Seeing Equinoxes and Solstices from Space [hd animation]
Images acquired December 21, 2010 - September 20, 2011.
To download the high res and learn more go to: earthobservatory.nasa.gov/IOTD/view.php?id=52248
One of the most frequently misunderstood concepts in science is the reason for Earth’s seasons. As we experience the September equinox today—anyone try to balance an egg yet?—we thought we’d offer a space-based view of what’s going on.
Around 6 a.m. local time each day, the Sun, Earth, and any geosynchronous satellite form a right angle, affording a nadir (straight down) view of the terminator, where the shadows of nightfall meet the sunlight of dusk and dawn. The shape of this line between night and day varies with the seasons, which means different lengths of days and differing amounts of warming sunshine. (The line is actually a curve because the Earth is round, but satellite images only show it in two-dimensions.)
The Spinning Enhanced Visible and Infrared Imager (SEVIRI) on EUMETSAT's Meteosat-9 captured these four views of the day-night terminator on December 21, 2010, and March 20, June 21, and September 20, 2011. Each image was taken at 6:12 a.m. local time.
On March 20 and September 20, the terminator is a straight north-south line, and the Sun is said to sit directly above the equator. On December 21, the Sun resides directly over the Tropic of Capricorn when viewed from the ground, and sunlight spreads over more of the Southern Hemisphere. On June 21, the Sun sits above the Tropic of Cancer, spreading more sunlight in the north and turning the tables on the south. The bulge of our spherical Earth blocks sunlight from the far hemisphere at the solstices; that same curvature allows the Sun’s rays to spread over more area near the top and bottom of the globe.
Of course, it is not the Sun that is moving north or south through the seasons, but a change in the orientation and angles between the Earth and its nearest star. The axis of the Earth is tilted 23.5 degrees relative to the Sun and the ecliptic plane. The axis is tilted away from the Sun at the December solstice and toward the Sun at the June solstice, spreading more and less light on each hemisphere. At the equinoxes, the tilt is at a right angle to the Sun and the light is spread evenly.
The equinox and changing of the seasons occurs on September 23, 2011 at 9:05 a.m. Universal Time. (Our September image above is a few days early.) Equinox means "equal night" in Latin, capturing the idea that daytime and nighttime are equal lengths everywhere on the planet. That is true of the Sun's presence above the horizon, though it does not account for twilight, when the Sun's rays extend from beyond the horizon to illuminate our gas-filled atmosphere.
NASA images and animation by Robert Simmon, using data ©2010 EUMETSAT. Caption by Mike Carlowicz.
Instrument: Meteosat
Credit: NASA Earth Observatory
NASA Goddard Space Flight Center enables NASA’s mission through four scientific endeavors: Earth Science, Heliophysics, Solar System Exploration, and Astrophysics. Goddard plays a leading role in NASA’s accomplishments by contributing compelling scientific knowledge to advance the Agency’s mission.
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Comments and faves
AnimatedMartian, MENONITRO, RavenEcho (edward steven perry), Sight of Jules, and 181 other people added this video to their favorites.
K)) [deleted] (20 months ago | reply)
Very interesting!
Fabietto76°OZ (20 months ago | reply)
Wonderful!!
Roger Hooton (20 months ago | reply)
Beautiful.
Cliff's Photography, Thank you for all visits!! (20 months ago | reply)
Awesome!!!
█ fo112 █ (20 months ago | reply)
Nice!
DarkAngelDay (20 months ago | reply)
wow! Cool
Rafał P. (20 months ago | reply)
Great shot!!!
bartholowaty | Photography (20 months ago | reply)
WOW!!!!!! Superb Pic ;)
very nice Image, Stunning composition.
...keep up your really good work ;-)
Bart
Please take time to check my photos.
If you like them please add me as contact.
natasayu (20 months ago | reply)
Stunning
_SG_ (20 months ago | reply)
fantastic pic!
[ via flickriver explore --_SG_ ]
2013AD (20 months ago | reply)
incredible. we are very fortunate to live in this wondrous universe
la india del cibao (20 months ago | reply)
I saw this beautiful video on Explore !
September 23, 2011
Salaatti (20 months ago | reply)
This is amazing!
2013AD (20 months ago | reply)
www.youtube.com/watch?v=8Lm6pEhykhs
Blue Ballon,cherry (19 months ago | reply)
amazing
PHablito PHotography (16 months ago | reply)
no comment
Roger Hooton (14 months ago | reply)
In Australia the seasons start on March 1st Autumn - June 1st Winter - September 1st Spring - December 1st Summer and not by the position of the Earth and Sun dates.
Does anyone know why we persist in the lie that the Sun RISES and the Sun SETS each day? Surely we are intelligent enough to know that it does not and we should call such by more truthful names. How about giving such new names. Thanks.
GeirO4 (14 months ago | reply)
Fantastic
[ lee ] (14 months ago | reply)
Very cool!
I think it would be more obvious what is happening if we were able to see the terminus stationary with the Earth tilting up and down.
UN3X (14 months ago | reply)
amazings!
Unlucky_Alf [deleted] (14 months ago | reply)
Nice one.
jaffles (14 months ago | reply)
Wonderful !
Éothain (14 months ago | reply)
Wow
petrus.13 (14 months ago | reply)
great
my last pic:
--
Seen in my contacts' photos. ( ?² )
Mariano R (14 months ago | reply)
12 seconds to explain 1 year. Excellent work !!!
dodagp (14 months ago | reply)
Enlightening work !!!!!!
Personally, I didn't make any attempt to balance the egg... Loved the fact though that you mentioned it ...
TheVoid91 (13 months ago | reply)
great