ASTRONOMICAL CYCLES

ASTRONOMICAL CYCLES

1. The Earth's Tilt + Orbit of earth around Sun.

   • The earth's axis is tilted at a 23.5 degrees angle.
   • SEASONS
     • The tilted axis of the earth gives us seasons. As earth travels around its year-long orbit of the sun, the North Pole leans first towards the sun (exposing it loser to the sun's light and bringing warm summery days, and, months later, tilts away from the sun and expereinces the opposite. This causes the Northern part of the earth warmer and then cooler. The South Pole points the opposite way to the North Pole, therefore the Northern and Southern hemispheres have opposite seasons.
       • EQUATOR SEASONS: Regions on or near the equator enjoy hot weather all year round (because the equator does not tilt away from the sun during the year) while regions further North or South of the equator have distinct wet and dry seasons.
       • THE FOUR SEASONS! When the North Pole is tilted towards the Sun, regions within this hemisphere have summer while the Southern hemisphere has winter. As the earth continues on its orbit, the seasons vary to Autumn in the Northern Hemisphere and Spring in the Southern Hemisphere. Alternately, when the Southern Hemisphere is tilted towards the sun, it experiences summer while Northern Hemisphere regions enjoy winter. This process gradually continues with the Southern Hemisphere having Autumn and the Northern Hemisphere having spring. The earth continues around the sun...
     • EQUINOX: when the sun crosses the celestial equator (twice a year) resulting in day and night of equal length. SOLSTICE: This is when the sun is at the highest (summer solstice) or lowest (winter solstice) point in the sky meaning longest and shortes days of the year respectively.
   • ECLIPSES
   • CHANGES IN DAYLENGTH

2. The Earth's Spin

   • DAY AND NIGHT
     • The earth spins around its own axis once every 23.93 hours (approx. 1 day)
     • While earth's orbiting the sun it is simultaneously spinning around its own axis (which occurs every 23.93 hours)- this results in our day and night- one half of the earth faces the sun, while the other side is dark.

3. The Orbit of the Moon around the Earth

   • FORMATION OF TIDES- NEAP AND SPRING TIDES
     • The moon's gravity pulls on the earth's oceans- distorting them which subsequently causes tides.The water which is on the side of earth currently facing the moon experiences the most forceful GRAVITATIONAL FORCE OF THE MOON, and bulges outwards (high tide). However, the water on the opposite side of the earth to the moon also bulges due to the ROTATIONA FORCE FROM SPIN OF EARTH (flung out)- these two bulges follow both the motion of the moon (tides similarly follow 28 day cycle) and the rotation of the earth (as the earth spins eastwards on its axis, the bulge westward.) Tides rise and fall twice ever 24 hours and 50 minutes (high and low tides), so high and low tides occur fifty minutes light each day. This is because the moon is moving as well as the earth so therefore it takes slightly longer to create high tide (50 minutes).
     • NEAP TIDE (weak tide): the pull of the moon and the sun affects the earth's tides. The lowest (neap) tides occur when the sun and moon pull at right angles to each other and as a result their pulls partially cancel each other out. (ropes puling on right angle). Two spring tides p/lunar cycle. SPRING TIDE (extra strong tide): When the sun and moon line up with each other (twice a month) in space, their graivties combine together, creating the highest (spring) tides. (ropes pulling together). Two neap tides p/lunar cycle.
   • • SOLAR ECLIPSE: A solar eclipse is when the moon passes between the earth and the sun- consequently blocking either all (total solar eclipse) or a portion (partial solar eclipse) of the sun. 2-5 solar eclipses can be viewed from somewhere on earth annually. WHAT HAPPENS? during totality (when the sun is completely covered)- day becomes night, the air gets colder, and birds roost. Totality can last up to 7 and a half minutes but is usually much shorter than this. During this time, the pink inner area of the sun (chromosone) appears. Additionally the corona (pearly white outer atmosphere of the sun) is visible and this can be sometimes viewed around the moon's edge.
     • Eclipses occur as a result of both THE EARTH'S ORBIT AROUND THE SUN as well as THE ORBIT OF THE MOON AROUND THE EARTH.
     • LUNAR ECLIPSE: A lunar eclipse, contrastingly, occurs as a result of the earth coming between the moon and the sun and subsequently the earth's shadow totally or partially obscures the moon. 2-5 lunar eclipses may appear annually. WHAT HAPPENS? During a total Lunar eclipse, the atmosphere is not completely dark in the moon's absence. Instead, the moon reflects a small amount of sunlight refracted from the earth's atmosphere. This refracted light is frequently reddish in colour.
   • PHASES OF THE MOON
     • Our changing views of light on the moon are called phases. Similar to earth, one half of the moon is constantly lit up by the sun, whilst the other side is dark. As the moon orbits the earth we view it from varying angles with its lit side facing either towards or away from us.
     • HOW DO THE PHASES WORK? The phases begin when the Moon comes between the Sun and Earth. The bright side of the moon is facing away from us and we see the dark near side. We call this the new moon. As the moon moves along its orbit, we see more and more of the near side lit up, until we see it all lit up at full moon. Then we see less and less of the moon lit up, until it shrinks to a crescent and then disappears at the next moon.
     • When the moon seems to grow in size from night to night, we say it is waxing. When it seems to shrink, we say it is waning. A crescent Moon is mostly dark, and a gibbous moon is mostly light. As the moon orbits Earth, it spins on its own axis so the same half (the near side) always faces Earth- we never see the far side of the moon.
   • Everything spinning has an outward force.

4. The Heating Effect of the Sun

   • CLIMATE
     • A particular area's climate is affected by its latitude (distance North or South of the equator)- this is due to the earth's curved surface because that means that the sun's rays hit different areas of the earth at differing angles. Regions on or near the equator receive a consistently hotter climate than the rest of the world because the sun's rays beat down on them more directly and at a higher concentration than regions on either side of the equator towards the North and South poles.

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