iclicker quiz 6 Visibility of the Constellations at

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 Topics 1. 2. 3. 4. Moon phases Eclipses: shadows and visualizing the earth/moon/sun Solar calendars vs Lunar calendars. Distances and angles * Visualize in 3 D! * Ask “How do we know? ”

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?

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?

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?

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!

Background for i>clicker Quizzes: Siderial vs Solar Time 1. The earth orbits around the Sun and spins on its own axis in the same sense (i. e. both clockwise or both anticlockwise) 2. A siderial day is defined as the time it takes the Earth to make a complete spin on its axis relative to distant stars 3. A solar day is defined as the time it takes the Earth to do a complete spin on its axis relative to the Sun 1. The length of a siderial day is about 4 minutes shorter than the length of a solar day

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 opposite senses (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

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

1 - Moon phases

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

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?

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?

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?

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

The Earth/Moon/Sun Topics 1. Eclipses: shadows and visualizing the earth/moon/sun * Visualize in 3 D!

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!

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. )

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

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!)

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

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?

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

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.

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 (You can’t cast a shadow onto the light source. ) B- The Moon’s shadow falls on the Earth Moon does cast a shadow on Earth. C- The Sun’s shadow falls on the Moon (The light source can’t cast a shadow of itself. ) D- The Earth’s shadow falls on the Moon Earth casts a shadow on the Moon during a LUNAR eclipse. E- The Earth stops turning (I really hope not. What would stop it? What would restart it? ) F- The moon falls out of the sky. (I really hope not…) G- Birds fall from the sky (Better get indoors!) H- The Sun falls from the sky. (Better find another planet to live on. )

2 - Eclipses – Solar Photo of eclipse from orbit

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

i>clicker quizzes #9 and #10 (answers) As day progresses, moon moves in between earth and sun. . You observe a solar eclipse just before sun. SET, 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 sun. RISE, 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.

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

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

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

Kepler’s Three Laws of Planetary Motion 1. 2. 3. 4. Observe / Question Hypothesize / Explain Predict Test! A heliocentric model where planets move on ellipses = excellent predictions 5. 8_Planetary Orbit Simulator --Kepler's laws

Kepler’s Three Laws of Planetary Motion Kepler’s 1 st Law: All planets have elliptical orbits w/ the sun at one focus. (Eccentricity of Earth’s path = 1. 7%… nearly perfect circle. )

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. �

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. �

Kepler’s Three Laws of Planetary Motion Keplers 2 nd Law: A planets sweeps out equal areas in equal times (i. e. Moves fastest at perihelion and slowest at aphelion. ) 5. 8 Planetary orbit simulator kepler's 2 nd law

Kepler’s Three Laws of Planetary Motion Kepler’s 3 rd 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. distance 3 = 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.

Light and Energy Topics 1. How light (=energy) and matter interact

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

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

How light (= energy) and matter interact A. 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 eneutrons ……… 0 (neutral) • a neutral atom has net charge = 0 (#p’s = #e’s)

How light (= energy) and matter interact A. What is the structure of matter? Atoms = Nucleus + Electron cloud Nucleus contains protons (p) and neutrons(n) Electrons (e) sort of “orbit” the nucleus You won’t need to use this formula. Just notice the similarity to� gravitational Force. 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) !

How light (= energy) and matter interact A. 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 (H 2 O, CO 2)

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

How light (= energy) and matter interact A. What is the structure of matter? B. 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 Ground State QUANTIZED 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. .

How light (= energy) and matter interact A. What is the structure of matter? B. 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

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

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.

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

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

How light (= energy) and matter interact A. What is the structure of matter? B. How is energy stored in atoms? C. What is light: photons or waves? • A wave is a pattern of motion that can carry energy without carrying matter along with it • Wavelength = l distance between two wave peaks Frequency = f number of times per second that a wave vibrates up and down Speed of light = ALWAYS the SAME • • wave speed = wavelength x frequency wave speed = l * f

How light (= energy) and matter interact A. What is the structure of matter? B. How is energy stored in atoms? C. What is light: photons or waves? A particle of light, a photon, is like an energy packet. The energy carried by the photon is related to its wavelength and frequency. photon’s energy: Energy = [Constant] * frequency ……………goes UP if frequency goes up! Energy = [another constant] * 1/ wavelength … goes DOWN if wavelength goes up (longer distance between peaks)

How light (= energy) and matter interact A. What is the structure of matter? B. How is energy stored in atoms? C. What is light: photons or waves? Our eyes are photon detectors! Different energy photons are perceived as different COLORS Prisms bend the path of photons according to their energy. White light contains a continuum of energies (wavelengths).

Electromagnetic Spectrum: high energy (break down molecules, damage DNA, release e- in metals) Moderate energies (“visible” bandpass, aka “optical” bandpass) (the amounts of energy that release electrons from atoms) low energy (Can “shake” e-’s in metals, causing current in antennae, receivers, etc) (“radio waves” are photons, NOT sound!) f unit: hertz = #/sec = s-1 E=hf unit: e. V (= 1. 6 e-19 J) or Joules

2 - Line emission • From atoms -- electrons release photons with only certain energies – Each chemical (# p’s) has a unique set of energy levels that its electrons can occupy. (quantized energy levels!) – Electrons can move between levels: Get energy = absorb a photon, move to a higher level Lose energy = emit a photon, fall to a lower energy level

i>clicker quiz #13 • If a photon A has a longer wavelength (redder) than another photon B, then photon A has ______ than photon B – – – A- higher energy B- lower energy C- lower frequency D- higher frequency E- B and C

2 - Line emission • From atoms -- electrons release photons with only certain energies – Each chemical (specific # of p’s) has a unique set of energy levels that electrons in its atoms can occupy (quantized energy levels!) – Electrons can move between levels – Each chemical element has its own “fingerprint” of energy levels

2 - Line emission • From molecules – have additional energy levels because they can vibrate and rotate – This complicates their spectra… large numbers of vibrational and rotational energy levels Note different appearance of single lines vs “bands” of lines.

… and then what? … What happens to the photon after the atom/molecule in material releases it? Answer depends DENSITY If the material is TRANSPARENT ? then the photons can travel freely out of the matter. What is happening in this picture? What could I learn from the specific lines that I see?

… and then what? … What happens to the photon after the atom/molecule in material releases it? Answer depends DENSITY If the material is OPAQUE? then the photons bounce around, sharing their energy. They end up with a “thermalized” distribution of energies. An analogy for “thermalized” photons (energy): a single runner (photon) running down an empty street: her speed is whatever she wants moving down a crowded street: she bounces into the crowd, her speed gets closer and closer to the average speed of the people in the crowd.