A twirling
ballerina
Rotation
 The Earth rotates on
its axis (imaginary
vertical line around
which Earth spins)
every 24 hours.
 It causes day and
night.
Revolution
 It takes the Earth 365.25 days (or
rotations) to travel or revolve around the
Sun once. This is called a year.
Why do we
have
seasons?
The key is that Planets are…
The best planet ever!
and…
It’s…
the…
The Earth doesn’t sit perfectly
straight up and down
A “false” view of
Earth rotating on its
axis.
This just isn’t right!
Our Axis is TILTED!
About 23.5 degrees
A more accurate view…
Notice the…
Insolation
It’s all about
CONCENTRATION!
Look at a ray of sunlight
hitting the middle of the
planet.
The ray hits this part of
the planet directly, giving
it a lot of energy (HEAT!),
and focusing this energy
over a small area.
Venus, lit by the Sun
But at the north & south pole?
Here comes a ray from
the sun toward the south
pole of Venus…
the direct ray of light
notice how much bigger an area the ray
covers…this means it’s
LESS concentrated!
That same picture of Venus
Angle of incidence…
equator vs. poles
North Pole
Equator
Earth
South Pole
Thus, Insolation is more intense near the equator compared to the poles.
For this reason, it’s warmer near the equator than at the poles.
Tilt of the Earth’s axis towards
or away from the sun creates the seasons
SUMMER (Northern Hemisphere)
When the north pole tilts toward the
sun, it gets more radiation – more warmth
during the summer
When the north pole tilts toward the
sun, the south pole tilts away
So when it’s summer in the north,
it’s winter in the south
WINTER (Southern Hemisphere)
Tilt of the Earth’s axis towards or
away from the sun creates the seasons
When the north pole tilts away
from the sun, it gets less Insolation –
So it’s colder during the winter
When the north pole tilts away from the
sun, the south pole tilts toward it…
When it’s winter in the north,
it’s summer in the south
WINTER (Northern Hemisphere)
SUMMER (Southern Hemisphere)
And the final piece to the
puzzle?
So, the TILT is a big part of it, and that the Earth revolves
around the Sun!
Identifying the Seasons
Northern
Hemisphere is
Summer and
Southern
Hemisphere is
Winter
because the
Northern
Hemisphere is
tilted towards
the Sun.
Step 3: For each position
Step
1: Draw
of the
Earth,imaginary
identify the
Step 2: lines
Put ato
“N”
and
“S”the
to
separate
season
for
both
the
Northern Hemisphere is
identify
the hemispheres.
Northern/Southern
Northern
Hemisphere
Spring and Southern
Hemispheres
(not
exact).
andisthe
Southern
Hemisphere
Fall.
Neither
Hemisphere
WHY.
Hemisphere
is tiltedand
directly
towards the Sun.
Northern
Hemisphere is
Winter and
Southern
Hemisphere is
Summer
because the
Southern
Hemisphere is
tilted towards
the Sun.
Northern Hemisphere is Fall and Southern Hemisphere is
Spring. Neither Hemisphere is tilted directly towards the Sun.
Solstices
 Occur twice a year, when the tilt of the Earth's axis is oriented
at its extremes. Tilted the farthest or closest
 Winter solstice is the shortest day of the year. In the Northern
Hemisphere. It occurs on December 21 or 22 and marks the
beginning of winter.
 The Summer Solstice is the longest day of the year. It occurs
on June 20 or 21 and marks the beginning of summer.
Equinoxes
 A day lasts 12 hours and a
night lasts 12 hours at all
latitudes.
 Equinox literally means
"equal day and night".
 Sunlight strikes the earth
most directly at the equator.
 This occurs twice a year.
So, In Summary…
Fact 1: Round planets heat up wherever they get direct sunlight
and are cooler at the tops and bottoms.
Fact 2: The Earth’s axis is TILTED 23.5o.
Fact 3: As Earth revolves around the Sun, the tilt causes different
parts of it to receive more or less sunlight for a few months,
causing the weather and daylight to change.
Fact 4: The equinox marks the time when daylight and nighttime are approximately the same length, with solstice occurring
on the longest and shortest days (in terms of sunlight).
So it’s a combination of the
TILTed axis and the revolution
of the Earth around the sun.
Activities for dry
season? And wet
season?
Dry Season
1.
2.
3.
4.
5.
Wet Season
1.
2.
3.
4.
5.