Equator, tropics and poles: a globe lesson

On a classroom wall map the equator and the tropics are printed lines, and students rarely ask what they mean. This lesson gives them a reason: these five circles mark where the Sun can be straight overhead, and where it can stay up, or stay down, for a whole day. Students find the real countries each line crosses, then connect the lines to sunlight.

Suggested age: 9–13 · Time: about 40 minutes · Links: all lessons · for schools

Learning goals

By the end of the lesson students can:

1. Name the five main circles of latitude: the equator, the Tropic of Cancer, the Tropic of Capricorn, the Arctic Circle and the Antarctic Circle.
2. Give the approximate latitude of each one.
3. Name at least two countries on each line.
4. Explain what the tropics and the polar circles have to do with the tilt of the Earth.

What you need

• The globe at earthglobe.app on a projector (press Classroom mode) or one device per pair.
• A worksheet or board table with five columns: Equator, Tropic of Cancer, Tropic of Capricorn, Arctic Circle, Antarctic Circle.

The five lines at a glance

The tropics sit at about 23.4 degrees because that is how much the Earth's axis is tilted. The polar circles sit at about 90 − 23.4 = 66.6 degrees for the same reason. (The tilt slowly changes over thousands of years, so the lines move a few metres every year.)

Step-by-step globe activity

1. Ask first (3 min). "Where on Earth is the Sun straight overhead at noon?" Most students will say "at the equator". Keep the answer on the board; you will come back to it.
2. Walk along the equator (8 min). The equator crosses the land of 11 countries. Search for each in turn and tap it to see its card:
   • South America: Ecuador (the line passes about 24 km north of central Quito), Colombia, Brazil.
   • Africa: São Tomé and Príncipe, Gabon, Republic of the Congo, DR Congo, Uganda (about 32 km south of Kampala), Kenya, Somalia.
   • Asia: Indonesia (the city of Pontianak sits on it).

   Ask students to imagine a line joining them. Which ocean does it cross in between?

3. A trick question (2 min). Search for Equatorial Guinea. Is it on the equator? (No. The mainland is north of the line, and its island of Annobón is south of it.)
4. Find the Tropic of Cancer (6 min). It runs through Mexico, the Bahamas, Algeria, Niger, Libya, Egypt, Saudi Arabia, United Arab Emirates, Oman, India, Bangladesh, Myanmar, China and Taiwan. Pairs pick four and find them. What kind of land do they see in North Africa and Arabia along this line? (Mostly desert.)
5. Find the Tropic of Capricorn (6 min). It runs through Chile, Argentina, Paraguay, Brazil (near São Paulo), Namibia, Botswana, South Africa, Mozambique, Madagascar and Australia (just north of Alice Springs). Only four countries lie completely south of it: Uruguay, Lesotho, Eswatini and New Zealand. Ask students to find them.
6. Go north to the Arctic Circle (5 min). Turn the globe to the top. The Arctic Circle crosses Norway, Sweden, Finland, Russia, the United States (Alaska), Canada, Greenland and just touches Iceland (the small island of Grímsey). The Antarctic Circle runs almost entirely around Antarctica and the ocean.
7. Bring in the Sun (5 min). In Satellite mode, look at the line between day and night near the poles. Explain: because the axis is tilted, the Sun is only ever straight overhead somewhere between the two tropics, and the polar regions lean into or away from the Sun for months at a time. Go back to the question from step 1: the Sun is overhead at the equator only around the equinoxes in March and September; at other times it is overhead somewhere else in the tropics.
8. See the lines (3 min). Turn on the latitude lines and check the countries students found.

Questions for students

1. What is the latitude of the equator?
2. Name two countries in South America and two in Africa that the equator crosses.
3. At about what latitude are the Tropics of Cancer and Capricorn? Why that number?
4. What happens at the Arctic Circle around 21 June?
5. Is the Sun straight overhead at the equator every day at noon? Explain.
6. Is Equatorial Guinea on the equator?

Answer key (for the teacher)

1. 0 degrees.
2. South America: Ecuador, Colombia, Brazil. Africa: São Tomé and Príncipe, Gabon, Republic of the Congo, DR Congo, Uganda, Kenya, Somalia (any two).
3. About 23.4 degrees north and south (23°26′). That is the tilt of the Earth's axis.
4. Around the June solstice the Sun does not set there for at least one day (midnight sun). Around the December solstice it does not rise for at least one day (polar night).
5. No. The Sun is straight overhead at the equator around the equinoxes (about 20 March and 23 September). In June it is overhead near the Tropic of Cancer, and in December near the Tropic of Capricorn. At the equator the noon Sun is always high, never more than about 23 degrees from straight up, which is why it stays warm all year.
6. No. Its mainland is north of the equator and the island of Annobón is about 155 km south of it.

Optional extension

How far are you from the equator? Switch to Distance mode, tap your town, then tap a point on the equator roughly straight south (or north) of you. Students read the distance in kilometers and miles. The equator is about 40,075 km (24,901 mi) around: what fraction of that is your distance? Follow up with day and night & the seasons.

Frequently asked questions

What is the latitude of the Tropic of Cancer?

About 23.4 degrees north (23°26′). It moves very slowly, by about 15 metres a year, because the Earth's tilt changes over thousands of years.

What is the difference between the Tropic of Cancer and the Tropic of Capricorn?

The Tropic of Cancer is in the Northern Hemisphere and marks the farthest north the Sun is ever straight overhead. The Tropic of Capricorn is the same line in the Southern Hemisphere.

How long is the equator?

About 40,075 km (24,901 miles).

Where can I see these lines on earthglobe.app?

Turn on the latitude lines.