Earthsearch: A Ten-Part Adventure Serial in Time and Space is a BBC Radio 4 science fiction series written by James Follett, comprising ten half-hour episodes broadcast between January and March 1981. There is also a novelisation by Follett under the same title. The series has been released on cassette and audio CD, and has been rerun several times on BBC 7 beginning in 2003.
Some years before the story opens, the huge Earth starship Challenger, on a mission to find Earth-like planets for colonization, encountered a meteoroid shower that killed all of the adult crew and seriously damaged the ship. The only human survivors were four babies - two boys, Telson and Darv, and two girls, Sharna and Astra.
The four have been raised from childhood by androids and tutored by two disembodied voices called Angel One and Angel Two. Most of the humans believe the voices are real angels, but Darv is more suspicious and believes they are actually computers.
Darv is correct. The Angels are the Challenger's ancillary control computers. Due to a fault in their design they have become megalomaniacal and want to return to Earth and rule it. It was they who deliberately manoeuvred the Challenger into the path of the meteoroids and shut off the ship's defences. Unfortunately for them, they underestimated the amount of damage that would result, not only to the ship but themselves. As a result they have lost an unknown amount of potentially vital information about the nature of space and time.
They are also having difficulties with the human crew, despite retarding the onset of puberty with drugs in order to keep them sexually ignorant. Telson, now commander, and Sharna are compliant, but Darv is headstrong and independent and is beginning to win Astra over.
When the Challenger arrives in Earth's solar system, the crew and the Angels are equally surprised to discover that the Earth has vanished, leaving the moon behind. The irony is that the Angels now need Darv's rebellious mind to try to figure out where Earth has gone, otherwise they will have no planet to rule.
The rest of the series deals with the crew's attempts to solve the mystery, encountering various humans and computers, hostile and otherwise, on their travels, while attempting to throw off the Angels' control over them once and for all.
In the final episode the crew leave the Challenger to settle on a new planet which they call Paradise.
The story is continued in Earthsearch II. The prequel Mindwarp is set on the original Earth. While it has only a loose connection to the Earthsearch series, it sets the stage for it, and contains many familiar plot elements and character traits.
The series is notable for not violating the known laws of physics by introducing faster than light travel. Instead the crew must enter suspended animation while the ship is travelling. The crew's ignorance of the time dilation effect caused by relativity is a major plot point.
Most of the regular cast had cameo roles (sometimes playing more than one character) in BBC Radio's 1981 production of The Lord of the Rings, because the cast were all still members of the BBC Radio Drama Repertory Company at the time when the Tolkien adaptation was being made.
In the original broadcast, when Angel One and Angel Two are talking to each other Angel One's voice is heard on the left stereo channel only and Angel Two on the right (although due to the technical limitations of the recording some crosstalk can be heard on the opposite channels). In the BBC 7 broadcast they are sometimes heard on the opposite channels, indicating that entire episodes are broadcast with the stereo channels transposed. Furthermore, listeners to BBC 7's mono DAB service complained that they could only hear one half of these conversations, indicating that the DAB transmission may have been sometime taken from one of the two stereo channels instead of being a mix of both.