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i>clicker quiz #6: Visibility of the Constellations at Different Times of the Year

i>clicker quiz #6: Visibility of the Constellations at Different Times of the Year. From the image below, what constellation is overhead at midnight on the Northern Hemisphere vernal equinox (March 21)? A- Virgo B- Pisces C- Sagittarius D- Gemini. Chapter 2 (2.3): The Earth/Moon/Sun.

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i>clicker quiz #6: Visibility of the Constellations at Different Times of the Year

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  1. i>clicker quiz #6: Visibility of the Constellations at Different Times of the Year From the image below, what constellation is overhead at midnight on the Northern Hemisphere vernal equinox (March 21)? A- Virgo B- Pisces C- Sagittarius D- Gemini

  2. Chapter 2 (2.3): The Earth/Moon/Sun Topics • Moon phases • Eclipses: shadows and visualizing the earth/moon/sun • Solar calendars vs Lunar calendars. • Distances and angles * Visualize in 3D! * Ask “How do we know?”

  3. 1- Moon phases • What determines the appearance of the moon? • What is moonlight? • Why does the moon rise in the east, set in the west? • Why does the moon’s appearance change?

  4. 1- Moon phases • What determines the appearance of the moon? • What is moonlight? Reflected sunlight! • Why does the moon rise in the east, set in the west? • Why does the moon’s appearance change?

  5. 1- Moon phases • What determines the appearance of the moon? • What is moonlight? Reflected sunlight! • Why does the moon rise in the east, set in the west? The earth spins! • Why does the moon’s appearance change?

  6. 1- Moon phases • What determines the appearance of the moon? • What is moonlight? Reflected sunlight! • Why does the moon rise in the east, set in the west? The earth spins! • Why does the moon’s appearance change? Because it ORBITS the EARTH!

  7. Background for i>clicker Quizzes: Siderial vs Solar Time • The earth orbits around the Sun and spins on its own axis in the samesense (i.e. both clockwise or both anticlockwise) • A siderial day is defined as the time it takes the Earth to make a complete spin on its axis relative to distant stars • A solar day is defined as the time it takes the Earth to do a complete spin on its axis relative to the Sun • The length of a siderial day is about 4 minutes shorter than the length of a solar day

  8. i>clicker quiz #7: Siderial vs Solar Time If the earth’s orbit around the Sun and the earth’s spin on its own axis were in oppositesenses (i.e. one clockwise and one anticlockwise), which of the following would be true: A. A siderial and solar day would be of the same length B. A siderial day would be 4 minutes longer than a solar day C. A siderial day would be 8 minutes longer than a solar day D. A solar day would be 4 minutes longer than a siderial day E. A solar day would be 8 minutes longer than a siderial day

  9. i>clicker quiz #8: Siderial vs Solar Time If the earth’s spin rate about its own axis were to slow down to half its present rate (while spinning in the same sense as its orbit around the Sun), so that the length of the day became ~48 hours, which of the following would be true: A. A siderial and solar day would be of the same length B. A siderial day would be 2 minutes longer than a solar day C. A siderial day would be 8 minutes longer than a solar day D. A solar day would be 4 minutes longer than a siderial day E. A solar day would be 16 minutes longer than a siderial day

  10. 1- Moon phases

  11. 1- Moon phases phases: new waxing crescent first quarter waxing gibbous full waning gibbous third quarter waning crescent new

  12. 1- Moon phases When does a FULL MOON rise? When does a NEW MOON rise? Does an astronomer on the moon see the Earth “rise” or “set”? Does he/she see phases of the Earth?

  13. 1- Moon phases When does a FIRST quarter MOON rise? When does a NEW MOON rise? For the picture at right, what is the phase of the Moon as seen from Earth?

  14. 1- Moon phases When does a FIRST quarter MOON rise? When does a NEW MOON rise? For the picture at right, what is the phase of the Moon as seen from Earth?

  15. 1- Moon phases When does a FIRST quarter MOON rise? When does a NEW MOON rise? For the picture at right, what is the phase of the Moon as seen from Earth? Crescent

  16. The Earth/Moon/Sun Topics • Eclipses: shadows and visualizing the earth/moon/sun * Visualize in 3D!

  17. 2- Eclipses • Lunar eclipse = Earth casts shadow on Moon (E between M & S) • Solar eclipse = Moon casts shadow on Earth (M between E & S) NOTE! Earth, moon, and sun are rarely perfectly aligned!

  18. 2- Eclipses – Lunar Partial vs Full shadows … the sun is not a dot! • Full = Umbra • Partial = Penumbra (our vantage point for these drawings is looking DOWN on the last slide.)

  19. 2- Eclipses – Lunar Total Lunar Eclipse, Jan 9/10, 2001

  20. 2- Eclipses – Lunar • Why does the moon appear red during a full lunar eclipse? • Blue light is scattered more efficiently Earth’s atmosphere (Daytime sky looks blue.) • Red light is scattered less efficiently (setting sun looks red) And the path of light (all colors) is bent by mass (general relativity!)

  21. 2- Eclipses – Solar • The Sun and moon are coincidentally same angular size when seen from Earth.

  22. 2- Eclipses – Solar • The Sun and moon are coincidentally roughly the same angular size when seen from Earth. • Why are Solar Eclipses so • much rarer than Lunar eclipses?

  23. 2- Eclipses – Solar As day progresses, moon moves in between earth and sun..

  24. Practice questions As day progresses, moon moves in between earth and sun.. During a solar eclipse: A- The Earth’s shadow falls on the Sun B- The Moon’s shadow falls on the Earth C- The Sun’s shadow falls on the Moon D- The Earth’s shadow falls on the Moon E- The Earth stops turning F- The moon falls out of the sky. G- Birds fall from the sky H- The Sun falls from the sky.

  25. Practice questions As day progresses, moon moves in between earth and sun.. During a solar eclipse: A- The Earth’s shadow falls on the Sun B- The Moon’s shadow falls on the Earth C- The Sun’s shadow falls on the Moon D- The Earth’s shadow falls on the Moon E- The Earth stops turning F- The moon falls out of the sky. G- Birds fall from the sky H- The Sun falls from the sky. (You can’t cast a shadow onto the light source.) Moon does cast a shadow on Earth. (The light source can’t cast a shadow of itself.) Earth casts a shadow on the Moon during a LUNAR eclipse. (I really hope not. What would stop it? What would restart it?) (I really hope not…) (Better get indoors!) (Better find another planet to live on.)

  26. 2- Eclipses – Solar Photo of eclipse from orbit

  27. i>clicker quizzes #9 and #10 You observe a solar eclipse just before sunSET, then the phase of the Moon must be: A- Full B- New C- First quarter D- Third quarter You observe a solar eclipse just before sunRISE, then the phase of the Moon must be: A- Full B- New C- First quarter D- Third quarter E- None of the above

  28. i>clicker quizzes #9 and #10 (answers) As day progresses, moon moves in between earth and sun.. You observe a solar eclipse just before sunSET, then the phase of the moon must be: B- New Solar eclipse = Moon between Earth and Sun. Must be a new Moon. Always. You observe a solar eclipse just before sunRISE, then the phase of the moon must be: E- None of the above You’re dreaming. Sun must be up in the sky to get a solar eclipse.

  29. i>clicker quiz #11 As day progresses, moon moves in between earth and sun.. You observe a lunar eclipse just before sunRISE, then the phase of the Moon must be: A- Full B- New C- First quarter D- Third quarter E- None of the above

  30. i>clicker quiz #11 (answer) As day progresses, moon moves in between earth and sun.. You observe a lunar eclipse just before sunRISE, then the phase of the Moon must be: A- Full Lunar eclipse = Earth between Moon & Sun. Must be a full Moon. Always.

  31. Solving the Mystery of Planetary Motion (use of the Scientific Method) * Visualize in 3D! * Ask “How do we know?”

  32. Kepler’s Three Laws of Planetary Motion • Observe / Question • Hypothesize / Explain • Predict • Test! A heliocentric model where planets move on ellipses = excellent predictions 5.8_Planetary Orbit Simulator --Kepler's laws

  33. Kepler’s Three Laws of Planetary Motion Kepler’s 1st Law: All planets have elliptical orbits w/ the sun at one focus. (Eccentricity of Earth’s path = 1.7%… nearly perfect circle.)

  34. Brief aside about ellipses: The ellipse is completely defined by: center, the eccentricity, and the length of the semi-major axis The focii are just geometrically defined points. The sun lies at one focus of elliptical orbit of each planet.

  35. Brief aside about ellipses: An ellipse is defined by: center, the eccentricity, and the length of the semi-major axis If eccentricity is 0… then the foci are at the center, and it’s a circle.

  36. Kepler’s Three Laws of Planetary Motion Keplers 2nd Law: A planets sweeps out equal areas in equal times (i.e. Moves fastest at perihelion and slowest at aphelion.) 5.8 Planetary orbit simulatorkepler's 2nd law

  37. Kepler’s Three Laws of Planetary Motion Kepler’s 3rd Law: The ratio of (a planet’s average distance from the Sun)3 to (its orbital period)2 is a constant for all the planets. distance3 = distance * distance * distance (time to orbit)2 = (time to orbit) * (time to orbit) A planet that is close to the Sun, completes an orbit in a shorter period of time than a planet that is farther from the Sun.

  38. Light and Energy Topics • How light (=energy) and matter interact

  39. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? What is light?

  40. How light (= energy) and matter interact What is the structure of matter? Atoms = Nucleus + Electron cloud Nucleus contains protons (p) and neutrons(n) Electrons (e) sort of “orbit” the nucleus

  41. How light (= energy) and matter interact What is the structure of matter? • Atoms = Nucleus + Electron cloud • Nucleus contains protons (p) and neutrons(n) • Electrons (e) sort of “orbit” the nucleus • these particles have “charge” • electrons ….. -1 e- (defines a fundamental unit of charge) • protons ……. +1 e- • neutrons ………0 (neutral) • a neutral atom has net charge = 0 (#p’s = #e’s)

  42. How light (= energy) and matter interact What is the structure of matter? • Atoms = Nucleus + Electron cloud • Nucleus contains protons (p) and neutrons(n) • Electrons (e) sort of “orbit” the nucleus • q= charge • r = distance between • like charges repel each other, opposite charges attract • atoms will attract electrons until net charge = 0 (#p’s = #e’s) ! You won’t need to use this formula. Just notice the similarity togravitational Force.

  43. How light (= energy) and matter interact What is the structure of matter? • Atomic Number = # of protons in nucleus • Atomic Mass Number = # of protons + neutrons • Molecules: consist of two or more atoms (H2O, CO2)

  44. How light (= energy) and matter interact What is the structure of matter? • Isotope: same # of protons but different # of neutrons. (4He, 3He)

  45. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? Excited Electron States If there is a FORCE (gravitational or electromagnetic) , there can be STORED ENERGY. STORE energy = go to high potential energy. RELEASE energy = “fall” back down Key point: The states available to electrons in atoms are QUANTIZED Ground State Electrons in an ATOM can only have “sit” at specific energy levels, which are determined by the #n’s and #p’s in the nucleus..

  46. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? Energy level transitions: The only allowed changes in energy for an electron while it is still trapped in the atom are those corresponding to a transition between energy levels Not Allowed Allowed

  47. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? What is light? Light = energy (sunlight feels warm!) Energy unit: Joule Flow of energy: Watt = 1 Joule / second The flow of energy is the rate that energy is … moving … delivered to earth example: rate that energy is used in a lightbulb rate that energy (aka photons aka sunlight) hits the earth from the sun

  48. i>clicker quiz #12 • When a photon interacts with an atom, what changes occur in the atom? A) The atomic number increases. B) The nucleus begins to glow. C) An electron changes its orbital energy. D) The photon becomes trapped, orbiting in the atom.

  49. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? What is light: photons or waves? • Light = energy • (sunlight feels warm. The light that hits your skin delivers energy!) • You can think of light as WAVE or as a PARTICLE : “wave/particle duality” • a particle (i.e. a photon) --- because it acts like a “packet” of energy. • a wave --- because it moves like a wave moves (mathematically convenient)

  50. How light (= energy) and matter interact What is the structure of matter? How is energy stored in atoms? What is light: photons or waves? • “wave/particle duality”

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