Why Can't a Plane Fly Slowly and Let the Earth Pass Underneath?

The idea of a plane flying slowly while the Earth passes underneath it might seem intuitive at first, but there are several physical principles that explain why this is not feasible. Here are the key points:

Relative Motion

The Earth is rotating, but an airplane is not stationary relative to the Earth. The plane is moving through the air, which is also moving with the Earth's rotation. For example, at the equator, the Earth's surface moves at about 1670 kilometers per hour (1037 miles per hour) due to this rotation. This relative motion means that a plane's speed is measured relative to the air, not the ground. Thus, the plane must still attain a certain speed to counteract the Earth's rotation.

Aerodynamics

Airplanes generate lift by moving through the air. This lift is produced by the wings as they interact with the air. If a plane flies too slowly, it will fail to generate enough lift to stay airborne. There is a minimum speed known as the stall speed, below which an airplane cannot maintain flight. This stall speed is crucial for ensuring the plane can maintain lift and continue flying.

Ground Speed vs. Airspeed

An airplane's speed is measured in terms of airspeed, the speed relative to the surrounding air, rather than ground speed, the speed relative to the Earth's surface. If a plane were to fly at a speed equal to the Earth's rotational speed, it would still need to maintain sufficient airspeed to generate lift. This is because the plane must move through the air to create the necessary pressure differential for lift.

Wind Resistance

When flying slowly, the effects of drag (air resistance) become significant. An airplane needs to overcome drag to maintain flight. If the plane is flying slowly, it must exert more energy to counteract this drag. This can be inefficient and impractical for long-distance travel.

Flight Path

The plane must also consider its flight path in relation to air traffic, weather conditions, and navigational considerations. Simplicity is not a luxury in commercial aviation. Simply hovering in one spot relative to the Earth's surface is not a viable option, as it would disrupt air traffic and could cause significant safety and logistical issues.

Physics of Flight

The principles of flight are governed by Newton's laws of motion and Bernoulli's principle. An airplane must move through the air to create a pressure differential that results in lift. A stationary or very slow-moving plane would not be able to achieve this. The combination of these principles ensures that planes must achieve a certain speed to stay aloft. Slowing down is not an option in this dynamic environment.

In summary, while the Earth rotates underneath the plane, the plane must still achieve the necessary airspeed to generate lift and overcome drag. Thus, it cannot simply hover in place as the Earth rotates beneath it. This is a crucial aspect of aviation safety and efficiency.