Magnetron

Magnetrons were devices used to transport massive objects, such as planets. The technology was possessed by both Daleks and Time Lords alike.

History
At some point in their early history (after the year 5000, during the Great War) the Daleks were developing an experimental magnetron to use as a weapon. A huge circular coil, it would be capable of producing powerful magnetic fields through superconductivity and be able to draw passing starships out of the sky. (PROSE: The Evil of the Daleks)

The Time Lords used a magnetron to transport the entire solar system in what became known as the Ravolox Affair, resulting in the devastation of Earth's biosphere. (TV: The Mysterious Planet, The Ultimate Foe) The Magnetron was later used to return the solar system to its original location. (PROSE: The Eight Doctors)

Following the Last Great Time War, the New Dalek Empire used a magnetron to move 27 planetary bodies to the Medusa Cascade. The Tenth Doctor, the Meta-Crisis Tenth Doctor and Donna Noble later used it to return all but one of them to their original locations; they were forced to "tow" the Earth using the TARDIS after the magnetron was struck by the Supreme Dalek's gunstick beam. (TV: Journey's End) Through the projections of the Matrix, the Time War-era Time Lords learnt of this event and noted that moving the Earth was one of their own tactics, having done so during the Ravolox Affair. Therefore, they realized the Daleks were willing to employ their own tactics against them. Furthermore, the fact that the Daleks managed to move the Earth without devastating the planetary biosphere proved to the Gallifreyans that their enemy had better technology than their own. The ways through which the Daleks moved entire planets thus became a matter that they began to urgently study. (PROSE: Dalek Combat Training Manual)

Features
The Daleks' version was evidently somewhat more advanced than the Time Lord version, which destroyed most of Earth's surface when it was used on the planet; by comparison, the Dalek version did no apparent damage at all to the planet, however it was used to move the rest of the solar system at the same time so it must have caused some feedback. While it can be assumed that the Time Lord magnetron probably could have been used to transport objects through time as well as space, only the Dalek technology was explicitly shown to have a temporal aspect, as some of the stolen planets were taken from completely different moments in time. (TV: Journey's End)

Alternate timelines
In the alternate timeline of the Time Paradox Incident, the Daleks used a Time Vortex Magnetron which would cause the human guerrillas who had travelled to the 20th century to be drawn to the Daleks' base the next time they used their time machine. By mistake, Jo Grant was drawn in instead. (TV: Day of the Daleks)

In another alternate timeline, a vortex magnetron was on display in a museum in the Tower of London. (AUDIO: Jubilee)

Behind the scenes
Magnetrons are, from which their use in Doctor Who can be reasonably extrapolated. They are used in the transmission of television signals and are the source of power in microwave ovens. They allow for the quick production of a great deal of energy.