September 2015 Laurelhurst Elementary Special Itinerary
The Equator and the
Prime Meridian
Please see the
Passport Club case in the front hall for information to answer these questions.
1. The Equator and the Prime
Meridian are both important lines on our globe.Which one helps us to
understand the seasons around the world?
2. At which location can the equator be found on the
globe?
3. The equator separates which two hemispheres?
4. What does the Prime Meridian
mark?
5. The Prime Meridian helps divide the earth into these two
hemispheres:
6.
Why do we have seasons?
Bonus: Where in the world would you like to be on December
21st?
Tell which hemispheres your location is in (Northern or
Southern, Eastern or Western) and if you would be observing the summer
or
winter solstice on that day.
Two Seasons at the Same
Time?
Charlie lives in Portland, Oregon.
His pen pal, Benicio, lives in Argentina. The boys enjoy writing letters to
each other and sharing interesting things about their lives. Charlie sends
Benicio a photo of his family’s summer camping trip they took last week.
Benicio sends Charlie a picture of himself on a recent skiing vacation with his
grandparents.
Charlie realizes that even though
he’s at the tail end of summer, his friend is looking forward to the coming of
spring. But how can there be two very different seasons at the same time?
The Axial Tilt and the
Equator
As the earth travels around the sun
each year, the amount of light in a day changes because the earth’s axis--the
invisible line down the center of the Earth—is not straight up and down but
actually at an angle. This angle is called the axial tilt. That tilt does two things:
- It changes the number of hours of daylight at each latitude depending on the position of the earth’s orbit around the sun. This is easiest seen by putting a pencil through a tennis ball and holding it at a fixed tilt while circling a light bulb.
- It impacts the angle of incidence of the light hitting the surface which impacts the strength of the irradiance in exactly the same way that the angle of a force pushing on something affects the force applied. The quickest experiment to demonstrate this is to shine a flash light directly on a surface and see how well lit it is. Then change the angle to be more oblique and you’ll see the light is more spread out and the surface less well lit.
The equator is fixed line which goes around the Earth at the location
of 0 degrees latitude. This divides the earth into the Northern and Southern
Hemispheres, which experience their seasons opposite each other. Beautifully,
as each hemisphere marks their own seasons, there are two days each year when
day and night are the same length in both hemispheres. We call these the
equinoxes; our longest day of sun is the summer solstice and the shortest day
of winter is the winter solstice. While the equinoxes are shared between
hemispheres, the solstices each have their own dates depending on which side of
the equator you live, north or south.
Solstices and Equinoxes
For both
hemispheres, the equinoxes are observed on March 20 or 21st and
September 22 or 23rd.
For the
Northern Hemisphere, our Summer Solstice takes place on June 21st or
22nd, when the Southern Hemisphere is celebrating their Winter
Solstice.
The Southern
Hemisphere’s Summer Solstice is on December 21st or 22nd,
while we are putting on mittens and scarves and observing our Winter Solstice.
(So, if it’s the
equator that helps us understand our seasons, what is the Prime Meridian?)
Just as the equator divides the globe
into Northern and Southern hemispheres, the Prime Meridian is a vertical line
which divides the globe into Eastern and Western Hemispheres. The Prime
Meridian is located at 0 degrees longitude and reaches halfway around the Earth
to a 180 degree mark on the opposite side of the globe. Please do not confuse
the Prime Meridian with the International Date Line, which is located at
roughly 180 degrees longitude.
(A special thank you to Justin Sharp, an atmospheric scientist and Laurelhurst parent, who gave me some extra direction to making this explanation better and more substantial and offered text to this site. Much Appreciated!)
(A special thank you to Justin Sharp, an atmospheric scientist and Laurelhurst parent, who gave me some extra direction to making this explanation better and more substantial and offered text to this site. Much Appreciated!)
