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Unit 4
An Exploration of the Earth-Sun-Moon Relationship
| Question | Answer |
|---|---|
| axis | the imaginary line that passes through Earth's center and the North and South poles |
| rotation | the spinning of Earth on its axis; causes day/night pattern |
| 24 hours (23 hrs & 56 min) | the actual amount of time it takes for Earth to complete one full rotation on its axis, causing day and night |
| revolution | the movement of one object around another, as in Earth around the Sun; one of the causes of Earth’s seasons |
| orbit | the path of an object as it revolves around another object in space. |
| 365.25 days | the actual amount of time it takes for Earth to complete one full orbit around the Sun, which is why we add a leap day every four years to keep our calendar in sync. |
| leap year | years with an extra day (February 29) added to the calendar to make up for the extra 0.25 day in Earth’s orbit around the Sun. |
| equator | an imaginary circle around the middle of the earth, halfway between the North Pole and the South Pole |
| equinox | the two days of the year on which hemisphere is tilted neither toward or away from the sun; marks the beginning of spring and fall; latin for "equal nights" |
| gravity | the force that pulls objects toward each other |
| solstice | the two days of the year on which the sun reaches its greatest distance north or south of the equator; marks the beginning of winter and summer |
| Northern hemisphere | the half of the Earth that lies north of the equator |
| Southern hemisphere | the half of the earth that is south of the equator |
| counterclockwise | the direction in which the Earth rotates on its axis causing the Sun to rise in the East and set in the west; Earth also revolves around the Sun in this direction |
| time zones | created zones dividing Earth into 24 regions about 15 degrees of longitude apart, with each zone representing one hour of Earth’s rotation to help keep time consistent around the world. |
| 23.5° | the angle at which Earth’s axis is tilted as it orbits the Sun, causing the seasons by changing how direct sunlight hits different parts of the planet throughout the year. |
| perihelion | the point in Earth’s orbit when it is closest to the Sun (for the Northern hemisphere this occurs in January); the prefix peri- means “near” and helion refers to the “Sun” |
| aphelion | the point in Earth’s orbit when it is farthest from the Sun (for the Northern hemisphere this occurs in July); the prefix ap- means “away from” and helion refers to the “Sun” |
| highlands | light-colored and bright, mountainous areas on the Moon |
| maria | the dark, flat plains on the Moon’s surface formed by ancient lava flows |
| craters | round imprints on the Moon’s surface (or other planets and moons) formed when meteoroids, asteroids, or comets collide with it at high speeds |
| Moon phases; lunar cycle | the different phases we see from Earth because as the moon revolves around the earth and the illuminated portion that we see changes. |
| 29.5 days | the amount of time it takes the Moon to complete one full cycle of phases as it orbits Earth. |
| dark side/far side of the Moon | the side of the Moon that is NOT seen from earth due to its synchronous rotation |
| synchronous rotation | when the Moon rotates on its axis at about the same rate that it revolves around Earth, so we always see the same side of the Moon (the “near side”) while the other side is called the “far side.” |
| waxing | when the visible, illuminated part of the Moon is “growing larger”, and the right side of the moon is illuminated |
| waning | when the visible, illuminated part of the Moon is “shrinking”, and the left side of the moon is illuminated |
| new moon | the first phase of the lunar cycle when the Moon’s dark, unlit side faces Earth, it lasts only one night, and the Moon is positioned between the Sun and Earth. |
| waxing crescent | the Moon phase that occurs after a new moon when a small, curved sliver of the Moon is visible and growing larger each night, with the right side illuminated. |
| first quarter | the phase when the right half of the Moon’s surface is illuminated and the illuminated portion we see continues to grow |
| waxing gibbous | the Moon phase when more than half of the Moon is illuminated and growing toward a full moon, with the right side mostly lit. |
| full moon | the phase when the Earth is located in between the Sun and Moon and the entire face of the Moon that faces Earth is fully illuminated by the Sun. |
| waning gibbous | the Moon phase after a full moon when most of the Moon is still lit, but the illuminated portion is slowly decreasing, with the left side illuminated. |
| third quarter | the phase when half of the Moon is illuminated on the left side and the Moon continues to wane. |
| waning crescent | the Moon phase when only a small, curved sliver of the Moon is illuminated on the left side, and the visible light is shrinking as it moves toward a new moon. |
| blue Moon | a rare event when a second full moon occurs in the same calendar month |
| eclipse | when one celestial body passes in front of another, blocking its light |
| lunar eclipse | when the Earth comes between the Sun and the Moon, casting a shadow on the Moon |
| solar eclipse | when the Moon comes between the Sun and Earth, blocking the Sun’s light either partially or completely |
| umbra | the darkest part of a shadow. During an eclipse, only the people in this part of the shadow experience a full eclipse |
| penumbra | the lighter shadow surrounding the darkest part. During a solar eclipse, people in the penumbra see only a partial eclipse |
Created by:
gibbonsUMS