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18 votes
Accepted

Are Buckyball-sized black holes possible?

A buckyball is about a nanometre ($10^{-9}$ m) across. If you limit the charge on the black hole to something like that of an electron or a few electrons, then this would mean the event horizon(s) of ...
ProfRob's user avatar
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14 votes
Accepted

What is a "Gentle Giant" Black Hole?

There's no "authoritative" definition, this is just the common meaning of the word "gentle" used in a popular science and science fiction context. A black hole might be gentle ...
James K's user avatar
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13 votes
Accepted

What created the big bang's singularity?

No one knows what came before the Big Bang if, indeed, anything did. Theories include: The Ekpyrotic universe theory where the BB was the result of the collision of branes. Various oscillating ...
Mark Olson's user avatar
  • 7,650
10 votes
Accepted

Singularities/ringularities and their properties

You need to be a bit cautious about statements like: A black hole contains a singularity at its center. It is a zero-dimensional point, and it's where all its mass is located. What you are referring ...
John Rennie's user avatar
  • 1,649
8 votes
Accepted

How can a singularity actually exist?

The answer is, of course, that a singularity can't exist. The fact that General Relativity predicts that singularities are inevitable under certain conditions is proof that GR is wrong. A singularity ...
Mark Olson's user avatar
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6 votes
Accepted

Black hole without singularity?

Does having an event horizon imply the existence of a singularity? An event horizon is not an inherent component of any given object. It's not like once a star turns into a black hole, it suddenly ...
zephyr's user avatar
  • 15k
6 votes

Can black holes even exist [if mass cannot be retained near the collapse threshold]?

A different way of looking at the issue: what properties would matter need to have to avoid imploding into a black hole if enough matter was gathered in a static sphere? The key thing about black ...
Anders Sandberg's user avatar
4 votes

How can a singularity actually exist?

As you say (although you phrase it slightly wrong), time slows down closer to the horizon, as seen from a distant observer. That means that, in the reference frame of a distant observer, matter never ...
pela's user avatar
  • 38.7k
4 votes

Is our universe a singularity?

A singularity isn't an object. It is a property of a differential equation. For example: $$t \frac{dx}{dt} + 2x= 0$$ This can be "solved" to give $x = \frac{C}{t^2}$, and given a value of $t$ and ...
James K's user avatar
  • 125k
4 votes

Fate of helium moving toward a singularity

I'll take the reference of an observer falling with the helium atom. At the Event horizon, the tidal force across a helium atom is still minute, $10^{-29}N$ much less than the Coulomb forces between ...
James K's user avatar
  • 125k
4 votes

Black hole without singularity?

Singularity means "my theory doesn't work here". In other words, GR is unable to predict what happens at the point, so it calls this point a singularity. The most important thing is not to mistake ...
kubanczyk's user avatar
  • 240
4 votes

Can black holes even exist [if mass cannot be retained near the collapse threshold]?

Gravity doesn't care at such extreme conditions. Yeah, I am definitely not joking. Friction, nuclear fission and whatever forces are there in the core of a massive dying star have no chance against ...
Alastor's user avatar
  • 2,668
3 votes

If space is negative energy and matter is positive energy then does that mean the universe is finite?

As everyone is saying, this is a very loose "plain English" version of some complex ideas, but if space was infinite, you could view this suggestion (that the overall total energy of the universe is ...
Steve Linton's user avatar
  • 10.3k
3 votes

Black hole without singularity?

A real neutron star would start to collapse when the strength of its gravity exceeds the strength of the neutron degeneracy pressure, before it has an event horizon. As you approach the event horizon,...
Robyn's user avatar
  • 191
3 votes

Why does kerr black holes have a ring shaped singularity rather than point?

Firstly do not confuse the event horizon with the singularity. Wikipedia gives the formulae for the Kerr metric. There are a number of places where this formula appears to break down because you ...
Steve Linton's user avatar
  • 10.3k
3 votes

Black hole without singularity?

The answer specifically about the question of a neutron star disappearing inside an event horizon but remaining in some sort of equilibrium is no. At least, it is no according to General Relativity, ...
ProfRob's user avatar
  • 155k
2 votes

Black hole without singularity?

A black hole could be any size. It could be the size of a planetary system. Given a specific distribution of matter, I think you don't necessarily need a singularity to be present. But given the fact ...
ClemyNX's user avatar
  • 21
2 votes

Black hole without singularity?

zephyr is right that you would need quantum gravity to really understand what happens inside event horizons. But the traditional description of what would happen inside the event horizon of a black ...
Mark Foskey's user avatar
  • 3,916
2 votes

Singularities/ringularities and their properties

A black hole contains a singularity at its center. It is a zero-dimensional point, and it's where all its mass is located. This isn't an established fact. A lot of people say they don't think there ...
John Duffield's user avatar
2 votes
Accepted

If a black hole pulls every object in the universe, why there is a light around it?

Well, you're partially correct here. A black hole traps everything inside its event horizon. Outside of the event horizon, matter (and energy) can still escape from its gravitational pull. This is due ...
sforsingh's user avatar
  • 1,443
2 votes
Accepted

What happens with the black hole's mass when a black hole disappears?

The mass (equivalently energy) is radiated away as Hawking radiation.
Steve Linton's user avatar
  • 10.3k
2 votes

If space is negative energy and matter is positive energy then does that mean the universe is finite?

In his book "Brief Answers to the Big Questions" completed by his colleagues after his death, Stephen Hawking does sort of mention that the negative energy created (along with equal amount of positive)...
Natthi Sharma's user avatar
2 votes

Does general relativity imply that singularities cannot exist?

Your understanding is incorrect. General relativity states that all matter in the universe is moving forward through spacetime at the speed of light. You are talking about the four velocity here. ...
David Hammen's user avatar
  • 34.1k
2 votes

Are there non-smooth metrics for spacetime (that don't involve singularities)?

It's a basic assumption of general relativity that a tangent space must exist at every point on the manifold. Therefore, the metric needs to be $C^1$. But "smooth" normally means at least $C^...
benrg's user avatar
  • 3,860
1 vote
Accepted

In the case of heat death of our universe, would proton decay overtake the singularity decay due to Hawking radiation?

It's likely that the "existence of a proton" has no meaning inside the event horizon. But if it does somehow, and the protons eventually decay, that would be invisible outside the black-...
antlersoft's user avatar
  • 3,455
1 vote

Does black hole singularity really exists with respective to relative frame of reference?

The question is really about how to turn a loose question into something that has an answer; to some degree this is a logic and philosophy question rather than astronomy, so don't get surprised if it ...
Anders Sandberg's user avatar
1 vote

Velocity of ringularity

$$ K_\text{min}=2\pi\sqrt{a^2+3(ma^2)^{2/3}} \tag{1} $$ where the quantities $m$ and $a$, both of which have units of length, are defined by $$ m=\frac{GM}{c^2} \hskip2cm a=\frac{J}{Mc}. \...
gisol's user avatar
  • 149
1 vote

Why doesn't a singularity spin infinitely fast?

Your intuition is correct, as far as classical dynamics is concerned. The main problem, I think, arises in that you are referring to a strictly quantum mechanical phenomenon - what is the physical ...
Daddy Kropotkin's user avatar

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