Page 9 - Curriculum Visions Dynamic Book

As the Earth and Moon move around the Sun, the angle of illumination changes by about 1 degree per day. The effect of this on the phases of the Moon (see pages 12–13) is to cause the time from one full Moon to the next to be 29.531 days (29 days, 12 hours, 44 minutes, and 3 seconds). This is called the synodic month.
As scientists studied the movement of the Moon,
they were able to make predictions about its path and effects. Giovanni Cassini (1625–1712) discovered that the Moon’s axis changes slowly over time, forming its own circular path. This change causes the Moon’s phases. It also accounts for eclipses (see pages 14–15).
Johannes Kepler (1571–1630) developed a series of laws for the movement of planetary bodies, predicting that the Moon changes speed as it makes its eccentric orbit. That is what allows us to see nearly 60% of the Moon’s surface (although not all at the same time).
apogee The point on an orbit where the orbiting object is at its farthest from the object it is orbiting.
axis (pl. axes) The line around which a body spins.
center of gravity The point at which all of the mass of an object can be balanced.
eccentric A noncircular, or oval, orbit.
gravity/gravitational pUll The force of attraction between bodies. The larger an object, the more its gravitational pull on other objects.
momentUm The mass of an object multiplied by its velocity.
orbit The path followed by one object as it tracks around another.
perigee The point on an orbit where the orbiting object is as close as it ever comes to the object it is orbiting.
plane A flat surface.
sidereal month The average time that the Moon takes to return to the same position against the background of stars.
sUn The star that the planets of the Solar System revolve around.
synodic month The complete cycle of phases of the Moon as seen from Earth. It is 29.531 solar days (29 days, 12 hours, 44 minutes, 3 seconds).
tide Any kind of regular, or cyclic, change that occurs due to the effect of the gravity of one body on another.
 This simple tidal sequence shows how the passage of the Moon causes the movement of the tides. In turn, the tides act as a frictional brake on the rotation of the Earth, causing the Earth and Moon to move apart slowly.
In practice, such things as the complicated shape of the ocean basins cause the high and low tides to sweep around the edge of the ocean basins.
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