Transcript Earth Sun and Moon

Earth and Moon
Chapter 19
PS 1, PS7 (S.8.7.1, S.8.7.2, S.8.7.3)
ESSENTIAL QUESTIONS
WHAT IS THE EARTH’S
POSITION IN SPACE RELATIVE
TO THE SUN AND MOON?
HOW DOES THIS
POSITIONING AFFECT
VARIOUS PHENOMENA?
EARTH FACTS
 The Earth is an oblate spheroid.
 Eratosthenes was the Greek astronomer who
computed the circumference of the Earth by
assuming that it was a perfect sphere. How did he
do this? Was he very accurate?
 The diameter at the equator is40,075.16 km and
40,008 km from pole to pole. What causes this
variation?
 The distance from the Earth to the Sun is
150,000,000 km (1 Astronomical Unit or AU)
The Earth-Sun System
 It takes one year or 365.25 days for the
Earth to revolve once around the Sun
 It takes the Earth 23 hours and 56 minutes
to rotate once on its axis
 The Earth’s rotation causes day and night
 The side of the Earth facing the Sun gets
light (daytime), the side that faces away
from the Sun is without light (nighttime).
The Seasons
 Seasons are caused
by the tilt (angle) of the
Earth, and the path it
takes around the sun
 It is warmer near the
equator because
sunlight hits the
Earth’s surface more
directly than at higher
latitudes
Earth’s Tilt & Revolution
 Seasons are caused mainly by the 23.5 degree tilt of the
Earth’s axis.
 This tilt causes the number of daylight hours to change
depending on the time of year.
 During winter, there are fewer daylight hours in in the
Northern Hemisphere because it is tilted away from the
sun.
 During summer, there are more daylight hours because the
Northern Hemisphere it tilted toward the Sun.
 The path of REVOLUTION is elliptical. The point at which
the Earth is closest is called its perihelion. The point at
which it is farthest away is called its aphelion. The distance
from the sun does not determine seasonal change. It is the
way the Earth revolves around the sun that affects the
angle of the Earth to the Sun which in turn causes the
seasonal variation.
The season’s yearly cycle
 An Equinox occurs when the Sun is directly above
the equator and both hemispheres receive the
same amount of sunlight. This happens in March
and September (Vernal and Autumnal). First day
of?
 A Solstice is the time when the sun is the farthest
north or south from the Equator.
 During the Summer Solstice, the Northern
Hemisphere is tilted toward the sun and receives
more warmth and daylight. The Summer Solstice
occurs in June and is the longest day of the year.
First day of?
 During Winter Solstice, the Northern Hemisphere
is tilted away from the sun and receives less
warmth and daylight. The Winter Solstice occurs in
December and is the shortest day of the year. First
HELPFUL WEBSITES
WWW.NASA.GOV
Earth/Moon System
 Lunar Cycles (phases)
 Eclipses
 Tides
Lunar Cycles
 Waxing- the sunlit part of the moon gets larger
 Waning- the sunlit part of the moon gets smaller
Eclipses
 An eclipse happens when
the shadow of one
celestial body falls on
another body. An eclipse
can only occur at a new or
full Moon and only when
the Sun, Moon, and Earth
are at certain orbital
positions during what is
called an eclipse season.
Eclipse seasons occur
every 173 days ( about 2X
a calendar year) and last
for 30-40 days. Each
season has two eclipses –
solar and then, about two
weeks later a lunar.
 A Lunar eclipse happens
when the Earth comes
between the sun and the
moon.
 A Solar eclipse happens
when the moon comes
between the Earth and the
Sun. Annular eclipses
happen when the moon
does not cover the sun
completely and a “ring of
fire” encircles the moon.
The Moon and the Tides
 On the side of Earth that faces
the moon the ocean’s surface
bulges because of the moon’s
gravity pull on the water.
 On the opposite side of the
Earth, the water bulges
because of the rotation of the
Earth and the revolution of the
moon around the Earth.
The Sun and the tides
 The Sun’s gravity also pulls on the Earth
and affects the tides, however since the Sun
is much farther away than the moon, its
affect is about half that of the moon.
 Tidal Range- the difference between levels
of ocean water at high tide and low tide.
Moon’s phases and the tide
 Spring Tides- Occur when the Sun, Earth,
and Moon are in line. The Sun’s added
gravitational force cause the greatest tidal
range between high tide and low tide.
 Neap Tides- Occur when the Sun, Earth and
Moon form a 90 degree angle. These tides
have the smallest range, because the
gravity of the Sun and Moon are working in
different directions. Why Tides?
WORKS CITED
http://www.sfgate.com/getoutside/
1996/jun/tides.html
WWW.NASA.GOV
WWW.UCAR.EDU