The 40th Parallel

The Story Behind the Song: The 40th Parallel

One of the observations that’s been made about our species on this planet is that an astonishing number of developments that have propelled humanity forward have happened midway between the equator and the poles, around the latitude we call the 40th parallel. This song celebrates some of the great mysteries about our planet that relate to this. Why has so much change that has profoundly affected our evolution and progress taken place close to the 40th parallel?

It’s not hard to come up with possible explanations for this association between new developments and this part of the northern hemisphere. This is the temperate zone, where—unlike at the poles or the equator—climate and weather conditions vary dramatically from season to season, even day to day. Creatures living in this zone have to adapt to heat and cold, rain and drought.

Furthermore, wind is a huge factor in how our civilizations have progressed at this latitude. If the Earth didn’t spin, the hot air at the equator would tend to move toward the poles at high altitudes, and the cold air at the poles would tend to move south toward the equator at ground level. But because the Earth spins, the Coriolis Effect makes any object that’s initially moving north or south turn as it goes forward, until it ends up moving more or less parallel to the equator. (That’s the reason water draining from a bowl always spins in the same direction as long as you’re on the same side of the equator.) As a result, instead of having winds blowing north at high altitudes and south at ground level, in the temperate part of the northern hemisphere we have the westerlies blowing at high altitudes, and the easterlies, or trade winds, blowing at sea level. Those trade winds made it possible for ships to sail across the great bodies of water separating the land masses, allowing trade and encouraging the spread of cultures and ideas (for good or bad).

One note: The 40th Parallel lyrics only refer to the 40th parallel in the northern hemisphere: “far above the Earth’s equator.” What about the southern 40th parallel? As it turns out, most of the land mass of our world lies in the northern hemisphere. Only a tiny amount of land lies along the southern 40th parallel (at least compared to the northern 40th parallel). As a result, the climate and wind conditions there don’t seem to have borne the same fruit seen in the northern temperate zone. I mean no insult to our friends to the south!