Petameter
A petameter (Pm) is a unit of length in the metric system, equal to 1 quadrillion meters (1 petameter = 10¹⁵ meters). This unit is extremely large and is used mainly in astronomy and theoretical physics to describe vast distances, such as those between stars or galaxies. For example, one petameter is about 105.7 light years. Since it measures such enormous distances, the petameter is not used in everyday life or common scientific applications—it’s mostly used in discussions about the scale of the universe.
Russian Archin
The archin (also spelled arshin) is a traditional Russian unit of length that was widely used before the adoption of the metric system. It is approximately equal to 28 inches or 0.7112 meters.
The archin was commonly used in measuring cloth, land, and building dimensions in Russia and neighboring regions. It roughly corresponds to the length of a forearm from the elbow to the tip of the middle finger, similar to the cubit.
Though obsolete today, the archin remains an important part of Russian historical measurements and appears in older legal and trade documents.
Summary:
1 archin ≈ 28 inches (0.7112 meters)
Used historically in Russia for textiles and land measurement
Based on the length of the forearm
Mostly of historical and cultural interest today
No conversions available for length.