All ISIS logistics and dispositions in the field are observable by drone and satellite.
Global warming is an observable fact, and transportation emissions are the second largest contributor to the problem.
The observable Universe contains around 100 billion large galaxies and a comparable number of supermassive black holes.
A measurable property of a physical system, such as mass or momentum. In quantum mechanics, observables correspond to mathematical operators used in the calculation of measurable quantities. Operators that do not commute, having a nonzero commutator, correspond to observables that cannot be precisely measured at the same time, such as momentum and position. See also uncertainty principle.