‘Radiation” is a scary word to some people, and justifiably so. We have read of the horrors of radiation poisoning, the widespread effects of spilled radiation from nuclear reactors, and radiation burns.

We tend to fear anything with the word “nuclear” in it because of the potential damage to the environment from nuclear accidents and spills.

At the same time, there are the lifesaving benefits of radiation treatment by X-rays and proton bombardment for treating cancer, as well as the diagnostic use of X-rays to see inside the human body.

To name all of the uses and benefits of various kinds of radiation would produce a very long list. That list is so long because of the ubiquitous presence of radiation in our lives.

It surrounds us at all times. We live in a sea of electromagnetic radiation from the sun and from our myriad radio waves from which our radio is capable of isolating a single frequency with very high precision.

There are fundamentally two kinds of radiation, nuclear and electromagnetic. One form of nuclear radiation, gamma, is electromagnetic. Two others, alpha and beta, are particles ejected as atoms split in nuclear fission or combine in nuclear fusion.

Alpha particles are big, heavy particles composed of two protons and two neutrons. They are relatively low energy and have little penetrating power.

Beta particles are tiny, lightweight electrons. Each electron is 1,800 times lighter in weight than the proton or neutron, making each alpha particle 7,000 times heavier than the beta particle.

Radioactive isotopes produce a unique spectrum of particles and gamma radiation. Identification of these isotopes depends on the uniqueness and consistency of these products of radioactive decay for a given isotope.

Cosmic rays are mostly alpha particles of exceedingly high energy traveling at near the speed of light. They come from all directions from unknown sources, although astronomers now think they come from supernovas.

Almost all radioactive decay produces gamma, which is in the upper-energy, shortest-wavelength and highest-frequency range of the electromagnetic spectrum.

The EM spectrum is an unbroken continuum. It ranges from the longest radio waves with wavelengths measured in miles to the shortest gamma radiation with wavelengths measured in fractions of atomic diameters.

The EM spectrum exists in nature throughout the continuum, but we humans have learned to use it as well. We have classified various regions and designated boundaries of the EM spectrum according to the way we create them artificially, except for the visible part, for the boundaries mark the region to which our eyes are sensitive.

As we move through the spectrum from radio, the wavelengths get shorter while the frequency and energy get higher. Next are microwaves, followed by infrared, visible (shortened to VIS), ultraviolet, X-ray and gamma.

EM radiation is mostly harmless in the low-energy radio part of the spectrum, but microwaves and IR can cause thermal burns; intense VIS can damage the retina; UV causes sunburn but does not penetrate deeply into the skin; and X-rays and gamma are high enough energy to penetrate the human body and cause internal damage.

Most radiation is not harmful; in fact, most of it is useful. People discover new uses and new methods every day for use in health, industry, business, entertainment and scientific research.

Richard Brill is a 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.