I published the following column in the 14 November issue of the Deseret News:

As we in the United States approach the national Thanksgiving holiday for 2019, it's appropriate to consider things for which we should express our gratitude. Obviously, of course, there's the good food that many of us will be eating. There are the family members with whom many of us will be gathering to share it.

However, there is much, much more. Indeed, our reasons for gratitude are virtually infinite. Here, let me suggest one vital factor in our lives that we almost always take for granted:

The phrase "thin blue line" is sometimes used to refer to the role of the police in society, who hold chaos at bay and thus permit order and civilization to flourish. The term could perhaps be used even more appropriately to describe the function of our terrestrial atmosphere, which allows not only civilization and order but sheer physical survival.

Our atmosphere as it exists today derives (as our oceans also do) from the "degassing" of the primitive semi-molten earth, supplemented by later additions belched up from volcanoes and emitted by hot springs.

The atmosphere of early geologic times was composed of such gases as hydrogen, nitrogen, carbon monoxide, carbon dioxide, water vapor and various forms of hydrogen chloride. We couldn't have survived those conditions. However, the lighter gases (e.g., hydrogen and helium) escaped toward space. Five hundred miles above the Earth, our "atmosphere," if it can still be called that, is composed of 50% helium and 50% hydrogen.

Somewhat later in our planet's history, living organisms developed that were capable of photosynthesis. They provided the oxygen that then permitted animal respiration and eventually the colonization of land, as well as providing the famous ozone layer that shields Earth (and us) from the sun's ultraviolet radiation.

Evidence for this sequence of atmospheric development can be found, to some degree at least, in Precambrian rocks and a few fossils, which show a transition from a largely oxygen-free environment to what we might term a free-oxygen environment.

Our terrestrial atmosphere is an exceedingly thin envelope surrounding Earth. Perhaps somewhat more than 99% of our planet's air exists within a region no higher than approximately 18 miles above sea level. Earth's radius -- the distance from its center to its surface or circumference -- somewhat less than 4,000 miles, which means that the thickness of that oxygenated region of our atmosphere is a bit less than 0.5% of Earth's radius.

But oxygen isn't evenly distributed even within that thin envelope. Denser and, thus, heavier gases such as oxygen, carbon dioxide, nitrogen and water vapor hang low in the current atmosphere, mostly within about 3 miles of the planet's surface. That thin band is equivalent to approximately 0.00075 of Earth's radius, well under one ten-thousandth. Its outer edge is not far above our heads.

I followed those thoughts up on 28 November 2019 with the column immediately below: