This Time - What a Strange Turn of Events by Philip Gibbs

Hello Phillip,

Loved your essay!

You write, "Minkowski used the symmetry in the Lorentz transformation to bring together space and time making them merely different dimensions of spacetime. Yet time is somehow different in our mind."

But time is also very different from space in our *physical* reality and relativity's equations!

In Einstein's 1912 paper, he wrote the fourth coordinate x4 as:

x4 = ict

x4 is the only coordinate that depends on time and the velocity light. Egro, x4 is very different from the three spatial dimensions (x1, x2, x3). In fact, x4 is expanding relative to the three spatial dimensions, given by dx4/dt = ic.

And starting with a 4D space in which the fourth dimension is expanding relative to the three spatial dimensions (dx4/dt=ic), all of relativity may be derived, while entropy and time's arrows and assymetries may be accounted for.

You write "Part of the mystery of time is to understand where this signature comes from. Why three plus signs for space and only one minus sign for time?"

And also, why the c^2 in front of time? So many physicists completely ignore these questions, while also compltely ignoring the great problems Godel had with "time" and the block universe, which my MDT theory liberates us from.

My paper solves these mysteries, while also accounting for time's definitive arrows and assymetries, quantum mechanics' nonlocality and entanglment, and entropy.

You ask, "from what bow did time's arrow take flight?"

It took flight from a more fundamental universal invariant--the fourth dimension is expanding relative to the three spatial dimensions at c, or dx4/dt = ic. Ergo time and all its arrows and assymetries.

http://fqxi.org/community/forum/topic/238

Time as an Emergent Phenomenon: Traveling Back to the Heroic Age of Physics by Elliot McGucken

"In his 1912 Manuscript on Relativity, Einstein never stated that time is the fourth dimension, but rather he wrote x4 = ict. The fourth dimension is not time, but ict. Despite this, prominent physicists have oft equated time and the fourth dimension, leading to un-resolvable paradoxes and confusion regarding time's physical nature, as physicists mistakenly projected properties of the three spatial dimensions onto a time dimension, resulting in curious concepts including frozen time and block universes in which the past and future are omni-present, thusly denying free will, while implying the possibility of time travel into the past, which visitors from the future have yet to verify. Beginning with the postulate that time is an emergent phenomenon resulting from a fourth dimension expanding relative to the three spatial dimensions at the rate of c, diverse phenomena from relativity, quantum mechanics, and statistical mechanics are accounted for. Time dilation, the equivalence of mass and energy, nonlocality, wave-particle duality, and entropy are shown to arise from a common, deeper physical reality expressed with dx4/dt=ic. This postulate and equation, from which Einstein's relativity is derived, presents a fundamental model accounting for the emergence of time, the constant velocity of light, the fact that the maximum velocity is c, and the fact that c is independent of the velocity of the source, as photons are but matter surfing a fourth expanding dimension. In general relativity, Einstein showed that the dimensions themselves could bend, curve, and move. The present theory extends this principle, postulating that the fourth dimension is moving independently of the three spatial dimensions, distributing locality and fathering time. This physical model underlies and accounts for time in quantum mechanics, relativity, and statistical mechanics, as well as entropy, the universe's expansion, and time's arrows.

"

You write, "So we know that the source of the direction of time is the big bang - the cosmological singularity of spacetime predicted using the theory of general relativity - but we still don't know why." The universe's expansion also arises because dx4/dt = ic. The universe can yet contract under gravitational forces while the fourth dimension yet exapnds, so time would not flow backwards if the universe begins to contract under gravitational forces.

You write, "The leading candidate for a theory of quantum gravity is superstring theory." Have you read Lee Smolin's THE TROUBLE WITH PHYSICS and Peter Woit's NOT EVEN WRONG? Also, have you read STRING THEORY IN A NUTSHELL? On the first page they state that String Theory is a non-finite theory. I'm not so sure I'd be holding out on ST, nor Quantum Gravity of any form for that matter, at least until we see a graviton or two, or a consistent theory that more than one physicist agrees on.

You conclude with, "To come to terms with such physics we must be prepared to work without the use of temporal causality. It is a hard principle for physicists to give up. Some are prepared to give up all structure on spacetime except causality. They don't go far enough.

The universe must be described by a vast ensemble of events devoid of spacetime structure. These events are linked by a web of possibilities allowed by the huge underlying of symmetry of string theory. Time emerges only because a solution fits in which the Lorentzian signature of spacetime prevails."

I would argue that time emerges because of the universe's fundamental invariant from where all motion arises--the fourth dimension is expanding rletaive to the three spatial dimensions: dx4/dt = ic.

Instead of forgetting space, causality, and time--which is very real at this moment as I am running late--perhaps we should forget quantum gravity for a moment, as well as non-physical models which do away with time, space, and causality? For while space and time manifest themselves throughout classical, relativistic, and quantum mechanical physics and our empirical reality, the graviton has never been seen.

And yet change *is* seen. And finally an equation has stepped forth to mary change to the fundamental fabric of space-time: dx4/dt = ic, where change belongs, along with time's arrows and assymetries. All of relativity arises from this, as does time and nonlocality, as well as entropy and all the dualities--wave/particle, space/time, mass/energy--and too it liberates us from the block universe and frozen time (while also liberating us from frozen progress in theoretical physics).

Do we have to quantize gravity? Could it be that nature is as it is, and that God or the Prime Mover/Creator came up with both QM and GR, which seem to coexist perfectly well in their current forms? For instance, this laptop computer is powered by quantum phenonema, and too, it is held on my lap by gravity. Each one has a role, and each seems perfectly content to play it. Perhaps both mathematical predictions and the experimental search for gravitons has fallen short because gravitons do not exist. Now this is no reason to stop looking, but too, it is not exactly a reason to keep looking, and it is certainly not a reason to get rid of time, space, and causality, which do seem to exist, as my laptop's clock tells me I am running late, yet again, and I have to drive through space, up the 101. :)

A book you would enjoy is Freeman Dyson's THE SCIENTIST AS REBEL. On page 219 Freeman Dyson writes,

"(Brian) Greene takes it for granted, and here the great majority of physicists agree with him, that the division of physics into seperate theories for large and small objects is unacceptable. General relativity is based on the idea that space-time is a flexible structure pulled and pushed by material objects. Quantum mechanics is based on the idea that space-time is a rigid framework within which observations are made. Greene believes there is an urgent need to find a theory of quantum gravity that works for large and small objects alike. . . As a conservative, I do not agree that a division of physics into separate theories for large and small is unacceptable. I am happy with the situation in which we have lived for the last eighty years . . . The question I am asking is if there is conceivable way we could detect the existence of individual gravitons. I propose as an hypothesis that it is impossible in principle to observe the existence of individual gravitons." --Freeman Dyson, THE SCIENTIST AS REBEL, pp 219-220

While there is no evidence for gravitons, nor consistent theory of quantum gravity, it is yet possible to observe, contemplate, experience, and witness time in multiple manners and ways.

Space, time, temporal causality--all of these are very, very real *physical* entities! And my paper and Moving Dimensions Theory show that time, and thus causality, emerge from a deeper source--a hitherto unsung fundamental invariance of the universe--the fourth dimension is expanding relative to the three spatial dimensions at the rate of c, or dx4/dt = ic.

http://fqxi.org/community/forum/topic/238

Thanks again for the wonderful, well-written paper which packed a lot in to only ten pages. :)

One last thing--a photon gains energy as it approaches a gravitational mass. It is blue-shifted due to the changes in the geometry of the local space-time. However, nothing *physically* is being added to the photon to blue-shift its energy. Ergo no need for gravitons.

Best,

Dr. E

Dr E. Thanks for taking the time to read my essay and make so much comment. I'll respond to some of your points now and come back to others when I have more time. I read your essay too, It is interesting but very different from my approach, so I doubt we'll find much common ground! Still it is interesting to discuss.

You asked "Have you read Lee Smolin's THE TROUBLE WITH PHYSICS and Peter Woit's NOT EVEN WRONG?".

Yes I have. I agree with some of what they say and diasagree with some other parts. Smolin and Woit actaully have different messages.

Smolin talks quite negatively about string theory but his overall message is not that string theory is wrong. His message is that any theory of quantum gravity whether ST or something else should be done in the spirit of general relativity, which means it needs to be background independent. Because of this he advocates that too much funding is going to string theorists who work from the perspective of particle physicists and more funding should go to alternative relativity based approaches.

I am more positive about string theory (although I am not a string theorist as such) but I agree with Smolin's message on background independence. I dont have much to say about the funding issue since it does not really affect me.

Woit's message is much stronger. He says that string theory has failed as a TOE because he thinks it will not be testable/falsifiable. I disagree with him but I still dont disagree with him about everything. For example I that sometimes string theory is often overhyped in the media.

I think it is a shame if this has grown into a bit of a feud between string theorists and "alternatives" such as LQG. More progress is made when concepts from one approach are applied to another but that seems to be not happening.

You also ask "have you read STRING THEORY IN A NUTSHELL? On the first page they state that String Theory is a non-finite theory."

I haven't read that one. String theory as a perturbation series probably diverges but the same thing happens in qunatum field theory. The point is that we need a well defined non-perturbative formulation which we dont have yet. My idea is to use symmetry (especially event symmetry) as the principle to help find it.

Looking through the essays, I think I may be the only author so far who sees string theory as relevant to the question. I dont think that is representative of the physics community as a whole.

Dr E says: You conclude with, "To come to terms with such physics we must be prepared to work without the use of temporal causality. It is a hard principle for physicists to give up. Some are prepared to give up all structure on spacetime except causality. They don't go far enough."

The major paradism shifts of science have been about giving up concepts we thought were fundamental and replacing them with something else. Copernicus abolished our idea that we are at the centre of the niverse. Einstein gave up absolute space and time. In quantum theory we lost determinancy.

Physicists recognise that we need to give up more cherished concepts to get at quantum gravity. Different approaches are characterised by what people thiunk should be given up and what should be kept. Perhaps we need to give up everything and the big question is just what order to do it in.

The concepts that I vote for keeping the longest are symmetry, quantization and information. These are things which seem more fundamental to me than geometry and temporal causality. Some physicists advocate keeping causality. I think that time symmetry (i.e. CPT) runs deeper than the asymmetry of time's arrow. Low entropy is just a local feature of cosmology and the way it affects the organisation of information.

My course is close to that of Rovelli when he says "Forget Time". He also notes that some people want to keep time and cites a paper by Smolin. Smolin uses temporal causality in his theories about cosmic evolution. Similar notions are fundamental to Eternal Inflation which is popular with some string theorists. You can also look to approaches such as Causal Set Theory to see the way that some physicists have thrown out everything except cauasality. I think this is wrong. Symmetry is more fundamental. Temporal causality has to go.

Dear Philip,

I recall that we have been in email exchange for years ago and I remember your excellent home page!

I think that your idea about permutations has something in it. My main criticism is that the reduction of everything to combinatorics leads to a loss of diffeo-structures and even the notion of topology. For instance, the notion of mass requires not only continuity but also diffeo-structures and isometries if one believes that Poincare invariance is behind classical conservation laws. Of course, these symmetries can be seen as a special case of permutation symmetries but...!

Personally I believe that discretization -rather than discreteness- is fundamental as a geometric correlate for the finite resolution of quantum measurement and also cognition. If so, the replacement of space-time regions with sets of discrete points would become a key element in the construction of quantum states which could be seen as their own descriptions carry information about finite measurement resolution in self-referential manner. Physical states would be their own approximations!

The notion of finite measurement resolution and the possibility to improve it would give an infinite hierarchy of physical states as the number of resolved points increases and the number of elements in the permutation group in question increases. The limit of infinite-dimensional permutation symmetry would not be achieved.

Some comments concerning your Grassman algebra like structure.

First of all, this kind of algebra emerges also in TGD as the Clifford algebra of the infinite-dimensional "world of classical worlds" consisting of 3-D surfaces. This algebra is a canonical representation of so called hyper-finite factor of type II_1, an extremely beautiful mathematical structure discovered by von Neumann, and coding for a lot of modern theoretical physics (quantum groups, knot theory, etc...). You are probably aware of the connection.

The infinite-dimensional permutation group relates very closely to this algebra and emerges and the interpretation is as permutation group for braids consisting of infinitely large number of braid strands but all permutations acting on finite but unlimited number of strands. Finite measurement resolution poses a bound for the number of strands defining actually the dimension of the symplectic fusion algebra. Infinite-dimensional permutation group appears also in number theory. It can be seen as the Galois group of algebraic numbers containing all possible Galois groups assignable to finite-dimensional algebraic extensions of rationals.

In category theory, which is now making its way to physics, finite structures appear and permutations generalized to braidings in quantum theory and associations (bracketings) are the key combinatorial notions. I believe that category theory is the manner to formulate the notion of finite measurement resolution and its improvement in a mathematically elegant manner. I have been just developing symplectic counterpart of conformal field theory ( see my blog). This leads to a hierarchy of fusion algebras which resemble your fermionic operator algebras in many respects: for instance generators satisfy the rule x^2=0 which says that symplectic fields at same point annihilate each other: this guarantees absence of UV infinities. These algebras are not however Grassman algebras since grading is lacking.

Thank you for very interesting contribution,

Matti Pitkanen

Dr E says: "Space, time, temporal causality--all of these are very, very real *physical* entities!"

I absolutely agree that they are real. They are as real as the surface of the sea whose existence cannot be denied. Yet the surface of the sea is just an interface between air and water. If you could observe it at the atomic level you would find that its position is not so well defined and its existance is blurred. And when a storm blows up the surface of the sea can be broken. Eventually it breaks down into a foaming mess and the surface vanishes even at macroscopic scales.

The existance of spacetime is similar to the existance of the surface of the sea. At small enough scales it disappears and all you see are the particles and waves of matter. Spacetime geometry maps the relationships between the events where (and when) particles interact. At high enough temperatures the whole thing breaks up, spacetime evaporates.

Dr E asks "Do we have to quantize gravity?"

It is a frequently asked question and many people have offered detailed answers to it before so I'll just give my overall view.

We dont have any experimental result that requires quantum gravity and I doubt we will have one for a very long time. But general relativity and quantum mechanics as separate theories do not give a consistent theory of physics. There are realms where they must come together. Even as separate theories they break down. General relativity breaks down at a black hole singularity while the standard model of particle physics breaks down at high energies.

Somebody might try and claim that these things dont have or need explanation because we can never experience them, but one day we may be able to observe the gravitional radiation left over from the big bang and the effects of quantum gravity will be imprinted on it.

Perhaps you are saying that we can bring GR and QM together without quantum gravity. You suggest that there are no gravitons. I did not mention gravitons in my essay because gravitons are a feature of perturbation theory in quantum gravity. My approach is inherently non-perturbative so gravitons are not so important.

In whatever way you try to bring together GR and QM you face the same problems. Even if you try to describe the universe without quantum gravity you have to describe an interface between them. This is a hard constraint to meet. We dont yet have any complete description of how this could be done so whatever your views about quantum gravity there is still a hard problem that needs to be solved.

Quantum gravity is not necessarily about breaking gravity down into discrete quanta that you could call gravitons. Anything that brings GR and QM together in a mathematically consistent and complete way that fits existing experimental constraints would be a valid candidate for quantum gravity.

Dear Matti,

I'm pleased to see you in the competition. I agree with you about the mathematics of clifford algebras, braids, quantum groups, category theory etc.

It is a curious thing that these same mathematical ideas arise unforced in different approaches to quantum gravity. It must be a sign that they have some real relevance.

There are of course major differences in your approach and mine. The main ones would be firstly that I try to work within the confines of string theory while you see your appraoch as a generalisation of it, and secondly that you are motivated by cognitive ideas that I avoid. Yet when we do our maths there is much in common. The same is true of many different approaches. It is this convergence of mathematics that gives us hope that the quantum gravity puzzle is soluable even if further empirical input is some way off.

The necklace algebas I constructed have not been studied in much depth by mathematicians. It would be nice to know more about how they relate to the Kac-Moody and the Von-Neumann algebras for instance.

In my essay I did not go into depth about the maths because it would not be possible to do it justice in 10 pages but I am glad you have seen some of the cited papers. The simplest necklace algebras describe a supersymmetry that includes event-symmetry. It is an algebra of discrete fermions or qubits on strings. Once confined to strings the fermionic statistics can be generalised to anyonic statistics. The permutation groups become braid groups and the algebra is quantised.

It turns out that there is a quantisation procedure that can be repeated in the spirit of multiple quantization with a new dimension being added to the algebraic structure each time you quantise. Multiple quantisation is another recurring theme in physics. It was advocated by carl von Weisacker for many years. It made its appearance in string theory in the form of Green's Worldsheets for Worldsheets in the 1980s. Actually I think that Rovelli's idea of thermal time is also linked to this because thermalisation is analogous to quantisation and the time dimension emerges from it in the same way.

KG Schlesinger related multiple quantisation to forming functor categories. I think this is in the right direction but some extra twist is needed to complete the idea

To better undertsand the necklace algebras you need to study their invariants. This is similar to the problem of understanding the entanglement of qubits and it requires the mathematics of hyperdeterminants. Certain multipartite configurations are related to the exceptional groups as described by Michael Duff in his work on dualities in string theory. This is how I see my work making contact with the 9+1 dimensional formulation of string theory that is connected to the mathematics of the octonions and the group E8.

Thanks for the detailed responses, Philip!

Your words bring to mind the thoughts of a Nobel Laureate physicist: "The master antitheory of the age is the idea that there is no fundamental thing left to discover, so that the world we inhabit is simply a swarm of detail that belongs to no one and thus can be legitimately handled by business tactics-resource management, competitive advertising, survival of the fittest, and so forth. A corollary is that there is no absolute truth, but only products, like shirts or hamburgers, that one throws away when their usefulness is exhausted. Antitheories are dangerous ideologies not only because they impede inquiry but because they lull one into ignoring threats that one's opponents can exploit to their advantage." -A Different Universe, Reinventing Physics From The Bottom Down, Robert B. Laughlin, Winner of the Nobel Prize in physics for his work on the fractional quantum Hall effect.

Yes--string theory and loop quantum gravity are in many ways anti-theories that depend on "survival of the fittest" in a marketing/media-manipulation perspective, and thus make progress in theoretical physics impossible, resulting in the undeniable empirical evidence of zero progress in the last thirty years, at the cost of hundreds of millions of dollars.

One of the reasons MDT has received violent opposition from anonymous postdocs and professors is that it makes vast progress--both in asking and answering foundational questions. And such questions have generally been outlawed by those exploring Quantum Gravity, who tend to favor progressless physics and groupthink, as opposed to the honest exploration of foundational questions.

"Great spirits have always found violent opposition from mediocrities. The latter cannot understand it when a man does not thoughtlessly submit to hereditary prejudices, but honestly and courageously uses his intelligence and fulfills the duty to express the results of his thought in clear form. --Albert Einstein"

For instance, String Theorists and Quantum Gravitationists generally ban you from quoting Nobel Laureates in physics and talking about physics and physical reality. They do not like you talking about time, space, and causality, as they insist that such things are not real, while tiny, vibrating strings, ten to forty additional dimensions, and atoms of spacetime and "bouncing" universes *are* real. Basically it's an entire program of replacing physical reality, sceince, and physics with groupthink, mysticism, tyranny, PR hype, and well-funded bureaucracies--it's a cash-driven conquest. Today success is considered having one's anti-theory hyped on Fox News, while perhaps signing a book deal before one's fifteen minutes of fame expires--even though their theories state that time does not flow and isn't real. The math never adds up, and even the great John Baez has finally given up, and is jumping off the train after riding it for ten years in the block universe that MDT has freed us from:

http://www.edge.org/q2008/q08_5.html

"Loop quantum gravity was less ambitious than string theory. Instead of a "theory of everything", it only sought to be a theory of something: namely, a theory of quantum gravity.

So, I jumped aboard this train, and for about a decade I was very happy with the progress we were making. A beautiful picture emerged, in which spacetime resembles a random "foam" at very short distance scales, following the laws of quantum mechanics.

We can write down lots of theories of this general sort. However, we have never yet found one for which we can show that General Relativity emerges as a good approximation at large distance scales -- the quantum soap suds approximating a smooth surface when viewed from afar, as it were.

I helped my colleagues Dan Christensen and Greg Egan do a lot of computer simulations to study this problem. Most of our results went completely against what everyone had expected. But worse, the more work we did, the more I realized I didn't know what questions we should be asking! It's hard to know what to compute to check that a quantum foam is doing its best to mimic General Relativity.

Around this time, string theorists took note of loop quantum gravity people and other critics -- in part thanks to Peter Woit's blog, his book Not Even Wrong, and Lee Smolin's book The Trouble with Physics. String theorists weren't used to criticism like this. A kind of "string-loop war" began. There was a lot of pressure for physicists to take sides for one theory or the other. Tempers ran high. . .

I realized I didn't have enough confidence in either theory to engage in these heated debates. I also realized that there were other questions to work on: questions where I could actually tell when I was on the right track, questions where researchers cooperate more and fight less. So, I eventually decided to quit working on quantum gravity.

It was very painful to do this, since quantum gravity had been my holy grail for decades. After you've convinced yourself that some problem is the one you want to spend your life working on, it's hard to change your mind. But when I finally did, it was tremendously liberating."--John Baez: http://www.edge.org/q2008/q08_5.html

Yes--string theory and quantum gravity seem to be on their way out, after thirty years of absorbing hundreds of millions of dollars, with nothing to show for it, but snarky groupthink regimes fighting for their version of unreality, non-theories, and mythology.

Now I agree that it is good to fund science, such as the artificial retina I worked on for my dissertation: http://elliotmcgucken.com/dissertation.html (where the first treatment of MDT appeared in the appendix)

But too, we ought ask ourselves, how much NSF funding did Einstein recieve when he revolutionized physics with five papers in 1905, while working as a patent clerk? How mush NSF funding did the Wright Brothers receive for developing powered flight in their bicycle shop? If young physicists are generally the most creative, why should today's old physicists, who never really advanced physics, be given funding to hire sycophantic postdocs and professors, who must destroy and defund the indie physicists?

"A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it" --Max Planck

The problem unique to our times is that now MDT is facing not an aging regime of physicists with successful theories, but an aging regime of non-physicisists and their anti-theories.

Perhaps the overfunding of quantum gravity programs, and other non-theory, non-physics, social endeavors, has lead to snarky groupthink regimes which Lee Smolin characterizes in "How does one Fight Sociology?" in The Trouble With Physics.

For the past thirty years, hundreds of millions of dollars have gone into snarky theories which have basically banned asking, and thus answering, foundational questions. The funniest thing about the String-LQG wars is that they are all based on a questionable premise, as the great Freeman Dyson reminds us in THE SCIENTIST AS REBEL. On page 219 Freeman Dyson writes,

"(Brian) Greene takes it for granted, and here the great majority of physicists agree with him, that the division of physics into seperate theories for large and small objects is unacceptable. General relativity is based on the idea that space-time is a flexible structure pulled and pushed by material objects. Quantum mechanics is based on the idea that space-time is a rigid framework within which observations are made. Greene believes there is an urgent need to find a theory of quantum gravity that works for large and small objects alike. . . As a conservative, I do not agree that a division of physics into separate theories for large and small is unacceptable. I am happy with the situation in which we have lived for the last eighty years . . . The question I am asking is if there is conceivable way we could detect the existence of individual gravitons. I propose as an hypothesis that it is impossible in principle to observe the existence of individual gravitons." --Freeman Dyson, THE SCIENTIST AS REBEL, pp 219-220

One of the problems with all the String Theorists and LQGers is that they begin with the premise that, "ALL PROGRESS MUST GO THROUGH US. WE ARE THE WAY, THE PATH, THE TRUTH." They get a few hundred million dollars, hire a few thousand grad-students, and select the snarkiest to award with tenure-track positions, so as to serve the anti-theory regime, squash all indie physicists and natural curiosity, and shore up funding for non-physics. And hence progress in physics grinds to a halt.

MDT predicts all of relativity from a simple postulate and equation that also provides *physical* model for entropy, time, and all its arrows, quantum entanglement and nonlocality, and all the dualities--space/time, energy/mass, and wave/particle. Not bad for one small equation: dx4/dt = ic, which offers a *physical* unification across all realms of physics, tying together entities as diverse as quantum entanglement and the timelessness of the photon, while presenting insight into a novel physical facet of our universe--the fourth dimension is expanding relative to the three spatial dimensions.

Science is more of an art than a science, and it always seems to advance in manners never before anticipated by the establishment, as Planck stated. One cannot legislate, nor vote on, nor dictate the advancement of science by fiat. "One cannot pray a lie," as Mark Twain once said.

"New scientific ideas never spring from a communal body, however organized, but rather from the head of an individually inspired researcher who struggles with his problems in lonely thought and unites all his thought on one single point which is his whole world for the moment." --Max Planck

And again we see the primacy of the honest individual in the classic, epic hero's journey!

"A hero ventures forth from the world of common day into a region of supernatural wonder: fabulous forces are there encountered and a decisive victory is won: the hero comes back from this mysterious adventure with the power to bestow boons on his fellow man." --Joseph Campbell

http://en.wikipedia.org/wiki/Monomyth

And the Nobel Laureate eocnomist F.A. Hayek agrees!

"The tragedy of collectivist thought is that, while it starts out to make reason supreme, it ends by destroying reason because it misconceives the process on which the growth of reason depends. It may indeed be said that it is the paradox of all collectivist doctrine and its demands for "conscious" control or "conscious" planning that they necessarily lead to the demand that the mind of some individual should rule supreme--while only the individualist approach to social phenomena makes us recognize the superindividual forces which guide the growth of reason. Individualism is thus an attitude of humility before this social process and of tolerance to other opinions and is the exact opposite of that intellectual hubris which is at the root of the demand for comprehensive direction of social purpose." -F.A. Hayek, The End of Truth, The Road to Serfdom

Peter Woit blogs about the sycophancy in American Academia:

http://www.math.columbia.edu/~woit/wordpress/?p=894

But yet, I asked my own foundational questions, far beyond the sycophancy and anti-theory regimes--questions based on a *physical* reality all to many ignore, and I ended up unfreezing time and liberating us from the block universe.

Einstein's Relativity may be derived from dx4/dt= ic, which represents a more fundamental invariance of this universe--the fourth dimension is expanding relative to the three spatial dimensions. Einstein introduced relativity as a principle--as a law of nature not deduced from anything else, and well, I guess I was dumb enough to ask, 'why relativity?' And I found the answer in a more fundamental invariance--the fourth dimension is expanding relative to the three spatial dimensions, or dx4/dt = ic.

And not only can all of relativity be derived from this, but suddenly we are liberated from the block universe and time and progress in theoretical physics are unfrozen. And change is seen in a most fundamental equation that weaves change into the very fabric of space-time, where it needs to be, as change pervades every realm of physics and all acts of *physical* measurement. And suddenly we have a *physical* model for entropy, time and its arrows and assymetries in all realms, free will, and quantum mechanics' nonlocality, entanglement, and wave-particle duality. The fourth expanding dimension distributes locality, fathering time. MDT accounts for the constant speed of light c--both its independence of the source and its independence of the velocity of the observer, while establishing c as the fastest, slowest, and only velocity for all entities and objects moving through space-time, as well as the maximum velocity that anything is measured to move. And suddenly we see a physical basis for the dualities--for space/time, wave/matter, and energy/mass or E=mc^2. Energy and mass are the same thing--it's just that energy is mass caught upon the fourth expanding dimension, and thus it surfs along at "c."

Well, I would call all of this a massive unification--all based on a simple *physical* model and equation. I imagine this is just the tip of the iceberg of everything implied by this new physical model--this hitherto unsung feature of the universe--the fourth dimension is expanding relative to the three spatial dimensions: dx4/dt=ic.

And it all began with *why length contraction?" "Why relativity?" "Why nonlocality?" "Why entanglement?"

I know it is a crime to ask such foundational questions, another crime to answer them, and yet another crime to answer them with a simple postualte and equation, as simple postualtes and equations have benn banned by the anti-theory regimes, along with simple postualtes and equations represeting hitherto unsung *physical* realties have been outlawed, and the top grad students and postdocs are regularly sent forth to detroy them, while wearing masks, in the dark of night, for all sycophants must eventually transform into anonymous cowards,as the Nobel Laureate economist F.A. Hayek hints at in his two chapters "The End of Truth," and "Why The Worst Get on Top."

(It is also against the law, generally, to quote Nobel Laureates, as you shall see at the end of this post)

But, yet, the fourth dimension moves. "E pur si muove!" as Galileo atated. We have been liberated from frozen time and the block universe! Ergo I have free will, and I shall use it to both ask and answer foundational questions in physics via MDT's simple elgance and beauty.

Below are some of the questions that are answered with Moving Dimensions Theory's simple postulate and equation: "because the fourth dimension is expanding relative to the three spatial dimensions: dx4/dt = ic."

0. Why time? Why time's arrows and asymmetries?

0.1 Why relativity? Why the principle of relativity? What deeper physical reality underlies relativity?

0.2 Why entanglement and nonlocality?

1. Why is light's velocity a constant c? Why relativity's postulates?

2. Why is light's velocity c independent of its source?

3. Why is it that nothing can travel faster than c?

4. Why does a photon, which travels at c, not age?

5. Why does a photon's spherically-symmetric probablistic wavefront define simultaneity--a locality in the fourth dimension?

6. Why are energy and mass equivalent? Why E=mc^2?

7. Why do all of time's arrows point in the same direction--towards dissipation, decoherence, and entropy?

8. Why do so many physicists say time is the fourth dimension, when Einstein never said x4 is time, but instead said x4 = ict?

9. Why can matter can appear as energy or mass?

10. Why is it that when matter appears as pure energy, it propagates at c through space?

11. Why does all matter have particle--local--and wave--nonlocal--properties?

12. Why does all energy have particle--local--and wave--nonlocal--properties?

13. Why is it that when matter appears as stationary mass it propagates at c through the fourth dimension?

14. Why is it that when matter appears as energy, it propagates at c through the three spatial dimensions?

15. Why is it that to move at c through space is to stand still in the fourth dimension?

16. Why is it that to move at c through the fourth dimension is to stand still in space?

17. Why is it that all objects move at but one speed through space-time--c?

18. Why is the universe expanding?

19. Why does radiation expand outwards, but not inwards?

20. Why do we see retarded waves, but not advanced?

21. Why is it that entropy imitates the general motion of all radiation and the universe's expansion--a spherically-symmetric expanding wave?

22. Why is it that Huygens' Principle, which underlies all reality ranging from QED to Feynman's many-paths, to classical physics, state that every point of a spherically-expanding wavefront is in turn a spherically-expanding wavefront?

23. Why are all photons described by a spherically-expanding wavefront propagating at c?

24. Why is it that two initially-interacting photons remain entangled, no matter how far they travel apart?

25. Why is it that two initially-interacting photons remain the exact same age, no matter how far they travel apart?

26. Why is it that Young's double-slit experiments show that both mass and energy have nonlocal wave properties?

27. Why is it that the collapse of the wave function is immediate in the photoelectric effect, and all other experiments?

28. Why is there no way for an object to gain velocity without being reduced in length via relativistic length contraction?

29. Why does a photon trace out a null vector through space-time? How can movement across the universe describe a path of zero length?

30. Why does time's arrow point in a definitive direction?

21. Why does entropy increase?

32. Why do moving clocks run slow?

33. Why is time travel into the past impossible?

34. Why does free will exist?

35. Why is it that time is not frozen---how come the block universe does not exist? Why do we have free will?

36. Why does a photon's probabilistic wavefront travel at c?

37. Why is the velocity of quantum entanglement c? Why is it that only initially interacting particles can yet be entangled? Why is it that they must first share a common locality or origin, in order to share an entangled nonlocality when they are separated?

38. Why is it that in Schrodinger's equation, the first derivative with respect to the fourth dimension is proportional to the second derivative with the respect to the three spatial dimensions? Any change in position in the fourth expanding dimension is an acceleration in the three spatial dimensions.

39. Why is it that a photon emitted from the sun is red-shifted as it travels away? It's wavelength appears longer as it is measured against space that is less-stretched. A photon inherits the local geometry of the space-time where it was emitted.

40. Why do clocks in gravitational fields run slow?

41. Why are photons red-shifted as they move away from massive objects, and blue-shifted as they move towards them?

42. Why the conservation laws? Why does an object maintain its rotation in space-time, unless acted upon by an exterior force?

43. Why is the velocity of every object through space-time c?

44. Why is it that the only way to stay stationary in the fourth dimension is to move at c through the three spatial dimensions?

45. Why is it that the only way to remain stationary in the three spatial dimensions is to move at c relative to the fourth dimension?

46. Why does a photon have zero rest mass, and how does zero rest mass imply the velocity of light? None of the object's matter exists in the three spatial dimensions, but only in the fourth expanding dimension.

47. Why time's arrows?

48. Why time's asymmetries?

49. Why entropy?

50. Why is there an i in x4=ict?

51. Why is the velocity of light both independent of the velocity of the source and the velocity of the observer?

52. Why are light, time, and measurement so fundamentally related?

53. Why the - sign in-front of x4 in the space-time metric? What is different about x4?

Well, MDT answers all theses questions, and more, with a simple physical postulate and equation: "The fourth dimension is expanding relative to the three spatial dimensions or dx4/dt = ic."

Over the years, MDT has provided a *physical* model that answered these and other questions, unifying diverse fields and physical phenomena in a common, simple principle.

Now as MDT unfreezes both time and progress in theoretical physics, it will be opposed by many. Furthmore, as MDT explains away wormholes and time travel into the past, which have never been seen but yet form the foundations of many modern religions adhered to by geometric mystics and soothsayers, it will be opposed even more. As MDT provides a simple equation and postulate that hearken on back to the heroic age of physics, instead of presenting indecipherable math that can be used to raise massive funding for some groupthink Matrix/corporate-state/MTV show, it will be opposed even more, by those in The Matrix who have nothing to gain by simple truth and beauty, and so much to lose--their illusions of grandeur.

MDT's great uniter and unifier is a fundamental invariant of the universe that has hitherto been unsung--the fourth dimension is expanding relative to the three spatial dimensions, or dx4/dt = ic.

Too, too many postmodern theories suggest that we should get rid of time, free will, nonlocality, causality, change, and even space! Yes--too, too many modern theories suggest that we should get rid of *physics* and *physical reality*, so that we can keep funding bureuacracies! Too, too many postmodern physicists have long ago given up trying to explain entanglement, nonlocality, entropy, and time and all its arrows and assymetries with a *physical* model. Too, too many physicists have chosen to ignore Godel's problems with the block universe and time, while losing the sense of wonderment when considering action-at-distance, nonlocality, and the EPR Paradox.

"The most beautiful thing we can experience is the mysterious. It is the source of all true art and all science. He to whom this emotion is a stranger, who can no longer pause to wonder and stand rapt in awe, is as good as dead: his eyes are closed." --Albert Einstein

Yes--entanglement, entropy, time, nonlocality, Huygens' Principle, relativity--how mysterious are all these! And yet if you ask foundational questions such as *why* entanglement, *why* entropy, *why* time, *why* nonlocality, *why* Huygens' Principle, *why* relativity, the richest, wealthiest establishment in the history of physics, which also happens to be the establishment which has contributed the least (perhaps money cannot buy physics and philosophy?), sends forth anonymous postdocs and grad students to launch the snarky, ad-hominem attacks they perfect under the guidance of their pseudo-physicist political mentors.

Yes--the typical view held by contemporary physicists is that of the block universe. In fact, up until now and MDT, I think pretty much everyone who has embraced Einstein's relativity has embraced the block universe, which pretty much denies free will. How strange that physicists, who strive and work for Truth each day, have renounced free will! Perhaps that is why there has been so little progress in theoretical physics over the past thirty years. Everyone is just reasoning that it's all fate anyway, and time is frozen, so why try that hard? Why not just write coffeee-table physics books about wormholes/time travel into the past (even though without free will, how could we choose to build a time machine?). Why not just build vast empires out of postmodern math, and hire grad students and postdocs (who get a tiny portion of the funds) to laugh at/snark true theoretical physicists and their free will, logic, and reason?

The great thing about Moving Dimensions Theory is that it allows us to keep all of relativity while also granting us free will and liberating us from the block universe.

Wish I could buy everyone a beer to celebrate our newfound free will! Perhaps now they can no longer argue that string theory and loop quantum gravity are our fate for the next four thousand years, as they are pre-embedded in the future of our block universe.

And too, in addition to exploding the block universe myth and unfreezing time, MDT provides a *physical* model accounting for change, entropy, relativity, quantum mechanics' nonlocality and entanglement, and time and all its arrows and assymetries across all realms. Furthermore, Huygens' principle, which manifests itself in all realms from classical waves to Feynman's many-paths interpretations of quantum mechanics, is given a deeper foundation--a raison d'etre--a fundamental source--and this is the same fundamental source underlying relativity and quantum mechanics' nonlocality and thus QM's probabilistic nature, as the fourth expanding dimension distributes locality.

Behold MDT--the great unifier and invariant source underlying all these *physical* phenomena--in relativity and quantum emchanics--in statistical mechanics and entropy.

For the first time in the history of relativity, *change* has been *physically* woven into the fundamental fabric of spacetime, with dx4/dt = ic. And that's where change needs to be! For can you name any branch of physics in which change, and time, do not exist? Without change, no measurement can be made.

MDT is unique in that it offers a *physical* model underlying entropy, entanglement, and nonlocality, and too, all of relativity can be immediately derived from its simple postulate and equation.

I expect MDT to bring additional boons for years to come!

It is certainly a greater theroy, with far more ranging consequences, than String Theory and LQG.

The first page of String Theory in a Nutshell states in a footnoted sentence:

THE CASE FOR STRING THEORY:

String Theory has been the leading candidate over the past two decades for a theory that consistently unifies all the fundamental forces of nature, including gravity. It gained popularity because it provides a theory that is UV finite.(1)

The footnote (1) reads: "Although there is no rigorous proff to all orders that the theory is UV finite, there are several all-orders arguments as well as rigorous results at low-loop-order. In closed string theory, amplitudes must be carefully defined via analytic continuation, standard in S-matrix theory. When open strings are present, there are diveregences. However, they are interpreted as IR divergences (due to the exchange of massless tsates) in the dual closed string channel. They are subtracted in the "Wilsonian" S-matrix elements."

So you see, String Theory is not a finite theory, but this is generally kept to the footnotes, when mentioned at all.

A lot of Nobel Laureates have problems with String Theory:

""WE DON'T know what we are talking about." That was Nobel laureate David Gross at the 23rd Solvay Conference in Physics in Brussels, Belgium, during his concluding remarks on Saturday. He was referring to string theory. . ." --http://www.newscientist.com/channel/fundamentals/mg18825293.700

It is anomalous to replace the four-dimensional continuum by a five-dimensional one and then subsequently to tie up artificially one of those five dimensions in order to account for the fact that it does not manifest itself." -Einstein to Paul Ehrenfest

String theorists don't make predictions, they make excuses. -Richard Feynman, Noble Laureate

String theory is like a 50 year old woman wearing too much lipstick. -Robert Laughlin, Nobel Laureate

Actually, I would not even be prepared to call string theory a "theory" rather a "model" or not even that: just a hunch. After all, a theory should come together with instructions on how to deal with it to identify the things one wishes to describe, in our case the elementary particles, and one should, at least in principle, be able to formulate the rules for calculating the properties of these particles, and how to make new predictions for them. Imagine that I give you a chair, while explaining that the legs are still missing, and that the seat, back and armrest will perhaps be delivered soon; whatever I did give you, can I still call it a chair? -Gerard `t Hooft, Nobel Laureate in String Theory

"It is tragic, but now, we have the string theorists, thousands of them, that also dream of explaining all the features of nature. They just celebrated the 20th anniversary of superstring theory. So when one person spends 30 years, it's a waste, but when thousands waste 20 years in modern day, they celebrate with champagne. I find that curious." -Sheldon Glashow, Nobel Laureate

"I don't like that they're not calculating anything. I don't like that they don't check their ideas. I don't like that for anything that disagrees with a n experiment, they cook up an explanation-a fix-up to say, "Well, it might be true." For example, the theory requires ten dimensions. Well, maybe there's a way of wrapping up six of the dimensions. Yes, that's all possible mathematically, but why not seven? When they write their equation, the equation should decide how many of these things get wrapped up, not the desire to agree with experiment. In other words, there's no reason whatsoever in superstring theory that it isn't eight out of the ten dimensions that get wrapped up and that the result is only two dimensions, which would be completely in disagreement with experience. So the fact that it might disagree with experience is very tenuous, it doesn't produce anything; it has to be excused most of the time. It doesn't look right." -Richard Feynman, Nobel Laureate in Physics

"But superstring physicists have not yet shown that theory really works. They cannot demonstrate that the standard theory is a logical outcome of string theory. They cannot even be sure that their formalism includes a description of such things as protons and electrons. And they have not yet made even one teeny-tiny experimental prediction. Worst of all, superstring theory does not follow as a logical consequence of some appealing set of hypotheses about nature. Why, you may ask, do the string theorists insist space is none-dimensional? Simply because string theory doesn't make sense in any other kind of space." --Sheldon Glashow, Nobel Laureate in Physics

Even String Theory's founder, Michio Kaku, has problems with the theory: "The great irony of string theory, however, is that the theory itself is not unified. To someone learning the theory for the first time, it is often a frustrating collection of folklore, rules of thumb, and intuition. (IN OTHER WORDS IT IS NOT PHYSICS!!!) At times, there seems to be no rhyme or reason for many of the conventions of the model. For a theory that makes the claim of providing a unifying framework for all physical laws, it is the supreme irony that the theory itself appears so disunited!!"

Chapter 1. Path Integrals and Point Particles: Why Strings?

" --"Introduction to Superstrings and M-Theory," page 5. -Michio Kaku

"If Einstein were alive today, he would be horrified at this state of affairs. He would upbraid the profession for allowing this mess to develop and fly into a blind rage over the transformation of his beautiful creations into ideologies and the resulting proliferation of logical inconsistencies. Einstein was an artist and a scholar but above all he was a revolutionary. His approach to physics might be summarized as hypothesizing minimally. Never arguing with experiment, demanding total logical consistency, and mistrusting unsubstantiated beliefs. The unsubstantial belief of his day was ether, or more precisely the naïve version of ether that preceded relativity. The unsubstantiated belief of our day is relativity itself. It would be perfectly in character for him to reexamine the facts, toss them over in his mind, and conclude that his beloved principle of relativity was not fundamental at all but emergent-a collective property of the matter constituting space-time that becomes increasingly exact at long length scales but fails at short ones. This is a different idea from his original one but something fully compatible with it logically, and even more exciting and potentially important. It would mean that the fabric of space-time was not simply the stage on which life played out but an organizational phenomenon, and that there might be something beyond." -A Different Universe, Reinventing Physics From The Bottom Down, Robert B. Laughlin, Winner of the Nobel Prize in physics for his work on the fractional quantum Hall effect.

"[String Theory] has no practical utility, however, other than to sustain the myth of the ultimate theory. There is no experimental evidence for the existence of strings in nature, nor does the special mathematics of string theory enable known experimental behavior to be calculated or predicted more easily. Moreover, the complex spectroscopic properties of space accessible with today's mighty accelerators are accountable in only as "low-energy phenomenology"-a pejorative term for transcendent emergent properties of matter impossible to calculate from first principles. String theory is, in fact, a textbook case of Deceitful Turkey, a beautiful set of ideas that will always remain just barely out of reach. Far from a wonderful technological hope for a greater tomorrow, it is instead the tragic consequence of an obsolete belief system-in which emergence plays no role and dark law does not exist."

-A Different Universe, Reinventing Physics From The Bottom Down, Robert B. Laughlin, Winner of the Nobel Prize in physics for his work on the fractional quantum Hall effect.

MDT delivers an ultimate theory, whereas Loop Quantum Gravity and Sring Theory only sustain a myth of an ultimate theory. And thus we are commanded from on high--from the pinnacles of the ani-theory regimes--to ignore MDT and Nobel Laureates such as Robert Laughlin, F.A. Hayek, Feynman, Einstein, Planck, and others I quote above. Welcome to the dark ages.

I apologize for the length of this post, but I am working on a book: HERO'S JOURNEY PHYSICS: FROM BRUNO, TO GALILEO, TO EINSTEIN--AND YET IT MOVES!

Best,

Dr. E (The Real McCoy)

Dr E.

Thanks for your further comments. First off I want to make it clear that I am not going to be drawn into a discussion of your essay in this thread. People who read here will be looking for discussions about my essay and I dont want them to have to wade through stuff which belongs in your area. I am happy to discuss any points of cross-over between my approach and that in other essays but I have already said that I find your approach very different from mine ad there is little in common to discuss here.

On the merits of sring theory, you quote a number of Nobel prize winners who have spoken out against it. Much as I respect the work of these great physicists, I do not regard them or anyone else as authority figures. In science all arguments stand on their own merits irrespective of who says them.

You also quote Gross who is one of the leading lights in the string theory world, and Kaku who was involved in string theory earlier on. The point they were making is one that is famiiar to all string theorists, i.e. that the fundamentals of the theory are not understood.

One of the problems with the string theory culture is that many people look for the papers written by its leading lights and then build on their work. At this year's string conference Gross was begging people to look elsewhere for new ideas, or for old ideas that can be reexamined. I think he has a very good point. The younger generations are the best at having original ideas so they need to look more to themselves for inspiration.

You mention that Peter Woit has talked about the sycophancy in American Acedemia. He may be right. I dont have much direct experience of American Academia but I have seen a similar thing when working for large American companies. The point is consistent with what Gross is saying. People need to make their own judgements rather than following the work of others. If the American system does not encourage it, the same is not true in all other countries. John Baez seems to have escaped all that by shifting to work on n-category theory which is much more open and international. He is a very smart guy. But there are people in the n-category world who are applying their ideas to string theory and opening up some very new and interesting perspectives.

My essay is about using symmetry to try to understand the foundations of quantum gravity abnd string theory in particular. The fact that I am not am not any kind of authority figure in physics means that people will be slow to listen, but in the end the idea will live or die on its scientific merits alone. If others are not ready to take up the idea then I need to do more work on it myself to build up the case. I think this point is equally relevant to all the "independent reaserchers" out there.

Dear Philip,

necklase algebras were a new acquitance to me. Thank you for mentioning them. Maybe they are also relevant for TGD.

The symplectic fusion algebras of symlectic QFT, whose structure constants I managed to guess just few days ago, are braided commutative and associative and form a structure known as disk operad in category circles.

These algebras are built from elementary buildong block algebras of arbitrary dimension by replacing one or more elements of algebra by this kind of algebra: this corresponds to an improvement of measurement resolution by replacing a point in a collection of point associated with braid with N points in a little disk around it. Thus these algebras correspond to a collection of trees with each node having arbitrary number of branches and form therefore a fractal.

Quite generally, the notion of operad seems to code for the notion of measurement resolution and what is to improve it.

Best Regards,

Matti

Hi Matti,

Yes the necklace algebras are less well known. Likewise I am unfamiliar with some of the stuff you use like the Von Neumann algebras. I will have to look at those.

Phil

I enjoyed your paper; I have also suspected graph theory might play an important part in physics because it is axiomatic, mathematically rich, and embodies symmetry. I liked seeing the connections from random graphs to random matrices and then tying it all into quantum physics.

Brian Hi and ks for your comment.

I agree with what you say about random graphs and matrices. My own interest in both stems from my doctorate work on Lattice Gauge Theories (1985). I remember a lattice conference where some people were reporting on using random triangulations for quantum gravity. I recall thinking tha if I was working on that I would drop the triangles and just look at random graphs.

I did a short postdoc at Edinburgh where the physics dept was also looking a lot at neural networks. I did some random graph computations on their computer arrays while I was there. After I left I bought a small computer and continued to try to get spacetime to emerge from random graphs, but I soon realised that it would require a complicated form for the action and my computer would not be powerful enough.

In my work on lattice QCDs I had been working with matrices for the quark fields so the move from random graphs to random matices was an obvious one to take. I was out of touch with the literature so I did not know that other people were looking at random matrix models until later when the WWW arrived.

I think that people who worked on field theory from continuous models have been slower to take up these ideas, but it is happening slowly. Of course mathematicians have been studying both random graphs and random matrices for much longer but their research is not directed so much at physics.

Matti made this very good point:

"I think that your idea about permutations has something in it. My main criticism is that the reduction of everything to combinatorics leads to a loss of diffeo-structures and even the notion of topology.For instance, the notion of mass requires not only continuity but also diffeo-structures and isometries if one believes that Poincare invariance is behind classical conservation laws. Of course, these symmetries can be seen as a special case of permutation symmetries but...!

Personally I believe that discretization -rather than discreteness- is fundamental as a geometric correlate for the finite resolution of quantum measurement and also cognition. If so, the replacement of space-time regions with sets of discrete points would become a key element in the construction of quantum states which could be seen as their own descriptions carry information about finite measurement resolution in self-referential manner. Physical states would be their own approximations!"

I did not say much in my essay about the discretness vs continuous nature of space and time but as Matti recognised it is a relevant issue so I'll add a few bullet point about it here. Matti will be familiar with much of this but I am sure there are others who ask themselves these questions so I wont assume too much.

- Discrete and continuous are not mutualy exclusive in quantum theory. We have learnt to live with wave particle duality and we understand it in terms of different bases of states in the quantum field theory. When we quantise gravity we can expect a similar result for spacetime itself. It will be both continuous and discrete.

- because of this duality it is not always clear what discreteness means. One message that is clear from different approaches to quantum gravity is that the amount of information in a volume of space is finite and bounded. Without this rule we cannot make sense of black hole thermodynamics for example. In classical field theories including general relativity and also in standard quantum field theory there is effectiviely no limit to the amount og information needed to describe the state of the fields inside a fixed volume. This is because space and time are fundemaentally contuous in these theories and there is no ultraviolet cutoff that limits the small wavelength high frequency modes that can stuff unlimited inforamtion into a small space. This should not be what happens in quantum gravity.

- another indication of soem kind of discreteness in quantum gravity is the generalised uncertainty principle that has been derived in various ways from different models of quantum gravity and also from general arguments about quantum gravity. It tells us that there is a limit to how small we can measure quantities of distance and time. The limit is reached at the Planck scale or possibly larger. This generalises the heisenberg uncertainty principle that tells us that there is a limit on how well we can know position and velocity at the same time. The generalised principle says there is even a limit to both individually. This principle does not mean that spacetime has to be a discrete structure but it means that something like discretness muts limit our ability to measure small distances and times.

- A continuous spacetime has a fixed topology but theories such as string theory and LQG suggest that spacetime tpology is not fixed. In a path integral approach to quantum gravity we would expect to have to sum over all possible topologies. I think this will be reflected in dual descriptions of spacetime - on the one hand you will have a sum over all topologies and on the other you will have a discrete description with no fixed topology.

- In the essay I choose to motivate evet-symmetry by starting from quantum field theory and removing spacetime to leave just Feynman diagrams. Since the diagrams in QFT are graphs with discrete nodes this leads to a discrete description of spacetime. In string theory the feynman diagrams become worldsheets. When you look at them on small scales there are no discrete branching points. Everything is smooth and continuous yet you can still throw away spacetime and go through the same argument. The discreteness of the events is lost and it is just the topology of the worldsheet and its internal mechanics that matters.

- When I define my necklace algebras I treat strings as structures made of discrete partons with fermionic statistics, but this is not the end of the story. Similar necklace lie algebras have been successfully deformed to Hpof algebras and I expect the same tobe possible with mine. This is because when particles are confined to one or two dimensions (as on a string or worldsheet) they can be given fractional or anyonic statistics. In this way the string partons can be split and spread contuously along the string. It will only be the total statistics of the string partons which must add up to an integer of half integer quantity.

- Event-symmetry is all about permutations of spacetime events, but when I am asked to state the principle of event symmetry I say something like this. "Physics should be invariant under a group that includes a permutation group acting on spacetime events either as a subgroup or as a homomorphism." This allows for me to generalise the permutation group e.g. to matrix groups which are less discrete. Because I allow for homomorphisms I can also accept braid groups which have homomorphisms onto the symmetric groups (of permutations). This is then just one step away from quantum groups. Of course I then also allow for algebraic generalisations of the group concept. Probably there is a more abstract way I could state the principle in terms of category theory that would include very general algebraic strcutures related to permutations but I am more interested in specifics than abstract generalisations. The point is that these generalisations allow s to go beyond the hard discreteness of the permutation group into realms where we have something more like a non-commutative geometry.

- event-symmetry is not a theory of quantum gravity. It is just a tentative symmetry principle analogous to the equivalence principle that can be used as a guide to forming theories of quantum gravity. In the case of string theory I am trying to use it as a way to understand the fundamentals of string theory as an existing theory of quantum gravity. In this context it does not change string theory to replace it with something discrete of which string theory is a continuous approximation. The discreteness is in fact already in string theory and is most easy to see in the matrix theory formulations. With event-symmetry I am looking to make those discrete formulations more complete so that the differnt dual formulisms of string theory can be unified.

Dear author and other commentators belonging to Theoretical Physics! i am a bit of an outcast experimentalist in this wonderful discussion on the 'Nature of Time'. There is life because there is time. Thus, creation, living and destruction by way of death are all facts of human life as well as other Creations in this physical Universe of ours! It is hard to discard the concept of TIME, as also the space that provides motions to take place, as positions change with time. Now, we are all discussing the nature of time itself. There is an interesting analog of time with energy in the Uncertainty relations, being conjugate quantities. If there is no time, energy becomes infinite. In fact, to explain the decay of an alpha structure inside an unstable nucleus, one can illustrate the overcoming of the coulomb potential barrier coming from the uncertainty corresponding to the frequency with which the alpha particle hits the unstable nucleus boundary region. Motion is an observed fact that involves both energy and time. Without the two, we can't discuss any motion. Further, the time has to be linear/continuous, if sanctity of any measurement is to be maintained. The discreteness is also allowed within the domain of Uncertainty relations. Thus far, everything is fine.

May i request the wise theoretician friends to enlighten me with the questions about the nature of time that seem to defy proper understanding. i am sure there are some that we all are supposed to discuss to clarify some facts about time that we don't understand in any scientific phenomenon.

Sorry if i appear to be naive and foolish in raising the issue in a simpleton manner.

Neranda Nath

Thank you for your comment. You are asking for a list of questions about time that theoretical physicists think need answering. I can't answer on behalf of all theoretical physicists, but I will give you my list ordered with the ones that I think are more metaphysical towards the end. Many physicists avoid metaphysical questions so they would avoid the latter ones (unless they don't agree that they are metaphysical). Otherwise I think this would be a good representation of the questions others would come up with.

If anyone wants to give long answers to any of these in specific relation to their own ideas or essays then I strongly suggest that they do so in their own essay forums because I think that makes it clearer for anyone wanting to read the threads.

So here are the questions...

How should we use time in quantum gravity?

What happens to time at a spacetime singularity?

Why is there (apparently) just one dimension of time, and three of space?

Is there a minimum unit of time?

What is the explanation for time's arrow in thermodynamics, and could it reverse?

What is the role of time in cosmology beyond the scales of the observable universe?

Is time continuous, discrete, both, neither or what?

Is temporal causality fundamental?

Is the observer and measurement in quantum theory relevant to any of the above?

What is the relationship of conciousness and free will to the nature of time?

I have covered most of these questions in my essay except the last two. They are interesting questions but I dont regard them as relevant to the issues I was looking at. Besides I dont have very complete answers for them. Many of the other essays have explored the topics like conciousness and free will which is fine. These are all valid foundational questions

I wont expand much on my answers but I'll say a little bit more about where my viewpoint comes from. My undergradaute courses in theoretical physics at cambridge had particularly good coverage of general relativity because of the interests of researchers there, but when I did my doctorate I concentrated on Lattice Guage Theories which is a much more mundane calculational approach to the string nuclear force. Some of the things I learnt from doing LGT has stringly influenced the way I now approach quantum gravity because I combine what I learnt with the principles of relativity. I already mentioned how it piqued my interest in random graph and random matrix models but there is something else even more fundamental.

I did calculations in LGT on 4 dimensional lattices which represented small bits of spacetime. The aim was to extract values for quantities in particle physics that depend on the string force such as the mass spectrum of hadrons.

The interesting thing about this was that we did not treat the time dimension as special. There is a well known trick called Wick rotation that allows you to make the time dimension the same as the space dimensions, so there is nothing like time eveolution left in the calculation. Yet you can still extract hadron masses and other quantities as if all the dynamical physics is there. It made me realise that the distinct nature of time is not as fundamental as you might think.

There was another trick we used if we wanted to see what happened at high temperatures. You can vary the size of tne time dimension on the lattice with anti-periodic boundary conditions to control the effects of temperature. As you change the size of the lattice you get phase trnasitions in the quark-gluon matter. When I was doing this we were predicting the temperature and density at which the trnasition happened and since then it has been measured in colliders.

Physical studies like this make the nature of time seem very different from our everyday experience and open the mind to new ideas. I think this is why theoretical physicists sometimes look at different fundamental questions on the nature of time than other scientists. Our ideas may seem wild at times but they are motivated by real physics and principles that we have observed in nature.

Dear Philip,

Thanks for the response listing questions that need the answer about the nature of time so far as Physics/cosmology is concerned. Let me list some of my doubts about the nature of time below:-

1. As time unit has been defined in Physics on the basis of territorial confinement in the solar system. Can it hold true on the cosmic scale!

2. Uncertainty relation of time/energy indicates that if time uncertainty is zero, energy becomes infinity. Won't it indicate the birth of the universe with such a scale of energy?

3.Space/time are concepts introduced by us but Gravity is a fact of nature independent of such concepts.

4. The concept of Quantum gravity has come about on account of the behavior of black holes in cosmology. Are there other processes that require quantum nature for gravity! Basically, the gravity is a macroscopic quantity with no significance for the microworld of atoms/nuclei/particles. As the latter provided the indication for quantum physics, how come gravity, in the absence of the discovery of 'graviton', can be justified.

5. i don't understand how the LGT theory, based on space/time coordinates, becomes relevantly applicable to quantum /gravitational aspects?

6. Time and temperature in thermodynamics appear to be parallel in nature. Can one of these represent the whole search for truth in physics? Inversion/reversal get ensured on symmetry considerations for both these parameters.

i am not sure if all the above points are relevant for you to consider under your essay. However, the theme of the essay may allow consideration of the above points! NN

1. As time unit has been defined in Physics on the basis of territorial confinement in the solar system. Can it hold true on the cosmic scale!

Yes, physics works surprisingly well at cosmic scales. For example the observations of stella spectra from distant galaxies shows just how universal chemistry is.

2. Uncertainty relation of time/energy indicates that if time uncertainty is zero, energy becomes infinity. Won't it indicate the birth of the universe with such a scale of energy?

This sounds like the Turok-Hawking model where the universe starts as a vacuum quantum fluctuation. in nay case the generalised uncertainty principle from quuantum gravity says that the minumum precision for a measurement of time is the Planck length, which implies an uncertainty eceeding the planck energy. The Planck unit of energy is the about the amount of energy needed to run a 60W light bulb for a year

3.Space/time are concepts introduced by us but Gravity is a fact of nature independent of such concepts.

space and time are just as real or unreal as gravity. The question is at what point do they emerge from more fundamental concepts and how?

4. The concept of Quantum gravity has come about on account of the behavior of black holes in cosmology. Are there other processes that require quantum nature for gravity! Basically, the gravity is a macroscopic quantity with no significance for the microworld of atoms/nuclei/particles. As the latter provided the indication for quantum physics, how come gravity, in the absence of the discovery of 'graviton', can be justified.

The effects of quantum gravity are too small on anything we have been able to observe. We may be lucky enough to find some phenomena where QG is significant, but even IF we dont the serach for a single consistent thoey of quantum gravity is not without hope or merit.

5. i don't understand how the LGT theory, based on space/time coordinates, becomes relevantly applicable to quantum /gravitational aspects?

My point was just that ideas from other areas can be applied in different situations. Think about how your own background and experiences may have affected your own thinking on fundamental concepts and you should get my point.

6. Time and temperature in thermodynamics appear to be parallel in nature. Can one of these represent the whole search for truth in physics? Inversion/reversal get ensured on symmetry considerations for both these parameters.

Dualities of similar sorts have proven very useful in physics. When you understand one model as being dual to another you can often use the duality to learn lots of things about each model by looking at its dual.

dear Philip,

the above anonymous post appears to be from you.Thanks for the same. I agree with the clarifications pointed out. best wishes for your essay, with the request that my essay may also succeed in soliciting some critical comments from you!

There are several perspectives about the Mysteries of the Universe i dared to introduce, e.g., possible constituents of the primordial matter, dark matter and the presumption that the field strengths of unified as well as four manifested components change with time, more so in the early universe of 1/2 billion years!