Unit VII Tides, Eclipses, Seasons
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32 terms
Terms | Definitions |
|---|---|
 Autumn Equinox | When the tilt of the Earth's axis is inclined neither away from nor towards the Sun, the Sun being vertically above a point on the Equator. The term equinox can also be used in a broader sense, meaning the date when such a passage happens. |
| Spring Equinox | The first day of the Season of Spring - and the beginning of a long period of sunlight at the Pole. The term equinox can also be used in a broader sense, meaning the date when such a passage happens |
| Axis of rotation | A rotation is a movement of an object in a circular motion. A two-dimensional object rotates around a center (or point) of rotation. A three-dimensional object rotates around a line called an axis. Axis: the center around which something rotates |
| Rotation | a transformation in which the coordinate axes are rotated by a fixed angle about the origin. OR the act of rotating as if on an axis OR a single complete turn (axial or orbital) |
| Revolution | Earth's yearlong elliptical orbit around the sun or the movement of an object around another object. |
| Solar Noon | •In the northern hemisphere north of the tropic of cancer, solar noon occurs when the position of the sun is geographic south. The sun is at its highest altitude in the sky at solar noon |
| Solar Time | The local time based on a solar day - the mean time between successive noons. Solar time is time kept or measured by the sun; and its basic division, the day, has been recognized and used since the dawn of history. |
| Daylight Savings Time | time during which clocks are set one hour ahead of local standard time; widely adopted during summer to provide extra daylight in the evenings |
| International Date Line | An imaginary line on the Earth's surface at 180° longitude, mostly through the Pacific Ocean, to the east of which the calendar date is one day earlier than to the west |
| Prime Meridian | Meridian at zero degree longitude from which east and west are reckoned (usually the Greenwich longitude in England) |
| Parellelism of the axis | Refers to the fact that the axis of the earth remains parallel to it's previous position as the earth revolves around the sun. This means that the earth's axis always points in the same direction. |
| Standard Time Zones | 15 degree areas of longitude equal to one hour and designated as a number of hours either earlier or later than Greenwich Mean Time. |
| Summer Solstice | The Summer Solstice occurs exactly when the earth's axial tilt is closest to the sun at its maximum of 23° 26' |
| Time Meridian | A line of longitude exactly divisible by 15 degrees on which each standard time zone is roughly centered. |
| Winter Solstice | The Winter Solstice occurs exactly when the Earth's axial tilt is farthest away from the sun at its maximum of 23° 26'. |
| Zenith | The direction pointing directly "above" a particular location; that is, it is one of two vertical directions at the location, orthogonal to a horizontal flat surface there. |
| Apogee | The point in an orbit around the Earth that is most distant from the Earth. The point in an orbit that is most distant from the center; The highest point |
| Aphelion | Apoapsis in solar orbit; the point in the orbit of a planet or comet that is at the greatest distance from the sun |
| Perigee | Periapsis in Earth orbit; the point in its orbit where a satellite is nearest to the Earth. |
| Perihelion | The point in an orbit where the body is at the minimum distance from the Sun. |
| Lunar Eclipse | Occurs when the moon passes behind the earth such that the earth blocks the sun's rays from striking the moon. This can occur only when the Sun, Earth and Moon are aligned exactly, or very closely so, with the Earth in the middle. |
| Solar Eclipse | Occurs when the Moon passes between the Sun and the Earth, and the Moon fully or partially covers the Sun as viewed from some location on Earth. This can only happen during a new moon, when the Sun and Moon are in conjunction as seen from Earth. |
| Annular Eclipse | Occurs when the sun is directly behind the moon but a ring of sunlight can be seen around the blackened moon. |
| Partial Eclipse | An eclipse in which the eclipsed body is only partially obscured. |
| Neap Tide | A less than average tide occurring at the first and third quarters of the moon. |
| Spring Tide | Tide that has a large change between low and high tide. It occurs at new and full phase, when the Moon's tidal effect is aligned with the Sun's tidal effect. |
| Penumbra | A fringe region of partial shadow around an umbra. The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast. |
| Umbra | A region of complete shadow resulting from total obstruction of light. The umbra, penumbra and antumbra are the names given to three distinct parts of a shadow, created by any light source. For a point source only the umbra is cast. |
| Waning | Part of the lunar cycle in which the Moon is getting less full and the "left side is lit up" OR A gradual decrease in magnitude or extent |
| Waxing | A gradual increase in magnitude or extent pertaining to the Lunar Cycle. Opposite of Waning. |
| Tides | Tides are the rise and fall of sea levels caused by the combined effects of the rotation of the Earth and the gravitational forces exerted by the Moon and the Sun. The tides occur with a period of approximately 12 and a half hours and are influenced by the shape of the near-shore bottom. |
| Tidal Range | The tidal range is the vertical difference between the high tide and the succeeding low tide. It is the difference in height between high and low water and will vary throughout the tidal cycle. |
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