Time after time a crack appeared in several episodes, it was first revealed in Amys room in the Eleventh Hour.
The time field was a body of time energy that spilled from cracks in the fabric of time and space. The cracks were created by the Silence when they blew up The Doctor’s TARDIS on 26 June 2010, as a means of preventing The Doctor from reaching Trenzalore .
The cracks were described by the Eleventh Doctor as “two parts of space and time that should never have touched, pressed together”. They were present in the very fabric of spacetime – a crack that appeared to be part of a wall would still be there if the wall were removed
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The crack is seen in Amys wall, and at the end of the end of the episode and on the new TARDIS view screen
The crack is at the bottom of the ship just after The Doctor left..
The crack appears after the TARDIS dematerialises at the end of the episode.
The crack appears on the spacehip when The Doctor and River meet
The crack appears at the end of Cold Blood
The crack starts to appear when Amy finds her engagement ring in Craigs house.
A residual crack was used by the Time Lords to reach out to the universe on Trenzalore from where they were trapped in a pocket universe in an attempt to return to the universe. The Eleventh Doctor spent hundreds of years defending the planet and crack as he refused to restore the Time Lords as it would cause the Last Great Time War to restart – but also refused to abandon the people of the town of Christmas to the armies of his enemies surrounding the planet. Eventually Clara Oswald used the crack to implore the Time Lords to save the Eleventh Doctor who was dying of extreme old age due to having no more regenerations. They were able to move the crack and use it to grant The Doctor a new cycle of regeneration before closing it, changing the future of the Doctor and Trenzalore.