Look
at this animation. The orange circle shows where the sun's most
direct rays hit the Earth in each season. Keep an eye on Alaska
in the summer and winter. Then read below . . .
The
sun only appears to move because the Earth
is tilted on its axis.
In
the winter, sunlight hits Alaska at a low angle. (That's
because the sun's most direct rays hit south of the
equator.) Winter sun in this location doesn't get
much above the horizon, even at noon.
Noon
on winter solstice.
But
in the spring and summer, the sun's most direct rays
hit further north of the equator. In Alaska, the sun
is up high much of the day. In some areas, it doesn't
set until after midnight!
Midnight
near summer solstice.
As
Alaska (and the rest of North America) moves toward
spring and summer, it gets more direct sunlight and
more hours of sunlight. That means that more energy
hits the Earth. And that warms up our atmosphere
and triggers the green wave of spring!