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 ...
- 118k
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 ...
- 7,390
9
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 ...
- 1,569
7
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 ...
- 7,390
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 ...
- 14.5k
6
votes
Are black holes really singularities?
What is a singularity?
A singularity is a point in the universe where matter is infinitely dense. The singularity is at the centre of the black hole, and is often hiding behind an event horizon. So ...
- 647
5
votes
Accepted
Are black holes really singularities?
This answer is to some degree opinion-based. I share your scepticism about the existence of strict mathematical singularities as General Relativity would predict. This is mainly, because the ...
- 11.2k
5
votes
Do black hole singularities actually merge?
Infinities are hard to bend the mind around, but in this case, the merge is not impossible. Yes, the distance between them must reach zero in order to make the black holes merge, but the rate of which ...
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 ...
- 91.4k
4
votes
Are black holes really singularities?
I think you are starting off from the premise that there is some way of stabilising an extremely dense object inside the event horizon of a black hole. In the classical theory of General Relativity ...
- 118k
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 ...
- 220
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 ...
- 33.8k
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 ...
- 91.4k
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 ...
- 9,933
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,...
- 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 ...
- 9,933
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, ...
- 118k
2
votes
How can a naked singularity be possible?
Nobody likes the idea of naked singularities, as they would have a toxic effect on causality. If a singularity existed that was not separated from us by an event horizon, then not only would the ...
- 91.4k
2
votes
Are black holes really singularities?
It is common to describe a singularity as a point of infinite density, but really they are more general than that: they are some sort of pathological behaviour in the spacetime metric. Whether ...
- 1,795
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 ...
- 21
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)...
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 ...
- 2,525
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 ...
- 2,459
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 ...
- 1,423
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.
- 9,933
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. ...
- 28.3k
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}.
\...
- 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 ...
- 3,989
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