White Hole: What Is It & How Does It Differ from Black Hole?

[physicsnoob12]

what is a white hole and how does it differ from a black hole?

 

[NobodySpecial]

There's no such thing - probably
Outside SF, a few cranks, and a bunch of theoretical astrophysicts there is no need for white holes in any current theory.

Of course it's big universe and stranger things have happened

 

[physicsnoob12]

ahh thank you someone was throwing the term around and i had no idea what it meant

 

[Kevin_Axion]

A white hole and a black hole attach two locations in space-time, the black hole draws things inwards where as a white hole is were all of the material is excreted. But as stated, they are non-existent.

 

[Finbar]

In general relativity for every solution to the field equations there exists a time reversal which also solves the field equations. Hence if black holes are solutions to the field equations so are their time reversal t--> -t. These solutions are called white holes.

The reason that we don't expect to see them in nature is because they would require very unlikely initial conditions(eg exploding matter close to a singularity). So by the second law of thermodynamics we can exclude their existence at large distances, large masses etc. However
one may expect that at very short distances with very few degrees of freedom they may contribute to the path integral in quantum gravity.