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# Points of Origin

Media Type:
Video

Running Time: 1m 52s
Size: 5.5 MB

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Source: Quantus

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This animation from KET illustrates how an origin is used for positive and negative measurement along a straight line and on a flat plane. It also shows how an origin, latitude, and longitude identify locations on Earth and explores how measuring temperature differs from measuring height or weight.

Background Essay

Origin is a mathematical construct used to find an exact location or measurement along a line, on a flat plane, or in three-dimensional space. Identifying an origin, the point from which measurements originate, gives us a common frame of reference to describe a location or measurement.

Temperature scales provide a practical application of the concept of origins. The Fahrenheit and Celsius scales assign arbitrary numbers to the temperatures of certain natural phenomena such as the freezing or boiling point of water. On the Fahrenheit scale, the temperature at which water freezes is +32º. So 0º, the origin of this measurement, is very cold. On the Celsius scale, the freezing point of water is 0º, and +32º is quite warm. Both Fahrenheit and Celsius are relative scales, but because we understand their designated origins, they offer useful and reliable information.

On the Kelvin scale used by scientists, temperature measurement has a set origin, not a designated one. Absolute zero (0ºK) describes the point at which objects have the least amount of energy possible. Absolute zero is -273.15º Celsius and -459.67º Fahrenheit.

The system used to describe locations on Earth provides another example of how origins provide a common frame of reference. Think of the Earth as an enormous orange with 360 equal sections. The dividing lines between the sections are the meridians, which run between the North and South Poles. You can also think of meridians as halves of great circles encompassing the globe. These lines were arbitrarily established so we can determine longitude, a point’s east-west measurement.

The "prime meridian," which passes through Greenwich, England, has been designated as 0º longitude. Longitudes are designated as E or W, that is, east or west of the prime meridian. The end line for measuring east and west longitudes is the other half of the prime meridian, the 180º line on the opposite side of the Earth.

If you drew a circle around your orange halfway between its top and bottom, this circle would correspond to Earth’s equator. Unlike the prime meridian, the equator has a fixed location. For measurement purposes, the equator has been designated 0º latitude.

Above and below the equator are the latitude lines, called parallels because these concentric circles are parallel to the equator. Parallels help determine a point’s latitude, or location along a north-south line. Latitudes north of the equator are labeled N; latitudes south of the equator are labeled S.

This complex system for finding locations on the Earth works because we all have agreed to accept the equator and the prime meridian as the origins for our measurements.

To learn more about numerical values, check out Importance of the Origin, Two Points Determine a Line, and Finding the Intersection.

Discussion Questions

• Define what is meant by the term "origin."
• Think of using a stopwatch to time a race: explain what we mean by "origin" in this situation.
• The Kelvin temperature scale has a set origin. What are some other measurements whose origins are set rather than designated?
• Look up the longitude and latitude of a particular location (your home town, a favorite place, a place that interests you).
• What do these measurements reveal about the location’s relationship to the equator and the prime meridian?

Standards

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