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  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

The rotation of the Earth

Revolution  Earth revolves around the Sun once every year  Causes the seasons  Shorter days during winter  Seasons and day length are affected by tilt of Earth’s axis  23.5°

What is the season?

Moon  Studied directly  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

Seasons  Length of day changes with seasons  Angle of sunlight changes with seasons  Sun directly overhead = More direct light  More direct light = More heat  Longer days + Direct Sun = Summer  Shorter days + Indirect Sun = Winter

The path of the sun in the sky

Solar Eclipse  Moon moves between the Earth and Sun  Photosphere is blocked  Corona becomes visible  Earth gets dark for a few seconds  Aug. 21, 2017

Lunar Eclipse  Earth between Sun and Moon  Moon goes dark because it does not make its own light  Shadow of Earth can be seen on the Moon  Proof that Earth is round  Sep 28, 2015

Phases of the Moon  Moon reflects sunlight  We only see the part of the Moon that is both facing the Sun and the Earth  This means the visible portion of the Moon is constantly changing

The phases of the Moon

Tides  Caused by the pull of the Moon on the oceans  Sun also affects the tides  Spring tide  Extreme tides; higher high, lower low  Neap tide  Moderate tides; lower high, higher low