1.2 Definition and significance of networks

The following came from the online course of INFO 606 at Indiana University taught by Professor Yong-Yoel (“YY”) Ahn.

1.2.1 What is a network

A network is a system of elements that are connected. Those elements are called nodes or vertices, and the connections are called links or edges. Network science is all about connections.

There are two things that we care about in connections in a network: structure, and dynamics. Structure and dynamics might affect each other. Professor YY took Facebook activity as an example. Interpersonal interactions on and through facebook are governed by the structure of your friends you have on FB; On the other hand, if someone keeps posting things that iritate you, you might unfriend him or her, which will alter the structure of your online friends network.

I thought about international relationships. Relationships between countries vary: some are strong while others are weak. These structures definitely have an effect on the things going on between countries. Then, if a country does something that make another country, or other countries angry, for example, initiating a war, the original structure might witness drastic changes.

1.2.2 Why should we care about networks? Understanding individual elements is far from enough.

Knowing about each neuron in a person’s brain cannot gaurantee you can understand how a brain functions, or even rebuild a brain. To do these, we need to how elements interact. Networks are everywhere.

Human body, Internet, electricity, food, forest, the universe, etc., all have networks in them.

Networks are omnipresent. Some networks are waiting for discovery and finding a new network itself can be a contribution. For example, professor YY and his colleagues found this flavor network.

Also, the fact that networks are everything mean they have huge influence on our lives. A prime example would be pandemics. A contagious disease won’t stay locally anymore, thanks to the advancing global air transportation. The Coronavirus Disease 2019 (COVID-19) was first found in China and in only several months, it became a nightmare for every country in the world. Networks let us make fun analogies.

Network thinking: everything is a system consisting of many individual elements that are connected and interact.

This thought help scientists make analogies and new discoveries. For example, in the 19th centuary, it led to probabilistic and statistical thinking.

Professor YY gave an example of this own. He was studying how hastags spread on Twitter. The goal was to predic viral hastags. Later, some other scientists applied this finding to human brain and published this paper.

1.2.3 Think for yourself

Can you give an example of a network in your life?