Today, Wednesday June 20, is the summer solstice. Ok sure, so it’s the longest day of the year. Big deal. Why does it matter?
Like most models you may have seen, our solar system actually lies in one flat plane, for the most part. However, Earth does not rotate on a vertical axis like a top. Instead the entire planet is tilted at a 23.5° angle towards the Sun, and rotates on an axis that points directly towards the North Star. This is why the North Star never moves throughout the night sky, and is directly overhead if you’re at the North Pole.
As the Earth travels around the Sun, some parts are more directly exposed to sunlight than other parts. This is why it is winter in the Southern Hemisphere when the Northern Hemisphere is in the middle of summer. Today on the Solstice, Earth’s axis points as much toward the sun as it will throughout its orbit, which for us means the most hours of sunlight throughout the year. People above the Arctic Circle are at a high enough latitude that they will actually experience daytime for a continuous 24 hours, and in Antarctica there is no sunlight at all!
The orbit of Earth, and all of the planets actually, is not a perfect circle but instead is in the shape of an ellipse, or a special type of oval. The two Solstices occur at the points on the ellipse when the Earth is farthest from the Sun; since the force of gravity is slightly lessened by this increase in distance, the oceans experience noticeably lower low tides than occur at other times during the year.
So be sure to pack up your sunscreen and your bathing suit and enjoy the sun while it lasts! Although today may be the first day of summer, the days will only get shorter from here, so be sure to make them last!