Why is it colder in winter even though the Earth is closer to the Sun?
Listing Details
Concepts
seasons; axis of rotation; hemisphere; light; energy; heat; absorption; reflection; sun
Time needed
- 30 minutes
Age
12-14
Setting
Home
Materials Needed
- Light
- Ball
- Marker
- Straw (cut in 2 pieces)
- Dark room
- Plasticine
Doing the activity!
- Try to find an old air-filled ball (basketball-sized or bigger would be best) that you can draw on with a marker.
- Draw a line around the middle representing the equator and stick half the straw on each “pole” using plasticine.
- Put a lamp, preferably with the shade removed, on a table in the middle of an otherwise dark room.
- Using the “Earth” and its tilted axis, try to recreate summer and winter in both hemispheres. What happens on the first day of summer? The first day of winter? What’s so special about the first days of spring and autumn?
What's happening?
Many people might think that the high temperatures in summer are caused by the Earth being closer to the Sun.but if you’re in the northern hemisphere, like Canada, you’re actually farther from the Sun in the summer! Why, then, is July hotter than January?
If you shine a flashlight straight down on a piece of paper, all that light energy will be concentrated in a small spot. The paper absorbs some of the light and converts it to heat, and reflects the rest. However, if the light shines down at an angle, the same amount of energy is spread over a wider area. The area lit by a flashlight on an angle, then, would not be as warm as if the flashlight was shining straight down.
Why does it matter?
We see the same thing happening with the Earth and the
Sun.
In the summer months, the Sun is more directly overhead than in
the winter. This makes the light energy is more intense, which makes
our part of the Earth hotter. In the winter, the Sun’s rays strike our
part of the Earth at a glancing angle, so the energy is spread out over
a larger area, making that part of the Earth not as warm. But how does
the Sun know when to be directly overhead and how does it get there
every year at the same time?
The answer doesn’t involve the Sun moving
at all... it’s because we move around the Sun and that the Earth is
tilted. If we were to look at Earth from space, its axis of rotation
(the imaginary line around which Earth spins) would stay pointed in the
same direction all the time. That causes a change of seasons as the
Earth moves around the Sun. Six months after the northern hemisphere
has its winter, as the Earth travels around the sun, the situation
reverses: the southern hemisphere gets the Sun’s rays at a slant, so
it’s winter there.
