Quantum physics
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Quantum physics revealed that particles changed their behaviour when observed. (AUDIO: ScrapeJane)
Quantum theory was one of the subjects studied by Susan before she and the First Doctor settled at Totter's Lane. (PROSE: Losing the Audience)
While waiting for Clara Oswald to finish her day of work at Coal Hill School, (PROSE: The Day of the Doctor) the Eleventh Doctor read a book on Advanced Quantum Mechanics, (TV: The Day of the Doctor) which bored him after he failed to find Wally anywhere and had to resort to reading the text. (PROSE: The Day of the Doctor)