The seasons of Planet Earth sustain humanity in several ways, including supplying emotional needs. Seasonal changes are enjoyable to many Earth residents, especially those who choose to live in regions where changes are more pronounced. We revel in delightful seasonal variety.
Seasons are welcomed by some and scorned by others. For example, springtime is generally a time of enjoyment and optimism as is autumn. Complaints about oppressive summer heat or bitter winter cold tend to balance the ledger for some mid-latitude residents. Of course, every season possesses unique appeal. Although autumn is a time of astronomical decline and cessation of plant growth, most people enjoy the refreshment of slowly declining temperatures. In select geographic regions autumn is graced by splashes of color around the countryside. Fall hues enhance decorations for parties and social gatherings. Harvest of pumpkins, gourds, Indian corn, vegetables, fruits, and grains communicate a reality statement: Summer is over; harvest has arrived. It is a time for joy and thanksgiving.
During autumn, the weather shifts slowly from summer heat to winter cold. In extreme northwest Illinois, the average daily high temperature declines from early July (82ºF) to early February (27ºF), a drop of 55º. Average daily low temperature declines a similar amount from the warmest to coldest months. Sunrise times slowly become earlier from December to June while sunset times slowly become later during that six month time frame. From June to December the situation is reversed. Sunrise times become later; sunset times become earlier. In December and June sunrise and sunset times change hardly at all for a few weeks. Hours of daylight slowly increase from winter to summer. From summer to winter hours of daylight slowly decrease. In northwest Illinois summer has 15 hours of daylight and 9 hours of darkness. In winter the situation reverses—we receive 9 hours of daylight and 15 hours of darkness. Sun rays strike Earth at a much lower angle in winter, spreading themselves out over a much greater land area. Therefore, we receive less heat. In summer, of course, we receive more heat because sun rays strike Earth more directly. In addition, northwest Illinois receives six more hours of intense sun rays.
We cited extreme northwest Illinois by way of illustration. At higher latitudes to the north seasonal effects are even more extreme. In mid-summer we recall walking on the streets of Fairbanks AK at 10:30 PM in daylight. At lower latitudes to our south the effects are less extreme. Near the equator the amount of daytime heat and length of daylight vs darkness is not very significant from one time of year to another compared with latitudes farther north or south. By coincidence, the five US locations where this blog author has lived were each located at approximately 41ºN latitude. Seasonal changes described in the above paragraph were embedded in personal experiences throughout my life. When our family visited Fairbanks AK in the summer or Aruba in the winter differences in the effects of seasons depending on latitude became apparent.
Thriving, healthy animal and plant populations and their unique adaptive behaviors depend in large part on Earth’s phenomenon of seasonal changes. If Earth were not tilted on its axis there would be no seasons. Our planet’s life forms, including human life, and their current population levels would be impossible to sustain. Environmental scientists have explained in detail why this would be true. In future posts we will deal more extensively with the beneficial consequences of our changing seasons.
We close with one well known example of the reward of seasonal changes. We are created with emotional and psychological needs and the means to satisfy them. Our Creator supplies the sensory and intellectual ability to identify wonders of nature and its design features. Many readers may remember our teachers and science texts touting the presence of chlorophyll, a green chemical pigment to aid plants in using the energy of sunlight to synthesize their own food from water and carbon dioxide. When the autumn season descends on our countryside, the reduced intensity of light is not sufficient for plants to continue to produce or retain green chlorophyll. As a result, many leaves lose their green color and display other colors formerly visually masked by the plentiful presence of chlorophyll. Eventually, the lifeless plant leaves drop away, giving up food synthesizing until new leaves are produced the following spring. Many motorists flock to regions where autumn leaf colors are most vivid.
Changing seasons supply multiple opportunities to discover wonder-producing processes of our environment. Together, awareness and intellectual understanding of these processes nourish our sense of wonder. God has given us “all things to enjoy” (1 Timothy 6:17).