<p>White holes are a theoretical construction of General Relativity.</p>

<p>Despite extensive searches, nothing has been found: not a supermassive white hole, not a stellar-sized white hole, nothing. Thus, the answer to your question is: on our current knowledge, they don't exist anywhere.</p>

<p>It is unclear how could they be formed. The geometry of the Kerr-solution (i.e. rotating black holes) suggests a white hole could exist on the "other side" of a black hole, but currently it is pure speculation.</p>

CC BY-SA 3.0
2016-11-18T19:22:17.883Z
@Logan Typically all hypotheses are allowed in physics, if they are falsifiable. This particular hypothesis lacks support in observations, therefore is falsified, at least as of now. As theory is only as relevant as much as it predicts future observations, any theory which predicts white holes needs to be adjusted, because as of now it is unscientific.
kubanczyk
CC BY-SA 3.0
2016-11-20T23:23:58.360Z
@kubanczyk I think "unscientific" is maybe hard word for them. The scientific SE sites use mainly "non-mainstream" for that. But, honestly, they are theories belonging to the mainstream physics, just as, for example, the Hawking-radiation. I wouldn't say they couldn't exist - what if they could, but there is no known process to create them?
peterh
CC BY-SA 3.0
2016-11-21T10:57:23.307Z
@peterh For Schwarzschild coordinate t<0 mainstream and non-mainstream physics observed that a black hole is a normal neutron star, hence r becomes undefined. It's a playful trick to mirror the r coordinate to the past white singularity when you do this in your brain. BUT the scientific method says not to use all the possible ideas, only these which are not (yet) trashed by the observations of reality. Either you adjust (with t>=0) or you are no longer in realm of scientific method (hence I wrote "unscientific"), but in the realm of people attached to the ideas they have in their heads.
kubanczyk
CC BY-SA 3.0
2016-11-21T12:42:09.463Z
@kubanczyk For t<0 there are extrapolations. Other extrapolations of the GR worked quite well, as we can read them in any popular GR book. Mainstream physicists are working on it since a long time (f.e. the Kerr-solution was discovered in 1963). Yes, popular sources are full with wormholes, Alcubierre-drives and similar. Well maybe they aren't really exact and clear. But Kerr's, Penrose's, Hawking's original papers are considered clear and okay by the mainstream. Note: even these sources play an important role in the popularization of the science.
peterh
CC BY-SA 3.0
2016-11-21T14:33:53.090Z
@peterh I agree these sources popularize beautiful mathematical ideas (and themselves). But I think they severely downplay observations and thus distract from the *scientific method*. It's significant how I feel you don't get the essence of my arguments.
kubanczyk
CC BY-SA 3.0
2016-09-05T07:02:38.660Z
Would the "other side" be the inside?
userLTK
CC BY-SA 3.0
2016-09-05T07:32:33.900Z
@userLTK In rotating BH, the singularity is not a point, but it is ring. If the BH is enough big, and your trajectory was choosen enough wisely, you can fall through this ring while you survive. Your worldline can be interpreted as if you would be fallen out in an alternate Minkowski-universe. There are good Penrose-diagrams describing this, so it is totally mainstream science, despite that most of them thinks it as too speculative, non-mainstream. After the CET worktime I will extend it with some references.
peterh
CC BY-SA 3.0
2016-09-05T14:03:08.910Z
I didn't even think it was a theory, i thought white holes were purely hypothetical at this point.
Logan
CC BY-SA 3.0
2016-09-05T15:47:42.043Z
@Logan Check [this](https://en.wikipedia.org/wiki/Penrose_diagram), particularly [this](https://en.wikipedia.org/wiki/Penrose_diagram#/media/File:PENROSE2.PNG)  - yes they are purely hypothetical, but they are valid solutions of the Einstein Field Equations, and thus they are mainstream physics/astronomy - be back soon. Maybe the topic is a little bit over-mystified by the popular media - I've learned from it from normal scientific sources and thus I was surprised why are they handled often as if it they would be phantasmagory. I think they are like the Hawking-radiation:
peterh
CC BY-SA 3.0
2016-09-05T15:53:36.313Z
@Logan from the theories it comes out, but there is no experimental proof, thus it remains in the hypothetical, but still mainstream physics area.
peterh
CC BY-SA 4.0
2019-01-29T05:24:39.200Z
For the laypeople reading this: The main points, as @peterh said, are - yes, there are solutions to some GR equations that look like white holes. No, they have never been observed in practice, not even as a hint. This is not unusual in science. Sometimes our equations have solutions that correspond to real objects, other times they don't. The rest is just personal preference.
Florin Andrei
CC BY-SA 4.0
2019-01-29T09:20:55.777Z
@FlorinAndrei I remember a young chemist saying that a not yet found element should exist with atomic mass between Gallium and Arsenium. He also estimated its properties. Others asked him, why he didn't order the elements in alphabetical order? It was so uncommon at the time, like ordering them by their atomic mass.
peterh
CC BY-SA 3.0
2016-09-04T15:35:43.123Z
2016-09-05T10:42:21.187Z
2016-09-05T10:42:21.187Z
peterh
<p>The idea of a 'super massive white hole' is sometimes discussed regarding GR,SR and the destination of material 'lost' in a black hole. Is there any good theoretical or observational evidence for these SWH, or are they merely metaphysical speculations?</p>

CC BY-SA 3.0
2016-09-04T09:12:37.757Z
I'm pretty sure there's no such thing, but if you post your video, that might make it slightly more answerable.    Question on whiteholes here:  http://astronomy.stackexchange.com/questions/134/what-is-a-white-hole?rq=1
userLTK
<cosmology><white-hole>
Is there anything like a supermassive white hole? How are they formed? And where are they present?
Darth Ewok
# Is there anything like a supermassive white hole? How are they formed? And where are they present?

(Asked by: username_0 on 2016-09-04)

The idea of a 'super massive white hole' is sometimes discussed regarding GR,SR and the destination of material 'lost' in a black hole. Is there any good theoretical or observational evidence for these SWH, or are they merely metaphysical speculations?

**Tags:** cosmology, white-hole

> **Comments:**
> **username_1**: I'm pretty sure there's no such thing, but if you post your video, that might make it slightly more answerable.    Question on whiteholes here:  http://astronomy.stackexchange.com/questions/134/what-is-a-white-hole?rq=1  

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## 1 answers

### Answer by username_2 on 2016-09-04. Score: 11

White holes are a theoretical construction of General Relativity.

Despite extensive searches, nothing has been found: not a supermassive white hole, not a stellar-sized white hole, nothing. Thus, the answer to your question is: on our current knowledge, they don't exist anywhere.

It is unclear how could they be formed. The geometry of the Kerr-solution (i.e. rotating black holes) suggests a white hole could exist on the "other side" of a black hole, but currently it is pure speculation.

> **Comments:**
> **username_1**: Would the "other side" be the inside?  
> **username_2**: @username_1 In rotating BH, the singularity is not a point, but it is ring. If the BH is enough big, and your trajectory was choosen enough wisely, you can fall through this ring while you survive. Your worldline can be interpreted as if you would be fallen out in an alternate Minkowski-universe. There are good Penrose-diagrams describing this, so it is totally mainstream science, despite that most of them thinks it as too speculative, non-mainstream. After the CET worktime I will extend it with some references.  
> **username_4**: I didn't even think it was a theory, i thought white holes were purely hypothetical at this point.  
> **username_2**: @username_4 Check [this](https://en.wikipedia.org/wiki/Penrose_diagram), particularly [this](https://en.wikipedia.org/wiki/Penrose_diagram#/media/File:PENROSE2.PNG)  - yes they are purely hypothetical, but they are valid solutions of the Einstein Field Equations, and thus they are mainstream physics/astronomy - be back soon. Maybe the topic is a little bit over-mystified by the popular media - I've learned from it from normal scientific sources and thus I was surprised why are they handled often as if it they would be phantasmagory. I think they are like the Hawking-radiation:  
> **username_2**: @username_4 from the theories it comes out, but there is no experimental proof, thus it remains in the hypothetical, but still mainstream physics area.  
> **username_3**: @username_4 Typically all hypotheses are allowed in physics, if they are falsifiable. This particular hypothesis lacks support in observations, therefore is falsified, at least as of now. As theory is only as relevant as much as it predicts future observations, any theory which predicts white holes needs to be adjusted, because as of now it is unscientific.  
> **username_2**: @username_3 I think "unscientific" is maybe hard word for them. The scientific SE sites use mainly "non-mainstream" for that. But, honestly, they are theories belonging to the mainstream physics, just as, for example, the Hawking-radiation. I wouldn't say they couldn't exist - what if they could, but there is no known process to create them?  
> **username_3**: @username_2 For Schwarzschild coordinate t<0 mainstream and non-mainstream physics observed that a black hole is a normal neutron star, hence r becomes undefined. It's a playful trick to mirror the r coordinate to the past white singularity when you do this in your brain. BUT the scientific method says not to use all the possible ideas, only these which are not (yet) trashed by the observations of reality. Either you adjust (with t>=0) or you are no longer in realm of scientific method (hence I wrote "unscientific"), but in the realm of people attached to the ideas they have in their heads.  
> **username_2**: @username_3 For t<0 there are extrapolations. Other extrapolations of the GR worked quite well, as we can read them in any popular GR book. Mainstream physicists are working on it since a long time (f.e. the Kerr-solution was discovered in 1963). Yes, popular sources are full with wormholes, Alcubierre-drives and similar. Well maybe they aren't really exact and clear. But Kerr's, Penrose's, Hawking's original papers are considered clear and okay by the mainstream. Note: even these sources play an important role in the popularization of the science.  
> **username_3**: @username_2 I agree these sources popularize beautiful mathematical ideas (and themselves). But I think they severely downplay observations and thus distract from the *scientific method*. It's significant how I feel you don't get the essence of my arguments.  
> **username_5**: For the laypeople reading this: The main points, as @username_2 said, are - yes, there are solutions to some GR equations that look like white holes. No, they have never been observed in practice, not even as a hint. This is not unusual in science. Sometimes our equations have solutions that correspond to real objects, other times they don't. The rest is just personal preference.  
> **username_2**: @username_5 I remember a young chemist saying that a not yet found element should exist with atomic mass between Gallium and Arsenium. He also estimated its properties. Others asked him, why he didn't order the elements in alphabetical order? It was so uncommon at the time, like ordering them by their atomic mass.  

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