Air is all around us. Although it looks invisible, the air has massive consequences on all living beings and the planet’s climate. Air is made up of various gases, where the most abundant ones are oxygen, carbon dioxide, and nitrogen. You would think that oxygen is the most abundant gas in the air, but it is nitrogen. This is because it is for more biological processes than oxygen.
The changes in temperature drive evaporation from the oceans. At the same time, the change in temperature because of the sun creates warm air and cold air. This happens because the Sun heats the ground. The air close to the ground ends up heating too, which changes its properties. Physics rules apply here and imply that cold air shrinks in volume and tends to become heavier as it contracts, this is stary close to the ground. Warm air expands; thus it has a lighter concentration. This drives warm air to lift. Think of hot air balloons, this is the principle of how they fly up. When warm air lifts, then cold air comes in to replace it. This flow of air creates wind.
Flight is an interesting application of the properties of air. Flight is a manipulation of 4 forces: drag, lift, thrust, and Newton’s third law. Drag is the force pushing a flying object against the wind. Think of trying to walk against the wind. You feel a force that will pull you backward. Drag is the resistance from the flow of air. Thrust is the force used to counter drag. Thrust is the force of the plane engines pushing it forward. Lift is the force generated to keep a plane up. It is affected by the angle of the wings. The change of angle changes the direction that air particles hit the wings. When these hit the wings, they create a small momentum on the way up. This momentum is counteracted by an opposing force on the way down, from Newton’s third law. The idea of flight is that there needs to be higher thrust than drag and lift needs to be stronger than the opposing force of Newton. This way we create a net positive of forces that keep the plane afloat in the air.
The same principles apply when flying in space. The difference is that after some point, there is no more air, so there is no drag force. Therefore, satellites flying in space do not have large engines to push them around.
The last point to touch on air is pollution, which is the change in on-air composition. This happens by the increase in carbon dioxide and the deposit of other gases into the atmosphere that are related to human manufacturing activity or from the combustion of oil.