Stephen Hawking

Stephen Hawking was a Human scientist in the late 20th early 21st century.

When Dalek Thay encountered the Cybermen, Mickey Smith compared this to Stephen Hawking meeting the speaking clock, a reference to his paralysis which required him to use a voicebox to speak.

Stephen Hawking died sometime before 2050, where the famous scientist Alistair Gryffen used the phrase "Hawking's Ghost!" to express shock. (K9TV: The Last Oak Tree)