How is molecular hydrogen detected?

[twofish-quant]

If you are calculating the forces on particles A, B, C, and D, it is completely inappropriate for you to draw a circle around an arbitrary observer O, and then treat all of the mass in that circle as though it were a point mass at point O.

Why? That's how the universe behaves.

The problem here is that you are trying to do philosophy rather than physics.

(The other major error in the article is equation 2.3... Failure to apply time dilation and the relativity of simultaneity.)

This is a Newtonian model. In it we are assuming that the speed of light is infinite and there is no time dilation. If we add time dilation and relativity, then we can't do anything Newtonian and we have to go to full blown GR. If you add the speed of light and time dilation to a Newtonian model, then what you end up with is likely to be inconsistent and wrong (it's a fun physics problem.)

The assumption here is that the "real theory of gravity" is "close enough" to Newtonian that we can do everything using Newtonian physics. You can show that this is true if the velocities involved are less than the speed of light. The problem with using GR is that then be becomes very hard to visualize.

In the real world, we don't know what the "true model" of gravity is. We *do* know that under most situations it looks like Newtonian gravity and under every situation that we've been able to measure, it looks like GR. So rather than apply an unknown model that's impossible to visualize, you take the observation that things are "close to Newtonian" do the problem and then work backward to argue that the difference between Newtonian and the actual situation isn't important to the conclusions.

 

[twofish-quant]

As I pointed out, attacks on me and my character, and appeals to consensus really don't convince me that you're right.

Maybe I don't care about convincing you. One thing about these sorts of conversations is that you often aren't trying to convince the person you are arguing with, but rather you are trying to convince a bystander.

It's constructive criticism. You certainly have the mathematical ability to do interesting things in physics, and personally, I think it's a shame that you are wasting it. I think that much of the problem is that you are "doing philosophy" rather "doing physics." Ultimately, what you seem to be looking for isn't there. If you keep asking for justifications, then at some point the response is "well that's just how the universe works."

A lot about doing physics is learning a *culture*. It's not my responsibility to convince you that you are wrong or right, and since you have no power over me, I really don't care that much if you are wrong or right. There's no requirement that you have to agree with the consensus (because the consensus is often wrong), but in order to have a reasonable discussion there *is* a requirement that you understand what the consensus is.

Ultimately, if you yourself care about learning the truth about the universe, then *you will have to convince yourself*. I can just point you in the right direction, but if that's not a road that you want to walk down, then there is nothing I can do. You can at this point argue that you find the evidence for deceleration to be unconvincing, but at this point you can't argue that no hasn't shown you the data, and there are enough references so that you can track down the rest of it if you are interested.

I do like it when people are interested in physics and cosmology, and I think that it's a real shame that you have spend so much effort on this particular issue with there are *thousands* of other problems that you could have spent your time and effort working on.

 

[twofish-quant]

Here's another way of thinking of it...

I have point A. You can argue that all of the forces are balanced at point A, so it doesn't accelerate.

I have point B. You can argue that all of the forces are balanced at point B, so it doesn't accelerate.

AHA! You say, the universe must then be non-accelerating!

But that doesn't work. If I start with point A as my origin, and then look at point B, I find that there is a force at point B pulling it toward point A. But wait, I just showed that the forces are balanced if I take point B as the origin? What gives?

The issue here is that the forces at point B when viewed from point A are *different* from the forces at point B when viewed from point B, because when you change coordinate systems then the forces change. But how can that be? Don't forces stay the same when you change between inertial coordinate systems?

Yes, but from point A's point of view, point B is not an inertial coordinate system, it's accelerating, and because it's accelerating, when you switch between point A and point B, the forces change. From point B's point of view, it's an inertial coordinate system, and A is accelerating. So when you switch between A and B, you have to change the forces to take into account the fact that the coordinate systems are non-inertial.

From A's point of view, there is a force on B pulling B toward A, and there is zero forces at A. Now when you switch to B's point of view, you are a non-inertial reference frame from A's point of view. To make it inertial, you have to subtract the forces that are acting on it. That causes the forces at B from B's point of view to go to zero, and then causes the A to go from zero force to the opposite of what was the force that A sees acting on B.

So if you take any point as the origin, you will see a force of zero for that point, but you will see non-zero forces for points other than the origin.

Now then you see how the universe works. We don't have any infinite clouds, but we have clouds that are "practically" infinite. You take something like the interstellar medium with a one light year cube, and then take a piece that is much, much smaller, and see how you calculate gravity.

 

[twofish-quant]

If you are calculating the forces on particles A, B, C, and D, it is completely inappropriate for you to draw a circle around an arbitrary observer O, and then treat all of the mass in that circle as though it were a point mass at point O.

It would make much more sense to account for the masses near the objects A, B, C, D, respectively, to calculate the forces that are acting upon them.

And if you do your bookkeeping right, you come up with the same answer. The important thing is to keep track of what reference frame you are in so that you can account for non-inertial effects correctly.

 

[JDoolin]

We seem to be in some disagreement over what Milne's Model actually is.

The general properties of Milne's model is
(1) It is a "Big Bang" in the literal sense.

Milne says there was no big bang.

By the way, this is the sort of argument that I regard as "simple contradiction" and sometimes I might forget to respond to such a thing. What can I add when I make a statement "P," and then someone else argues "Not P?" My statement comes from reading Relativity, Gravitation, and World Structure. Your argument is just the negation of my statement.

Milne's model is fundamentally different from the Standard Model in the sense that whereas the standard model claims that the Big Bang was a whole lot of events shrunk down to a zero volume by a scale factor a(t)=0 at t=0. Milne's model is still a big bang, but a big bang of an entirely different character, where you simply have a single event at t=0.

I just wanted to clarify that, in case anyone was confused. There's no wiggle-room in Milne's model to say "No--it's not really a big bang, it's actually just space stretching." Milne's model is a literal "Big Bang" model.
-----

That's not correct. Newton's second law is

\vec F = \frac{d\vec{p}}{dt}

The dp/dt formulation does not change the argument, by the way. The point is you are dealing not just one force, but a sum of forces.
\sum \vec F = \frac{d\vec{p}}{dt}
And if the sum of those forces is zero, there is no acceleration, and there is also not a change in momentum.

All I've been doing here is giving you arguments. You are free to reject those arguments, but if you *ignore* those arguments then people will just give up talking with you. I posted a link to the supernova results. If you take a look at them and say "well maybe Milne was wrong" then we might be getting somewhere. If you take a look at them and say "MILNE IS GOD AND CAN'T BE WRONG" then I might as well be arguing with young Earth creationists.

I have not intended to ignore any of your arguments, except for those which are "simple contradiction" or "strawmen." If you have arguments of some other variety that you feel I have ignored, please repeat them.

 

[JDoolin]

Here's another way of thinking of it...

I have point A. You can argue that all of the forces are balanced at point A, so it doesn't accelerate.

I have point B. You can argue that all of the forces are balanced at point B, so it doesn't accelerate.

AHA! You say, the universe must then be non-accelerating!

But that doesn't work. If I start with point A as my origin, and then look at point B, I find that there is a force at point B pulling it toward point A. But wait, I just showed that the forces are balanced if I take point B as the origin? What gives?

The issue here is that the forces at point B when viewed from point A are *different* from the forces at point B when viewed from point B, because when you change coordinate systems then the forces change. But how can that be? Don't forces stay the same when you change between inertial coordinate systems?

Yes, but from point A's point of view, point B is not an inertial coordinate system, it's accelerating, and because it's accelerating, when you switch between point A and point B, the forces change. From point B's point of view, it's an inertial coordinate system, and A is accelerating. So when you switch between A and B, you have to change the forces to take into account the fact that the coordinate systems are non-inertial.

From A's point of view, there is a force on B pulling B toward A, and there is zero forces at A. Now when you switch to B's point of view, you are a non-inertial reference frame from A's point of view. To make it inertial, you have to subtract the forces that are acting on it. That causes the forces at B from B's point of view to go to zero, and then causes the A to go from zero force to the opposite of what was the force that A sees acting on B.

So if you take any point as the origin, you will see a force of zero for that point, but you will see non-zero forces for points other than the origin.

Now then you see how the universe works. We don't have any infinite clouds, but we have clouds that are "practically" infinite. You take something like the interstellar medium with a one light year cube, and then take a piece that is much, much smaller, and see how you calculate gravity.

I think I begin to understand something of where this is going. I appreciate your further explanation.

The essential difference then, between Milne's Model and the Standard Model is whether two observers will disagree on simultaneity of distant objects(in Milne's Model), or whether two observers will disagree on the forces on distant objects(in the Standard Model.)

Thank you for giving further explanation here.

I still think that ignoring the relativity of simultaneity is a flaw, but I also realize now that I was misunderstanding Einstein's argument.

He was literally saying that the force on a distant particle is an observer dependent quantity, while time is an observer independent quantity. That seems amazing to me, and I will have to think about it further.

Wouldn't that mean, observationally, that all objects in the universe should be accelerating toward us?

 

[Chronos]

I agree with TQ, JDoolin, your arguments appear philosophical and you seem to refrain from mathematically sound assertions. I would like to see the math.

 

[twofish-quant]

Milne's model is fundamentally different from the Standard Model in the sense that whereas the standard model claims that the Big Bang was a whole lot of events shrunk down to a zero volume by a scale factor a(t)=0 at t=0.

That's not true. Standard Model (version 2012) says absolutely nothing about what happens at t=0 a(t)=0. Standard model (version 2012) breaks once you exit the inflationary era.

Maybe Standard Model (version 2020) will have something to say about this.

Milne's model is still a big bang, but a big bang of an entirely different character, where you simply have a single event at t=0.

If the "big bang" was of an entirely different character, then you have a problem because we have lots of good observations of the big bang. Once you have the scale factor a(t), you can calculate nuclear reaction rates, and once you do that, you get helium and deuterium abundances.

There *is* a paper which a I cited, in which people have claimed that you can get correct abundances in a Milne-Dirac universe, but that involves 1) assuming that the universe consists of 50% anti-matter and 2) assuming that anti-matter is repulsive. The other thing is that they end up calculating supernova velocities which are now known to be wrong.

And if the sum of those forces is zero, there is no acceleration, and there is also not a change in momentum.

Right, the dp/dt argument was wrong, but the reference frame argument still stands.

If the sum of the forces is zero, you still get acceleration if you measuring the sum with respect to a non-interial reference frame. Once you pick a point to be your frame reference, then all other points become non-intertial, and if the sum of the forces is zero in those reference frames, you still have acceleration.

This happens a lot with gravity. If I'm in an elevator in free fall, I measure zero force. Even though all the forces are zero in my local reference frame, I'm still acclerating because those forces are defined in a non-interial reference frame. Once you've chosen one point in the universe, then all of the other points are non-interial therefore the fact that you get zero net force in those other frames is irrelevant.

I have not intended to ignore any of your arguments, except for those which are "simple contradiction" or "strawmen."

The trouble is that I have no idea what you think is a simple contradiction or strawman unless you tell me.

If you have arguments of some other variety that you feel I have ignored, please repeat them.

Ultimately, the only argument is "we look at the universe and it doesn't work that way".

If you take the cosmological calculation, it is equally valid in large gas clouds of indefinite size and uniform density. If Milne was right and there is no net internal gravitational force in a large cloud of uniform density, then gas clouds wouldn't collapse to form stars, but they do.

 

[Bobbywhy]

Without putting total trust in the validity of Wikipedia, here are two excerpts from the Wiki page on the “Milne Model”:

“Incompatibility with observation
Even though the Milne model as a special case of a Friedmann-Robertson-Walker universe is a solution to General relativity, the assumption of zero energy content limits its use as a realistic description of the universe. Besides lacking the capability of describing matter Milne's universe is also incompatible with certain cosmological observations. In particular it makes no prediction of the cosmic microwave background radiation nor the abundance of light elements which are hallmark pieces of evidence that cosmologists agree support Big Bang cosmology over alternatives.

At the time Milne proposed his model, observations of the universe did not appear to be in a homogeneous form. This, to Milne, was a deficiency inherent in the competing cosmological models which relied on the cosmological principle that demanded a homogeneous universe. “This conventional homogeneity is only definite when the motion of the particles is first prescribed.” With present observations of the homogeneity of the universe on the largest scales seen in the cosmic microwave background and in the so-called "End of Greatness", questions about the homogeneity of the universe have been settled in the minds of most observational cosmologists.”

http://en.wikipedia.org/wiki/Milne_model

 

[twofish-quant]

The essential difference then, between Milne's Model and the Standard Model is whether two observers will disagree on simultaneity of distant objects(in Milne's Model), or whether two observers will disagree on the forces on distant objects(in the Standard Model.)

First of all, let's not talk about the standard model since that's a moving target. What goes for the standard model will change over time. If it turns out that there is some massive observational flaw in the supernova data and the deceleration parameter is zero, then Milne's model will be Standard Model - version 2020.

Second, I'm explicitly not using the standard model of cosmology (2012), but something that is "close enough" that we can argue meaningfully about it. I'm using a Newtonian model of cosmology which is the zeroth order approximation. The Newtonian model includes assumptions that are *known* to be wrong (i.e. the speed of light is infinite) and results in conclusions that are also *known* to be wrong (i.e. Newtonian models don't take into account geometric curvature).

The reason I'm arguing based on a Newtonian cosmology is that neither you or I know general relativity well enough to have a reasonable discussion based on Friedmann-Walker models. The differences between Newtonian cosmology and FLRW are well known enough so that we can argue in a Newtonian world, and then figure out the implications once we add in GR.

The good thing about Newtonian models is that people have a good intuition about Newtonian. If you are in a falling elevator, the forces that you measure *will* be different than for a stationary observer. The other thing about thinking in Newtonian terms is that it's not out of the question that I can think of some experiment that you can perform in your living room that shows that a different gravity model (i.e. Milne) is wrong.

He was literally saying that the force on a distant particle is an observer dependent quantity, while time is an observer independent quantity. That seems amazing to me, and I will have to think about it further.

Do this in an elevator or a subway car. If you are in a subway car that suddenly stops, it should become obvious that forces are an observer dependent quantity.

Note that we are in a Newtonian model where we are *assuming* that time is observer dependent. If you go into GR, you don't use forces at all. If you use the concept of "force" and then you add in special relativity, then you get a total mess.

Wouldn't that mean, observationally, that all objects in the universe should be accelerating toward us?

Yes. Gravity does that.

You throw a ball in the air, and it accelerates toward the ground. If you throw it hard enough then it may not ever hit the ground, but there is still acceleration toward the ground. An apple drops from a tree, it goes to the ground.

Now we know this to be wrong. Things are accelerating *away* from us. You toss a ball in the air, it speeds *away* from you. This is weird. Shocking even. But that's what we see.

 

[twofish-quant]

Besides lacking the capability of describing matter Milne's universe is also incompatible with certain cosmological observations. In particular it makes no prediction of the cosmic microwave background radiation nor the abundance of light elements which are hallmark pieces of evidence that cosmologists agree support Big Bang cosmology over alternatives.

This isn't strictly true. I had a link to a paper that claimed that you can get CMB and light elements in a Milne-Dirac universe. You can search for it on the Los Alamos preprint server. The trouble is that in order to get those numbers you have to assume that the universe is 50% anti-matter and that anti-matter repels each other.

This is one of those papers that is totally nutty until something happens. If people do AEGIS and it turns out that anti-matter gravity is repulsive then someone is got a free trip to Sweden.

One thing about productive physicists is that every productive physicist I know of has at least one nutty idea. I know of a Nobel Prize winner that was convinced that black holes didn't exist, to the point that no one dared mention those words in front of him. However, he was productive because he had lots of ideas, so instead of spending 100% of his time disproving black holes, he spent 1-5% of his time on this, and then 30% of his time on stuff that got him the Nobel Prize.

There's a famous astrophysicist who was President of the AAS who has some truly crazy ideas about astrophysical jets (he doesn't think they exist). The thing is that he is nice about it. He isn't going to talk about astrophysical jets unless you ask him to talk about astrophysical jets, and if you ask him to talk about them, he'll calmly tell you a theory which everyone else thinks is truly wacko. But he spends most of his time on star formation.

It's the ability not to be totally consumed by one idea that distinguishes Roger Penrose from Halton Arp. Penrose has some truly nutty ideas. It's that he has enough pokers in the fire, that *something* is going to hit paydirt.

One problem with the original poster is that he is mining for gold in California. There was once a lot of gold in California, but people came in and took it all, so there's not much left. We are talking about arguments from the 1930's, and anything that was "paydirt" in 1930 has been mined out. Now if you want to mine the Amazon rain forest or the moon for gold, that's different.

 

[Chronos]

We can agree the current model has warts. That does not mean it is wrong, merely incomplete. We can improve on a model that is incomplete, we cannot improve on a model that is wrong.

 

[JDoolin]

I agree with TQ, JDoolin, your arguments appear philosophical and you seem to refrain from mathematically sound assertions. I would like to see the math.

Maybe I am refraining a little bit, because I still remain concerned that anything I say might be construed as "original research." Besides which, for all I know, I may well not even be competent to make "sound" assertions.

I don't have the time or energy to type up a lot of LaTeX, and I am not sure you'll be happy with the level of math content here, but I want to summarize my point-of-view, and maybe if you can just see the things I'm seeing, it would help to communicate.

http://www.spoonfedrelativity.com/misc/2012-07-10_2237-Math-Justification-1.swf
http://www.spoonfedrelativity.com/misc/2012-07-10_2257-Mathematical-Justification-2.swf
http://www.spoonfedrelativity.com/misc/2012-07-10_2313-Mathematical-Justification-3.swf
http://www.spoonfedrelativity.com/misc/2012-07-10_2352-Mathematical-Justification-4.swf
http://www.spoonfedrelativity.com/misc/2012-07-11_0013-Mathematical-Justification-5.swf

You see, there is nothing here about "the data" at all. I have no data. I haven't seen the data. My only argument is a philosophical one: I don't think it is right to throw away Lorentz Transformations. I think that special care should be made to try to figure out possible structure of the universe based on the POSSIBILITY that Milne was right. I'm not saying certainty. I'm saying POSSIBILITY.

 

[JDoolin]

This isn't strictly true. I had a link to a paper that claimed that you can get CMB and light elements in a Milne-Dirac universe. You can search for it on the Los Alamos preprint server. The trouble is that in order to get those numbers you have to assume that the universe is 50% anti-matter and that anti-matter repels each other.

This is one of those papers that is totally nutty until something happens. If people do AEGIS and it turns out that anti-matter gravity is repulsive then someone is got a free trip to Sweden.

I would like to see that paper, because that sounds like someone taking the Milne model seriously. It also sounds not at all nutty to me. Okay, maybe a little nutty. Speculative, but definitely in the realm of possibilities. Considering we've surely never had any anti-matter in large enough quantities, and around long enough to get a measure of it's gravitational field, have we?

 

[Bobbywhy]

I followed Halton Arp for years, thinking intrinsic redshift was a characteristic of quasars and that quasars were "connected" to low-redshift galaxies. I even wanted to believe the Tifft quantizatiion of redshifts. After many years of trying I gave up and got on with my learning process. My lesson learned: do not let wishful thinking and emotion control my science.

Oh Jonathan Doolin, I watched and listened carefully to -1, -3, -4, and -5 above. -2, as you say, is not functional right now. Too bad, though, as the first time through those four I was confused. So, I watched and listened to all four a second time. Now I am a trained listener and a professional public speaker (Toastmasters International=28 years) but, unfortunately, I never could figure out what message you were trying to communicate in each of those four modules. Perhaps your written script could be revised to be more coherent and to clearly address the point you want to make. The point is I couldn't find the point. Do the titles "spoonfedrelativity" intimate that even babies should understand your explanations?

Since you seem to have some great passion for Milne's Cosmology, could you simply write up a clear, professional paper with all your work and ideas, and then send it to some publisher that would then submit your work to peer review. Would that not either prove or disprove your approach?

Cheers, Bobbywhy

 

[JDoolin]

I followed Halton Arp for years, thinking intrinsic redshift was a characteristic of quasars and that quasars were "connected" to low-redshift galaxies. I even wanted to believe the Tifft quantizatiion of redshifts. After many years of trying I gave up and got on with my learning process. My lesson learned: do not let wishful thinking and emotion control my science.

Oh Jonathan Doolin, I watched and listened carefully to -1, -3, -4, and -5 above. -2, as you say, is not functional right now. Too bad, though, as the first time through those four I was confused. So, I watched and listened to all four a second time. Now I am a trained listener and a professional public speaker (Toastmasters International=28 years) but, unfortunately, I never could figure out what message you were trying to communicate in each of those four modules. Perhaps your written script could be revised to be more coherent and to clearly address the point you want to make. The point is I couldn't find the point. Do the titles "spoonfedrelativity" intimate that even babies should understand your explanations?

Since you seem to have some great passion for Milne's Cosmology, could you simply write up a clear, professional paper with all your work and ideas, and then send it to some publisher that would then submit your work to peer review. Would that not either prove or disprove your approach?

Cheers, Bobbywhy

Thank you. Yes the original intent of the SpoonfedRelativity site was to communicate Special Relativity and eventually General Relativity in the clearest way possible. That was before I realized that Special Relativity and cosmological General Relativity were in direct conflict, and the FLRW metric assumes as one of its premise that the Lorentz Transformation equations are invalid at large distances.

Since then the website has become a big confusing question mark. It doesn't Spoonfeed anyone anything; instead it is a list of all of the arguments that have been accumulated over the years. At this point, it represents a personal cache of memories of what I was trying to do during Christmas Break or summer breaks a year, or two years or three,or many years ago,

However, I am finding that the Jing videos and the stylus tool might be a much better tool to use to keep track of what I am doing, figure out how to MAKE my point, and eventually come up with a better explanation.

 

[JDoolin]

Oh Jonathan Doolin, I watched and listened carefully to -1, -3, -4, and -5 above. -2, as you say, is not functional right now.

The video-2 is functioning just fine. There are several animations in it. Mathematica was not functioning so I couldn't show you the program behind it. I suppose I could attach the .nb (Mathematica notebook) file if you'd like. Say the word, and I will try to locate it. (Though not today, I am totally out of time for this project today!)

 

[twofish-quant]

That was before I realized that Special Relativity and cosmological General Relativity were in direct conflict, and the FLRW metric assumes as one of its premise that the Lorentz Transformation equations are invalid at large distances.

Yes. This is something that people are aware of, and I remember my cosmology professor mentioning it in an early lecture. It's not an assumption so much as a consequence. Once you start with the premise that the universe is isotropic and homogenous, then at large distances things are going to be flying away from each other at > c, and Lorenz transformation will break down.

Essentially, if you try to do cosmology using special relativity, you end up getting a big inconsistent mess. So you either do things with Newtonian gravitation or else you do it with full general relativity.

The reason that Einstein is considered a genius, is that once you figure out that the speed of light is finite, it's not easy to come up with a theory of gravity that's consistent. The "obvious" ways of adding relativity to gravity don't work.

There are people that believe that if Einstein hadn't come up with the key ideas, that we'd still be struggling trying to figure out how to make gravity work with relativity.

 

[twofish-quant]

I would like to see that paper, because that sounds like someone taking the Milne model seriously.

http://arxiv.org/abs/1110.3054

And it was published in A&A

http://adsabs.harvard.edu/abs/2012A&A...537A..78B

One bit of constructive criticism is that you *really* need to learn how to do basic library research. Once you have that one paper, you'll find a cluster of people that are working on Milne-Dirac universes.

I got to that paper, by going to http://arxiv.org/ and typing in "Milne cosmology".

It's a very good example of how to present a "nutty theory" that passed peer review. The fact that you can get the right baryon-acoustic oscillations with Milne-Dirac is a non-obvious and interesting result. Also, even if it's wrong, it's interesting. The situation is that in order to have a Milne universe, you have to have no gravity. You can get no gravity by either having an empty universe or by having a universe that is 50% antimatter in which the antimatter counteracts the gravity of the matter.

Also, you have to read papers critically. The supernova data they cite is old and noisy, and more recent data move things away from the Milne baseline.

Considering we've surely never had any anti-matter in large enough quantities, and around long enough to get a measure of it's gravitational field, have we?

Again, figuring this stuff out is why you have to learn to do library research but...

That's what AEGIS is for. If we do the experiment and it turns out that anti-matter has gravitational repulsion, then people get free trips to Stockholm.

There is the "magic wand" or "tooth fairy rule" of cosmology papers. In any paper, you are allowed one free wave of the magic wand. The problem with the Milne-Dirac papers is that they wave the magic wand twice. Once assuming that antimatter is repulsive and the other that assumes that somehow there are vast quantities of hidden antimatter in the universe.

If AEGIS shows something unexpected, then you now have only one magic wand wave.

 

[twofish-quant]

I followed Halton Arp for years, thinking intrinsic redshift was a characteristic of quasars and that quasars were "connected" to low-redshift galaxies. I even wanted to believe the Tifft quantizatiion of redshifts. After many years of trying I gave up and got on with my learning process. My lesson learned: do not let wishful thinking and emotion control my science.

Arp's ideas weren't crazy for 1965, and if you have *only* the data that was available to people in 1965, then they make a lot of sense. The trouble is all of the data after 1965. One thing is that in the early observational stages you are always looking at fuzzy, noisy data and so it's easy to interpret the data in many different ways. The problem is that after a while the data becomes clearer and clearer.

Also, there's nothing wrong with wishful thinking and emotions, but it's important to manage wishful thinking and emotions. The other thing is that the problem with Arp is that he didn't have a "portfolio" of nutty ideas. Roger Penrose is a crank on some things, but you can ignore his ideas on neuroscience and look only at his quasi-crystal stuff. For that matter, Albert Einstein and Issac Newton had some crazy ideas that didn't work out.

The other thing is that there are a lot of scientists (probably most scientists) that are "closet cranks." Which is to say that they have crazy ideas, but if you argue with them, they'll tell that that yes I know this is crazy, and then smile and change the subject.

Since you seem to have some great passion for Milne's Cosmology, could you simply write up a clear, professional paper with all your work and ideas, and then send it to some publisher that would then submit your work to peer review.

The trouble is that none of this is original or particularly interesting.

The papers I linked on to Milne-Dirac are publishable because they have something *new*. It's not obvious that you can get baryon acoustic oscillations and the right helium abundances with Milne-Dirac, and that's a *new* and *original* result.

The other thing is that peer review is a terrible process for getting feedback. Peer reviewers are editors, they aren't teachers. If a peer reviewer looks at your paper for ten seconds and thinks it's garbage, they'll just stamp reject without any comment, because they are busy and unpaid, and it's not their job to teach you astrophysics.

Would that not either prove or disprove your approach?

I don't think it would. The thing about journals is that there are "unwritten rules" as to how you present an argument, and if you don't know those rules (and you learn them in graduate school), then you aren't going to get anywhere.

 

[Chronos]

I agree, twofish. Most of the genius ideas posted on this site seem plagued by a shocking ignorance of math and fundamental physics.

 

[Bobbywhy]

twofish-quant, thank you for your comments in post #70 above. "Crazy ideas" musn't be ignored without thorough consideration of their source. Since I am not a professional scientist your viewpoints are enlightening...one of the great benefits of PF! I certainly learned a lot by following the exchange between you and JDoolin!

 

[twofish-quant]

"Crazy ideas" musn't be ignored without thorough consideration of their source.

It's quite complicated...

The reason I mention Roger Penrose is that when he is talking about neuroscience he really is a crank. However, curiously the things that make him a crank in one field makes him totally brilliant in another. If you hear him talk about neuroscience, you can tell it's the same person that is doing work in quasi-crystals. However, he got lucky that in one area, the data seemed to end working in his direction, and in another it hasn't.

The thing about "crazy ideas" is that it's a matter of time allocation. OK, someone mentions a nutty idea. Now what? What exactly is it that you want me to do with it?

One problem with cosmology is that there are realms in which it's not clear what is "crazy" and what itself. Once you get into the inflationary era, then it's not clear what's nutty and what isn't. However, one thing that I don't think that the general public doesn't quite appreciate is that most of cosmology happens in "non-crazy" areas. Popular works in cosmology play up the "weird physics" and often miss the point that most of cosmology takes place in situations where the physics isn't weird at all.

For example, once you get past the very, very, very early universe, you are just talking about "gas and gravity." Some of the big mysteries involve things that are unlikely to involve any super-weird physics. Galaxy formation, and early star formation for example.

 

[JDoolin]

That was before I realized that Special Relativity and cosmological General Relativity were in direct conflict, and the FLRW metric assumes as one of its premise that the Lorentz Transformation equations are invalid at large distances.

Yes. This is something that people are aware of, and I remember my cosmology professor mentioning it in an early lecture. It's not an assumption so much as a consequence. Once you start with the premise that the universe is isotropic and homogenous, then at large distances things are going to be flying away from each other at > c, and Lorenz transformation will break down.

Essentially, if you try to do cosmology using special relativity, you end up getting a big inconsistent mess. So you either do things with Newtonian gravitation or else you do it with full general relativity.

The reason that Einstein is considered a genius, is that once you figure out that the speed of light is finite, it's not easy to come up with a theory of gravity that's consistent. The "obvious" ways of adding relativity to gravity don't work.

There are people that believe that if Einstein hadn't come up with the key ideas, that we'd still be struggling trying to figure out how to make gravity work with relativity.

Here is my problem in arguing with you guys. The continually retreating premise. If I say that FLRW metric is based on the premise that Lorentz Transformation is invalid at large distances, you claim that that is not a premise. The premise is homogeneity and isotropy.

But when Milne showed you that isotropy is possible without homogeneity, so long as you account for special relativity, then you change your story. Now, that is impossible because it doesn't fit with the FLRW metric.

But yes, a lot of Gravitation, Relativity, and World Structure is devoted to explaining that argument. Explaining how and why Einstein and Eddington are wrong--that isotropy is indeed possible without homogeneity. And the premise on which the FLRW metric is based, is fundamentally flawed.

If you would acknowledge that point, then you might begin to focus on my real argument instead of straw-men.

 

[JDoolin]

It's quite complicated...

The reason I mention Roger Penrose is that when he is talking about neuroscience he really is a crank. However, curiously the things that make him a crank in one field makes him totally brilliant in another. If you hear him talk about neuroscience, you can tell it's the same person that is doing work in quasi-crystals. However, he got lucky that in one area, the data seemed to end working in his direction, and in another it hasn't.

The thing about "crazy ideas" is that it's a matter of time allocation. OK, someone mentions a nutty idea. Now what? What exactly is it that you want me to do with it?

One problem with cosmology is that there are realms in which it's not clear what is "crazy" and what itself. Once you get into the inflationary era, then it's not clear what's nutty and what isn't. However, one thing that I don't think that the general public doesn't quite appreciate is that most of cosmology happens in "non-crazy" areas. Popular works in cosmology play up the "weird physics" and often miss the point that most of cosmology takes place in situations where the physics isn't weird at all.

For example, once you get past the very, very, very early universe, you are just talking about "gas and gravity." Some of the big mysteries involve things that are unlikely to involve any super-weird physics. Galaxy formation, and early star formation for example.

I feel that Penrose made a tremendous error in claiming that Lorentz Contraction is invisible. I've actually not read Penrose account of it, but Terrell's description is online somewhere, and I posted my arguments against it on my website.

On the other hand, I have very much enjoyed reading "The Emperor's New Mind."

All I know of Penrose's ideas of neuroscience are what I read in that book, so I may be unaware of exactly how nutty he is, but I didn't see anything in "The Emperor's New Mind" that was particularly nutty or controversial. In fact, as I recall, I was excited to find someone who essentially agreed with me. I think the main point that Penrose was making was that people have opinions, and computers don't. A computer is able to compute, but it is utterly unable to make a judgment of whether that information is interesting or the effort was worthwhile. Where do those opinions come from? It is doubtful that our opinions and emotions are going to be successfully emulated with a computer in their current form. I don't know what exactly your issue with Penrose is, but given your prediliction for building straw-men, I wonder whether you are arguing with Penrose, or a straw-man version of Penrose?

I don't think that Penrose was wrong, but that Penrose was aware of something that perhaps you're not. That human-beings are opinion-generating engines. That's our function, to figure out what we value, and pursue it. Whether you agree with Penrose, or not, that that function derives from quantum mechanics, it actually relates to the argument that you were making earlier.

Your argument was that if I believe something that the consensus does not believe then it is a waste of time to spend ten years of my life on it. That is your opinion. My opinion is that those ten years were not at all wasted. While it has been painful, humiliating, and humbling at times, I got a Masters degree in physics, and a Masters degree in mathematics during that time. I became gainfully employed as an adjunct professor. I have learned a lot about physics, mathematics, logic, and emotions during that time. I've learned over the years that my opinions are not something I'm stuck with, but nobody can change them for me, either. I have to take personal responsibility for my opinions; and Penrose, pointing out that my opinions may be somehow quantum mechanical in nature--might not be terribly useful in neuroscience, but it has been helpful in my own personal psychology.

As an example, just six months ago, I realized that I was a victim of an opinion that I had--I completely lacked faith in other people. I had seen the evidence that they were continually disappointing me, never listening to me, and I had long accepted that they were going to continue to do so, and I might as well just accept it. But I decided that I was going to quantum-mechanically change that opinion, and believe that people are NOT going to disappoint me. It changes how I interact with them, and other people around me are starting to do things to impress me.

You could do it now, if you would just acknowledge my point, that Milne's model really is isotropic and nonhomogeneous. And then if someone went out and actually read "Relativity, Gravitation, and World Structure" and went out and edited the Wikipedia article so that it wasn't full of lies and nonsense about Milne's model being a zero mass version of the FLRW metric, but is, in fact, an isotropic, but nonhomogeneous distribution--an exploding sphere of matter--that would also really impress me. It would be like a "Quantum change" or something.

 

[JDoolin]

I followed Halton Arp for years, thinking intrinsic redshift was a characteristic of quasars and that quasars were "connected" to low-redshift galaxies. I even wanted to believe the Tifft quantizatiion of redshifts. After many years of trying I gave up and got on with my learning process. My lesson learned: do not let wishful thinking and emotion control my science.

Oh Jonathan Doolin, I watched and listened carefully to -1, -3, -4, and -5 above. -2, as you say, is not functional right now. Too bad, though, as the first time through those four I was confused. So, I watched and listened to all four a second time. Now I am a trained listener and a professional public speaker (Toastmasters International=28 years) but, unfortunately, I never could figure out what message you were trying to communicate in each of those four modules. Perhaps your written script could be revised to be more coherent and to clearly address the point you want to make. The point is I couldn't find the point. Do the titles "spoonfedrelativity" intimate that even babies should understand your explanations?

Since you seem to have some great passion for Milne's Cosmology, could you simply write up a clear, professional paper with all your work and ideas, and then send it to some publisher that would then submit your work to peer review. Would that not either prove or disprove your approach?

Cheers, Bobbywhy

Let's also acknowledge another point. If I'm right, it could be embarrassing and humiliating to a LOT of people. Pretty much everybody in the field of modern cosmology. Over the years, I realized that even if I'm right, it's not really that great news. In fact, if I'm right, cosmoloogy will become in some ways a lot more boring. No more searching for Dark Matter. No more great mysteries, about the fundamentals. You'd just be looking for details. Details, details, details. If I'm right, a good part of the sense of wonder about the universe will be gone.

I'm basically the idiot in the back of the room, when the teacher is doing the super-complicated equation and the only part of it that I understand is that 3+5=8 not 7. While everyone else is following along, figuring out all of the neat principles that are derived from assuming isotropy AND homogeneity, I just am too stubborn to go along with it.

When people finally notice that the idiot in the back of the room is actually right, that the teacher made a typo at the beginning, it really doesn't mean the idiot is brilliant. It just means that the idiot was right.

I really don't have a paper to write, and twofishquant is correct. I'm not a research scientist, and I certainly don't have anything *new* to say, based on new data. I don't read that much. And I don't know any of the unwritten rules of submitting an article. I just get stuck at the point where it stops making sense, and I can't read any further.

I could happily prepare a series of lectures, if I had someone who wanted to listen, but I really can't prepare a paper to send to a group of people who really really REALLY don't want to hear what I have to say.

 

[JDoolin]

http://arxiv.org/abs/1110.3054

And it was published in A&A

http://adsabs.harvard.edu/abs/2012A&A...537A..78B

One bit of constructive criticism is that you *really* need to learn how to do basic library research. Once you have that one paper, you'll find a cluster of people that are working on Milne-Dirac universes.

I got to that paper, by going to http://arxiv.org/ and typing in "Milne cosmology".

It's a very good example of how to present a "nutty theory" that passed peer review. The fact that you can get the right baryon-acoustic oscillations with Milne-Dirac is a non-obvious and interesting result. Also, even if it's wrong, it's interesting. The situation is that in order to have a Milne universe, you have to have no gravity. You can get no gravity by either having an empty universe or by having a universe that is 50% antimatter in which the antimatter counteracts the gravity of the matter.

Also, you have to read papers critically. The supernova data they cite is old and noisy, and more recent data move things away from the Milne baseline.



Again, figuring this stuff out is why you have to learn to do library research but...

That's what AEGIS is for. If we do the experiment and it turns out that anti-matter has gravitational repulsion, then people get free trips to Stockholm.

There is the "magic wand" or "tooth fairy rule" of cosmology papers. In any paper, you are allowed one free wave of the magic wand. The problem with the Milne-Dirac papers is that they wave the magic wand twice. Once assuming that antimatter is repulsive and the other that assumes that somehow there are vast quantities of hidden antimatter in the universe.

If AEGIS shows something unexpected, then you now have only one magic wand wave.

Thank you very much for the link. I have to admit I am confused about the Milne-Dirac model. But perhaps there is some way I could contact those researchers, with my questions. Typically of these articles, I find myself illiterate; unable to get past the first assertion; Equation (1), you see, simply looks wrong to me. It doesn't make any mathematical sense.

http://screencast.com/t/9WYFYl8F

 

[twofish-quant]

Here is my problem in arguing with you guys. The continually retreating premise. If I say that FLRW metric is based on the premise that Lorentz Transformation is invalid at large distances, you claim that that is not a premise. The premise is homogeneity and isotropy.

It's a premise because homogenity+isotropy+GR= FLRW.

But when Milne showed you that isotropy is possible without homogeneity, so long as you account for special relativity, then you change your story.

Who is this "you"? There are lots of people on this thread, and we don't all think the same.

I don't have any reason to dispute that isotropy is possible without homogenity, and that if you assume isotropy without homogenity, that you can get a metric that is different than FLRW. This is a well-defined mathematical question, and I have no reason to conclude that Milne got this wrong.

So what?

Now, that is impossible because it doesn't fit with the FLRW metric.

No. It's *possible*. It's just not what we observe. FLRW metric works because it's consistent with observations and Milne isn't.

Explaining how and why Einstein and Eddington are wrong--that isotropy is indeed possible without homogeneity. And the premise on which the FLRW metric is based, is fundamentally flawed.

I really don't see why this is relevant except as a historical footnote. Einstein and Eddington were wrong about a lot of things, so there's no reason why they should be right about this argument, but since I'm more interested in cosmology than science history, I don't see why this matters.

We *observe* that the universe is homogenous and isotropic, we then take these observations and create models that are consistent with these observations which gets us FLRW. It may indeed be *possible* for the universe to be non-isotropic. It's would also be *possible* for the Earth to have two moons or for me to be drinking diet Pepsi instead of Coke right now.

Lot's of things are *possible*. That's why you have to go out and see what is actually there.

If you would acknowledge that point, then you might begin to focus on my real argument instead of straw-men.

Ultimately, the only arguments that are going to convince me are "I took these measurements, and they fit the Milne model better than FLRW." Right now we are talking theory. If you assume X, Y, and Z, you must conclude A. If A isn't the case, then you look at where you messed up with X, Y, and Z.

As a *theoretical* point, the Milne model is inconsistent with any gravity model that approximates Newtonian physics. Since we *observe* that Newtonian physics works in most situations (and we can define the situations in which it doesn't), this poses a big problem.

The problem is that you are doing philosophy rather than physics. You are treating isotropy and homogenity as if they were mathematical axioms when they aren't.

With physics the only arguments that matter are those that are grounded in empirical observation. You can convince me that if we assume X, we get the Milne model. That's not hard. The problem is getting to observation.

We *observe* that the universe is homogenous and isotropy at large scales. That gets you to FLRW. If we observe something different, then we toss FLRW.

 

[twofish-quant]

Your argument was that if I believe something that the consensus does not believe then it is a waste of time to spend ten years of my life on it.

I'm not telling you how to live your life. You can live life the way that you want.

But for me, I want to do productive stuff. This means working on several things, so that if I "strike out" on one, I can get somewhere with another. It's not a matter of agreeing with consensus. It's a matter of agreeing with God. If God says that the universe does or does not work in a certain way, then no amount of effort is going to change that.

Also it's important to be *original*. I spent eight years trying to get supernova to explode with convection and came to the conclusion that it couldn't be done. This is not a waste because it was *original* in 1998. Now if someone does exactly the same thing that I did, it would be a waste of time, because it wouldn't be *new*.

The other fun stuff is to work on something for which there is no consensus. There is no consensus model on how supernova work, or for how black hole jets work, or for how galaxies formed.

My opinion is that those ten years were not at all wasted.

Again, this is a matter of personal philosophy, so if you don't agree with me then fine, but what knowledge does humanity have now that it didn't have ten years ago as a result of your efforts?

I like advancing the frontiers of knowledge. Sometimes it's something silly and trivial. You code a program one way, and you find that it doesn't work. That's "new knowledge". I can point to stuff that I know now that I didn't know a week ago, and that adds to humanities knowledge of the universe.

So when someone does something and at the end of it, humanity learns nothing, I think that's a waste. Again this is a personal view.

You could do it now, if you would just acknowledge my point, that Milne's model really is isotropic and nonhomogeneous.

I haven't worked through the math, so I don't know for sure, but I have no reason to doubt this. However, if that's true then you have a problem since the universe appears to be statistically homogenous. Also, if you are arguing that this was Milne's position, then I have no real reason to question that.

Milne's model being a zero mass version of the FLRW metric, but is, in fact, an isotropic, but nonhomogeneous distribution--an exploding sphere of matter--that would also really impress me.

Definitions shift. When cosmologists talk about the Milne model, they are referring an a zero mass version of FLRW. Now this may not be what Milne himself had in mind, but this is an issue of scientific history, which I'm not that interested in.

If you accept any sort of Newtonian-like universe, then Milne model=zero gravity.

 

[twofish-quant]

Let's also acknowledge another point. If I'm right, it could be embarrassing and humiliating to a LOT of people.

I don't think so. Guess what?

Scientists *love* it when the universe throws people a surprise. If it turns out that the universe isn't decelerating you are talking about enough papers and grant to last the next 20 years.

In fact, if I'm right, cosmoloogy will become in some ways a lot more boring.

You *kidding*? If Milne is right, that means that most of what we thought we known about gravity gets tossed in the trash. Milne in a non-empty universe is inconsistent with GR, which means that every thing involving gravity has to be rewritten.

And then there are the big open questions now. How did galaxies form? We toss out all of the old equations and rewrite everything. How does this effect black holes? Heck, do black holes even exist.

No more searching for Dark Matter.

Not true. If it turns out there is no cosmological dark matter, then we *still* have to look for galactic scale dark matter.

No more great mysteries, about the fundamentals. You'd just be looking for details. Details, details, details. If I'm right, a good part of the sense of wonder about the universe will be gone.

The wonder is all in the details.

While everyone else is following along, figuring out all of the neat principles that are derived from assuming isotropy AND homogeneity, I just am too stubborn to go along with it.

Look outside. If you can point to something out there and say, look this isn't homogenous, then people will listen. Also isotropic and non-homogenous universes have this weird fine tuning problem, which is if the universe is non-homogenous then why did God decide to put is right in the center of the non-homogenity.

If you have a non-homogenous universe, and you end up near the center of that universe, then you need to figure out how you ended up there. If it turns out that we are in the center of an inhomogenity to one part in 10^-3, then you can say it's random. If you look at the universe and it turns out that you are at coordinate 0.000000000000000 then you really have something weird happening.

Anytime you solve one mystery, you have a million new ones. If we establish that we live in the Milne universe, that's only the start of the mystery.

I could happily prepare a series of lectures, if I had someone who wanted to listen, but I really can't prepare a paper to send to a group of people who really really REALLY don't want to hear what I have to say.

It's a tough crowd, but part of being a physicist means learning to "enjoy the fight." It's like entering a boxing ring. If I enter the ring against a heavyweight champion, and he smiles at me, that's not "fun." I want them to try to knock me out. The first time you go into the ring, you'll probably get knocked out in ten seconds. Second time, maybe you can last for a minute. Maybe after a few years, you might actually win a round.

The most important part of getting a Ph.D. is the defense. That's when you present your results to your dissertation committee and they try to tear you to shreds. It's intellectual cage fighting, and they'll only hand you a sheet of paper when you can show that you can defend yourself in the arena.

 

[twofish-quant]

Typically of these articles, I find myself illiterate; unable to get past the first assertion; Equation (1), you see, simply looks wrong to me. It doesn't make any mathematical sense.

The article assumes that the reader knows general relativity, and equation (1) is the GR metric which corresponds to the Milne model of the universe.

If you look hard, I'm pretty sure that there is something out there that presents a simple introduction to GR.

Also, if you want to start thinking about homogenity

https://telescoper.wordpress.com/2011/06/22/cosmic-clumpiness-conundra/

Again, the assumptions of homogenity and isotropy are not mathematical axioms but rather working assumptions that seem to be accurate.

 

[JDoolin]

I haven't worked through the math, so I don't know for sure, but I have no reason to doubt this. However, if that's true then you have a problem since the universe appears to be statistically homogenous. Also, if you are arguing that this was Milne's position, then I have no real reason to question that.

Thank you. But actually, I encourage you to question that! Don't take my word for it; go and actually read "Relativity, Gravitation, and World Structure," if you can find the time. At least skim the chapter where he discusses his differences of opinion with Eddington, and the use of a-priori reasoning. Look at the big diagram at the front of the book. See if what I'm saying is true. I'd like to understand why people argue with me over this. The Milne model seems to be misrepresented everywhere I look, so unless you are looking at the same book I am, you actually DO have reason to question that I am telling you the truth.

 

[JDoolin]

The article assumes that the reader knows general relativity, and equation (1) is the GR metric which corresponds to the Milne model of the universe.

If you look hard, I'm pretty sure that there is something out there that presents a simple introduction to GR.

Also, if you want to start thinking about homogenity

https://telescoper.wordpress.com/2011/06/22/cosmic-clumpiness-conundra/

Again, the assumptions of homogenity and isotropy are not mathematical axioms but rather working assumptions that seem to be accurate.

The type of homogeneity assumed in the FLRW metric is an infinite homogeneous distribution of matter. Milne's model does not claim there should (or should not be) some kind of "cosmic clumpiness" on the small scale. Rather, it predicts increase in the density towards infinity at the extreme periphery of any observer's view.

There's two competing effects at the extreme periphery. You have higher density, but younger universe. The younger universe means we should have less galaxies. The higher density means we should have more galaxies. I would think we should expect to find, in this high density, low age region, a large number of supernovae, but very few fully formed galaxies. But at those distances, 10, 20, 30 billion light-years, we possibly can't see anything as dim as a galaxy anyway.

This is why I'm so suspicious when you say that Milne's model is being tested with the data. You need to be able to point at something that tells me clearly that there is no increase in density at the extreme periphery of the visible universe, and I have strong doubts that we have observations that are that good.

(This paragraph has been edited with Chronos' correction. Thanks, Chronos.) If I were to take a wild guess about what to expect from Milne's model, at the extreme periphery of the universe, I would expect there to be more Type II supernovae toward the edge of the universe, and fewer Type I supernovae. Based on my reading of an introductory astronomy book, it sounds like Type I supernovae come from white dwarfs collecting enough matter to reach critical mass for carbon-detonation, while Type II supernovae are the truly giant stars going supernova. Since the most distant regions are extremely young, the Type II supernovae would dominate, and the older Type I supernovae would be relatively less common.

Also from Milne's Model, there should be a directional difference in the distribution of galaxies. I would expect an asymmetry in the distribution of galaxies that fairly precisely matched the asymmetry in the dipole anisotropy of the CMBR.

Also from Milne's Model, if I am correct that there are secondary accelerations, there should be a local region where Hubble's constant is large and low variance, indicating projection from a more recent event, and a more distant region where Hubble's constant is small, and high variance, indicating an older part of the universe; a projection from a more ancient event.

Now, if none of these expectations are happening, then perhaps we can reject Milne's model based on comparing hypotheses to data. But as long as Milne's model is being rejected because it is a zero-mass model, then we're not rejecting Milne's model. We're rejecting a straw-man.

 

[Chronos]

I believe you had a dyslexic moment there, James. Type I supernova are classified as white dwarf detonations, Type II supernova are the ones resulting from core collapse of massive stars.

 

[JDoolin]

I believe you had a dyslexic moment there, James. Type I supernova are classified as white dwarf detonations, Type II supernova are the ones resulting from core collapse of massive stars.

I corrected it above. Thanks.

 

[JDoolin]

Now I am a trained listener and a professional public speaker (Toastmasters International=28 years) but, unfortunately, I never could figure out what message you were trying to communicate in each of those four modules. Perhaps your written script could be revised to be more coherent and to clearly address the point you want to make. The point is I couldn't find the point.

I have made three more modules. Hopefully you will find these more coherent.

http://screencast.com/t/npv2XLleRl7o. In this module, I discuss why is it that I am multiplying 1 mile per hour times the age of the universe.

http://screencast.com/t/Rie6CCJR8: In this module I discuss the reasons why a kinematic model of the universe has been rejected. From what I have seen, they are all based on straw-man arguments posing as ruductio-ad-absurdam.

If I'm right, http://screencast.com/t/d5rmfSFIr9: In this module, I discuss the particular reasonong which was addressed earlier in posts 45, 47, and 48, 53, 56, 54, in this thread. For your convenience, I am re-posting all the relevant parts of that argument below. You will notice that post 56 and 54 have been reversed, chronologically, in the tradition of the dialectic--in post 56 I had posted a hypothesis, that distant forces were observer dependent, and then later realized that twofishquant had already posted the contradiction to this hypothesis--that indeed the distant forces could, with bookkeeping, be found to be the same.

Do you have some other reasoning, perhaps based on an application of Gauss's Law? I'm asking that because I'm pretty sure that I've seen such an argument made by none other than Einstein himself. However, I don't remember where I saw it; some book I've long since returned to the library (in frustration).

http://www.ast.cam.ac.uk/~pettini/Physical%20Cosmology/lecture02.pdf

Ah, yes, thank you for that article. This was exactly the argument that I was thinking of. I've seen this argument in books, but I had never found it online. I was calling it "Gauss Law" but it is "Birkhoff's Theorem."

While I am essentially in agreement with Birkhoff's theorem, the article you reference is making a major error in its application, (and if I am not mistaken, Einstein made this same mistake, and was perhaps its originator.) If you are calculating the forces on particles A, B, C, and D, it is completely inappropriate for you to draw a circle around an arbitrary observer O, and then treat all of the mass in that circle as though it were a point mass at point O.

It would make much more sense to account for the masses near the objects A, B, C, D, respectively, to calculate the forces that are acting upon them.

(The other major error in the article is equation 2.3... Failure to apply time dilation and the relativity of simultaneity.)

Here's another way of thinking of it...

I have point A. You can argue that all of the forces are balanced at point A, so it doesn't accelerate.

I have point B. You can argue that all of the forces are balanced at point B, so it doesn't accelerate.

AHA! You say, the universe must then be non-accelerating!

But that doesn't work. If I start with point A as my origin, and then look at point B, I find that there is a force at point B pulling it toward point A. But wait, I just showed that the forces are balanced if I take point B as the origin? What gives?

The issue here is that the forces at point B when viewed from point A are *different* from the forces at point B when viewed from point B, because when you change coordinate systems then the forces change. But how can that be? Don't forces stay the same when you change between inertial coordinate systems?

Yes, but from point A's point of view, point B is not an inertial coordinate system, it's accelerating, and because it's accelerating, when you switch between point A and point B, the forces change. From point B's point of view, it's an inertial coordinate system, and A is accelerating. So when you switch between A and B, you have to change the forces to take into account the fact that the coordinate systems are non-inertial.

From A's point of view, there is a force on B pulling B toward A, and there is zero forces at A. Now when you switch to B's point of view, you are a non-inertial reference frame from A's point of view. To make it inertial, you have to subtract the forces that are acting on it. That causes the forces at B from B's point of view to go to zero, and then causes the A to go from zero force to the opposite of what was the force that A sees acting on B.

So if you take any point as the origin, you will see a force of zero for that point, but you will see non-zero forces for points other than the origin.

Now then you see how the universe works. We don't have any infinite clouds, but we have clouds that are "practically" infinite. You take something like the interstellar medium with a one light year cube, and then take a piece that is much, much smaller, and see how you calculate gravity.

Thank you for giving further explanation here.

I still think that ignoring the relativity of simultaneity is a flaw, but I also realize now that I was misunderstanding Einstein's argument.

He was literally saying that the force on a distant particle is an observer dependent quantity, while time is an observer independent quantity. That seems amazing to me, and I will have to think about it further.

And if you do your bookkeeping right, you come up with the same answer. The important thing is to keep track of what reference frame you are in so that you can account for non-inertial effects correctly.

I meant to ask, precisely what bookkeeping is done, so that you all get the same non-zero answer? I can agree that with correct bookkeeping, you should get the same answer, but by my calculation that answer should be zero. Because I don't believe that "correct bookkeeping" is represented by drawing a circle extending out to the radius of the object and stopping (as is done on page 2-3 here: http://www.ast.cam.ac.uk/~pettini/Physical%20Cosmology/lecture02.pdf ) . I think the circle needs to be drawn to encompass a large volume around the object. At least, make the circle large enough to encompass the masses that are in the object's immediate vicinity.

With this sort of bookkeeping, all observers would, indeed, agree that the force on the object would be the same. But the "same value" that everyone would come up with, would be zero.

 

[twofish-quant]

Thank you. But actually, I encourage you to question that! Don't take my word for it; go and actually read "Relativity, Gravitation, and World Structure," if you can find the time.

It's not so much a matter of reading books but rather doing the math.

Also, it *is* known that you can have homogenity rather than isotropy and isotropy without homogenity. Again, it's not a matter of reading books, but just thinking about the situation.

I'd like to understand why people argue with me over this.

I don't think that people are arguing with you over *this*. I think people are arguing with you over something else.

Mathematically, you can have an isotropic universe without homogenity, so what? Big deal.

The Milne model seems to be misrepresented everywhere I look

I don't think it's misrepresentation rather than "definition creep." When cosmologists talk about the Milne model they are talking about a situation in which galaxies move according to the velocities of Milne. Unless you are willing to throw away GR, the only way this can happen is if you have an empty universe.

It's not so much an effort to misrepresent Milne, but rather salvaging something.

 

[twofish-quant]

The type of homogeneity assumed in the FLRW metric is an infinite homogeneous distribution of matter.

Right. But for FLRW to work you just need things to be bigger than the cosmic horizon. If things cut off at 100 billion light years, you get the same results.

But at those distances, 10, 20, 30 billion light-years, we possibly can't see anything as dim as a galaxy anyway.

Yes we can. This is a very simple calculation. Take the absolute brightness of a galaxy. Take the detection limit of our current telescopes. It's a very easy calculation to show that the drop off in galaxies that we see is *real* and not an observational effect.

It's not even close.

You need to be able to point at something that tells me clearly that there is no increase in density at the extreme periphery of the visible universe, and I have strong doubts that we have observations that are that good.

Again, you need to be able to do library research. I've been more patient than most people at "spoon feeding" you data (since this may be of interest to someone else), but at some point you have to be able to do your own library research. (Start with google and early galaxies and dark ages).

And yes, our observations *are* that good. Again, detection limits is something that you can do research on your own. It's a very simple calculation that you can do, and I'll leave it to you as an exercise to figure out how to do it.

It's not even close.

Also from Milne's Model, there should be a directional difference in the distribution of galaxies. I would expect an asymmetry in the distribution of galaxies that fairly precisely matched the asymmetry in the dipole anisotropy of the CMBR.

We don't see this.

Now, if none of these expectations are happening, then perhaps we can reject Milne's model based on comparing hypotheses to data. But as long as Milne's model is being rejected because it is a zero-mass model, then we're not rejecting Milne's model. We're rejecting a straw-man.

No we aren't. For Milne to be consistent with GR you have to have zero mass. Therefore to accept Milne in the absence of matter, then you have to reject GR. Since we have good observational tests for GR, this is something that people aren't going to do lightly.

 

[twofish-quant]

I meant to ask, precisely what bookkeeping is done, so that you all get the same non-zero answer?

Once you have matter that is in an accelerating reference frame then the acceleration becomes a "fictious force".

I think the circle needs to be drawn to encompass a large volume around the object. At least, make the circle large enough to encompass the masses that are in the object's immediate vicinity.

If you have an closed sphere, then the masses that are outside the circle between the origin and the point are canceled out by the mass on the other size of the hollow region.

With this sort of bookkeeping, all observers would, indeed, agree that the force on the object would be the same. But the "same value" that everyone would come up with, would be zero.

Yup, but if you are in a non-interial reference frame then zero force would = acceleration.

 

[twofish-quant]

The younger universe means we should have less galaxies.

Once you get past z=8 or so, we see *NO* galaxies and *NO* stars.

 

[twofish-quant]

I think that you still don't "get it."

On the northwest corner of 1st Avenue and 14th Street in New York City, there is fast food place that sells hot dogs. Now someone argues that there is a French restaurant there.

You cannot by any purely mathematical or philosophical argument refute that position.

It is perfectly mathematically and philosophically possible for there to be a French restaurant at the corner of 1st ave and 14th street. There is no logical contradiction for there to be a French restaurant at the NW corner of 1st and 14th. If you ask me to prove through logical arguments that there isn't a French restaurant there, I can't.

But there isn't. You can go to that location, and see that it's a hot dog joint. If you can't get a plane ticket to NYC, you can go onto google maps, and see that there isn't one there.

Same goes with cosmology. I cannot by pure mathematics or logic show that Milne is wrong. I can just look a the sky and show that he is wrong about how the universe is set up, and most of those measurements were taken decades after Milne was around.

Also, the point of theory is to tell the observers what to look for. You are asserting (incorrectly) that we can't see distant galaxies because our telescopes aren't good enough. Now even if that were true, then the question should be "how good do our telescopes have to be?"

One of the points that I'm trying to make here is that cosmology is not philosophy. It's grounded in observations in much the same way that oceanography is.

 

[Chronos]

My apologies for referring to you as James, Jonathan. I perceive your error as one of philosophy, not science - e.g., I agree with twofish. Cosmology is a conjecture founded on observation. While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

 

[SpiffyKavu]

Golly, this thread has gone off topic. I was going to say that the Fermi telescope has good things to say about molecular hydrogen (not always well traced by CO), but I have a feeling a new topic would be better...

 

[twofish-quant]

While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

And this is a serious, serious philosophical problem when you deal with things like multiverses, pre-event zero, and the anthropic principle stuff.

However, once you get past the very, very early universe, you don't have to worry about these issues.

One problem with the way that cosmology is presented to the general public is that there is so much focus on the "this is *WEIRD* and *SPOOKY* stuff" that people aren't aware that most of cosmology isn't different from oceanography or planetary science, and observing the big bang isn't any different from observing the moon. We know the moon is there because we can see it. We know the big bang happened because we see that too. In some ways, we know more about the formation of the universe than we do about the formation of the moon.

 

[JDoolin]

My apologies for referring to you as James, Jonathan. I perceive your error as one of philosophy, not science - e.g., I agree with twofish. Cosmology is a conjecture founded on observation. While I agree cosmology is still largely a matter of conjecture, it is a conjecture based on observational evidence. Once you leave the realm of observational evidence you enter the realm of metaphysics.

There IS an error of philosophy here, but I don't think it is mine.

The problem is that you are doing philosophy rather than physics. You are treating isotropy and homogenity as if they were mathematical axioms when they aren't.

If homogeneity is NOT a mathematical axiom, then it should not be possible to make a mathematical argument with it as your premise.

Once you start with the premise that the universe is isotropic and homogenous, then at large distances things are going to be flying away from each other at > c, and Lorenz transformation will break down.

The issue here is that your cosmology professor actually IS using the idea of an infinite homogeneous universe as an axiom. He then uses that axiom to draw logical consequences. He then uses those logical consequences to throw out the idea of Special Relativity applied at large scales.

 

[George Jones]

I have closed this thread. There have been several pages of violations of Physics Forums Rules, which I explicitly posted earlier in this thread (post #26).