Speed of light

[harry]

G'day rom the land of ozzzzz

I forgot I posted that link before.

I meant to post this one

http://arxiv.org/abs/astro-ph/0605274
Stability of Magnetic Equilibria in Radio Balloons

Authors: Gregory Benford
(Submitted on 10 May 2006 (v1), last revised 19 May 2006 (this version, v2))

Abstract: Current-carrying flows, in the laboratory and in astrophysical jets, can form remarkably stable magnetic structures. Decades of experience shows that such flows often build equilibria that reverse field directions, evolving to an MHD Taylor state, which has remarkable stability properties. We model jets and the magnetic bubbles they build as reversed field pinch equilibria by assuming the driver current to be stiff in the MHD sense. Taking the jet current as rigid and a fixed function of position, we prove a theorem: that the same, simple MHD stability conditions guarantee stability, even after the jet turns off. This means that magnetic structures harboring a massive inventory of magnetic energy can persist long after the building jet current has died away. These may be the relic radio "fossils," "ghost bubbles" or "magnetic balloons" found in clusters. These equilibria under magnetic tension will evolve, retaining the stability properties from that state. The remaining fossil is not a disordered ball of magnetic fields, but a stable structure under tension, able to respond to the slings and arrows of outside forces. Typically their Alfven speeds greatly exceed the cluster sound speed, and so can keep out hot cluster plasmas, leading to x-ray "ghosts." Passing shocks cannot easily destroy them, but can energize and light them up anew at radio frequencies. Bubbles can rise in the hot cluster plasma, perhaps detaching from the parent radio galaxy, yet stable against Rayleigh-Taylor and other modes.

[makc]

The reason for speed of light being fixed is that in Einstein's theory there is a tensor in which all four 4 diagonal elements must sum to zero.

That is not as simple, and not the reason for the speed of light being fixed - it is actually other way around in some way, because the whole theory is built on light speed invariance as a premise, which is simply based on experimental evidence.

[Chris Peterson]

You missed the point of my question. What force would cause the galaxies to fall in towards the voids in the first place? That is, what force is it that this proposed force of yours is opposing? You don't doubt Newton's First Law, do you?

I do not propose galaxies falling towards the voids, as I propose anti-gravity filling the voids .. rather, the voids are compressing the galaxies together into filaments .. galaxies between voids being squeezed.

So I take it you do doubt Newton's First Law? Because you still haven't explained what force would cause galaxies to enter voids in the first place. Without such a force, there's no need for a new force ("antigravity") to keep them out.

On the other hand, a perfectly ordinary force called gravity, which is pretty well understood, is all we need to explain the structure of galaxies into filaments.

[bongman]

http://www.math.columbia.edu/~woit/wordpress/?p=563

This is a book I picked up this week. Very interesting insight on an alternative model for the universe and how it functions (not physicaly but from "creation" to "end") I have only just started said book, but the Ideas stated within have really got me thinking, I'm sure some of you would really enjoy what these two have to say.

[aristarchusinexile]

I read it this past winter, lots of information well presented. It assisted in forming my idea of anti-gravity voids expanding and accounting for Redshift.

[aristarchusinexile]

I've tried to read about LQG, and my brain has the scars to prove it. The only relation between these two that I can fathom is a vague one involving the meaning of the word 'loop'. A coronal loop is plasma following a path of constant force, and the loops in LQG have something to do with 'paths' around nodes in spin networks... I think.

Paths being the common factor .. thanks Qev .. more information adds up to more information. Time being a path?

[aristarchusinexile]

I have yet to see any answer to my question. The closest thing to an answer offered here seems to be that it is the current theory that it was a sigularity in the beginning. I know that, hence the question in the first place. But, besides an inference from regresion, why a sigularity? All that followed the first attempt to answer the question seems to be misguided gibberist about Nietzsche. For the record, I am not a Nietzschian. I just like the name Zarathustra. I am however well versed in his philosophy. I would politely like to request that those here who clearly are not please refrain from posting your ignorance.

I just repeat that there are published theories which say singularities are not necessary.

[Doum]

And i keep saying the theory explain why it was probably a singularity. There is no new force that explain otherwise. So till something new come out, the theory of a singularity is the only one i heard of. I will look at knew one when it get out of mud.

[JimJast]

Hi makc, it is of cource true that speed of light has to be fixed because of relativity and we don't discuss that but only on what value it is fixed and why. The value we get experimentally, but why it has this particular value we have to guess. My guess is the sum of those 4 terms out of which the nature can detrmine c. The similar reasons may exist for other constants of nature. Accidental values of physical variables might determine constants of nature because of certain necessary relations between them. Once I determined in this way G and so I have an impression that if we know proper relations we may determine possibly all constants of nature. We may have a problem when some relations give us different values than others. Then we may invalidate some ot the relations for this reason only. E.g. if we got two different values for c from two different relations. Then we may refine our knowledge of nature. So far we don't know that much to have such pradoxes and so we can have an idea of constants of nature. Maybe in some future all constants of nature disappear and we are able to calculate them like now we might be able to calculate c (if my assumption is true do you think it might?)
-- Jim

[JimJast]

Maybe what gravity is shaping is only part of what exists in space like the meduim that carrys elcetro magnetic waves.

People were looking for meduim that carrys elcetro magnetic waves (called ether) and it turned out that there is no such medium in nature. Einstein's theory of relativity came out from those attempts to find such a medium and since Einstein's theory works now we are sure there is no ether.

Possibly there is more to space than what light interacts with and maybe gravity does not affect that type of space. I have gut feelings that there is more to gravity being a distortion or shaping of space time. [...] We need to know more about gravity.

For the time being we don't need to know more since every phenomenon pertaining to gravity got explained about 1915 and people just have to finally accept that.

[Chris Peterson]

Hi makc, it is of cource true that speed of light has to be fixed because of relativity and we don't discuss that but only on what value it is fixed and why. The value we get experimentally, but why it has this particular value we have to guess. My guess is the sum of those 4 terms out of which the nature can detrmine c. The similar reasons may exist for other constants of nature. Accidental values of physical variables might determine constants of nature because of certain necessary relations between them. Once I determined in this way G and so I have an impression that if we know proper relations we may determine possibly all constants of nature. We may have a problem when some relations give us different values than others. Then we may invalidate some ot the relations for this reason only. E.g. if we got two different values for c from two different relations. Then we may refine our knowledge of nature. So far we don't know that much to have such pradoxes and so we can have an idea of constants of nature. Maybe in some future all constants of nature disappear and we are able to calculate them like now we might be able to calculate c (if my assumption is true :) do you think it might?)

In my opinion, this is circular reasoning. There doesn't need to be any "why" as to the values of physical constants. They are what nature made them, and understandable physical behaviors follow. Calculating values for physical constants from other terms is either circular, or demonstrates that the constant isn't fundamental (which could happen with c, of course, if a unified theory is developed).

BTW, I'd be cautious talking about the speed of light. It isn't a constant at all. c is the constant (a different thing), and it only happens that the speed of light equals c under specific conditions. Actually measuring the speed of light experimentally is probably not the most accurate way of determining C.

[aristarchusinexile]

People were looking for meduim that carrys elcetro magnetic waves (called ether) and it turned out that there is no such medium in nature. Einstein's theory of relativity came out from those attempts to find such a medium and since Einstein's theory works now we are sure there is no ether.

Dark Matter has been called the new aether.

[aristarchusinexile]

And i keep saying the theory explain why it was probably a singularity. There is no new force that explain otherwise. So till something new come out, the theory of a singularity is the only one i heard of. I will look at knew one when it get out of mud.

It's obvious to me that some of us on the forum and probably all of us at one time or another do not read all the relevant posts on a topic .. so I have sent Doum a PM with this link http://physicsworld.com/cws/article/print/3428

[bystander]

Hi makc, it is of cource true that speed of light has to be fixed because of relativity and we don't discuss that but only on what value it is fixed and why. The value we get experimentally, but why it has this particular value we have to guess. My guess is the sum of those 4 terms out of which the nature can detrmine c. The similar reasons may exist for other constants of nature. Accidental values of physical variables might determine constants of nature because of certain necessary relations between them. Once I determined in this way G and so I have an impression that if we know proper relations we may determine possibly all constants of nature. We may have a problem when some relations give us different values than others. Then we may invalidate some ot the relations for this reason only. E.g. if we got two different values for c from two different relations. Then we may refine our knowledge of nature. So far we don't know that much to have such pradoxes and so we can have an idea of constants of nature. Maybe in some future all constants of nature disappear and we are able to calculate them like now we might be able to calculate c (if my assumption is true do you think it might?)-- Jim

Simple algebra should tell you it's the constants that determine the value of the variables, not the other way araound. Did you say you were a mathmatician

[makc]

note that numeric values of constants actually follow from our arbitrary selected measure units.

for example, we select a "second" to be a unit of time. then, we select a "meter" to be a unit of length. but, since meter is the distance travelled by light in free space in 1⁄299,792,458 of a second by definition, it follows that speed of light (c) is 299 792 458 meters per second. we end up with this cryptic number not because it has some special significance in nature (like π or e), but because long time ago French Academy of Sciences created random metal bar with the length of approximately 1⁄10,000,000 of the distance from the equator to the north pole through Paris.

similary, if you select a "light second" to be a unit of length instead of meter, you would have numeric value of c equal to 1.0 (much nicer number, imho). however, light second is not convenient to humans because we are much smaller than that.

[makc]

you know, they would find it long time ago already, but it's just too f***kin dark and this thread is like from half year ago.

[bystander]

note that numeric values of constants actually follow from our arbitrary selected measure units.

True, but c would be a constant, regardless of the units of time and distance.

[harry]

G'day from the land of ozzzzzz

How can TIME be a path?

If it is a path, can it be followed?

[JimJast]

bystander wrote:
Did you say you were a mathmatician

No. I've been working in figurative sculpture (http://geocities.com/jim_jastrzebski/art/sculpt.htm).

makc wrote:
[...] similary, if you select a "light second" to be a unit of length instead of meter, you would have numeric value of c equal to 1.0 (much nicer number, imho). however, light second is not convenient to humans because we are much smaller than that.

But we are just right for "light nanosecond" which we are (almost) using but calling it for some reason a "foot".

BTW, how do I properly quote and how can I edit my stuff?

[Chris Peterson]

Dark Matter has been called the new aether.

Not by anybody who understands the nature of science! The two examples couldn't be more different. Aether was proposed, without any need or supporting observation, for what would best be described as a philosophical problem: they had a scientifically incorrect belief system they couldn't work around, that a medium was required to carry something. Experiments demonstrated that the aether didn't exist, and better theory eliminated the need for it.

Dark matter wasn't proposed in the absence of observation; just the opposite. The effects of dark matter were first observed, and the presence of a form of matter that interacts gravitationally but not electromagnetically was suggested as the best fit. This is precisely the same way that most subatomic particles, including protons, neutrons, and electrons were proposed. None of these types of matter were directly observable at all, only inferred from their indirect effects.

[Doum]

aristarchusinexile,

You are right i didnt read that link. And i dont always take time to look my PM neither. So, that "Loop quantum gravity" look interesting . I will try to understand it better. As for singularity, at the beginning the universe was smaller then the planck lenght (1.616 × 10-35 meters) in diameter so we cant say a thing about it cause we cant measure it (It's too small). That why the singularity is advance cause we dont know what the universe look like before the planck lenght. So the question i see is what can stop a singularity from happening at that scale since we dont have any information about it?
The "Loop quantum gravity" seem to be able to go smaller then the planck lenght and give us an answer to what was before the planck lenght. But since we cant measure smaller then the planck lenght it may remain a speculation (or a theory). Same for the singularity.

In reality, we cant say for now what the universe was before the planck lenght (1.616 × 10-35 meters) or should i say before the planck time (the earliest period of time in the history of the universe, from zero to approximately 10−43 seconds).

What still remain the same is that after the planck time (10−43 seconds up to now) the universe did start as a big bang.

Here is a text i extract from a link about Planck epoch.

"If quantum effects are ignored, the universe starts from a singularity with an infinite density. This conclusion could change when quantum gravity is taken into account. String theory and Loop quantum gravity are leading candidates for a theory of unification, which have yielded meaningful insights already, but work in Noncommutative geometry and other fields also holds promise for our understanding of the very beginning."

here is the link: http://en.wikipedia.org/wiki/Planck_epoch

Those theories are interesting to watch evolve. It may get out of mud fast. Or not.

Another question i have. Should anything smaller then the planck lenght be call a singularity for now. Since we cant measure anything smaller then that. That way we avoid those words (infinitely small and infinitely dense) that are annoying. Tho having the univers in a 1.616 × 10-35 meters diameter is near infinitely small and infinitely dense. A singularity may be.

[aristarchusinexile]

Duom,

Read Pascual Jordan. "A star could be made out of nothing at all, because at the point of zero volume its negative gravitational energy would precisely cancel out its positive mass energy."

This statement is reported to have brought Einstein, who was walking, to a complete halt in the middle of a busy street. Jordan was a contemporary of Einstein, one of the 'founders' of quantum mechanics. He is not well known because he was a member of the Nazi Party, but why is that a problem when we have all heard of Wherner Von Braun?

[bystander]

BTW, how do I properly quote and how can I edit my stuff?

Use the quote and edit buttons. To attribute a quote, use quote="name" inside [], Make sure you close with [/quote].

[aristarchusinexile]

G'day from the land of ozzzzzz

How can TIME be a path?

If it is a path, can it be followed?

Predestination is a long-debated topic. It seems to me it is certain that there are certain events already fixed and waiting our arrival on the 'path of time'. I've read in reputable publications, books written by PHD Physicists, that time can be traveled forward and back, that the apparatus for doing so simply can't at this time be built and powered .. if so, there must be a path of time. I think perhaps, concerning jets, that the path of time is coiled inside the Black Hole, and its release is part of the power that drives the jets millions of light years long. Of course, I don't have math to support the idea .. just IMOPO.

[The Code]

Is our universe, with its big bang, and our 13.7 billion year history , the final death of a black hole/white hole, that big, our universe is but a mere speck inside? could i get some views on this?
http://math.ucr.edu/home/baez/physics/R ... verse.html

when they get the gravitational telescope i feel our eyes, will for the first time, open.
thx
mark