# What is Singularity: Definition and 428 Discussions

A gravitational singularity, spacetime singularity or simply singularity is a location in spacetime where the density and gravitational field of a celestial body is predicted to become infinite by general relativity in a way that does not depend on the coordinate system. The quantities used to measure gravitational field strength are the scalar invariant curvatures of spacetime, which includes a measure of the density of matter. Since such quantities become infinite at the singularity point, the laws of normal spacetime break down.Gravitational singularities are mainly considered in the context of general relativity, where density apparently becomes infinite at the center of a black hole, and within astrophysics and cosmology as the earliest state of the universe during the Big Bang/White Hole. Physicists are undecided whether the prediction of singularities means that they actually exist (or existed at the start of the Big Bang), or that current knowledge is insufficient to describe what happens at such extreme densities.General relativity predicts that any object collapsing beyond a certain point (for stars this is the Schwarzschild radius) would form a black hole, inside which a singularity (covered by an event horizon) would be formed. The Penrose–Hawking singularity theorems define a singularity to have geodesics that cannot be extended in a smooth manner. The termination of such a geodesic is considered to be the singularity.
The initial state of the universe, at the beginning of the Big Bang, is also predicted by modern theories to have been a singularity. In this case, the universe did not collapse into a black hole, because currently-known calculations and density limits for gravitational collapse are usually based upon objects of relatively constant size, such as stars, and do not necessarily apply in the same way to rapidly expanding space such as the Big Bang. Neither general relativity nor quantum mechanics can currently describe the earliest moments of the Big Bang, but in general, quantum mechanics does not permit particles to inhabit a space smaller than their wavelengths.

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1. ### B What is the actual shape of black holes?

When looking at depictions of black holes, we often get illustrations of a two-dimensional space-time where everything spirals into a "hole". The hole then leads to a singularity usually depicted as a funnel shape. Then there are images of black holes shown as spherical with glowing rings...
2. ### B Where does the original singularity get its energy from?

Where does the original singularity get its energy from?
3. ### I Incomplete geodesics in a singularity, do they warrant quantum concerns?

Question: The idea of a continuum breaks down for a singularity when a geodesic become incomplete (the breaking of the idea that there was a continuous succession, where no part could be distinguished from neighboring parts, except by arbitrary division), and so with that does this indicate a...
4. ### I Black hole singularity, a time-like surface?

Below is the description from the book. I thought that hyperbolas in the right quadrant are time-like and hyperbolas in the upper quadrant are space-like. If it were so, the surface ##r=0## would be space-like, but the book says otherwise. -- ?
5. ### I Do any real macroscopic black holes have a singularity?

Here's my reasoning. The event horizon is the point where the escape velocity becomes greater than the speed of light. This results in the event horizon spacetime boundary having infinite time dilation. So, that must mean that inside the boundary of the event horizon, time dilation must...
6. ### I Same state as in the Big Bang in a collapsing universe?

Suppose the universe were to eventually collapse in a Big Crunch [1]. How closely could the universe's final moments resemble those at the beginning of the universe? Could the universe return to its original state exactly in some kind of "Big Crunch" or "Big Bounce" model? [1]...
7. ### B Easy derivative but with a pesky singularity

Setting: a plane with the standard Cartesian coordinate system. A particle is constrained to the x axis, with position x and moving at speed x dot. Another particle is constrained to the y axis, with position y and moving at speed y dot. The distance between them at any moment is s. It is...
8. ### B Spagettification and a singularity

a singularity is assume to be a point without dimensions. When 2 mass particles fall into a black hole in the direction of the centre and separated by small distance, the particle closest to the center will have an acceleration as seen from the other particle as I understood. so distance between...
9. ### A Can an Oscillating Eternal Universe be Described without Singularity?

Consider the FLRW metric. We pick a specific definition for the scale factor as suggested bellow. Suppose we have a hypothetical metric having the scale factor defined by ## a(t)=\sin(t) (1+ \text {sgn}(\sin(t)) +\epsilon ## Does this make sense, mathematically (and physically)? Like having...
10. ### I Question about the big bang singularity

In big bang theories where our universe begins from a singularity (ignoring other theories just now), what would happen if the universe didn't begin as a single point but rather began as energy in an uneven shape? Would we be able to tell from the way the universe is now? Do we know that if the...
11. ### I Being at the position of a singularity before it is formed

Suppose we have a large sphere with thin non rotaring surface of floating iron particles (to prevent that they start a chain reaction making a star instead of a black hole) with a total mass sufficient to form a black hole. with an observer in the center of the sphere. This means the sphere...
12. ### I Black hole singularity vs. quantum mechanics

I'm wondering about some aspects about black holes (BH) and singularities, but since all my questions have to do mostly with quantum mechanics, I placed this thread in here. OK, let's assume there IS a singularity in the middle of a BH. A) Pauli exclusion principle (PEP) says no two fermions...
13. ### A Dustball Collapse & Evaporation: No Black Hole Singularity

This old nut is often dismissed as flawed thinking by a naive student. It’s been discussed here too, I know. However, when you do the math in standard (Schwarzschild-like) coordinates: Dustball collapse and evaporation in standard coordinates (Arxiv) A. the (coordinate) speed of light...
14. ### A Merger of Extremal BHs Causes Naked Singularity?

Let's say you have two extremal black holes containing the maximum amount of possible charge. Now let's say they're orbiting each other such that they will eventually merge. As the black holes merge they are producing gravitational waves. Once the merger is complete the new black hole mass will...
15. ### I Does Time Drive Black Hole Travelers to a Central Singularity?

Since my understanding of these geometries is wrong, I'll do this in numbered steps - the easier to correct my logic. I think the big problem I have is with the time dimension. There seems to be a presumption that the time vector will drive a falling object into a central singularity. But how...
16. ### I Schwarzschild Metric Singularity: Why?

Why does the Schwarzschild metric have a singularity at r=0 if it is only valid outside the spherically symmetric static mass?
17. ### B GR and closeness to a black hole singularity

Assume a Schwarzschild black hole. Near the event horizon other than Hawking radiation the behavior of matter and energy are fairly accuratly described by general relativity. How close can one get to the center (the singularity based on GR) before one must switch to a quantum gravity theory...
18. ### I Exploring Spacetime Interval at a Singularity: Tad Williams' Otherland

Tad Williams’ Otherland series has a scene where the characters are drawn to a temple no matter which direction they try to walk, as if space itself is curved. This is kind of the intuition I get when a physicist talks about the spacetime interval kind of flipping past an event horizon: if you...
19. ### I Proper time to reach the singularity of a Schwarschild black hole

When calculating the proper time along a timelike radial geodesic, with the initial condition that object the starts at rest at some Schwarzschild coordinate ##r_0>r_S##, i.e. \frac{\mathrm{d}r}{\mathrm{d}\tau}\Bigg|_{r=r_0}=0\;, after using the equations of motion one finds...
20. ### I How does the Singularity produce all the diverse matter in the universe?

How does the Singularity produce all of the diverse matter and properties that we observe in the Universe today? Although Theories like Quantum Gravity have somewhat produced indications about the existence of Graviton particles and allow some form of Gravity to operate within the laws of...
21. ### Determining a parameter so that it's a removable singularity

So, for this exercise I'm considering the removable singularity for ##x=2## to cause ##f(2)## to be different from ##\lim_{x \to 2}f(x)##. But as soon as I write everything down, I get stuck here: ##\lim_{x \to 2}f(x)\neq\frac{4(a-4)}{0}## How do I calculate ##a##?
22. ### I Cauchy Integral Formula with a singularity

Dear Everyone, I am wondering how to use the integral formula for a holomorphic function at all points except a point that does not exist in function's analyticity. For instance, Let f be defined as $$f(z)=\frac{z}{e^z-i}$$. F is holomorphic everywhere except for $$z_n=i\pi/2+2ni\pi$$ for all...
23. ### B Do things that fall into black holes ever reach the singularity?

A Paradox of the black hole is that GR states the stationary observer experiences time dilation, while the inflating observer experiences no time dilation. By the time the infalling observer reaches the event horizon, an infinite amount of time passes for the other frame of reference. But...
24. ### B Descending a Rotating Black Hole: Hit the Ring Singularity?

So I have been watching the latest edition of PBS Space Time ( I know, not a proper resource/guide,) and it seems to be a bit confusing as to whether you would hit the ring singularity at the center or not. On the one side he claims that the geodesics end there but on the other he claims you...
25. ### I Could Quantum Physics explain the singularity in a Black Hole?

If a singularity exists in the center of a black hole, could quantum physics, instead of relativity , explain it?
26. ### I Big Bang singularity: can we say anything about its size?

The Big Bang is sometimes described as started from a singularity, which I have interpreted as meaning that its characteristics are undefineḍ. If that is the case, can we not even say that the Universe as a singularity was still infinite? Otherwise we are implying that the singularity was...
27. ### I Penrose Singularity: Trapped & Anti-Trapped Surfaces Explained

As I understand Penrose proved there must a be a singularity using certain assumption for black holes and something called a "trapped surface:. Can anyone give a lay person explanation of what this and "anti trapped surface" are? How were they used in the singularity theorems and what was new...
28. ### I Who was the first to find an initial singularity in GR models of the universe?

I have a question about the history of cosmology, hope its okay to ask here. Who was the first person since Einstein's Gr to point out a singularity in cosmology? I know Freidman talked of an expanding universe and Lematire a primeval atom. But were there any explicit mentions of the density of...
29. ### I Planck Length & Singularity: Point or Sphere?

Since Planck length is a distance unit of space-time which cannot be further subdivided, would that not imply that an electron, or singularity, or any other point particle cannot actually be a “point”, but must rather be a spherical volume with a Planck length diameter? i realize this may well...
30. ### I A Copenhagen solution of the black hole singularity problem

Due to strong gravitational tidal forces, any living observer will die and any macroscopic measuring apparatus will be destroyed before it reaches the black hole singularity at the center of a macroscopic black hole. Hence the black hole singularity cannot be observed, so from an experimental...
31. ### How to judge the singularity of a matrix in numerical method?

Summary: different methods give different results. They are not consistent. Summary: different methods give different results. They are not consistent. I use two different methods to detect whether a matrix is singular. The result of calculating the determinant of a 9-order square matrix is...
32. ### Determine the singularity type of the given function (Theo. Phys)

NOTE: Was not sure where to post this as it is a math question, but a part of my "Theoretical Physics" course. I have no idea where to start this and am probably doing this mathematically incorrect. given the function f(z) = cos(z+1/z) there should exist a singular point at z=0 as at z = 0...
33. ### I The Singularity and the Schwarzschild radius

A singularity would be: a location in spacetime where the gravitational field of a celestial body is predicted to become infinite by general relativity in a way that does not depend on the coordinate system. (wiki) If the threshold to get a singularity is reached then space-time curvature...

46. ### Coordinate singularity in Schwarzschild solution

Hi! I have the following problem I don't really know how to approach. Could someone give me a hand? The line element of a black hole is given by: ds^2=\Bigg(1-\frac{2m}{r}\Bigg)d\tau ^2+\Bigg(1-\frac{2m}{r}\Bigg)^{-1} dr^2+r^2\Big(d\theta ^2+\sin^2(\theta)d\phi ^2\Big) It has an apparent...
47. ### I Big Bang Singularity vs Black Hole Singularities

Is there a fundamental difference between the (speculative) understanding of a singularity arising from the creation of a black hole and the singularity which we think may have been at the origin of the Big Bang? Noteably, would there be two basic theoretical types of singularities...
48. ### B A Singularity in Semi-Classical physics too?

Hello. My question is based upon my (mis?)understanding of these two premises. 1. General Relativity breaks down when trying to describe the extreme conditions that are inferred to have existed in the very early universe. 2. According to this link...
49. ### Black hole vs mathematical singularity

What is the difference between mathematical singularity and black hole singularity[emoji780]
50. ### B Real-Life Demonstrations of Black Holes for Video

Hi, I am working on a video, and I was wondering if any of you knew of some real-life demonstrations I can do about black holes? So far I have the gravity well, and the balloon covered by foil that you crush to show same mass but denser. My video is about the anatomy of a black hole, so I cover...