Redshift z

[snoopy]

Our Solar System is not in the perimeter of our galaxy.

It is supposed to be approximately 2/3's of the way from the central sourse in the Constellation of Sagittarius (spelling(?).

 

Mike C

 

Our solar system is in the perimeter of our galaxy in what is called the arm of Orion.

 

Constellations are groups of stars used by astronomers many for historical reasons and comprise other galaxies ie they do not indicate our position in our galaxy.

[PhysBang]

Our solar system is in the perimeter of our galaxy in what is called the arm of Orion.

 

Constellations are groups of stars used by astronomers many for historical reasons and comprise other galaxies ie they do not indicate our position in our galaxy.

Nope, sorry.

 

It is quite common to use traditional constellations to indicate direction, as these constellations change their form and position very slowly. The centre of the Milky Way is in the direction of Sagittarius and we are not on the perimeter of the galaxy.

[Mike C]

I'd bet, if our galaxy made a magnetic field strong enough to affect... let's say the Andromeda galaxy (like dark matter)... my compass would dance around like a french harlot

 

 

I do not understand why you bring in the magnetic fields into this discussion?

 

The 'dark matter' I spoke of was the separated electric charges trying to recouple to form the HA again.

It is the electric force that is causing this dark matter enhancement of gravity.

 

The Andromeda Galaxy is approaching our galaxy at about 60 Kms per second.

This is because of gravity, not the magnetic fields.

 

My opinion is that they are not going to collide because they are moving off line in eliptical orbits.

 

Phys

Thanks for straightening Snoopy out.

 

Mike C

[modest]

Nope, sorry.

 

It is quite common to use traditional constellations to indicate direction, as these constellations change their form and position very slowly.

Snoop is right, not when talking about earth's position in the galaxy.

 

The centre of the Milky Way is in the direction of Sagittarius and we are not on the perimeter of the galaxy.

"on the perimeter" as you say and "in the perimeter" as snoopy and Mike C said are two rather different things. Once again snoopy is right, we are in the perimeter.

 

Our Solar System is not in the perimeter of our galaxy.

I assumed Mike C meant 'interior' or some other word that might salvage this sentence.

 

It is supposed to be approximately 2/3's of the way from the central sourse in the Constellation of Sagittarius (spelling(?).

Here I assumed he was referring to the center of the galaxy when he said Sagittarius. This, however, is a big stretch and requires altering the rules of english substantially.

 

In any case, snoopy is right to interject as these two sentences when put together are ripe with error.

 

-modest

[modest]

It is the electric force that is causing this dark matter enhancement of gravity...

 

Mike C

 

If it's OK, I have answered you here:

 

Do we feel forces of Dark Matter

 

-modest

[Mike C]

If it's OK, I have answered you here:

 

Do we feel forces of Dark Matter

 

-modest

 

I accessed that URL but got no response.

What Happened?

 

Mike C

 

Oops, I copied the url and pasted instead of the lower access .

[peter]

Just for the sake of this discussion, lets say that the universe has an edge and that we are located on that edge. If by some miracle we happen to look at the center of the universe, wouldn't the light coming toward us be red shifted because of the gravity well it was climbing out of?

What happens if we are located at the edge of the universe and shoot light beam outward, does the light go outside of the universe?

[CraigD]

What happens if we are located at the edge of the universe and shoot light beam outward, does the light go outside of the universe?

No. The “edge of the universe” would simply expand to encompass the light.

 

This is an imaginary thought exercise, of course, because by the same reasoning, the edge of the universe would already have expanded to encompass light from other sources before we could reach it. “We” having mass, can never have traveled quite as fast as light, and hence never reach the ever-expanding “edge of the universe”

 

The above assumes a simplistic, 3-dimensional Euclidean definition of space, and classical view of matter and light, the latter of which, at least, doesn’t appear to be the actual case. It’s possible that the former isn’t, either – for example, space may have a spherical geometry, wrapping back around itself to have no edge.

 

In an interpreted quantum field view of mater and light, even in simple E3 space, the idea of the “edge of the universe”, even one expanding at lightspeed, isn’t very meaningful, as there is a small but non-zero probability of a specific particle, massless or otherwise, existing at any point and time outside such a boundary. Interpretations of quantum physics open up a whole new realm of “what if” thought exercises.

[peter]

No. The “edge of the universe” would simply expand to encompass the light.

So it can conclude that the universe will expand forever.

 

for example, space may have a spherical geometry, wrapping back around itself to have no edge.

.......

 

Interpretations of quantum physics open up a whole new realm of “what if” thought exercises.

 

This is true. There are a lot of "what if"s being asked out there and a lot of "may"s being answered, they are all imaginations.

[freeztar]

they are all imaginations.

 

I would say that they are all potential paths to progress.

[modest]

they are all imaginations.

I would say that they are all potential paths to progress.

 

Indeed. While I think peter meant his statement to deride a bounded model of the universe, his statement itself does not mean or imply anything bad.

 

This is true. There are a lot of "what if"s being asked out there and a lot of "may"s being answered, they are all imaginations.

 

"What if" has its place in scientific investigation. What if the earth is spherical? What if a person in free fall is in an inertial reference frame? Nothing wrong with "what if"

 

"may be" is often better than "must be" as an answer. 'Must be' attempts to close the door on a subject, but we know there is always more investigating to do. 'May be' is a hypothesis and the scientific method has nothing against it.

 

"imaginations" are also a wonderful thing to have in science and a key ingredient in the mental workings of the best scientists.

 

So, peter's statement "may" have been intended as scornful of modern cosmology but "what if" it really isn't?

 

-modest

[coldcreation]

"may be" is often better than "must be" as an answer. 'Must be' attempts to close the door on a subject, but we know there is always more investigating to do. 'May be' is a hypothesis and the scientific method has nothing against it.

 

"imaginations" are also a wonderful thing to have in science and a key ingredient in the mental workings of the best scientists.

 

So, peter's statement "may" have been intended as scornful of modern cosmology but "what if" it really isn't?

 

-modest

 

Good points modest...

 

 

Now, back to redshift z.

 

The two central points emerge from this thread: Ever since the appearance of modern cosmology, with its expanding universe concept, another interpretation was available and viable. It was discarded on insufficient grounds.

 

Notably, there are two explanations (or interpretations) for cosmological redshift—both of which embody essential aspects of the gravitational interaction. One is the well known standard interpretation: a change in the scale factor to the metric, i.e., expansion of space, where the photons are degraded or diluted in energy due to the stretching of the wavelength in the travel time. The other is: wavelengths throughout the entire spectrum are redshifted as they pass through a curved spacetime manifold in a non-expanding universe. The latter case is based on the imfamous de Sitter metric circa 1917.

 

Secondly, it should become apparent that the insufficiencies, shortcomings and drawbacks pertaining to the dynamic features of both interpretations exemplify the need to explore a more powerful and increasingly well-defined interpretation of what we call the essence of the physical universe and its evolution in time, based (at least) on redshift z.

 

There are, indeed, overwhelming arguments showing that the standard model cannot mimic all the current observations.

 

It can be demonstrated that non-expanding general relativistic spacetimes reproduce identical cosmological observations as the currently favored theory (lambda-CDM). The de Sitter universe has the advantage of alleviating the tribulations (such as dark energy and CDM) and offers solutions to numerous quantum and astronomical problems that face us today.

 

An amazing amount of literature is available on this problem: testimony to its importance. It will undoubtedly demand more attention as this story unfolds. See, for example, Kerszberg, P. 1989, The Invented Universe, The Einstein-De Sitter Controversy (1916-17) and the Rise of Relativistic Cosmology.

 

We are evolving toward a world model that relates strongly to the aesthetic of the late 1900s through the early 1920s, those drafted by Millikan, MacMillan and Nernst. The unusual juxtaposition of principles and theory in such worldviews suggests an allegorical content that distinguishes these ideas from mere decoration. Yet simultaneously, it is the same content that is strongly reminiscent of cosmology at that time, before the great schism, before the breach of war and that engaged the viewer’s imagination to a degree to which many later works did not.

 

I think I know what Peter is attempting to express. Steer through the narrow passage between the crumbling laws and you will enter a fairy-tail world seen through the eyes of modern cosmology. Then, when you suddenly immerse into the bright bustle of the big bang (near t = 0), it is impossible not to wonder if it had been designed to thwart certainty, the steps never quite long enough to get both feet safely planted on the same level. The visual feast, an oasis of high-energy elegance, can only be acted out with the vivid imagination.

 

 

And yet, and yet.

 

 

 

 

CC

[PhysBang]

Sorry, which de Sitter universe is this? Is this the one in which de Sitter used the cosmological constant and incorrectly thought was static.

 

The one published in De Sitter, W. (1917) “On the Curvature of Space,” Proceedings of the Section of Sciences, Koninklijke Akademie van Wetenschappen te Amsterdam 20: 229–242? The one that Felix Klein's extension of the metric showed that the model wasn't static?

 

The one with a matter-free universe? The one that has the same dark energy as the current standard cosmological model?

[modest]

The one published in De Sitter, W. (1917) “On the Curvature of Space,” Proceedings of the Section of Sciences, Koninklijke Akademie van Wetenschappen te Amsterdam 20: 229–242? The one that Felix Klein's extension of the metric showed that the model wasn't static?

 

In his next letter on the topic (of June 16, 1918), Klein was more direct. As in his earlier letter, he wrote the transformation from the pseudo-Cartesian coordinates of the De Sitter hyper-hyperboloid in 4+1-dimensional Minkowski space-time to the coordinates used to write the solution in static form. This shows, Klein explicitly pointed out, that the singularity at the equator has to be an artifact of the static coordinates…

 

The singular behavior of the temporal component of the metric, which vanishes on the equator, reflects the fact that in the immediate vicinity of the equator, points infinitesimally close in proper time will be infinitely far removed from one another in coordinate time.

 

This time Klein’s point was not lost on Einstein. He immediately wrote back to Klein to tell him that he now accepted that the De Sitter solution is matter-free, fully regular, and homogeneous. This does not mean, however, that Einstein also accepted the De Sitter solution as a possible cosmological model. He still held that any acceptable cosmological model would have to be static. Klein had shown that in the static form of the De Sitter solution, the time coordinate breaks down on the equator. In Weyl’s hybrid static solution, on the other hand, which coincides with the De Sitter solution outside a zone of matter around the equator, the time coordinate is well defined everywhere. Only this hybrid solution, therefore, provides an acceptable static cosmological model. Einstein thus had to accept that the De Sitter solution forms a counterexample to Mach’s principle as he had formulated it in March 1918 and that his critical note on the De Sitter solution stood in need of correction. His modified field equations did allow fully regular matter-free solutions. He could still hold, however, that they did not allow globally static fully regular matter-free solutions. From a letter from Weyl to Klein of February 1919, written after consultation with Einstein, it can be inferred that this is the position to which Einstein retreated in response to Klein’s analysis of the De Sitter solution.

 

-The Einstein-De Sitter Debate

 

Refers to "Weyl’s hybrid static solution" which I think refers to a paper he wrote in 1919 called "A New Extension of the Theory of Relativity". Can anyone find it or a discussion of it?

[peter]

I have absolutely no intent to “scorn’’ or “deride” the modern cosmology, please do not misunderstand my words, however, I respect your right for imagination.

Compare to other science subjects, cosmology is the most difficult and wonderful science subject. The cosmology is specially full of curiosity and imaginations because you can not touch, feel and measure the far away and long ago, cosmologists are working hard to find the truth with every possible clue. My self is full of imaginations. As Modest said “"imaginations" are also a wonderful thing to have in science and a key ingredient in the mental workings of the best scientists”, without imaginations, there is no progress in science and our society.

I remembered that my kid asked “what did the universe look like before the Big Bang?” “where did that tiny, extremely hot and dense spot come from?” “ anything else beyond that spot?” I believe that those questions have been asked over and over since the beginning of the Big Bang model and they are beyond the scope that current laws can describe. Anyone has a good answer for them? You may say “ I don’t know” or come up with imaginations, a fairy –tale world.

[modest]

I have absolutely no intent to “scorn’’ or “deride” the modern cosmology, please do not misunderstand my words, however, I respect your right for imagination.

Compare to other science subjects, cosmology is the most difficult and wonderful science subject. The cosmology is specially full of curiosity and imaginations because you can not touch, feel and measure the far away and long ago, cosmologists are working hard to find the truth with every possible clue. My self is full of imaginations. As Modest said “"imaginations" are also a wonderful thing to have in science and a key ingredient in the mental workings of the best scientists”, without imaginations, there is no progress in science and our society.

I remembered that my kid asked “what did the universe look like before the Big Bang?” “where did that tiny, extremely hot and dense spot come from?” “ anything else beyond that spot?” I believe that those questions have been asked over and over since the beginning of the Big Bang model and they are beyond the scope that current laws can describe. Anyone has a good answer for them? You may say “ I don’t know” or come up with imaginations, a fairy –tale world.

 

Well said, I apologize if I misunderstood. Many people share you sentiment exactly.

 

-modest

[coldcreation]

Sorry, which de Sitter universe is this? Is this the one in which de Sitter used the cosmological constant and incorrectly thought was static.

 

When you write de Sitter "incorrectly thought it was static" it reminds me of a time, not too long ago (before 1998), when it could be read in just about every text book that Einstein had "incorrectly" introduced lambda into the field equations ("had he not done so, he would have predicted the expanding universe").

 

Now lambda is back again. I wish Einstein were here today (he deserves another Nobel). His greatest blunder turned out to be one of his greatest discoveries.

 

On the score of de Sitter, it turns out he was correct as well.

 

There are in fact three static solutions to the field equations: Einstein's (1917), one with a Minkowski spacetime (four components to the metric tensor are 1,1,1,-1). The third is a de Sitter solution (1916, Mon. Not. RAS 76, 699), (1916, Mon. Not. RAS 77, 155) and (1917, Mon. Not. RAS 78, 3). Note: the latter model has redshift increasing with distance (the de Sitter effect) as well as a time dilation factor.

 

Tolman (1929) proved that these three (and only three) models were in fact static. (Tolman, R.C., 1929, Proc. Nat. Acad. Sci. 15, 297).

 

(See also, Sandage, A.R. 1993, The Deep Universe, Saas-Fee Advanced Course 23, Lecture Notes 1993, Swiss Society for Astrophysics and Astronomy, pp 97 - 126).

 

 

The one published in De Sitter, W. (1917) “On the Curvature of Space,” Proceedings of the Section of Sciences, Koninklijke Akademie van Wetenschappen te Amsterdam 20: 229–242? The one that Felix Klein's extension of the metric showed that the model wasn't static?

 

Perhaps...

 

 

The one with a matter-free universe? The one that has the same dark energy as the current standard cosmological model?

 

Willem de Sitter, who might be recognized, after Einstein, as the ‘father’ of general relativistic cosmology, approached pictorial space in an obviously relativistic way, and, even if he veered towards a synthetic shaping, the evidence indicates that he continued to work fundamentally in a natural way (or at least thought he did), working as he saw it from the manipulation of formal relations towards nature, not from the starting-point in nature. His range of world models was strictly limited and his ways of forming them were flexible enough for rhyming (synthetic and nature, art and science) to be a factor -- his empty world model is an example.

 

Before seriously attempting to answer your palpable questions, PhysBang, the one case of a relativist who did approach both gravitation and a complementary belief in the revelatory power of the cosmological term should be mentioned: Willem de Sitter was able to demonstrate that the geometrical attribute of pure space (a completely empty universe) is a hypersphere -- time is no longer independent of space, but depends on distance. The time and space that separates two points is curved (a geodesic), corresponding to a hyperbolic spacetime description.

 

If such purity of conception was indeed his aim between 1917 and 1932, it is difficult to believe that he ever altogether achieved it. Only in a superficial sense can de Sitter’s cosmology be called compromising, and if behind it there lay any true spirit of compromise, it had not come from the pressure applied by the enemies of relativity. For the fact is that his world-views had become successful, the concepts he had sold, and the criticism was generally positive, even for his empty universe model (a true masterpiece), though whatever element of compromise there was does seem to have been a direct response to the pressures of the time. (The most important of these came from Einstein himself). An underlying impression of de Sitter’s poetic license is there to be sensed beneath the luxuriant surface of Kosmos, 1932.

 

 

 

R.I.P.

 

 

 

 

 

CC