earth, moon, and sun

Download Earth, Moon, and Sun

Post on 21-Mar-2016




0 download

Embed Size (px)


Earth, Moon, and Sun. Earth, Moon, and Sun. Astronomy. The study of the moon, starts, and other objects in space. The ancient Egyptians were among the first people to study the stars. They watched the sky to predict floods, and to be prepared to plow and plant their fields. How Earth Moves. - PowerPoint PPT Presentation


Earth, Moon, and Sun

Earth, Moon, and SunEarth, Moon, and SunAstronomyThe study of the moon, starts, and other objects in space.The ancient Egyptians were among the first people to study the stars. They watched the sky to predict floods, and to be prepared to plow and plant their fieldsHow Earth MovesEarth moves through space in two major ways: rotation and revolution.The sun and moon seem to move across the sky each day because Earth is rotating on its own axis.RotationThe imaginary line that passes through the Earths center and the North and South poles is Earths axis.The spinning of Earth on its axis is called rotationThis causes day and night. As Earth rotates, the part of it facing the sun experiences day, and the part of it on the opposite side experiences night.It takes Earth about 24 hours to rotate once, hence one day being 24 hours long.RevolutionIn addition to rotating on its axis, Earth also travels around the sun.Revolution is the movement of one object around another. One complete revolution of the Earth around the sun is called one year.Earths orbit, or path, is not quite circular, its an ellipse.The Seasons of EarthMost places on Earth (besides the poles and tropics) have 4 seasons: winter, spring, summer, and autumn. The temperatures differ from place to place, though. Sunlight hits the Earths surface most directly at the Equator, which is why its warmest there.Sunlight hits the poles at a steeper angle, causing it to spread out over a greater area, which is why the poles are cooler.Earths Tilted Axis and SeasonsEarth has seasons because its axis is tilted as it revolves around the sun.Otherwise, temperatures would remain the same all year long.Earths axis is always tilted at an angle of 23.5 from vertical.As it rotates, the North pole faces the sun for part of the year, and away from the sun for part.Distance from the sun does not cause seasons.

Earth in JuneNorth end of axis is tilted toward the sunIn the Northern Hemisphere, there are more hours of daylight than darkness.It is summer because of direct sunlight and more hours of it, which heats the Earths surface more than any other time.Earth in DecemberPeople in the Southern Hemisphere receive the most direct sunlight.Suns rays in the Northern Hemisphere are more slanted and there are fewer hours of sunlight. It is winter.SolsticesThe days when the sun is farthest north or south of the equator.Summer solstice for us is when the sun is farthest north of the equator, around June 21st. Longest day of the year for our hemisphere.Winter solstice for us is when the sun is farthest south of the equator, around December 21st.Shortest day of the year for our hemisphere.EquinoxesTwice a year when day and night are each 12 hours long (light and dark) everywhere on Earth. Equinox means equal night. Vernal (spring) Equinox around March 21st, marks the beginning of spring in the northern hemisphereAutumnal Equinox around September 22nd, marks the beginning of fall in the northern hemisphereGravity and MotionIn 1666, when an apple fell from a tree, Isaac Newton first thought about the moons orbit and theorized that there must be a force between the Earth and moon to keep the moon in orbit.GravityForce a push or a pullMost everyday forces require objects to be in contact. Gravity is different.Gravity a force that attracts all objects toward each other.Law of Universal Gravitation Newtons law which states that every object in the universe attracts every other object.The strength of the force of gravity between two objects depends on two factors: the masses of the objects and the distance between them.Gravity, Mass, and WeightWhy dont you feel objects pulling you?Mass the amount of matter in an objectdoes not changeWeight the force of gravity on an objectcan change depending on its locationOn the moon, you would weight about 1/6 of your weight on Earth. This is because the moon is much less massive than Earth, therefore the moons gravity on you is far less than that of Earths gravity.Gravity and DistanceThe strength of gravity is affected by the distance between two objects as well as their masses.The force of gravity decreases rapidly as distance increases.If the distance between two objects were doubled, the force of gravity between them would decrease to of its original value.Inertia and Orbital MotionInertia the tendency of an object to resist a change in motion.The more mass an object has, the greater its inertia.An object with greater inertia is more difficult to start or stop.Newtons First Law of Motion an object at rest will stay at rest and an object in motion will stay in motion with a constant speed and direction unless acted upon by a force.Orbital MotionNewton concluded that two factors inertia and gravity combine to keep Earth in orbit around the sun and the moon in orbit around Earth.17Motions of the MoonThe near side of the moon always faces the Earth, the far side always faces away.As the moon revolves around Earth, the relative positions of the moon, Earth, and sun change. The changing relative positions of the moon, Earth, and sun cause the phases of the moon, eclipses, and tides.Phases of the MoonThe moon does not produce light it reflects light from the sun. This is why we can see it.The different shapes of the moon you see from Earth are called phases.The moon goes through its whole set of phases each time it makes a complete revolution around Earth.Phases are caused by changes in the relative positions of the moon, Earth, and sun.*the half of the moon that faces Earth is not always the half that is sunlit*Phases of the Moon, contd.The phase of the moon you see depends on how much of the sunlit side of the moon faces Earth.About 29.5 days after the last new moon, the cycle is complete, and a new moon occurs again.

EclipsesWhen the moons shadow hits Earth or Earths shadow hits the moon, an eclipse occurs.Most months, this does not happen!Eclipse occurs when an object in space comes between the sun and a third object, casting a shadow on that objectSolar EclipsesSolar Eclipse occurs when the moon passes directly between Earth and the sun, blocking sunlight from Earth. A new moon blocks our view of the sun

Total Solar EclipseUmbra the very darkest part of the moons shadow, which is cone-shaped.From any point in the umbra, light from the sun is completely blocked by the moon.The point of the umbra reaches only a small part of Earths surface. People within the umbra experience a total solar eclipse.For a short time, the sky turns dark and eerie as night even in the middle of a clear day and the air cools. You can see the stars and the solar corona, the faint outer atmosphere of the sun.Partial Solar EclipsePenumbra another shadow cast by the moon that is less dark than the umbra, and much larger. In the penumbra, part of the sun is visible from Earth.In a solar eclipse, people in the penumbra see only a partial eclipse. An extremely bright part of the sun remains visible, making it dangerous to look at. EclipsesLunar Eclipse occurs at a full moon when Earth is directly between the moon and sun. Earth blocks sunlight from reading the moon.Total Lunar EclipseLike the moons shadow in a solar eclipse, the Earth also has an umbra and penumbra.When the moon is in Earths umbra, you see a total lunar eclipse.Can be seen anywhere on Earth that the moon is visible.The edge of Earths shadow is visible before and after a lunar eclipse.Partial Lunar EclipseOccurs when the moon passes partly into the umbra of Earths shadow.The edge of the umbra appears blurry, and you can watch it pass across the moon for 2 or 3 hours.TidesTides the rise and fall of ocean water that occurs every 12.5 hours or so.Water rises for about six hours, then falls for about six hours, in a regular cycle.The force of gravity pulls the moon and Earth (including the water on Earths surface) toward each other.Tides are caused mainly by differences in how much the moons gravity pulls on different parts of Earth.The Tide CycleThe moons gravity causes high tide on the side closest to the moonThe moons gravity pulls on Earth more strongly than it does on the water on Earths opposite side, therefore causing high tide on the opposite side of Earth, as well.Between the areas of high tides, water flows away, causing low tides.*see Tides handout, its more clear there!*Spring TidesThe gravity of the sun and the moon pull in the same direction. Their combined forces produce a tide with the greatest difference between consecutive low and high tides, called a spring tide.Spring TidesThe suns gravity also pulls on the Earths waters. During a new moon, the Earth, moon, and sun are nearly in line.The gravities of the sun and moon pull in the same direction, producing the highest difference between high and low tides, called a spring tide.Occurs twice per month, at a new and full moon.Neap TideDuring the moons first-quarter and third-quarter phases, the sun and moon are at right angles (90) to Earth.The sun and moon pull at right angles, causing a neap tide, which has the least difference between high and low tides. These occur twice per month. Earths MoonUntil 1609, no one knew anything about the moon. They could see the shapes on it, but couldnt explain them.Telescope - a device build to observe distant objects by making