SCIENCE IN ACTION
By MICHAEL JOHN UGLO
GOOD day everyone. Our sixth lecture in the Science in Action series is on the science topic of atmosphere, a branch of specific study in physics and technology. Our last lecture was on fluids. We can also relate fluids to the atmosphere in physics.
Atmosphere can mean many things in the use of the word in many circumstances. In the study of science, it comes to be known as the parcel of air surrounding the planet earth we live in. It is all the gases we need to live our lives together with the other living things like plants and animals as well as all tiny living things that we cannot see with our naked eyes. These are the smallest or microscopic plants and animals we call microbes. It is noteworthy that the corona virus comes in this category called microbes.
The composition of the air or so called the different kinds of gasses that are contained in our atmosphere are namely nitrogen (78 per cent), oxygen (21 per cent), hydrogen and and other gasses like argon (0.9 per cent), carbon dioxide (0.04 per cent), and other gases like water vapour, helium in lesser amounts.
The atmosphere shapes our landscapes which we call terrain. The winds that blow from these gases as a result of temperature differences become the erosive agents that shape our landscape. They erode craters created by meteors and volcanoes. They also form sand dunes. The atmosphere varies in temperature in the respective layers such as the troposphere which contains the majority of the gasses in the atmosphere. We have stratosphere after the troposphere followed by the mesosphere and then the thermosphere. After the thermosphere is the ionosphere. The region above the ionosphere is the magnetosphere.
Because about 97 per cent of the earth’s gasses are in the troposphere, all weather systems and climates are determined by the troposphere. Life on earth is determined by the atmospheric gasses and composition. That is, nitrogen is responsible to form ammonia which has the building block for nucleotides and nucleic acids that form all proteins in all living things. The ammonia is produced from lightning strikes as well as fixed by nitrogen fixation bacteria called rhizobium. They can be located at the root nodules or swellings of legume plants such as peas and peanuts.
The carbon dioxide is taken up by the green plants, cyanobacteria and phytoplankton (microscopic sea-surface-floating plants) combined with water and sunlight with the presence of chlorophyll to make plant food called glucose. This is a simple sugar which is a carbohydrate. The oxygen in the atmosphere is used by both plants for respiration or breathing. In plants, oxygen is used to derive energy during burning of sugar which is called anaerobic respiration which does not include oxygen while respiration involving oxygen is called aerobic respiration. Cellular respiration happens at the level of the cells to provide energy for the cells to carry out their normal life processes or more specifically biochemical and metabolic activities.
The atmosphere also in the very beginning formed the planets. The discs of atmospheric gases coalesced and generated enough gravity to form the planets as we know them today. These gases without adequate gravity will escape into space. The presence of water means that the gravity is sufficient to hold it together than to let it escape into space.
The gravity of the earth measures approximately 10 meters per second squared (10ms-2) as its acceleration at free fall. That means acceleration without the friction or resistive forces of the atmosphere. The escape velocity is the speed that any air molecule that acquires enough energy to escape into space. Lighter gases such as hydrogen and helium have higher velocities so they escape very easily. Heavier gases such as nitrogen are in our atmosphere because they have low velocities and do not reach the escape velocities.
The ultraviolet radiations from the sun together with the solar wind with cosmic radiations from the outer planets bombard many gas molecules and that gives more energy to escape into space. That is so with planets like Mars and Venus which do not have atmospheric gases like the earth’s. The planets Mars and Venus lost their water bodies when the high-powered radiations like ultraviolet and cosmic rays dissociate (photo-dissociate) water molecules into component hydrogen and oxygen which escape into space. The earth is also exposed to those harmful radiations, but its magnetic fields deflect those radiations therefore, letting all our gases in the atmosphere accumulate and support life on the planet earth.
This does not mean that the earth’s magnetic field doesnot let gases heat up and escape into space. Earth’s magnetic field also supports the heating and the escape rate into space. Atmospheric temperature decreases with increasing height above sea level called altitude.
The atmosphere pressure decreases as you go higher up in altitude because of the decreasing column of air above it. As one goes down in altitude, the atmospheric pressure increases also because of the larger column and volume of gases above it.
The exosphere is where there is no atmosphere because there is lower gravity and higher temperature that provides more energy for air particles to escape into space.
The atmosphere allows for the circulation of wind systems and precipitation. Along the equator and the tropical region, temperature is warmer than in the temperate zone.
Temperature in the temperate zone is warmer in comparison to the freezing polar temperature. This allows for the development of the wind cycles in the polar cycles, temperate cycles and the tropical cycles.
My prayer for PNG today is; “Come to Me, all who labour and are heavy burdened and I shall give you rest, take up my yoke and learn from me; yes my yoke is easy and my burden is light.”
Next week: Light and technology
- Michael John Uglo is the author of the science textbook “Science in PNG, Pacific, Asia & Caribbean” and a lecturer in Avionics, Auto- Piloting and Aircraft Engineering. Please send comments to: [email protected]