History of Measurement



History of Measurement8890050800Early Egyptians used balance scales like the one pictured above to measure mass.00Early Egyptians used balance scales like the one pictured above to measure mass.How far away is London? What is your mass? How tall is your best friend? Today, it is possible to quickly answer all these questions and many more because of precise and universal standards of measurement. We have standards for measuring length, area, mass, volume, temperature, and other variables. But centuries ago, there were few agreed-upon standards. How did they come about?Very early standards of measurement relied upon the width of the human palm, the length of the human foot, and the length from the elbow to the tip of the middle finger, which was called the cubit. Even today you can see people use these measurements as a quick way to determine distance. The disadvantage of this, of course, is that such measurements are imprecise. After all, palms, feet, and forearm length differ from person to person.As early as 3000 B.C. attempts were made to standardize the cubit. The Egyptian royal cubit came to be a length of approximately 52.3 cm, whereas the Sumerian was about 49.5 cm. Longer distances were less precisely defined for several thousand years. For example, the Roman mile was considered to be the distance covered by 1000 double paces, roughly equal to 1.5 kilometers.Early measurements of area were also not very precise. An acre came to be defined as the amount of land that could be plowed by a yoke of oxen in one day. Of course, the area plowed varied greatly according to the nature of the land and the heartiness of the oxen.Volume and MassFor things like grain and liquids, measuring volume was usually easier to do than measuring mass. It was simpler to fill a container of a specific size with seeds, water, honey, or oil than it was to weigh these substances. However, highly valuable substances demanded a more precise system of measurement, and for certain substances, measurements of mass were more accurate.Measurement of mass was first used for gold dust about 5000 B.C. But the use of the balance scale did not come about until more than 2000 years later. This kind of scale was made of a beam that rests on a pivot point at its center and has one pan to hold objects to be weighed, or massed, and another pan that holds standard masses. The same kind of scale is still used to make precise measurements of mass today.The Metric SystemThe invention of the metric system led to the standardization of measurement through much of the world. It began as a decimal system of physical units based on a unit of length known as the meter. This system was adopted by law in France during the 1790s. During these years, French scientists measured part of the distance from the equator to the North Pole on a line running through Paris. They then estimated the total distance and divided it into ten-millionths. In other words, a distance one-quarter around the Earth was made up of ten million meters. The problem with this was that the calculations of the French scientists were based on the assumption that Earth was a perfect sphere. When scientists later discovered that Earth was not a sphere, the meter needed to be based on a different standard. It became defined internationally as the distance between two lines etched on a bar of platinum-iridium allow, which was kept at a constant temperature at Sevres, near Paris.Later, scientists developed a still more precise standard. A meter came to be defined internationally as the length of the path traveled by light in a vacuum during a time interval of 1/299,792,458 of a second.Despite the invention of the metric system, people in the U.S. and Great Britain continued to use the inch, foot, yard, and mile to measure length. The British yard was based upon a standard known as the imperial standard yard, which was the distance between two marks on a bronze bar manufactured in 1839 and then recreated in 1845. But eventually it was discovered that the bar was shrinking at a rate of one millionth of an inch per year. In 1899, in response to this problem, the U.S. decided to base its standard of length on a standard meter. In 1960, the Eleventh Congress on Weights and Measures called for a universal system of measurement based on the metric system. Six base units of measurement were decided then and one more was added in 1971. They included the meter, the kilogram, the second, the ampere, and the Kelvin. They also included the mole, which expresses the molecular weight of a substance in grams, and the candela, which measures light intensity. This international standard became known as the SI system, which stands for Systeme International. Established units of measurement with special units, such as the nautical mile, the knot, and the hectare were temporarily accepted as valid, but these may come up for review in the future. Since 1975, the U.S. has officially committed itself to convert to the metric system. However, efforts among businesses, governments, and individuals have been slow-moving and many people still feel more comfortable using the English system. Making the ConnectionMake a system of measurement for length by using your own forearm as a cubit. Use your cubit to measure the size of your classroom and various objects in the room. Make a chart of your measurements. Compare your measurements with those of your classmates.What might happen if you were working on a project to build a model bridge with a classmate and you each used your own cubit to measure and cut pieces of wood for the model?________________________________________________________________________________________________________________________________________________________________________What difficulties might people today have if measurements of length and mass were not standardized?________________________________________________________________________________________________________________________________________________________________________3) When you return to class tomorrow measure the top of your table in cubits. Complete the data table below with the tabletop measurements the others at your table made. Complete the data table with measurements obtained by the students sitting at another table like yours. My TableAnother TableThe Length of Tabletops in Cubits4) What kind of graph would you make if you wanted to show the differences in measurements obtained for the same tabletop? ____________________________________________________________________________________ ................
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