Dominic Corsini has an extensive educational background with a B.S. in Secondary Biology and General Science with a Minor in Environmental Education, an M.Ed. in Educational Leadership, an M.S. in Biology, and a K-12 Principal Certification Program. Corsini has experience as a high school Life, Earth, Biology, Ecology, and Physical Science teacher.
Summer Solstice Defined
Many people throughout the northern hemisphere have likely noticed that it gets dark earlier in the winter than it does during the summer. In fact, late December marks some of the shortest days of the year with respect to daylight hours. Yet inevitably, as we move into spring the days start getting longer and continue doing so until we reach the summer solstice. The summer solstice is the longest day of the year and signifies the first official day of summer, often occurring around June 21st.
How the Summer Solstice Works
To explain the details behind the summer solstice, it is best we refer to an illustration.
There are two items worth noticing in this image. The first is the fact that Earth is tipped on its axis, and the second is that Earth is revolving around the sun in a counterclockwise manner. To begin, focus your attention on the Earth found on the far right of our image. This Earth has the northern hemisphere (top half) tilted away from the sun and the southern hemisphere (bottom half) tilted towards the sun. This means that the northern hemisphere is receiving less direct solar radiation than the southern hemisphere does. Translation: the northern hemisphere is experiencing winter, while the southern hemisphere is experiencing summer.
Now, in addition to the cold brought on by less direct solar radiation, the Earth's tilt also causes the northern hemisphere to experience shorter days during late December. As the Earth continues on its path around the Sun, the amount of solar radiation (and length of day) begins to increase. For example, the Earth shown in the back of our image has a northern hemisphere experiencing spring. As we continue along, the Earth positioned on the far left now has its northern hemisphere tilted towards the Sun. This is the position of the Earth when the northern hemisphere experiences summer and the southern hemisphere experiences winter.
The important thing to remember is that throughout this transition from winter to summer, the amount of daylight is constantly increasing. However, this cannot continue forever, because it would mean the end of night (which obviously doesn't occur). Therefore, at some point the length of day must stop getting longer and start getting shorter. This point in time is our summer solstice. It marks the time when days stop getting longer and start getting shorter. In fact, even the word solstice means sun stop. A fitting word for describing what happens to the amount of daylight we have. As we continue on our inevitable journey back toward winter, we transition through autumn, shown as the Earth in the front of our image, and the days continue to grow shorter. Eventually we reach winter when the days stop getting shorter and start getting longer (the winter solstice). And we continue this cycle again with lengthening days until the summer solstice, then shortening days until the winter solstice.
The amount of daylight we receive changes on a daily basis. It's subtle, but undeniable. As we move from the darkness of winter and into the light of summer, the length of our days increases. This trend continues until the summer solstice, which is the longest day of the year and official beginning of summer. The tilt of the Earth and revolution around the Sun are responsible for producing this phenomenon. Following the summer solstice the days get shorter until late December (when the winter solstice occurs), and then begin growing longer again in a continuous cycle.
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