Thought Experiments


Are White Holes Real?

Sailors have their krakens and their sea serpents. Physicists have white holes: cosmic creatures that straddle the line between tall tale and reality. Yet to be seen in the wild, white holes may be only mathematical monsters. But new research suggests that, if a speculative theory called loop quantum gravity is right, white holes could be real—and we might have already observed them.

Image: Flickr user C.P.Storm, adapted under a Creative Commons license.

A white whole is, roughly speaking, the opposite of a black hole. “A black hole is a place where you can go in but you can never escape; a white hole is a place where you can leave but you can never go back,” says Caltech physicist Sean Carroll. “Otherwise, [both share] exactly the same mathematics, exactly the same geometry.” That boils down to a few essential features: a singularity, where mass is squeezed into a point of infinite density, and an event horizon, the invisible “point of no return” first described mathematically by the German physicist Karl Schwarzschild in 1916. For a black hole, the event horizon represents a one-way entrance; for a white hole, it’s exit-only.

There is excellent evidence that black holes really exist, and astrophysicists have a robust understanding of what it takes to make one. To imagine how a white hole might form, though, we have to go out on a bit of an astronomical limb. One possibility involves a spinning black hole. According to Einstein’s general theory of relativity, the rotation smears the singularity into a ring, making it possible in theory to travel through the swirling black hole without being crushed. General relativity’s equations suggest that someone falling into such a black hole could fall through a tunnel in space-time called a wormhole and emerge from a white hole that spits its contents into a different region of space or period of time.

Though mathematical solutions to those equations exist for white holes, “they’re not realistic,” says Andrew Hamilton, an astrophysicist at the University of Colorado at Boulder. That is because they describe universes that contain only black holes, white holes and wormholes—no matter, radiation or energy. Indeed, previous research, including Hamilton’s, suggests that anything that falls into a spinning black hole will essentially plug up the wormhole, preventing the formation of a passage to a white hole.

But there’s a light at the end of the wormhole, so to speak. General relativity, from which Hamilton draws his predictions, breaks down at a black hole’s singularity. “The energy density and the curvature become so large that classical gravity is not a good description of what’s happening there,” says Stephen Hsu, a physicist at Michigan State University in East Lansing. Perhaps a more complete model of gravity—one that works as well on the quantum scale as it does on large ones—would negate the instability and allow for white holes, he says.

Indeed, a unified theory that merges gravity and quantum mechanics is one of the holy grails of contemporary physics. Applying one such theory, loop quantum gravity, to black holes, theorists Hal Haggard and Carlo Rovelli of Aix-Marseille University in France have shown that black holes could metamorphose into white holes via a quantum process. In July, they published their work online.

Loop quantum gravity proposes that space-time is made up of fundamental building blocks shaped like loops. According to Haggard and Rovelli, the loops’ finite size prevents a dying star from collapsing all the way down into a point of infinite density, and the shrinking object rebounds into a white hole instead. This process may take just a few thousandths of a second, but thanks to the intense gravity involved, the effects of relativity make the transformation appear to take much, much longer to anyone watching from afar. That means that minuscule black holes born in the infant universe could “now be ready to pop off like firecrackers,” forming white holes, according to a report in Nature. Some of the explosions astronomers thought were supernovae may actually be the wails of newborn white holes.

The black-to-white conversion could resolve a nettlesome conundrum known as the black hole information paradox. The notion that information can be destroyed is anathema in physics, and general relativity says that anything, including information, that falls into a black hole can never escape. These two statements are not at odds if black holes simply act as locked safes for any information they slurp up, but Stephen Hawking showed 40 years ago that black holes actually evaporate over time. That led to the disturbing possibility that the information contained within them could be lost too, triggering a debate that rages to this day.

But if a black hole instead turns into a white hole, then “all the information is recovered,” says Haggard. “We are quite excited about this mechanism because it avoids so many of the thorny issues that surround this discussion.”

The new work is preliminary, however, and it is far from clear whether loop quantum gravity is an accurate description of reality. The only glimpse we get of white holes might turn out to be those we model in labs and kitchen sinks. But Carroll says that’s okay. Just thinking about these possibly mythical cosmic creatures can improve physicists’ intuition, “even if the real world is messy and not like those exact situations,” he says. “That’s the way in which white holes are very useful.”

Go Deeper
Editor’s picks for further reading

Inside Black Holes
Physicist Andrew Hamilton is your guide on a visual journey inside a variety of kinds of black holes.

Nautilus: “White Holes” Could Exist—But That Doesn’t Mean They Do
Matthew Francis on white holes and their implications for the symmetry of time.

Ask an Astronomer: What is a white hole?
Astronomer Karen Masters provides an introduction to the physics of white holes.

Tell us what you think on Twitter, Facebook, or email.

Maggie McKee

    Maggie McKee is a freelance science writer focusing mainly on astronomy and physics. She worked at New Scientist as both a reporter and physical sciences news editor from 2003 to 2012 and in 2012 was one of the winners of the first European Astronomy Journalism prize. She studied physics at Grinnell College and science writing at the University of California, Santa Cruz, and now lives near Boston with her husband and a passel of four-legged friends.

    • ………

      I believe our entire Universe is the result of a Black hole in a Universe of higher dimensions collapsing and creating us, therefore black holes in our Universe may create others…..

      • yinkissyang

        There are some creative comments here. I might have to make a theory of the Universe.

        • ………

          I coulda sworn I read something like this years ago but if they want to act like it’s a new theory I guess I can still look for answers to my theories, they also explain the dark matter energy problems “why can’t we detect 80% of matter and energy in the Universe?” Answer= it’s technically not here….

          • Hominid

            What have been dubbed ‘dark matter & energy’ are INFERRED from a few observations and are the most plausible explanation to account for those observations. Dark matter IS “technically” there – and it’s up to scientists to discover its nature.

            • ………

              even though it reacts to and effects the matter in our Universe, it’s still seems to “not be here”, this is a theory so unless you have answers or a scientist who might, telling me what we already don’t know doesn’t discover anything………It’s an idea

            • Hominid

              Duh! What’s your point? There are phenomena (about five distinct observations so far) that suggest the observable matter doesn’t account for the amount of gravity necessary for those phenomena to occur. The presence of an as yet undetected source of gravity (dark matter) is the one hypothesis (NOT theory) that best explains ALL the observations. What do YOU suggest? That scientists stop trying to understand what’s going on? “Telling [you] what [you] don’t know” is PRECISELY the way discoveries are made. You’re scientifically illiterate.

            • ………

              Are you one of those people who just like to argue? you point out that it’s a Hypothesis and not a Theory but since they are synonyms it seems you’re the illiterate one, my theory explains several different phenomena but I could use a brain that went to college to look at my ideas, I can’t do the math to prove its feasibility, and this is my record, I won’t delete it, I learned from Lerner….

            • Hominid

              You’re incoherent.

            • ………

              I was wondering why that last comment was strangely free of hostility and insult…..welcome back human…couldn’t resist that last dig could you? Grammar was never my thing….

            • anonymous

              [Sorry “……..” but hypotheses and theories have specific definitions in science and are actually quite distinct. A hypothesis is an idea that needs to be tested. A theory is the highest level of fact in science and means that the hypothesis has been tested and proven several times over by different groups of scientists and even via different methods. Please don’t feel bad about confusing the two, it is a common error. The most important thing for all of us is that we remain fascinated by the universe and keep asking questions.]

            • Tempest

              Hey Moron, the highest is a scientific law, not a scientific theory

    • Michael

      Another galactic gob-stopper! from the scientists that brought us a universe that came from nothing and the absence of anything material, and vacuum of non existence! I think “Galactic Gob-Stopper!” fits the evolution theory of all that is! Choke on that one fellas and ladies!

    • different1

      What if when matter is consumed by a black hole, the breakdown in the existence of time causes the matter to be broken down into it’s most basic sub atomic particles and gets ejected at the start of time( the big bang) a White hole that created everything or just regurgitates what will be in a causal loop.

      • Eddy N.

        I’m so glad you suggested this alternative. It’s almost like, “Which came first, the chicken or the egg,” but on a much grander scale.

      • Curt

        please send me some of whatever you’re smoking.

        • The Movie Man

          Why does a theory that is out of the box have to imply smoking something? If in the 60’s someone had suggested that Star Trek tech would shape the world of the 21st century they would have scoffed the exact same way you are. But here are some examples of “outrageous” ideas that proved to be true or untrue as the case may be.
          1. The earth is the center of the universe = false
          2. The sun goes around the earth= false
          3. the earth is flat = false
          4. man will never fly = false
          5. Star Trek communicators – flip phones
          6. Star Trek medical monitors = we have them today
          7. Star Trek data pads = Ipad

          So you see saying something is impossible is just the result of a small mind that can’t think of a new way to make something happen.

          • Mike Melgaard

            You went too far.. he was joking =/

          • Русская мафия уборщик

            get a sense of humor

          • Mike

            Actually, the sun does go around the earth. With respect to the earth, of course.

            • robie


        • jdiz89


      • Xiox

        You know that is actually a really good one, it certainly would make a hell of a lot of sense wouldn’t it? Just puts some things in perspective.

      • Matt

        The Loop Quantum Gravity theory supports the theory of white holes, however, the theory of the big bang is not supported by the Loop Quantum Gravity theory. Einsteins theory traces back into the past infinitely. So that is very unlikely.

      • Silver

        Its almost like the ying and yang symbol… a black hole forms in a universe filled with existence, and a white hole forms in a universe of nothingness

      • samurai_with_sword

        I would like to extend the hypothesis. I believe that everything in physics is a circle (or a globe for that matter). Circle of life, round planets and stars. Aged rocks tend to become round. You can expand however you want, eventually you are going to circle back and there are infinite routes to circle back. You can circle around an atom, or you can circle around earth or you can circle around space and time. Virtually every thing circles back. Nature has a way of creating symmetry, if that symmetry is not apparent over a short distance, it still is a symmetry over a larger distance. Similar to that one article about chicken eye fluid having ‘Disordered hyper-uniformity’.

        If there is matter there is dark matter, if there is energy there is dark energy, if there are black holes, of course there are white holes. To me its not a question if dark matter, dark energy or white hole exists. I actually like these stuff, because they complete the symmetry in nature. It is just a matter of us finding out how it all connects and interacts with each other.

    • george belk

      I will have to ask my preacher man about this. He knows every thing. Of course you have to slip him some cash first, but he says amen brother and gives me the answer.

      • Googol

        How is this related to the article?

        • george belk

          ? What the hell article are you reading?

        • Christopher Suiters

          It is called a joke. Get over yourself

      • Zeitgeist21

        Go spout your ignorant atheist propaganda somewhere else, douchebag.

        • Notabeliever

          Really, that is the best your religious intelligent mind could come up with with

    • Ian Elliott

      We all come from white holes. They’re called our childhood neighborhoods.

    • kenny

      Black holes are blacks and white holes are whites?

      • samurai_with_sword

        Yes, in either case they both are A holes.

    • Wasif

      With too much forward leap in theoretical physics, science is dwelling more and more into intellectual masturbation without any practical significance, spending billions on theoretical research concerning white holes/ blue holes is completely pointless

      • Mike Melgaard

        Masturbating is REALLY fun though..

      • kaede

        I cry for the taxpayers’ money.

    • littleoysters

      the Answer to the Ultimate Question of Life, The Universe, and Everything, as you shuld realize by now, is 42. There, done, now let’s move on to the big stuff.

      • ………

        The age of God when he had his first PanGalactic bargle blaster and gave birth to the universe in the BIG BLECHHHH and away it went down the white hole….Flush…..

        • jdiz89


      • notabeliever

        love it…hitchhiker

    • Yachter

      Black Holes, White Holes, sounds racist to me

      • Mr. XX

        I beg to differ

        • me

          you are right he forgot the most important one!!!

          the troll hole:


      • crusty

        Are you thinking about black whores and white whores?

      • Mrbobofboblandia

        You forgot the dreaded MEXICAN HOLE!!!!!

        • Joe

          Really? -_-

      • jdiz89

        Haha thats so funny… you know what it does sound racist

    • mike

      Maggie is a pretty lady

    • Oicu

      It wasn’t that long ago when the existence of “Black Holes” we not thought to be real. Then they were the thing that was going to destroy the universe. Now they are the savior of the universe.
      Now we have ‘White Holes.” Are they real? Are they going to destroy our universe, save it, or turn out to be where God has been hiding?

    • RickMH
    • clerickolter .

      Odds are if these are real they would have to be ancient since Space and Time warp around them until I suspect they pop off all the energy and matter they collected I suspect we will believe them when they see one, which should stand out like nothing else in the observable universe.

    • Tarso

      The input is a black hole and the output is a white hole. But it is the same hole, Isn’t it ?

    • Matthew

      What if all suns/stars are the white holes. Emitting all the information the black hole it is entangled with engulfs. Hmm….just a thought.

      • samurai_with_sword

        Suns/Stars are NOT white holes. They are suns/stars.

    • Randomness

      I wander if they will ever find the 50 sades of grey holes?

    • Randomness

      I wander if they will ever find the 50 shades of grey holes?

    • nammfats

      In theory every black hole is a white hole… but it all has to do with scale. Get small enough at the exact center of the black hole, then all the incoming matter into the black hole looks like matter coming out of a white hole. It’s all a matter of scale and perspective.

      • samurai_with_sword

        When you are talking about space and time, small from your point of view may not necessarily be small. Once you cross the event horizon, may be the whole outside universe looks like a point to you and everything inside the event horizon may look large like a universe to you. So an event horizon might be a flat infinite surface which from either side looks round and from one side it is a black-hole and from the other side, it is a white hole.

      • PartyCannon


    • bill_josby

      glory holes are much more mysterious

      • Mike Melgaard

        I am dying from this comment right now. Great work.

    • The Movie Man

      Here is my take, these “Holes” are nothing more than channels between different universe’s. The black holes on our side pull mater in that is shot out on the other side through a white hole, and the white holes on our side are shooting out matter that was pulled into a black hole in another universe.

    • deutsch

      If there exists black holes and white hole, then there should be grey holes (came before white hole discovered.). Remember that black holes and white holes exhibit opposite polarity and they will cancel out once met in order to create grey holes. Once they are found, there may be yellow hole somewhere nearby. That’s our next quest.

      • samurai_with_sword

        grey holes are everything in between black holes and white holes, which is space, planets and stars. duh.

        • PartyCannon

          U NEVER KNOW

      • PartyCannon

        Whats yellow holes got to do with any of dis

    • jason

      If black holes eventually absorb all matter. There will be nothing to fuel the rotation. And true nothing or true space would rip the mono-poles out at its weakest point. This could potentially happen if a black holes had an insufficient amount of protons to absorb.

    • ImpStout

      I would think if this theory is fact that observational data should be out there. None is offered in the article even though it suggests that we “may have already observed” in the first paragraph.

    • Kenneth Meth

      Maybe the white hole is what is at the other end of black holes, an vice versa.

    • Middle Class Warrior

      I think our universe IS a White Hole in some other Universe’s Black Hole. That mother Universe would be a White Hole from a previous universe’s Black Hole and so on . As well as Our Black Holes being White Holes/Universes containing black holes that are white hoes/universe… … Kinda Fractal like

      • Middle Class Warrior

        Kinda evolutionary too… Life has many fractal features too…

    • Todd1

      The aliens visited in Carl Sagan’s novel Contact created a white hole at the center of the universe to slow the pace of universal expansion.

      Assuming for a moment that gravity doesn’t act fundamentally differently in black holes or, more generally, in areas of high matter density, how could white holes exist? Gravity draws matter closer together, not farther apart. Of course, this is the central conundrum of the big bang as well…that being, what event or reaction is strong enough to break the hold of that much gravity?

      Imagine a ball-bearing tied to the end of an elastic string. After releasing the ball it accelerates to the midpoint of its motion then decelerates to a momentary stop at full length. For black holes to have corresponding white holes we could posit that the intense gravity of a singularity slingshots matter out through a white hole.

      Why does Hawking radiation mean that information is destroyed? A droplet of dye dispersing in a container of water has too many particles/variables for our computers to track the dispersion in reverse, but this doesn’t mean, with perfect knowledge of conditions, that this is not possible. Why is Hawking radiation different?

    • Hominid

      What I find most nettlesome about cosmology is the use of work-a-day terms as technical terms without defining them or even acknowledging the practice.

    • ocdhickson

      Now wait a minute. Is the Hotel California a black hole?
      “You can check out anytime you like but you can never leave.”

      • jdiz89

        that is so true

    • seescaper

      Much of the dysfunctionality of current physics could be resolved by understanding the nature of the relationship between matter, space, and energy, and how the structure of the electron is related to the structure of the universe. Please view this link to the WSM theory of Dr. Milo Wolff:

    • seescaper
    • Mr. XX

      it makes sense. but where does string theory fit in?

      • Mr. XX

        If black holes have gravity and an event horizon, do white holes have antigravity and an inverted event horizon?

    • Vorador Gameman

      Having the universe start as a white hole explosion or ejection which created many black holes which will all consume everything and each other then the result will create a white hole repeating the process could be a theory

    • Bret Corey

      While the Einstein Big Bang theory could help to explain the beginning the spread of the universe it however dose not support the cold spots warm spots of other neighboring universes. However the quantum gravity white hole black hole theory would help to explain these cold spots warm spots as matter is sucked into a black hole condensed and then exponentially multiplied as it is shot back out… Thus reason behind the fact our universes cold as it is with warm spots like suns like sparks floating through a massive reaction space from being sucked into a black hole and shot back out same as our possible neighbor in universes mimicking the same actions thus why in theory why they can be detected at all because we are seeing the reaction of this equational process on a more ancient and much greater scale.

    • Cinapanina

      Isn’t that where we are right now, in a ‘white hole’, we all eventually have to leave and we can never come back?

    • Dan Lopez

      What if a white hole is just the back side of a black hole????

    • David

      Gravity is the question? The tug of war concept? As we know the universe is expanding at the speed of light continually this event horizon is theory, hypothetically beyond quantum explanation the thought is trained to disprove fact, light for instance is a fact, secondly where did it come from? Until man figures out this? Fact we have a long way to go! Not only from the front,present,and tommorow, light has moved in these distances hence the whence fact became present by observation. Things that are not are facts one diagram displayed this model only separated by atomic structures betwixed between sub atomic and what?particle? The seen and the unseen! Just because a fact is abstract and is unable to be observed with the naked eye! Simply doesn’t mean it’s not.

    • David Catron

      After reading the article I cant help but feel that white holes have been observed. That being said, they have not been observed on the steller scale. As im sure many of the readers know, the observations into the “center” of our galaxy point to a super massive black hole being at the core of our galaxy. Many scientists believe that this is the norm for many of our galactic neighbors. That being said, scientists have observed a phenomena in young galaxies know a quasar. Many have hypothesized them to be a smbh expelling all of the “ingested” matter and gases that the smbh took in during the initial forming of the galaxy. All that being said, it is entirely plausible that the singularity has what could be described as a “maximum capacity”. As the smbh reaches its maximum capacity it may change its gravitational flow to release the contents back into the universe in the form of a “white hole”. Im know that there are others out there with different views and opinions on this article. This is just my take on the article. Thank you.

    • Clifford Johnson

      Holy Moly.

    • Tristan

      What if thar coneted a black hole and a white hole

      • iKYFGoygOWBLO

        Um TYPO!!!

    • Science Lover

      White holes do exist. If all the matter in the universe was consumed by black holes, then there would be true nothingness, except black holes. Then the black hole would be so dense, containing all the matter of the universe, that it would no longer be able to contain the matter. So, it would explode, releasing all of its matter, energy, and information, as in the process of the Big Bang. Thus, black holes are just the beginnings of white holes; white holes evolve from over-condensed black holes.

    • PartyCannon

      This is soooo AMAZING!!!!!!!!!!!! I ❤️❤️❤️❤️❤️❤️❤️ Astronomy :):):):):):)

    • max_sportsman

      just ask this matter cant be destroyed so it goes somewhere why not on ther other side of that darkness have light

    • Clinton Walker

      So…. If black holes have an insane amount of gravity (allowing us to see them), wouldn’t white holes have an equally strong reverse force making then detectable?

    • Tyler Loper

      Ok so I’ve heard black holes destroy everything that goes in it. But matter can not be created nor destroyed. So therefore, black holes can not destroy things. Which I’m thinking that instead of “destroying” it could possibly be a wormhole and is sent somewhere else in the universe. But to where? My guess would be a white hole. Which could be the other end of a black hole where light and everything else is released. Now black holes are suppose to have a strong gravitational pull and could crush anything. But what if you had something that could neutralize the effect of the gravitational pull from crushing you. You could possibly go into a wormhole to somewhere else in the solar system.

    • “essential features: a singularity, where mass is squeezed into a point of infinite density” — Nope, that ain’t going to happen!

    • Captain Canada

      Yes they are. I know one. She lives next door. LOL.

    • robie

      now we have this new theory about firewalls so the matter is incinerated…

      way to bum us all out and doom any remote chance someone wants to go into one.

      ( ͡° ͜ʖ ͡°)