Starship Asterisk*

aristarchusinexile wrote:And yet .. the mysterious 'replusive force' which some say is driving the universe apart, if it is a force, must be energy, and seems to be in the process of constant creation.

Scientists don't believe in everything that people say, especially when they don't have any theory to explain the thing. Then they ignore what people say and most of the time they are right. Usually it turns out that people saw some illusion that they took for real. It already happened so with "Newtonian gravitational attraction" (in which even Newton, being a smart gay, didn't believe, since, the same as Einstein, he didn't believe in action at a distance and both were right). It is most likely the same with this "repulsive" stuff "which some say is driving the universe apart".

The only theory applicalble here is Einstein's gravitation and in Einstein's theory gravitational force is neither repulsive nor attractive. It is an inertial force coming from the gravitational time dilation and from the curvature of space. The inertial force can't be "repulsive" and can't "drive the universe appart". So there is no reason for panic

JimJast wrote:Scientists don't believe in everything that people say, especially when they don't have any theory to explain the thing. Then they ignore what people say and most of the time they are right. Usually it turns out that people saw some illusion that they took for real. It already happened so with "Newtonian gravitational attraction" (in which even Newton, being a smart gay, didn't believe, since, the same as Einstein, he didn't believe in action at a distance and both were right). It is most likely the same with this "repulsive" stuff "which some say is driving the universe apart".

The only theory applicalble here is Einstein's gravitation and in Einstein's theory gravitational force is neither repulsive nor attractive. It is an inertial force coming from the gravitational time dilation and from the curvature of space. The inertial force can't be "repulsive" and can't "drive the universe appart". So there is no reason for panic

See today's APOD: 2009 March 29 - Signals of a Strange Universe. Dark energy is that "repulsive" stuff to which you are referring.

bystander wrote:Dark energy is that "repulsive" stuff to which you are referring.

Neither "Dark energy" nor "repulsive gravitation" are ideas from science yet. They are hypothetical things proposed by laymen (if you read carefully the wikipedia's description that you quoted you might notice it).

Neither "dark energy" nor "repulsive gravitation" fit any existing theory of gravitation (at least not Einstein's, which is rather well established theory explaining gravitation merely with curvatures of spacetime) and so for the time being "dark energy" and "repulsive gravitation" are stories from different science.

I'm not sure if discussing SF is forbidden in this forum but just to be on the safe side, I wouldn't discuss it here. The main problem is that you can't prove the existence of neither "dark energy" nor "repulsive gravitation" and we are supposed to discuss only things that exist objectively and they can be observed. There might exist other fora dedicated to such things like "repulsive gravitation" and "dark energy".

JimJast wrote:Neither "Dark energy" nor "repulsive gravitation" are ideas from science yet. They are hypothetical things proposed by laymen (if you read carefully the wikipedia's description that you quoted you might notice it).

Neither "dark energy" nor "repulsive gravitation" fit any existing theory of gravitation (at least not Einstein's, which is rather well established theory explaining gravitation merely with curvatures of spacetime) and so for the time being "dark energy" and "repulsive gravitation" are stories from different science.

I'm not sure if discussing SF is forbidden in this forum but just to be on the safe side, I wouldn't discuss it here. The main problem is that you can't prove the existence of neither "dark energy" nor "repulsive gravitation" and we are supposed to discuss only things that exist objectively and they can be observed. There might exist other fora dedicated to such things like "repulsive gravitation" and "dark energy".

Yes, dark energy is hypothetical (proposed by cosmologist not laymen), but it is the prevailing theory among mainstream cosmologists. Repulsive gravitation (aristarchusinexile's musings aside) is a misnomer, as it has nothing at all to do with gravity, but rather (albeit misleading) is a term referring to the accelerating expansion. Maybe you ought to reread the wiki article.

A book I must read - 'Reinventing Gravity: A Physicist Goes Beyond Einstein' .. by John W. Moffat, a physicist at the Perimeter Institute for Theoretical Physics in Waterloo, Canada. (Those darned Canadians, eh!)

"Moffat says that both Newton and Einstein were wrong, and that Newton's gravitational constant is not constant across distances as large as galaxies and galaxy clusters. Scientists haven't been able to find dark matter because it doesn't exist: MOG values help account for rates of galaxy rotation. Perhaps more revolutionary is Moffat's claim that black holes don't exist either. His theory predicts a "grey star," a massive object with many but not all of the properties of a black hole. Moffat's theory thus far has withstood many objections. If MOG stands the test of time, Moffat will have created a paradigm shift not seen since Newton. Illus. (Oct.)" From Publisher's Weekly

From the publisher's promo - "The cap­stone to a storybook career—one that began with a correspondence with Einstein and a conversation with Niels Bohr—Moffat's modified gravity theory, or MOG, can model the movements of the universe without recourse to dark matter, and his work chal­lenging the constancy of the speed of light raises a stark challenge to the usual models of the first half-million years of the universe's existence. This bold new work, presenting the entirety of Moffat's hypothesis to a general readership for the first time, promises to overturn everything we thought we knew about the origins and evolution of the universe."

According to what I've read so far, Moffat ("In 1958, he became the only Trinity College, Cambridge student to be awarded a Ph.D. without a first degree. He was supervised by Fred Hoyle and Abdus Salam.") from Wikipedia )says there is no need for Black Holes or Dark Matter.

JimJast wrote:Neither "Dark energy" nor "repulsive gravitation" are ideas from science yet. They are hypothetical things proposed by laymen (if you read carefully the wikipedia's description that you quoted you might notice it).

Nonsense. Dark energy is hypothesized to explain an observed behavior of the Universe, is widely accepted by scientists, and fits in well with existing theory and observation. It meets every standard for a robust scientific theory. I don't know what "repulsive gravitation" even is, unless you're referring to a component of one of the modified gravity theories- some of which meet the standards of scientific theory, but none of which are accepted by many scientists as likely.

Neither "dark energy" nor "repulsive gravitation" fit any existing theory of gravitation (at least not Einstein's, which is rather well established theory explaining gravitation merely with curvatures of spacetime) and so for the time being "dark energy" and "repulsive gravitation" are stories from different science.

Dark energy's role in the early formation of the Universe fits in well with GR. However, there's no requirement that the two "fit" as such, only that neither provides some sort of contradiction of the other. So far anyway, they don't.

I'm not sure if discussing SF is forbidden in this forum but just to be on the safe side, I wouldn't discuss it here. The main problem is that you can't prove the existence of neither "dark energy" nor "repulsive gravitation" and we are supposed to discuss only things that exist objectively and they can be observed.

You can't prove the existence of anything. In fact, everything we take as real is nothing more than a theoretical explanation based on observation. This includes things like EM, gravity, and matter. It also includes dark energy, which is objectively observed, although the observation remains more open to alternate explanations than some other observations.

JimJast wrote:

aristarchusinexile wrote:And yet .. the mysterious 'replusive force' which some say is driving the universe apart, if it is a force, must be energy, and seems to be in the process of constant creation.

Scientists don't believe in everything that people say, especially when they don't have any theory to explain the thing. Then they ignore what people say and most of the time they are right. Usually it turns out that people saw some illusion that they took for real. It already happened so with "Newtonian gravitational attraction" (in which even Newton, being a smart gay, didn't believe, since, the same as Einstein, he didn't believe in action at a distance and both were right). It is most likely the same with this "repulsive" stuff "which some say is driving the universe apart".

The only theory applicalble here is Einstein's gravitation and in Einstein's theory gravitational force is neither repulsive nor attractive. It is an inertial force coming from the gravitational time dilation and from the curvature of space. The inertial force can't be "repulsive" and can't "drive the universe appart". So there is no reason for panic

Suggested reading: MOG - 'Reinventing Gravity: A Physicist Goes Beyond Einstein' - by John W. Moffat - no singularity needed, no black holes, no dark matter. Collins publisher. Excerpts on Google.

JimJast wrote:I'm not sure if discussing SF is forbidden in this forum but just to be on the safe side, I wouldn't discuss it here. The main problem is that you can't prove the existence of neither "dark energy" nor "repulsive gravitation" and we are supposed to discuss only things that exist objectively and they can be observed. There might exist other fora dedicated to such things like "repulsive gravitation" and "dark energy".

Heavier than air flying machines, men on the moon, a spherical planet earth - all were considered not just science fiction, but fantasy too fantastic to ever be considered possible.

Moffat's Modified Gravity Theory (MOG), is the latest version of his Nonsymmetric Gravitational Theory (NGT). Bekenstein produced a competing relativistic version of Migrom's Modified Newtonian Dynamics (MOND) called Tensor-Vector-Scalar Gravity (TeVeS). To differentiate his work from Bekenstein, Moffat called his version Metric-Skew-Tensor Gravity (MSTG). He later proposed a simplified version of MSTG called Scalar-Tensor-Vector Gravity (STVG). Both STVG and TeVeS claim to be based on Einstein's General Relativity and his search for a Unified Field Theory. Both theories compete with the Lambda Cold Dark Matter (ΛCDM) model of the BBT, the current prevailing model of the universe, and claim to do away with the need for dark matter and dark energy. However, both have problems of their own, such as the need for a variable speed of light (variable over time) and other inconstant physical constants.

aristarchusinexile wrote:Suggested reading: MOG - 'Reinventing Gravity: A Physicist Goes Beyond Einstein' - by John W. Moffat - no singularity needed, no black holes, no dark matter. Collins publisher. Excerpts on Google.

Direct further discussion on MOG to here: http://asterisk.apod.com/vie ... =8&t=16718

bystander wrote:Moffat's Modified Gravity Theory (MOG), is the latest version of his Nonsymmetric Gravitational Theory (NGT). Bekenstein produced a competing relativistic version of Migrom's Modified Newtonian Dynamics (MOND) called Tensor-Vector-Scalar Gravity (TeVeS). To differentiate his work from Bekenstein, Moffat called his version Metric-Skew-Tensor Gravity (MSTG). He later proposed a simplified version of MSTG called Scalar-Tensor-Vector Gravity (STVG). Both STVG and TeVeS claim to be based on Einstein's General Relativity and his search for a Unified Field Theory. Both theories compete with the Lambda Cold Dark Matter (ΛCDM) model of the BBT, the current prevailing model of the universe, and claim to do away with the need for dark matter and dark energy. However, both have problems of their own, such as the need for a variable speed of light (variable over time) and other inconstant physical constants.

Excellent post, Bystander. Much appreciated. Another stimulus in Moffat's idea, if what I have read is correct, is the non-need for singularity.

aristarchusinexile wrote:'Reinventing Gravity: A Physicist Goes Beyond Einstein' - by John W. Moffat

In 1950 Einstein said that metric tensor of spacetime must be non symmetric. Apparently he finally noticed the contradiction betwen symmetric metric tensor of spacetime and the principle of conservation of energy (symmetric metric tensor requires constant creation of energy). The Big Bang cosmology is based on symmetric metric tensor of spacetime so it not only contradicts Einstein's gravitation but also the conservation of energy. As such it can't be a true theory. Regardless how many people support it and how many observations agree with it. Contradicting one valid principle disqualifies it. All religions propose theories cosistent with observations and they have millions of supporters and yet many scientists doubt them only because they violate some valid principles.

Conclusion is that if the contemporary cosmology is based on some wrong assumptions (like constant creation of energy), it may be also totally wrong, and if Einstein was right in everything, then his cosmology might be right as well. In this case the universe might be stationary. We just need to explain all those things that creation of energy explains so neatly. Astronomers might be doing right thing checking all observations again against Einstein's assumptions that were neglected for a log time and so, not so many astronomers had an opportunity to check Einstein's theory against observations. I wouldn't be surprised if it happened as Feynman once said: when there was a difference of opinion between Einstein and others nature always took side of Einstein's.

here he goes again. man, I would love to see that non-symmetric thing math done correctly; that's really all you have to do to get people listening.

Jim Jast - I find it hard to believe but you're beginning to make even me look at you as an odd kind of character. Why don't you post the math?

aristarchusinexile wrote:Jim Jast - I find it hard to believe but you're beginning to make even me look at you as an odd kind of character. Why don't you post the math?

It is not allowed in this forum to publish things that weren't published in a scientific journal yet. The proof that "Einstein's universe" (a static one) has the Hubble constant the same as our universe was not published in a scientific journal yet. When I sent it to "Phys. Rev. Lett." and it passed through the referees (without identifying any formal problems) the editors declined to publish it because of low interest of the subject to their readers (as I derived everything from the first principles only, which they think wouldn't be interesting to the readers).

makc wrote:here he goes again. man, I would love to see that non-symmetric thing math done correctly; that's really all you have to do to get people listening.

makc, Einstein said already in 1950 that metric can't be symmetric (obvious to physicists, just common sense, not to mathematicians though) and they didn't listen. They (Misner, Thorne, and Wheeler in their 1973 Bible "Gravitation") said the metric is symmetric. I sent one (non symmetric) to "Phys. Rev. Lett." and they said, "it won't interest our readers". Why don't you write a non symmetric metric yourself and see if ou get them listening? And why would they? Except a few retired physicists nobody gives a damn about the universe. Here we tend to think that it is an important thing since we are interested in it. But even here there is more moderators than regular guys interested in the discussion (and one of them even a regular nut case ). If not for the moderators the discussion would die for lack of interest.

So editors of "Phys. Rev. Lett." were right: no one in the real world gives a damn whether the universe is expanding or not. Most likely the universe is not expanding as Einstein already shown with his field equation and the right value of cosmological constant (whatever it is, it just keeps the universe put forever).

There are always guys who claim crazy thing against logic (even if it is such good logic as Einstein's). Apparently Einstein just ignored such claims. He said "I believe my theory of relativity to be true. But it will only be proved for certain in 1981, when I am dead." It was not proved yet since some people still think that the universe is not "Einstein's" and that it is expanding. But just think how long people believed in attractive gravitational force despite that even Newton was against it. Now they believe, against Einstein, in the "expansion of space". I give that belief a few more years and then they switch since for how long one can live on math only and ignore physics and observations? Astronomers get already a little bit nervous with the predictions of the Big Bang cosmology being opposite to the observations and necessity to support them with new epicycles.

Wheeler wrote about cosmological constant as about Einstein's biggest blunder. In 1998 observations showed that there must be a non zero cosmological constant so Wheeler was wrong and Einstein was right. Wheeler's metric is symmetric, Einstein's is non symmetric. Want to bet who comes out right this time? Actually it wouldn't be fair bet since I know that symmetric metric is mathematical impossibility if energy is conserved, and most physicists believe it is. Just wait until the non symmetric metric becomes official, and all other things in which Wheeler failed as a mathematician and a physicists get popularized as well. Feynman might have Wheeler (his teacher) on his mind when he said "...such people are not only bad physicists but also bad mathematicians..."

JimJast wrote:There are always guys who claim crazy thing against logic (even if it is such good logic as Einstein's). Apparently Einstein just ignored such claims. He said "I believe my theory of relativity to be true. But it will only be proved for certain in 1981, when I am dead." It was not proved yet since some people still think that the universe is not "Einstein's" and that it is expanding. But just think how long people believed in attractive gravitational force despite that even Newton was against it. Now they believe, against Einstein, in the "expansion of space". I give that belief a few more years and then they switch since for how long one can live on math only and ignore physics and observations? Astronomers get already a little bit nervous with the predictions of the Big Bang cosmology being opposite to the observations and necessity to support them with new epicycles.

So, is Einstein God? or is he the only one who knows God's design? Even Newton was wrong. Could it not be that Einstein may be wrong. Einstein was a genius, no doubt, but a lot more is now known. Perhaps even Einstein would revise his view of the universe. Einstein was not infallible.

JimJast wrote:Wheeler wrote about cosmological constant as about Einstein's biggest blunder. In 1998 observations showed that there must be a non zero cosmological constant so Wheeler was wrong and Einstein was right. Wheeler's metric is symmetric, Einstein's is non symmetric. Want to bet who comes out right this time? Actually it wouldn't be fair bet since I know that symmetric metric is mathematical impossibility if energy is conserved, and most physicists believe it is. Just wait until the non symmetric metric becomes official, and all other things in which Wheeler failed as a mathematician and a physicists get popularized as well. Feynman might have Wheeler (his teacher) on his mind when he said "...such people are not only bad physicists but also bad mathematicians..."

wiki wrote:Cosmological Constant: History

Einstein included the cosmological constant as a term in his field equations for general relativity because he was dissatisfied that otherwise his equations did not allow, apparently, for a static universe: gravity would cause a universe which was initially at dynamic equilibrium to contract. To counteract this possibility, Einstein added the cosmological constant. However, soon after Einstein developed his static theory, observations by Edwin Hubble indicated that the universe appears to be expanding; this was consistent with a cosmological solution to the original general-relativity equations that had been found by the mathematician Friedman.

It is now thought that adding the cosmological constant to Einstein's equations does not lead to a static universe at equilibrium because the equilibrium is unstable: if the universe expands slightly, then the expansion releases vacuum energy, which causes yet more expansion. Likewise, a universe which contracts slightly will continue contracting.

Since it no longer seemed to be needed, Einstein called it the '"biggest blunder" of his life, and abandoned the cosmological constant. However, the cosmological constant remained a subject of theoretical and empirical interest. Empirically, the onslaught of cosmological data in the past decades strongly suggests that our universe has a positive cosmological constant. ...

BTW and FYI, there are current theories that include nonsymmetric tensors. Although they claim dark energy and dark matter are not necessary, they require the use of non constant constants. See MOG.

bystander wrote: BTW and FYI, there are current theories that include nonsymmetric tensors. Although they claim dark energy and dark matter are not necessary, they require the use of non constant constants. See MOG.

How satisfying to know I contributed something seen by someone else as having real value.

bystander wrote:So, is Einstein God? or is he the only one who knows God's design? Even Newton was wrong. Could it not be that Einstein may be wrong. Einstein was a genius, no doubt, but a lot more is now known. Perhaps even Einstein would revise his view of the universe. Einstein was not infallible.

Newton was right: so far there is no evidence of action at a distance in universe and so Newton was right that there is no gravitational attraction, just the illusion of it in minds of stupid humans. Einstein was a physicists who knew some physical principles and knew how to apply them. One can deduce a lot of stuff just from physical principles (like eg. from the principle of conservation of energy). It gives one a lot of intuition that sometimes is wrong but in long run proved to be better then just mathematical assumptions supported by illusions and prejudice. The assumption that the universe is expanding was surely a mistake. Had Wheeler been better physicist he might have never made this mistake. But some people aleadly allow creation of energy and action at a distance and then they have the same probems that Wheeler had.

BTW and FYI, there are current theories that include nonsymmetric tensors. Although they claim dark energy and dark matter are not necessary ...

As I already mentioned, any true theory has to include non symmetric tensors since it is just a mathematical fact that conservation of energy in stationary spacetime requires non symmetric tensors. And then the dark energy, being just a mathematical support of Wheeler's assumption of expansion of space, is not needed anymore. We could just ask Einstein to spare ourselves decades of "expanding univese model". Einstein admitted "the biggest blunder of his life" only because discovering the cosmolgical constant awoke a desire in every cosmologists and his brother to meet Einstein about the universe. So it was a nuisence, reason for which Einstein jokingly called "the biggest blunder of his life". Then Einstein decided to forbid his secretaty to let in anyone who wanted to talk to him about the universe [source: a chat with my teacher, Roy Glauber, who was an assistant to Einstein at that time].

At this moment I have read 15 chapters of John Moffat's book, Reinventing Gravity. I must admit that for the first half it was a rehash of the history of astronomy, general relativity and quantum mechanics, but JM was simply building his case. I almost laid it aside. Three days later and getting past chapter 10, my interest in his extremely logical arguments was piqued by his close match of observed data and accuracy of predictions using a non-constant value of gravity. JM is right on track-not for re-inventing gravity, but for deriving a much more accurate mathematical description of gravity. This is just what Einstein did to Newton's equations. You might want to know that JM's results are identical for those of Newton and Einstein for objects in the zone extending from the sun out to the orbit of Saturn where things start to change. Past Saturn, even Einstein’s equations don’t fit the observed data. JM has gravity increasing out to 135 parsecs before it changes again. JM's equations contain no "free" numbers and they are verified repeatedly with observed data from numerous sources, whereas the "dark matter" club has several "free" numbers in their equations that have been changed to match observed data.

Read the book. Stay tuned. Dark matter just might turn out to be nothing more than a cool idea. This race for a modified theory of gravity is heating up!

Mond didnt seem to fit the observation
http://en.wikipedia.org/wiki/Modified_N ... n_Dynamics
"Since then, many such LSBs have been observed, and some astronomers have claimed their data invalidated MOND. There is evidence that a contradiction exists.[2]

An exception to MOND other than LSB is prediction of the speeds of galaxies that gyrate around the center of a galaxy cluster. Our galaxy is part of the Virgo supercluster. MOND predicts a rate of rotation of these galaxies about their center, and temperature distributions, that are contrary to observation.[3][4]"

Also,

An empirical criticism of MOND, released in August 2006, involves the Bullet cluster (Milgrom's comments[1]) , a system of two colliding galaxy clusters. In most instances where phenomena associated with either MOND or dark matter are present, they appear to flow from physical locations with similar centers of gravity. But, the dark matter-like effects in this colliding galactic cluster system appears to emanate from different points in space than the center of mass of the visible matter in the system, which is unusually easy to discern due to the high energy collisions of the gas in the vicinity of the colliding galactic clusters.[2]. MOND proponents admit that a purely baryonic MOND is not able to explain this observation. "

Also on Tensor-vector-scalar gravity:

" However, other authors (see Slosar, Melchiorri and Silk [6]) claim that TeVeS can't explain cosmic microwave background anisotropies and structure formation at the same time, i.e. ruling out those models at high significance."


So i will wait till i see something good out of it. But it is not there yet.

What do you guys think of this answer:
http://wiki.answers.com/Q/What_is_the_r ... d_distance

Doum wrote:Mond didnt seem to fit the observation
http://en.wikipedia.org/wiki/Modified_N ... n_Dynamics
"Since then, many such LSBs have been observed, and some astronomers have claimed their data invalidated MOND. There is evidence that a contradiction exists.[2]

An exception to MOND other than LSB is prediction of the speeds of galaxies that gyrate around the center of a galaxy cluster. Our galaxy is part of the Virgo supercluster. MOND predicts a rate of rotation of these galaxies about their center, and temperature distributions, that are contrary to observation.[3][4]"

Also,

An empirical criticism of MOND, released in August 2006, involves the Bullet cluster (Milgrom's comments[1]) , a system of two colliding galaxy clusters. In most instances where phenomena associated with either MOND or dark matter are present, they appear to flow from physical locations with similar centers of gravity. But, the dark matter-like effects in this colliding galactic cluster system appears to emanate from different points in space than the center of mass of the visible matter in the system, which is unusually easy to discern due to the high energy collisions of the gas in the vicinity of the colliding galactic clusters.[2]. MOND proponents admit that a purely baryonic MOND is not able to explain this observation. "

Also on Tensor-vector-scalar gravity:

" However, other authors (see Slosar, Melchiorri and Silk [6]) claim that TeVeS can't explain cosmic microwave background anisotropies and structure formation at the same time, i.e. ruling out those models at high significance."


So i will wait till i see something good out of it. But it is not there yet.

Duom, you've been studying English in your spare time!

It's an April Fool's joke, right?

For a real answer, see http://www.astro.ucla.edu/~wright/cosmo_02.htm#MD (Ned Wright's cosmology pages, linked to from March 29th's APOD).

No. I copy and pasta.