Which of the following is a characteristic of gyroscopes?

A fundamental characteristic of gyroscopes is their rigidity in space. This property refers to the tendency of a rotating gyroscope to maintain its orientation, resisting changes to its axis of rotation. As a gyroscope spins, the forces acting on it help keep it stable, providing a reliable reference point. This is critical in aviation, particularly in instruments used for navigation and attitude indication, where maintaining a constant reference helps pilots understand the aircraft's orientation in three-dimensional space.

The other options do not accurately describe the defining attributes of gyroscopes. For instance, loss of speed pertains to the velocity of a rotating object rather than a direct characteristic of gyroscopic behavior. Change in altitude is related to vertical positioning and does not reflect the unique properties of gyroscopes. Additionally, lightweight construction can be a feature of some gyroscopic systems, but it is not a defining characteristic of gyroscopes themselves. Thus, rigidity in space stands out as the correct and significant characteristic related to gyroscopes.