Gravity vs. Magnetism — What's the Difference?

Gravity, a fundamental force, acts between all masses in the universe, dictating the motion of planets, stars, and galaxies, and influencing the structure of the cosmos itself. Its strength depends on the mass of the objects and the distance between them, following Newton's law of universal gravitation. Magnetism, on the other hand, arises from the motion of electric charges, affecting only materials sensitive to magnetic fields, such as iron, nickel, cobalt, and certain alloys. It plays a critical role in electrical and electronic devices, from simple compasses to advanced data storage systems.

Gravity is always attractive, pulling objects together, while magnetism can either attract or repel, depending on the orientation of the magnetic poles. This duality allows magnets to do work, like driving electric motors or levitating trains (maglev). Gravity’s influence is omnipresent but weak compared to electromagnetic forces, including magnetism, which is why we can use a small magnet to lift a paperclip against the entire Earth's gravitational pull.

The source of gravity is mass and energy, according to Einstein's theory of general relativity, which describes gravity not as a force in the traditional sense but as a curvature of spacetime caused by mass and energy. Magnetism, however, originates from the spin and orbital motion of electrons around an atom and the alignment of these elements in certain materials to create a magnetic field.

In terms of range, gravity has an infinite range, affecting objects across the vast expanse of the universe, whereas magnetism tends to have a more localized effect, with the strength of the magnetic force decreasing rapidly with distance from the source. Despite their differences, both forces are integral to the functioning of the universe and our daily lives. For instance, gravity is essential for keeping planets in orbit around the sun, while magnetism is key to the Earth's magnetic field, protecting us from solar radiation.

Applications of these forces vary widely. Gravity is crucial in astrophysics, planetary science, and for understanding the universe's large-scale structure. Magnetism finds its applications in technology, including electrical engineering, digital data storage (like hard drives), and medical devices (such as MRI machines).