxy to our Milky Way will just look like a small white spot through a telescope.

5. Edwin Hubble
Near the end of the 1920’s, observations made by Hubble showed that most of the stars and galaxies spectra that he observed were shifted to the red, except for those closest to Earth. By examining their red shift he calculated how fast they were moving away. Those farthest from Earth were moving the fastest. By using Hubble’s observations astronomers were able to determine that the universe is expanding!

6. The Big Bang Theory
The diagram below shows the time from the big bang up until now. As you can see, in seconds the universe went from an extremely tiny ball of matter and energy to a size many times through a process called infaltion.
1027 oC oC ,000oC oC oC

7. Cosmic Background Radiation
This was first discovered in 1965 at Bell Lab’s in New Jersey by Penzias and Wilson. This formed shortly after the big bang and shows that the sky has energy evenly distributed throughout it which helps support the Big Bang Theory. This energy is at a temperature of -270oC or 3 Kelvin. Even though it is fairly even there are some “ripples” that are noticed. Astronomers think that these “ripples” indicate the formation of the first galaxies in the newly forming universe.

8. Dark Matter
The “ripples” discussed on the previous slide have been analyzed and what the findings show is that the kinds of matter that we are all familiar with make up only about 4% of the total matter in the universe. Through observations and mathematical calculations astronomers have determined that 23% of the universe is composed of dark matter, matter that doesn’t give off light but does exert a gravitational on nearby objects.
                                                
Rotation curve of a typical spiral galaxy: predicted (A) and observed (B). Dark matter can explain the velocity curve having a "flat" appearance out to a large radius

9. Dark Energy
Observations of distant galaxies suggest that they are farther from us than what current theory has predicted.
                                                           
As this NASA chart indicates, roughly 70 percent or more of the universe consists of dark energy, about which we know next to nothing.

10. Dark Energy cont.
Due to this excess distance, astronomers have concluded that there is some unseen force that is pushing galaxies apart.
Due to dark energy the universe is not only expanding but is also accelerating!