The Earth in its orbit at the solstices and equinoxes.
Click on image for full size
The Seasonal Merry-Go-Round
The tilt of Earth's rotational axis and the Earth's orbit work
together to create the seasons. As the Earth travels around the Sun,
it remains tipped in the same direction, towards the star Polaris.
This means that sometimes the northern half of the Earth is pointing
towards the Sun (
summer), and sometimes it
is pointing away (
winter). These points in
the Earth's orbit are called
solstices.
Notice that when the northern hemisphere is tilted towards the Sun,
the southern hemisphere is tilted away. This explains why the
hemispheres have opposite seasons.
Halfway in between the solstices, the Earth is neither tilted directly
towards nor directly away from the Sun. At these times, called the equinoxes, both hemispheres receive roughly
equal amounts of sunlight. Equinoxes mark the seasons of autumn and
spring and are a transition between the two more extreme seasons,
summer and winter.
Shop Windows to the Universe Science Store!
The
Summer 2010 issue of The Earth Scientist, available in our
online store, includes articles on rivers and snow, classroom planetariums, satellites and oceanography, hands-on astronomy, and global warming.
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