The picometre is a unit of length and is a multiple of the SI unit metre. It uses the symbol pm.
It represents one trillionth of a metre, or one hundredth of an Ångström.
Because the picometre is so small, its use is restricted almost entirely to chemistry, quantum physics and particle physics. Atoms are typically 62 pm and 520 pm.
LISA (Laser Interferometer Space Antenna) is a probe planned for launch in 2034 to detect gravitational waves in space. Its measures these displacements with an accuracy of up to 20 pm over a distance of 2,500,000,000 m.
The yard is a unit of length in the imperial and US system and uses the symbol yd.
A yard is equal to 3 ft or 36 inches. There is 0.9144 m in a yard. There are 1760 yards in a mile.
Derived from the Old English 'gyrd' or 'gerd', the yard was first defined in the late 1600s laws of Ine of Wessex where a "yard of land" (yardland) was an old unit of tax assessment by the government.
The yard was the original standard adpoted by early English leaders and was apparently used in length by the Saxon race and represented the breadth of the chest of a man. After a relative hiatus, Queen Elizabeth reintroduced the yard as the English standard of measure, and it still survives in many 2nd generation conversations today.