3. THE SUN-EARTH-MOON
SYSTEM
The Sun, Earth, and Moon work together daily to create ocean
tides, sunsets, the length of days, seasons, etc.
Earth spins around an imaginary vertical axis that runs from the
North Pole to the South Pole. When an object turns or spins
around a point located at its center this is known as rotation.
- The Earth’s rotation is what causes day and night.
Think About It:
- How long does it take for the Earth to completely rotate
around its axis?
4. ROTATION AND REVOLUTION
As Earth rotates, it also revolves around the sun.
- Revolution is the act of one object spinning in a circular or
elliptical orbit around another object.
Earth completes one full revolution (or one full orbit) around the
sun every 365.25 days.
- Orbit is the path the Earth takes
around the sun
The Earth’s orbit is actually shaped like
an oval (also called an ellipse)
5. SEASONS
Earth is divided into two hemispheres (The North and The South)
by the equator.
- The equator is an imaginary line around the Earth that goes
exactly halfway between the North Pole and the South Pole
and divides it into two equal halves
Earth’s axis is tilted at an angle of 23.44 degrees. That
combined with the
hemispheres is what creates
our seasons
6. SEASONS
When the Northern Hemisphere (Hint: we are in the Northern
Hemisphere) is tilted towards the Sun, we are experiencing
Summer.
When we are tilted away from the Sun, we are experiencing
Winter
Think About It:
- Does the Southern
Hemisphere experience
seasons at the same time
that we do? Why or Why
not?
7. SEASONS
There are distinct days that start each season. The beginning of
the winter and summer seasons are called solstices.
The Summer Solstice is the longest day of the year occurring on
June 21st in the Northern Hemisphere
- There are still only 24 hours in the day, but the sun is up for
over 12 hours
The Winter Solstice is the shortest day of the year occurring on
December 21st in the Northern Hemisphere
- There are still just 24 hours in the day, but the sun is only up
for around 8 to 9 hours of daylight
8. SEASONS
The beginning of the spring and autumn seasons are called
equinoxes.
- An equinox is a day of the year which has equal amounts of
day and night.
The Autumnal Equinox is the start of autumn on September 21
in the Northern Hemisphere
The Vernal Equinox is the start of spring on March 21 in the
Northern Hemisphere
Think About It:
Thinking about the dates given for the Northern Hemisphere,
when are the solstices and equinoxes in the Southern
Hemisphere?
9. LUNAR PHASES
Just like the Earth, the moon is in constant motion. It completes
a revolution around Earth every 28 days.
- The moon also completes a full rotation in 28 days
Think About It:
- Why do we see the same side (the
light side) of the moon? Explain
in your own words.
10. LUNAR PHASES
Throughout the 28 days of the moon's revolution, it will go
through 8 lunar phases.
- Lunar Phases are the changes in appearance of the moon
The Moon reflects sunlight to us on Earth. The Sun always lights
half of the Moon, but because of the change in position
between the Earth and Moon we
see 8 distinct lunar phases
11. LUNAR PHASES
When the moon appears to be growing, the moon phase is
called waxing. When the moon appears to be shrinking, the
moon phase is called waning.
Let’s Practice:
12. ECLIPSES
Eclipses are somewhat rare events that occur when the sun,
moon, and Earth are perfectly aligned.
The two types of eclipses are solar and lunar.
- A solar eclipse is an eclipse that occurs when the moon is
between the sun and Earth
- A lunar eclipse is an eclipse that occurs when Earth’s
shadow covers the moon
Think About It:
- What moon phase would occur during a solar eclipse?
During a lunar eclipse? Give your reasons.
