What is a White Hole?



A diagram of the structure of the maximally extended black hole spacetime. The horizontal direction is space and the vertical direction is time.

The equations of General relativity have an interesting mathematical property: they are symmetric in time. That means that you can take any solution to the equations and imagine that time flows backwards rather than forwards, and you will get another valid solution to the equations. If you apply this rule to the solution that describes Black Holes, you get an object known as White Hole. Since a Black Hole is a region of space from which nothing can escape not even light the Time-Reversed version of a Black Hole is a region of space into which nothing can fall. In fact, just as a Black Hole can only suck things in, a White Hole can only spit things out.

White holes are a perfectly valid mathematical solution to the equations of General relativity, but that does not mean that they actually exist in nature. In fact they almost certainly does not exist, since there`s no way to produce one. (Producing a white hole is just as impossible as destroying a Black Hole, since the two processes are Time-Reversals of each other.)

See also  -1) https://forastrophysicist.blogspot.com/2019/08/what-if-sun-become-black-hole.html?m=1

2) https://forastrophysicist.blogspot.com/2019/08/how-big-is-black-hole.html?m=1

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