Exploration Earth (audio story)

Exploration Earth: The Time Machine was the third episode of the BBC Schools radio series Exploration Earth, a series exploring geography. As it was an educational programme, it used the Doctor Who format and elements to explore the processes of the creation of the Earth. The subtitle The Time Machine was never actually said on-air, nor used on packaging from the BBC Audio release. It may, however, have been used in Radio Times listings, teacher's guides and other contemporary "internal" documents.

Publisher's summary
In this special BBC schools radio episode, not heard since its original 1976 broadcast, the TARDIS takes the Doctor and Sarah back in Time to witness stages of the Earth's development. However, as the planet evolves from a mass of heat and gas, Megron the High Lord of Chaos has his own designs on our homeworld. If his threats to endanger the stability of Earth have any substance, the existence of Mankind itself is in question!

Plot
The Doctor notices a fault with the TARDIS controls. After mumbling some technobabble, he's forced to simplify things for Sarah: the steering's gone out. A force has gripped the TARDIS and thrown it back 4,500 million years into Earth's past. Once they arrive, they get into a two-person space capsule and explore the nascent Earth, which at that time is just an oxygen-less ball of gas. The Doctor points out that at the core of all that gas is a molten core which will form the planet Sarah knows as Earth.

The two ascend back to the orbiting TARDIS, and are controlled again by the mysterious force. This time it drags them millions of years in the future. They return to the capsule to view what has become of the Earth since they last looked upon it. Now, the planet is much smaller, closer to the size Sarah knows. The planet is considerably more solid, the Doctor notes — its crust rapidly forming. While they are examining the planet's geologic fury, they hear a disembodied voice. It's a Megron, claiming that he has taken control of Earth. The Megron have been attracted to Earth at this point in its history because they believe the planet's geologic formation is an expression of chaos and disharmony. When the Doctor points out that it's actually a sign of progress and coming order, the Megron disappears, blowing the duo back into the TARDIS and further down the time vortex.

The Doctor and Sarah again are thrown yet more millions of years forward. Sarah now can't help but notice the numerous volcanoes dotting the surface of the planet. Sarah is profoundly disturbed by the violence they seem to be meting out on the surface of the Earth, but the Doctor finds it beautiful. He lets her look through a device that shows the history of the planet passing before her eyes, so as to show her the cause and effect of volcanic activity and plate tectonics. She's getting physically sickened by it all, but the Doctor continues to enthuse about the creative spectacle. Finally, when she sees a mountain range form before her eyes, Sarah begins to get excited by the process as well. The Doctor points out that this is the beginning of true order on the planet. The Megron then returns, but he's still not buying the Doctor's claims that the planet is emerging from chaos. The Doctor counters that the planet is no longer exclusively using space gases: a little oxygen has begun to be sustained on the planet itself. The Megron still tries to deny things.

Back in the TARDIS, the duo have moved on to a point when the Earth has an atmosphere and life. Oxygen has come in abundance to the Earth. But the Megron is still there. The Doctor challenges him to a telepathic duel. The Megron loses, and the Doctor banishes him from Earth.

Cast

 * The Doctor - Tom Baker
 * Sarah Jane Smith - Elisabeth Sladen
 * The Megron - John Westbrook

Crew

 * Writer - Bernard Venables
 * Producer - David Little
 * Special Sounds - Dick Mills and the BBC Radiophonic Workshop
 * No other individuals were actually credited on-air at broadcast

Continuity

 * The earliest scene in this production seems to take place after the earliest scene in The Runaway Bride. That is, the Doctor and Sarah arrive after gravity had pulled the core of the planet together.  Thus, this play does nothing to upset Donna's discovery of a Racnoss spaceship at the center of the planet.
 * As with all other made-for-radio and other audio adventures, the canonicity of Exploration Earth remains unclear.

Timeline

 * This story occurs after ST: Old Flames
 * This story occurs before DW: The Hand of Fear

Releases

 * As a cassette and CD from the BBC Radio Collection, paired with the audio adaptation of Genesis of the Daleks.
 * As a stand-alone CD release as part of the Daily Telegraph/WH Smith 2010 giveaway.