White Holes

White holes are theoretical cosmic regions that function in the opposite way to black holes. Just as nothing can escape a black hole, nothing can enter a white hole.

To a spaceship crew watching from afar, a white hole looks exactly like a black hole. It has mass. It might spin. A ring of dust and gas could gather around the event horizon — the bubble boundary separating the object from the rest of the universe. But if they kept watching, the crew might witness an event impossible for a black hole — a belch. \”It\’s only in the moment when things come out that you can say, \’ah, this is a white hole,\’\” said Carlo Rovelli, a theoretical physicist at the Centre de Physique Théorique in France.

Physicists describe a white hole as a black hole\’s \”time reversal,\” a video of a black hole played backwards, much as a bouncing ball is the time-reversal of a falling ball. While a black hole\’s event horizon is a sphere of no return, a white hole\’s event horizon is a boundary of no admission — space-time\’s most exclusive club. No spacecraft will ever reach the region\’s edge.

Objects inside a white hole can leave and interact with the outside world, but since nothing can get in, the interior is cut off from the universe\’s past: No outside event will ever affect the inside. \”Somehow it\’s more disturbing to have a singularity in the past that can affect everything in the outside world,\” said James Bardeen, a black-hole pioneer and professor emeritus at the University of Washington.

https://www.space.com/white-holes.html#:~:text=White%20holes%20are%20theoretical%20cosmic%20regions%20that%20function%20in%20the,collapsed%20star%20brethren%2C%20black%20holes.

@heckbasket