Download 2nd Grade Discovery Lab

Discovery Lab
Night sky
2nd Grade
Activity: Earth’s Orbit Around the Sun
(GPS S2E2) – Students will relate the length of the day and night to the change in seasons (for example: Days
are longer than the night in the summer.)
Supplies:
 Earth’s Orbit Model
 Light
 Book - The Reasons for the Seasons by Gail Gibbons
Concepts to be learned:
 The tilt and position of the Earth relative to the Sun determines the seasons.
 Understand the expression “the sun rises in the east and Sets in west.”
Background Information
 The seasons are caused by the tilt of the Earth on its “imaginary” axis (23.5°) and the Earth’s orbit around
the sun. The tilt always stays the same and points toward the North Star, Polaris (meaning “Pole Star”).
One Earth rotation on its axis takes about 24 hours (at 1,000 mph), and one Earth revolution around the sun
takes about 365¼ days (at 67,000 mph). Both spins are counterclockwise.

The Earth’s orbit around the sun is elliptical.

The Earth and sun are closest during OUR winter and the Southern Hemisphere’s summer. However, the
summers in the Southern Hemisphere are not hotter than our summers. The Southern Hemisphere is
considered a “water hemisphere” due to having lots more ocean water than the Northern Hemisphere. The
excess water absorbs the extra heat.

The tilt of the Earth determines the season we’re in. We are in the Northern Hemisphere, so if the top of
the Earth’s axis points toward the sun, we are having summer in the Northern Hemisphere.
Conversely, if the top of the Earth’s axis points away from the sun, we are having winter in the
Northern Hemisphere. This is reversed for the Southern Hemisphere.

Fall and spring are transitions between winter and summer. The Earth is neither tilted toward or away
from the sun. There are 4 seasons and they always occur in order: winter, spring, summer, and fall. So, the
only way to tell if we are in spring or fall is to determine which way we’re moving. If we are moving from
winter, heading to summer, then it’s spring. If we are moving from summer, heading to winter, then it’s
fall. We are currently moving from summer, heading to winter, so we (the Northern Hemisphere) are in fall
transition.
Earth’s Tilt and the Seasons

Each child represents the planet Earth. Tell the students that the earth is tilted. Explain briefly what tilted
means and use one of the earth models to demonstrate how the earth is tilted. (Take one of the Earth
models out of the block and show the students how the Earth would look if it were not tilted). Now tell the
students that the top part of their body is the Northern Hemisphere, their waist is the equator, and below
their waist is the Southern Hemisphere. Use a globe to point out the Northern hemisphere, equator and the
Southern Hemisphere. Tell the students that you (the parent volunteer) will represent the sun.

Have the children walk over to the taped “Earth’s Orbit” model in the middle of the room on the floor.
Everyone should cluster together facing the white board while standing on the tree representing winter.
Remind the students that the top half of their body represents the northern hemisphere and the bottom half
of their body represents the southern hemisphere. The first month of the year is January which occurs in
winter. Tell the students that the tilt of the Earth is always pointed towards the North Star. Point to the
North Star on the white board.

A parent or student volunteer stands in the middle of the orbit holding the picture of the sun and facing the
children’s backs. The children will be facing the North Star, with the top half of their bodies tilted away
from “the sun.” Ask which hemisphere is pointed away from the Sun. The correct answer is the Northern
or the top part of the body). Therefore so it must be winter in the northern hemisphere and summer in the
southern hemisphere.

Next, have the students move backwards to the tree representing spring. Everyone should cluster together
facing the white board (the North Star). Again, remind the students that the top half of their body
represents the northern hemisphere and the bottom half of their body represents the southern hemisphere.
Tell the children that the northern hemisphere is now having spring. Point out that they are no longer
completely facing away from the sun, in fact the Northern Hemisphere is getting warmer.

Now, have the students move backwards as the Earth moves into summer. Everyone should be clustered
together and tilted towards the sun (parent volunteer). Tell the students that northern hemisphere is now
experiencing summer because it is tilted towards the sun and the Southern Hemisphere is now experiencing
winter because it’s not tilted towards the sun. (It is actually tilted away from the sun, as they will discover
later.)

Finally, have the students move to the tree representing autumn. Tell the children that the northern
hemisphere is getting cooler because it is no longer tilted directly towards the sun as it was in the summer.
The Earth’s Orbit
Have the students return to their seats to look at the model on the table. The seasons are marked on the blocks
of wood on each earth model. The red star on each ball is in the same location and represents Troup County,
GA. Each Earth model should be pointed in the same direction (toward the North Star). Turn on the light bulb.
Troup County, GA in the Winter:
 Point to the Earth model marked “winter.” The tilt points away from the sun.
 The northern hemisphere is receiving less sunlight, that is why Troup County is experiencing colder
weather and less daylight.
 The Southern Hemisphere is getting 3X as much sunlight as the Northern Hemisphere, so it’s summer
down there.
 The equator is getting 12 hours of daylight and 12 hours of night.



The North Pole is getting zero hours of sunlight (24 hours of darkness).
The South Pole is getting 24 hours of sunlight (zero hours of darkness—“Land of the Midnight Sun”).
The further south you move from the equator, the longer the sunlight exposure you get, so your day is
longer, until you reach 24 hours of daylight at the South Pole.
Troup County, GA in the Spring:
 Point to the Earth model marked “spring.” The Earth is neither tilted toward or away from the sun.
 The Northern Hemisphere is transitioning from winter to summer, so it is spring time for us.
 Every place on Earth has 12 hours of daylight and 12 hours of night.
 The equator is getting 12 hours of daylight and 12 hours of night.
 The days will be getting longer in the Northern Hemisphere since we are headed towards the summer
season.
Troup County, GA in the Summer:
 Point to the Earth model marked “summer”. The tilt points towards the sun.
 The Northern Hemisphere is getting 3X as much sunlight as the Southern Hemisphere, so it’s summer in
Troup County. Point out that the sun ( light bulb) is shining more directly on Troup County.
 The tilt causes the sun to appear higher in the sky during the summer than during the winter. The higher
sun causes more hours of daylight and more intense, direct sunlight, or hotter conditions on the surface of
the Earth.
 The equator is getting 12 hours of daylight and 12 hours of night.
 The North Pole is getting 24 hours of sunlight (zero hours of darkness—“Land of the Midnight Sun”).
 The South Pole is getting zero hours of sunlight (24 hours of darkness)
Troup County, GA in the Fall
 Point to the earth model marked “Fall.” The Earth is neither tilted towards or away from the sun.
 The northern hemisphere is transitioning from summer to sinter, so it is fall (or Autumn) for us.
 Every place on Earth has 12 hours of daylight and 12 hours of night.
 The equator is getting 12 hours of daylight and 12 hours of night.
 The days will be getting shorter in the Northern Hemisphere since we are headed toward winter season.
For reinforcement, remove one of the earth models from the block and show the students that if the
earth was on a vertical axis (Not Tilted) we would not have the seasons.
Activity - Earth’s Orbit Around the Sun
Think about the models at this station. They represent Earth’s path around the sun. Then answer the following
questions:
1. Circle the answer that best describes the movement of the Earth around the Sun.
A. The Earth moves in a square path around the sun.
B. The Earth moves in a circular (but slightly elliptical) path around the sun.
C. The sun revolves around the Earth.
2. Which of the following is the best reason why we have different seasons on the Earth?
A. We have seasons because the Earth is tilted as it revolves around the sun.
B. The Earth is turning very fast and this makes it snow.
C. The Earth is not tilted, so this causes the seasons.
3.
Troup County, Georgia is pointed toward the Earth in the summer and ________________ from the Earth
in the winter.
4. If you are in Australia (the southern hemisphere) and it is winter, what season are they having in America
(the northern hemisphere)? _______________________________
5. How long does it take for the Earth to make one revolution around the sun? (To go around one time)
________________________________________