1. In: pg 50 Before reading: As humans, we form theories all of the time. 1. What is a theory?

2. P1&4 Wed 9/30 p3&6 Thurs10/1 If you were absent last time you missed an activity. See me to make it up! Last day to make corrections on test is Thurs 10/1! That’s me! Big Bang lab

3. A scientific theory A scientific theory is when scientists have tested a group of related hypotheses many times and the hypotheses (remember, a hypothesis is an explanation for an observations about nature) are supported by data. Scientific ideas are not considered theories until they are generally accepted principles that explain a vast number of observations and experimental data. Examples of scientific theories include: the Atomic Theory, the Theory of Natural Selection, the Theory of Plate Tectonics as well as many other widely supported and accepted scientific principles. “They’re the big ideas in science,” explains Niles Eldredge, a paleontologist at the Museum of Natural History. “They’re taken very, very seriously.” Eugenie Scott, executive director of the National Center for Science Education, says, “Theories explain laws and facts. They’re the most important thing we do in science.” And Ken Miller, a biologist at Brown University and well- known lecturer on evolution, says a theory is the result of large collections of facts put into an explanatory framework.

4. Thru p51 After the reading: 1.What is a scientific theory? 2.How do scientific theories differ from the theories you form everyday?

5. The Big Bang Theory The Big Bang Theory is the dominant scientific theory about the origin of the universe. According to the big bang, the universe was created sometime between 10 billion and 20 billion years ago from a cosmic explosion that hurled matter and in all directions. The original matter was small and dense, but we don’t know what it was. The big bang was initially suggested because it explains why distant galaxies are traveling away from us at great speeds. The theory also predicts the existence of cosmic background radiation (the glow left over from the explosion itself). The Big Bang Theory received its strongest confirmation when this radiation was discovered in 1964.

6. After the reading 3. What does the Big Bang Theory explain? 4. What are 2 pieces of evidence supporting the Big Bang Theory?

7. How do we now if a star is moving towards us or away from us? We look at their spectral fingerprint. Remember--the pattern of lines tells us the gas composition of the star The way the lines are shifted tells us if a star is moving towards us or away from us and how fast it is moving. –Red-shift=moving away –Blue shift=moving towards

10. Is this spectrum red-shifted or blue-shifted? What way is this star moving relative to Earth?

11. Hubble’s Law By the late 1920s, Edwin Hubble had been taking spectra and measuring distances to a large number of galaxies. From each spectrum he learned the galaxy’s redshift, which told him how fast it was moving away from Earth, then he compared that with the object’s distance. What he found set the stage for much of 20th- century cosmology: the farther away the galaxy, the faster it receded. This relation—that a galaxy’s speed is directly proportional to its distance—became known as Hubble’s Law. It was observational proof that we live in an expanding universe, and it helped lay the foundation for the big-bang theory of the universe’s origin.

12. Thru 1: pg 52 Big Bang Balloon Read the direction sheet. Follow the steps and complete the data sheet. Tape in the data sheet.

13. Out p50 If a star or galaxy’s spectrum is red shifted, it is moving_____ from Earth. If it is blue-shifted, it is moving _____ Earth.