Gravity is said to be the force that holds the universe together, but without electromagnetism there would be little of note to hold together.

Electromagnetism is one of the four fundamental forces, along with gravity and the strong and weak nuclear forces that are responsible for all interactions in our universe.

We are all familiar with the common effects of magnetism in the compass and holding souvenirs to the fridge, and with electricity as static cling in the clothes dryer. Of course, we use controlled electricity every day to power everything from household lighting and appliances to battery-powered cellphones.

In 1865 Scottish physicist James Clerk Maxwell summarized the known properties of electricity and magnetism and came to the startling conclusion that they are different aspects of the same phenomenon. His equations predicted that electromagnetic energy could propagate through empty space at the speed of light. In 1886 Heinrich Hertz generated and detected electromagnetic waves and later showed that they propagated at the speed of light as Maxwell thought.

Quantum mechanics now recognizes that electromagnetic forces are transmitted in packets of energy called photons. We see photons of certain energy as light, but their true importance is in atomic processes.

Atoms comprise a positively charged nucleus surrounded by a cloud of negatively charged electrons like fruit flies around a mango. In comparative size, fruit flies would be in the most distant row of the largest stadium flying around a mango seed on the 50-yard line.

In classical terms we say the electron is attracted to the distant nucleus by opposite charges. In quantum terms the moving electrons exchange photons with the nucleus much as basketball players exchange the basketball as they move around the court. This exchange of photons provides the attractive forces between nucleus and electrons and allows atoms of various elements to exist.

Without photons and the electromagnetic force, there would be no atoms and no matter as we know it.

The electromagnetic forces also allow atoms to stick together to form molecules. Atoms form molecules by electric interactions with other atoms. These interactions do not involve the nucleus, but rather electrons in the so-called, but misnamed, “valence shells” of atoms.

Forming chemical compounds requires atoms to interact with one another by transferring electrons. In order for electrons to move from one atom to another, the two atoms must exchange photons. These electromagnetic interactions are responsible for nearly all chemicals on Earth, as well as molecular bonds in our bodies. In other words, light holds molecules together.

Because of electron repulsion, it is impossible for two objects to touch. Electrons in the two objects prevent them from coming together. The distance between may be small on the macro scale; on the atomic scale it is the electromagnetic force that keeps you from falling through the floor.

The repulsion of a relatively few atoms in you and the floor is enough to overcome the gravitational force of the entire Earth. Electromagnetism is stronger than gravity by 42 orders of magnitude. Without electromagnetism the universe would be nothing more than a sea of fundamental particles.

Richard Brill is a professor of science at Honolulu Community College. His column runs of the first and third Friday of the month. Email questions and comments to brill@hawaii.edu.