| A | B |
|---|
| Gravity | the force of attraction between two objects |
| Mass | the amount of matter that makes up an object. |
| Matter | anything that takes up space. It is made of atomic particles |
| Weight | the measure of the gravitational pull on an object |
| Vacuum | the removal of all matter. "In a vacuum" an area with all matter removed. |
| Density | the ratio of the amount of matter in an object compared to its volume. |
| Friction | the resistance between two objects as they rub against one another |
| Pressure | the force applied to an area of a surface. Pressure always works to equal out between two areas. |
| Force | the push or pull on an object |
| Light | electromagnetic waves that travel through space. |
| Sound | vibrations transmitted through a medium |
| Medium | any gas, liquid, or solid used to transmit sound |
| Temperature | the amount of heat or energy an object possesses |
| astronomical unit | name for the measurement of the distance from the earth to the sun |
| Sol | Sun god in Roman mythology |
| Sun | Our special star |
| solar spectrum | the entire span of EM waves emitted by the sun |
| wavelength | the distance from the crest of one wave to the crest of the next wave |
| picometers | how gamma rays are measured |
| nanometers | how visible light wavelengths are measured |
| nuclear fusion | process in which nuclei of hydrogen atoms combine under intense heat and pressure to form the nuclei of helium atoms |
| photosphere | the visible surface of the sun |
| chromospheres | the lowest layer of the sun's atmosphere starting at the photosphere and extending out 2000 km from the sun's surface |
| corona | the hot outer atmosphere of the sun that extends far out into space to become solar wind |
| solar wind | a flow of mostly protons, electrons, and small atomic nuclei from the sun |
| prominence | a stream of solar plasma that rises into the corona from the chromospheres and then gradually falls back |
| sunspots | small dark areas that appear on the sun's surface |
| solar flare | a sudden energetic explosion of the sun's matter that emits bursts of rays and particles |
| moon | the closest astronomical body we can see in the sky |
| satellite | any natural or artificial object that orbits a planet. |
| moon | natural satellite |
| craters | any distinct, roughly circular, walled depression in the earth's surface (or moon) |
| meteoroids and asteroids | flying space rocks |
| crater chain | formed by a comet that broke up into many pieces before impacting |
| maria | circular areas that ancient observers thought were large lakes or seas on the moon's surface |
| rille | a long, narrow valley on the moon's surface |
| capture theory | suggests that the earth's gravity captured a largish planetesimal as it traveled by in a similar orbit or speed. |
| fission theory | says that the moon spun off from the earth as the earth was forming, like mud flinging off a spinning wheel. |
| accretion theory | says that the earth and moon condensed together from the same nebular cloud at the beginning of the solar system |
| giant impact hypothesis | suggests that the young earth experienced a glancing hit by a Mars-sized planet. |
| apparent motions | the result of observing the sun, moon, planets and stars from our location her on a moving, rotating earth |
| revolution | the motion of an astronomical body around another astronomical body that is the center of an orbital system |
| rotation | the spin of an object around an imaginary axis that passes through its center |
| perigee | the moon's point of closest approach |
| apogee | the most distant point of the moon's orbit |
| terminator | the line between the light and dark sides of any astronomical body |
| waxing | the lighted area of the moon grows lighter |
| waning | the lighted area of the moon grows smaller |
| full moon | occurs when the moon is exactly opposite the sun with the earth between |
| sideral year | one full orbit of the earth around the sun |
| calendar year | 365 days |
| Julian year | 365.25 days |
| lunar or synodic month | the time between new moons defines one orbit and is called this |
| sideral month | full orbit of moon around earth in reference to distant stars which takes 27.3 days |
| day | one full rotation of the earth |
| solar day | the time from one local noon to the next, or about 24 hours |
| equinox | occurs when the sun's rays are perpendicular to the earth's Equator |
| solar eclipse | occurs when the moon blocks some of the sun's light from reaching the earth |
| eclipse | happens when one celestial body cuts off the light from the sun to another body |
| solar and lunar | 2 types of eclipses |
| total solar eclipse | occurs when the moon's disk completely covers the sun's disk. |
| umbra | The main shadow of the moon |
| annular eclipse | the ring-shaped portion of the sun's disk shows around the moon |
| lunar eclipse | happens when the earth blocks the sun's light that normally shines on the moon |
| tides | a change in local sea level and height of the crest caused by gravitational pulls of the moon and sun |
| ray | a bright streak that radiates from some craters on the moon's surface |
| ecliptic | the sun's apparent path among the stars as observed from Earth |
| lunar phase | the regular, repeatedly changing appearance of the shape of the lighted face of the moon as seen from Earth |
