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m&m 2.2
How We Use Astronomy
| Question | Answer |
|---|---|
| Celestial sphere | What appears to be a dome to which stars are attached |
| Horizon | Separates the visible portion of the celestial sphere from the part we can't see |
| Zenith | The point on the celestial sphere directly above an observer |
| Nadir | The point on the celestial sphere directly below an observer |
| Celestial equator | An imaginary line that encircles the heavens midway between the celestial poles |
| Celestial poles | The ends of the earth's axis |
| Day | The most basic unit of time |
| Meridian | An imaginary line that is used to measure the motion of celestial objects |
| Sideral day | One rotation of the earth relative to the stars. Also called sidus in Latin |
| Apparent solar day | Equals the amount of time the sun takes to cross the meridian twice |
| Mean solar day | The average length of the apparent solar day |
| Equation of time | The difference between mean solar time and apparent solar time |
| Standard solar time | When a traveler crosses into another time zone, they must their watch by exactly one hour and have the correct time |
| Ecliptic | The path the sun follows in a year |
| Equinox | Where the sun crosses the celestial equator. Two points |
| Vernal equinox | The point when the sun crosses the celestial equator from south to north |
| Autumnal equinox | The point when the sun crosses the celestial equator from north to south |
| Solstice | A point on the ecliptic midway between the two equinoxes |
| Summer solstice | Halfway between the vernal and autumnal equinoxes, the sun reaches its farthest point of the celestial equator |
| Torrid zone | Extremely hot zones that are bounded on the north by an imaginary circle called the Tropic of Cancer and on the south by the Tropic of Capricorn |
| Frigid zones | Extremely cold zones that are bounded on the north by an imaginary circle called the Arctic Circle and on the south by the Antarctic Circle |
| Seasons | Because of the earth's elliptical orbit these are not equal in terms of days. Length depends on orbit and speed of earth |
| Temperate zones | Located between the frigid and torrid zones which are neither hot nor cold |
| Precession of the equinoxes | The process when the earth's axis traces a slow circle and the equinoxes are gradually shifting along the ecliptic. Takes 26,000 years to complete |
| Month | Comes from Latin word for the period between one new moon and the next, moonth |
| The Gregorian calendar | The system we now use because the original calendar we used was several days off |
| Pope Gregory XIII | Issued a proclamation in 1582 which established a new calendar |
| Year | The time it takes for the earth to revolve around the sun |
| Anno Domini | Latin for "in the year of our Lord" |
| Week | Instituted by god at the end of creation when He rested on the 7th day of creation and ordained it as a day of rest |
| Other calendars | All of these calculate moon phases and have different year lengths |
Created by:
Jer Stephens
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