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Solar System. Spheres and Orbits. Gravity causes planets To be roughly spherical To orbit in ellipses To hold onto their matter Evidence for round Earth Pictures Horizon Logic Measurements. Eratosthenes 200 B.C. calculations. Gravity. Force of attraction between all objects
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Spheres and Orbits • Gravity causes planets • To be roughly spherical • To orbit in ellipses • To hold onto their matter • Evidence for round Earth • Pictures • Horizon • Logic • Measurements
Gravity • Force of attraction between all objects • Affected by mass and distance • More mass more gravity • Farther apart less gravity • Weight changes; mass does not • You weigh less on Mt. Everest • You weigh more on Jupiter
Magnetism • Swirling of liquid metal creates electricity • Outer core is liquid iron and nickel • Electricity creates a magnetic field • Magnetic field protects Earth from solar wind • Magnetic poles roughly line up with geographic poles
Rotation • Earth rotates every 24 hours • Causes day and night cycles • Creates need for time zones • Confirmed by Leon Foucault’s pendulum
Revolution • Earth revolves around the Sun once every year • Seasons and day length are affected by tilt of Earth’s axis • 23.5°
Moon • Studied directly 1969-1972 • Larger than any other moon of the inner planets • Formed by impact of small planet with Earth
Moon • Rotates and revolves every 27.3 days • No atmosphere • Daily temperatures range from 250° to -350° F • Some water mixed in with the soil • No weather no weathering
Giant Impact Hypothesis • 4.5 billion years ago • Planets collide debris orbits Earth eventually comes together to form Moon • Slowly moving away from Earth
Interior of the moon • Divided into layers like Earth • No tectonic activity because the interior has cooled too much
Satellite • Any body that orbits a larger body • Mix of falling and moving forward results in round orbits
Sun • 99.8% of all matter in the solar system • Average star • Made Hydrogen and Helium in a plasma state
Solar Layers • Core • 27,000,000°C • Nuclear fusion releases energy • Radiation zone • Energy moves away from the core • Convection zone • Hot particles rise and cooler particles sink • Convection: transfer of heat through the movement of heated particles
Solar Layers • Photosphere • Layer that we see • Radiates visible light • Chromosphere • Glows red with heat from the inner layers • Corona • Millions of miles thick • Only visible when photosphere is blocked
Solar Layers • The sun has no surface • Layers and zones can be detected but there are no clear lines • Like fire
Sunspots • Loops of magnetic energy make the Sun cooler in places • Form solar flares when the loops break • Solar flares release energy and particles • Solar wind • Produces aurora in Earth’s thermosphere • Solar prominence: plasma flows along the loop
Earth’s Rotation • Spin is counterclockwise when viewed from the North Pole • Sun, Moon, stars rise in the East and set in the West
Day-Night Cycles • Day: time required to rotate once • Length determined by whether the North or South is tilted toward the Sun • Longer days + Direct Sun = Summer • Shorter days + Indirect Sun = Winter • Equator: equal day length all year • Poles: six months day, six months night