Science flash card

• ccur of the and its the sun.
• es of mand eep Earth un and und of the moon and
• The positions of the sun, the earth, and the moon determine the earth's seasons and moon phases. These positions also influence lunar and solar eclipses, as well as high and low tides.
• Earth and its moon experience two different types of motion as they move through space

  1. Earth spins on its axis once every 24 hours, or one solar day

  2. Moon spins on an axis about once every 29.5 days, or one lunar day

  3. Earth revolves around the sun once every 365.25 days

  4. Moon revolves around Earth counterclockwise approximately every 29.5 days
• Both Earth and its moon follow elliptical paths, or orbits, as they complete their revolutions
• Sun's mass


  330,000 times that of Earth
• The sun is closer to Earth than any other star, and therefore exerts an enormous gravitational pull on the earth, keeping the planet revolving
• Since Earth is massive compared to its moon, the earth's gravitational pull on the moon is greater than the moon's gravitational pull on Earth
• However, compared to natural satellites that orbit other planets, the moon is huge. Its relatively large mass, combined with its nearness to Earth, means that the moon exerts a significant gravitational force on the earth
• Inertia


  Keeps the earth orbiting around the sun and the moon orbiting around the earth
• Newton's first law of motion states that objects at rest will stay at rest and objects in motion will stay in motion unless acted upon by an outside force
• Law of universal gravitation


  Every object in the universe attracts every other object, depending on their masses and distances from one another
• The greater the mass of an object, the greater the gravitational pull of that object. Gravitational pull also increases as the distance between two objects decreases
• Since weight is determined by the force of gravity, an object's weight varies depending on where it is in the universe. The mass of an object is the same wherever it is located
• The GRACE (Gravity Recovery and Climate Experiment) mission is a joint project of the United States and Germany. The goal of this mission is to map variations in Earth's gravity field using two spacecraft
• Solstice


  The two days of the year in which the sun's most direct rays reach farthest north or farthest south
• Equinox


  The two days of the year when day and night are almost the same length everywhere on Earth
• As Earth revolves around the sun, many areas experience four seasons characterized by variable temperatures, weather patterns, and length of daylight. This change of seasons is caused by the tilt of the earth as it rotates on its axis and revolves around the sun
• The people living near the equator do not experience four distinct seasons. Instead, they have alternating wet and dry seasons. Those living near the North and South Poles have short summers and long winters. There the sun provides light for 24 hours each day for most of the summer season, although the sun remains low in the sky. During the polar regions' winter season, it is continually dark for months!
• Neither of Earth's hemispheres is tilted toward the sun during the spring equinox
• During the winter solstice, the Southern Hemisphere is tilted toward the sun
• Around June 22, people in the Northern Hemisphere experience more daylight hours of sunshine than any other time of year. Around December 22 the opposite occurs during the winter solstice, when there are more hours of darkness than daylight. These solstices take place because of the maximum tilt of the Earth's axis toward and then away from the sun
• During the equinox, the sun appears to be directly above the equator and the amounts of daylight and nighttime are almost equal everywhere on Earth
• Crescent


  The moon phase in which less than half of the moon's sunlit side is visible
• Gibbous


  The moon phase in which more than half, but not all, of the moon's sunlit side is visible
• Wax


  To grow
• Wane


  To shrink
• Lunar eclipse


  An event that occurs when Earth passes directly between the sun and the moon, causing Earth's shadow to block the sun's light from the moon
• Solar eclipse


  An event that occurs when the moon passes directly between the sun and Earth, causing the moon's shadow to block the sun's light from a portion of Earth
• When the earth and moon are in line with the sun, they occasionally block sunlight from each other. These events are called eclipses
• A lunar eclipse occurs when Earth blocks the sunlight from the full moon. For this to happen, Earth must be between the sun and the moon
• A solar eclipse occurs when the moon passes directly between the sun and the earth during a new moon phase
• The moon's color and brightness during an eclipse varies because of the amount of light refracted or bent by the earth's atmosphere
• During a total solar eclipse, the moon blocks sunlight from the Earth
• Waxing


  When the near side of the moon is illuminated, it is called a full moon
• Waning


  After a full moon occurs, it appears to shrink as the moon returns to a new moon
• The moon's near side always faces the Earth while most of its far side faces away from Earth
• Eclipses


  When the Earth and moon are in line with the sun, they occasionally block sunlight from each other
• Lunar eclipse


  Occurs when Earth blocks the sunlight from the full moon
• Solar eclipse


  Occurs when the moon passes directly between the sun and the Earth during a new moon phase