In Canada and the rest
of the northern
hemisphere, the first
day of the spring season
is the day of the year
when the Sun crosses the
celestial equator moving
northward (on March 20th
or 21st).
This day is known as the
Vernal Equinox.
A common misconception
is that the earth is
further from the sun in
winter than in
summer. Actually,
the Earth is closest to
the sun in December
which is
winter in the
Northern hemisphere.
As the Earth travels
around the Sun in its
orbit, the north-south
position of the Sun
changes over the course
of the year because of the
changing orientation of
the Earth's tilted
rotation axes. The dates
of maximum tilt of the
Earth's equator
correspond to the
Summer Solstice and
Winter Solstice, and
the dates of zero tilt
to the Vernal Equinox
and
Autumnal Equinox.
The reason for these
changes has to do with
the Earth's yearly trip
around the sun. For part
of the year the Earth's
North Pole points away
from the sun and part of
the time toward it. This
is what causes our
seasons. When the North
Pole points toward the
sun, the sun's rays hit
the northern half of the
world more directly.
That means it is warmer
and we have summer.
Links
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The Seasons and the Earth's Orbit
- Through the Naval Oceanography Portal, the
United States Naval Observatory provides
astronomical information on the Earth's orbit
around the Sun and how it relates to the
changing seasons. |
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