Earth and the Sun
Earth Science 2013
Astronomy
• Definition: The study of the
planets,[------ moon, stars, and
other objects in space
Sun
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The Sun is the center of our Solar System
There are 8 planets in our solar system
We are 92 million miles from the Sun
The Sun is responsible for all the energy we
receive on Earth
Earth
• The planet we live on
• Only Planet with life(that we know of…)
• Third planet from the Sun
Earth
• The Earth is an inner planet
– Small in size
– Few or no moons(only one)
– No rings
Earth’s Movements
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Rotation: One spin on its axis
Takes about 24 hours to rotate once
This rotation causes DAY and NIGHT
Sun always rises in the EAST and sets in the
WEST
Earth’s Movements
• Revolution (orbit): One lap around the Sun
• This takes about 365 days or one year to
complete
• The path is not quite a circle; its more of an
oval shape
Calendars
• Calendars mark time on earth in 24 hour days
and 365 days per year
• The Egyptian astronomers counted the days
between the appearance of the star Sirius and
found an average of 365 days between
appearances.
• So the Egyptians came up with one of the first
Calendars!
Leap Years
• The path of the Earth around the Sun actually
takes 365 ¼ day to complete.
• Every fourth year we add up the extra time
¼ + ¼ + ¼ + ¼ = one extra day
• This day is added to the calendar every 4 years
on February 29
• Leap Years: 2004, 2008, 2012, 2016, 2020,
2024, 2028, etc
Earth’s Tilt
• Earth has seasons because the axis is tilted as
it moves around the Sun
• WE ARE IN THE NORTHERN HEMISPHERE
• When the Northern Hemisphere is tilted
towards the Sun, we get the most sunlight =
summer
• When the Northern hemisphere is tilted away
from the Sun, we get the least sunlight =
winter
Seasons
Seasons
• Most places on Earth have 4 distinct seasons:
Winter, Spring, Summer, and Fall
• The length of each season depends on its
location on the Earth and how the sunlight
hits the Earth
• The uneven heating of the Earth creates
three different climates: tropical, temperate,
and polar
Season’s interactive
• Click here
Four Seasons
• Winter Solstice
– Starts around December 21
– Northern Hemisphere is tilted away from the Sun
– The rays from the Sun are the weakest
– Shortest day of the year in Northern Hemisphere;
longest day of the year in the Southern
Hemisphere
– Marks the beginning of winter
Four Seasons
Four Seasons
• Autumnal Equinox
– Starts around September 22
– The Suns is directly over the equator creating an
equal amount of daytime and nighttime
– Marks the beginning of Fall
Four Seasons
• Spring Equinox
– Starts around March 21
– The Suns is directly over the equator creating an
equal amount of daytime and nighttime
– Marks the beginning of summer
Four Seasons
Four Seasons
• Summer Solstice
– Starts around June 21
– Northern Hemisphere is tilted towards the
Sun
– The rays from the Sun are the strongest
– Longest day of the year in Northern
Hemisphere; shortest day of the year in the
Southern Hemisphere
– Marks the beginning of the summer
Climate Zones
The Moon
• The Moon takes 27.3 days
to revolve around the
Earth
• The Moon takes 27.3 days
to rotate on its axis
• Therefore, we only ever
see one side of the moon
Lunar Landing Sites