White hole

In general relativity, a white hole is a hypothetical region of space-time which cannot be entered from the outside, although matter and light can escape from it. It is the reverse of a black hole, which can only be entered from the outside and from which matter and light cannot escape.

         Best example for a white hole is, imagine that white hole is a chocolate fountain where all chocolates are flowing outwards, but in case of white holes it is photons and mass instead of chocolates.
           Even the big bang has been described as a white hole. According to this theory, the universe might have originated from a black hole that lies within another universe. If a black hole and a white hole are the two ''mouths" of a wormhole, then all the matter and energy falling into a black hole could in theory come out a white hole in another universe.
          White holes were born as a solutions to Einsteins general relativity equation. White holes also have the properties like mass, charge and angular momentum. The objects falling towards a white hole would never actually reach the white holes event horizon.
         According to maximally extended schwarzschild solution, the white holes event horizon in the past becomes a black holes event horizon in the future, that means any object falling towards it, will eventually reach the black hole horizon.
     The physicist Sean Carroll says, " A black hole is a place where you can go in but you can never escape, a white hole is a place where you can leave but you can never go back.
        But unfortunately, the time dilation near a white hole would be similar to that of a black hole, that is time would move slower, but for an observer very far away, it would appear as if the object near the event horizon is being thrown out really slow. While in case of black hole the observer outside the event horizon would appear as if the object is falling very slowly into the black hole.