# how has the meter been defined over time

The meter is the basic unit of length in the SI system of units. The solution was to define the metre in the same manner as the ångström had been defined in 1907, that is … Following the successful 1983 redefinition of the metre in terms of an exact numerical value for the speed of light, the BIPM's Consultative Committee for Units (CCU) recommended and the BIPM proposed that four further constants of nature should be defined to have exact values. ALDER: Historians have estimated that, within France alone, there were 250,000 different units of measurement in use at the time. Historically, the metre was defined by the French Academy of Sciences as the length between two marks on a platinum-iridium bar, which was designed to represent 1/10,000,000 of the distance from the equator to the north pole through Paris. metric system, system of weights and measures planned in France and adopted there in 1799; it has since been adopted by most of the technologically developed countries of the world. It is based on a unit of length, called the meter (m), and a unit of mass, called the kilogram (kg).. A Unit of mass : kilogram : The kilogram, symbol kg, is the SI unit of mass. ... the length of one meter was defined on the basis of the speed of light and time. As time passed, more and more European countries adopted the French meter as their length standard. These are: The Planck constant h is exactly 6.626 070 15 × 10 −34 joule-second (J⋅s). An interesting effect of the definition of the meter this way is that it fixes the speed of light in a vacuum to the exact value of 299,792,458 m/s. The meter was defined accordingly, as the distance traveled by a beam of light in exactly 1/299,792,458th of a second. Since 1983 the standard meter has been defined in terms of which of the following? Nonetheless, it was decided that the meter would remain as realized in the platinum bar. This added an additional measurement uncertainty to any length result in metres, over and above the uncertainty of the actual interferometric measurement. Long ago, the base for reference was the human body. It is defined by taking the fixed numerical value of the Planck constant h to be 6.626 070 15 × 10-34 when expressed in the unit J s, which is equal to kg m 2 s-1, where the meter and the second are defined in terms of c and Δν Cs. Subsequent definitions of the meter have since been chosen to hew as closely as possible to the length of that first meter bar, despite its shortcomings. a. Scientists find an average of 40 microplastic particles per cubic meter of the northern water. ± specific alloy bar housed at Sevres, France b. The way base units of length have been determined has changed greatly over time. This meter has been used for centuries for a range of purposes—from Christian hymns and the Romantic poems of Wordsworth, to television theme songs, and its popularity over that time earned it the name "Common meter." PALCA: So this … ... just how badly even these remote waters have been tainted. Today, one meter is defined as "the distance that light travels in a vacuum in 1/299,792,458 of a second," as defined in 1983. The meter is defined to be the distance light travels through a vacuum in exactly 1/299792458 seconds. Poems are written using many other sorts of meters as well, of course, but the two above are the most common. Start studying Physical Science Chapter 1: Measurements (first half). Learn vocabulary, terms, and more with flashcards, games, and other study tools.