Are Space & Time A Fundamental Property Or Emergent

[Intoscience]

There is  popular theoretical "belief" among some leading physicists that space & time may not be fundamental property's of the universe & the governing laws of nature.

Theoretical physicists like  Nima Arkani-Hamed & Sean Carrol seriously consider that space and maybe time are rather emergent properties, coming from something more fundamental. This line of thought is driven by gravity and quantum mechanics at the most extreme small limits (Planck scales). 

It's a very interesting idea and if it gains any ground may open up physics to the possibility of better theories and a more fundamental understanding of how the universe works.  

What is your take on this idea?

 

[beecee]

33 minutes ago, Intoscience said:

There is  popular theoretical "belief" among some leading physicists that space & time may not be fundamental property's of the universe & the governing laws of nature.

Theoretical physicists like  Nima Arkani-Hamed & Sean Carrol seriously consider that space and maybe time are rather emergent properties, coming from something more fundamental. This line of thought is driven by gravity and quantum mechanics at the most extreme small limits (Planck scales). 

It's a very interesting idea and if it gains any ground may open up physics to the possibility of better theories and a more fundamental understanding of how the universe works.  

What is your take on this idea?

 

Space is defined by three dimensions...Time adds the fourth dimension which we see as spacetime. Space and time are also interchangable, and all while being abstract concepts, are still real. Whether they are fundamental maybe revealed by a future validated QGT. 

You may have seen this interview with Professor Carroll.....

 

[Intoscience]

Hi Beecee, thanks for your reply. 

Yes, I've seen this interview and listened to and watched many more on this subject from other physicists. 

I don't argue that time is not real. 

I'm more interested in the defining fundamental idea of what space-time is. Why do they consider that spacetime is not fundamental? It appears that the argument stems from the reductionist perspective?  

[swansont]

1 hour ago, Intoscience said:

It's a very interesting idea and if it gains any ground may open up physics to the possibility of better theories and a more fundamental understanding of how the universe works.

It's interesting (to some, anyway) and yes, it might open the door to new physics. Likely at scales we can't yet probe, or are at the edge of probong, because otherwise we would probably have noticed something by now.  

[Intoscience]

8 minutes ago, swansont said:

It's interesting (to some, anyway) and yes, it might open the door to new physics. Likely at scales we can't yet probe, or are at the edge of probong, because otherwise we would probably have noticed something by now.  

This seems to be the major problem, the very fact that we cannot observe such extremely small distances. Much like we cannot observe what is inside a black hole, where at the centre such an extremely small region may exist. 

[studiot]

 

On 7/7/2021 at 10:13 AM, Intoscience said:

What is your take on this idea?

Can you tell me what you understand 'emergent' to mean ?

Perhaps with some example(s) of actual 'emergence'.

[Intoscience]

3 hours ago, studiot said:

 

Can you tell me what you understand 'emergent' to mean ?

Perhaps with some example(s) of actual 'emergence'.

Well, I guess in the context of this topic, then space and maybe time are emergent (come into existence) under certain quantum conditions, that originate from something even more fundamental. These are not my ideas, I'm trying to gain an understanding of how these physicists are suggest this. My understanding is that its based on reduction at the quantum level, and what might lay beyond our current observation capabilities.  

I guess we could argue similar, where in GR gravity is an emergent condition that arises due to space-time curvature?

[swansont]

9 minutes ago, Intoscience said:

Well, I guess in the context of this topic, then space and maybe time are emergent (come into existence) under certain quantum conditions, that originate from something even more fundamental. These are not my ideas, I'm trying to gain an understanding of how these physicists are suggest this. My understanding is that its based on reduction at the quantum level, and what might lay beyond our current observation capabilities.  

I guess we could argue similar, where in GR gravity is an emergent condition that arises due to space-time curvature?

From what I've read, "emergent" indicates a behavior that is seen at some larger scale but is not seen at a smaller scale with the constituent entities. Gravity would not qualify. As far as we know, even a small mass exerts gravity, even if we ignore it.

 

[Intoscience]

1 minute ago, swansont said:

From what I've read, "emergent" indicates a behavior that is seen at some larger scale but is not seen at a smaller scale with the constituent entities. Gravity would not qualify. As far as we know, even a small mass exerts gravity, even if we ignore it.

 

But if there is no space-time curvature then there is no gravity. In GR gravity is a condition/behaviour/state  (dependent on your definition) that arises from the curvature of space-time. So in my mind gravity is emergent from space-time curvature. Space-time curvature occurs when either energy or mass is present and the amount of curvature is dependent on the density/concentration of the mass or energy relative to the space it occupies. 

I'm not arguing, I'm asking if my basic understanding of gravity in the model of GR is correct?

[swansont]

18 minutes ago, Intoscience said:

But if there is no space-time curvature then there is no gravity.

They are the same thing. It's not emergent, as such.

 

[studiot]

12 minutes ago, Intoscience said:

But if there is no space-time curvature then there is no gravity. In GR gravity is a condition/behaviour/state  (dependent on your definition) that arises from the curvature of space-time. So in my mind gravity is emergent from space-time curvature. Space-time curvature occurs when either energy or mass is present and the amount of curvature is dependent on the density/concentration of the mass or energy relative to the space it occupies. 

I'm not arguing, I'm asking if my basic understanding of gravity in the model of GR is correct?

Arguing , discussing whatever. You are putting your points in the proper way.

🙂

It is not, however, my understanding of the meaning of the term, 'emergent'.

We do not consider heat, resulting from friction to be 'emergent', although it is the result of that friction.

There has to be something special about the circumstances that allows or brings about 'emergence', so that it would not happen in different circumstances.

Consider a pile of bricks for instance.

If you stack them in any old random way, the pile will soon fall over.

But if you configure them in one particular way you will achieve a very strong and stable self supporting structure called an arch.

This property sensitive to configuration which is the controlling circumstance in this case.

Configuration is not more, or less 'fundamental' than the bricks themselves or their other properties.

[beecee]

9 hours ago, swansont said:

From what I've read, "emergent" indicates a behavior that is seen at some larger scale but is not seen at a smaller scale with the constituent entities. Gravity would not qualify. As far as we know, even a small mass exerts gravity, even if we ignore it.

That is the way I would interpret it also. Would an example be Space and time possibly at or before the quantum/Planck level and where our laws of physics and GR do not apply?

[swansont]

13 minutes ago, beecee said:

That is the way I would interpret it also. Would an example be Space and time possibly at or before the quantum/Planck level and where our laws of physics and GR do not apply?

That’s what’s being looked at, AFAIK

[StringJunky]

9 hours ago, swansont said:

From what I've read, "emergent" indicates a behavior that is seen at some larger scale but is not seen at a smaller scale with the constituent entities. Gravity would not qualify. As far as we know, even a small mass exerts gravity, even if we ignore it.

 

I have seen it mentioned that another requirement is a failure to predict  the correct outcome in emergent circumstances.  You can't predict what will result from some combination. It seems to me that this requirement is that it 'appears' to be magic. From this, it would seem  that the use of the word 'emergence' might just be a placeholder word for some process that is not yet understood.

[Intoscience]

16 hours ago, studiot said:

Arguing , discussing whatever. You are putting your points in the proper way.

🙂

It is not, however, my understanding of the meaning of the term, 'emergent'.

We do not consider heat, resulting from friction to be 'emergent', although it is the result of that friction.

There has to be something special about the circumstances that allows or brings about 'emergence', so that it would not happen in different circumstances.

Consider a pile of bricks for instance.

If you stack them in any old random way, the pile will soon fall over.

But if you configure them in one particular way you will achieve a very strong and stable self supporting structure called an arch.

This property sensitive to configuration which is the controlling circumstance in this case.

Configuration is not more, or less 'fundamental' than the bricks themselves or their other properties.

Right, ok that helps.

Thanks 

[studiot]

I thought I had added in the example using space and time.

In quantum mechanics by themselves, neither space nor time are emergent as they are a necessary part of the fundamental principles and equations.

However the Heisenberg Uncertainty Principle is emergent from this Mathematics as the matrices involved ar non commutative.

ie

A.B is not equal to B.A where A and B are the relevant matrices, involving space / time.

So (B.A. - A.B) is non zero and gives us the Uncertainty Principle

[swansont]

That's a fundamental property of wave functions. I wouldn't say it's emergent. You might argue that this is fundamental, and having well-defined trajectories is an emergent property, since you tend to need a large mass (and thus a large number of particles conglomerated) for the wave nature to cease dominating.

 

edit:

https://en.wikipedia.org/wiki/Emergence#Nonliving,_physical_systems

The laws of classical mechanics can be said to emerge as a limiting case from the rules of quantum mechanics applied to large enough masses. This is particularly strange since quantum mechanics is generally thought of as more complicated than classical mechanics.

The later examples of phase transitions might be a clearer one. It's not a property of a single particle. It's a collective behavior where you need a number of particles in order to observe it.

[studiot]

7 minutes ago, swansont said:

That's a fundamental property of wave functions. I wouldn't say it's emergent. You might argue that this is fundamental, and having well-defined trajectories is an emergent property, since you tend to need a large mass (and thus a large number of particles conglomerated) for the wave nature to cease dominating.

 

edit:

https://en.wikipedia.org/wiki/Emergence#Nonliving,_physical_systems

The laws of classical mechanics can be said to emerge as a limiting case from the rules of quantum mechanics applied to large enough masses. This is particularly strange since quantum mechanics is generally thought of as more complicated than classical mechanics.

The later examples of phase transitions might be a clearer one. It's not a property of a single particle. It's a collective behavior where you need a number of particles in order to observe it.

I am not convinced.

It must depend upon your use of the word emerge or emergent or emergence.

For instance I would say that the general English expression

The Moon emerged from behind the clouds is too wide and open (and just plain wrong) for the Scientific use.

But lots of (scientific) folks use it in different ways.

 

As far as matrix multiplication goes we know the commutator is sometimes zero sometimes not zero thus there are circumstances when there is an emergent consequence and sometimes not, depending upon circumstances

To me it is the reliable emergence of whatever phenomenon under the some repeated circumstances but equally relaible failure to emerge under different repeated circumstances.

I look forward to your definition to match future use against.

[swansont]

I'm following the description in the link I provided

emergence occurs when an entity is observed to have properties its parts do not have on their own, properties or behaviors which emerge only when the parts interact in a wider whole.

[studiot]

8 minutes ago, swansont said:

I'm following the description in the link I provided

emergence occurs when an entity is observed to have properties its parts do not have on their own, properties or behaviors which emerge only when the parts interact in a wider whole.

Thank you.

And are you happy (satisfied) with that self referential definition ?

[swansont]

1 hour ago, studiot said:

And are you happy (satisfied) with that self referential definition ?

I'm not unhappy with it; this isn't an area where I spend much time and effort. It's more for folks doing work on foundations of physics. I don't have anything invested in e.g. whether time is emergent or not, since that isn't going to affect how to build and operate clocks in any foreseeable future.

[Conjurer]

Sean Carrol explains it in his book, "The Particle at the End of the Universe".  That is a reference if you could not tell.  I could post the date and location it was published in reference form if you would like.

So, anyways, the reason why he believes spacetime is not fundamental is because it is a scaler.  The reason it is a scaler is because it has a base energy level that is not zero.  The reason its base energy is not zero is from random particle pairs that emerge and annihilator each other in space.  No one even believes anything about the actual properties of random particle pairs here, because they break conservation laws.  In other words, no one has discovered what causes them or where they come from, so they cannot derive what energy source is driving them or causing them to exist.  Therefore, the reason he believes spacetime is not fundamental is because he doesn't believe the energy comes from nowhere and it is free energy that violates conservation laws.  There has to be something else behind creating them in spacetime, and it is linked to a more fundamental property of spacetime.

I believe the universe came from pure nothingness and he should just get over it along with everyone else.  Energy would eventually have to come from somewhere for us to exist to even troll each other about it.   

[MigL]

Scalar just means that the value associated with every point in space-time has no direction.
I fail to see how that favors emergence, or fundamentality, of space-time.

[joigus]

Trying to answer to @Intoscience's question 'what's your take on this?', and leaving aside the ongoing discussion based on the nonsense of spacetime being a scalar... 

I understand 'emergent' as a variable that's derived from relationships among more fundamental variables, and it's not present in those variables. Very much what Swansont stated. It is derived from the overall dynamics of those variables.

The variable that's really bothersome, especially when trying to combine cosmology and quantum mechanics is time, not space. Because:

• The universe cannot be instantiated/re-instantiated
• There were no observers* [?]
• No really good explanation for initial conditions of the universe
• Meta-laws (laws previous to physical laws as we know them): What does 'previous' even mean?

Time, in combination with QM, really seems to stand in the way of anything meaningful we might try to say in very early cosmology. It's not a practical matter for everyday physics. It's about very early cosmology.

That's precisely why most prominent physicists who are concerned with cosmology support the view that spacetime, or maybe just time, is emergent. Namely: it hides something in it, so to speak; it derives from a more fundamental, structure.

The three questions, time asymmetry, chiral asymmetry, and charge asymmetry in the universe must be related, as the CPT theorem of quantum field theory relates them all very clearly. If/when we find out why time is a one-way pathway, because we get to understand how it emerged that way, we will probably understand the other two.

Maybe it's something completely unsuspected. Maybe instability and spontaneous breaking of symmetry are at the core of why we perceive the universe as a history, the actual underlying level being something much more symmetric, and observers only making sense as stretched over time. I'm approaching my dangerous 'push the envelope' mode.

* The now popular view of measurement as decoherence between alternatives doesn't even start to tackle this problem IMO, as irrespective of whether the universe is in a mixed instead of a pure quantum state, a quantum state for the whole universe doesn't make a lot of sense, at least with the usual operational rules that go with it. This is the problem of the pointer states, can be formally swept under the carpet for anything other than the whole universe, but is clearly posed in Wheeler & Zurek.

[studiot]

28 minutes ago, joigus said:

Trying to answer to @Intoscience's question 'what's your take on this?', and leaving aside the ongoing discussion based on the nonsense of spacetime being a scalar... 

I understand 'emergent' as a variable that's derived from relationships among more fundamental variables, and it's not present in those variables. Very much what Swansont stated. It is derived from the overall dynamics of those variables.

The variable that's really bothersome, especially when trying to combine cosmology and quantum mechanics is time, not space. Because:

• The universe cannot be instantiated/re-instantiated
• There were no observers* [?]
• No really good explanation for initial conditions of the universe
• Meta-laws (laws previous to physical laws as we know them): What does 'previous' even mean?

Time, in combination with QM, really seems to stand in the way of anything meaningful we might try to say in very early cosmology. It's not a practical matter for everyday physics. It's about very early cosmology.

That's precisely why most prominent physicists who are concerned with cosmology support the view that spacetime, or maybe just time, is emergent. Namely: it hides something in it, so to speak; it derives from a more fundamental, structure.

The three questions, time asymmetry, chiral asymmetry, and charge asymmetry in the universe must be related, as the CPT theorem of quantum field theory relates them all very clearly. If/when we find out why time is a one-way pathway, because we get to understand how it emerged that way, we will probably understand the other two.

Maybe it's something completely unsuspected. Maybe instability and spontaneous breaking of symmetry are at the core of why we perceive the universe as a history, the actual underlying level being something much more symmetric, and observers only making sense as stretched over time. I'm approaching my dangerous 'push the envelope' mode.

* The now popular view of measurement as decoherence between alternatives doesn't even start to tackle this problem IMO, as irrespective of whether the universe is in a mixed instead of a pure quantum state, a quantum state for the whole universe doesn't make a lot of sense, at least with the usual operational rules that go with it. This is the problem of the pointer states, can be formally swept under the carpet for anything other than the whole universe, but is clearly posed in Wheeler & Zurek.

 

Thank you for an interesting view, especially the first line. +1