Mass Observation was created in 1937.
Observation on the Spot was created in 1982.
The statement is an observation. It describes the phenomenon that occurs when iron rusts in a closed container, indicating that the total mass remains constant despite the chemical reaction. This aligns with the law of conservation of mass, which states that mass is neither created nor destroyed in a closed system.
Ground Observation Corps was created in 1950.
Wanne Observation Tower was created in 1888.
Observation Tower Burgholzhof was created in 1891.
Hünenburg Observation Tower was created in 1952.
Sinnott Memorial Observation Station was created in 1931.
Observation Tower Height of Goetzingen was created in 1883.
Combined Pilots-Observation Badge was created on 1936-03-26.
Hurricane Mountain Fire Observation Station was created in 1919.
Snowy Mountain Fire Observation Station was created in 1917.
Azure Mountain Fire Observation Station was created in 1918.