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Nick666 said:Isnt the infinite energy of the vacuum a genuine infinity in nature ?
This is new to me. Current theory is that the energy in the universe is finite.
Nick666 said:Isnt the infinite energy of the vacuum a genuine infinity in nature ?
it is a mental (mathematical) construct but an essential one...
Naty1 said:jambaugh:
Be cautious! Such firm "beliefs" may blind you! : such "beliefs" have tripped up physicsts for all of history and prevented them from understanding new theories and experimental findings .
also recall that light was once viewed as traveling in ether, mass was "solid", space and time were "fixed and immutable", a proton is a fundamental particle, dark matter and dark energy are "impossible" (just mathematical constructs) etc,etc,etc.
Just keep an open mind. For example, if matter is both a particle and a wave,and equivalent to energy, why can't space and time be as well?? (after all, they all came from the same place: nowhere ("empty" space))... Nobody knows.
http://en.wikipedia.org/wiki/Vacuum_energyfleem said:This is new to me. Current theory is that the energy in the universe is finite.
Nick666 said:http://en.wikipedia.org/wiki/Vacuum_energy
It says here that the energy of the vacuum is infinite, but they renormalize it. Whatever that means.
As a non-scientist, you should stay quite calm when it comes to these points...
Naty1 said:valid point; And scientists, especially calm...
This caution runs both ways... but if you look at history the mistakes made in "too dogmatic beliefs" have been in reification of models and failure to pay attention to operational meaning. Einstein was able to revise his view of time and thence unify space-time by acknowledging that "time is what a clock indicates" and "distance is what a measuring rod measures". Hence the reality is in the dynamics of the clock and the measuring rod. His open-mindedness on this point allowed him to then generalize the previously fixed relationships between these. However the success of his theory led to the opposite position, with followers taking the geometric model as an ontological fact. This tends to be the nature of scientific progress.Naty1 said:jambaugh:
Be cautious! Such firm "beliefs" may blind you! : such "beliefs" have tripped up physicsts for all of history and prevented them from understanding new theories and experimental findings .
Again the aetheric interpretation of light was a mistake of reifying a model. It was in acknowledging that the reality of the aether was not necessary to describe the dynamics of light which led to relativity. Relativity doesn't assert the ether is real and doesn't assert the ether is unreal. It shows that the question is irrelevant because the physics is in the empirical observations of how light behaves.also recall that light was once viewed as traveling in ether, mass was "solid", space and time were "fixed and immutable", a proton is a fundamental particle, dark matter and dark energy are "impossible" (just mathematical constructs) etc,etc,etc.
My mind is quite open, but I am skeptical of many of the "kludges" (such as dark energy/matter and inflation) to get them to fit empirical data.Just keep an open mind. For example, if matter is both a particle and a wave,and equivalent to energy, why can't space and time be as well?? (after all, they all came from the same place: nowhere ("empty" space))... Nobody knows.
Astronomical observations have shown that the (energy) density of vacuum is rather small. It's certainly not infinite.Nick666 said:http://en.wikipedia.org/wiki/Vacuum_energy
It says here that the energy of the vacuum is infinite, but they renormalize it. Whatever that means.
Here Here!DrFaustus said:Pythagorean -> You keep asking questions about "Reality" (whatever that is) and are trying to come up with answers starting from physics. And this is the main problem you're having, that is not realizing that we can only infer properties about "Reality" by working out the consequences of the assumptions we make. [...] Bottom line, do not mistake a "model" for "Reality".
Yes. I agree that renormalization methods are valid and meaningful in the successful QFT of the standard model. Your point about the necessity of renormalization and how it relates to the canonical commutation relations is an important one. My past research has been in deformation expansion of the canonical commutation relations. The "necessity" of the canonical relations themselves stems from the very use of a field theory namely the fibration of space-time-gauge parameters into gauge fields over a space or space-time. The foundational assumption is that each point in space (or even each cell of space) has a physical quantum system associated with it. One is forced to count their ground contributions leading to the divergent vacuum energies. (One interesting result I've yet to publish is a relativity to the bosonic vacuum which I think could "hook" into GR.)jambaugh -> A quick remark on renormalization. It is true that in most of the books on QFT it does indeed appear as a "quick fix", but it not need be so. The mathematical reason for divergences to appear (at least some of them) is because a rigorous mathematical treatment of quantum fields requires quantum fields to be "operator valued distributions" and not operators. The reason is simply that you cannot satisfy the canonical commutation relations with operators and because if you consider the CCR at the same spacetime point, e.g. for the simple scalar field you have [tex] [\varphi(t,\vec{x}), \partial_t \varphi(t,\vec{x})] = \delta(0) [/tex], which is infinite, or better, meaningless.
I agree (w.r.t. QFT) and of course the non-renormalizability of Grav in QFT suggests an alternative to QFT is necessary for the next theory. (Hence string-brane mathematics but as I said I see these as promulgating some of the same problems).Is renormalization gone? Not really. But it does not involve "subtractions of infinite quantities" as it usually does. Renormalization is now carried over as the "extension of products of distributions to points where such a product is ill defined". But this can be, and is done in a finite way. And also perturbation theory is based on causality so the formalism is perfectly well defined at all steps (this is the method of Epstein and Glaser). The reason why this is not thought is that it involves a lot of mathematical work and is generally not needed in current physical research. In any case, this really suggests that renormalization is in some sense an intrinsic feature of QFT.
Thanks for the references I'll compare them to my own library. However as I'm not looking to improve theory within QFT but rather to supplant it I'm not as concerned (yet) with improved expositions of renormalization or field theory. I may take a look at the Scharf book.(For the latter point, you can have a look at Bogoliubov's book "Introduction to the theory of quantized fields". As for renormalization being carried over in a mathematically rigorous way by handling products of distributions, have a look at "Finite QED" by Scharf.)
DrFaustus said:But questions like "Is spacetime a manifold?" are on the one hand not for physicists to answer (as you have noted it easy to cross the borderline with philosophy) and on the other completely irrelevant. As long as your assumptions allow you to describe and predict the result of experiments, that's all you need.
DrFaustus said:Bottom line, do not mistake a "model" for "Reality".
I am open minded but I don't buy every new speculation just because it generates juicy headlines in the popular media. (E.g. FTL tunnelling). Neither do I take orthodox views...
DrFaustus said:As for renormalization being carried over in a mathematically rigorous way by handling products of distributions, have a look at "Finite QED" by Scharf.)
malawi_glenn said:as far as we/I know, yes, it is smooth
Civilized said: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.
Pythagorean said:Is Spacetime Smooth?
Smooth: infinitely differentiable
Pythagorean said:Is Spacetime Smooth?
Smooth: infinitely differentiable
ibcnunabit said: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 said: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 said: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.
WaveJumper said: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 said: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 said: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 said: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:.
WaveJumper;2283804 [i said:"Time and space and gravitation have no separate existence from matter."[/i]
:.
WaveJumper said: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 said: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 said: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).
john 8 said: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 said: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 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 said: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 said: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.
WaveJumper said: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.