Concepts: seasons, axis of rotation
Skills: observing, critical thinking
Safety first! Light bulbs can get very hot. Make sure your hands and other objects do not touch the bulb.
People often think that it is hotter in the summer (in the northern hemisphere) because the Earth is closer to the Sun. In fact, in the northern hemisphere summer, the Earth is farther away!
The reason for the difference in temperature between the summer and the winter actually has to do with the tilt of the Earth’s axis. If the Earth were not tilted at an angle, there would be no summer or winter.
In the summer, the northern hemisphere is tilted toward the Sun which means that the Sun’s rays hit this part of the Earth’s surface more directly. Since there is more direct sunlight, more of the Sun’s energy is absorbed by the land surface. As a result, the temperature is higher. Depending on where you live in relation to the equator, if you look up towards the Sun at noon (12 p.m.) in the summer, you will see that the Sun is higher in the sky than it is in the winter.
In the winter, the northern hemisphere is tilted away from the Sun, which means that the Sun’s rays hit this part of the Earth in a more oblique or slanted manner. Since there is less direct sunshine, less energy is absorbed by the surface and the temperature is lower. If you look up towards the Sun at noon in the winter, you will see that the Sun lower in the sky.
The southern hemisphere experiences the reverse of the northern hemisphere. When it is summer in the northern hemisphere, it is winter in the southern hemisphere and vice versa. So remember, seasons are all about the tilt of the Earth’s axis, not the distance between the Earth and the Sun!
Why does it matter?
The tilt of the Earth as it travels around the Sun determines our seasons.
Try the activity again, changing the tilt of your Earth. What would happen if the Earth had no tilt? What if it was tilted at 90°?