Chapter 1 Our Place in the Universe

Transcription

1 Chapter 1 Our Place in the Universe

2 Syllabus 4 tests: June 18, June 30, July 10, July 21 Comprehensive Final - check schedule Website link on blackboard

3 1.1 Our Modern View of the Universe Our goals for learning: What is our place in the universe? How did we come to be? How can we know what the universe was like in the past? Can we see the entire universe?

4 What happens if you miss a class? Points will be deducted from your grade Extra points will not be added to your grade I will you a warning I will miss you

5 What is my name? Dr. Allain Dr. Rhett Dr. Williams Dr. Blanchard Mrs. Moore Mr. Rhett

6 Success Tips Read the text (it is surprisingly good) (read before class) Do the online activities - I will give you a code Do the homework in the text Discuss with me and others Participate in class Don t have the goal of copying everything

7 Survey Questions

8 Learning Stuff School is like a gym I am the trainer You must do the work If you are not sore and sweaty, its not a good workout

9 My Goals Critical Thinking Key Ideas in Science: Energy Light Matter Forces Historical Perspectives on Science The nature of science

10 What is Farthest from us? The moon The sun Jupiter A star

11 What is our place in the universe? Our Cosmic Address

12 Star A large, glowing ball of gas that generates heat and light through nuclear fusion

13 Planet Mars Neptune A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition.

14 Moon (or satellite) An object that orbits a planet. Ganymede (orbits Jupiter)

15 Asteroid A relatively small and rocky object that orbits a star. Ida

16 Comet A relatively small and icy object that orbits a star.

17 A star and all the material that orbits it, including its planets and moons Solar (Star) System

18 Nebula An interstellar cloud of gas and/or dust

19 Galaxy A great island of stars in space, all held together by gravity and orbiting a common center M31, The Great Galaxy in Andromeda

20 Universe The sum total of all matter and energy; that is, everything within and between all galaxies

21 How did we come to be?

22 How can we know what the universe was like in the past? Light travels at a finite speed (300,000 km/s). Destination Moon Sun Sirius Andromeda Galaxy Light travel time 1 second 8 minutes 8 years 2.5 million years 1 Light year = distance light travels in one year

23 At great distances, we see objects as they were when the universe was much younger.

24 Can we see the entire universe?

25 1.2 The Scale of the Universe Our goals for learning: How big is Earth compared to our solar system? How far away are the stars? How big is the Milky Way Galaxy? How big is the universe? How do our lifetimes compare to the age of the universe?

26 On a 1-to-10 billion scale: Sun is the size of a large grapefruit (14 cm) Earth is the size of a tip of a ball point pen, 15 meters away. The scale of the solar system Relative Distance of the Nearest Star

27 How far away are the stars? On our 1-to-10 billion scale, it s just a few minutes walk to Pluto. How far would you have to walk to reach Alpha Centauri? A. 1 mile B. 10 miles C. 100 miles D. the distance across the United States (2500 miles)

28 How big is the Milky Way Galaxy? The Milky Way has about 100 billion stars. On the same ten billion-toone scale The Size of the Milky Way

29 Thought Question Suppose you tried to count the more than 100 billion stars in our galaxy, at a rate of one per second How long would it take you? A. A few weeks B. A few months C. A few years D. A few thousand years

30 Which of the following is the correct ordering from largest to smallest? Solar System, Milky Way, Local Supercluster, Local Group Milky Way, Solar System, Local Group, Local Supercluster Local Group, Local Supercluster, Solar System, Milky Way Local Supercluster, Local Group, Milky Way, Solar System Local Supercluster, Milky Way, Solar System, Local Group

31 Now let s step through the Universe in powers of 10: Zooming Out or Zooming In 26 Orders of Magnitude

32 How do our lifetimes compare to the age of the Universe? The Cosmic Calendar: A scale on which we compress the history of the universe into 1 year.

33 How is Earth moving in our solar system? Contrary to our perception, we are not sitting still. We are moving with the Earth in several ways, and at surprisingly fast speeds. Earth rotates around its axis once every day.

34 Earth orbits the Sun (revolves) once every year at an average distance of 1 AU 150 million km. with Earth s axis tilted by 23.5º (pointing to Polaris). and rotates in the same direction it orbits, counterclockwise as viewed from above the North Pole.

35 Our Sun moves randomly relative to the other stars in the local Solar neighborhood at typical relative speeds of more than 70,000 km/hr. but stars are so far away that we cannot easily notice their motion. And it orbits the galaxy every 230 million years.

36 How do galaxies move within the universe? Galaxies are carried along with the expansion of the universe. But how did Hubble figure out that the universe is expanding?

37 Hubble discovered that all galaxies outside our Local Group are moving away from us. the more distant the galaxy, the faster it is racing away. Conclusion: We live in an expanding universe.

38 What happens to the raisins in the Interactive Figure? They move apart and get bigger. They move apart and stay the same size. They do not move, but they get bigger. They get closer together and get smaller. They get closer together and get bigger. Raisin Cake