NASA On Air: Satellite Sees Fall Equinox From Space (9/22/2015)
LEAD: This year's fall equinox arrives WEDNESDAY, Sept. 23, at 4:21 a.m. EDT. The name equinox comes from the Latin words for "equal" (aequus) and "night" (nox). The length of day and night is the same on this date: 12 hours each.
1. Looking at the Northern Hemisphere, night is on the left and day is on the right.
2. Advancing towards December, the Northern Hemisphere night becomes longer and days become shorter. Shorter days mean less solar energy and consequently colder days.
3. It is the relative tilt of Earth as it goes around the sun that causes the seasons.
TAG: By Dec. 21, 2015, Earth’s North Pole will be tilted 23.5 degrees away from the sun.
NOTE: Time-lapse video assembled from images taken by EUMESAT's Meteosat-9 satellite in 2010 and 2011. For more information about the images, see links below.
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Credits
Please give credit for this item to:
NASA's Goddard Space Flight Center
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Video editor
- Joy Ng (KBR Wyle Services, LLC)
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Producer
- Howard Joe Witte (ADNET Systems, Inc.)
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ID: 11353 Produced Video
Follow The Line
Read moreYou may think the seasons are caused by a change in the distance between Earth and the sun. In fact, the tilt of Earth on its axis is the most important factor. You can see this from space by watching the movement of Earth’s terminator—the edge between the shadows of nightfall and the sunlight of dusk and dawn. Because Earth spins on a tilted axis, the orientation of this line changes over the course of a year in sync with the seasons. On the September and March equinox, when Earth is at a right angle to the sun, light is spread evenly across the globe and the terminator runs from pole to pole. But on the December and June solstice, when Earth is tilted away from and toward the sun, respectively, light is cast disproportionately on each hemisphere, causing the terminator to appear slanted. Watch the video to view the migration of Earth's terminator across the seasons. ||
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