I love daily posts of Astronomy Picture of the Day on FaceBook.
Here's a doozie.
Image Credit: NASA, Meteosat, Robert Simmon
This is link to the video...
Explanation:
Welcome to an equinox on planet Earth. Today is the first day of
spring in our fair planet's northern hemisphere, fall in the southern
hemisphere, with day and night nearly equal around the globe. At an
equinox Earth's terminator, the dividing line between day and night,
connects the planet's north and south poles as seen at the start of this
remarkable time-lapse video compressing an entire year into twelve
seconds. To make it, the Meteosat satellite recorded these infrared
images every day at the same local time from a geosynchronous orbit. The
video actually starts at the September 2010 equinox with the terminator
aligned vertically. As the Earth revolves around the Sun, the
terminator tilts to provide less daily sunlight to the northern
hemisphere, reaching the solstice and northern hemisphere winter at the
maximum tilt. As the year continues, the terminator tilts back again and
March 2011 equinox arrives halfway through the video. Then the
terminator swings past vertical the other way, reaching the the June
2011 solstice and the beginning of northern summer. The video ends as
the September equinox returns.
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