Oxygen and nitrogen are two of a handful of elemental superstars of life. Without them, life would not be possible. In some ways, these two elements are very similar, but they are also very different.
Oxygen and nitrogen atoms differ in only one proton and one electron. In chemical reactions, the important subatomic particle is the electron, and oxygen has eight while nitrogen has seven. In the last two days, we talked about the difference that one electron makes. Oxygen and nitrogen make up about 99% of our atmosphere, with nitrogen composing nearly three-quarters of our air. So why is nitrogen’s percentage so high compared to oxygen?
As we said previously, the triple bond of a nitrogen molecule requires more than twice as much energy to break as the double bond of an oxygen molecule. The oxygen bond can be broken to allow combustion oxidation and energize our bodies. On the other hand, the nitrogen bond is not easy to break, but plants require nitrogen for photosynthesis and growth. What is the solution?
Lightning breaks the nitrogen bond allowing rain to wash nitrogen to the ground. Plants such as beans, peas, and alfalfa, which we call legumes, have microorganisms on their roots that extract nitrogen from the air. That enriches the soil with nitrogen while providing for the legumes. More than a century ago, scientists found a way to extract nitrogen from the air to produce ammonia. That process enabled fertilizer production, which today allows farmers to produce enough food for the world’s population.
It is not easy to break the nitrogen bond so it can combine with other elements, but with 78% of the atmosphere being nitrogen, there is no shortage. So why is our atmosphere mostly nitrogen? Since it is only about 21% oxygen, wouldn’t it be better to have more oxygen so we could breathe easier? The answer is that nitrogen stability is essential for our safety. Wildfires have been a significant problem in recent years. If the atmosphere consisted of a very high percentage of oxygen, fires would be more common and dangerous. If the atmosphere consisted of 100% oxygen, all it would take is one lightning strike to set the whole planet on fire.
Remarkably, we have the correct percentage of elements in our atmosphere. We have the right amount of oxygen to allow respiration to power our bodies and combustion to power our vehicles and industry and heat our homes. At the same time, we have the right amount of nitrogen to prevent uncontrolled combustion leading to the destruction of life. We have just a small amount of carbon dioxide, which plants need for photosynthesis. Plants use CO2 and generate oxygen to keep the gases in balance. The balance is amazingly precise as long as humans don’t generate enough carbon dioxide to mess it up.
During the dinosaur age, the oxygen level was higher, on the order of around one-third of the atmosphere. That allowed the enormous animals to prepare the Earth for humans. Now we have the precise balance to sustain human life and advanced society. The question is, did the features of oxygen and nitrogen and the balance between them happen by accident, or was it part of an intelligent plan? We think the best explanation is that an intelligent Planner of life created it.
Nitrogen and oxygen together make up about 99% of the air we breathe. The vast majority of our atmosphere is nitrogen. Oxygen is ten times as abundant as nitrogen in the universe, but it makes up only about 21 percent of our atmosphere. So, the less common element is the most abundant in our atmosphere. What does that mean to us? The bottom line is that the atmosphere is fine-tuned for life. Let’s examine that more carefully.
An atom of oxygen and an atom of nitrogen differ by only one proton and one electron. That may not seem like much, but it makes a world of difference. Both of those elements form diatomic molecules, meaning that two atoms bond together to make one molecule of oxygen or nitrogen.
Covalent bonding is the chemical bonding of atoms by equal sharing of electrons. Thatbond gives atoms stability in their outer, or valence, electron shells. Atomic stability requires eight valence electrons. The only elements with that number are the so-called “noble gases”–helium, neon, argon, krypton, and radon. For that reason, they are inert, refusing to combine with other elements. All other elements need electrons to complete the octet in their valence shells.
An oxygen atom has six electrons in its valence shell, so it needs to share two electrons to become stable. When an oxygen atom shares two electrons with another oxygen atom, they both become stable. Nitrogen, on the other hand, has only five valence electrons. Therefore, by forming a covalent bond with another nitrogen atom, sharing three electrons, both atoms complete their outer shell. In this way, our atmosphere is made up of stable diatomic oxygen and nitrogen molecules.
However, not all molecules are equally stable. That is where we see the atmosphere is fine-tuned for life. For example, oxygen molecules have a double bond sharing two electrons, but nitrogen atoms have a triple bond sharing three electrons for more stability. That difference may seem insignificant, but it is essential to make life possible. Come back tomorrow when we will explain what a difference it makes.
The atmospheric oxygen level in Earth’s early history allowed life-forms to grow much larger than they do today. We find fossil remains of insects that grew to incredible sizes. There are wonderfully preserved fossils of a dragonfly called Meganeura which was the size of a modern-day hawk. Ants a foot (30 cm) long and centipedes that were as long as two feet (61 cm) show up in the fossil record. There are also fossils of mammals that were larger than any land mammals living today.
A major key to the huge sizes is the amount of oxygen in the atmosphere at the time those animals lived. New laboratory techniques in nuclear chemistry give us accurate methods of determining the oxygen level of the atmosphere in the past. Ice cores and tree rings confirm the measurements. Studies show that Earth’s atmosphere has had oxygen content as high as 35 percent in the past compared to 21 percent today. This higher oxygen level would have some negative consequences, with fires burning much hotter and faster and corrosion happening faster. Its effect on some living things, however, would be very positive.
Laboratory experiments have also shown us how oxygen content affects the size of living things. Insects do not breathe with lungs since oxygen diffuses into their bloodstream directly. Dr. Robert Berner at Yale has shown that a 35 percent level of oxygen in the atmosphere would increase the diffusion rate of oxygen in an insect’s bloodstream by as much as 67 percent. Body size varies directly with oxygen concentration, and experiments with fruit flies and mealworms consistently show high growth rates with increased oxygen. Studies done on alligators have shown that variations in egg development and growth are in direct proportion to the oxygen in the atmosphere. It is the same for mammals. Dr. Paul Falkowski of Rutgers has said, “Pound for pound, mammals typically need three times as much oxygen as reptiles do.” An oxygen level that would support reptiles might not support mammals.
All of this is very helpful in understanding a variety of issues relating to the Bible and the evolution/creation controversy. It is increasingly obvious that dinosaurs and humans could not survive together on this planet. At the time of the dinosaurs, the oxygen level was too low for mammals to survive. Competition for food and living space between humans and dinosaurs would be most difficult. Domestication of reptiles is impossible so humans would not be able to train dinosaurs to help with heavy chores.
The Bible does not mention dinosaurs, and no Hebrew word in Genesis 1 could legitimately be interpreted to mean dinosaurs. The emphasis that the Bible gives to the breath of living things as seen in the Hebrew word “nephesh” becomes more and more relevant as we learn more about how vital that concept of breath is. (See Genesis 2:7; 7:22, etc.)
Many people seem to feel that dinosaurs were unnecessary to human existence and that their presence denigrates evidence of God’s creation. The balance between the composition of the atmosphere and the abundance of life on Earth is critical. For plants to grow, there has to be soil, and soil is not as simple as it looks. Dirt must have the critical elements for food chains and cell reproduction. The production of all of those resources is not simple. As plants take in carbon dioxide and lock carbon into the soil, they release oxygen into the atmosphere. The ecological system of the planet at the time when the dinosaurs lived allowed not only the formation of soil but also the massive amounts of coal and fossil fuels we need.