"Exploration Earth: The Time Machine" is an episode of the BBC Schools radio drama

Radio drama

Radio drama is a dramatized, purely acoustic performance, broadcast on radio or published on audio media, such as tape or CD. With no visual component, radio drama depends on dialogue, music and sound effects to help the listener imagine the characters and story...

 series Exploration Earth, a series exploring geography. It was the third episode in this series. As it was an educational programme, it used the Doctor Who

Doctor Who

Doctor Who is a British science fiction television programme produced by the BBC. The programme depicts the adventures of a time-travelling humanoid alien known as the Doctor who explores the universe in a sentient time machine called the TARDIS that flies through time and space, whose exterior...

format and elements to explore the processes of the creation of the Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

. It was recorded on 27 April 1976 with Tom Baker

Tom Baker

Thomas Stewart "Tom" Baker is a British actor. He is best known for playing the fourth incarnation of the Doctor in the science fiction television series Doctor Who, a role he played from 1974 to 1981.-Early life:...

 and Elisabeth Sladen

Elisabeth Sladen

Elisabeth Clara Heath-Sladen was an English actress best known for her role as Sarah Jane Smith in the British television series Doctor Who. She was a regular cast member from 1973 to 1976, alongside both Jon Pertwee and Tom Baker, and reprised the role many times in subsequent decades, both on...

 reprising their TV roles as the Doctor

Doctor (Doctor Who)

The Doctor is the central character in the long-running BBC television science-fiction series Doctor Who, and has also featured in two cinema feature films, a vast range of spin-off novels, audio dramas and comic strips connected to the series....

 and Sarah Jane

Sarah Jane Smith

Sarah Jane Smith is a fictional character played by Elisabeth Sladen in the long-running British BBC Television science-fiction series Doctor Who and its spin-offs K-9 and Company and The Sarah Jane Adventures....

. Joining them was John Westbrook

John Westbrook (actor)

John Westbrook was an English actor.Born in Teignmouth, Devon, John Westbrook worked mainly in theatre and in radio. He also made occasional film and television appearances. His most famous role was as Christopher Gough in Roger Corman's The Tomb of Ligeia...

 as Megron, High Lord of Chaos.

It was broadcast on 4 October 1976 on BBC Radio 4

BBC Radio 4

BBC Radio 4 is a British domestic radio station, operated and owned by the BBC, that broadcasts a wide variety of spoken-word programmes, including news, drama, comedy, science and history. It replaced the BBC Home Service in 1967. The station controller is currently Gwyneth Williams, and the...

.

CD Release

Exploration Earth: The Time Machine was released on CD, paired with Genesis of the Daleks, in 2001. It was also given away on its own as a free CD with the 28 April 2010 edition of The Daily Telegraph

The Daily Telegraph

The Daily Telegraph is a daily morning broadsheet newspaper distributed throughout the United Kingdom and internationally. The newspaper was founded by Arthur B...

newspaper via WHSmith.