Glasperlenspiel: Scientists propose new test for gravity

September 1, 2010
Glasperlenspiel: NIST scientists propose new test for gravity

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A beam of laser light (red) should be able to cause a glass bead of approximately 300 nanometers in diameter to levitate, and the floating bead would be exquisitely sensitive to the effects of gravity. Moving a large heavy object (gold) to within a few nanometers of the bead could allow the team to test the effects of gravity at very short distances. Credit: K. Talbott/NIST

A new experiment proposed* by physicists at the National Institute of Standards and Technology may allow researchers to test the effects of gravity with unprecedented precision at very short distances -- a scale at which exotic new details of gravity's behavior may be detectable.

Of the four fundamental forces that govern interactions in the universe, may be the most familiar, but ironically it is the least understood by physicists. While gravity's influence is well-documented on bodies separated by astronomical or human-scale distances, it has been largely untested at very close scales—on the order of a few millionths of a meter—where electromagnetic forces often dominate. This lack of data has sparked years of scientific debate.

"There are lots of competing theories about whether gravity behaves differently at such close range," says NIST physicist Andrew Geraci, "But it's quite difficult to bring two objects that close together and still measure their motion relative to each other very precisely."

In an attempt to sidestep the problem, Geraci and his co-authors have envisioned an experiment that would suspend a small glass bead in a "bottle," allowing it to move back and forth within the bottle. Because there would be very little , the motion of the bead would be exquisitely sensitive to the forces around it, including the gravity of a heavy object placed nearby.

According to the research team, the proposed experiment would permit the testing of gravity's effects on particles separated by 1/1,000 the diameter of a human hair, which could ultimately allow Newton's law to be tested with a sensitivity 100,000 times better than existing experiments.

Actually realizing the scheme—detailed in a new paper in —could take a few years, co-author Scott Papp says, in part because of trouble with friction, the old nemesis of short-distance gravity research. Previous experiments have placed a small object (like this experiment's glass bead) onto a spring or short stick, which have created much more friction than laser suspension would introduce, but the NIST team's idea comes with its own issues.

"Everything creates some sort of friction," Geraci says. "We have to make the laser beams really quiet, for one thing, and then also eliminate all the background gas in the chamber. And there will undoubtedly be other sources of friction we have not yet considered."

For now, Geraci says, the important thing is to get the idea in front of the scientific community.

"Progress in the scientific community comes not just from individual experiments, but from new ideas," he says. "The recognition that this system can lead to very precise force measurements could lead to other useful experiments and instruments."

More information: * A.A. Geraci, S.B. Papp and J. Kitching. Short-range force detection using optically cooled levitated microspheres. Physical Review Letters, Aug. 30, 2010 (online). 105, 101101 (2010) DOI: 10.1103/PhysRevLett.105.101101

Provided by National Institute of Standards and Technology (news : web)

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Xaero
Sep 01, 2010

Rank: 1.3 / 5 (15)
..There are lots of competing theories about whether gravity behaves differently at such close range..
A similar experiment was proposed as a test of extra-dimensions of string theory.

http://www.scient...tra-dime

This test failed, although scientists attempted to filter out all sources of errors and noise: electrostatic forces, van der Waals forces and even Casimir force. Or just because of it - in dense aether theory all these forces are just the evidence of extradimensions, which are violating inverse square law for gravity at short distances.
TabulaMentis
Sep 01, 2010

Rank: 4.4 / 5 (7)
"According to the research team, the proposed experiment would permit the testing of gravity's effects on particles separated by 1/1,000 the diameter of a human hair, which could ultimately allow Newton's law to be tested with a sensitivity 100,000 times better than existing experiments."

This sounds like an experiment that needs to be done ASAP!
Where do I send my money?
NotAsleep
Sep 01, 2010

Rank: 3.7 / 5 (3)
..There are lots of competing theories about whether gravity behaves differently at such close range..


I'd like to reword that a little bit ("there are competeing theories about how gravity behaves at close range" might make more sense), what are these theories? I feel like gravitational theories are kept really quiet, barring the theories on the origin of mass
Xaero
Sep 01, 2010

Rank: 1 / 5 (12)
The problem of contemporary physics is, it describes existing forces separately with many theories, which can be quite exact locally (and as such they're considered true), but the vacuum density is actually a continuum, where intrinsic forces are melted together with extrinsic ones. Formal math cannot describe such system easily, because it adheres to either intrinsic perspective (general relativity), and or extrinsic perspective (quantum mechanics) - but nothing between it.

But when we're sitting inside of some gravity lens or blob of vacuum density, then we're always both inside of this blob, both outside of it. The resulting perspective is mixed in similar way, like for observer at the water surface, where the resulting ripples are always a mixture of both surface (transverse) waves, both underwater (longitudinal) waves.

As the result, water surface is never only simply two-dimensional or three-dimensional - but something between 2D and 3D.
Xaero
Sep 01, 2010

Rank: 2 / 5 (16)
This sounds like an experiment that needs to be done ASAP! Where do I send my money?
You can save your money, because such experiments were done many times during research of Casimir force. They even used a light wave levitation of tiny dropplets and/or glass spheres in optical tweezers - you're just fooled with the fact, they're described as a test of gravity, not Casimir force.

http://www.nature...443.html

Scientists are lobby and/or selfish meme like any other influential group of people. You should realize, scientists as a whole aren't very motivated into mutual reconciliation and coalescing of their insights, experiments and theories - it enables them to get more grants fr individual projects and to survive easier inside of human society. The more of seemingly different forces, experiments and theories, the better for such physicists.
Xaero
Sep 01, 2010

Rank: 1.8 / 5 (16)
We even observe the positive feedback here: the laymans are fooled the more, as the number of various articles about the same thing increases. In this way the progress in science becomes merely illusive. Only people, who can navigate in fast increasing number of experiments, ideas and theories can recognize their similarity and to reduce their number - not individual specialists.

Of course, such people are universally hated by all people, who are profiting from existing conceptual mess in less or more conscious way. Scientists want new money for experiments, whereas journalists and laymans want new reports about them - nobody cares, whether these experiments are actually bringing some new insights or not.

It's a sort of new religion based on informational consumerism: people are pilling informations like journals and books in their libraries without actually reading them.
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (14)
The water surface is a good model for explanation of the difference between intrinsic and intricate perspective. As I told already, there are two main kinds of waves: transverse and longitudinal ones. The transverse waves are spreading more slowly, so that the space-time represented with these waves appears most large in wavelengths, where these waves are dominant - it explains, why we are observing Universe in transverse waves nearly exclusively.

Toward both smaller, both larger scales the longitudinal character of waves increases. These waves are spreading in extradimensions, so that the dimensionality of space-time increases. It manifests with fuzziness of our Universeat both cosmological scale, both at the quantum scale. The very long ripples at the water surface are spreading in the same longitudinal way, like the very tiny ones, which are coupled with Brownian noise of underwater and as such they violate the inverse law, which is exactly valid only for pure transverse waves.
gold2_718
Sep 01, 2010

Rank: 5 / 5 (7)
So Xaero, do you know these scientists who are just in it for experiment money? It seems to me that since the levitated bead is not conducting, any Casimir force would be quite small and in any case, we can calculate the size of the effect and take it into account. Read the papers, do the calculations, and then chime in on how we are not putting ideas together. Go to one of the big conferences where we share these ideas openly. See the discussions in the hallways where we examine each other's work and try to figure out the big picture. Sure, things are a mess right now - trying to figure out why is what science is all about!
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (14)
Therefore we can interpret common short distance forces both with masive violation of inverse square law for gravity due the extradimensions, both violation of Lorentz symmetry in strictly 3D space at the distance scale bellow and/or above 2cm.

But not at the same moment, because the ratio between violation of gravity and Lorentz symmetry is of antropocentric, observer dependent origin. We shouldn't consider deformed gravity in deformed space-time - or we'll get lost in fuzzy double reasoning. This is why we are keeping pair of mutually contradicting inconsistent theories, i.e. general relativity and quantum mechanics and why the further development in physics splits into LQG and string theory.
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (15)
do you know these scientists who are just in it for experiment money
The motivations, which I described above are of emergent nature and they cannot be assigned to individuals. But this doesn't make them less effective. Subjectively all these scientists just want to propose NEW ORIGINAL experiments, which is definitely perfect. But such originality is not what is expected for reconciliation of existing theories and experiments.

The Casimir force was indeed studied with droplets in mixtures of dielectric fluids (where it can be both positive, both negative depending on permitivity and permeability constant ratio). Actually you cannot measure any other deviation of gravity from inverse square law, then just van der Waals and London's cohesion forces and Casimir force. If we will exclude all these forces, we'll find no violation of gravity, because we just neglected all possible violations already. We can spend incredible amount of money in such experiments without any result.
Xaero
Sep 01, 2010

Rank: 1.7 / 5 (12)
Go to one of the big conferences where we share these ideas openly
Which conference do you mean? I was banned from all large public forums dedicated to physics already. These guys apparently didn't realize, I'm forced to explain their incompetence in wider connections at more public forums, after then.
TabulaMentis
Sep 01, 2010

Rank: 3.4 / 5 (5)
@Xaero

"This is why we are keeping pair of mutually contradicting inconsistent theories, i.e. general relativity and quantum mechanics and why the further development in physics splits into LQG and string theory."

What happened to Dense Aether Theory?
gold2_718
Sep 01, 2010

Rank: 5 / 5 (9)
Looking for deviations means excluding everything you understand to see if something new occurs. That is the point of the experiment. Whether you call it one force or many is irrelevant. The point is that we can calculate what we think will happen but then, we have to check because we don't get to pick Nature's laws, we can only deduce them from experiment. We are at a crossroads in that theorists are proposing ideas for what is going on the regime where quantum field theory and general relativity seem to break down (or at least disagree with each other). This is pushing the experimentalists to come up with new and clever ways to test these ideas.
Your continual sniping at the scientific establishment is counter-productive at best and is starting to smell of sour grapes.
NotAsleep
Sep 01, 2010

Rank: 5 / 5 (10)
Go to one of the big conferences where we share these ideas openly
Which conference do you mean? I was banned from all large public forums dedicated to physics already. These guys apparently didn't realize, I'm forced to explain their incompetence in wider connections at more public forums, after then.


...ok, you got me. How'd you get banned from public forums?
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (12)
What happened to Dense Aether Theory?
Dense aether theory just explains this dichotomy as a more general metatheory.

Why truth has just two sides? Why the democracy converges into two main parties and/or social arrangements (conservative and liberal ones)? Why foam consists of rather spherical membranes with just two surfaces? Why we haven't three or more main physical theories?

It's all geometric stuff, resulting from dispersive character of energy spreading through inhomogeneous particle environment. Inside of such system just three dimensional artifacts with two dimensional surface exhibit the highest distance/surface ratio, thus providing the highest energy density due the principle of least action and largest space-time from intrinsic perspective. Just the three dimensional spheres exhibit the most compact arrangement - not circles, not hypersheres. Any other way would make our Universe a much smaller and temporal.
http://mathworld....ing.html
Xaero
Sep 01, 2010

Rank: 1.4 / 5 (9)
How'd you get banned from public forums?
Usually I got a warning message and my account was suspended and/or locked for writing. Actually it's a technical stuff of DB specialists, which has no meaning here.
gold2_718
Sep 01, 2010

Rank: 4.4 / 5 (7)
@Xaero, So you are a serious scientist, just misunderstood by all the riff-raff at conferences? Sorry to hear that. If you send me a paper that has been rejected from publication, I will try to get it accepted (that is, if it does not contain obvious flaws by which I mean predictions which are contradicted by well-tested experiments. Papers don't have to be 'right' to get published, just not obviously wrong). While you are at it, please also send the comments from the referees, I'd like to see why they don't understand your reasoning.
Xaero
Sep 01, 2010

Rank: 1.4 / 5 (11)
Your continual sniping at the scientific establishment is counter-productive at best..
Nope, you can explain many dense aether stuff with it. Actually people don't understand their own society in the same way, like the Universe itself.

http://www.dailyg...ang.html

But because people can be approximated with colliding particles following energy density gradients like particles of gas, we can model them with dense Boltzmann gas based theory in the same way, like the evolution of Universe. Actually such similarity is not accidental at all ("Simmilia simillibus observentur") - we can find many similarities just at very global scales. So we can learn many stuffs about social and biological evolution from Universe evolution and vice-versa and every analogy simplifies the understanding of the rest.
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (14)
If you send me a paper that has been rejected from publication, I will try to get it accepted
It's apparent, your approach is sticking on well established "Work-finish-publish" paradigm of Faraday, which actually increases the level of knowledge fragmentation and conceptual confusion of modern science, if you try to think about it. It's a good or maybe necessary model of presentation as a criterion of scientific salary - but it's not a good model for explanation of most general connections, which is basically a continuous neverending process.

It's completely dual paradigm to existing scientific method, which wouldn't be possible without Internet, where people can teach and learn mutually in small pieces in distributed way. It's targeted to understanding of connections, not their description and/or formulation in formal way. Most of people don't want to calculate anything and they don't need any equations for understanding of physics.
Xaero
Sep 01, 2010

Rank: 1.3 / 5 (12)
Sure, things are a mess right now - trying to figure out why is what science is all about!
Only theoretically - in real praxis the scientists avoid intuitive models, whenever possible ("shut up and calculate"). Formulation of various formal regressions based on randomly picked sets of ad-hoced postulates is not an understanding, it's still just a regression - no matter, how succesfull you're in it.

The understanding is, if you can explain or even predict experimental results in logically robust and reproducible way, i.e. without ad-hoced axioms and approaches, like the renormalization.

You're not required to read any publications of mine - just make familiar with Oliver Lodge's books first. This approach will not tell you, how much the gravity will be violated in the experiment like this one above described - but you will understand, what you're actually doing.
Pyle
Sep 01, 2010

Rank: 4.9 / 5 (10)
Only theoretically - in real praxis the scientists avoid intuitive models, whenever possible

No. Scientists avoid intuitive models that aren't verifiable by experimental results. Ambiguous explanations with no predictive value are worthless. If a theory is able to explain a phenomenon or result, and is NOT contradicted by
well-tested experiments
then it is worth something. Even better if it is able to predict the results of future experiments.

Until then,
word salad
.
Question
Sep 01, 2010

Rank: 1 / 5 (2)
Could gravity (weight) just be the effect we feel from time running slower toward the center of a mass? A relatively simple explanation of why this time runs slower toward the center of mass and how heat plays a role also is given at this link:
http://www.scribd...-Physics

(Let me try this again and see what happens.)
There is also a test proposed.
Xaero
Sep 01, 2010

Rank: 1.7 / 5 (12)
Ambiguous explanations with no predictive value are worthless..
Why not, but can you be less ambiguous? Which explanations do you mean exactly - and how can you demonstrate their ambiguity?
Skeptic_Heretic
Sep 01, 2010

Rank: 4.5 / 5 (11)
This is why we are keeping pair of mutually contradicting inconsistent theories, i.e. general relativity and quantum mechanics
Those two theories are not mutually contradictory. You don't seem to understand either of them.
_ilbud
Sep 01, 2010

Rank: 4 / 5 (8)
Man it's like the secret meets physics with the ontology of Glen beck.
gold2_718
Sep 01, 2010

Rank: 5 / 5 (8)
Could gravity (weight) just be the effect we feel from time running slower toward the center of a mass? A relatively simple explanation of why this time runs slower toward the center of mass and how heat plays a role also is given at this link:
http://www.scribd...-Physics


First, time runs more slowly the more intense the gravitational field. At the center of mass of a large body, the gravitational force due to that body vanishes (if you could carve a cavity at the center of the Earth, you would be weightless inside). Second, John E. Royer's book is a classic example of finding an alternative explanation by ignoring inconvenient facts. He does away with quarks and cannot explain either the scattering patterns of high-energy nucleon collisions or the formation of gluon 'jets'. Scientists are not allowed to ignore established experimental facts when creating new theories.
xamien
Sep 01, 2010

Rank: 5 / 5 (10)
Man it's like the secret meets physics with the ontology of Glen beck.


HAH! That made me smile.

Seriously, Xaero, if you feel that your contributions are that important and that you have the evidence to back your assertions (or at least some way to gather said evidence), then the only other problem standing in your way must be the way you socially interact with the scientific community. I think you need to read Thomas Kuhn's work.
KBK
Sep 01, 2010

Rank: 1.4 / 5 (10)
A good and successful scientist who brings new understandings about-is also a decent physiologist. A decent psychologist is aware that they are fundamentally full of crap, and does their best to not have that intrude in their ruminations and in that moment goes further forward than their notably more self-ignorant brethren.

"Godel's statement G", in the incompleteness theorem, in human psychological terms, as allied to the very incompleteness of the scientist and their problem. If the scientist cannot stand outside of their own limitations, then they will never complete or come to solution in the given problem.

Scientists, first and foremost, left brained and logical-objective, are only using half their faculties, and need to stick a knife in their metal guts and churn it around and around and fix themselves. Then they can begin to see answers to difficult problems.

Until then they will run in circles like confused and upset children, unwilling to see realities.

As real as it gets.
migmigmig
Sep 02, 2010

Rank: 4.7 / 5 (11)
Translation of Xaero:

"Blah blah Aether Wave. Blah blah scientists are evil and selfish and don't collaborate. Blah blah they laughed at me so I hate them."

I will readily admit I don't have the mathematical chops to tell you you're full of bat guano.

I will readily admit that if you weren't full of bat guano you wouldn't have to be trying to "prove" your guano to a bunch of layman dweebs like me on a public science website.

I'm sure you think you're important. I'm sure you think you're right.

There've been a handful of people in the world who, in the face of rejection, have kept to their guns and been later proven right.

Wake me up when that happens.
migmigmig
Sep 02, 2010

Rank: 4.7 / 5 (11)
Oh, yes, and if I did have the mathematical chops to point out your dripping white guanoburgers to you, of course I'm sure you would consider me one of those evil, selfish, scientist types.

And, as such, I would be immediately dismissed as one of the conspiracy of people who are actively preventing you from receiving the deep adulation you so desperately deserve.

Am I getting close?

Oh, wait, I won't read this article again.

So feel free to reply, but I'm sure you'll be able to figure out my counter-reply by its absence.
hodzaa
Sep 02, 2010

Rank: 1.4 / 5 (9)
Those two theories are not mutually contradictory..
These two theories (i.e. general relativity and quantum mechanics) are giving contradictory predictions regarding vacuum energy density and/or cosmological constant, which differ in more than one hundred orders of magnitude.

http://en.wikiped...astrophe

This discrepancy has been termed "the worst theoretical prediction in the history of physics!"
..if you feel that your contributions are that important and that you have the evidence to back your assertions, then the only other problem standing in your way must be the way you socially interact with the scientific community....
I've no problem in communication with scientific community - so far I haven't banned any of readers of my blogs.
hodzaa
Sep 02, 2010

Rank: 1.4 / 5 (9)
..Until then they will run in circles like confused and upset children, unwilling to see realities.
I explained, why and in which way scientists (theoretical physicists in particular) are motivated in their stance. This is not about stupidity and/or bad intentions - but about sociological factors, which are leading mainstream physical community to its deceptive behavior objectively. The correction of these factors is therefore not a job for scientific community itself, but for the rest of society. Scientists are just doing their very best, like every other community separated from reality. But what is good for physicists isn't always good for the rest of society. It's layman society, who is motivated to correct such disproportion, not physicists.
questioner
Sep 02, 2010

Rank: 1 / 5 (8)
an wow i forgot about how ur gravatationless at the centre of gravity > gold2_718 .. are u an actual scientist? like for real im asking? is any one comenting on here? does anyone have like a physics degree or just a wiki blog degree lol ...
Skeptic_Heretic
Sep 02, 2010

Rank: 4 / 5 (9)
These two theories (i.e. general relativity and quantum mechanics) are giving contradictory predictions regarding vacuum energy density and/or cosmological constant, which differ in more than one hundred orders of magnitude.
No, the vacuum catastrophy is the difference between the observation and the theoretical calculation. This has zero to do with classical mechanics, and only points to an unobserved attribute or an error in quantum field theory. CM and QM do not disagree, the problem is that they are irreconcilable. They are irreconcilable not due to disagreement but due to the lack of common ground on which to reconcile them.
Question
Sep 02, 2010

Rank: 1 / 5 (8)
gold 718
Quarks and gluons have in no way been proven, in fact quarks have never even been observed directly. They could be just a mathematical model, much like the ancient Greeks had a model to explain and predict the future positions of the moon and planets. As for gluon jets, they could be the spray of accumulated mass influence by magnetic fields.
It is the Standard Model that has accepted a number of things as facts that have not been proven.
hodzaa
Sep 02, 2010

Rank: 1 / 5 (7)
..they are irreconcilable not due to disagreement but due to the lack of common ground on which to reconcile them.
Ask a Mathematician: How/Why are Quantum Mechanics and Relativity incompatible?

http://www.askama...m/?p=714

These theories simply providing different results, not just the inconsistency with experiments. For example, from quantum mechanics follows the cosmological constant 10E+108 times larger, then from general relativity.

http://en.wikiped..._problem
hodzaa
Sep 02, 2010

Rank: 1 / 5 (5)
..in fact quarks have never even been observed directly...
Single top quark detected:
http://www.scienc...detected
http://www.univer...p-quark/
Question
Sep 02, 2010

Rank: 1 / 5 (2)
..in fact quarks have never even been observed directly...
Single top quark detected:
http://www.scienc...detected

The one link I could connect to claims a 1 in 20 billion chance they have observed a quark. This is exactly the odds I do not think makes for good science or proof.
If it cannot be repeated on a regular basis, what is it worth?

Skeptic_Heretic
Sep 02, 2010

Rank: 4.6 / 5 (10)
Single top quark detected:
That still isn't a direct observation.
These theories simply providing different results, not just the inconsistency with experiments. For example, from quantum mechanics follows the cosmological constant 10E+108 times larger, then from general relativity.
No, that's wholly inaccurate. The problem you're referring to is that we cannot derive the cosmological constant from the existing quantum field equations. Which means once again, QFE may be wrong or missing a findamental aspect of reality. There is no contradiction. Krause explains this problem in the RDF series, available on youtube, and shows through observational evidence that the problem is the non-inclusion of dark energy and the relatively unknown shape of the Universe that gives rise to this issue. You're out of your depth here. This is twice now that the texts you've linked explain the problem and you've ignored it. Read your own sources entirely before using them.
Gawad
Sep 02, 2010

Rank: 5 / 5 (4)
Could gravity (weight) just be the effect we feel from time running slower toward the center of a mass? A relatively simple explanation of why this time runs slower toward the center of mass and how heat plays a role also is given at this link:
http://www.scribd...-Physics

(Let me try this again and see what happens.)
There is also a test proposed.


Hi Question. The speed of time depends on the gravitational gradient. As the gradient increases the speed of time slows (as seen from an external reference frame). But at a center of mass the gradient is flat, so the speed of time is maximal, or c.
Sirinx
Sep 02, 2010

Rank: 1 / 5 (8)
The problem you're referring to is that we cannot derive the cosmological constant from the existing quantum field equations.
In cosmology the vacuum catastrophe refers to the disagreement of 107 orders of magnitude between the upper bound upon the vacuum energy density as inferred from data obtained from the Voyager spacecraft of less than 10E+14 GeV/m3 and the zero-point energy of 10E+121 GeV/m3 calculated using quantum field theory. Whereas general relativity requires cosmological constant to be very low

http://prd.aps.or.../e044029

or even zero

http://iopscience.../235019/

Which means, there is not only inconsistency of quantum mechanics with observations, but with predictions of general relativity, too. In GR cosmological constant can be NEVER the number with one hundred orders of magnitude.

You're just too uninformed for to realize it (and yyz, Question, frajo, panorama and Gawad who upvoted you with five points, too).
Sirinx
Sep 02, 2010

Rank: 1.4 / 5 (9)
It brings an apparent problem: could we ever reconcile formal theories, which are supplying/requiring an apparently different values (in range of one hundreds of magnitude) for the same quantity in rigorous way - or we are just wasting the money of tax payers for such re-search?

For formally thinking trolls this question was answered already, though: "Of course it has a good meaning, because it enables us to take salary for it"! The experiment above proposed just illustrates this ignorant approach at different level.
Question
Sep 02, 2010

Rank: 1 / 5 (2)
Gawad quote:
Hi Question. The speed of time depends on the gravitational gradient. As the gradient increases the speed of time slows (as seen from an external reference frame). But at a center of mass the gradient is flat, so the speed of time is maximal, or c.
But what does the gravitational gradient depend on? It depends on gravitons interacting with matter. And that increases with an increase in mass. The gradient at the center of a mass would at its maximum. But as you say flat and that is why matter would be weightless there. In other words the time and atom spent at all possible positions or directions is equal. No imbalance, no weight.

frajo
Sep 02, 2010

Rank: 4.4 / 5 (9)
You're just too uninformed for to realize it (and yyz, Question, frajo, panorama and Gawad who upvoted you with five points, too).
Your delusions of grandeur, Zephir, are just too massive to let you understand the reasons for your being downvoted or the reasons for the upvoting of your adversaries.
Gawad
Sep 02, 2010

Rank: 5 / 5 (4)
Gawad quote:
Hi Question. The speed of time depends on the gravitational gradient. ...

But what does the gravitational gradient depend on? It's litterally the shape of the local space-time and that depends on the distibution of matter, energy, pressure and everything else that goes into the stress-energy tensor for GR.
It depends on gravitons interacting with matter. And that increases with an increase in mass. The gradient at the center of a mass would at its maximum. But as you say flat and that is why matter would be weightless there. In other words the time and atom spent at all possible positions or directions is equal. No imbalance, no weight.
Personnally, I'd avoid treating gravitons and how they interact as real ("It depends on gravitons") as they're currently entirely speculative, even moreso than the Higgs. Not that treating gravity as the result of particle interactions can't give you the same result, AFAIK, but it just seems a little premature.
Gawad
Sep 02, 2010

Rank: 5 / 5 (2)
I absolutly despise that quote function.
Hi Question. The speed of time depends on the gravitational gradient.

But what does the gravitational gradient depend on?
It's litterally the shape of the local space-time and that depends on the distibution of matter, energy, pressure and everything else that goes into the stress-energy tensor for GR.
It depends on gravitons interacting with matter. And that increases with an increase in mass. The gradient at the center of a mass would at its maximum. But as you say flat and that is why matter would be weightless there. In other words the time and atom spent at all possible positions or directions is equal. No imbalance, no weight.
Personnally, I'd avoid treating gravitons and how they interact as real ("It depends on gravitons") as they're currently entirely speculative, even moreso than the Higgs. Not that treating gravity as the result of particle interactions can't give you the same result, AFAIK, but it just seems
Gawad
Sep 02, 2010

Rank: 5 / 5 (4)
a little premature. And, I can assure you that the *gradient* at a center of mass is *not* at it's maximum if it is *flat*. Think about it.
Question
Sep 02, 2010

Rank: 1 / 5 (3)
a little premature. And, I can assure you that the *gradient* at a center of mass is *not* at it's maximum if it is *flat*. Think about it.

I have thought about it and it can be both. While the gravity field or gradient would be at it maximum at the center its effect on time would also be at its maximum. But the effect on time is equal on all sides at the very center, you could describe things here as flat and having no effect on the weight of matter. Matter would be weightless.

Skeptic_Heretic
Sep 02, 2010

Rank: 5 / 5 (3)
You're just too uninformed for to realize it (and yyz, Question, frajo, panorama and Gawad who upvoted you with five points, too).
If I'm uninformed then why can't you recognize that in all problems with the reconciliation that the issue appears to be Quantum Field Theory, which we've known for a long time to be missing a significant piece of the puzzle? I know why but will you admit it? The reason why is because we don't teach quantum field theory to undergrads or highschool students. It requires significant mastery of dynamic physical mathematics, something that you're unable or unwilling to do. That and you keep saying "cosmological constant", it isn't a cosmological constant, it is vacuum energy density. Which in order to certify we must first determine what type of energy it is. The QFE doesn't denote negative or positive energy, it is quite possible that the energy balance is small but the content is large.

BTW: Another new screen name for Zephir, oh joy.
Skeptic_Heretic
Sep 02, 2010

Rank: 5 / 5 (3)
Oh and again, both of your references don't exemplify your point, if anything they agree with me, again.
Xaero
Sep 02, 2010

Rank: 1 / 5 (7)
...are just too massive to let you understand the reasons for your being downvoted...

You can claim before other readers, it's my usage of multiple accounts, which forces you to rate me low systematically. But it still doesn't explain, why you're up-voting the lies of Skeptic_Heretic the more, the more such lie is apparent - well, like mafia. Actually just this symmetry makes your true motivations apparent.

You all know very well, S_Heretic is spreading BS about physics, I'm I right?
Gawad
Sep 02, 2010

Rank: 5 / 5 (4)
I have thought about it and it can be both. While the gravity field or gradient would be at it maximum at the center its effect on time would also be at its maximum. But the effect on time is equal on all sides at the very center, you could describe things here as flat and having no effect on the weight of matter. Matter would be weightless.
It seems to me like you are co-minglling a hypothetical particle interaction with a geometric description of spacetime, and it's leading to a confused picture: maximum local gradients that are somehow not flat. Even if you want to treat gravitation as the result of particle interations (in this case having maximum interations at center of mass), be careful that doesn't lead you to a nonsensical geometric picture. And like I said, be careful with gravitons. How would frame dragging be handled through particle interactions?
Skeptic_Heretic
Sep 02, 2010

Rank: 4.4 / 5 (7)
You can claim before other readers, it's my usage of multiple accounts, which forces you to rate me low systematically. But it still doesn't explain, why you're up-voting the lies of Skeptic_Heretic the more, the more such lie is apparent - well, like mafia. Actually just this symmetry makes your true motivations apparent.

You all know very well, S_Heretic is spreading BS about physics, I'm I right?
Yes because if it is a lie about physics, the best place to get people to agree with it is a site dedicated to physics. Where people who are well educated in physics will see it, and somehow be fooled into agreeing with it.

Your paranoid delusions are at the level of necessary intervention. Please seek counseling.
Xaero
Sep 02, 2010

Rank: 1 / 5 (8)
..Your paranoid delusions are at the level of necessary intervention...
You're upvoted simultaneously by six people, which are always the very same in the range of few minutes... These people are willing to upvote BS's like your recent claim, relativity predicts the same value of cosmological constant, like the quantum mechanics - just for the sake of consistency of these theories in the eyes of layman public. Other, less controversial claims aren't upvoted by your suite, though.

Do you have some rational explanation for it? Or you're spreading propaganda here in organized way? You must be very proud of yourself - but you're actually doing a disservice to science.
Question
Sep 02, 2010

Rank: 2.3 / 5 (3)
Gawad: There is another way of looking at this center of the earth weightlessness. If you were in the center of the earth the gravity created by the earth's mass would be pulling on you equally in all directions. You could float around inside weightlessly. This concept my seem silly when applied to the earth but these same principles would apply to galaxies. As for frame dragging, the coriolis effect has no problem dealing with particles. I would love to know what you think a 100 pound weight would weigh in the center of the earth?
Gawad
Sep 02, 2010

Rank: 5 / 5 (4)
...your recent claim, relativity predicts the same value of cosmological constant, like the quantum mechanics...


Huh? Where the hell did S_H claim that??? If that's what you really think than you are completely misunderstanding his argument. Or you're putting up one hell of chew-your-arm-off-ugly strawman. If you are actually misunderstanding the argument, I can imagine a few possible reasons, but I have to wonder: is it possible that your command of English is insufficient to destinguish between notions like "contradict" and simply not being in the same realm of application? You do realize that Einstein's field equations don't tell you what the CC is, only that there is one. It's value is actually determined from observations when these are tied into the field equations. It's not in the equations themselves! What the QM values actually contradict (when they are infinate or on the order 10^120 too large) are cosmological observations themselves, not GR as such.
Gawad
Sep 02, 2010

Rank: 4.4 / 5 (5)
Gawad: There is another way of looking at this center of the earth weightlessness. If you were in the center of the earth the gravity created by the earth's mass would be pulling on you equally in all directions. You could float around inside weightlessly. This concept my seem silly when applied to the earth but these same principles would apply to galaxies. As for frame dragging, the coriolis effect has no problem dealing with particles. I would love to know what you think a 100 pound weight would weigh in the center of the earth?

Question, your 45kg mass wouldn't weigh anything because the local gravitational gradient you are describing is PERFECTLY FLAT. I follow this perfectly well, trust me. If it weren't flat your 45kg wieght would be heading off in some direction. Or trying to. If you consider that "maximal" there's a problem with how you see slopes.
Gawad
Sep 02, 2010

Rank: 4.2 / 5 (5)
As for frame dragging, the coriolis effect has no problem dealing with particles.


Frame dragging is not a coriolis effect.
Gawad
Sep 02, 2010

Rank: 5 / 5 (3)
Gawad: There is another way of looking at this center of the earth weightlessness. If you were in the center of the earth the gravity created by the earth's mass would be pulling on you equally in all directions. You could float around inside weightlessly. This concept my seem silly when applied to the earth but these same principles would apply to galaxies. As for frame dragging, the coriolis effect has no problem dealing with particles. I would love to know what you think a 100 pound weight would weigh in the center of the earth?

Wait a minute! You're confusing gradients with the notion of local maxima and minima. Ffft ! Doh!
Question
Sep 02, 2010

Rank: 1 / 5 (1)
Gawad, I agree with you about the gradient slope and I was not very clear about that. But the gravitational field is at it strongest in the center of the earth, time runs at its slowest there. I am glad to see you do agree with me about weight in the center of the earth. The coriolis effect is not the same as frame dragging but rotation and its effect on moving particles should the same.

frajo
Sep 02, 2010

Rank: 3.7 / 5 (6)
Question, your 45kg mass wouldn't weigh anything because the local gravitational gradient you are describing is PERFECTLY FLAT.
Sorry, but Question doesn't know what - inter alia - "gradient" means.
Question
Sep 02, 2010

Rank: 1 / 5 (2)
The gravitational gradient (effect on weight) and the strength of a gravitational field's effect on time are not the same thing.
The gradient is at its maximum on the surface of a mass, zero or flat at the center. The gravitational field's (density for lack of a better word) effect on time is at its maximum in the center of a mass.
Gawad
Sep 02, 2010

Rank: 3.4 / 5 (5)
But the gravitational field is at it strongest in the center of the earth, time runs at its slowest there.
Question, as long as we are talking in terms of SR and GR, time does not care how *strong* your local gravity field is as such. The speed of time depends on your...wait for it: ACCELERATION. If you are at rest at a center of mass your gavitational gradient is 0, you are in freefall, your acceleration is 0 and time in your reference frame runs at c. Period. You can imagine whatever you like, but then you're leaving SR/GR and venturing into phantasy physics.
Gawad
Sep 02, 2010

Rank: 4 / 5 (4)
The coriolis effect is not the same as frame dragging but rotation and its effect on moving particles should the same.
Just like that, eh? Man, it's a long, long road....
Question
Sep 02, 2010

Rank: 1 / 5 (1)
Quote from Gawad:
"Hi Question. The speed of time depends on the gravitational gradient. As the gradient increases the speed of time slows (as seen from an external reference frame). But at a center of mass the gradient is flat, so the speed of time is maximal, or c."

Now I see where we disagree, you think the slowing of time depends on the gravitational gradient. I think it depends of the gravitational field, not on the gradient. If you are correct time would not be slowed at all in the center of a mass, I say it would be slowed at its maximum.
Question
Sep 02, 2010

Rank: 5 / 5 (1)
Gawad
So we agree that at the very center of a mass matter would be weightless. We disagree on the gravitational gradient's effect on time.

So let me ask you a question, since you say gradient is the controling factor on time in a gravitation field where would a gravitational field be at its strongest? At the center of a body of mass or on its outer surface? You cannot say in the center because the gradient is flat at the center, we agree on that. But if you don't say the center you are ignoring the force of gravity on all sides of yourself. Which is it?
Gawad
Sep 02, 2010

Rank: 3.4 / 5 (5)
Now I see where we disagree, you think the slowing of time depends on the gravitational gradient. I think it depends of the gravitational field, not on the gradient. If you are correct time would not be slowed at all in the center of a mass, I say it would be slowed at its maximum.
Fair enough. I realized that a little while back. Thing is, GR says your gavitational gradient *is* your field strength.
Gawad
Sep 02, 2010

Rank: 3.7 / 5 (6)
Gawad
So we agree that at the very center of a mass matter would be weightless. We disagree on the gravitational gradient's effect on time.

So let me ask you a question, since you say gradient is the controling factor on time in a gravitation field where would a gravitational field be at its strongest? At the center of a body of mass or on its outer surface? You cannot say in the center because the gradient is flat at the center, we agree on that. But if you don't say the center you are ignoring the force of gravity on all sides of yourself. Which is it?

For a solid spherical body of uniform density the maximum gavitational gradient is at the surface. That's also where time runs the slowest.
Xaero
Sep 02, 2010

Rank: 1.4 / 5 (9)
We should realize, in strict special relativity context no lensing can be actually possible, because the light will spread through vacuum in the same invariant speed in all directions thinkable. If you're observing some lensing, you're observing the violation of special relativity and 4D dimensionality of space-time. It's extradimensions of space-time, what you're actually starring at in this case. And extradimensions mean violation of causality in quantum mechanics way: the multiple images of Einsteinian lenses are violating the determinism of reality in both time, both in space.

Maybe Mr. Einstein would be surprised, that he derived relativity with using of quantum mechanics phenomena - i.e. the theory, which he fought against for most of his life.
Gawad
Sep 02, 2010

Rank: 3.4 / 5 (5)
Question, as long as we are talking in terms of SR and GR, time does not care how *strong* your local gravity field is as such.
Sorry, I miswrote. Of course time cares how strong the *local* field is, in other words the field at your specific location. To clarify: time doesn't care how steep the gravitational gradient gets around you or *other than where you are*. In other words whether you are at the very center of a neutron star or a wispish hydrogen cloud makes no difference. In both cases the gradient is flat and time runs at c.
Gawad
Sep 02, 2010

Rank: 3.3 / 5 (7)
We should realize, in strict special relativity context no lensing can be actually possible, because the light will spread through vacuum in the same invariant speed in all directions thinkable. If you're observing some lensing, you're observing the violation of special relativity and 4D dimensionality of space-time. It's extradimensions of space-time, what you're actually starring at in this case. And extradimensions mean violation of causality in quantum mechanics way: the multiple images of Einsteinian lenses are violating the determinism of reality in both time, both in space.

Maybe Mr. Einstein would be surprised, that he derived relativity with using of quantum mechanics phenomena - i.e. the theory, which he fought against for most of his life.


Jesus. Italian or ranch with that?
Skeptic_Heretic
Sep 02, 2010

Rank: 2.3 / 5 (6)
At the center of massive galactic cluster, the net effect of gravitational forces will be compensated and effectively zero. But this center will still exhibit gravitational lensing and change in inertia of objects
No it won't. The very center of a galaxy is a black hole core. It does not lense. The lensing is performed by the event horizon which is spherical. You've never seen light from the exact center of a galaxy because it doesn't leave that center.
hodzaa
Sep 03, 2010

Rank: 2.7 / 5 (7)
..At the center of massive galactic cluster..
No it won't. The very center of a galaxy..
Can you understand the difference between galactic cluster and single galaxy? Btw not all galaxies contain black hole in its core - so your post is nonsensical even in its own context.
Skeptic_Heretic
Sep 03, 2010

Rank: 3.4 / 5 (5)
Can you understand the difference between galactic cluster and single galaxy?
Yes I can but your ability with the language is so poor it's difficult to determine what you actually mean in most instances. The center of a galactic cluster would not be the gravitational center of an object, it would be the center of mass, but not the gravitational center.
Btw not all galaxies contain black hole in its core - so your post is nonsensical even in its own context.

Show me one that you know does not have one with evidence please.
Gawad
Sep 03, 2010

Rank: 4.3 / 5 (6)
For a solid spherical body of uniform density the maximum gavitational gradient is at the surface. That's also where time runs the slowest.
Humm...this is interesting. Jigga/Xaero/Alizee/Sirix/Hodzaa/etc./etc./etc. disagrees with this simple statement (rated it a 1...but at least only once). I'd be curious to know why. Well, at least unless it directly involves Dense Aether Wave on Water Surface.
Skeptic_Heretic
Sep 03, 2010

Rank: 4.5 / 5 (8)
Humm...this is interesting. Jigga/Xaero/Alizee/Sirix/Hodzaa/etc./etc./etc.
I like the fact that he self ranks. It makes it easier to find his other screeen names and address his systemic abuses.
Xaero
Sep 03, 2010

Rank: 1 / 5 (7)
For a solid spherical body of uniform density the maximum gravitational gradient is at the surface. That's also where time runs the slowest.
Humm...this is interesting. ...etc. disagrees with this simple statement (rated it a 1...but at least only once). I'd be curious to know why...
Because you're mixing gravitational potential and curvature of space-time. The time runs the slowest at center of massive bodies, where gravitational force is zero. How the "gravitational gradient" is supposed to be defined?
Skeptic_Heretic
Sep 03, 2010

Rank: 4.4 / 5 (7)
Because you're mixing gravitational potential and curvature of space-time.
According to relativity, the gravitational potential is what determines the curvature of spacetime.
Sepp
Sep 03, 2010

Rank: 4.3 / 5 (3)
What beats me is how physicists can propose an experiment to find fine details of the behavior of gravity, while at the same time we can't even agree what causes gravity, i.e. what is the exact mechanism of it, and how gravity is transmitted (if it is) through the intervening space between objects.

Would not the larger question about the mechanism and cause of gravity be the first thing to resolve?
Gawad
Sep 03, 2010

Rank: 5 / 5 (3)
For a solid spherical body of uniform density the maximum gravitational gradient is at the surface. That's also where time runs the slowest.
Humm...this is interesting. ...etc. disagrees with this simple statement (rated it a 1...but at least only once). I'd be curious to know why...
Because you're mixing gravitational potential and curvature of space-time. The time runs the slowest at center of massive bodies, where gravitational force is zero.
O.k., hold on a sec. thar cowboy....So you're saying time runs the slowest where the gravitational force is ZERO. Essentially, this is the same claim as Question, did I get that right?
How the "gravitational gradient" is supposed to be defined?
O.k....sigh...how about the delta in gavitational force as the delta in distance from a gravitating body. Does that help? And along that gradient the body surface is the place where the gravity is strongest. Man, this isn't rocket science! Wait, a minute...hummm.

Gawad
Sep 03, 2010

Rank: 5 / 5 (3)
For a solid spherical body of uniform density the maximum gravitational gradient is at the surface. That's also where time runs the slowest.
Humm...this is interesting. ...etc. disagrees with this simple statement (rated it a 1...but at least only once). I'd be curious to know why...
Because you're mixing gravitational potential and curvature of space-time. The time runs the slowest at center of massive bodies, where gravitational force is zero. How the "gravitational gradient" is supposed to be defined?
Um, one more question, when you say "time runs the slowest...where gravitational force is zero" whose reference frame are you considering?
Xaero
Sep 03, 2010

Rank: 1 / 5 (7)
So you're saying time runs the slowest where the gravitational force is ZERO. Essentially, this is the same claim as Question, did I get that right?
Yep - I explained already, it violates the equivalence principle - see my posts above given.
TabulaMentis
Sep 03, 2010

Rank: 1 / 5 (3)
What beats me is how physicists can propose an experiment to find fine details of the behavior of gravity, while at the same time we can't even agree what causes gravity, i.e. what is the exact mechanism of it, and how gravity is transmitted (if it is) through the intervening space between objects.

Would not the larger question about the mechanism and cause of gravity be the first thing to resolve?

Check out this Physorg.com article about magnetism:

http://www.physor...904.html

Gravity and magnetism are great mysteries.

Maybe string theory, LQG theory, gravitybrane theory, or some other idea will eventually answer those questions.
DamienS
Sep 03, 2010

Rank: 4.4 / 5 (7)
What beats me is how physicists can propose an experiment to find fine details of the behavior of gravity, while at the same time we can't even agree what causes gravity, i.e. what is the exact mechanism of it, and how gravity is transmitted (if it is) through the intervening space between objects.

Would not the larger question about the mechanism and cause of gravity be the first thing to resolve?

This is nothing new. Humans have always exploited systems and process which they didn't initially understand at the fundamental level. For example fire, dyes, projectile aerodynamics and hydrodynamics and static electricity to name a few.

While we may not have a deep understanding of gravity, we can certainly measure its effects, form relations and make predictions. By doing more accurate measurements at scales previously unavailable, we may just detect something surprising which in turn may act as a trigger for a deeper, more fundamental understanding of gravity.
Cave_Man
Sep 04, 2010

Rank: not rated yet
alot of things seem to be changing in physics and science, seems like the blow link ties into particle physics because of the apparent between force, energetic particles and the structure of those particles on large scale more solid particle conglomerations.
http://www.flight...-to.html
ubavontuba
Sep 05, 2010

Rank: not rated yet
Btw not all galaxies contain black hole in its core - so your post is nonsensical even in its own context.
Show me one that you know does not have one with evidence please.
M33 doesn't have a detectable supermassive black hole.

"Rutgers astronomers have made a provocative discovery -- the first galaxy without a supermassive black hole (SBH) at its center..."

http://www.scienc...3143.htm

Anyway, don't mind me... I'm just in the mood to poke a hornet's nest with a short stick...

Skeptic_Heretic
Sep 05, 2010

Rank: 5 / 5 (1)
Selective quote mining.
the first galaxy without a supermassive black hole (SBH) at its center or the smallest black hole ever detected in the center of a galaxy.


The whole sentence is a little bit more descriptive after the provocative headline.
ubavontuba
Sep 05, 2010

Rank: not rated yet
Selective quote mining.
the first galaxy without a supermassive black hole (SBH) at its center or the smallest black hole ever detected in the center of a galaxy.
The whole sentence is a little bit more descriptive after the provocative headline.
Nah. The rest of the sentence just reiterates what I said above (if there is one, it's too small to be detected).

The whole sentence is a little bit more descriptive after the provocative headline.

ubavontuba
Sep 05, 2010

Rank: not rated yet
Selective quote mining.
the first galaxy without a supermassive black hole (SBH) at its center or the smallest black hole ever detected in the center of a galaxy.
The whole sentence is a little bit more descriptive after the provocative headline.
Nah. The rest of the sentence just reiterates what I said above (if there is one, it's too small to be detected).

The whole sentence is a little bit more descriptive after the provocative headline.

(apologies for the double post)
ubavontuba
Sep 05, 2010

Rank: not rated yet
Here's a link to an official paper:

http://iopscience...2/5/2469

"...best if the central black hole mass is zero."
Skeptic_Heretic
Sep 05, 2010

Rank: 2 / 5 (4)
Great paper, and that is their assertion, however it is an introductory paper on this particular study, and the author does note that there are very large holes in our ability to detect the lowest limit BH above the upper limit of 1500 M that they've determined.

I stand corrected, however, the finale is yet to come on this question.
ubavontuba
Sep 05, 2010

Rank: not rated yet
Great paper, and that is their assertion, however it is an introductory paper on this particular study, and the author does note that there are very large holes in our ability to detect the lowest limit BH above the upper limit of 1500 M that they've determined.

I stand corrected, however, the finale is yet to come on this question.

Yes. It's very thorough and well written.

Did you notice how they suggest that even if it approached the upper limit, it still wouldn't be massive enough to explain this galaxy's existence within current theories?

Quite an interesting conundrum.

A spooky hypothesis: Maybe it's not a natural galaxy, but rather an artifical structure... (que scary music)

Skeptic_Heretic
Sep 06, 2010

Rank: 2.5 / 5 (6)
Well they did also neglect to use K Band radio teloscopy to account for cold dust particles obscuring the view. Their mathematical modeling of the K Band was very thorough however I don't agree that it still lends creedence to a zero mass as best fit. We'll see what shakes out when our ability to view BHs gets better. Which should hopefully be soon.
MaxwellsDemon
Sep 06, 2010

Rank: 3.7 / 5 (6)
Humm...this is interesting. Jigga/Xaero/Alizee/Sirix/Hodzaa/etc./etc./etc.
I like the fact that he self ranks. It makes it easier to find his other screeen names and address his systemic abuses.

Lol, you're so right. It must be lonely being the only one who approves of yourself.
sender
Sep 07, 2010

Rank: 2 / 5 (2)
A simple experiment to test gravity in nm distances could utilize skyrmions and deuterium/osmium atoms suspended in a microgravity vacuum. The grave dissimilarities between atomic structure and magnetic impedance could yield polarimetric dissimilarities due to gravitational attractors.
Gawad
Sep 08, 2010

Rank: 5 / 5 (1)
So you're saying time runs the slowest where the gravitational force is ZERO. Essentially, this is the same claim as Question, did I get that right?
Yep - I explained already, it violates the equivalence principle - see my posts above given.

O.k....then how do you account for having to compensate for time running faster at higher orbits (where gravity is weaker) demonstrated by the gps sattellites are concerned? Also, at what speed do you figure time runs at the event horizon of a BH, where the gravitational field is massive?
MaxwellsDemon
Sep 08, 2010

Rank: 3.7 / 5 (3)
@Gawad:
For a solid spherical body of uniform density the maximum gravitational gradient is at the surface. That's also where time runs the slowest.

Excuse me, but that's false. Time dilation is a function of the gravitational potential, not the gravitational force/gradient:
Gravitational time dilation is the effect of time passing at different rates in regions of different gravitational potential; the lower the gravitational potential (closer to the center of a massive object), the more slowly time passes.


http://en.wikiped...dilation
NotAsleep
Sep 08, 2010

Rank: 1 / 5 (4)
100th post! Wow, now YOU guys are ridiculous
Gawad
Sep 09, 2010

Rank: not rated yet
@Gawad:
For a solid spherical body of uniform density the maximum gravitational gradient is at the surface. That's also where time runs the slowest.

Excuse me, but that's false. Time dilation is a function of the gravitational potential, not the gravitational force/gradient:

...

http://en.wikiped...dilation


Just because it's you, I went back to do some digging and it does look like the formula I was using applied only to the surface of a body and above. I found a more complete formaula where it is immediately evident that time dilation continues to increase as keep going down into the gravity well:

t=tau/sqrt(1+((2phi)/c^2)) where phi=(1/2((GMr^2)/(R^3))-(3/2(GM)/R) and R=body radius and r=distance from the centre of gravity. Accordingly, as the distance, r^2, goes to 0, dilation will continue to increase. So I'll concede the point, but not without some reservation as offhand this looks like a violation the the equivalence principle.
Gawad
Sep 09, 2010

Rank: 3 / 5 (2)
@Gawad: Look - if Question (and me) is saying, time runs the slowest where the gravitational force is ZERO, i.e. at the center of Earth, I can see nothing strange, when the time is running faster at higher orbits, where gravity is weaker. Do you?

Actually the same question applies for Skeptic_Heretic, who upvoted you in the mean-time. The consistent logical thinking makes an apparent problem for both of you.


Geeze! Another alias? How many is that? 42?

And, yes there is something "strange" about that. Because by your reasoning time runs SLOWER as the grav force goes to 0 (at the centre of a massive body) AND time runs FASTER as the grav force goes to 0 (as you move away from a massive body). Offhand, this is illogical as it is trying to have it both ways. I did dig up what I think is the correct reason and I concede the point to Maxwell (sorry about how the formula looks, it's the best I can do with physorg). But I'm still not entirely convinced, so I'll do some more digging.
Skeptic_Heretic
Sep 09, 2010

Rank: 3.7 / 5 (3)
if Question (and me) is saying, time runs the slowest where the gravitational force is ZERO, i.e. at the center of Earth, I can see nothing strange, when the time is running faster at higher orbits, where gravity is weaker. Do you?
Gravitational force cannot be zero in that circumstance. It may be a net force vector of zero, however, it isn't a zero effect.
MaxwellsDemon
Sep 09, 2010

Rank: 4.3 / 5 (6)
It pained me to agree with Jigga/Xaero/Alizee/Sirix/Hodzaa/wiki11/etc. on anything, but fortunately I doubt it'll ever happen again.

There's a fascinating relationship between gravitational potential energy, time dilation, and escape speed (aka 'escape velocity,' but that's a misnomer). As the gravitational potential energy reaches its most negative value at the center of a body (where we set the gravitational potential energy to zero at infinity), the escape speed reaches the maximum value, as does the magnitude of the time dilation. In fact, the magnitude of the GR gravitational time dilation at any point is *identical* to the magnitude of the SR time dilation for a body moving with a speed equal to the escape speed at that point.

So all you need to do to calculate the time dilation at any point in a gravitational field is to plug the escape speed at that point into the Lorentz transform (and when using natural units, c = 1, this is actually just the equation of a unit circle).
MaxwellsDemon
Sep 09, 2010

Rank: 5 / 5 (5)
Lol! He's so annoyed that he even gave me a "1" for the post where I was forced to agree with him!

I consider it a badge of honor to be reviled by a weak mind, my friend ;)
Gawad
Sep 09, 2010

Rank: not rated yet
There's a fascinating relationship between gravitational potential energy, time dilation, and escape speed (aka 'escape velocity,' but that's a misnomer). As the gravitational potential energy reaches its most negative value at the center of a body (where we set the gravitational potential energy to zero at infinity), the escape speed reaches the maximum value, as does the magnitude of the time dilation. In fact, the magnitude of the GR gravitational time dilation at any point is *identical* to the magnitude of the SR time dilation for a body moving with a speed equal to the escape speed at that point.
That's certainly a much more intuitive approach than the equation I posted. Humm...thanks.
ubavontuba
Sep 09, 2010

Rank: not rated yet
Here's a fun and relevant paper about time dilation inside a sphere:

http://arxiv.org/...701084v2

It reminds me of Doctor Who's Tardis...

http://en.wikiped...i/TARDIS

Sing with me now: Oo-ee-oo-oo-oo-ee-oo-oo...
Rank 4.6 /5 (37 votes)
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Hovering not hard if you're top-heavy, researchers find

Top-heavy structures are more likely to maintain their balance while hovering in the air than are those that bear a lower center of gravity, researchers at New York University's Courant Institute of Mathematical Sciences ...

Physics / General Physics

created 1 hour ago | popularity 5 / 5 (1) | comments 1 | with audio podcast

SLAC, Stanford team focuses on high-energy electrons to treat cancer

Accelerator physicists at SLAC and cancer specialists from Stanford are working on a new technology that could dramatically reduce the time needed for cancer radiation treatments. The team ran an initial experiment ...

Physics / General Physics

created 4 hours ago | popularity 5 / 5 (1) | comments 0

Measurements from high-energy collisions lead to better understanding of why meson particles disappear

For several years, physicists at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL), USA, have studied an unusual state of matter called the quark–gluon plasma, which they ...

Physics / General Physics

created 5 hours ago | popularity 5 / 5 (1) | comments 0

Quantum physicist explains $100K offer for proof scaled-up quantum computing is impossible

(PhysOrg.com) -- MIT researcher Scott Aaronson has certainly riled the physics community with his offer this past Friday, of $100,000 to anyone who can prove that scaled-up quantum computing is impossible. ...

Physics / Quantum Physics

created Feb 08, 2012 | popularity 4.1 / 5 (11) | comments 32 | with audio podcast weblog


Employers feel no love for unscrupulous practice of 'service sweethearting'

A new study led by two Florida State University marketing professors finds that some frontline service employees who are rewarded for hikes in customer loyalty and satisfaction also may engage in "service ...

US issues guidelines to avoid heparin contamination

Four years after US drug-maker Baxter International's blood thinner heparin was contaminated in China, causing dozens of deaths, US regulators on Friday issued draft guidelines for safe production.

Expat French get Internet vote for first time

French citizens will for the first time this year be able to vote in a parliamentary election over the Internet, an experiment that could be extended to other elections if successful.

"Twisted Metal" gamers get shot at real gunplay

Fans of "Twisted Metal" will get to welcome a long-awaited sequel of the car-battle videogame with a real-world bang by blasting an ice cream truck to bits with a machine gun.

The power of estrogen -- male snakes attract other males

A new study has shown that boosting the estrogen levels of male garter snakes causes them to secrete the same pheromones that females use to attract suitors, and turned the males into just about the sexiest ...

New error-correcting codes guarantee the fastest possible rate of data transmission

Error-correcting codes are one of the triumphs of the digital age. They’re a way of encoding information so that it can be transmitted across a communication channel — such as an optical fiber o ...