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Tue Jun 11, 2019, 07:14 PM

White Holes: Black Holes' Neglected Twins


White Holes: Black Holes' Neglected Twins

https://www.space.com/white-holes.html


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.

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 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.





"It took 40 years to understand black holes, and it's only recently that people have been focusing on white holes," Rovelli said.

The Event Horizon Telescope, a planet-scale array of eight ground-based radio telescopes forged through international collaboration, captured this image of the supermassive black hole in the center of the galaxy M87 and its shadow.




While general relativity describes white holes in theory, no one knows how one might actually form. A black hole cordons off its bit of space when a star collapses into a tiny volume, but playing this video backwards doesn't make physical sense. An event horizon exploding into a functional star would look a bit like an egg unscrambling itself — a violation of the statistical law demanding that the universe gets messier over time.

Even if large white holes did form, they probably wouldn't hang around too long. Any outgoing matter would collide with the matter in orbit, and the system would collapse into a black hole. "A long-lived white hole, I think, is very unlikely," said Hal Haggard, a theoretical physicist at Bard College in New York.





For a while, white holes seemed to share the fate of wormholes — mathematically permissible contortions of space-time likely prohibited by reality. But in recent years, some physicists have brought white holes back in an attempt to save their darker siblings from an unseemly death.

Ever since Stephen Hawking realized in the 1970s that black holes leak energy, physicists have debated how the entities could possibly shrivel up and die. If a black hole evaporates away, many ask, what happens to the internal record of everything it swallowed? General relativity won't let the information out and quantum mechanics forbids its deletion.

"How does a black hole die? We don't know. How is a white hole born? Maybe a white hole is the death of black hole," Rovelli said. "The two questions join nicely, but you have to violate the general relativity equations in the passage from one to the other."





Such a microgram-size white hole, being similar in mass to a human hair, would have none of the gravitational drama of its black hole ancestor, according to Haggard, but would hide a cavernous interior containing the information of everything it had swallowed in its previous life. Too small to attract orbiting matter, the white hole might remain stable enough to eventually spit out all the information accumulated by its forerunner.

In this picture, white holes would one day come to dominate the universe, after the stars have burnt out and black holes have withered. Any observers then could easily detect the objects as relatively large particles Haggard speculates, but those days are countless trillions of times the current age of the universe in the future. "It's the craziest time scale I've seen in physics," Haggard said.

The ultimate white hole

Alternatively, the aftermath of a white hole may exist everywhere. To black hole physicists, the Big Bang's explosion of matter and energy looks like potential white hole behavior. "The geometry is very similar in the two cases," Haggard said. "Even to the point of being mathematically identical at times."



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Arrow 11 replies Author Time Post
Reply White Holes: Black Holes' Neglected Twins (Original post)
bobsal Jun 11 OP
Da Mannn Jun 11 #1
sipow Jun 11 #2
CornFed Jun 11 #3
Currentsitguy Jun 12 #4
SatansSon666 Jun 12 #5
Currentsitguy Jun 12 #6
SatansSon666 Jun 12 #7
Currentsitguy Jun 12 #8
SatansSon666 Jun 13 #9
Currentsitguy Jun 13 #10
SatansSon666 Jun 14 #11

Response to bobsal (Original post)

Tue Jun 11, 2019, 10:14 PM

1. It's OK to be White.

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Response to bobsal (Original post)

Tue Jun 11, 2019, 10:48 PM

2. Black Holes Matter

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Response to bobsal (Original post)

Tue Jun 11, 2019, 11:03 PM

3. I studied black holes in college

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Response to bobsal (Original post)

Wed Jun 12, 2019, 01:14 AM

4. Want to know what it's like inside a black hole? Look around.

The Universe is a closed system in which nothing can escape. It is finite, but unbounded. Depending on which theory you subscribe to (String or M Theory) we are a 3 dimensional bubble existing in an 11 or 12 dimensional multiverse.

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Response to Currentsitguy (Reply #4)

Wed Jun 12, 2019, 08:23 AM

5. Universe is an isolated system.

As far as we can tell anyway.
If it was a closed system it could exchange energy with another system.

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Response to SatansSon666 (Reply #5)

Wed Jun 12, 2019, 09:07 AM

6. Ah! But there is some evidence we DO exchange with other systems

Google the term Great Attractor. There is a segment of the Universe the seems to be pulled toward "something". The problem is there does not seem to be anything there that would be capable of exerting the gravitational force necessary. One theory is what is doing the exerting is a significant amount of mass in an adjoining Universe. This would be evidence gravity is capable of traversing the space "between" universes.

It's a little difficult to get your head around the concept of "between" since that is 11 or 12 dimensional space and we don't really do well conceptualizing anything beyond 3 dimensions.

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Response to Currentsitguy (Reply #6)

Wed Jun 12, 2019, 09:15 AM

7. The great attractor is still in our universe.

It is mysterious because we can't see it, but there are millions of galaxies beyond it wthin the confines of the observable universe.
We will eventually be able to see it, in about 30 million years or so as we spin around the galaxy, apparently.

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Response to SatansSon666 (Reply #7)

Wed Jun 12, 2019, 10:00 AM

8. What I cited is a competing theory.

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Response to Currentsitguy (Reply #8)

Thu Jun 13, 2019, 05:15 PM

9. Yeah, but it doesn't mean it isn't part of our universe.

They figure it's beyond the known universe and like it says that only means what we can see from the light that has been able to reach us.
It's a cool idea though.

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Response to SatansSon666 (Reply #9)

Thu Jun 13, 2019, 05:21 PM

10. This little exchange

Has prompted a two day long conversation with my wife on the subject. We were out for cocktails last night, sitting at the bar, discussing String and M theory. Needless to say no one struck up a conversation with us.

Geek love.

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Response to Currentsitguy (Reply #10)

Fri Jun 14, 2019, 11:50 AM

11. yeah. lol.

Not exactly a subject many people have a grasp on, let alone know a whole lot about. Myself included to an extent. Not something I have been particularly interested in.

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