Against Spacetime by Giovanni Amelino-Camelia

It is simpler to admit the non-existence of a quantum gravity theory rather than admitting the non-existence of a spacetime....

It is simpler still to admit the wackyness of the foundations of quantum theory itself rather than going after spacetime, especially since GR has been experimentally better confirmed (by several orders of magnitude) than the crown jewel of quantum theory (namely QED).

Nevertheless, Good luck, Giovanni, for the essay competition.

Joy

The simplest thing is to admit that the speed of light does depend on the speed of the light source - the "recourse to contracting lengths, local time, or Lorentz transformations" was a costly mistake:

http://www.amazon.com/Relativity-Its-Roots-Banesh-Hoffmann/dp/0486406768

Relativity and Its Roots, Banesh Hoffmann: "Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether."

Pentcho Valev pvalev@yahoo.com

Giovanni

Simpler than the winner of the last 3 world simpleton championships (in the famous words of Blackadder) "observers in relative motion do not share the same time." Precisely as you propose. (Pentcho this is the subtle point you missed). If what is termed a 'space time event' can grow and shrink on transformation, (change of kinetic state) then so must the length between peaks of a wave.

I loved your incisive essay Giovanni. I too considered "detection at a given detector" and analyse it's massive (lol) consequences. I can't agree all agree with the clear truth of your suggestion; "...over the last century we gradually came to appreciate that there would be no spacetime without particles."

I've been working on a re-interpretation of 'spacetime' with others including John Minkowski, which wirks well, and we believe the simplest of simpletons could comprehend if only they could drop the assumptions around the earlier interpretations. You beautifully show these assumptions as questionable and point in the same direction.

I hope you may be able to read and comment on my essay (beneath the kinetic theatre).

Congratulations on a fine and important essay.

Peter

Ciao Giovanni,

It is good to know your kids are making you keep your priorities straight.

Well, I agree with you that "the most serious difficulties are at the interface between quantum theory and relativistic spacetime inferences", but the question of the century is: What must give?

You are right, of course, to "go after all opportunities of finding new insight experimentally without imposing much prejudice on which avenues look more promising." The latter would be like looking for the keys where light is, not where they are lost.

All the best,

Joy

The problem is straightforward, Giovanni. You seem to reject the consequent (spacetime) but then refuse to question the truth of the antecedent (Einstein's 1905 postulates). Such a behaviour is incorrect when the theory is DEDUCTIVE.

Best regards, Pentcho

I totally agree with Joy Christian

And I totally agree with your cool name!

Giovanni,

You did question the truth of Einstein's 1905 postulates in the past:

http://discovermagazine.com/2008/mar/13-e-nste-n

"Six iconoclasts who could revolutionize physics - again. (...) 4. Giovanni Amelino-Camelia: 42, University of Rome-Sapienza, Italy. Body of work: His "doubly special relativity" posits that the supposedly constant speed of light actually depends on its wavelength and that space has a minimum distance. His theory could unify physics and help explain the early growth of the universe, but experimental proof seems to be a tall order. Einsteinian trait: Rejects accepted physics on the basis of logic arguments."

Why are you so timid now?

Pentcho Valev pvalev@yahoo.com

Hi Giovanni:

I thoroughly enjoyed your well-written paper and fully agree with your conclusion - " .....in some of the contexts where quantum mechanics is most significant, such as quantum tunneling through a barrier, the spacetime abstraction proves to be cumbersome. And I argue that in quantum-gravity research we might limit our opportunities for discovery if we insist on the availability of a spacetime picture."

Not only the above conclusions are vindicated in my paper - -" From Absurd to Elegant Universe", but also it is shown (figure 1) that since spacetime dilates at quantum particles' speeds (V close to C), observing or limiting quantum phenomena to fixed or classical spacetime departs from physical realty leading to the well-known inconsistencies and QM paradoxes. My paper proposes a new model for the missing physics of spontaneous decay that explains the inner workings of QM and demystifies the quantum observations resolving many of its paradoxes and inconsistencies with relativity theory. As you point out, this has never been done, and hence, the QM mysteries and misinterpretations continue to prevail.

The model predicts the observed expansion of the universe and galaxies and other data. The model provides answers to key fundamental questions and resolves paradoxes among general relativity, quantum mechanics, and cosmology. The impact of the new understanding on widely-accepted fundamental assumptions is discussed and a new wholesome perspective on reality is provided.

I would greatly appreciate your comments on my paper.

Best Regards

Avtar Singh

Hi Giovanni

I read your interesting and thought-provoking essay. I have some comments and doubts about some issues that I would be grateful if you could make some comments. You mention that:

But in some sense we never actually "see" spacetime, we never "detect spacetime", and over the last century we gradually came to appreciate that there would be no spacetime without particles.

You argue against space-time, but it was not clear to me what new conceptual framework or formulation you propose to replace space-time. For instance, in thermodynamics time is not an indispensable item for the calculation of the physical quantities, by only knowing the pressure, the temperature and the volume one can predict the outcome of a system no matter how much time elapses. To be honest, I did not get well why you see space-time redundant, the arguments you lay down appear to me somewhat messy, in what sense you think they are redundant?

On the other hand, I have been studying the problems of the measurement of the one-way speed of light and of clock synchronization and one of your statements call my attention particularly this: "Alice and Bob establish that they are in relative rest at a distance L with synchronized clocks."

According to my research the one-way speed of light has been never measured and clock synchronization a la Einstein assumes that the one-speed of light is isotropic which turns out to be redundant and thus a dead end. I have realized that clock synchronization has become a non-trivial task as at first sight it may seem.

Moreover, you mentioned in relation to the aether that:

I shall leave these questions to the appetites of philosophers... And then quote Poincaré:...Whether the ether exists or not matters little - let us leave that to the metaphysicians... Later you argue that the concept was rule out from physics because it turned out to be useless.

However, in my essay I hold the opposite opinion that reviving the aether it is more useful to solve most of the present problems of physics. Bell, Dirac and others contented that the situation of the aether in 1905-1915 was quite different from the situation of the aether in the middle of the XX century. This seems to me very plausible and I discuss in my essay some of the misconceptions around this concept. I claim that certain assumptions should be revived in physics because of their usefulness. One case of this was the notion of light as a particle brought back to life by Einstein. I would like to quote what Newton thought about the aether and its connection with gravity (Vesselin Petkov also holds that gravity is not a force and thus quantization of gravity is chimera), which I think it could be of great relevance to physics:

"Gravity is the result of a condensation causing a flow of ether with a corresponding thinning of the ether density associated with the increased velocity of flow..."

To make even clearer that Newton was actually Cartesian in the philosophical matters of gravity, in a letter to Bentley in 1692 Newton wrote:

"It is inconceivable that inanimate brute matter should, without the mediation of something else which is not material, operate upon and affect other matter, without mutual contact, as it must do if gravitation in the sense of Epicurus be essential and inherent in it. And this is one reason why I desired you would not ascribe 'innate gravity' to me. That gravity should be innate, inherent, and essential to matter, so that one body may act upon another at a distance, through a vacuum, without the mediation of anything else, by and through which their action and force may be conveyed from one to another, is to me so great an ABSURDITY, that I believe no man who has in philosophical matters a competent faculty of thinking can ever fall into it."

Making the assumption that the quantum vacuum is some sort of fluid (as the CERN experiments have revealed) it has been shown that the bending of light due to the presence of a massive object can be equivalently explained by a gradient in the refractive index of the vacuum.

Finally you mention that:

But how should one describe the position of the particle when it is formally "inside" the barrier? And especially how much time does it take a particle to quantum-tunnel through a barrier?

Besides reconsidering the aether in physics one should get rid of the notion of particle. Instead, I propose to use solitons which, as it is well known in several field of mathematics and physics, behave as particles in all aspects. The essay of Jarek Duda explains all the similitudes and at the same time the advantages of dealing with solitions in physics instead of particles. If one incorporates these two ingredients into physics the wave-particle duality disappears and experiments such as the double-slit experiment become quite intuitive and easy to handle.

I wish you good luck in the contest and I would be grateful if you could leave me some comments about my essay.

Israel

Dear Giovanni,

You are "more than willing to question the truth of Einstein's 1905 postulates" and at the same time your understanding is that "truth" is of interest for professions different from yours? Sounds contradictory. I think "truth" is quite relevant to your profession. Of the two statements:

A. The speed of light varies with the speed of the light source.

B. The speed of light is independent of the speed of the light source.

one is ABSOLUTELY true, the other is false. Unfortunately the false one was chosen as a fundamental postulate in 1905 - its "protective belt" had already been built:

http://bertie.ccsu.edu/naturesci/PhilSci/Lakatos.html

"Lakatos distinguished between two parts of a scientific theory: its "hard core" which contains its basic assumptions (or axioms, when set out formally and explicitly), and its "protective belt", a surrounding defensive set of "ad hoc" (produced for the occasion) hypotheses. (...) In Lakatos' model, we have to explicitly take into account the "ad hoc hypotheses" which serve as the protective belt. The protective belt serves to deflect "refuting" propositions from the core assumptions..."

The protective belt ("contracting lengths, local time, or Lorentz transformations") referred to by Banesh Hoffmann:

http://www.amazon.com/Relativity-Its-Roots-Banesh-Hoffmann/dp/0486406768

"Relativity and Its Roots" By Banesh Hoffmann: "Moreover, if light consists of particles, as Einstein had suggested in his paper submitted just thirteen weeks before this one, the second principle seems absurd: A stone thrown from a speeding train can do far more damage than one thrown from a train at rest; the speed of the particle is not independent of the motion of the object emitting it. And if we take light to consist of particles and assume that these particles obey Newton's laws, they will conform to Newtonian relativity and thus automatically account for the null result of the Michelson-Morley experiment without recourse to contracting lengths, local time, or Lorentz transformations. Yet, as we have seen, Einstein resisted the temptation to account for the null result in terms of particles of light and simple, familiar Newtonian ideas, and introduced as his second postulate something that was more or less obvious when thought of in terms of waves in an ether."

Pentcho Valev pvalev@yahoo.com

Hi Giovanni

Thanks you for your reply and your comments. I think I will read again your essay to grasp the detail. Anyway, I hope you get a chance to leave some comments in my entry.

Good luck in the contest

Best regards

Israel

Giovanni,

I liked your essay, for it makes a point similar to mine in a simple fashion. Your equation for the translation of the Alice coordinate to Bob

x(3)^μ_B = x(3)^μ_A b^ν{p(3)_ν()p(4)_ν, x(3)^μ}

is such that the last term looks very similar to a Yangian commutator. A Yangian is a quantum deformation of a universal enveloping operator. In fact I am working on precisely a formula of this type. This is equivalent to the Yang-Baxter relationship so that spacetime relationships have a quantum group structure.

I did not discuss Yangians in my essay, though they are a part of this overall work. I instead focused on the BCFW recursion relationship. The implication is that locality is an approximation. In the Yangian system there is aduality, where one set of variables given a spacetime relationship or configuration variables is dual to another set which have no explicit reference to spacetime.

Cheers LC