Are you ready for spring? The calendar says it will start next Tuesday the twentieth. Now if the weather cooperates we will be in business!
The first day of spring, of course, coincides with the spring equinox, sometimes called the vernal equinox. As the name implies (“equi” equal, and “nox” night) the lengths of the nighttime and daytime on the equinox will be close to equal around the globe.
The spring equinox, along with the fall or autumnal equinox, marks the time of the year when the sun is directly overhead on the equator. But this is not for the whole day. It will occur on the twentieth at precisely 16:15 Universal Time (UTC) which is 10:15 am Central Time.
After the spring equinox, our days will lengthen until the summer solstice in June, marking the first day of summer. Then our days begin to shorten until the fall or autumnal equinox in September. The days continue to shorten until the first day of winter or winter solstice in December.
It is all because the earth does not spin on an axis that is perpendicular to the orbit. If that were the case, we wouldn’t have the seasons, and the sun would always be directly overhead of the equator. The earth’s angle of rotation is tilted 23.5 degrees off perpendicular. Have you ever wondered why?
Apparently, there has been a collision, or collisions. The leading hypothesis is that back after the Big Bang, when the planets in our solar system were forming, a lot of material would have been flying around. Some of that material coalesced to form the planets of our solar system. Larger masses would have produced greater gravitational attraction than smaller ones. It is hypothesized that at some point, there was a collision or perhaps many collisions involving the earth that knocked the earth off its axis. The distribution of the mass of the earth is also a factor. Based on what I have read, the earth is a little top heavy due to the polar ice. And it is not equally distributed up there.
So the earth is tilted and we have our four seasons. But what would life on earth be like if the tilt were 35 degrees? 45 degrees? It would be different. So maybe 23.5 degrees isn’t so bad.
“Happy Spring Equinox!”
Chuck Lura
Natural North Dakota is supported by NDSU Central Grasslands Research Extension Center and Dakota College at Bottineau, and by the members of Prairie Public. Thanks to Sunny 101.9 in Bottineau for their recording services.
