White holes: What we know about black holes' neglected twins
By Charlie Wood Contributions from Daisy Dobrijevic published February 24, 2022
White holes are returning to the experimental spotlight
White holes are theoretical cosmic regions that function in an opposite way to black holes. (Image credit: Future/Adam Smith)
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.
White holes were long thought to be a figment of general relativity born from the same equations as their collapsed star brethren, black holes. More recently, however, some theorists have been asking whether these twin vortices of spacetime may be two sides of the same coin.
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.
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.
More:
https://www.space.com/white-holes.html
= new reply since forum marked as read
There is still no evidence for white holes. Lots of speculation and theories, but no real evidence. Hardly fitting for a headline talking about "experimental spotlight" ... like they are setting up a white hole on a lab bench and poking at it. Yes, they're looking for evidence that the big bang was a white hole ... but it's still just speculation until they find something.
And for a bonus, the story includes my favorite (and widely repeated) misinformation about what's at the center of black holes:
This alleged infinitely dense point singularity is most likely a result of an error in General Relativity. There is no evidence for it. Black holes warp space enough that light cannot escape, that much is accepted. But what is at the center of a black hole is unknown.
General Relativity and Quantum Mechanics conflict, the math doesn't work. What is known is that both are wrong or rather incomplete. That the math of General Relativity produces a "singularity" at the center of black holes is just really good evidence that the theory is incomplete and we have no clue what's happening there. It's like proving "1 = 0" ... you know you've got an error someplace. Please do come back after there is a decent 'theory of everything" and try that math again. And if you still get an infinite density you might want to reconsider that new theory.
[Rant mode disabled]
Apologies for flaming, I just get triggered by news stories about unicorns popping out of worm holes because the math allows it.
And Judi -- thanks for your posts! Please don't consider my ranting as a complaint in your direction!
