earthglobe.app

Day and night & the seasons: a globe lesson

Almost every class has a student who is sure that summer happens because the Earth is closer to the Sun. It is a sensible guess, and it is wrong. This lesson uses a globe that shows the real line between day and night to explain two things: why we have day and night, and why we have seasons.

Suggested age: 7–11 for day and night (Part 1), 10–14 for the seasons (Part 2) · Time: about 40 minutes for both parts · Links: all lessons · for schools

Learning goals

By the end of the lesson students can:

  1. Explain that day and night happen because the Earth spins on its axis.
  2. Point to the line between day and night on a globe and say which places are in daylight.
  3. Explain that the Earth's axis is tilted by about 23.4 degrees.
  4. Explain that the seasons come from that tilt, not from the Earth's distance to the Sun.

What you need

Part 1: Day and night (15 minutes)

  1. Ask first. "Why does it get dark at night?" Collect answers. Common ideas are "the Sun goes down" or "the Sun goes around the Earth".
  2. Show the real line. Open the globe in Satellite mode. The bright half faces the Sun and the dark half faces away. The line between them is worked out from the current time, so it shows where the Sun is shining right now.
  3. Find home. Type your town into the search box and press Go. Is it in daylight? Near the line, it is sunrise or sunset.
  4. Spin the Earth. Let a student drag the globe slowly from left to right, with north at the top. Explain that the real Earth turns this way once in about 24 hours. Places on the dark side turn into the light: that is sunrise. Places turn out of the light: that is sunset.
  5. Check the idea. Ask: "If the Earth stopped spinning, what would happen to day and night?" (One side would have endless day and the other endless night.)

Part 2: The seasons (20 minutes)

  1. Look at the poles. Turn the globe so you look down towards the North Pole, then towards the South Pole. Is the area around each pole lit, dark, or split? Write down today's date next to the answer.
  2. Explain the tilt. The Earth's axis, the line it spins around, is tilted about 23.4 degrees. As the Earth travels around the Sun over a year, the axis keeps pointing the same way in space. For part of the year the north end leans towards the Sun; six months later the south end does.
  3. Connect tilt to summer. When your half of the Earth leans towards the Sun, the Sun climbs higher in the sky, its light hits the ground more directly, and days are longer. That is summer. When your half leans away, the light comes in at a low angle and days are shorter. That is winter.
  4. Bust the myth. Tell students that the Earth is actually closest to the Sun in early January and farthest in early July. If distance caused the seasons, the whole world would have summer in January. Instead, the Northern Hemisphere has winter then, and the Southern Hemisphere has summer.
  5. Opposite seasons. Search for a city in the other hemisphere (for example Buenos Aires if you are in the north, or London if you are in the south). Ask: "What season is it there today?"

Optional hands-on model (5–10 minutes)

Darken the room and use a lamp as the Sun. A student holds a ball tilted to one side and walks slowly around the lamp, keeping the tilt pointing at the same wall the whole time. The class watches which half of the ball gets the most direct light at each side of the lamp. Then go back to the globe and compare.

Questions for students

  1. What causes day and night?
  2. How long does the Earth take to turn once?
  3. By how many degrees is the Earth's axis tilted?
  4. Is the Earth closer to the Sun in January or in July? What does that tell us about the cause of the seasons?
  5. When it is summer in the Northern Hemisphere, what season is it in the Southern Hemisphere? Why?
  6. Look at the area around the North Pole on the globe today. Is it lit, dark, or split? Use the tilt to explain what you see.

Answer key (for the teacher)

  1. The Earth spins on its axis. The half facing the Sun has day; the half facing away has night.
  2. About 24 hours (NASA gives one rotation as 23.9 hours).
  3. About 23.4 degrees.
  4. Closer in January, farther in July. Because the Northern Hemisphere has winter in January, distance cannot be the main cause. The tilt is.
  5. Winter. The two halves of the Earth lean towards the Sun at opposite times of year.
  6. It depends on the date. Around the December solstice (about 21 December) the area around the North Pole stays dark all day, because the north end leans away from the Sun. Around the June solstice (about 21 June) it stays lit all day. Near the equinoxes (about 20 March and 23 September) the line between day and night runs close to both poles, and day and night are about 12 hours each almost everywhere.

Optional extension

A two-date diary. Students take a screenshot of the globe (or sketch it) today, then again a few weeks later at the same clock time. What changed at the poles? Older students can link this to the Arctic Circle: inside it, there is at least one day a year when the Sun does not set and one day when it does not rise. Continue with the equator, tropics and poles lesson.

Frequently asked questions

What causes day and night?

The Earth spins on its axis about once every 24 hours. Whichever half faces the Sun has daytime; the other half has night.

Why do we have seasons?

Because the Earth's axis is tilted about 23.4 degrees. As the Earth orbits the Sun, each hemisphere takes turns leaning towards the Sun, which gives it higher Sun, more direct light and longer days.

Is it summer because the Earth is closer to the Sun?

No. The Earth is closest to the Sun in early January, during northern winter.

Is the day and night line on earthglobe.app real?

Yes. It is calculated from the current time and the position of the Sun, and it updates while the page is open. The surface and city-light images are NASA composites, not live photos.