Facts of the Matter: Most electromagnetic waves are undetectable to humans

We are immersed in a dense sea of electromagnetism, or EM.

Every day, we are bombarded by the entire range of the spectrum of EM waves, from the longest radio waves to the shortest and most energetic gamma photons. The vast majority of it is as undetectable to our naked senses as water is to a fish.

Much of this EM radiation is man-made in the form of radio and microwaves. The form that we are most familiar with is that of the visible light spectrum ranging from energetic blue to less energetic red light.

Visible light is only a small portion of the EM spectrum.

The connection between electricity and magnetism was discovered by accident. In 1820, Hans Christian Oersted planned to demonstrate the heating of a wire by an electric current, and also to give demonstrations of magnetism, for which he had a compass needle mounted on a wooden stand.

He noticed that whenever the current was switched on in the wire, the compass needle moved.

Michael Faraday, a brilliant English scientist, was part of this effort, and in 1821 put it to work to invent EM rotation, the principle behind the electric motor.

Faraday was working on a number of other projects, and it was 10 years before he could return to the study of electricity and magnetism.

In 1831 he discovered that the magnetism generated by a coil of wire could generate an electric current in another coil, thereby building the first electrical transformer.

A few months later he rotated a copper disc between the poles of a horseshoe magnet to generate a continuous direct current. This was the first generator.

He had discovered that a changing electric field induces a magnetic field, and a changing magnetic field induces an electric field.

Faraday’s work captured the attention of James Clerk Maxwell, a Scottish theoretical physicist.

In 1873, Maxwell published “Treatise on Electricity and Magnetism,” in which he summarized and synthesized the discoveries of Coloumb, Oersted, Ampere, Faraday and others in four equations that are used today as the basis of EM theory.

Upon solving the equations, his calculations showed that the mutual induction would have the form of undulations and could sustain itself only if it moved at the speed of light.

In the following decade Heinrich Hertz generated and detected EM waves, which led ultimately to the generation, transmission and proliferation of radio waves.

Cellphones, Bluetooth, Wi-Fi and broadcast media use radio waves. The James Webb Space Telescope collects infrared light from galaxies billions of light-years away. IR is also used in remote control devices.

Beyond visible light is the ultraviolet range. It is present in sunlight and is highly toxic to biological molecules such as DNA. It is responsible for sunburn and for disinfectant. Much of it is filtered by ozone in the upper atmosphere.

X-rays have too many uses to list here. Most familiar are medical pictures and security scanners at the airport. X-rays are emitted by certain stellar objects and are studied with X-ray telescopes.

Gamma radiation consists of deadly high-energy photons emitted by neutron stars, black holes and nuclear explosions.

If we could see the entire EM spectrum as we see light, the world around us would be ablaze in a glow of white, and we would see everything and nothing.

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