Physicists offer foundation for uprooting a hallowed principle of physics
January 5th, 2009Physicists at Indiana University have developed a promising new way to identify a possible abnormality in a fundamental building block of Einstein's theory of relativity known as "Lorentz invariance." If confirmed, the abnormality would disprove the basic tenet that the laws of physics remain the same for any two objects traveling at a constant speed or rotated relative to one another.
IU distinguished physics professor Alan Kostelecky and graduate student Jay Tasson take on the long-held notion of the exact symmetry promulgated in Einstein's 1905 theory and show in a paper to be published in the Jan. 9 issue of Physical Review Letters that there may be unexpected violations of Lorentz invariance that can be detected in specialized experiments.
"It is surprising and delightful that comparatively large relativity violations could still be awaiting discovery despite a century of precision testing," said Kostelecky. "Discovering them would be like finding a camel in a haystack instead of a needle."
If the findings help reveal the first evidence of Lorentz violations, it would prove relativity is not exact. Space-time would not look the same in all directions and there would be measurable relativity violations, however minuscule.
The violations can be understood as preferred directions in empty space-time caused by a mesh-like vacuum of background fields. These would be separate from the entirety of known particles and forces, which are explained by a theory called the Standard Model that includes Einstein's theory of relativity.
The background fields are predicted by a generalization of this theory called the Standard Model Extension, developed by Kostelecky to describe all hypothetical relativity violations.
Hard to detect, each background field offers its own universal standard for determining whether or not an object is moving, or in which direction it is going. If a field interacts with certain particles, then the behavior of those particles changes and can reveal the relativity violations caused by the field. Gravity distorts the fields, and this produces particle behaviors that can reveal otherwise hidden violations.
The new violations change the gravitational properties of objects depending on their motion and composition. Objects on the Earth are always moving differently in different seasons because the Earth revolves around the Sun, so apples could fall faster in some seasons than others. Also, different objects like apples and oranges may fall differently.
"No dedicated experiment has yet sought a seasonal variation of the rate of an object's fall in the Earth's gravity," said Kostelecky. "Since Newton's time over 300 years ago, apples have been assumed to fall at the same rate in the summer and the winter."
Spotting these minute variances is another matter as the differences in rate of fall would be tiny because gravity is a weak force. The new paper catalogues possible experiments that could detect the effects. Among them are ones studying gravitational properties of matter on the Earth and in space.
The Standard Model Extension predicts that a particle and an antiparticle would interact differently with the background fields, which means matter and antimatter would feel gravity differently. So, an apple and an anti-apple could fall at different rates, too.
"The gravitational properties of antimatter remain largely unexplored," said Kostelecky. "If an apple and an anti-apple were dropped simultaneously from the leaning Tower of Pisa, nobody knows whether they would hit the ground at the same or different times."
Animation using Kostelecky's Standard Model Extenstion to predict how apples might fall differently can be viewed at http://www.physics.indiana.edu/~kostelec/movies/agrav3.avi .
Paper: http://link.aps.org/abstract/PRL/v102/e010402 .
Source: Indiana University
Oct 15, 2008 |
not rated yet |
0
http://aetherwave...tum.html
http://aetherwave...ity.html
He did ~200,000! measurements vs MM 63.
There is a sidereal signal in data...
This sounds to me like his attempt at making his theory palatable to the "Einstein can do no wrong" crowd. It's like adding a note at the end of the standard model that says "PS - By the way, what you just read is not completely valid."
The bottom line is it's amazing how LITTLE we know about gravity.
-fleem
Can you define this concept please?
The momentum of the universe is certainly relative to the observer. However, the magnitude of that momentum in the eyes of a given observer varies with the velocity of the observer (relative to any given reference frame). There is a "preferred" velocity in which the magnitude of the momentum of the universe is zero.
In a closed universe, the kinetic energy of the universe appears greater for an observer moving relative to that preferred IRF. There is some question even among the standard model crowd about the role of that preferred velocity--for example, should we consider it affecting the observer's gravitational potential energy relative to an observer in some other inertial reference frame. Admittedly the effect is extremely slight, if there is any. On a side note, I believe the apparent paradox lies in a misinterpretation of the concept of "kinetic energy". In other words, that question among even proponents of pure GR have forgotten that kinetic energy is something that resides ~between~ two closed massive systems--you can't extract kinetic energy from a moving object without using a machine attached to a massive stationary object. (the same applies to potential energy, for that matter--you can't extract potential energy unless a machine connects to both objects between which the potential energy exists). This, then, gives rise to the question, "Where exactly ~is~ the kinetic or potential energy of a two-body system? Is it located within one object, the other object, or between the two".
We get so used to thinking of kinetic energy residing within an object moving relative to ourselves, that we forget such fundamental, but paramount, questions.
Anyway that is where the confusion lies. By stating that there is some question even among proponents of GR, I do not mean to imply I question GR--except maybe I'd like a clarification of some of the fundamental concepts like "where is a given amount of kinetic energy actually ~located~"--which is sometimes ignored in the community.
-fleem
I am a layperson about GR, so please forgive me in advance all mistakes and misconceptions I might make. What I want to point at is the very concept of spacetime. GR speaks of gravity being a distortion/curvature of the spacetime fabric. But there is no theory that even attempts to define spacetime itself. That is to say, how to define distance or time interval? What are they? If we take two separate points in space, two separate points in time, or two separate events in spacetime, what determines their separation? What IS that separation? I would believe some sort of flux relation; a dynamic process. Our human experience makes us take the sense of space and time for granted, as a given, subject to no explanation. But in my opinion, answering that question is fundamental for understanding gravity. Because if gravity is a curvature of spacetime, then we'll never comprehend what gravity is without explaining spacetime in the first place. Also, there is a popular assumption that spacetime is a 4-dimensional reality, where a time axis is perpendicular to the 3-spatial axes. But, as I understand, GR tell us that spacetime is a unified entity, without division between spatial and temporal dimensions. This is somehow contrary to our daily experience (and most importantly: thermodynamics), where space and time have different symmetries (invariance in space vs arrow of time). But what if this is only an illusion? That is, spacetime as a single, unified dimensional system is highly symmetric, but perhaps not based on classical (non)euclidean cartesian model, but something much more complex (bootstrap logarithmic distribution? rotational symmetry? polyhedral symmetry?). In any case, such a system would in fact be a 3D system of dimensions, whose manifestation in our daily experience makes us distinguish spatial and temporal components, which truly are just different "angles" at which we perceive reality.
I know this is a bit confusing, but the bottom line is: we have no explanation of spatial and/or temporal separatedness (distance).
Also: If we want to be accurate, can we be speaking of points in spacetime, or just regions thereof? In other words: if such qualities as momentum or distance are inherently relative and dynamic, does it make sense to speak of points?
fleem & others, I look forward to your comments and smashing critique showing how horribly I'm wrong... ;)
Now to wax more philosophical, here's my take on GR:
GR is strictly a classical theory. It assumes there are continua like manifolds and so on. There aren't. There's no such thing as a continuum. We've all been laughing at Zeno's paradox, but its time the smiles faded. The universe is discrete. (Now by discrete I don't mean there's a mesh in space-time. I simply mean there are indivisible interactions of particles which are what ~define~ space-time rather than "reside" in space-time).
Space-time is strictly a classical concept that has no place in quantum mechanics (or at least without major revision). Certainly quantum mechanical interactions take place with a certain order that obeys causality, but why do we even say there is such a global thing as "time"? Well, because when we look at two macroscopic clocks sitting on a shelf which are ticking at the same rate, we assume there is a ~global~ "field" that forces those clocks to tick at the same rate. However, those clocks are part of the same system--they are exchanging myriad virtual photons because they are so large, near each other, and yes, even hot. That's why they tick at the same rate. If we make tiny clocks and cool them way down, we see their time rates are much more independent.
So space-time is a man-made concept (continuum) which is really only useful in describing an ~average~ pattern of interactions among many particles.
-fleem
Indeed. We cannot derive the Lorentz invariance violation by using of theory based on relativity and Lorentz invariance by formally clean way without usage of black magic. It's virtually impossible to derive 1=2 by using of 1=1.
This is basically string and quantum gravity approach. I.e. to guess the solution - which can be done by a much cheaper way, indeed.
As for gravity we have no clue. We don't even know what the carrier particle is - or even if there is one. Time is just as elusive as gravity.
I believe that there is a link between charge and gravity. Look at the equations and they are earily similar. That is not just coincidence.
Newtons Law for Gravity
http://en.wikiped...vitation
Coulombs Law
http://en.wikiped...’s_law
In the process of obtaining knowledge of reality, we by necessity, conform it within pre-existing mental paradigms; causality, space-time. These concepts are not applicable outside that realm in which our minds have evolved to operate on.
It is supposed to be the graviton but if it exists it is too weak to be detected easily and so far nobody was able to craft an experiment to test the existence of gravitons but if quantum gravity is right then gravitons should exist.
Sometimes I get the impression that general relativity should undergo a different mathematical formalism. However, you are right there are many concepts in physics which have no 'concrete' definition. The only reasonable approach is mathematics, mainly when we are dealing with the foundations of space-time and matter. If you are going to be a theoretical physicist, for example, then math is the best way of dealing with the strange worlds of QM and GR.
No wonder that the mystics love quantum mechanics. :)
Yep. Of course its all we have to go by so we continue to play the game :)
However there is one "axiom" that proves itself, and that is "I think therefore I am", which proves the statement, "there is order". Beyond that its just a game of probabilities, because there is no such thing as a deductive proof without axioms (assumed laws). Thus two plus two ~probably~ equals four, but it might not always equal four. For that matter two might not always equal two.
However, I like to hope that there ~might~ someday be a way to take "I think therefore I am" and arrive at a TOE ~without~ axioms. Now THAT would be something.
-fleem
Yes, deductive propositions are self contained and true by virtue of the starting definitions (like Descartes line), and cannot tell us, in themselves, anything new about reality. Hume showed that there is no analytic link between cause and effect, only constant conjunction of observed events, so our inductive knowledge can only be certain by at best a high degree of probability.
Even if a TOE existed it would still be delimited by mental constructs and would be in a form dependant on mental ordering. If we had an invisible dog, or Louis Carroll's invisible cheshire cat, our knowledge would only be about the leash. :) What's important of course us that we can make predictions, but the point is certain concepts are not the reality itself but a means of ordering that reality for thought.
As is mentioned above, the core of the problem is understanding what space-time is, what is it made of, what is the quantum of discrete space-time.
Unfortunately for string theorists this approach negates one of the raison-d'etres for string theory - the requirement of a spin-2 particle resembling the graviton. As much of physics is ruled by string theorists, huge amounts of research into space-time rather than new particles predicted by string theory are not carried out.
There is now solid evidence that a direct interaction between gravitation and electromagnetism does not take place.
ABSTRACT "Time resolved images from the center of the Galaxy appear to counter General Relativity", Dowdye, Jr., E.H., http://adsabs.har...28..186D
For decades now some very important fundament principles of mathematical Physics have been incorrectly applied to the theory of gravitational lensing or just simply ignored. From astrophysical observations it is apparent that the current understanding of the effects that gravitation should have on light is fundamentally incorrect. Astrophysical observations pertaining to lensing are consistent with effects due to an indirect interaction involving an interfering media, not a direct interaction taking place in vacuum space. It is however theoretically possible that current technical means may not permit a distinction to be made between an indirect and a direct interaction between gravitation and light. The thin plasma atmosphere of the sun represents an indirect interaction between the gravitational field of the sun and the rays of light from the stars. There is convincing observational evidence that a direct interaction between light and gravitation is yet to be observed. Historically, the observed evidence for light bending occurred predominantly near the plasma rim of the sun, not in the vacuum space far above the rim. The events taking place at the site of Sagittarius A* presents convincing observational evidence that a direct interaction between rays of light and gravitation in vacuum space simply does not take place. This is clearly revealed in the time resolved images of the rapidly moving stellar objects orbiting about Sagittarius A*, a region at the galactic core believed to be a super massive black hole. This is a region that has been under intense observations by the Astrophysicists since 1992. A clear lack of observational evidence for optical lensing due to gravitation is apparent when examining the undistorted images of the stars moving along Keplar paths about Sagittarius A*. The space in the immediate vicinity of a black hole is by definition an extremely good vacuum. The evidence for this is clearly seen in the highly elliptical orbital paths of the rapidly moving stars orbiting about the galactic core mass. The presence of any material media near the galactic core mass would conceivably perturb the motion of the stellar object s16 moving with fractional light velocities, thus causing it to rapidly disintegrate. Astrophysical observations reveal that s16 has a velocity approaching 3 % of the velocity of light when passing to within a periastron distance corresponding to 60 astronomical units from the black hole thus giving solid evidence that the space in this region has to be, without a doubt, an extremely good vacuum. It follows from this that a direct interaction between the light emitted from the orbiting stars and the gravitation of this super massive galactic core at the site of Sagisttarius A* is yet to be observed.
For details see: http://www.extinc...ings.htm
A paper on this subject has been published in the renown refereed journal Astronomische Nachrichten, "Time resolved images from the center of the Galaxy appear to counter General Relativity", Dowdye, Jr., E.H., Astronomische Nachrichten, 328, Issue 2, 2007,pp 186 -191
For real astrophysical data and collected images/movies see link to
Max-Planck-Institut für extraterrestrische Physik:
For details: http://www.mpe.mpg.de
Movie Image: http://www.extinc...2003.gif
You wrote:
Regards
EHD
Are you an armchair physicist or a real one i.e. PhD in physics?