Science of the Season: Summer Solstice

Science of the Season: Summer Solstice

BY : Rhiannon Nevinczenko

Summer solstice marks the first day of summer in the Northern Hemisphere. In the Southern Hemisphere, the same date marks the opposite season - the winter solstice, first day of winter. For those of us in the Northern Hemisphere, this is the longest day and shortest night of the year. This is true regardless of whether your location observes Daylight Savings Time, because the length of the day has everything to do with Earth's relationship with the Sun (and little to do with what number we name an hour with). 
Because Earth is tilted at 23.5 degrees on its axis, different parts of the planet get more direct or indirect sunlight depending on which side is tilted towards or away from the Sun. In other words: In the summer, the Northern Hemisphere is tilted towards the Sun, and receives more direct sunlight. Likewise, in the winter, it is tilted away from the Sun, and receives indirect sunlight by comparison. 
Notice how the Sun's position seems to almost pause on the analemma (see the infographic) at the summer and winter solstice. This is how the term solstice came about, because the Sun appeared to pause for a few days. (Sol = Sun, stice = stop). 
The analemma is a figure-eight figure that shows the Sun's position at different times of the year. The arcs on the diagram, on the other hand, show how the sun moves through the sky from sunrise to sunset on the solstices and equinoxes. The analemma and arcs meet at noon. 
Graphics/illustration by R. L. Nevinczenko.

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