Agauge of how exact a measurement is called

Abird sitting high in a tree is an example of what type of wnergy

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?

According to an observer on earth, planet x is stationary. maria and samir depart earth on their spaceships at the same time, each flying at 0.5c. maria flies toward planet x and samir flies in the opposite direction. according to maria, her voyage to planet x takes 9 years. how many years does maria's voyage take according to samir?