Is Spacetime Truly Smooth or Discrete?

[George Jones]

As for renormalization being carried over in a mathematically rigorous way by handling products of distributions, have a look at "Finite QED" by Scharf.)

I'm not sure, but I don't think that all experts who think about these things are comfortable with Scharf's work. Also, even after regularization and renormalization, QED is still (almost certainly) divergent, that is, individual terms in a particular series are all finite, but the series itself diverges. Physicists think this is okay because:

1) divergent series often converge faster than convergent series ;

2) this just indicates the presence of other physics not taken into account by QED.

 

[DrFaustus]

George -> Don't really want to go into this... just a quick reply. It's no need for physicists to be comfortable with the rigorous approach to QFT as essentially all the physics that was and is currently extracted from QFT is done so within the standard Lagrangian QFT framework. Scharf's book is a book mathematical physicists are more comfortable with simply because it's rigorous. And I can reassure you that ALL the mathematical physicists are familiar with that book. But as I said, it's not worth the effort for the vast majority of physics research.

Physicists may be happy about the non-convergence of the perturbative series, but mathematical physicists most definitely are not. And in fact, the rigorous construction of an interacting QFT model in 4D does not exist as of now. A lot of effort has been put into this an in 2D and 3D rigorous models have been constructed. But not in 4D. And Witten knows this all too well and it's the reason why he, amongst others, insisted in putting the Yang-Mills problem amongst the Millenium prizes. In other words, construct a QFT model in 4D and win a million (more or less).

As for the "other physics beyond QED" claim, that's really just a heuristic interpretation of the entire situation. The reason is that supersymmetric non-commutative Yang-Mills models offer some hope in such a rigorous construction, and yet there is physics beyond such models. Stated differently, the problem of the rigorous construction of an interacting QFT model is (almost) a purely mathematical problem. And it's resolution will tell us very little, if anything, about physics beyond any particular model.

 

[john 8]

Pythagorean asked; Is Spacetime Smooth? Smooth: infinitely differentiable.

You said;

as far as we/I know, yes, it is smooth

How do you know it is smooth? If this spacetime thing is smooth that means it is a physical object with a surface. Most smooth objects reflect light. And all objects have a location in space.

So please give more data on this statement that you made.

 

[john 8]

Just wanting to add another witness to the fact that every mainstream book on quantum mechanics and quantum field theory treats space / spacetime as a smooth manifold.

Well said, all the currently established mainstream theories (the standard model) and the mainstream extensions to these (GUTs, string theory) always treat spacetime as a smooth manifold.

Naty1, Malawi and I have both gone through a mainstream graduate education in physics, and we are telling you that spacetime is smooth in the standard model and in string theory. You are disagreeing with us on the basis of vague statements in wikipedia and popularized books, when we each have shelves full of textbooks that leave no doubt that spacetime is smooth in all of our current physical theories. In my opinion, we need to get some knowledgeable moderators into this dicussion so that we can resolve this disagreement for good.

If you don't mind, could you please clarify something for me and the others on this form.

When you say spacetime is smooth, are you referring to a mathematical model or a physical structure?

 

[Naty1]

For those who may be interested a related thread is "Are we digital or analog?"
at https://www.physicsforums.com/showthread.php?p=2269227#post2269227

 

[ibcnunabit]

Is Spacetime Smooth?

Smooth: infinitely differentiable

I don't think anyone really knows, at this point. It hasn't been proved either way, but we do know that if it's quantized it must be a pretty fine-grained quantization. Reiner Hedrich, for one, has written a number of papers on the idea of quantum spacetime.

If quantum mechanics is universally true, then it's quantized. If quantum gravity turns out true, then spacetime must be quantized, so gravitons would mean quantum spacetime. As would chronons, if you believe in quantum time, but that's pretty speculative at this point.

Right now most (non-QM) models start with an assumption of smoothness, but hey--a HD TV looks pretty smooth from a distance, but we all know there are pixels when you look closely enough. I'd like to see it proved one way or the other; I'm very curious to find out which way it comes out.

--Mike from Shreveport

 

[ibcnunabit]

Is Spacetime Smooth?

Smooth: infinitely differentiable

I don't think anyone really knows, at this point. It hasn't been proved either way, but we do know that if it's quantized it must be a pretty fine-grained quantization. Reiner Hedrich, for one, has written a number of papers on the idea of quantum spacetime.

If quantum mechanics is universally true, then it's quantized. If quantum gravity turns out true, then spacetime must be quantized, so gravitons would mean quantum spacetime. As would chronons, if you believe in quantum time, but that's pretty speculative at this point.

Right now most (non-QM) models start with an assumption of smoothness, but hey--a HD TV looks pretty smooth from a distance, but we all know there are pixels when you look closely enough. I'd like to see it proved one way or the other; I'm very curious to find out which way it comes out.

--Mike from Shreveport

 

[john 8]

I don't think anyone really knows, at this point. It hasn't been proved either way, but we do know that if it's quantized it must be a pretty fine-grained quantization. Reiner Hedrich, for one, has written a number of papers on the idea of quantum spacetime.

If quantum mechanics is universally true, then it's quantized. If quantum gravity turns out true, then spacetime must be quantized, so gravitons would mean quantum spacetime. As would chronons, if you believe in quantum time, but that's pretty speculative at this point.

Right now most (non-QM) models start with an assumption of smoothness, but hey--a HD TV looks pretty smooth from a distance, but we all know there are pixels when you look closely enough. I'd like to see it proved one way or the other; I'm very curious to find out which way it comes out.

--Mike from Shreveport

Look, this space-time thing is not a real physical entity. If it was then think about where does it exists? What exists around it? What is it made of? If you say it is made of particles then what do you call that area between these space-time particles? And particles of what?

If you say that space-time is a E/M wave then where is this wave eminating from?

Please stop believing in fantasy and use science to solve your questions regarding science, physics, astronomy, etc.

There is no scientific reference or definition that states that space-time is a thing that exists as an entity. Please stop this science fiction fantasy. The field of science does not define space-time as a physical thing.

 

[WaveJumper]

There is no scientific reference or definition that states that space-time is a thing that exists as an entity. Please stop this science fiction fantasy. The field of science does not define space-time as a physical thing.

As far as physics and science are concerned, there is no such thing as physical matter or as you say "Physical thing"(the daily usage of the word "physical stuff"). There is only quantum fields that exchange force carrier bosons to create the illusion of solid physical stuff.

"Physical things" cannot be touched. You have never really touched anything at all, as the electrons in the outer shells repel the electrons of matter at 10^-8m.

Having said that, I think spacetime appears as much a thing as solid matter. And they are both relative to the frame of reference of the observer.

 

[john 8]

As far as physics and science are concerned, there is no such thing as physical matter or as you say "Physical thing"(the daily usage of the word "physical stuff"). There is only quantum fields that exchange force carrier bosons to create the illusion of solid physical stuff.

"Physical things" cannot be touched. You have never really touched anything at all, as the electrons in the outer shells repel the electrons of matter at 10^-8m.

Having said that, I think spacetime appears as much a thing as solid matter. And they are both relative to the frame of reference of the observer.

You have put this space-time thing in the same category as solid matter. You say that as far physics and science are concerned, there is no such thing as physical matter.

Sounds like you are confused.

Please refer to science reference books and look up matter.

There are many things around us that we agree exist because we can percieve their presence. We notice things around us because they are made of something that our bodies can percieve.

However you want to look at the world around you, you have to agree that there are things that are detectable by us.

This universe is filled with things that are either made of atoms, electrons and such, and those things that are E/M waves. Either way, if we consider something to be a thing then that thing is a form of energy. There is no doubt about the many things that we call real or physical in that they are a form of energy that occupy a location in space.


So, please be clear in what you are saying about this space-time thing. Is it a particle, a wave such as quantum fields that exchange force carrier bosons to create the illusion of solid physical stuff.

You contradicted yourself in your explanation of physical stuff, and what space-time is.

Please clear up your explanation.

 

[john 8]

Having said that, I think spacetime appears as much a thing as solid matter. And they are both relative to the frame of reference of the observer.

I forgot to add this.

You say space-time is relative to the frame of reference of the observer. What does it mean to observe? To look? To see? Are you saying that this space-time thing can be observed?

I know solid matter can reflect light and thus be observed by the eye. Are you saying that this space-time thing has a structure simular to solid matter?

You are all over the map on this. Is space-time real, not real, simular to solid matter, what exactly are you saying?

 

[WaveJumper]

You have put this space-time thing in the same category as solid matter. You say that as far physics and science are concerned, there is no such thing as physical matter.

Sounds like you are confused.

Please refer to science reference books and look up matter.

No, it's you who is confused and i am going to add more to your confusion. I said solid physical matter is an illusion, and look above - you said "You have put this space-time thing in the same category as solid matter". Yes, i did put it in the same category as matter, and there is no solid matter as such outside of our perception. So is spacetime. Outside of our perception - spacetime is quite different, in GR spacetime is relative, in QM the objective existence of space is debateable. And unless you can present evidence that you are smarter than Einstein, i suggest that you learn to live with the following statement:



"Time and space and gravitation have no separate existence from matter."

AE

There are many things around us that we agree exist because we can percieve their presence. We notice things around us because they are made of something that our bodies can percieve.

However you want to look at the world around you, you have to agree that there are things that are detectable by us.

This universe is filled with things that are either made of atoms, electrons and such, and those things that are E/M waves. Either way, if we consider something to be a thing then that thing is a form of energy. There is no doubt about the many things that we call real or physical in that they are a form of energy that occupy a location in space.


So, please be clear in what you are saying about this space-time thing. Is it a particle, a wave such as quantum fields that exchange force carrier bosons to create the illusion of solid physical stuff.

You contradicted yourself in your explanation of physical stuff, and what space-time is.

Please clear up your explanation.

If i could perfectly explain what space-time really is, don't you think i would be the most famous person in the world? How would you want me to find this perfect description of the "spacetime thing"? By way of a time machine and traveling to the future or by contacting God? Don't be silly, please.

 

[WaveJumper]

I forgot to add this.

You say space-time is relative to the frame of reference of the observer. What does it mean to observe? To look? To see? Are you saying that this space-time thing can be observed?

I know solid matter can reflect light and thus be observed by the eye. Are you saying that this space-time thing has a structure simular to solid matter?

You are all over the map on this. Is space-time real, not real, simular to solid matter, what exactly are you saying?

Physics has not thoroughly and meaningfully described reality the way we perceive it. You have zero knowledge in physics and hence your misconception that physics is at present day a great tool to understand what existence and reality is. It is not.

Put up with the situation or find yourself a damn religion(if you MUST believe in something).

 

[Istvan Mezo]

The collapse of the wave function is caused by an interaction with the rest of the Universe. This is not a linear process.

On the other hand, in Quantum Field Theory the interactions between fields and particles are introduced in the Lagrange function as muiltiplication of operators. Maybe this multiplication causes the nonlinearity.

Do I understand well?

 

[john 8]

No, it's you who is confused and i am going to add more to your confusion. I said solid physical matter is an illusion, and look above - you said "You have put this space-time thing in the same category as solid matter". Yes, i did put it in the same category as matter, and there is no solid matter as such outside of our perception. So is space-time. Outside of our perception - space-time is quite different, in GR space-time is relative, in QM the objective existence of space is debatable. And unless you can present evidence that you are smarter than Einstein, i suggest that you learn to live with the following statement:.

Here is a definition of illusion from a dictionary:

1. something that deceives by producing a false or misleading impression of reality.
2. the state or condition of being deceived; misapprehension.
3. an instance of being deceived.
4. Psychology. a perception, as of visual stimuli (optical illusion), that represents what is perceived in a way different from the way it is in reality.
5. a very thin, delicate tulle of silk or nylon having a cobwebbed appearance, for trimmings, veilings, and the like.
6. Obsolete. the act of deceiving; deception; delusion.


Are any of these the definitions that you want to use to describe walls, rocks, cars, and all of the other things that are perceivable through our senses? Science does not define solid physical matter as an illusion. Illusions and solid physical matter are two different things. You want to say that solid physical matter is an illusion, yet for anything to exist that is perceivable by our senses that thing is made of something.

Illusion or not, science has defined solid physical matter as being made of atoms. Is your space-time made of atoms? If not, what is this space-time thing made of and why is there no scientific reference that backs up your claim regarding matter.

Also, if there is no solid matter what is that thing that is working against gravity and your weight that you are sitting on? What are those things called walls that you can not walk through as you can with air?

A table can support an object. A table is agreed by all living things to exist. A table and other matter can reflect light.

I say space-time is not a thing that belongs in the group of things that we as a human race put those things that we can perceive through our senses. If you disagree, how do you perceive this space-time thing that tells you that it is a thing that exists?

Here is how your thinking is coming across: Einstein said it, I believe it, that is it.

What physical evidence or observation do you have that backs up your claim that space-time is able to be perceived?

"Time and space and gravitation have no separate existence from matter."[/i]
:.

What does this mean? Are you saying they are the same thing? Are you saying that they are all made of the same thing? Where are you getting this data? Be specific please.

If i could perfectly explain what space-time really is, don't you think i would be the most famous person in the world? How would you want me to find this perfect description of the "spacetime thing"? By way of a time machine and traveling to the future or by contacting God? Don't be silly, please.

Just give the scientific explanation, simple as that. If something exists you do not need a time machine or God to perceive it.

Look, does this space-time thing have a size, weight, color, thickness. Can it be sensed, measured or perceived, if so in what way. You believe that this fabric of space-time is a thing, so just say why.

 

[john 8]

If i could perfectly explain what space-time really is, don't you think i would be the most famous person in the world? How would you want me to find this perfect description of the "spacetime thing"? By way of a time machine and traveling to the future or by contacting God? Don't be silly, please.

Just give the scientific explanation, simple as that. If something exists you do not need a time machine or God to perceive it.

Look, does this space-time thing have a size, weight, color, thickness. Can it be sensed, measured or perceived, if so in what way. You believe that this fabric of space-time is a thing, so just say why.

Physics has not thoroughly and meaningfully described reality the way we perceive it. You have zero knowledge in physics and hence your misconception that physics is at present day a great tool to understand what existence and reality is. It is not.

Put up with the situation or find yourself a damn religion(if you MUST believe in something).

Physics is a field of endeavor that is comprised of human beings. They are part of the human race just like you and I are. We are all in the same group when it comes to reality. When you say that physics has not thoroughly and meaningfully described reality the way WE perceive it you are wrong.

Those in physics are WE and those in physics have human perceptions and nervous systems the same as you and me, their reality is a human reality. You are really grasping at straws here, just explain why YOU think that WE should agree with you that space-time is a thing that is perceivable and has some effect on the rest of the physical universe.

Einstein, Newton Galileo, Copernicus, just to name a few, those people put forward data that has shaped our present day understanding of the world around us. Does the whole world have a misconception of the laws and theories put forward by these men?

You make it sound as though all the discoveries and observations that have been done by mankind in the field of physics are NOT what reality is. So that means that you have some other idea or concept of what reality IS.

You say physics is not a good tool in understanding what existence and reality is, so please tell the world what is the correct tool, or what reality really is. WE are all mistaken as to what reality is according to what you are saying.

Lets keep this simple. You say that space-time is some sort of thing that exists, I say that space-time is not a thing, is not made of anything, and is just a mathematical model.

Just give some evidence of the existence of this space-time thing?

 

[friend]

Look, does this space-time thing have a size, weight, color, thickness. Can it be sensed, measured or perceived, if so in what way. You believe that this fabric of space-time is a thing, so just say why.

This is how we know that spacetime is a physical entity... We observe that things traveling close to the speed of light shrink in the direction of motion but observers riding along those traveling things do not preceive any shrinkage. How can this be if there is no spacetime through which to define travelling?

 

[WaveJumper]

Just give the scientific explanation, simple as that. If something exists you do not need a time machine or God to perceive it.

There is no theory of everything yet, we DO NOT know how the universe works as a whole and what it really is apart from our sensory experience of it. You need to remember that.

Look, does this space-time thing have a size, weight, color, thickness. Can it be sensed, measured or perceived, if so in what way. You believe that this fabric of space-time is a thing, so just say why.

Do you really want me to repeat 100 times that perception of reality and the true nature of reality aren't quite the same? Length, mass, speed and time are relative concepts.

Physics is a field of endeavor that is comprised of human beings. They are part of the human race just like you and I are. We are all in the same group when it comes to reality. When you say that physics has not thoroughly and meaningfully described reality the way WE perceive it you are wrong.

Are you aware that for more than a century there hasn't been just classical mechanics but also quantum theory and General relativity in physics? Your quote above is complete nonsense when applied to 20th and 21th century physics and last i checked we were living in the 21th.

Those in physics are WE and those in physics have human perceptions and nervous systems the same as you and me, their reality is a human reality. You are really grasping at straws here, just explain why YOU think that WE should agree with you that space-time is a thing that is perceivable and has some effect on the rest of the physical universe.

I've said it multiple times already - because of length contraction and time dilation at high speeds, what you perceive as "thing"(the whole universe; spacetime) isn't absolute. It isn't really the "thing" that your perception feeds you.

Einstein, Newton Galileo, Copernicus, just to name a few, those people put forward data that has shaped our present day understanding of the world around us. Does the whole world have a misconception of the laws and theories put forward by these men?

You need to take off your aluminium shades as they blocking your view. The world of Einstein is not the world of Newton. Ignorance convinces, doesn't it? We know much but understand little and you are clearly out of your depth on this topic.

You make it sound as though all the discoveries and observations that have been done by mankind in the field of physics are NOT what reality is. So that means that you have some other idea or concept of what reality IS.

Nobody knows the true nature of reality, you need to stop this crap. Most of us come here to exchange ideas and 'restore' reality to something that makes some sense. On physicsforums.com you'll find all types of physicists, they come in all flavours - ones who believe the Moon is not there when you're not looking(i.e. physical reality does not exist), others who believe the universe splits into 2 copies anytime my dog goes to pee, yet others believe you are living in a non-local universe in which you are just a biological 'robot' deprived of free will, others believe the universe is a hologram, etc. You'd often hear talk of Ultimate Reality, this is any of the above propositions/interpretations. Reality, whatever it is, is pretty strange for certain.

You say physics is not a good tool in understanding what existence and reality is, so please tell the world what is the correct tool, or what reality really is.

Am i supposed to answer this or just sit back and laugh? You think i am something close to the conception of an all knowing god? Thanks for the compliment, but sadly i am not. But thanks, anyway. A TOE is at least conjectured to be a valid tool to understand the true nature of reality. If you are eager to find what spacetime truly is, you need to buy a time machine(there is one on ebay now, look for "1/6th SCALE TIME MACHINE FROM THE 1960 GEORGE PAL MOVIE").

WE are all mistaken as to what reality is according to what you are saying.

I concede that somebody may be right. It's still anybody's guess what reality really is.

Lets keep this simple. You say that space-time is some sort of thing that exists, I say that space-time is not a thing, is not made of anything, and is just a mathematical model.

Just give some evidence of the existence of this space-time thing?

It may be as you are saying, a lot of high profile physicists are giving serious consideration to the idea that information is fundamental to reality, and energy/matter is a derivation. But as far as perception of reality is concerned, spacetime is as much a thing as matter is(and that's a consequence of experimentally verified GR). As an additional clue, the only candidate for a TOE - String Theory posits that everything, including space and time, is made up of tiny vibrating 1-dimensional strings. If there is a material world out there, space is as much part of it as matter is.


In general, I feel common people should have the right to, at least on a basic level, be introduced to the controversies of modern physics on the nature of reality. The mathematical fence is making otherwise intelligent people look like sheep.

 

[john 8]

This is how we know that spacetime is a physical entity... We observe that things traveling close to the speed of light shrink in the direction of motion but observers riding along those traveling things do not preceive any shrinkage. How can this be if there is no spacetime through which to define travelling?

What are the physical qualities of this physical entity? It is physcical in what way?

Is there any science that describes space-time as a physical entity?

 

[john 8]

There is no theory of everything yet, we DO NOT know how the universe works as a whole and what it really is apart from our sensory experience of it. You need to remember that.


Do you really want me to repeat 100 times that perception of reality and the true nature of reality aren't quite the same? Length, mass, speed and time are relative concepts.


Are you aware that for more than a century there hasn't been just classical mechanics but also quantum theory and General relativity in physics? Your quote above is complete nonsense when applied to 20th and 21th century physics and last i checked we were living in the 21th.

I've said it multiple times already - because of length contraction and time dilation at high speeds, what you perceive as "thing"(the whole universe; spacetime) isn't absolute. It isn't really the "thing" that your perception feeds you.

You need to take off your aluminium shades as they blocking your view. The world of Einstein is not the world of Newton. Ignorance convinces, doesn't it? We know much but understand little and you are clearly out of your depth on this topic.

Nobody knows the true nature of reality, you need to stop this crap. Most of us come here to exchange ideas and 'restore' reality to something that makes some sense. On physicsforums.com you'll find all types of physicists, they come in all flavours - ones who believe the Moon is not there when you're not looking(i.e. physical reality does not exist), others who believe the universe splits into 2 copies anytime my dog goes to pee, yet others believe you are living in a non-local universe in which you are just a biological 'robot' deprived of free will, others believe the universe is a hologram, etc. You'd often hear talk of Ultimate Reality, this is any of the above propositions/interpretations. Reality, whatever it is, is pretty strange for certain.

Am i supposed to answer this or just sit back and laugh? You think i am something close to the conception of an all knowing god? Thanks for the compliment, but sadly i am not. But thanks, anyway. A TOE is at least conjectured to be a valid tool to understand the true nature of reality. If you are eager to find what spacetime truly is, you need to buy a time machine(there is one on ebay now, look for "1/6th SCALE TIME MACHINE FROM THE 1960 GEORGE PAL MOVIE").

I concede that somebody may be right. It's still anybody's guess what reality really is.


It may be as you are saying, a lot of high profile physicists are giving serious consideration to the idea that information is fundamental to reality, and energy/matter is a derivation. But as far as perception of reality is concerned, spacetime is as much a thing as matter is(and that's a consequence of experimentally verified GR). As an additional clue, the only candidate for a TOE - String Theory posits that everything, including space and time, is made up of tiny vibrating 1-dimensional strings. If there is a material world out there, space is as much part of it as matter is.


In general, I feel common people should have the right to, at least on a basic level, be introduced to the controversies of modern physics on the nature of reality. The mathematical fence is making otherwise intelligent people look like sheep.

Lets get back on track here.

Here is a statement that I made that you quoted in post 59

“There is no scientific reference or definition that states that space-time is a thing that exists as an entity. Please stop this science fiction fantasy. The field of science does not define space-time as a physical thing.”


Here is your response:

As far as physics and science are concerned, there is no such thing as physical matter or as you say "Physical thing"(the daily usage of the word "physical stuff"). There is only quantum fields that exchange force carrier bosons to create the illusion of solid physical stuff.

"Physical things" cannot be touched. You have never really touched anything at all, as the electrons in the outer shells repel the electrons of matter at 10^-8m.

Having said that, I think spacetime appears as much a thing as solid matter. And they are both relative to the frame of reference of the observer.

I asked for a scientific definition or reference that states that space-time exists as a physical entity. You have not provided any. Period!

Does science define space-time as a physical entity? Y/N.

I am not asking for your opinions on reality or discussions on T.O.E. Stop avoiding the question.

Does science define space-time as a physical entity? Y/N. Just answer the question.

After we have established what science says regarding space-time then we can move forward from there.

I know that you put much effort into your latest post, but all of this is so simple. Does science define space-time as a physical entity? Y/N.

What you find will clear things up for you and get you on the right track. Science has established what space-time is. Getting the established definitions and the established understanding will help you in getting rid of false data and beliefs.


I highlighted a section in your post, do you honestly think that there is a working time machine being sold on Ebay? WOW! You really do believe in fantasy and science fiction.

 

[Dale]

It is physcical in what way?

Hi john 8,

Are you still using your definition that "physical" means "wave or particle"?

FYI WaveJumper, friend, et al. you may want to go back and see some of john's earlier posts, he seems to be avoiding the previous threads where he presented similar stuff. A lot of the trouble communicating with him is semantic, you have to define things clearly.

 

[WaveJumper]

Lets get back on track here.

Here is a statement that I made that you quoted in post 59

“There is no scientific reference or definition that states that space-time is a thing that exists as an entity. Please stop this science fiction fantasy. The field of science does not define space-time as a physical thing.”


Here is your response:





I asked for a scientific definition or reference that states that space-time exists as a physical entity. You have not provided any. Period!

Define "physical". Then define "Thing". Without these definitions, we are talking in different languages.

GR in the words of Wheeler:

“Spacetime tells matter how to move; matter tells spacetime how to curve.”

Spacetime can curve in the presence of immense gravity, why would it not be considered as much a thing as what you refer to as "Matter", which is nowhere being solid or absolute?

Does science define space-time as a physical entity? Y/N.

Science defines observations and experiments. Our current observations do not allow us to infer a coherent unified picture of the true nature of the classical(macro) and quantum scale.

I am not asking for your opinions on reality or discussions on T.O.E. Stop avoiding the question.

But reality(the state of existence of everything) is what you are inquiring about. A fundamental unified description of spacetime is actually Reality. You have only been asking about what reality is in this thread. No one knows, niemand weiss, никто не знает, comprendo?

Does science define space-time as a physical entity? Y/N. Just answer the question.

Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime(yet). Speculations and hypothesis about what fundamentally spacetime might be, are not a scientific definition of "spacetime". What you are looking for lies in the future.

After we have established what science says regarding space-time then we can move forward from there.

Space in qm is very diffrent from the picture of space in relativity and classical mechanics. For all intents and purposes, a good case can be made that spacelike separation does not exist, based on Bell's theorem.

The only hint we have from the purported canditate for unified theory points to spacetime not being fundamental:

"Is spacetime fundamental?
Note that there is a complication in the relationship between strings and spacetime. String theory does not predict that the Einstein equations are obeyed exactly. String theory adds an infinite series of corrections to the theory of gravity. Under normal circumstances, if we only look at distance scales much larger than a string, then these corrections are not measurable. But as the distance scale gets smaller, these corrections become larger until the Einstein equation no longer adequately describes the result.
In fact, when these correction terms become large, there is no spacetime geometry that is guaranteed to describe the result. The equations for determining the spacetime geometry become impossible to solve except under very strict symmetry conditions, such as unbroken supersymmetry, where the large correction terms can be made to vanish or cancel each other out.
This is a hint that perhaps spacetime geometry is not something fundamental in string theory, but something that emerges in the theory at large distance scales or weak coupling. This is an idea with enormous philosophical implications."

http://www.superstringtheory.com/blackh/blackh4.html

Science has established what space-time is.

Are you a time traveller holding a 3000 Mpix camera? Reference please of a unified picture of spacetime.


Suppose you were a time traveller coming from year 3112. Why would your frog view theory of the true nature of spacetime be considered complete? For all intents and purposes, this might be forever impossible.

 

[john 8]

Hi john 8,

Are you still using your definition that "physical" means "wave or particle"?

FYI WaveJumper, friend, et al. you may want to go back and see some of john's earlier posts, he seems to be avoiding the previous threads where he presented similar stuff. A lot of the trouble communicating with him is semantic, you have to define things clearly.

Alright. So what is the definition of physical according to you?

 

[john 8]

Define "physical". Then define "Thing". Without these definitions, we are talking in different languages..

I define "physical" and "thing" the same as any definition found in any standard dictionary.

Notice how no one has given a scientific definition of space-time that states space-time is a physical thing according to how science defines "physical" and "thing". STOP AVOIDING THE QUESTION AND JUST GIVE THE SCIENTIFIC EVIDENCE. Show the proof that space-time is a physical thing. Has anyone shown that space=time is a physical thing? NO. Stop giving your hopes and dreams and give scientific evidence. Space-time is physical in what way?

GR in the words of Wheeler:

“Spacetime tells matter how to move; matter tells spacetime how to curve.”

Spacetime can curve in the presence of immense gravity, why would it not be considered as much a thing as what you refer to as "Matter", which is nowhere being solid or absolute?..

Great! So what is space-time made of? Stop avoiding the question. I say space-time is not a physical thing. You say that it is, the burden of proof is on you to prove that it is. GO! What is your proof?

Science defines observations and experiments. Our current observations do not allow us to infer a coherent unified picture of the true nature of the classical(macro) and quantum scale.



But reality(the state of existence of everything) is what you are inquiring about. A fundamental unified description of spacetime is actually Reality. You have only been asking about what reality is in this thread. No one knows, niemand weiss, никто не знает, comprendo??..

Does this provide proof that space-time is a physical thing? NO. SO FAR NO EVIDENCE.

Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime(yet). Speculations and hypothesis about what fundamentally spacetime might be, are not a scientific definition of "spacetime". What you are looking for lies in the future.

So what you are saying is that you cannot provide any evidence that space-time is a physical thing. You say that space-time is a physical thing yet you cannot provide any scientific evidence to back up your claims. STOP THE DOUBLE TALK and just provide evidence that space-time is a physical thing.

Space in qm is very diffrent from the picture of space in relativity and classical mechanics. For all intents and purposes, a good case can be made that spacelike separation does not exist, based on Bell's theorem.

The only hint we have from the purported canditate for unified theory points to spacetime not being fundamental:

"Is spacetime fundamental?
Note that there is a complication in the relationship between strings and spacetime. String theory does not predict that the Einstein equations are obeyed exactly. String theory adds an infinite series of corrections to the theory of gravity. Under normal circumstances, if we only look at distance scales much larger than a string, then these corrections are not measurable. But as the distance scale gets smaller, these corrections become larger until the Einstein equation no longer adequately describes the result.
In fact, when these correction terms become large, there is no spacetime geometry that is guaranteed to describe the result. The equations for determining the spacetime geometry become impossible to solve except under very strict symmetry conditions, such as unbroken supersymmetry, where the large correction terms can be made to vanish or cancel each other out.
This is a hint that perhaps spacetime geometry is not something fundamental in string theory, but something that emerges in the theory at large distance scales or weak coupling. This is an idea with enormous philosophical implications."

http://www.superstringtheory.com/blackh/blackh4.html .

STILL NO SCIENTIFIC EVIDENCE TO BACK UP YOUR CLAIM THAT SPACE-TIME IS A PHYSICAL THING! Everyone take note that no evidence that space-time is a physical thing has been presented so far. Lots of run-a-round, but no science, NONE! Science, science, science, this is so easy, just provide scientific evidence. If you can not do this then I will have to assume that you are just making this whole thing up.

Are you a time traveller holding a 3000 Mpix camera? Reference please of a unified picture of spacetime.


Suppose you were a time traveller coming from year 3112. Why would your frog view theory of the true nature of spacetime be considered complete? For all intents and purposes, this might be forever impossible.

Forget this time traveler stuff, if space-time is a physical thing then it is physical now and now and now, show your evidence now.

THERE HAS NOT BEEN ONE PERSON ON THIS PLANET WHO HAS DESCRIBED SPACE-TIME AS A PHYSICAL THING IN SCIENTIFIC TERMS OR LAWS ACCORDING TO SCIENCE, THIS INCLUDES EINSTEIN. YOU NEED TO PROVIDE EVIDENCE TO THE CONTRARY IN ORDER TO PROVE YOUR POINT.

If you want to believe that space-time is a physical thing then just provide scientific evidence that backs up your claim. I am not asking for something unusual, just asking for evidence. Where is your evidence? Where is the science? So far nowhere to be seen.

Man up, follow the rules of this forum, or just admit that maybe there is no science that states space-time is a physical thing.

You, along with the others who believe space-time is a physical thing have been given ample opportunity to prove your point regarding space-time. Now is the time to blow me out of the water and provide your proof. I will drop this subject all together, in fact you will not hear from me again if anyone can provide scientific proof that space-time is a physical thing according to how science defines “physical” and “thing”.

I say that everything that exists and we can perceive with our senses is either a particle or a wave. If you disagree then please provide evidence to the contrary. Otherwise, if you think that space-time is a physical thing then provide evidence that it is a particle or a wave.

Space-time is physical in what way? Period.

 

[Dale]

I define "physical" and "thing" the same as any definition found in any standard dictionary.

Excellent, I am glad you have changed your mind. Then http://www.merriam-webster.com/dictionary/physical" definition 1a of "thing" is "a matter of concern". Since time and space are a matter of concern in every successful theory of physics then they are clearly physical things according to standard dictionary definitions.

 

[john 8]

Excellent, I am glad you have changed your mind. Then http://www.merriam-webster.com/dictionary/physical" definition 1a of "thing" is "a matter of concern". Since time and space are a matter of concern in every successful theory of physics then they are clearly physical things according to standard dictionary definitions.

So what is space-time made of? Do you want to say that space-time is a "of or relating to physics"? Is that an entity that exists?

"A matter of concern" is being influenced by a mass?

So what is it? Space-time is a "of or relating to physics" Is that a thing that is being influenced by a mass?

Space-time is "a matter of concern" Is that being distorted by a mass?

Come on! What is space-time made of?

 

[john 8]

Define "physical". Then define "Thing". Without these definitions, we are talking in different languages..

Physical as defined in any standard or scientific dictionary.

GR in the words of Wheeler:

“Spacetime tells matter how to move; matter tells spacetime how to curve.”

Spacetime can curve in the presence of immense gravity, why would it not be considered as much a thing as what you refer to as "Matter", which is nowhere being solid or absolute?..

So space-time is made of what?

Science defines observations and experiments. Our current observations do not allow us to infer a coherent unified picture of the true nature of the classical(macro) and quantum scale.



But reality(the state of existence of everything) is what you are inquiring about. A fundamental unified description of spacetime is actually Reality. You have only been asking about what reality is in this thread. No one knows, niemand weiss, никто не знает, comprendo?




Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime(yet). Speculations and hypothesis about what fundamentally spacetime might be, are not a scientific definition of "spacetime". What you are looking for lies in the future.?..

So science DOES NOT SAY anything concrete about the true nature of spacetime. Screw speculations. Science does not say space-time is a physical thing, yet you along with others believe that space-time is a thing. You now know that science does not agree with your assertions. Space-time is NOT a physical thing. PERIOD.

Space in qm is very diffrent from the picture of space in relativity and classical mechanics. For all intents and purposes, a good case can be made that spacelike separation does not exist, based on Bell's theorem.

The only hint we have from the purported canditate for unified theory points to spacetime not being fundamental:

"Is spacetime fundamental?
Note that there is a complication in the relationship between strings and spacetime. String theory does not predict that the Einstein equations are obeyed exactly. String theory adds an infinite series of corrections to the theory of gravity. Under normal circumstances, if we only look at distance scales much larger than a string, then these corrections are not measurable. But as the distance scale gets smaller, these corrections become larger until the Einstein equation no longer adequately describes the result.
In fact, when these correction terms become large, there is no spacetime geometry that is guaranteed to describe the result. The equations for determining the spacetime geometry become impossible to solve except under very strict symmetry conditions, such as unbroken supersymmetry, where the large correction terms can be made to vanish or cancel each other out.
This is a hint that perhaps spacetime geometry is not something fundamental in string theory, but something that emerges in the theory at large distance scales or weak coupling. This is an idea with enormous philosophical implications."

http://www.superstringtheory.com/blackh/blackh4.html





Are you a time traveller holding a 3000 Mpix camera? Reference please of a unified picture of spacetime.


Suppose you were a time traveller coming from year 3112. Why would your frog view theory of the true nature of spacetime be considered complete? For all intents and purposes, this might be forever impossible.

I asked for a scientific definition or reference that states space-time is a physical thing. You said that "Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime"

You are wrong! Science does say something concrete about space-time. The definitions that you found do not agree with what you want to believe so now you want to say science is silent. You can see that science does not recognize space-time as a physical thing.

Boo Hoo! Stop being religious and start being a scientist, physicist. Space-time is NOT A physical thing. Science says so.

LOOK AT THE EVIDENCE!

You cannot find any agreement in the scientific community to support your BELIEF.

 

[Fredrik]

I asked for a scientific definition or reference that states space-time is a physical thing. You said that "Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime"

You are wrong! Science does say something concrete about space-time. The definitions that you found do not agree with what you want to believe so now you want to say science is silent. You can see that science does not recognize space-time as a physical thing.

Boo Hoo! Stop being religious and start being a scientist, physicist. Space-time is NOT A physical thing. Science says so.

LOOK AT THE EVIDENCE!

You cannot find any agreement in the scientific community to support your BELIEF.

Not this again. John, we're really sick of this. At least I am. We have tried to explain these things to you many times, but you have ignored all the responses you got. This isn't going anywhere.

 

[jnorman]

back to the original question - i was under the impression that plank's constant indicated that spacetime was quantized. ie, spacetime is not subdividable beyond the plank length and plank time. is this incorrect, and why? thanks.

 

[Dmitry67]

back to the original question - i was under the impression that plank's constant indicated that spacetime was quantized. ie, spacetime is not subdividable beyond the plank length and plank time. is this incorrect, and why? thanks.

I was thinking that too :) But then people explained me that space is not made of "pixels": it is smooth, but distance is operator, so every time you calculate it, you get an integer value, while the coordinates can be real.

 

[Halcyon-on]

Is Spacetime Smooth?

Yes, they are (compact) smooth dimensions.

 

[Fredrik]

back to the original question - i was under the impression that plank's constant indicated that spacetime was quantized. ie, spacetime is not subdividable beyond the plank length and plank time. is this incorrect, and why? thanks.

It's certainly incorrect in general relativity, since that's a classical theory. Some version of the idea you're describing is likely to hold in a quantum theory of space and time, but we're not quite there yet.

 

[Dale]

Hi john8,

Do you agree or disagree with the statement that time is "a matter of concern of or relating to physics"?

So what is space-time made of?

Being made of something isn't part of the cited definitions of "physical" or "thing". If you would like to use a different definition that incorporates the requirement that "physical things" be "made of something" then please be explicit.

The rest of your post just follows from the fact that you seem to be using some super-secret personal definition that you don't wish to share. I have always been clear and forthright as to how I define any given term in our discussions. You, on the other hand, have been very evasive and hesitant with providing your definitions, so it is not a surprise that this semantic argument is going nowhere.

Physical as defined in any standard or scientific dictionary.

I am going to call "BS" on this. I have cited a standard dictionary definition of "physical thing" which clearly applies to space and time, and you have rejected it. Your definition obviously includes that a "physical thing" must be "made of" something, so stop hiding from the question and give us your definition.

 

[Bob_for_short]

Is Spacetime Smooth?

As a practising physicist, I will tell you - it completely depends on what you put in space and what boundary conditions you use.

 

[bebe7]

Excellent, I agree, it depends on the parameters/conditions. When a supermassive star collapses and creates a black hole, space and time will bend.

I know its a hypo but warpd drive is based on bending the fabric of space-time.

 

[strongstring]

Spacetime is definitely not 'smooth'. There is a feature known as quantum foam whereby quantum fluctuations in vacuums, matter and any other situation the space time might be in, afffects the texture of spacetime. The quantum fluctuations cause the spacetime fabric to be very 'rough the different energy levels cause it to spike and dip in areas. This is one of the factors that greatly improved the support of string physics, this is because point particles, (infinately small), can get stuck in the quantum foam, and answers for probability come up as infinty, which is nonsense. Strings however are too big to fit in these gaps and are unaffected.

Thanks
William Evans

 

[strongstring]

So what is space-time made of? Do you want to say that space-time is a "of or relating to physics"? Is that an entity that exists?

"A matter of concern" is being influenced by a mass?

So what is it? Space-time is a "of or relating to physics" Is that a thing that is being influenced by a mass?

Space-time is "a matter of concern" Is that being distorted by a mass?

Come on! What is space-time made of?

Because space time infllicts the force of gravity upon matter and energy, it is theorized to be made of gravitons, the messenger particle for gravity. another theory sugests that it is time itself, (which i really disagree on).

Thanks
William Evans

 

[Halcyon-on]

Spacetime is definitely not 'smooth'. There is a feature known as quantum foam whereby quantum fluctuations in vacuums, matter and any other situation the space time might be in, afffects the texture of spacetime. The quantum fluctuations cause the spacetime fabric to be very 'rough the different energy levels cause it to spike and dip in areas. This is one of the factors that greatly improved the support of string physics, this is because point particles, (infinately small), can get stuck in the quantum foam, and answers for probability come up as infinty, which is nonsense. Strings however are too big to fit in these gaps and are unaffected.

Thanks
William Evans

This is not physics! This is only a supposition, a conjecture not demonstrated by facts or experiment. The quantum foam is a definitely fascinating, but we are far from saying that "spacetime is definitely not smooth" because of the several incongruences of the theory.

 

[WaveJumper]

Physical as defined in any standard or scientific dictionary.

Space has properties and those properties belong to an object. They don't belong to a 'nothing'.

So space-time is made of what?

Just because no one has been able to find the "atoms" of space, doesn't mean that anything goes.

So science DOES NOT SAY anything concrete about the true nature of spacetime. Screw speculations. Science does not say space-time is a physical thing, yet you along with others believe that space-time is a thing. You now know that science does not agree with your assertions. Space-time is NOT a physical thing. PERIOD.

Science does not clearly state what 'physical' is, it's a matter of debate, but that's offtopic. Using your preconceived models of observing condensed energy as solid physical stuff and extrapolating it back to space is obviously not going to work. Space is definitely not a form of condensed energy, but its properties hint that it's definitely not a 'nothing'. BTW, no human has ever come across, or even been able to comprehend what 'Nothing' is. There is no nothing, the concept of Nothing is a misconception. Just because "nothing" works when you talk to your friends and children, doesn't mean that you can apply it in fundamental physics.

I asked for a scientific definition or reference that states space-time is a physical thing. You said that "Science is silent(DOES NOT SAY) anything concrete about the true nature of spacetime"

You are wrong! Science does say something concrete about space-time. The definitions that you found do not agree with what you want to believe so now you want to say science is silent. You can see that science does not recognize space-time as a physical thing.

Boo Hoo! Stop being religious and start being a scientist, physicist. Space-time is NOT A physical thing. Science says so.

LOOK AT THE EVIDENCE!

You cannot find any agreement in the scientific community to support your BELIEF.

Where is the evidence that "nothing" exists? What is nothing? Where am I supposed to find it or evidence of its existence?

 

[p764rds]

Space-time could not be smooth because it would need too much 'precision' to define the smallest metrics. At around the plank length the number of bits needed to define position (x,y,z and t) is around a few KB. But it would be a huge number of bits at near infinite smallness (eg Gbytes!). It is same problem as renormalization and cut off (infra red and ultra violet). - Probably around plank lengths at a guess.

Below a certain small length there is no possible action because its undefined. No actions as the length approaches zero - either at high or low energy because the length would be undefined. Its not that its outside space-time, its because any length below this cut-off is quite simply unknown or undefined. There can be no value associated with it.

 

[physical1]

There is no nothing, the concept of Nothing is a misconception. Just because "nothing" works when you talk to your friends and children, doesn't mean that you can apply it in fundamental physics.

Where is the evidence that "nothing" exists? What is nothing? Where am I supposed to find it or evidence of its existence?

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

http://c2.com/cgi/wiki?NothingIsAnything"

p.s. if there is "no nothing" then how do you define "no". No is just another word for nothing. Double none and double nuttin!

 

[WaveJumper]

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

http://c2.com/cgi/wiki?NothingIsAnything"

p.s. if there is "no nothing" then how do you define "no". No is just another word for nothing. Double none and double nuttin!

If Brukner-Zeilinger Information Interpretation is true(as i beleive), something and nothing are all the same - they are information. There are no paradoxes related to space(the disappearance of space under certain conditions, universe's boundery conditions, something out of nothing, entanglement and Bell's theorem, Zeno-like paradoxes related to whether space is continuous vs discrete, the finely tuned initial conditions, etc.). There are no time paradoxes either - the flow of time, the arrow of time, the abscence of universal now, backwards in time qausations, etc.) Hence i define "nothing" as a wrong mental image that's useful for contrasting something against a 'nothing'. It may have to do with death; if we were immortals, we'd hardly ever come up with the notion of nothing. If the Information interpretation is right, "no nothing" has the same fundamental 'content' as "nothing", just in a different sequence of bits.

 

[p764rds]

Hahahaha. Yes the question of what is "nothing" is something programmers often ask.

There is a physical 'nothing' which is where you 'cannot place an object' (Democritus et al) and where 'God lives' as someone told me yesterday.

But in our space-time the real 'nothing is a piece of undefined space-time.
Between 0.008 plank lengths and .007 plank lengths is nothing because its not defined - simple.

 

[Pythagorean]

I don't think anyone really knows, at this point. It hasn't been proved either way, but we do know that if it's quantized it must be a pretty fine-grained quantization. Reiner Hedrich, for one, has written a number of papers on the idea of quantum spacetime.

If quantum mechanics is universally true, then it's quantized. If quantum gravity turns out true, then spacetime must be quantized, so gravitons would mean quantum spacetime. As would chronons, if you believe in quantum time, but that's pretty speculative at this point.

Right now most (non-QM) models start with an assumption of smoothness, but hey--a HD TV looks pretty smooth from a distance, but we all know there are pixels when you look closely enough. I'd like to see it proved one way or the other; I'm very curious to find out which way it comes out.

--Mike from Shreveport

Thank you for this straight forward reply! I was surprised to see this thread still going.

I would just like to add (to make sure the more credible philosophical replies in this thread don't go ignored) that it's not necessary that one or the other be universally true. As Frederik and DrFaustus had replied originally, it could just be that these models are forever doomed to be limited to their 'appropriate places'.

I think you and I understand each other though and this reply is more tailored to the line of thinking I was experiencing at the time I asked the question. I've flirted many times with the idea of quantized time, but I'm hoping to get this whole quantized space business sorted out first!

 

[p764rds]

I've flirted many times with the idea of quantized time, but I'm hoping to get this whole quantized space business sorted out first!

Time must be granular for the same reason that space must be granular - the reason is, that the precision of the metrics (space an time) cannot be infinite.

You can view this as cut-off, capping, renormalization in QFT parlance.

Or, better, viewed in informational terms - the amount of data to needed to locate 1 Planck length in space-time is a few kilobits. There must be a limit that prevents it from being many giga bytes. Why? too much data would not be able to be processed in the required time. That limit will be one of the constants for this universe.

(Zeilinger work is heading in that direction)

 

[Halcyon-on]

Time must be granular for the same reason that space must be granular.

This is surely true in your own universe. But in the real universe the only think that we can state for sure is that the energy-momentum is quantized (granular), not the space-time.

 

[aussie_mike]

I worked with an electronics engineer who was completing his PhD in Physics, and he was of the opinion that space time is granular. Quantum physics and Planck constants seem to imply this. The clincher for me is that at the tiniest level a particle goes from point A to point B without traveling through the "space" between the two. Does not that define spacetime as granular?

 

[Dmitry67]

I also made a mistake assuming that minimal length implies that space is something like an array of pixels. But it is wrong analogy.

 

[jeff_kosela]

i didnt read many,... of the forums but an idea that came to mind is, on the level of quantum physics, understanding that matter is energy, i would say, no form, or build up of matter would affect super-symmetry, so in a... equation valuing these properties, id say space time,(or decay...) is constant.

 

[d9090]

If the action of Mass is quantized, then so must be the action of a "particle" with Mass on Space-Time, and the action of Space-Time on a "particle" with Mass.

Continuous Space-Time makes the mathematics easier; discrete Space-Time is closer to a "realistic" theory were the "action" known as Gravitation actually described.

But don't mind me: I'm a kook who swore off "point particles" and "ponderous matter" for Lent years ago.

d.

ps. the whole "no-thing" thing this is amusing. Surely no Marvel comic fan is getting sucked into that one! No-prizes really do exist! But then if you toss the basic idea of "reality" or "existence" you might expect a little confusion here and there. :-)

------
Emergence of Novelty: Bane of Reductionism
'As above' is not necessarily so 'below'.