Keith Morris,age 11, of Langley Air Force Base, Virginia, for his question:
Which kind of radiation is most deadly?
Our word "radius" is coined from an older word meaning one of the spokes in a wheel. Radius is related to radiator and radial, radiance and radio words that suggest the fanning out of rays or straight lines. The noun "radiation" covers a multitude of related meanings.
The radiation from a radiator is gentle warmth and radiation from a radio is fairly harmless electromagnetic energy. Ultraviolet and other dangerous radiation from the seething sun are filtered out by the earth's atmosphere. So is the more dangerous radiation of primary cosmic rays that continuously bombard our planet from outer space. The earth itself produces small doses of deadly radiation from uranium and other radioactive substances. Nature exposes us to a lot of radiations that are either beneficial, harmless or present in moderately safe doses.
However, with the Age of Science man released the energy of the atomic nucleus. The smidgeons of natural radioactive substances were amassed in large quantities and other man made radioactive materials were created. Nowadays we can release immense doses of deadly radiation from nuclear fission and nuclear fusion. These new skills can and will be used for the generation of electricity and other beneficial purposes. But nuclear power also is harnessed for warfare and its deadly radiations are cause for our most serious concern.
The emissions of radioactive substances have been well studied since the dis¬covery of radium at the turn of the century. Radium disintegrates by nuclear fission, the breaking apart of atomic nuclei into smaller atoms. In the nuclear fusion of a hydrogen bomb, small nuclei combine to form larger atoms. Both fission and fusion emit three types of radiation called alpha, beta and gamma rays. Their tremendous speeds give them the power to penetrate and damage living cells like minuscule bullets.
The mildest are alpha rays, streams of particles comparable to the nuclei of helium atoms. In a vacuum they may reach speeds of 10,000 miles per second but ordinary air slows them down rapidly. They rarely penetrate through the skin, and a thick sheet of paper stops them in their tracks. However, alpha radiation inside the body can damage living cells. Beta rays are electrons traveling fast enough to cross several yards of air and penetrate an inch or more into the body. They can be stopped by half an inch of wood or a metal shield 1/8th of an inch thick. Gamma rays are streams of electromagnetic energy emitted at almost the speed of light. Their wave lengths are 100 times shorter than the short wave lengths of X rays and their searing energy can penetrate the flesh and bones of the entire body. It takes a four inch shield of lead or two feet of concrete to stop them. All three types of nuclear radiation can be harmful to living cells. But beta rays are 100 times more deadly than alpha rays and the most deadly gamma rays are 100 times more destructive than beta rays.
A nuclear explosion produces fallout with other forms of radiation. Streams of nuclear particles and nuclear radiation devastate atoms of the earth's air and minerals, plant and animal tissues. These atoms become radioactive themselves, damaging other atoms in a chain reaction. The fallout may shed 200 of these deadly isotopes. Most of them disintegrate in a few weeks. One of the exceptions is strontium 90, which takes 23 years to lose half its ammunition. It lingers in air, water and food and its penetrating power is dangerous to all plant, animal and human life in the world.