Blinovitch Limitation Effect

The Blinovitch Limitation Effect was the effect or non-effect of crossing timelines.

Named after Aaron Blinovitch who formulated the Blinovitch theory in a reading room in the British Museum in 1928 on Earth. (MA: The Ghosts of N-Space)

Theory A
The limitation effect limits the amount a person can change their time line, in fact any changes which deviate create a time loop. (DW: Day of the Daleks)

Theory B
The effect is the energy released when crossing your own timeline and interacting with a past (or future depending on perspective) and the energy thus released. (DW: Mawdryn Undead) This aspect of the effect, however, does not appear to come into effect when different incarnations of a single Time Lord, such as The Doctor interact with each other. (DW: The Three Doctors, The Five Doctors, et al)

Theory C
The Limitation Effect stops a time traveller from messing around with their own personal timeline. The limitation effect is a precursor to a paradox (probably). (DW: Day of the Daleks)

Theory D
If someone continually returns to a time period they have previously time traveled to, then each time they return it becomes increasingly more difficult to change what happens in that moment of time. (Doctor Who: Adventures in Time and Space)