Astronomy: Earth, Sun & Moon Overview & Objectives Know about the Earth, Inside & Out Interior, Plate Tectonics, Atmosphere, Magnetic Field Know about the Moon: Earth’s Fellow Traveler Size, Distance, Orbit, Composition, Origins Know about the Sun Size, Distance, Energy, Composition Understand the Relationship b/w Earth, Sun, Moon Eclipses, Seasons Chapter 2, Lesson 1 & 2 Chapter 3, Lesson 1

Earth’s Interior 3 Layers: Crust Mantle Core Chapter 2, Lesson 1

Earth’s 3 Layers Crust - outer layer (only 60 miles thick) Mantle – middle layer 1,800 miles thick (½ way to center) Solid, but can flow slowly Core – center Denser than mantle (iron & nickel) Liquid outer core Solid inner core Chapter 2, Lesson 1

Motion of the Earth’s Crust Do the continents move? Continental drift - gradual motion of the continents relative to one another Why do they move? Chapter 2, Lesson 1

Motion of the Earth’s Crust Plate tectonics - motion of sections (plates) of Earth’s crust across the underlying mantle But what causes the plates to move?

Plate Tectonics Convection of heat in Mantle Explains much of Earth’s features & topography Mountains Volcanoes Earthquakes Ocean mountains/trenches Rift zone - line near center of the oceans - lava flows upward Mid Atlantic Ridge & Mid Oceanic Rise Chapter 2, Lesson 2

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Plate Tectonics Earthquake Locations Chapter 2, Lesson 2

Earth’s Atmosphere Very thin onion skin (only 90 miles) 4 layers Composition? Mostly nitrogen & oxygen All weather occurs in: Troposphere (7-8 miles) Ozone layer Protects us from fatal ultraviolet (UV) radiation from Sun

Earth’s Magnetic Field Caused by Uses: Compasses Protects us from harmful sun rays Magnetic poles shift each year (can flip!) iron core

Earth’s Magnetic Field Charged particles from Sun are captured by Earth’s magnetic field (Van Allen Belts) Aurora (Northern & Southern Lights) Light radiated from impacts of charged particles Video

Moon’s Size & Distance Diameters Earth – 7,800 miles Moon – 2,160 miles Comparison? About ¼ size of Earth Moon distance from Earth 240,000 miles Activity Chapter 2, Lesson 2

Moon’s Orbit Moon’s orbit is elliptical Appears larger at perigee Closest distance Appears smaller at apogee (farthest distance) How long to orbit the Earth? One “Moonth” (month)! 27.3 days Why do you always see same face of the Moon? Rotates 1 time per orbit

Moon’s Orbit Phases Causes Tides on Earth: Full, New, Quarter Moons Waxing & waning? Causes Tides on Earth: Moon’s gravity pulls on Earth causing “bulges” in oceans Chapter 2, Lesson 2

Moon’s Composition Crust 62 miles thick Moonscape: Maria (singular “Mare”) “Seas” - Lunar lowlands Impacts from meteorites that filled craters in w/ lava Highlands Mountains - result of millions of ancient craters piled up on top of one another

Moon’s Origin - 4 Theories Double Planet Theory – Moon formed at same time as Earth Fission Theory - material spun off from Earth Capture Theory Large Impact Theory Large object impacted the Earth Metal cores combined to form massive Earth core Lighter material thrown off became the Moon - space debris was captured by Earth Chapter 2, Lesson 2

Size & Distance of the Sun 865,000 miles diameter You could fit 1,000,000 Earths in the Sun! 93,000,000 miles from Earth! Remember activity? 200 mi = 1”? Sun = 360’ 7.3 Miles away 8 mins at speed of light Earth Chapter 2, Lesson 2

Composition of the Sun “The FURNACE” ¾ of Sun is Primary source of Sun’s energy: Atom nucleus - protons & neutrons Nuclear fusion – 2 nuclei “fuse” to form a larger nucleus Incredible gravity at center of Sun fuses protons = Heat source Hydrogen, the rest is mostly Helium nuclear fusion reactions

Sun’s Atmosphere 3 Main Layers: Photosphere Chromosphere Region where solar flares erupt Corona - Outermost region - Extends 100,000 miles - visible part that emits light - region b/w photosphere & corona

Sun’s Atmosphere “The Solar Wind” Solar wind – a continuous outflow of charged particles from the Sun What protects Earth? Its magnetic field & atmosphere Flying out at 249 miles/sec! Significant role in space weather activity Causes Aurora Borealis Chapter 3, Lesson 1

Sun Spots and Flares Sunspots - dark spots appearing periodically in groups on surface Effect on Earth? Cooler climates Solar Flares Solar flares – a surface explosion Ejected 1,000s of miles into space Effect on Earth? Can disrupt satellites & radio transmissions

Earth & Sun Relationship: Seasons Why are there seasons? .... 2 reasons: Earth is “tilted” Rotation Video 1 Star Spin Video 2 Actual Spin Earth orbits the Sun: 23.5° 24 hours (1 Day) 365.25 days (1 Year)

Earth & Sun Relationship: Seasons Solstices Summer & Winter Sun farthest distance from the “celestial equator” Longest & shortest days of the year Equinoxes Vernal (Spring) Autumnal (Fall) Sun crosses “celestial equator” Night/day are equal

Earth, Moon & Sun Solar Eclipses Sun about 400x larger than the moon… But Sun is about 400x farther away than the moon So, they appear the EXACT SAME SIZE on Earth!!! Certain times the Moon perfectly covers the Sun Chapter 3, Lesson 1