I hate to see spring go. So much comes with the season: the flowers, fireflies, warm weather, the Summer Triangle and Milky Way. New flowers continue to bloom through the season just as new constellations rise in the east, but summer feels like a plateau. We’ve spent months climbing to get here. Now it’s time to rest, have an iced drink and chill.
That mood mirrors the celestial tempo. In spring, the sun hurriedly climbs northward from its low perch in the south until reaching its highest point in the sky. That will happen at 5:03 a.m. (Central Time) Thursday, June 21, the date of the summer solstice. Because it beams down from high, its rays are more intense than those of the winter sun. That and the fact that the sun takes a considerably long path across the sky (it’s out for many more hours) makes summer hot!
There’s a lag between the first day of summer and the warmest time of year because it takes time to heat up all that land and ocean water. In mid-June, you’ll often see mountain peaks still covered in snow. That’s why mid-to-late July is usually the warmest time of year, at least for the U.S.
The build-up of heat and its lingering through August can make summer feel long. So we’re clear, summer heat has nothing to do with Earth being closer to the sun. In fact, it’s the opposite. The planet’s a few million miles further away in July than in early January, when it’s closest. It all has to do with the tip of Earth’s axis: in summer, the northern hemisphere is tipped toward the sun, so the sun appears high in the sky. In winter, it’s tipped away from the sun, so it’s low in the sky.
Earth’s orbital motion causes the sun to appear to move in a full circle against the background stars in one year. Of course, we’re doing the moving. Basically, the sun’s just sitting in one spot. And the up and down motion of the sun with the changing seasons? That’s simply a reflection of Earth’s tilted axis, which is tipped 23.5°. As the planet plies its orbit, each hemisphere alternately faces toward and away from the sun.
A word about the word “solstice.” It comes from the Latin sol for sun and sistere meaning “to stand still.” That’s because at each of the solstices, the sun’s appears to stand still at its northern limit (in summer) and southern limit (in winter) before it reverses direction. For summer, that means that at 5:03 a.m. tomorrow it simultaneously reaches it pinnacle and starts to head south once again.
So it all comes down to that tilt and the planet’s ceaseless orbiting of our closest star. Any planet that has a tipped axis will experience seasons. Planets like Jupiter and Venus, that orbit nearly straight up and down, don’t have much for seasons, but others like Mars and Saturn, do. What a difference simple astronomical facts can make in our lives.