A couple of questions about singularities

In summary, a cosmological singularity is a point in time when our mathematical equations can no longer describe the dynamics due to the presence of infinities and breakdown of processes. A gravitational singularity, such as a black hole, is a point-like singularity with infinite density, but we cannot know for sure as it is beyond the event horizon. There are mathematical tools, such as the Shwartzchild metric and thermodynamic equations, to describe these singularities. They do exist, but our understanding of them is limited by the limitations of our current physics. The Big Bang was not an explosion, but rather a hot dense beginning which expanded throughout the universe. Quantum mechanics has a minimum size, length, and energy level, known as
  • #1
twistor
74
8
Which is the difference between a cosmological and a gravitational singularity? Is there any mathematical tool that relates them? Do they REALLY exist or are they of a nature that simply escapes GR? How can the Big Bang and flatness of space coexist? Could the Big Bang be a local event? How does QM relate to singularities? Why didn't black holes form in the early universe?
 
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  • #2
I count seven questions, not two (a "couple"). :wink:
 
  • #3
jtbell said:
I count seven questions, not two (a "couple"). :wink:

lol

twistor said:
Which is the difference between a cosmological and a gravitational singularity??

A cosmological singularity is a time when our mathematics can no longer describe the dynamics. Prior to 10-43, we cannot desribe as the math involved no longer makes sense, to many infinities and processes. A Gravitational singularity such as a black hole is a point like singularity said to have infinite density. We do not know for sure as their is no way to measure beyond the event horizon of a black hole.

twistor said:
Is there any mathematical tool that relates them?
Their are a variety of mathematical methods to describe them, for a BH google Shwartzchild metric, For the Cosmological singularity its more involved in the thermodynamic equations of an ideal gas, and symmetry metrics

twistor said:
Do they REALLY exist or are they of a nature that simply escapes GR?
Black holes do exist, see the previous on Cosmological singularity
twistor said:
How can the Big Bang and flatness of space coexist?

Your obviously thinking of the big bang as some explosion. This is wrong, the big bang only describes a hot dense beginning, not some super particle that pop media programs would have you believe.
twistor said:
Could the Big Bang be a local event?
no the big bang occurred throughout all the universe. However the volume of the universe was smaller, we do not know if the universe was infinite or finite at that time, nor do we know the size now. We only know the observable portion of the universe.

twistor said:
How does QM relate to singularities?

QM has a minimum size, length and energy level called Planck units. As a consequence some of the infinity issues are avoided.

twistor said:
Why didn't black holes form in the early universe?

Primordial black holes did form in the early universe, how early we do not know for sure. This is a consequence of more material due to a denser intergalactic medium
 
  • #4
Mordred said:
lol



A cosmological singularity is a time when our mathematics can no longer describe the dynamics. Prior to 10-43, we cannot desribe as the math involved no longer makes sense, to many infinities and processes. A Gravitational singularity such as a black hole is a point like singularity said to have infinite density. We do not know for sure as their is no way to measure beyond the event horizon of a black hole.


Their are a variety of mathematical methods to describe them, for a BH google Shwartzchild metric, For the Cosmological singularity its more involved in the thermodynamic equations of an ideal gas, and symmetry metrics


Black holes do exist, see the previous on Cosmological singularity


Your obviously thinking of the big bang as some explosion. This is wrong, the big bang only describes a hot dense beginning, not some super particle that pop media programs would have you believe.
no the big bang occurred throughout all the universe. However the volume of the universe was smaller, we do not know if the universe was infinite or finite at that time, nor do we know the size now. We only know the observable portion of the universe.



QM has a minimum size, length and energy level called Planck units. As a consequence some of the infinity issues are avoided.



Primordial black holes did form in the early universe, how early we do not know for sure. This is a consequence of more material due to a denser intergalactic medium


Thank you a lot!
 
  • #5
I'd like to point out that parts of Mordred's post which referenced some minimum time or minimum units are really only educated guesses. The singularity for both the cosmological case, and the gravitational case occur only at one point (at t=0 for the cosmological case, and at r=0 for the gravitational case), it's just that we do not expect our physics to work well sufficiently close to these singularities (in physics we don't like to have true infinities in physical observables as would be the case if singularities really existed). The minimum time or minimum units are really just educated guesses on at what scales our currently understood physics will break down (where the "correct" physical results would be significantly different than our currently predicted results), and we have to apply new physics.
 
  • #6
hv = E = m(c^2)
hv = m(c^2)
Planck's constant multiplied by the frequency, divided by square of the speed of light (in a vacuum), gives the mass of the virtual/real particulate.
The highest frequency (v) available in quantum mechanics is defined by the Hansen constant as: sqrt[ C^5/(h-bar)G] which is 10^43 Hz.
In our 4-dim continuum and, because this number is derived from constants, this is absolute.
This posits that, at this frequency, mass and energy are in 'transit-phase' or metathesis.
The 'Hidden variables' that caused (as causality) the plenum to expand is, at this moment in time, more conjecture than theory.
String theory 'suggests' (within the math) that the plenum was a 'Planck-like' quantum object, of 10^-33 cm diameter, and not, as misused, a singularity.
A singularity is a dimensionless point (in space) Apart from the fact that there was not any space, in which a singularity could exist at the plenum,
(Space-time was created due to the expansion)
A quantum object with, almost vanishing size but not zero, appears to be the correct interpretation of a substantial 'singularity' within the meaning of the word used in the above context.
The 'BB' appears to have been an expansion not an explosion. Explosions throw their debris into something. There wasn't anything to explode into at the plenum.
Space-time was created with the expansion.
 
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  • #8
Mordred said:
Not sure if your aware of how to post math in Latex, Frank makes it easier to read for complex forms. This link explains how to do so
https://www.physicsforums.com/showpost.php?p=3977517&postcount=3

Now, I didn't know that!
I shall be having a field day once I get the hang of it.
Nice to find you here Mordred.
Seems as if QM is wrong about superposition in the macro-world.
We CAN be in 2n places at once!
Thanks for the latex thread.
I thought it prudent to reiterate my explanation I gave on the other forum.
I added a couple of lines to comply with the essence of the question/discussion.
 

Related to A couple of questions about singularities

1. What is a singularity?

A singularity is a point in space-time where the laws of physics break down and all known physical quantities become infinite. It is often associated with the center of a black hole, where the gravitational pull is so strong that even light cannot escape.

2. How are singularities formed?

Singularities are formed when a large mass collapses under its own gravitational pull. This can happen during the death of a massive star, leading to the formation of a black hole, or in the early stages of the universe during the Big Bang.

3. Can we observe singularities?

No, singularities cannot be directly observed because they are hidden within black holes. However, scientists can study the effects of singularities on their surroundings, such as the distortion of space-time and the emission of radiation from the event horizon of a black hole.

4. Are there different types of singularities?

Yes, there are two main types of singularities: the Big Bang singularity and the black hole singularity. The Big Bang singularity marks the beginning of the universe, while the black hole singularity is found at the center of a black hole.

5. What is the singularity at the center of a black hole?

The singularity at the center of a black hole is a point of infinite density and zero volume. It is where the laws of physics, as we know them, no longer apply. This singularity is surrounded by the event horizon, which marks the point of no return for anything entering the black hole.

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