<p>It would help to clarify your question on what exactly you mean by a 4th dimension.  Space-time for example is 4 dimensional everywhere, but it's 3 spatial dimensions and 1 time dimension.</p>

<p>Quantum theory allows for extra dimensions, but they're very small, smaller than an atom and impossible to measure by normal means.  CERN has looked for those folded dimensions but has found no evidence of them, and string theory defines 10 or 11 dimensions, most of them we can't see or measure, if they exist at all.</p>

<p>If you mean 4 spatial dimensions, then the answer is no, with a capital N.   There's no evidence that an extra spatial dimension would form in a black hole.  There's nothing in relativity that suggests that might happen.  An extra time dimension . . . probably not either, but it's fun to think about what 2 time dimensions would look like.</p>

<p>What happens inside a black hole is that one of the dimensions becomes like time.  It only moves in 1 direction, but that doesn't make it a 4th dimension, it just changes the nature of 1 of the dimensions.  </p>

<p>If you actually had a 4th dimension (and the book flatland discusses this in pretty good detail), but if you actually had that, very strange things can happen, for example, you can be flipped over, like flipping a card over, which can represent 2 dimensions, from face down to face up.  Your left side would become your right side.  Your heart would be on the other side of your chest and all the left handed molecules in your body would become right handed molecules, which would make your ability to absorb and use nutrients that you digest problematic.   It might even make things taste and smell different.</p>

<p>You can't tie your shoes in the 4th dimension, but even if you could, your shoes could slide off your feet, no matter how well you tied them.   Food could fall out of your stomach, not through one of the two normal exits, but it could just slip out, like a ball rolling off a table.   Anything not attached could slip apart.   Sex would be much more difficult.  Bolts and nuts could just move sideways and detach, unless there was some electrostatic charge keeping them in place, in fact, the pressure that forms natural between a screw and a nut might cause all nuts and bolts to fly apart at considerable velocity once you entered 4th dimensional space.</p>

<p>Two people could also stand in exactly the same place, just in a different 4th dimensional space.   That brings a whole new aspect to the how many people can you fit in this Volkswagen game, as you could fit theoretically any number of people in the same Volkswagen.   </p>

<p>A 4th spatial dimension is probably impossible, because it breaks too many rules and laws as we know them, and it's never been observed.</p>

<p>Black holes, by comparison, can do strange things like slow down time, and they aren't fully understood, but a 4th spatial dimension probably isn't possible, unless you mean at quantum distances, in which case . . . maybe.</p>

<p>Feel free to read this for a <a href="https://astronomy.stackexchange.com/questions/9919/is-a-black-hole-a-5-dimensional-vortex?rq=1">different approach to a somewhat similar question</a>.  </p>

CC BY-SA 4.0
2019-03-05T14:28:27.240Z
What *would* an extra time dimension look like...?
BenjaminF
CC BY-SA 4.0
2019-03-05T21:36:47.160Z
@BraydenFox   Oh dear.   I put my foot in it this time.    I don't really know what it would be like.   I remember Neil deGrass Tyson talking about a 2nd time dimension in an interview so I threw it in my answer.   I'm not sure it's even possible and I tossed it in as more for creative writing than trying to identify a real thing.   Fun to think about though.   If you google "2 time dimensions" you get some real answers, but that wasn't really what I was going for.
userLTK
CC BY-SA 4.0
2019-03-04T20:09:34.213Z
2019-03-05T08:09:58.843Z
2019-03-05T08:09:58.843Z
userLTK
<p>Is a black hole a three dimensional or four-dimensional hole?</p>

CC BY-SA 4.0
2019-03-04T18:20:06.503Z
Hi, user26136, and welcome to Astronomy Stack Exchange! Please be aware that we ask that users [put only one question per post](https://meta.stackexchange.com/q/39223/274942), unless both are very closely related. I've edited your question to remove the second bit about a pulsar's rotation. Feel free to ask it as a separate question, although to be honest, I think [this answer](https://astronomy.stackexchange.com/a/19928/2153) should answer that question - it boils down to conservation of angular momentum.
HDE 226868
CC BY-SA 4.0
2019-03-04T18:29:51.617Z
No.   Which is to say, there's a capture radius but theoretically the hole itself is a point singularity.  And BTW we don't yet admit the existence of a fourth spatial dimension.
Carl Witthoft
CC BY-SA 4.0
2019-03-04T20:31:35.603Z
In short: it is a 3D object. It doesn't look like a hole. It looks like a sphere. The hole is only an analogy.
peterh
CC BY-SA 4.0
2019-03-05T08:03:26.640Z
@Carl Witthoft : I don't admit the existence of a point singularity.
John Duffield
CC BY-SA 4.0
2019-03-06T06:39:24.650Z
I'll vote to reopen now that the question has been improved. In its new form I think it's both narrow and clear.
uhoh
<black-hole>
Is a black hole a three-dimensional or four-dimensional object?
user26136
# Is a black hole a three-dimensional or four-dimensional object?

(Asked by: username_0 on 2019-03-04)

Is a black hole a three dimensional or four-dimensional hole?

**Tags:** black-hole
> **Comments:**
> **username_1**: Hi, user26136, and welcome to Astronomy Stack Exchange! Please be aware that we ask that users [put only one question per post](https://meta.stackexchange.com/q/39223/274942), unless both are very closely related. I've edited your question to remove the second bit about a pulsar's rotation. Feel free to ask it as a separate question, although to be honest, I think [this answer](https://astronomy.stackexchange.com/a/19928/2153) should answer that question - it boils down to conservation of angular momentum.  
> **username_2**: No.   Which is to say, there's a capture radius but theoretically the hole itself is a point singularity.  And BTW we don't yet admit the existence of a fourth spatial dimension.  
> **username_3**: In short: it is a 3D object. It doesn't look like a hole. It looks like a sphere. The hole is only an analogy.  
> **username_4**: @Carl Witthoft : I don't admit the existence of a point singularity.  
> **username_5**: I'll vote to reopen now that the question has been improved. In its new form I think it's both narrow and clear.  

---

## 1 answers

### Answer by username_6 on 2019-03-04. Score: 3

It would help to clarify your question on what exactly you mean by a 4th dimension. Space-time for example is 4 dimensional everywhere, but it's 3 spatial dimensions and 1 time dimension.

Quantum theory allows for extra dimensions, but they're very small, smaller than an atom and impossible to measure by normal means. CERN has looked for those folded dimensions but has found no evidence of them, and string theory defines 10 or 11 dimensions, most of them we can't see or measure, if they exist at all.

If you mean 4 spatial dimensions, then the answer is no, with a capital N. There's no evidence that an extra spatial dimension would form in a black hole. There's nothing in relativity that suggests that might happen. An extra time dimension . . . probably not either, but it's fun to think about what 2 time dimensions would look like.

What happens inside a black hole is that one of the dimensions becomes like time. It only moves in 1 direction, but that doesn't make it a 4th dimension, it just changes the nature of 1 of the dimensions.

If you actually had a 4th dimension (and the book flatland discusses this in pretty good detail), but if you actually had that, very strange things can happen, for example, you can be flipped over, like flipping a card over, which can represent 2 dimensions, from face down to face up. Your left side would become your right side. Your heart would be on the other side of your chest and all the left handed molecules in your body would become right handed molecules, which would make your ability to absorb and use nutrients that you digest problematic. It might even make things taste and smell different.

You can't tie your shoes in the 4th dimension, but even if you could, your shoes could slide off your feet, no matter how well you tied them. Food could fall out of your stomach, not through one of the two normal exits, but it could just slip out, like a ball rolling off a table. Anything not attached could slip apart. Sex would be much more difficult. Bolts and nuts could just move sideways and detach, unless there was some electrostatic charge keeping them in place, in fact, the pressure that forms natural between a screw and a nut might cause all nuts and bolts to fly apart at considerable velocity once you entered 4th dimensional space.

Two people could also stand in exactly the same place, just in a different 4th dimensional space. That brings a whole new aspect to the how many people can you fit in this Volkswagen game, as you could fit theoretically any number of people in the same Volkswagen.

A 4th spatial dimension is probably impossible, because it breaks too many rules and laws as we know them, and it's never been observed.

Black holes, by comparison, can do strange things like slow down time, and they aren't fully understood, but a 4th spatial dimension probably isn't possible, unless you mean at quantum distances, in which case . . . maybe.

Feel free to read this for a [different approach to a somewhat similar question](https://astronomy.stackexchange.com/questions/9919/is-a-black-hole-a-5-dimensional-vortex?rq=1).

> **Comments:**
> **username_7**: What *would* an extra time dimension look like...?  
> **username_6**: @BraydenFox   Oh dear.   I put my foot in it this time.    I don't really know what it would be like.   I remember Neil deGrass Tyson talking about a 2nd time dimension in an interview so I threw it in my answer.   I'm not sure it's even possible and I tossed it in as more for creative writing than trying to identify a real thing.   Fun to think about though.   If you google "2 time dimensions" you get some real answers, but that wasn't really what I was going for.  

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