Electrons moved in two dimensions when influenced by a magnetic field, hinting at how a similar effect would occur in the fourth dimension.

His absence is explained by having the Doctor locked up ... Vicki explains to Steven that TARDIS stands for ‘Time and Relative Dimensions in Space’. This is the first time that ‘Dimension ...

Patrick Troughton took a holiday during the making of Episode 2. His absence was explained by having the Doctor unconscious for the whole episode. For the first time in the show’s history ...