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Earth-Sun Relationships. Earth’s Orientation. • Revolution – seasonal changes occur because Earth’s position relative to the sun continually changes as it travels along its orbit .
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Earth-Sun Relationships Earth’s Orientation • Revolution – seasonal changes occur because Earth’s position relative to the sun continually changes as it travels along its orbit. • Rotation – the length of daylight compared to the length of darkness also is determined by Earth’s position in orbit.
Earth-Sun Relationships • The summer solstice is the solstice that occurs on June 21 or 22 in the Northern Hemisphere and is the “official” first day of summer. • The winter solstice is the solstice that occurs on December 21 or 22 in the Northern Hemisphere and is the “official” first day of winter.
Earth-Sun Relationships • The autumnal equinox is the equinox that occurs on September 22 or 23 in the Northern Hemisphere. • The spring equinox is the equinox that occurs on March 21 or 22 in the Northern Hemisphere.
16.2 Waves and Tides Tides are daily changes in the elevation of the ocean surface. • Tide-Causing Forces • Ocean tides result from the gravitational attraction exerted upon Earth by the moon and, to a lesser extent, by the sun.
16.2 Waves and Tides Tide Cycle • Tidal range is the difference in height between successive high and low tides. • Spring tides are tides that have the greatest tidal range due to the alignment of the Earth–moon–sun system. • Neap tides are tides that have the lowest tidal range, occurring near the times of the first-quarter and third-quarter phases of the moon.
16.2 Waves and Tides • Three main tidal patterns exist worldwide: • Diurnal tidal patterns have one high tide and one low tide per day • Semidiurnal tidal patterns exhibit two high tides and two low tides each day • Mixed tidal patterns are similar to a semidiurnal pattern except it is characterized by a large inequality in high water heights, low water heights, or both
Circumference of Earth • You might be interested to know that the circumference of Earth is different depending on how you measure it. • The circumference around the equator is larger than around the poles • Around the equator = 40,075 km(24,901 mi) • Around the poles = 40,007 km(24,859 mi) • This is because Earth isn’t a perfect sphere; it bulges around the equator because of its rotation