Facts About India

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Unit of Length

The meter and the kilogram had their origin in the metric system. Meter was originally defined as one 10 millionth of the distance from the North Pole to the equator of the Earth. By international agreement, the standard meter had been defined as the distance between two fine lines on a bar of platinum-iridium alloy preserved at constant temperature of 273.16 K at one bar pressure.

The 1960s conference, defined the meter as 1,650,763.73 wavelengths of the reddish orange light emitted by the isotope krypton-86. The meter was again redefined in 1983 as the length of the path travelled by light, in vacuum, during a time interval of 1/299,792,458 of a second. Accuracy can be measured to 1 part in 10 13 .

Unit of Length Chart
Unit of Length Chart

Units based on meter are:

1 km = 1000 m = 103m

1 cm = 1/100 m = 10-2m

1 mm = 1/1000 m = 10-3m

1 um = 1/1000000 m = 10-6m

1 nm = 1/1000000000 = 10-9m
Very small distances are measured in micrometres or microns, angstroms, nanometers(nm) and femtometers(fm)
1m = 103mm = 109 nm

Large distances such as distances of star from the earth are expressed in Light year. Light year is a unit of length equal to the distance travelled by light in one year.

1 light year = 9.46 x 1015m

Range of lengths

Size of objects for distances Length (m)
Radius of a proton 10-15
Size of atomic nucleus 10-14
Size of hydrogen atom 10-10
Length of typical virus 10-8
Wavelength of light 10-7
Size of red blood Corpuscle 10-5
Thickness of the paper 10-4
Height of the Mount Everest above sea level 104
Radius of the Earth 107
Distance of bone from the Earth 108
Distance of the sun from the 1011
Distance of Pluto from Sun 1013
Size of our Glaxay 1021
Distance of Andromeda galaxy 1022
Distance to the boundary of observable universe 1026


Parallex Method
To measure the large distances, such as star or a planet, an important method is Parallex Method. In this method and object is observed from two different points.

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