Night and dayĪt the solstices in June and December, we celebrate the longest and shortest days of the year. And if you’re seething about summer’s end, consider moving closer to the Equator. So, if the chillier air and crispier leaves have you happily reaching for pumpkin-flavored everything, thank Earth’s tilt-not its distance from the sun. “If the light is angled, it’s not going to be as hot.” “What it has to do is the amount of light per square centimeter that’s falling on you,” says Dan Milisavljevic an astronomy professor at Purdue University. At the same time, the southern half of Earth is tilted away from the sun and catches its rays at an angle, causing the cooler, shorter days of winter.Įarth is bathed evenly in sunlight only twice a year, on the equinoxes. When the planet's Northern Hemisphere is tilted toward the sun, sunlight hits it head on, bringing summer’s heat and longer days. So if it’s not Earth’s changing proximity to the sun, what gives us seasons? It's all in the slant: Earth's axis isn’t straight up and down relative to the sun, but tilted at a slight angle of about 23.5 degrees.Īs Earth revolves around the sun, it maintains that tilt, and the sun’s light doesn't hit the entire surface directly. “So in the northern winter-in December-the sun is actually closest to the Earth by a small amount, and in the summer it’s actually farther away.” “The Earth’s orbit is about 3 percent out of round,” explains Jay Holberg, a senior research scientist at the lunar and planetary lab at the University of Arizona. The Harvard grads-captured forever in 1980s hair and their caps and gowns-were wrong. After all, Earth’s orbit isn’t a perfect circle. With varying degrees of confidence, the students explain that the Earth gets warmer or colder based on its distance from the sun. In a grainy video, a group of newly fledged Harvard graduates is asked why we have seasons. Want to know why equinoxes happen, what to expect, and how they have been celebrated through the ages? We've got you covered. Even though an equinox happens twice a year, every year, there are a lot of misconceptions about this seasonal transition. (See gorgeous pictures that celebrate the arrival of fall.)įor the other half of the planet, September 22 is the vernal equinox, signaling the beginning of spring. The Northern Hemisphere blew by the longest day of the year with June’s summer solstice and is now coming up to the fall equinox on September 22, 2020-the day when the sun passes directly over Earth’s Equator.
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