Scientists have discovered four fundamental forces of nature. These are gravitational, electromagnetic, weak and strong forces. All of these are connected to radiation in some way.
Gravitation
Gravitation is the least important for our discussion. Gravitation is a force that causes attraction between material objects. Although gravitation influences radiation on a cosmic scale, it is by far the weakest force of nature and is of little importance in our discussion of radiation and its dangers on a human scale.
Electromagnetism
The next force in terms of strength is the electromagnetic force. Early research on electricity found that there were two types that attracted and cancelled each other which we call positive and negative. Because of a mistake that Ben Franklin made, electrons are said to be positive and protons are said to be negative in charge. It would make a lot more sense to say that electrons had a positive charge but tradition dictates otherwise.
Electricity and magnetism were thought of as two separate forces but then it was discovered that magnetic fields are a manifestation of moving electrical charges. When electrons in orbit around atomic nuclei change energy levels, they either absorb or emit a packet of electromagnetic energy known as a photon. Photons have a frequency and a wavelength that are inversely related. As the frequency increases, the wavelength decreases. The amount of energy carried by a photon is directly related to the frequency of the photon and increases as the frequency increases. The electromagnetic spectrum extends from a frequency of a million cycles per second with a wavelength of a kilometer up to a frequency of ten followed by eighteen zeros per second and a wavelength of one ten billionths of a meter. Photons travel at one hundred and eighty six thousand miles per second in a vacuum but will move slower when passing though gases, liquids and solids.
Electromagnetic energy is present in many ways in our lives both naturally and artificially. Natural types of EM radiation include heat, visible light, ultraviolet light and highly energetic gamma rays. Artificial EM radiation includes all sorts of radio communication from AM radio to microwaves, lasers that utilize visible light for many things, ultraviolet light for many uses and X-rays to probe the interior of things. Many of the frequencies of EM radiation have biological effects, some benign and some harmful. Gamma rays are highly energetic photons that are released by radioactive decay and also generated by astrophysical processes which bombard the earth with these packets of energy. This type of EM radiation is harmful to living things.
Weak Force
The weak force is much weaker than both the electromagnetic and the strong force. This force holds an electron and a proton together to create a neutron. Electric charges come in two polar opposite types referred to a positive and a negative charge. When the weak force holds an electron and a proton together, the resulting particle is called a neutron because the two charge types cancel each other and the neutron is electrically neutral. When a neutron is expelled from a radioactive nucleus in what is called beta decay, it spontaneously splits into an electron and a proton in about 15 minutes. The weak force is also involved in thermonuclear fusion which takes place stars and results in the creation of all the elements in the periodic table from hydrogen atoms.
Strong Force
Like electrical charges repel each other. The protons in the nucleus of an atom carry a positive charge and so they are pushed apart by their charge. However, the strong force overcomes the repulsive EM force and holds the nucleus together. The strong force is about one hundred times stronger than the EM force at atomic distances. The strong force also binds together the particles called quarks to create protons and neutrons. The nuclear binding energy is a measure of the energy that is holding the nucleus together. Depending on the mass of the nucleus and the number of neutrons, the splitting of some nuclei in nuclear fission results in the release of nuclear binding energy which is the source of the heat used to generate power in a nuclear reactor or destructive force in a nuclear explosion.
