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  • A celebrated astrophysicist is intently studying  the skies in search of his elusive quarry,  

  • combing through the thousands of images coming  to him from the state-of-the-art International  

  • Event Horizon telescope. Finally, after months  and months of searching, he thinks he may have  

  • found what he's been looking for all this time  - in the images he sees the telltale signs of a  

  • mysterious phenomenon called a black hole. But  as he scrutinizes the images captured by the  

  • powerful telescope, something doesn't seem quite  right. There, right in front of his very eyes,  

  • the black hole appears to beburping!? The  scientist knows that this should be impossible:  

  • nothing can escape from a black hole, not even  light - that's why they're so hard to find - but  

  • here is photographic evidence of matter coming  out of a black hole! Could it be that this is  

  • not a black hole at all, but the black hole's  neglected twin - a white hole? Could this be his  

  • chance to once and for all answer the questions  that have been nagging at him throughout his whole  

  • career - What is a white hole? How do they formHow do they work!? And, do they even exist at all?

  • In 1915, Einstein's field equations turned  the world of physics on its head. His theory  

  • of relativity described the force of gravity  and shattered the prevailing paradigm of the  

  • nature of reality - rather than being rigidspace and time can actually bend and fold,  

  • along with the mass of stars and planetsWithin a year, scientists had calculated how  

  • space-time curves around a single ball of massthe seeds of what today is called the singularity.  

  • Physicists were able to describe how a spherical  mass shrunken down to infinitely dense point  

  • could wrap space around it so tightly  that a region of space is effectively  

  • pinched off from rest of universe, creating  a no-mans land beyond the event horizon where  

  • the laws of physics no longer apply and the  link between cause and effect is shattered.

  • A black hole is an incredibly dense  area of space where all matter has  

  • been squeezed into an impossibly tiny spacecalled the singularity. This creates such an  

  • intense gravitational pull that nothing, not even  light, can escape from the black hole's clutches.  

  • A tiny black hole might be the size of a single  atom, but have a mass equal to a large mountain.  

  • Stellar black holes, formed when a dying  star collapses in on itself in a supernova,  

  • can have a mass up to 20 times greater than  our sun. The largest black holes are called  

  • supermassive black holes, and they can be found  at the center of every galaxy in our universe. The  

  • supermassive black hole at the center of our Milky  Way galaxy, named Sagittarius A*, has as much mass  

  • as 4 million of our suns, all condensed intotiny ball only as big as a few million Earths.

  • A black hole's event horizon is what we would  consider the surface of the black hole, although  

  • it's not a surface in the true sense of the word  - it's not a membrane or barrier, but rather, the  

  • threshold beyond which there is no going back. The  event horizon is the point of no return - nothing  

  • that crosses the event horizon can ever come backEven light cannot escape the black hole once it's  

  • passed the event horizon. Once somethingor someone - has crossed the event horizon,  

  • they will begin the inevitable process of  falling towards the black hole's singularity,  

  • eventually dissolving into the singularity  itself. We can only guess what happens after that.

  • Physicists have been studying black  holes for decades and are only just  

  • beginning to understand them. Only recently have  

  • they turned their attention to the black  hole's neglected twin - the white hole.

  • From afar, a white hole would appear  identical to its better-known cousin,  

  • a black hole. Like a black hole, a  white hole might be big or small,  

  • might spin or remain stationary, and might be  electrically charged. A white hole would also  

  • be surrounded by a ring of dust, and a cloud of  gas and debris would gather at its event horizon.

  • The key difference between a black hole  and a white hole is that white holes burp.  

  • Yes, burp. Unlike a black holefrom which nothing can escape,  

  • matter actually can cross the event horizon and  come out of a white hole. It's only in these  

  • moments, when objects emerge from the white  hole, that scientists can definitively say  

  • that what they are looking at iswhite hole, and not a black hole.

  • If a black hole's event horizon is the point of  no return, then the event horizon of a white hole  

  • could be described as the point of no admission  - nothing can ever cross the event horizon of  

  • a white hole and reach the interior. In a black  hole, objects in the space outside can cross the  

  • event horizon and affect the interior of the black  hole, but matter inside the black hole can never  

  • again interact with space outside. In a white  hole, the reverse holds true - objects from inside  

  • the white hole can cross the event horizon and  interact with objects in the space outside of it,  

  • but nothing on the outside can ever enter  the white hole or affect the inside.  

  • This is because a white hole is a black  hole's time reversal, according to physicists.

  • A black hole's singularity exists in the futurewhereas a white hole's singularity exists in the  

  • past. Since the interior of the white hole is  cut off from the universe's past via its event  

  • horizon, no outside object or event will ever  affect the inside of a white hole. James Bardeen,  

  • a black hole pioneer and professor  emeritus at the University of Washington  

  • explains the magnitude of this difference:  “Somehow it's more disturbing to have a  

  • singularity in the past than can affect  everything in the outside world”, he says.

  • Scientists had theorized about the existence  of black holes for hundreds of years before  

  • Einstein's theory of relativity paved  the way for physicists to prove their  

  • existence - theoretically, at least. Since  no light escapes from a black hole, they are  

  • invisible to the naked eye. Until very recentlythe only way scientists have been able to find  

  • evidence of black holes has been to look for  signs of their impact on the surrounding universe.  

  • Stars, gasses and other space objects behave  differently near a black hole than they do  

  • elsewhere in the universe as the black hole's  intense gravity pulls on them. Using telescopes  

  • equipped with special tools, scientists can  pick up a type of high-energy light emitted  

  • by objects that interact with a black hole's  gravitational forces, and reverberation mapping  

  • can measure the radiation given off by the ring  of debris that surrounds the black hole, helping  

  • physicists pinpoint the location of a black holeeven if they can't see the black hole itself.

  • Finally, in 2019, scientists made a stunning  breakthrough in the study of black holes  

  • when the International Event Horizon telescope  captured the world's first image of a black hole.  

  • Technically, what they captured was the  black hole's shadow, since the absence of  

  • light reflecting from a black hole makes the black  hole itself impossible to see, but nevertheless,  

  • this was the world's first solid, photographic  proof of the existence of black holes.

  • If black holes have finally been proven to be  real, does that mean that white holes are a proven  

  • fact of the universe, too? Well, not exactlyWhile Einstein's theory of general relativity  

  • does describe the existence of both black and  white holes, it doesn't explain how a white  

  • hole might actually form in space. A black hole  forms when a dying star implodes in a supernova,  

  • collapsing all of the star's matter into an  impossibly tiny area cordoned off from the  

  • rest of space. The reverse doesn't quite make  sense - the idea of a white hole exploding into  

  • a fully-functioning star would be a bit like  unscrambling an egg: it just wouldn't work.  

  • This idea also violates the statistical  law that entropy must increase over time.

  • Furthermore, if a white hole did formthe matter it releases when itburps”  

  • would collide with the matter in orbit  around the white hole. These collisions  

  • would cause the entire system to collapse into  a black hole. Perhaps if white holes do exist,  

  • they don't remain as a white hole for long. Hal  Haggard, a theoretical physicist at Bard College  

  • in New York, has said that “a long-lived  white hole, I think, is very unlikely.”

  • Other scientists have different  theories about white holes that help  

  • explain some of the inconsistenciesSteven Hawking discovered back in the  

  • 1970s that black holes leak energy, which  led him to wonder - how do black holes die?  

  • And what happens to everything that's been  trapped inside of a black hole when it dies?  

  • The theory of general relativity holds that  nothing can get out of a black hole, but quantum  

  • mechanics prevents any information inside a black  hole from being deleted. So where does it go?

  • Some have taken this to mean that a white hole is  actually the result of the death of a black hole.  

  • As a black hole dies, it may become so  small - as small as one microgram in size,  

  • about the mass of a human hair - that it would no  longer obey the laws of physics as we know them.  

  • This infinitesimally tiny object would  be so small that it would defy gravity,  

  • but inside it would hide a cavernous  interior full of everything it swallowed  

  • in its previous life as a black holeIt's small size and gravity-defying  

  • behaviour could allow it to remain stable  enough to eventually spit out information  

  • and matter that had been swallowed by the black  hole, becoming a “burpingwhite hole instead.

  • If this theory holds true, the universe could  one day come to be dominated by white holes.  

  • After all of the stars in the universe have burnt  out and imploded into black holes, and then after  

  • all of those black holes themselves have all diedthe universe might be nothing but a sea of burping  

  • white holes. Thankfully, this could only happen  in a universe countless trillions of times older  

  • than our universe currently is, so it's notscenario we need to worry about any time soon.

  • There are many more questions than answers when  it comes to white holes, and that leaves room for  

  • plenty of imaginative theories about what a white  hole actually is. Some scientists actually think  

  • that we are currently living inside the ultimate  white hole. To these black hole physicists,  

  • the behavior of a white hole looks suspiciously  similar to a little thing we call the Big Bang.  

  • The explosion of matter and energy resulting  from the Big Bang that created our universe  

  • is remarkably similar to the way theorists  suspect that white holes release matter.

  • The geometry is very similar in the two cases,"  Hal Haggard, the physicist from Bard College, has  

  • said. "Even to the point of being mathematically  identical at times." This theory has attracted  

  • plenty of criticism, but Haggard intends  to follow this rabbit hole to the very end,  

  • sayingWhy wouldn't you investigate whether white  holes have interesting consequences? It may be  

  • that those consequences aren't what you expectedbut it would be foolhardy to ignore them.”

  • We may still be a long way off from being able  to look into a telescope and watch with our own  

  • eyes as a white hole burps out matter into the  surrounding universe. Although we've only just  

  • gotten our first glimpse of a black hole - and  though we have yet to even lay eyes on a white  

  • hole - scientists will undoubtedly discover more  about these mysterious phenomena in the future.  

  • If the past has taught us anything, it's  that just because we can't see something  

  • doesn't mean it isn't out there. Only time  will tell which theory about white holes  

  • will prove to be correct - or if we had it  completely wrong all along. One day we may  

  • get an answer to the questionWhat iswhite hole?” but until then, it remains  

  • yet another of the countless as-yet-unsolved  mysteries of our vast and unknowable universe.

  • If you thought this video was fascinatingyou'll definitely want to check outWhat  

  • Would Happen to Your Body in Space?”, oryou might like this other interesting one!

A celebrated astrophysicist is intently studying  the skies in search of his elusive quarry,  

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What Is a White Hole? (Opposite of Black Hole)

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    林宜悉 posted on 2020/11/15
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