When the Earth takes one full lap around the
sun, we call that a year. As you know, humans
separate our year into 4 seasons: Spring, Summer,
Fall, and Winter.
I found this great image that shows the Earth and
the Sun during each season:
Figure 1. The Earth’s orbit around the sun.
Notice how the earth is tilted to one side.
This tilt is the key to understanding how the
sunlight is different for each hemisphere.
Take a look at the left and the right sides of
Figure 1 above. On the right side is labeled
“Summer Solstice,” and the left side is
labeled “Winter Solstice.” These labels
refer to the seasons we experience in the Northern
hemisphere. As you can see, at the Summer
Solstice, the North pole is tiled towards the sun:
Figure 2. Earth (North pole) tilted towards the
sun during a Summer Solstice.
And at the Winter Solstice, the North pole is
tilted away from the sun:
Figure 3. Earth (North pole) tilted away from
the sun during a Winter Solstice.
Let’s think about our experience as residents
of the Northern hemisphere: When are the days
the longest? During the Summer! But
what happens in the Southern hemisphere at the
same time? Exactly the opposite, because while
the North pole is tilted towards the Sun, the
South pole is tilted away from the sun!
So how do we deal with the fact that each
hemisphere is oriented oppositely We simply
give the opposite season for the Southern
hemisphere as we do for the Northern. So while we
are enjoying the long days of Summer, the
Australians (and everyone else below the equator)
have the short days of winter.
Finally, we can think of every day in between the
Solstices (both Summer and Winter) as a transition
between one or the other. So while the Northern
hemisphere gets the most sun exposure on the
Summer Solstice, it gradually reduces over the
course of 6 months until we reach the other side
of the Sun, where it is now the Winter Solstice.
When the transition is exactly halfway done, we
call that an Equinox, where we mark the
beginning of Spring or Fall. Compared to Figure 2
and 3, what do you think the Earth looks at the
Equinox? Think about it, then check your
answer with the resource I’ve provided below.
So with each passing day, we get a slightly
different amount of sunlight in almost every part
of the world. Can you think of a time and place
where the sunlight is either all on, or all off
for more than a day?
If you’d like to read more, here is a great
resource, and the source for the figures as well:
All the best,
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