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• 1 media/1690049.jpg 2020-07-21T13:06:39-07:00 Temporal Data Visualizations 22 Temporal data visualizations help us answer "when" questions. They allow us to visualize when events occurred and how they are temporally related to when other events occurred. They help us understand the sequence and duration of events, how events overlapped or were separated in time, and how things may have changed or remained continuous over time. plain 2020-09-08T10:52:46-07:00 Time is a mysterious and elusive concept. Time passes, and is gone. It moves quickly and slowly. We measure it by the movement of the Earth, the passing of sands through an hourglass, the steady shifting of gears, the frequency of microwaves, the decay of elements -- and by our own "sense." It is difficult to grasp, and therefore essential to visually display. 
  
  All temporal data visualizations serve one basic purpose — to show data over time. They allow us to visualize when events occurred and how they are temporally related to when other events occurred. They help us understand the sequence and duration of events, how events overlapped or were separated in time, and how things may have changed or remained continuous over time.
  
  Timelines are probably the most common type of temporal data visualization in social studies, particularly in history. While you might not typically think of timelines as a data visualizations, temporal points on a timeline are, in fact, data points. These data points provide more or less precise information about when and how long an event occurred, as well as information about the sequence with which multiple events occurred.
  
  But there are other temporal data visualizations we commonly use in social studies education as well. As you'll see along the right side of this page, there are various kinds of graphs and charts that show us patterns in data over time, helping us spot trends, anomalies, shifts, and periods of stability that give us insight into change and continuity — a fundamental aspect of historical thinking. 
  
  The following sections provide an overview of the different functions temporal data visualizations can serve. 
  
  Chronology
  All temporal data visualizations display chronology. They provide information about a sequence of historical events or other variables in the order by which they occurred. By layering data, they can also provide information about concurrence, or when events were happening at the same time. Units of time on a temporal data visualization can differ drastically, from seconds to millennia, and it's important to pay attention to timeframe over which events, quantities, and other data points are sequenced. Timelines are perhaps most readily associated with the function of chronology, but other temporal visualizations, which use time as a framework for other data, such as time series and line graphs, also display chronology.  In fact, as discussed in the section on misleading data visualizations, it would be a gross misrepresentation of data to organize points of time on a graph's axis out of chronological order. In modern society, most people take chronology -- factual information about when and in what sequence something occurred -- for granted. But, in fact, assembling chronologies has been and continues to be a challenging human endeavor. Just think about popular crime shows that revolve around detectives trying to figure who was where when, and doing what. Even trying to sequence events in our own lives can seem like a riddle.  Because time is such an amorphous concept, the way that people from modern Western cultures typically display a sequence of events in time, on a straight line, is not the only way to display chronology, and some of the primary source data visualizations you'll encounter on this website will demonstrate that point. Nonetheless, most temporal data visualizations social studies students will encounter represent chronology on a straight line, and all try to distill events or data within a temporal framework that can be readily displayed and easily perceived.  
  
  Duration
  Some spans of time can be nearly impossible to imagine. You can probably easily imagine a minute, a day, or even a  year, but not necessarily a century or millennium.  For children and adolescents, who have even less of a concrete frame of reference for time periods than adults, this can be particularly challenging. Temporal data visualizations can help us to visualize different spans of time, or durations. Timelines, for example, can help us imagine the nearly unimaginable periods of time we sometime deal with in social studies, typically by comparing them to durations that are easier to grasp. For example, it is easier to imagine how long a century is when we equate a year with a millimeter and juxtapose one millimeter (equaling one year) with 100 millimeters (equaling one century). Timelines accomplish this with design features like lines and bars to show duration, and line graphs and time series accomplish it through the choice of scale on an x-axis. Some timelines are are also scaled, with the distance between each tick mark representing a specific span of time. Other temporal data visualizations, like area graphs or line graphs can show us the duration of positive or negative trends. This can help us see anomalies in data, such as when a long upward trend in average life expectancy is punctuated by a brief dip, which may be caused by war, genocide, or epidemic. 
  
  Patterns of Change and Continuity
  History is a complex mix of change and continuity, not just a list of events. Temporal data visualizations can help students understand this fundamental concept of history by revealing patterns of change and continuity over time. This, in turn, can raise questions about another fundamental concept of history, causes and consequences: Why did things change the way that they did? What accounts for continuities I observe in the data? In the video on the left, the late Hans Rosling demonstrates this well by walking viewers through an example of the animated bubble maps featured on his website, Gapminder. Almost all temporal data visualizations reveal patterns of change and continuity. Even timelines can signal change by noting significant turning points in a national or regional history. However, it is also important to note that data visualizations that show change and continuity in one area, can mask change and continuity in other areas. For example, just because a country's Gross Domestic Product has been steadily increasing, that does not necessarily mean that standards of living have significantly changed for all segments of the country's population.