In my neck of the woods, we’re in what you call “Four Season Country.” We’ve get a fairly definitive Winter, Spring, Summer, and Autumn here every year. Our local nine do their spring training in Florida, however, where it’s basically Summer, Summer, Summer, and Summer. I traveled down thataway to take in a few spring training games this past year, and promptly got sunburnt to $#!t, despite having applied sunscreen the same way I do in the height of summer here at home.
The difference in this case, your students should understand, is not the amount of sunlight I was exposed to that led to me getting lobstered. Rather, it was the angle of the sunlight that got me. What does that mean, exactly? This easy peasy lemon squeezy Demo Science science demo will help you explain how sunlight can actually be hotter from different angles.
Time for A Latitude Adjustment
All you need for this experiment are a flashlight and a dark-colored sheet of paper. A good ol’ 8-1/2” x 11” will work just fine, but the bigger the paper the better. You’ll also need an open space on the floor large enough to lay said paper down flat on. So maybe don’t get too carried away with your giant sheet of black craft paper.
Lay the paper flat on the floor of your classroom and have your students gather ‘round. (Try not to step on the paper, Kevin!) Have whatever smelly little kid is closest hit the lights, then shine your flashlight straight down on the paper from above. Instruct your students to observe how the light strikes the paper.
Then, angle your flashlight so its beam hits the paper at a slant. If you go nice and slow betwixt straight up and angled, students who are paying attention carefully will get an even better idea of how angle affects sunlight. Hold your flashlight at whatever angle you like, and again have your students observe the light closely.
Ask ‘em what they saw and/or deduced.
I Saw the Light
With the flashlight pointed straight down, the light striking the paper creates a small and intense circle. When the light is slanted, it creates a larger but dimmer oval shape on the paper. Like the sunlight in the Midwest and in Florida, the light hitting the paper from both angles comes from the same source and therefore contains the same amount of light.
Here’s the important part, so take notes, Chief. Because the oval is bigger, its light is spread more thinly upon the paper. A ray of sunlight hitting the earth at an angle, as it increasingly does as one travels north—south if you’re in the Southern Hemisphere—behaves in the same way. Ergo, sunlight that shines more directly upon the ground, as it does in the lower latitudes of Florida, the same amount light and heat in a smaller area of greater intensity.
Locations at the equator—or zero degrees latitude—receive roughly two and a half times as much heat from the same amount of sunlight as the North and South Poles—90°N and 90°S latitude, respectively. You’re gonna need more sunscreen down at the equator, kids!