- Creation Date: November 14, 2012
- Academic Subject:
Our video will start with the narrator setting the scene – the viewer (represented on-screen by a buffalo) decides to visit his or her friend in Australia (a kangaroo) next summer. The friend will be surprised when the viewer shows up in June. That’s the middle of winter – in Australia, at least. Here we’ll pose the main question we answer – why are the seasons opposite in the Northern and Southern hemisphere?
We’ll explain how it’s the tilt of the Earth and the revolution of the Earth around the Sun that cause the seasons. We’ll first talk about the revolution around the Sun, explaining that there’s an orbital plane in which the Earth travels. Here, we’ll also discuss the concept of solstices and equinoxes, pointing out where the Earth is in its revolution when these dates occur. Next, we’ll show that the Earth is tilted 23.5° off this orbital plane. We’ll show how during July, August, and September, the Northern Hemisphere is tilted towards the Sun. Using a flashlight and a globe, we’ll show how sunlight shines directly on the Northern Hemisphere and indirectly on the Southern Hemisphere. We’ll explain that direct sunlight leads to more heating in that area (“summer”) and indirect sunlight leads to less heating (“winter”). We’ll then discuss the months of January, February, and March, and how the Southern Hemisphere receives direct sunlight and the Northern Hemisphere receives indirect sunlight. This is the reason why the two hemispheres have opposite seasons. We’ll also note that these changes are more extreme the closer you get to the poles.
We feel that this concept leads very nicely into a discussion of how the tilt of the Earth also influences the length of a day. However, this would be too much information for the seasons video. So, we proposing make a second 5-minute video, in which the viewer (the buffalo) visits his or her friend (a reindeer) in Norway during the summer. It’s difficult to tell when it’s time to go to bed, because the sun never sets. The two of them discuss how the length of the day is longer when your hemisphere is tilted towards the sun (winter), and is proportional to your distance from the Equator. We’ll talk about how anything within the Arctic and Antarctic Circles (which are approximately 66.5° N/S (90-23.5, which is Earth’s tilt)) experiences 24 hours of sunlight in the summer and 24 hours of darkness in the winter. We’ll use our flashlight and globe to demonstrate this concept, by marking a spot close to the poles and spinning the globe. The viewers will be able to see that this spot receives complete sunlight or darkness.