The word “interactions” suggests multiple bodies or entities that “interact” with each other to produce some meaningful result. Two people conversing constitute an interaction. Three vehicles approaching a traffic junction, along with a pedestrian who is trying to cross the road at the same time, is an interaction. Five speakers in a panel discussion interact with each other. 193 countries in the United Nations interact with one another or within smaller groups, such as the Security Council, within the larger body. No man is an island. Similarly, the civilised world has a societal structure arising from interactions among people, organisations, and entities of various types. Accordingly, the study of the social sciences has become the central discipline engaging the interest of academics, the intelligentsia, and, indeed, any concerned, thinking person in the modern world.
Sociological affairs may be broadly defined as interactions that constitute systems. These systems may be simple or complex. In a simple system, interactions are few in number and—in relation to the context—strong. My first example, namely the case of two people talking to each other with no one else present, is a strong interaction. Each person is talking only to the other person. No third person is around to even listen to the conversation. An analogy from the world of chemistry is pertinent: two atoms of hydrogen, H, form a strong bond, H–H, to form a molecule H2, that can float around freely for the most part without let or hindrance from anything else, including other molecules of H2 that may be present in a metal cylinder where H2 gas is stored under high pressure. The H2 molecule is a stable entity, and it is difficult to break it back into two hydrogen atoms.
Hydrogen is important in chemistry because it is an essential constituent of the hydrogen bond. Let us start with a molecule of water, H2O, or H–O–H, which has two strong bonds between oxygen and hydrogen. When two water molecules come close together, they interact with one another, unlike two H2 molecules, which do not. This interaction may be represented as O–H…O–H, in which an atom of hydrogen in one water molecule interacts with an atom of oxygen in its neighbour. This hydrogen bond, represented by the dotted lines, is surprisingly strong. This hydrogen bond is why a pond of water does not completely freeze even when the surrounding temperature falls below 0℃. It is why it is easier to comb wet hair than dry hair. Hydrogen bonds in water are examples of a simple system.
As researchers looked more closely at hydrogen bonds, they found that certain interactions in carbon-containing molecules are of the type C–H…O–H. These interactions exhibited some features, but not all, of strong hydrogen bonds like O–H…O–H. They began calling these interactions weak hydrogen bonds to distinguish them from the strong hydrogen bonds found in water. Before long, they found larger systems of the type C–H…O–H…O–H where both strong and weak hydrogen bonds may be found within one system. These are examples of complex systems because they involve a combination of strong and weak interactions, like a conversation between two people, with a third person occasionally making just a comment or two. The conversation is mostly between the two main people, but the third person’s input is not zero.