Properties of the Earth
How do we know the earth is round? In 350BC Aristotle observed the Earth cast a curved shadow on the Moon during an eclipse. Early sailors, noticed that approaching ships came into view a little at a time. Sailors also noticed how the sky looked and saw that the North Star moved higher or lower in the sky.
- Imaginary vertical line around which the Earth spins. It is tilted 23.5 o from the line drawn to the plan of its orbit. Rotation= the spinning of earth which causes day and night. One complete rotation takes about 24hrs or one day
As earth rotates, you can see the sun come into view at daybreak. Earth continues to spins, making it seem as if the sun moves across the sky until it sets at night. During night, your area of earth has rotated so that it is on the opposite side of the sun.
The earth has a magnetic field of north and south. Unfortunately the magnetic field is inclined at an angle of 11.5 o. The field is also position in the opposite direction of the named poles (ex. South magnetic field is located at the north pole).
Revolution= Earth’s yearly orbit around the sun Ellipse- elongated, closed curve (ex. earth’s orbit) Earth is closest to the sun => January 3 Earth is farthest to the sun=> July 4
Solstice: the day when the sun reaches its greatest distance north or south of the equator Equinox: occurs when the sun is directly above earth’s equator
Moon’s rotation Takes 27.3 days to revolve around the earth and complete 1 rotation.
Different forms that the moon takes in its appearance from Earth. How does this happen? It’s surface reflects the sun, as the moon revolves around earth, you see different portions of its lighted side, causing the moon’s appearance to change.
NEW MOON: when the moon is between the Earth and the Sun FULL MOON: when all the moon’s surface facing the Earth reflects light. Waxing Phases 1. Waxing crescent- the right quarter of the moon is visible (24hrs after the new moon) 2. First quarter- half of the right side of the moon is visible 3. Waxing Gibbous- ¾ of the right side of the moon is visible 4. Full Moon- when all the moon is visible
Waning Phases 1. Waning Gibbous- ¾ of the left side of the moon is visible 2. Third quarter (half moon)- half of the left side of the moon is visible 3. Waning crescent- the left quarter of the moon is visible Lunar Cycle- takes about 29.5 days
SUN
-When the earth or the moon temporarily blocks the sunlight from reaching the other Total solar eclipse- when the moon is directly between the sun and earth and casts its shadow over part of earth.
Umbra- area of total solar eclipse Penumbra- lighter shadow on Earth’s surface (partial solar eclipse)(DO NOT STARE AT THE SUN DUE TO INCREASE REFLECTION FROM THE MOON MAY DAMAGE YOUR EYE SIGHT)
-The rise and fall of sea level. What causes tides? They are NOT created by wind, but by the gravitational attraction of Earth and the Moon & the Earth and the Sun.