A couple of questions about singularities

  • Context: Graduate 
  • Thread starter Thread starter twistor
  • Start date Start date
  • Tags Tags
    Couple Singularities
Click For Summary

Discussion Overview

The discussion revolves around the nature of singularities in cosmology and gravity, exploring their definitions, mathematical relationships, existence, and implications in the context of the Big Bang and quantum mechanics. Participants raise questions about the differences between cosmological and gravitational singularities, the mathematical tools that might relate them, and the conditions under which they exist.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants differentiate between cosmological singularities, which occur at a time when mathematics fails to describe dynamics, and gravitational singularities, which are point-like with infinite density.
  • There is a suggestion that various mathematical methods exist to describe singularities, including the Schwarzschild metric for black holes and thermodynamic equations for cosmological singularities.
  • Some participants assert that black holes exist, while the existence of cosmological singularities is debated.
  • One participant challenges the common perception of the Big Bang as an explosion, proposing it as a hot dense beginning that occurred throughout the universe rather than at a single point.
  • There is a discussion about the relationship between quantum mechanics and singularities, with references to Planck units and the avoidance of infinity issues.
  • Some participants claim that primordial black holes formed in the early universe, though the timing and conditions are uncertain.
  • A later reply emphasizes that minimum time or units mentioned are educated guesses, noting that true infinities in physical observables are generally avoided in physics.
  • Another participant introduces a complex argument involving quantum mechanics, Planck's constant, and the nature of the universe at the time of the Big Bang, suggesting that a singularity may not be the correct interpretation of early conditions.

Areas of Agreement / Disagreement

Participants express differing views on the definitions and implications of singularities, with no consensus reached on their existence or the nature of the Big Bang. The discussion remains unresolved regarding the relationship between quantum mechanics and singularities.

Contextual Notes

Participants note limitations in current understanding, particularly regarding the breakdown of physics near singularities and the speculative nature of certain claims about minimum units and the early universe.

twistor
Messages
74
Reaction score
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?
 
Space news on Phys.org
I count seven questions, not two (a "couple"). :wink:
 
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
 
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!
 
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.
 
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.
 
Last edited:
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.
 

Similar threads

Undergrad Question about the big bang singularity
  • · Replies 13 ·
Replies
13
Views
5K
Undergrad Question on the horizon problem
  • · Replies 17 ·
Replies
17
Views
3K
Undergrad How does the Singularity produce all the diverse matter in the universe?
  • · Replies 9 ·
Replies
9
Views
2K
Undergrad Shouldn't the Big bang be physically impossible?
  • · Replies 25 ·
Replies
25
Views
4K
Graduate What are Black Hole Singularities: Physical or Mathematical?
  • · Replies 2 ·
Replies
2
Views
2K
Undergrad Some questions about Cosmic Inflation
  • · Replies 4 ·
Replies
4
Views
5K
Undergrad Does Kerr's argument against singularities apply to all black holes?
  • · Replies 12 ·
Replies
12
Views
3K
Graduate What is the limit of classical GR in describing the singularity of a black hole?
  • · Replies 9 ·
Replies
9
Views
3K
Undergrad Relativistic Reference Frames and the Big Bang?
  • · Replies 6 ·
Replies
6
Views
2K
Graduate Assumptions of Hawking-Penrose 1970 Singularity Theorem
  • · Replies 35 ·
2
Replies
35
Views
4K