![]() Terrence Antonio James/Chicago Tribune/Getty Images The setting sun is seen looking west on Randolph Street in Chicago just days before the autumnal equinox in 2019. ![]() Precisely when does the fall equinox happen? Here are the answers to some of your fall equinox questions:įrom our CNN Fast Facts file: The term equinox comes from the Latin word equinoxium, meaning “equality between day and night.” More on that farther down in the article. There’s a good explanation (SCIENCE!) for why you don’t get precisely 12 hours of daylight on the equinox. Well, there’s just one rub – it isn’t as perfectly “equal” as you may have thought. They have long, dark winters and then have summers where night barely intrudes.īut during the equinox, everyone from pole to pole gets to enjoy a 12/12 split of day and night. But hardy folks close to the poles, in places such as Alaska and the northern parts of Canada and Scandinavia, go through wild swings in the day/night ratio each year. People really close to the equator have roughly 12-hour days and 12-hour nights all year long, so they won’t really notice a thing. People in the Americas will celebrate it on Thursday time zone differences mean people in Africa, Europe and Asia will mark it on their Friday. Your location on the globe also determines whether you mark the day this year on Thursday, September 22, or Friday, September 23. For people south of the equator, this equinox actually signals the coming of spring. If you reside in the Northern Hemisphere, you know it as the fall equinox (or autumnal equinox). On Saturday, we enter our second equinox of 2018. Everyone on Earth is seemingly on equal status – at least when it comes to the amount of light and dark they get. At the same time, the Southern Hemisphere is tilted away from the sun and experiencing winter.Twice a year, the sun doesn’t play favorites. When the Northern Hemisphere is tilted toward the sun, latitudes between the equator and 90°N (the North Pole) are experiencing summer. The combination of more direct rays of sunlight and more hours of daylight causes the hemisphere tilted toward the sun to receive more solar radiation and to have warmer temperatures. The hemisphere tilted toward the sun also has more hours of daylight than the hemisphere that is tilted away from the sun. Whichever hemisphere (the Northern or Southern Hemisphere) is tilted toward the sun receives more direct rays of sunlight (or rays that are closer to perpendicular or a 90° angle). Earth is actually a little farther from the sun when the Northern Hemisphere is having summer. This is a misconception because Earth's orbit is only slightly elliptical and our planet is nearly the same distance from the sun all year long. ![]() People often mistakenly think that the different seasons are caused by a change in Earth's distance from the sun. Similar to the previous graphic but this perspective is vertical and looking down at the North Pole. Because the direction and angle of the axis of rotation do not change, the Northern Hemisphere is tilted toward the sun during part of the year and away from the sun during another part of the year. The direction and angle (or tilt) of Earth's axis of rotation do not change as Earth revolves around the sun. When we add a day every 4 years to align the calendar, this year is often called a leap year.Īt the present time, Earth is tilted on its axis of rotation by 23.5°. To keep our calendars synchronized with the planet's actual orbit, every 4 years we add an extra day to the month of February – 4 quarters of a day (1 quarter each year for 4 years) equals 1 day or 24 hours. Earth takes 365 and ¼ (6 hours) days to complete one revolution around the sun. Like the other planets, Earth rotates on its axis as it revolves around the sun. This is a horizontal perspective facing the equator. This graphic shows Earth with its 23.5° tilt, the direction of its rotation and the pattern of the seasons as it travels around the sun. ![]()
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