Bill Nye Explains the Seasons
Science
Seasons Explained by Bill Nye
The seasons. It gets cold in the winter. Flowers bloom in the spring. We get lots of sun in the summer. And leaves fall. In the fall. See, the earth seasons affect every living thing on earth. That's right. Seasons affect the way everything grows and changes every year. The reason we have seasons on earth is because the earth is tilted. Now let's say that this is the earth. And there's an imaginary line going through the middle of it called the earth's axis. It's tilted, and it stays tilted as the earth goes around the sun, and a 100,000 kilometers an hour. That's a billion kilometers every year. Now, not only is the earth going around the sun, but the earth is spinning. Now when you're in the part of the earth, it's toward the sun, it's daytime. And when you're on the part of the earth that's away from the sun, it's nighttime.
Now the seasons work in kind of the same way. When the part of the earth that you're on is tilted toward the sun, it's summertime there. So when it's summertime here at Nye laboratories, on the other side of the world, it's winter time in places like South America and Australia. He built your shoes on time. Oh, thanks. Then, when the part of the earth that we're on is tilted away from the sun, it's winter time here. And it's summertime, on the other side of the world. Isn't that wild? All because the earth's axis is tilted. That's the reason for the seasons. Why are the north and south poles, the coldest places on the earth? Well, please consider the following. Let's say that this heat lamp is like the sun, because it's hot. And let's say that this globe is like the earth. Because it looks like the earth.
Anyway, we've mounted thermometers on the earth like this. See? Now the one at the equator is just about off the scale. And the one at the South Pole is right around the room temperature Mark. And the ones in between are somewhere in between. That's because the heat is hitting the one at the equator, almost straight on. Or as at the poles, it's just barely grazing by. And then somewhere in between, well, it's somewhere in between. You see, it's not that the equator is closer to the heat. It's that the heat is hitting it more straight on. See if the earth were sitting like this, then this thermometer would be the hottest, and this one would be the coldest. Anyway, that's why the very warmest places on the earth are right around the equator, tropical rainforests and jungles. In the very coldest places, are at the poles because they're the ones that the energy from the heat lamp just barely grazes by. I mean, the energy from the sun.
Anyway, thank you for joining me. Do you notice though that the axis about which the earth turned is not straight up and down. It's tilted to one side, and an angle of 23 and a half degrees from the perpendicular. This has a lot to do with why we have different seasons, as we shall see. Let's say that this plastic globe of science is like the earth. And we have two solar panels. Now, solar panels convert light directly into electricity. So right now, these two panels are making enough electricity to run these two little motors. Now right now, both motors are going about the same speed. Now notice that we have one panel in the northern half of the earth, the northern hemisphere, and one panel in the southern half of the earth. The southern hemisphere. They're both receiving about the same amount of light. But let's say it's summer. Here at Nye laboratories in the northern half of the earth, the northern hemisphere. That means that the earth would be tipped toward the sun, felt like.
The motor in the southern hemisphere is just barely moving. And the motor in the northern hemisphere is spinning like crazy. Now let's say it's 6 months later. And the earth is going around the sun so that it's access is tipped. This way, look, it's reversed. The one in the south is going wild. And the one on the north slowed way down. See what that means is that this panel in the southern hemisphere is receiving more white, more energy from the sun than the one in the northern hemisphere. It's just like the earth seasons right here with the solar panel plastic globe of science. Using a flashlight you can see for yourself the direct rays are concentrated on a smaller area than planted rain. This is why direct rays produce more heat.