Gravity globe
From Tardis Wiki, the free Doctor Who reference
A gravity globe, or grav globe, was a human device to provide massive illumination. It could be sent aloft under its own power so that it would "hang" at a set height and provide light in a large space. Gravity globes were particularly useful in large dark caves.
Ida Scott used a globe to light up Krop Tor's core. (TV: The Impossible Planet/The Satan Pit)
The Clerics used a globe to light up the Maze of the Dead. (TV: The Time of Angels/Flesh and Stone). The Eleventh Doctor destroyed it to help the group jump onto the underside of the Starship Byzantium.
Ironically, it does nothing but float and glow, only applying noticeable force to nearby objects when destroyed. (Flesh and Stone)
