Physics is Wild
A popular belief that has been around for many centuries is the theory that the Earth is not spherical, but rather a flat disk. The Flat Earth Society first formed in 1965 and created a platform with three main beliefs: the Earth is disk-shaped, the Earth is stationary and does not accelerate, and gravity is nonexistent and things simply fall (The Flat Earth Society). The Flat Earth Society’s belief that the Earth is shaped like a disk rather than a sphere is completely incorrect and is disproved with countless pieces of evidence. The topics of universal gravitation and attraction, the laws of rotational motion, and electricity and magnetism verify that the Earth is spherical rather than a disk.
The laws of universal gravitation and attraction are two of the most important concepts in physics and can ultimately be used to prove the falsity of the Flat Earth Theory. While the concept of gravity is widely accepted throughout society and the science community, there are generally two beliefs about gravity the Flat Earthers possess: it is a made up concept and objects simply fall or gravity does exist and its vector points outward from the center of the Earth, similar to physicist current knowledge of how gravity works. The laws of attraction between objects on Earth disproves the first Flat Earther belief about gravity being nonexistent. The Henry Cavendish experiment verifies the existence of an attractive force and provides scientists with the gravitational constant G, 6.67*〖10〗^(-7) N*m^2/(kg^2 ). In Cavendish’s experiment, two spheres were attached to a hanging horizontal rod while a third sphere was brought near to one of the hanging spheres, causing it to move (Figure 1-1). The string suspending the rod twisted as a result of gravitational attraction between the two spheres and with the use of a beam of light, a mirror, and a scale, Cavendish was able to prove the existence of gravitational attraction and determine the gravitational constant (Harvard). If a gravitational force did not exist, the Cavendish experiment would have failed. The other Flat Earth Society view about gravity is similar to scientists’ current observations of the force, as it is known that gravity’s vector is directed outward from the center of the Earth. While this works for the spherical model because everything on the surface of the Earth follows the direction of the gravitational vector, the disk shape model of the Earth does not follow this pattern. On the Flat Earth model, everything and everyone lies perpendicular to the horizontal axis of the Earth, not in the same direction of the gravity vector. In this case, the force of gravity would seem normal in the middle and on the sides of the disk, but would occur at varying angles in other regions, dependent on location. All of the Earth’s water would pull towards the center of the disk and turn the edges of the Earth into a desert. Plants and trees would grow at angles because they develop in the direction which opposes gravity. Gravity would cause everywhere on the Earth to be uninhabitable except for the center and sides of the disk, where humans would already be unable to live due to flooding or desert like conditions.
The laws of rotational motion deal with torque, centripetal acceleration, and angular kinematics. While they are prevalent throughout daily life, they can be applied to larger systems such as the Earth to demonstrate how the Earth revolves and most importantly, why it is impossible for the Earth to be shaped like a disk. Inertia, high tangential velocity, and the gravitational attraction between the Earth and the sun results in the Earth’s orbit and revolution. In the Flat Earth model, the sun lies above the face of the disk rather than at a distant angle. Rather than sunrises and sunsets being caused by the Earth’s rotation and orbit around the sun, the Flat Earthers believe the sun simply lights areas of the Earth in sections. However, the sun is a continuously burning ball of hydrogen and helium, making it impossible for sections of a disk-shaped Earth to be lit individually. Another popular belief from the Flat Earth Society is that the Earth has no velocity and remains stationary in space. However, a stationary Earth means there is zero perpendicular momentum or tangential velocity, which would result in a collision between the Earth and the Sun due to universal gravitation (Eq 2-1). If a disk shaped Earth did exist, then it would have to rotate in order to maintain distance from the sun. However, a disk shaped Earth would have a moment of inertia of 2.34 * 1038 kg*m2 (Eq 2-2) whereas a spherical shaped Earth would have a moment of inertia of 9.7 * 1037 kg*m2 (Eq 2-3). As the moment of inertia changes, the angular velocity and the radial acceleration will be affected and the Earth would rotate at a higher velocity. If the Earth were to rotate with such a difference in velocity, disasters such as higher water levels, stronger and more frequent earthquakes, and violent volcanic eruptions would immediately occur (Nave).
Electricity and magnetism play an important role in the lives of many people. However, if the Earth were disk-shaped as the Flat Earthers believe, electricity and large-scale magnetism would cease to exist. Magnets have two poles where the magnetic effect is strongest, one pole of the magnet always pointing North. The Earth’s magnetic field is produced by electric currents in Earth’s outer core, which is formed by molten iron (Figure 3-1). In an experiment by Hans Christian Oersted, a compass needle was placed near a straight section of current carrying wire. When the wire had a force applied to it, the compass needle aligned tangent to a circle around the wire, proving that magnetic fields are produced in the shape of a circle when a current carrying wire is placed at the center, similar to the spherical model of the Earth. A natural phenomena known as the Aurora Borealis or the Northern Lights confirm the validity of the spherical Earth model and demonstrates how electricity and magnetism affect the Earth. The Aurora Borealis is formed as charged ions move towards the Earth from the sun and enter the atmosphere around the upper and bottom poles. The velocity component in the x-direction relative to the field for each particle forms a circular orbit around the magnetic field lines while the velocity component, which is in the y-direction relative to the magnetic field, carries the particles along field lines toward the poles. As the particles approach the northern pole, the strength of the magnetic field becomes stronger and the radius of the circular path of the particles decreases. The high-speed particles ionize the atmosphere, forcing the electrons to recombine with atoms, which then emit light, leading to the creation of the Northern Lights (Giancoli). If the Earth were flat, there would be no evidence of the Northern Lights.
The Flat Earth Society’s beliefs about a disk shaped Earth have been and will continued to be disproved by the laws of physics. The laws of universal gravitation and attraction, the laws of rotational motion, and the topics of electricity and magnetism confirm knowledge of a spherical shaped Earth. The laws of universal gravitation and attraction are two of the most important concepts used to explain ideas such as how gravity and the normal force work and why the Earth, sun, and moon do not crash into each other. When applied to largescale systems, the laws of rotational motion can be used to explain how the Earth rotates and what would happen if the shape of the Earth changed or completely stopped rotating, as the Flat Earthers believe. The concepts of electricity and magnetism also prove the irrelevancy of the Flat Earth Theory as neither would exist if the Earth were in the shape of a sphere.