The Day After Tomorrow (also known as Into Infinity in the United Kingdom) is a 1975 British science fiction television special produced by Gerry Anderson between the two series of Space: 1999.

Written by Johnny Byrne and directed by Charles Crichton, it stars Brian Blessed, Joanna Dunham, Nick Tate, Katharine Levy and Martin Lev, with narration by Ed Bishop.

Set in a future where environmental damage on Earth threatens the survival of humanity, The Day After Tomorrow follows the interstellar mission of Altares, a science vessel that uses photon energy to travel at the speed of light.

After leaving the Solar System and reaching Alpha Centauri, their primary destination, the crew of Altares push deeper into space; there, they encounter phenomena including a meteor shower, a red giant and, finally, a black hole, which pulls the ship into another universe.

Originally commissioned to produce a child-friendly introduction to Albert Einstein's theory of special relativity, Anderson and Byrne conceived The Day After Tomorrow as a pilot for a TV series, with the episode title "Into Infinity".

Critical responses to The Day After Tomorrow have been mixed: while its model effects and music have been praised, it has divided opinion with its "psychedelic" images, which have been compared to the visual style of film director Stanley Kubrick.

[2] As Altares leaves the Solar System, Jane and David observe how Pluto turns blue, then red, due to the shortening and lengthening of light waves caused by the Doppler effect.

Although the ship cannot reach the faster-than-light speeds needed to break free, Anna believes that the hole may lead to another universe and urges her companions not to give up hope.

I wanted young people to watch this film on television and find it exciting enough that, in the course of viewing the programme, they would be able to acquire an understanding of Einstein's theory of relativity.

[4] To launch the series, Heinemann commissioned Anderson to produce an episode about Albert Einstein's theory of special relativity, which holds that the speed of light cannot be exceeded and remains constant whether an object is still or moving.

[1] Faced with the prospect of cancellation, Anderson and Space: 1999 story editor Johnny Byrne conceived Heinemann's episode, which they had named "Into Infinity", as a pilot for a new series, provisionally titled The Day After Tomorrow.

[1][4] Anderson was ultimately unable to secure the funding needed to make further episodes, leaving "Into Infinity" – now more commonly known by the series title – as a one-off special.

I went into my office and wrote a little thing that took the principle of a ship travelling at the speed of light and put a family in it – so by not leaving them separated meant they wouldn't age at different rates because of the dilation effect.

Byrne – who, like Anderson, had no scientific background – found the central concept hard to grasp: "Once I got the go-ahead I suddenly realised I knew very little about the theory of relativity ...

Recognising that the child characters Jane and David would serve to represent the young audience's curiosity and ask questions on its behalf, Heinemann wanted them to be "just like real children" rather than "[coming] across like kids do on Saturday morning programmes.

"[3] Byrne wrote the dialogue in such a way that the characters give only partial explanations of the phenomena they encounter, the aim being to encourage the audience to study the topics in their own time and develop their researching skills.

[1] In the absence of Bob Bell and Keith Wilson, who were working on The New Avengers and Star Maidens, Anderson's business partner Reg Hill assumed the role of production designer.

[1][2] A three-foot-long (0.91 m) model was used for long shots; close-ups used a larger, six-foot (1.8 m) version, which was fitted with a powerful light for the photon drive as well as freon gas-powered jets to simulate exhaust.

[1][4] As Anderson's regular composer Barry Gray had other commitments, newcomer Derek Wadsworth was contracted to produce the theme and incidental music (the latter in collaboration with Steve Coe).

[6][12] Like the title sequences of Anderson's earlier productions, The Day After Tomorrow opens with a fast-paced montage of action shots from later in the episode, giving a preview of the story to come.

In a review for TV Zone magazine published in 2002, Andrew Pixley praised the acting, music and direction, commenting that the programme "oozes with the charm associated with the golden era of Anderson."

He also regards the "info dump" introduction as a weak imitation of the Space: 1999 opening titles and argues that the repeated appearances of the mass–energy equivalence equation, E = mc2, only confuse the audience.

He considers the special to have aged poorly, noting that while Altares is presented as a "lightship" of the future, some of the on-board equipment resembles 20th-century devices such as slide rules and punched cards.

Calling The Day After Tomorrow a "high-tech, science-minded update of the whole Lost in Space format", he comments that its plot mixes action with "psychedelic" moments like the fall into the black hole ("a Kubrickian wonder, a montage dominated by double images, slow-motion photography and the use of a creepy distortion lens.

"[10] He also describes the special as "less minimalist ... in colour and costume" than the first series of Space: 1999, believing that elements like Wadsworth's "hard-hitting, hard-driving" score liven up the proceedings.

Science-fiction writer and critic Christopher Mills likens the special to a 2001 "for kids", noting that the plot features "wonky pseudo-science and insanely improbable coincidences".

[10] David Hirsch of Starlog magazine suggests that the lack of interest from TV networks in funding a series may have been due to the fact that the special's first appearance preceded the release of Star Wars (1977), which triggered a renewal of the science fiction genre.

[21] In 2002, a DVD of The Day After Tomorrow and Star Laws, Anderson's 1986 pilot for a series that would later be made as Space Precinct, was released by Fanderson as part of its members-only merchandise range.