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Chapter 1 Our Place in the Universe

Chapter 1 Our Place in the Universe. Star. A large, glowing ball of gas that generates heat and light through nuclear fusion. Planet. A moderately large object that orbits a star; it shines by reflected light. Planets may be rocky, icy, or gaseous in composition. Mars. Uranus.

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Chapter 1 Our Place in the Universe

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  1. Chapter 1Our Place in the Universe

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

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

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

  5. Asteroid A relatively small and rocky object that orbits a star Mathilde

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

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

  8. Nebula An interstellar cloud of gas and/or dust

  9. Galaxy A great island of stars in space, all held together by gravity and orbiting a common center M31, the Great Galaxy in Andromeda M31, the great galaxy in Andromeda

  10. One difference between the terms solar system and galaxy is that: • the solar system contains only one star but the galaxy contains many billions. • the solar system contains planets, but the galaxy does not. • other galaxies are rare, but other solar systems are common. • other solar systems are rare, but other galaxies are common.

  11. One difference between the terms solar system and galaxy is that: • the solar system contains only one star but the galaxy contains many billions. • the solar system contains planets, but the galaxy does not. • other galaxies are rare, but other solar systems are common. • other solar systems are rare, but other galaxies are common.

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

  13. Key Definition: Light-Year The distance light can travel in 1 year About 10 trillion kilometers (6 trillion miles)

  14. Put these objects in the correct order, from nearest to farthest from Earth: • The Sun, the Milky Way, Alpha Centauri, Pluto, the Andromeda galaxy • The Sun, Alpha Centauri, Pluto, the Andromeda galaxy, the Milky Way • The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy • Pluto, the Sun, Alpha Centauri, the Milky Way, the Andromeda galaxy

  15. Put these objects in the correct order, from nearest to farthest from Earth: C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy The sun – a star ~93 million miles away ~150 million kilometers ~ 8 light-minutes

  16. Put these objects in the correct order, from nearest to farthest from Earth: C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy Pluto – a “dwarf planet” ~3 billion miles away ~48 billion kilometers ~ 4.5 light hours

  17. Put these objects in the correct order, from nearest to farthest from Earth: C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy Alpha Centauri – a star ~26,000 billion miles away ~4.2 x 1013 kilometers ~ 4.5 light years

  18. Put these objects in the correct order, from nearest to farthest from Earth: C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy Milky Way – a galaxy ~200 billion stars ~100,000 light years across ~ 27,000 light years to center

  19. Put these objects in the correct order, from nearest to farthest from Earth: C. The Sun, Pluto, Alpha Centauri, the Milky Way, the Andromeda galaxy Andromeda – another galaxy ~400 billion stars ~2.5 million light years away

  20. Which is farther, the distance from San Francisco to Los Angeles, or the distance from you to the International Space Station, when it passes directly overhead? • San Francisco – LA is further • The space station is further

  21. Which is farther, the distance from San Francisco to Los Angeles, or the distance from you to the International Space Station, when it passes directly overhead? • San Francisco – LA is further!! • The space station is further

  22. In a scale model solar system that used a grapefruit to represent the Sun, how large would the Earth be? • The size of an orange • The size of a marble • The size of the point of a ballpoint pen • The size of a bacterium

  23. In a scale model solar system that used a grapefruit to represent the Sun, how large would the Earth be? • The size of an orange • The size of a marble • The size of the point of a ballpoint pen • The size of a bacterium

  24. In a scale model solar system that used a grapefruit to represent the Sun, how large would the Earth be? • The size of an orange • The size of a marble • The size of the point of a ballpoint pen • The size of a bacterium

  25. In a scale model solar system that used a grapefruit to represent the Sun, how far away would the Earth be? • 6 inches • 1 foot • 5 feet • 40 feet • 1 mile

  26. In a scale model solar system that used a grapefruit to represent the Sun, how far away would the Earth be? • 6 inches • 1 foot • 5 feet • 40 feet • 1 mile

  27. In a scale model solar system that used a grapefruit to represent the Sun, how far away would Pluto be? • 100 feet • 200 feet • 2,000 feet • 10 miles

  28. In a scale model solar system that used a grapefruit to represent the Sun, how far away would Pluto be? • 100 feet • 200 feet • 2,000 feet • 10 miles

  29. In a scale model solar system that used a grapefruit to represent the Sun, how far away would Pluto be? • 100 feet • 200 feet • 2,000 feet • 10 miles

  30. In a scale model solar system that used a grapefruit to represent the Sun, how far away should you put another grapefruit to represent Alpha Centauri, the next nearest star? • 10 feet • 1,000 feet • 1 mile • 10 miles • 1,500 miles

  31. In a scale model solar system that used a grapefruit to represent the Sun, how far away should you put another grapefruit to represent Alpha Centauri, the next nearest star? • 10 feet • 1,000 feet • 1 mile • 10 miles • 1,500 miles

  32. How can we know what the universe was like in the past? • Light travels at a finite speed ( 186,000 miles/second = 300,000 km/s).

  33. How can we know what the universe was like in the past? We see objects as they were in the past: The farther away we look in distance, the further back we look in time. Look far enough away, and we look back in time to when the universe was much younger…

  34. Example: This photo shows the Andromeda Galaxy as it looked about 2 ½ million years ago.

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

  36. How big is the universe? • The Milky Way is one of about 100 billion galaxies. • 1011 stars/galaxy  1011 galaxies = 1022 stars It has as many stars as grains of (dry) sand on all Earth’s beaches.

  37. 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.

  38. Earth rotates on its axis: • Once a day • Once a week • Once a month • Once a year • Once every 250,000 years

  39. Earth rotates on its axis: • Once a day • Once a week • Once a month • Once a year • Once every 250,000 years

  40. How is Earth moving in our solar system? Earth rotates around its axis once every day.

  41. Earth revolves around the Sun: • Once a day • Once a week • Once a month • Once a year • Once every 250,000 years

  42. Earth revolves around the Sun: • Once a day • Once a week • Once a month • Once a year • Once every 250,000 years

  43. 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, counter- clockwise as viewed from above the North Pole.

  44. The Moon revolves around Earth: • Once a day • Once a week • Once a month • Once a year • Once every 250,000 years

  45. The Moon revolves around Earth: • Once a day • Once a week • Once a moonth • Once a year • Once every 250,000 years

  46. Earth revolves around the Milky Way Galaxy: • Once a day • Once a week • Once a month • Once a year • Once every 230 million years

  47. Earth revolves around the Milky Way Galaxy: • Once a day • Once a week • Once a month • Once a year • Once every 230 million years

  48. Our Sun moves randomly relative to the other stars in the local solar neighborhood… • attypical 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.

  49. Are we ever sitting still? Earth rotates on axis: > 1,000 km/hr Earth orbits Sun: > 100,000 km/hr Solar system moves among stars: ~ 70,000 km/hr Milky Way rotates: ~ 800,000 km/hr Milky Way moves in Local Group Universe expands

  50. Why do we not feel or sense the various motions of Earth in the universe? • They are not real, they are just models • They are too slow to sense • They are nearly uniform, and you can not sense uniform velocity, only acceleration, which is a change of velocity or direction

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