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The assumption of bounded/unbounded space


pywakit
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The cosmicweb computer simulations are the work of Andrey Kravtsov. Truly wonderful. There are some longer ones which were shown by Smoot in his TED talk. Google "Smoot TED" for a great 18 minute lecture on structure formation by a Nobel cosmologist.

 

As I recall Kravtsov's computer animations show the condensation of dark matter only. Since there is is so much more of it, it dominates the process of structure formation.

 

Penrose gave a talk at Cambridge in 2005 where he explained that the entropy of the gravitational field is defined differently from the entropy of, for example, a gas. In the case of a gas, uniformity = high entropy. The gas spreads out to fill the box uniformly and entropy increases.

In the case of the gravitational field, uniformity is very unstable. Because of universal attraction. Clumping breeds more clumping. It is the opposite of gas intuition. In the gravitational field, uniformity = low entropy. The combination of geometry and matter naturally kinks and curdles and condenses (into cobwebby structure in this case) and entropy increases.

 

I don't agree with all of Penrose talk because some parts were exceedingly speculative but his diagrams explaining entropy and the second law as applied to cosmology were pretty effective.

http://www.newton.ac.uk/webseminars/pg+ws/2005/gmr/gmrw04/1107/penrose/

 

There are some Youtube videos of him giving essentially the same talk somewhere in the US in 2007

This is Penrose' brief illustrated discussion of the entropy concept:

Here is a 9-minute segment where he explains that the entropy of gravity is different

It's a popular non-technical talk. All on a pictorial/intuitive level. Don't watch unless you enjoy or at least have patience with that type of presentation.

Edited by Martin
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By the way Martin ... I just take your word ( and other physicists ) on things like this ...

 

If this number is negative, the finite case is favored. If it is zero or positive then the infinite. The number is called omega-sub-k.

 

My understanding of the math is nearly non-existent. But the over-all conceptualization ... seems pretty simple.


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The cosmicweb computer simulations are the work of Andrey Kravtsov. Truly wonderful. There are some longer ones which were shown by Smoot in his TED talk. Google "Smoot TED" for a great 18 minute lecture on structure formation by a Nobel cosmologist.

 

As I recall Kravtsov's computer animations show the condensation of dark matter only. Since there is is so much more of it, it dominates the process of structure formation.

 

Penrose gave a talk at Cambridge in 2005 where he explained that the entropy of the gravitational field is defined differently from the entropy of, for example, a gas. In the case of a gas, uniformity = high entropy. The gas spreads out to fill the box uniformly and entropy increases.

In the case of the gravitational field, uniformity is very unstable. Because of universal attraction. Clumping breeds more clumping. It is the opposite of gas intuition. In the gravitational field, uniformity = low entropy. The combination of geometry and matter naturally kinks and curdles and condenses (into cobwebby structure in this case) and entropy increases.

 

I don't agree with all of Penrose talk because some parts were exceedingly speculative but his diagrams explaining entropy and the second law as applied to cosmology were pretty effective. Let's google "Penrose Cambridge 2005" and see if we get the talk.

 

Martin, could you please explain how this applies to bounded/unbounded space? My understanding ( and attempts at comprehension ) of space is of 'bound' energy permeating infinity in a generally isotropic manner. Quantum fluctuations ( I think if it as a build up of static charge ) essentialy 'clumps' the 'fabric' of space together temporarily stretching the lines of energy. And space tries to immediately 'unclump' them always working toward a homogenous state. This is how I view the 'expansion' of space. Meaning space isn't actually expanding but working within it's own self-imposed limitations ( properties ) to smooth everything back out. This, as opposed to dark energy acting on space, stretching and expanding it ...

 

Am I way off here? Or is this an equally possible alternative to dark energy?

 

Like the atoms of gas 'trying' to become equidistant ( isotropic ) and gravity wanting to clump them together ( entropic ). A property rather than an outside force ...

Edited by pywakit
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This is in reply to your post #24. I hadn't yet seen your post #27.

Py, you raise some serious epistomological issues. Do we ever know facts about the universe? And if we don't have absolute certainty about it, does this even matter?

 

I'll have to get back to this later. One stance would be to say that scientific theories are not meant to be believed, they are meant to make predictions and to be tested.

 

That is, we do not presume to KNOW about the universe. What we want to do is develop the simplest most Occam models that fit the data, and ideally which turn out to fit NEW data surprisingly well, as it comes in.

 

If a model surprises us repeatedly by predicting new phenomena which are then confirmed and by fitting the data amazingly well, surviving test after test, we might sink into the rut of ACTING as if we believe it and talking carelessly to laymen as if we believe it to be true. But that is not what is at the heart of science. It is not belief, it is making predictions and testing them with measurements/observations.

 

One always retains a corner of skepticism about any model. Eventually any model must be found wanting and must be improved on. Well that is one possible attitude one can take.

 

And so far, working cosmologists are still using essentially the model that Friedman derived (from the 1915 Einstein equations) in 1923 by a process of making simplifying assumptions. And the Friedman model is amazingly successful. Also it is starkly simple. Really really Occam.

Look up wikipedia "Friedmann equations" (they use the German spelling, but he was Russian, so people differ in how they spell it). If you are not into math it may look complicated but as such things go it is the epitome of classic beauty and economy. And it keeps on fitting the data year after year.

 

What I would mean by finite versus infinite is which version of the Friedman model. That is potentially decidable. Which fits better the infinite version of the model or the finite version? I expect that to be decided in my lifetime.

But I do not believe the model. I have no need to believe any description of the universe and its history. I rely on it, in the absence of anything better, for calculation and communication, and it is eminently reliable, but why believe?*

 

This is my personal attitude. (Perhaps I shouldn't bother you with that, but it could make it easier for us to arrive at an understanding.)

 

*quantum gravitists are working on a revised (quantum) version of the Friedman model which does not suffer from a singularity, when that is ready and if it passes the tests then I'll probably switch over and rely on the quantum version wherever they differr significantly. If you want a link to that development, just ask.


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By the way Martin ... I just take your word ( and other physicists ) on things like this ...

I'm a retired mathematician who has become interested in cosmology and in the current developments in quantum cosmology. I'm a sidelines onlooker, not a pro.

Swansont, for instance, is a working physicist.

In cosmology I try to report the mainstream consensus as well as I can.

 

...

 

Martin, could you please explain how this applies to bounded/unbounded space? My understanding ( and attempts at comprehension ) of space is of 'bound' energy permeating infinity in a generally isotropic manner. Quantum fluctuations ( I think if it as a build up of static charge ) essentialy 'clumps' the 'fabric' of space together temporarily stretching the lines of energy. And space tries to immediately 'unclump' them always working toward a homogenous state. This is how I view the 'expansion' of space. Meaning space isn't actually expanding but working within it's own self-imposed limitations ( properties ) to smooth everything back out. This, as opposed to dark energy acting on space, stretching and expanding it ...

 

Am I way off here? Or is this an equally possible alternative to dark energy?

 

Like the atoms of gas 'trying' to become equidistant ( isotropic ) and gravity wanting to clump them together ( entropic ). A property rather than an outside force ...

 

This is your speculation, then. A dynamic space endlessly struggling with matter's tendency to clump. There is no dark energy, but rather space has a kind of will of its own---it is trying to smooth everything back out.

An unending tug of war between two principles.

 

I see no reason anyone should object to your expounding this kind of worldview. You probably won't succeed in getting some mathematically adept person from among the SFN members to formulate your idea mathematically, in the form of equations. I say that just as a note of realism.

 

If you did get it translated into equations then you could see what they say about the expansion history, and redshift data, and the microwave background. You could compare derived numbers with observed numbers.

 

Another thing that could conceivably happen is someone might turn up some earlier work on a model LIKE yours in some essential way, and you might learn of an already existing mathematical formulation.

 

I'm just kind of brainstorming, thinking out loud with no particular direction.

Basically though, at least right at the moment, I find myself unable to respond. It doesn't look definite or quantitative enough to grapple with---a verbal embryo so to speak. Instinctively a hands-off feeling.

Edited by Martin
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Thank you Martin.

 

Nothing happens in a vacuum. More specifically, nothing happens in an absolute void ...

 

In the interests of understanding each other maybe you wouldn't mind if I gave a 'brief history of time' as pertains to pywakit's existence.

 

Before I do, though ... I am already a little familiar with models that don't require a BB. In fact, my model doesn't really require a 'bang' so much as it requires a black hole ( the last black hole ) to reach it's critical mass limit and release it's stored energy. Whether that is a 'reaction' or the limits of angular momentum, it doesn't really matter. The effect is the same. So in short, my model does not conflict with the non-BB models ... as far as where the mass comes from. And I use the term BB in it, because that is easier conceptually. And hopefully makes the transition from the standard model not so abrupt.

 

My approach to science is one of acute suspicion. I love science, but my relationship with scientists is not so loving. I'm kidding, but there are several reasons I would feel this way. Valid reasons. Get to that in a minute.

 

Yes Martin, I am a 'layman'. From a scientist's p.o.v. this is ( understandably so ) a dismissive term. But it assumes facts not in evidence ... such as what that layman's level of understanding and comprehension may or may not be. The assumption is a layman will have little grasp of the subject at hand.

 

I think of all those thousands of 'learned men and women' who must have been so extremely annoyed with Edison for daring to take the accumulated knowledge of electromagnetism and chemistry ( stealing it!) and putting together an electric light bulb. Before they figured it out .... How vexing.

 

I have done exactly what Edison did. I 'steal' from the workers in the trenches. An analogy would be my Corvette. Yes, if pressed I suppose given sufficient time I could build one myself. But it was much easier to simply 'steal' the hard work of so many and just order it from the factory. Yellow, convertible, 6M, and waaay too fast. Lol. I did this in 2000 and I must confess, I have never felt guilty as I blast though the gears.

 

I would feel guilty I suppose about stealing the necessary knowledge to produce my model but for the snubs of scientists through out my lifetime. Nothing you did, of course ....

 

Mankind took a stance a long time ago. We were not here by accident, and neither was our universe, regardless of it's size. Science began as an effort to explain why we were special, as opposed to just 'explaining'. It is easy to assert this as nearly all scientists of the day professed a belief in god, or some higher ( cognitive ) authority. There is nothing rational, or scientific about this belief. For me, it's been like living in a mad-house with no walls for half a century. EVERY body is clearly irrational. Lol. Faith is just a manufactured term for 'irrational belief with absolutely no supporting evidence'. This was still very evident when I was a child of six some fifty-one years ago.

 

I was born without a 'belief CAPACITY'. Raised on a devoutly christian island, this was a nightmare. Like living in the 'twilight zone'. Actually very frightening. But this is the basis for my arrogance and obnoxious behavior. And also how I came to understand the universe as I do.

 

Martin, I learned very quickly that adults can be very very wrong even as they insist they are not. In sunday school I made the mistake ( at age 6 ) of questioning god's word, his will, his level of rationality, his judgements, and his very existence. I had already grasped that there was no proof that he existed by the time I was 4, so for me, this relegated him to 'tooth fairy' status. Maybe he DID exist, but the burden of proof was on the believers. And they weren't offering any.

 

My 'mistake' caused the islanders to make me a pariah for more than 5 years. No child was allowed to speak to me for fear I might infect them with my satanic thoughts. No bs. This is what happened. I was beaten so many times I can't count. My family hated me for they were now suspect too in the eyes of the islanders.

 

This incident took place at the beginning of the summer, and as none of my family could stand the sight of me, and I was likely to be beaten if noticed, I requested permission to sleep outside for the summer. Permission granted. ( we lived on a 100 acre farm, btw. )

 

Overhead each night was a brilliant expanse of stars. ( no streetlights, no neighbors ) I was desperate for relief from my nightmare, and I would lay under the stars and beg some alien race to come get me ... Pathetic really. But the flip side was I spent a great deal of time contemplating the universe. The real one I could see as opposed to this mythical one everyone believed in.

 

I worked out the 'transit method' that summer. Trying to explain it to adults who were certain that god put us here, and there were no other planets in the universe ( which I already visualized as 'infinite' ) was an exercise in futility. Not to mention further beatings. But Martin ... time proved me right. And everyone else wrong. My conclusions were not based on faith, or my own desperate wishes. They were based on 'not' having faith. 'Not' being blinded. Logic said .... there are all those stars. They are suns. If our sun has planets, then other suns do too.

 

But science did not 'officially' agree with me. Yes, there 'probably were' but "We can't know for sure, and we never will because the light from stars is much too bright to ever see a non-radiating object next to it."

 

It took me 4 years to get up the courage to write to NASA. But 'somebody' had to tell them how to find planets because they were clearly not figuring it out for themselves. I ws unaware, by the way, that Struve had written a short paper on this method in 1952 ... and science ignored him, too. NASA saw no need to write me back and thank me, nor even a nice note to encourage my further interest in astrophysics ... and this just told me that even the brightest of scientists can blind themselves to 'truth'.

 

Martin, I have been correct in every prediction I have ever made regarding the 'big' picture. For 50 years. All the 'adults' were wrong. Now that I'm all grown up, is it so hard to see where my rather antagonistic attitude comes from? I have very high confidence in my ability to look at big pictures. 50 years of being correct does that to you. 50 years of scientists being 'incorrect' ( at least as far as the big picture goes ), or at best being afraid to commit in the face of ( in my view ) overwhelming evidence does not make me easily intimidated when very nice, well-intentioned scientists like you tell me I lack sufficient 'academics' to understand how our universe operates.

 

I did not just 'think up' my model. Out of a 'void'. I have stolen every bit of pertinent information I could ( and still do ) from all you nice scientists, to create this model. I am not afraid to commit, nor am I afraid to suffer the sometimes abusive and dismissive reactions from 'learned men'. It is fully expected, and completely understandable that you or others would feel the way you do.

 

I have much to learn ... and some things I will clearly never grasp. But that doesn't matter to me when I'm hitting 150 ( yikes! ) in my vette. I am confident in the underlying physics, and engineering ( and genius ) that went in to building it. I am equally confident in the genius that unravelled astronomy.

 

You said you may 'jump ship' soon. This just further illustrates my point. There is no real, current consensus on the structure and processes that form the physical unverse we occupy. There are 1000 different interpretations from the observations we have to date. You claim Friedman's universe has done a wonderful job. Other very respected scientists do not agree. I think my model is more 'Occam' than the standard model, and that all observations and experiments, and math support mine just as well. In addition, the other models out there require some pretty serious 'magic acts' to solve their deficiencies. My model requires no such magic. No superphysics. No 'hypotheticals' that conflict with known laws and properties of space.

 

Yes, I am very confident. I don't think I am your standard 'layman'. But I still reserve the right to say .... Oooops. I was wrong. It would be tough, but I would survive it.

 

Please forgive my lack of economy in expressing this to you. And please forgive my attitude. It is not directed at you, or any individual. Scientists don't have a lock on 'blindness'. I am just as capable of being wrong, too.

 

I hope we can continue the debate. I hope we can both understand each other better now. I really do understand your viewpoint. I just don't necessarily agree.


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Couple more points I forgot. On the 'methodology of science'.

 

50 years ago, as I lay on the grass and stared up at the beautiful expanse of stars, I would think about what the scientists said.

 

"There 'might' be no other planets outside our solar system. We can not know for 'sure'."

 

This was complete insanity to me. We knew they were stars. We knew there were other galaxies of stars ... thousands of them. This meant that at the very least there were going to be TRILLIONS to QUADRILLIONS of stars in the KNOWN visible universe.

 

But our star 'may' be the only one with planets. Hmmm. Really. So what you are telling me is there are quadrillions of suns in the universe. And just one has planets. The rest? Just hanging out by themselves ....

 

This was not 'science'. This was religion. The only rational, reasonable, and logical assumption would have been ...

 

Our star has planets. We can't be sure at this time how our planets came to exist, but what we have observed to date is that there is very likely a physical process involved. Therefore the probability of all those other stars NOT having planets is effectively zero, unless ours were put here by some deity. Since we have zero evidence of that either, this is the model we will use until proven otherwise.

 

Taking this stance would not have hampered scientific inquiry in any way. In fact, it might have sped the process up considerably. And there would have still been left open the possiblity of observations disproving that model.

 

But religion stopped them. All of them. From treating the problem truly objectively.

 

It was one thing to understand the mentality of christians and their 'special' status in the universe. Quite another to understand the mentality of scientists. To me, it was inexcusable that science could take such an illogical, and irrational stand .... all the while claiming the infallibility of scientific methodology.

 

Something wrong with my cognition here?

 

And by the way .... how do you think the religions of the world will react if/when science tries to tell them that we have sufficient evidence to assume an infinite universe .... filled with an infinite amount of matter/energy? I don't think they will like it very much at all ....


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If in fact, we come down on the side of an infinite universe, generally isotropic, and therefore an infinite amount of matter/energy then we can make some assumptions based on measurements already taken of space around us.

 

There will be an infinite number of replicas of us in an infinite universe. There may be other mechanisms ... other laws of physics in play ... for other universes, but essentially whatever CAN happen, will happen an infinite number of times.

 

We will also be required to take the stance that the universe is eternal. To do otherwise would be to illogically, and irrationally presume infinity ( and from this 'moment' forward ... eternity ) began with us.

 

Reason sound so far?

 

CMBR. This is the measurement that would 'prove' my model, I believe. As you know, it is a closed loop. If the universe is infinite, and generally isotropic, then there will have been an infinite number of 'bangs' in all directions in the past. And the properties of space would apply universally. If the universes are 'leaking' at all ( can't have just one with this 'defect' in infinity ), then we would be getting CMBR from across the 'voids'. ( Because photons would be travelling throught the medium they always travel through. It doesn't matter how far it is when you have been travelling for eternity ...)

 

Anyway, the red shift would show this, would it not? I don't think it does. The argument that space itself is expanding collapses with an infinite/eternal universe. For that would mean a beginning. A starting point. If it's going in one direction now ( expanding ) it would shrink going back in time, to an infinitely small point.

 

Again, all we know is galaxies are moving away at accelerating velocities. It doesn't have to mean space is actually expanding. If there is no leakage, it ( our BB ) is a closed loop. To the last photon. The idea that photons will simply be absorbed back into space does not seem quite rational. We have captured photons that are over 13.5 billion years old ... that have stumbled through all kinds of gasses, gravitational fields, and matter on that journey. They seem rather hardy, don't they? I don't see any reason why they will just go 'poof' in a few more years. Particles, yes. Photons, no.

 

This seems a much better adjustment to the standard model than any others.


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Martin wrote:

 

What I would mean by finite versus infinite is which version of the Friedman model. That is potentially decidable. Which fits better the infinite version of the model or the finite version? I expect that to be decided in my lifetime.

But I do not believe the model. I have no need to believe any description of the universe and its history. I rely on it, in the absence of anything better, for calculation and communication, and it is eminently reliable, but why believe?*

 

I agree with you. I am only trying to suggest a better model than what we have. One that makes no contradictions. I don't 'believe' in my model either. It just seems to fit the evidence better, and would be no less reliable.


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I wrote:

Anyway, the red shift would show this, would it not? I don't think it does.

 

However, if the red shift showed CMBR 'leakage' from outside our local universe, then that would indicate either one-way universes, or an infinite universe so isotropic that each local universe gains exactly the same mass that it loses allowing for continuing BB/expansion/collapse/BB cycles.

 

But again, CMBR redshift measurements do not indicate leakage from other universes.

Edited by pywakit
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...

CMBR. This is the measurement that would 'prove' my model, I believe. As you know, it is a closed loop. If the universe is infinite, and generally isotropic, then there will have been an infinite number of 'bangs' in all directions in the past. And the properties of space would apply universally. If the universes are 'leaking' at all ( can't have just one with this 'defect' in infinity ), then we would be getting CMBR from across the 'voids'. ( Because photons would be travelling throught the medium they always travel through. It doesn't matter how far it is when you have been travelling for eternity ...)

 

Anyway, the red shift would show this, would it not? I don't think it does. The argument that space itself is expanding collapses with an infinite/eternal universe. For that would mean a beginning. A starting point. If it's going in one direction now ( expanding ) it would shrink going back in time, to an infinitely small point.

...

 

Py, I have highlighted what I think is a mistake in reasoning. Accepting present expansion doesn't mean assuming a beginning. Because the expansion doesn't need to extend that far back.

 

When people apply quantum mechanics to the law of gravity one result that comes up (in some of the analysis) is that quantum effects make gravity repel at very high density (like what is conjectured around big bang 13 some billion years ago.

 

That could mean that the bang was a bounce. A contracting phase reached a high enough density that the force reversed and started an expanding phase.

 

I don't want to elaborate further right now, but logically one cannot infer back in time to an "infinitely small point."

 

The most revolutionary thing going on in cosmology, at present, is the research called quantum cosmology. If you want get a taste of it, here is a keyword search in a research publications database called Spires:

 

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2005&FORMAT=WWW&SEQUENCE=citecount%28d%29

 

Please let me know if your computer can't get the listing. I have set the date so only papers from after 2005 show up and I have set the ordering so that the most often referenced papers appear first. These are typically the ones that other researchers consider most important. Ground-breaking research tends to be referenced more often.

Edited by Martin
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It's not really a request. "No" is not an acceptable response to a call to follow the rules.

Cap'n effectively asked me to change my personality and who I am. He did so in response to a pretty light post I made in defense of Martin. I stand by my response, and will continue to do so no matter how many times Cap'n asks me to "Please try to be nicer."

 

Cap'n didn't tell me I'd broken a rule. He told me that my good intentions sometimes have negative impacts. I understand that, but I also won't be changing who I am or how I respond to certain people any time soon.

 

Seriously. Let's put things in perspective here for a moment, shall we guys? This is what I said:

 

 

Py - Chill out. I'm frankly surprised that Martin has bothered wasting any time at all with you. The least you could do is to lose the attitude and see about improving your own understandings since he has offered to help in doing so.

 

 

If that's over the line, then your priorities are all out of whack.

Thanks.

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I think you need to remember that your words exist to achieve a goal, such as convincing someone or making a point, and sometimes your tone works against that goal. Your post was highly unlikely to achieve its goal because its tone was far more likely to irritate pywakit than to improve his attitude, and we know how things go when posters get personal.

 

Please. I made my post with the intention of keeping this thread on track. Let's not ruin that.

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My apologies. I just didn't think my post was out of line. I should perhaps have responded more clearly to that effect. I agree though that this is all rather unnecessary, off topic, and would prefer to move on so the core discussion can continue.

 

Sorry to the OP and other readers for the distraction. The tone of the discussion has absolutely changed for the better, and that was the goal I'd hoped to achieve.

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Py, I have highlighted what I think is a mistake in reasoning. Accepting present expansion doesn't mean assuming a beginning. Because the expansion doesn't need to extend that far back.

 

When people apply quantum mechanics to the law of gravity one result that comes up (in some of the analysis) is that quantum effects make gravity repel at very high density (like what is conjectured around big bang 13 some billion years ago.

 

That could mean that the bang was a bounce. A contracting phase reached a high enough density that the force reversed and started an expanding phase.

 

I don't want to elaborate further right now, but logically one cannot infer back in time to an "infinitely small point."

 

The most revolutionary thing going on in cosmology, at present, is the research called quantum cosmology. If you want get a taste of it, here is a keyword search in a research publications database called Spires:

 

http://www.slac.stanford.edu/spires/find/hep/www?rawcmd=dk+quantum+cosmology+and+date%3E2005&FORMAT=WWW&SEQUENCE=citecount%28d%29

 

Please let me know if your computer can't get the listing. I have set the date so only papers from after 2005 show up and I have set the ordering so that the most often referenced papers appear first. These are typically the ones that other researchers consider most important. Ground-breaking research tends to be referenced more often.

 

Yes, of course to your first statement. However, I was tired and not thinking clearly. As I was formulating the paragraph my original intent was to use the word 'could', as opposed to 'would'. Then I forgot what I was talking about. Lol. I have been following a lot of models, and I am a little familiar with the 'possibility' of gravity repelling at high densities. There seems to be no evidence of such an anomaly, no observations that bear it out, and as yet no real consensus on it's 'probability'. And that is 'one' result. I believe the other result is the opposite.

 

The model(s) you describe does not adequately address other issues such as hydrogen/helium levels, nor CMBR. It does seem to create the need for another mechanism for the creation of CMBR in the first place. So in short, I have a few problems with any 'bounce' theory. Please correct me if my information is inaccurate.

 

It also does not deal satisfactorily with entropy, or isotropy ( I think ), the loss or gain of mass per bounce ( potentially 'running out of steam' ) in the local universe, and it does not offer a satisfactory mechanism for the expansion to reverse.

 

So this is, I suppose, why I would have subconsciously just dismissed the 'bounce' possibilty, and claimed an absolute. I was in error to do so.

 

Either way, of course, I do not think space allows 'infinitely small' any more than it allows 'infinitely big'. Just because math produces an infinite answer does not mean that the universe must obey our math. The fact is, we continue to refer to a singularity as 'infinitely small' when we have zero evidence of any such thing occurring in the universe. Extremely small, yes. But to be infinitely small, I think it would have to contain an infinite amount of mass. And we don't have an infinite amount laying around. Or there would have to be an arbitrary 'trigger' point where gravitational collapse can not be stopped, or reversed. Or it would have to have a maximum limit of mass, a minimum limit to size, then it would have to 'shunt' mass somewhere else. It sure doesn't seem to be returning the information to the universe. Yet. ( Hawking radiation may or may not be a real phenomena, but I don't think we are going to get rid of any black holes that way.) And we have yet to see a black hole turning inside out. Thankfully.

 

It appears that the properties of space become inflexible at some point. It allows bending and stretching just so much, then it puts the bakes on. A photon is the easiest ( possible ) evidence of this. We assume the photon's max velocity is 300,000 kps based solely on it's observed speed. I would disagree with this assumption. It is just as likely that a photon has 'infinite' velocity potential, but the lines of energy ( the medium ) in space that it travels in do the limiting.

 

I will check out the latest from the resource you have provided. And thank you for being such a gentleman. I hope I can reciprocate ...


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Martin, tell me if this experiment makes any sense. Maybe I am looking at this the wrong way.

 

But this is what I would do:

 

Since I think it is the 'homogenizing' property of space that makes the nitrogen released in a vacuum rush to equidistance, as opposed to a 'repelling' force of the atoms ( pulled, rather than pushed ), I would take the formula that expresses the accelerating velocity of that 'repulsion' and apply it to various ages of galaxies we know to be receding from us. I would then also apply it to the local group of galaxies to see if their gravitational attraction is in any way affected by space's 'tugging'. Maybe all this has already been done ... If so, my apoplogies.

 

Anyway, I would think we would find a correlation between/among these phenomena.

 

Bad thinking?

 

I suppose so, since it could just as easily be attributed to 'dark energy'.

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...But this is what I would do:

 

Since I think it is the 'homogenizing' property of space that makes the nitrogen released in a vacuum rush to equidistance, as opposed to a 'repelling' force of the atoms ( pulled, rather than pushed ), I would take the formula that expresses the accelerating velocity of that 'repulsion' and apply it to various ages of galaxies we know to be receding from us. I would then also apply it to the local group of galaxies to see if their gravitational attraction is in any way affected by space's 'tugging'. Maybe all this has already been done ... If so, my apoplogies.

 

Anyway, I would think we would find a correlation between/among these phenomena.

 

Bad thinking?

...

 

Not bad thinking. It strikes me that you are here thinking like Aristotle rather than like Ludwig Boltzmann. Aristotle might have explained the observed effects of gravity by saying that things have a "downwards going" property---an innate tendency to go down. And if he had imagined air molecules he might have attributed to them a "repulsive" or a "spreading-out" tendency.

 

But Boltzmann did not say that gas molecules repel each other. He did not attribute any innate dispersive tendency to them. He thought more deeply.

 

There are more different ways they can be spread out. Boltzmann imagined what is called the multidimensional phase space of the molecules---where you describe the current situation by listing the position and velocity of each molecule.

There is a bigger volume of phase space where they are spread out.

 

If there are 100 molecules in the box, and you need 6 numbers to describe each (3 to tell position and 3 to tell speed and direction) then a point in "situation space" (called phase space) is simply a list of 600 numbers.

 

There is more volume in this 600 dimensional space that has them spread out. If you pick a random point, a random list of 600 numbers satisfying whatever overall conditions like temperature, the chances are very high that it will describe a spread out situation.

 

So Boltzmann did not NEED to postulate a dispersive tendency in molecules to want to get away from other molecules. He flourished in the second half of the Nineteenth---Old Vienna---the Austrian Empire. He was a major force in getting other physicists to accept the idea of atoms and molecules. One of the greatest, like Aristotle or Archimedes. He founded thermodynamics.

 

I've oversimplified and left out stuff but tried to suggest the main idea. If you divide up the phase space (the range of situation list possibilities) into regions, where each region corresponds to some macro conditions like of temperature and pressure----that is called 'coarse-graining' the phase space.

 

Entropy is the log of the volume of a given coarse grain, a given region. Because you only care about the macro conditions, like pressure temperature, that specify a region. You don't care how those conditions are implemented down at level of individual molecule position and motion.

 

Boltzmann was able to give a mathematical definition of disorder. To quantify disorder so that one can track and predict and make equations to govern its evolution. This was the first time such a thing was done on our planet. Two great Viennese: Boltzmann and Mozart.

 

The dispersion of galaxies is, as far as we know, NOT analogous to the dispersion of gas molecules in a box.

However there is an Indian named Thanu Padmanabhan who has been trying to persuade people that the theory of geometry (General Relativity) can be based on thermodynamics. That is, that the theory of gravity (which describes expansion of distance) can be derived from a more general thermodynamics. Padmanabhan has written a dialog about this (like Galileo used to communicate radical ideas in the form of dialogs or imaginary conversations.) It sounds borderline but one must allow that Padmanabhan might turn out to be right. It is within the realm of possibility. However as far as we now know the geometrical expansion of distances between stationary points has nothing to do with matter-thermodynamics.

 

In case anyone is interested, here is Thanu's dialog:

http://arxiv.org/abs/0910.0839

(proceed at your own risk).

Edited by Martin
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Uh oh. Thinking as a philosopher rather than a scientist. As much as I would like to consider it a compliment to be compared to Aristotle, he was, after all, rather ignorant as to the true functions of the universe.

 

So yes. Bad thinking. Lol. But you are kind.

 

So now I must ask the obvious. "As far as we know......" Have there ever been any studies of this nature? Do we have the capability of making such comparisons? And perhaps I fail to glean all the information contained in your post. I was more concerned with the INCREASING RATE OF ACCELERATION of the atoms from initial release to isotropic positions, rather than measurements of a 'static' state of being.

 

We know that the galaxies farthest from us ( in time and space ) are 'moving away' faster than those closer. My contention is the atoms leave the bottle at a certain velocity and quickly accelerate. They go from 'zero' to (x) ... then back to 'zero' again once equidistance ( general isotropy ) has been achieved within the box.

 

How long does it take to reach maximum velocity? The idea here is space takes a given volume/number of atoms from 'rest' and pulls them apart. The more massive ( and therefore, the stronger the gravitational force ) the structure, the longer it takes to accelerate that mass. As before ... even if there was a correlation, it could be attributed to dark energy.

 

More bad thinking?


Merged post follows:

Consecutive posts merged

Furthermore, if we removed the walls of the box, giving the atoms infinite space in which to disperse, what 'would' be the maximum velocity achieved? I don't think there will be a point where the atoms say "Ok. We are far enough from each other now." will they ... Point being, there is no 'repulsive' force. The atoms are much too far apart to have any further possible relationship/interaction. ( communication )

 

The other point being ... it seems illogical that 'space' is actually expanding between any two atoms, anymore than 'space' is expanding between galaxies.

Edited by pywakit
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In the box thought experiment, the box sits in a static geometry. We don't put General Relativity into the picture (which allows geometry to change dynamically, so that distances between stationary points can change.)

 

...

Furthermore, if we removed the walls of the box, giving the atoms infinite space in which to disperse, what 'would' be the maximum velocity achieved?...

 

No gain in velocity. Since there is no repulsive force. Remember we are thinking about this in the static framework of conventional Euclidean geometry. This is good on ordinary time and distance scales. If we were thinking in terms of cosmological scales. Thinking of the molecules behavior over billions of years time and millions of lightyears distance, then Gen Rel geometry would complicate the answer. there would be noticeable effects of nature's dynamic geometry.

 

 

But now you begin putting Gen Rel into the picture. You start talking about expansion cosmology.

The other point being ... it seems illogical that 'space' is actually expanding between any two atoms, anymore than 'space' is expanding between galaxies.

 

"Space expanding" is just what they tell children and laymen. It is not a good way to think (IMHO) and it is not what the Gen Rel math says. In Gen Rel there is no substance called space, there is only geometry and the geometry is dynamic and evolves according to certain rules.

 

Since there is no substance called space, it is a bit confusing to speak of it as expanding. However spatial geometry can change with time. That is the whole point of "non-Euclidean". Nature does not provide us with exact static Euclidean geometry. When and where the geometry looks Euclidean that is because something CAUSED it to adopt that pattern. Gen Rel is the theory of geometry and what causes it to be the way it is and what causes it to change. It is a successful theory that has passed many tests. Euclidean static geometry is wrong, we know. Gen Rel dynamic geometry is remarkably close to right except in certain extreme circumstances, and those are being worked on as we speak.

 

To get a useful idea of distance in Gen Rel, one has to specify how one wants to define the present moment. Which events are simultaneous. How you do that is to some extent arbitrary, although working cosmologists dealing with real data have agreed on a very natural-seeming way to do it, so it doesn't look arbitrary.

 

Once one has specified how to slice the 4D history into slices of simultaneous events, one can give a meaning to distances.

 

For a working cosmologist, the CMB background is the ancient light from the collective matter when it was approximately evenly spread out. Like a hot gas. Before it began to condense into blobs and start falling towards other blobs.

 

So we can define that you are STATIONARY relative to the bulk matter of the universe if you are stationary relative to that ancient light.

 

But that is very easy to check. If you are not moving the CMB should have the same temperature in all directions. If you are moving in some direction then you should see a doppler hotspot ahead of you (a blueshifted patch of sky) and a doppler coldspot behind you (a redshifted patch on the microwave map).

 

So we can define who are the stationary observers throughout the universe. They are the ones for whom there is no doppler hotspot in their microwave sky. They are at rest with respect to the ancient uncondensed matter and its ancient light.

 

OK do now we can start doing geometry. We can take two widely separated stationary observers and see if the distance between is changing with time. There is no reason to suppose it wouldn't change. Nature does not subscribe to Euclid's prescriptions.

And we can, in effect, measure the angles of very large triangles between stationary observers and see what they add up to. There is no reason to suppose that they would always add up to 180 degrees.

 

Py, in your post I quoted where you say something isn't LOGICAL. I'm not sure what you mean. I might disagree. I would say that, knowing what we do about geometry, it is not logical to expect the distance now between two stationary observers to be the same as the distance sometime later.

Or sometime earlier.

Something similar can be said about very large triangles and 180 degrees.

 

At small scale we don't have to worry about these things because the differences with Euclidean are undetectable, or just barely detectable. It would be nonsensical to worry about such small differences

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Martin, you will only make me appear more obtuse if you drag me down this road. Lol. Ok. How shall I respond? My understanding of GR is that is describes the properties and relationships of matter/energy in the established medium we call 'space'.

 

I am always a little suspicious when science claims an absolute. "Since there is no substance called space ... " We are certain this statement is true because .... ?

 

We can see ( through measurements ) that some force ( dark energy ) is acting on the 'medium'. We seem to now be claiming this as an absolute. But that is an assumption based on another assumption. That space has no 'substance' of it's own. But does it really follow? The reality is ... there IS a measurable force at play. It seems equally likely that space DOES have substance. This is what logic tells me. What I am trying to do is pin down which explanation best fits the evidence.

 

"No gain in velocity." Hmm. I don't think I am being clear here. Once released from the bottle the atoms charge out to become equidistant inside the box. They are changing their positions in space. That change does not occur instantaneously. What I am trying to establish here is that 'something' is causing the atoms to change position. Whether repulsive or not. And that the relative velocity to distance may be an important measurement. There is a force at play here.

 

The visual I would use would be a cubic room ( vacuum chamber ) 100x100x100 ft. At one end, centered on the wall we have the nozzle for the nitrogen bottle. We manage to release 100 atoms from the bottle simulataneously. What are the velocities/corresponding positions of the atoms relative to the nozzle and each other at 1/1000th of a second? 10/1000ths? 100/1000ths? What is the maximum velocity the atoms will achieve before settling into isotropy? How quicly to they achieve isotropy? What is the 'braking' mechanism once they achieve it? Do the atoms 'run past' isotropy and then 'readjust' their relative positions?

 

You say that the behavior of nitrogen atoms can not be applied to the behavior of galaxies, and what I am suggesting is that there could be a relationship, but we haven't figured it out yet because we haven't studied and compared the numbers, or we lack the capacity to make such comparisons.

 

I sincerely hope I am not giving you a head ache ... If these are stupid questions just tell me to shut up.

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... In Gen Rel there is no substance called space, there is only geometry and the geometry is dynamic and evolves according to certain rules.

 

Since there is no substance called space, ...

 

In General Relativity, there is no substance called space.

The subsequent discussion assumes we are in the context of Gen Rel.

 

I can't keep putting the words "in Gen Rel" into each sentence.

 

So please keep the context in mind, as a qualification.

 

No absolute claim has been made that "there is no substance called space. What I'm saying is that in the mathematical framework we use in describing the universe, there is no substance called space.

There is no mathematical entity in the theory that expands----there are distances, describing geometry. And of course there is matter.

 

So when people popularize---when they talk about the current models of the universe in layman terms---they actually give a distorted impression when they say "expanding space" as if it were a substance.

 

THERE ACTUALLY COULD BE SUCH A SUBSTANCE, like an "ether". But there is not such a thing in the theory. Therefore it is a miscommunication.

 

I am always a little suspicious when science claims an absolute. "Since there is no substance called space ... " We are certain this statement is true because .... ?

 

Sorry if I wasn't clear enough. I was not claiming an absolute certainty that there is no substance that expands. Such a thing might be discovered one day. But in Gen Rel, the basic math model we use in cosmology to describe and predict, to organize and fit data, there is no such substance. And popularizers mislead people if they speak as if there were.

 

Intentionally or not, you were giving scientists a bad rap, in the sentence I quoted. Or scientists, or just me. Whoever the suspicion was being directed at.

 

A lot of people (not necessarily yourself) seem to have an anti-science bias. And they tend systematically to mis-state what scientists are trying to say, to make the message look doctrinaire, and cast doubt on its credibility.

This is a kind of straw-man debating technique where one misrepresents what another person is saying in order to discredit it. When this sort of thing happens to me, I reflect that it is often my own fault for not being clear enough.

 

Other times I think the main fault is with popularizers. There are scores of them, although the only names I can think of at the moment are Stephen Hawking and Brian Greene. They are doubtless not the worst.

 

What you said before did not involve a nozzle. You said

 

...Furthermore, if we removed the walls of the box, giving the atoms infinite space in which to disperse, what 'would' be the maximum velocity achieved?...

 

Now you imagine a surrounding vacuum chamber a 100ft cube

So a little box with 100 molecules sits inside the big cubical vacuum chamber. Somehow, in the twinkle of an eye, you instantaneously "remove the walls of the the box" as you said.

Now the atoms have more freedom to roam about.

 

I told you I thought there would be no change in velocity. In other words no change in the temperature of the gas.

The random thermal motion just has a larger scope.

 

However you are now asking about something different. You now want there to be a nozzle. A channel in which a pressure gradient is temporarily maintained and pressure converted into directed velocity.

 

I'm not sure how this is supposed to relate to galaxies. Maybe you should refine the image and try to make it relate to the universe in some way.

 

You should probably note that relative to the background, galaxies are nearly stationary. They have random motions which, when possible to measure, turn out to be a few hundred km/second at most. Whereas light goes about 300,000 km/second. That is, galaxies move on the order of 1/1000 of the speed of light.

 

However most of the galaxies which we can see with, say, the Hubble telescope, are receding from us at more than twice the speed of light. That is, the distances from us to them are increasing at over twice 300,000 km/second.

 

Recession is not the same as ordinary motion. It does not get you closer to anywhere. It has no destination. It is not limited by the Special Relativity Speed Limit. It is just a rate of distance increase.

 

A distant galaxy may give you the impression that it is moving and going somewhere. But it is not getting closer to anything. There is nothing ahead of it that it is getting closer to. It has no direction of motion. It is getting farther away from everything. It has no momentum associated with this change in geometric circumstance. Distances from it, as from us, can change at rates exceeding c. Because that change is not ordinary motion.

 

So somehow you want to relate this to gas in a box? It sounds like an analogy with very limited applicability. Useful as a visualization but not something that would make for a reasonable numerical comparison.

 

BTW Happy New Year! I hope we all learn some new things in 2010 and that the experience is on the whole pleasant.

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Sorry Martin. I am not the most tactful human alive .... Neil DeGrasse Tyson ( a very patient man, in my experience ), Seth Shostak, and Frank Drake come to mind also.

 

Thank you for attempting to straighten me out on GR. Clearly I have misunderstood it's scope, and limitations. I will study harder, I promise.

 

As grumpy as I can get with science, I am not anti-science at all. I think you must know this by now. Quite the contrary. I fully expect science to explain all the mysteries of the universe in time ... Like you, I hope within my life time.

 

I would use Dark Energy as an example of my 'suspicion'. I have read 'theoretical' models that seem to approach it's existence as a 'given' ... then building on or incorporating DE into the model. This is annoying to me, as it only lends further authenticity to an unproven 'hypothetical'. Much the same with Hawking Radiation. Not all respected scientists are in agreement with either of these, as I am sure you know.

 

It is wrong of me to cast aspersions on you or any other scientist. It isn't my intent.

 

You wrote:

 

I was not claiming an absolute certainty that there is no substance that expands ...

 

We may be talking at cross-purposes here. I don't think space DOES expand. What I am asserting is that space is an energized structure without form ( infinite ), but with certain properties, and limitations. And these properties are possibly mis-identified as an outside force ( DE ) working on both it, and matter. And that matter/energy in the visible local universe are an integral ( borrowed energy ) and transitory part of a previously existing ( eternal ) structure.

 

My main goal is to devise, or have someone else think of a way to devise, experiments that would tend to infer my model as opposed to the current standard model, and others waiting in the wings. At the same time I wait patiently for someone to say ... " Ok, jerk. Here's your critical flaw!" Lol. In which case it's back to square one.

 

In the meantime, I just maintain my desire to contribute something meaningful to Mankind. I could have less lofty goals, I suppose ... but if you are going to dream, you might as well dream big.

 

Your patience rivals Dr. Tyson's. Thank you again.


Merged post follows:

Consecutive posts merged

To everyone who has participated ... I hope 2010 is a satisfying, and productive year for you.

 

Thank you for being so patient with me ...

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In General Relativity, there is no substance called space.

The subsequent discussion assumes we are in the context of Gen Rel.

 

I can't keep putting the words "in Gen Rel" into each sentence.

 

So please keep the context in mind, as a qualification.

 

No absolute claim has been made that "there is no substance called space. What I'm saying is that in the mathematical framework we use in describing the universe, there is no substance called space.

There is no mathematical entity in the theory that expands----there are distances, describing geometry. And of course there is matter.

 

So when people popularize---when they talk about the current models of the universe in layman terms---they actually give a distorted impression when they say "expanding space" as if it were a substance.

 

THERE ACTUALLY COULD BE SUCH A SUBSTANCE, like an "ether". But there is not such a thing in the theory. Therefore it is a miscommunication.

 

 

 

Sorry if I wasn't clear enough. I was not claiming an absolute certainty that there is no substance that expands. Such a thing might be discovered one day. But in Gen Rel, the basic math model we use in cosmology to describe and predict, to organize and fit data, there is no such substance. And popularizers mislead people if they speak as if there were.

 

Intentionally or not, you were giving scientists a bad rap, in the sentence I quoted. Or scientists, or just me. Whoever the suspicion was being directed at.

 

A lot of people (not necessarily yourself) seem to have an anti-science bias. And they tend systematically to mis-state what scientists are trying to say, to make the message look doctrinaire, and cast doubt on its credibility.

This is a kind of straw-man debating technique where one misrepresents what another person is saying in order to discredit it. When this sort of thing happens to me, I reflect that it is often my own fault for not being clear enough.

 

Other times I think the main fault is with popularizers. There are scores of them, although the only names I can think of at the moment are Stephen Hawking and Brian Greene. They are doubtless not the worst.

 

What you said before did not involve a nozzle. You said

 

 

 

Now you imagine a surrounding vacuum chamber a 100ft cube

So a little box with 100 molecules sits inside the big cubical vacuum chamber. Somehow, in the twinkle of an eye, you instantaneously "remove the walls of the the box" as you said.

Now the atoms have more freedom to roam about.

 

I told you I thought there would be no change in velocity. In other words no change in the temperature of the gas.

The random thermal motion just has a larger scope.

 

However you are now asking about something different. You now want there to be a nozzle. A channel in which a pressure gradient is temporarily maintained and pressure converted into directed velocity.

 

I'm not sure how this is supposed to relate to galaxies. Maybe you should refine the image and try to make it relate to the universe in some way.

 

You should probably note that relative to the background, galaxies are nearly stationary. They have random motions which, when possible to measure, turn out to be a few hundred km/second at most. Whereas light goes about 300,000 km/second. That is, galaxies move on the order of 1/1000 of the speed of light.

 

However most of the galaxies which we can see with, say, the Hubble telescope, are receding from us at more than twice the speed of light. That is, the distances from us to them are increasing at over twice 300,000 km/second.

 

Recession is not the same as ordinary motion. It does not get you closer to anywhere. It has no destination. It is not limited by the Special Relativity Speed Limit. It is just a rate of distance increase.

 

A distant galaxy may give you the impression that it is moving and going somewhere. But it is not getting closer to anything. There is nothing ahead of it that it is getting closer to. It has no direction of motion. It is getting farther away from everything. It has no momentum associated with this change in geometric circumstance. Distances from it, as from us, can change at rates exceeding c. Because that change is not ordinary motion.

 

So somehow you want to relate this to gas in a box? It sounds like an analogy with very limited applicability. Useful as a visualization but not something that would make for a reasonable numerical comparison.

 

BTW Happy New Year! I hope we all learn some new things in 2010 and that the experience is on the whole pleasant.

 

Martin, this post of yours is wonderful. Your effort of explaining so many concepts in so few words is higlhy appreciable. It makes clear to anyone (I hope) how difficult are those concepts to explain, and to grasp. Talking about distances, for example, IMO there are 2 concepts-in-one. The first is distance in space, as we learn at school. Increasing distance is called motion, and increase of motion is called acceleration. O.K.

The second concept is "distance-out-of-space", a concept nobody learn at school. When geometry of space change, distance (the second concept) increases (or decreases) without motion. You must know that no layman can understand a thing of it. Please, use another word for the second concept, and maybe someone may grasp something of it. I have the very strong feeling that even very renowned scientists use the one concept for the other without taking any attention of it.

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qft :)

 

hi Michel and iNow,

thanks for the favorable comment, it's encouraging.

 

iNow, as I recall from your past comments we have a fairly similar perspective on cosmology and you have some hands-on experience with the mainstream model embodied in Wright's and Morgan's cosmology calculators.

 

Michel, my impression is you have mental energy that you put into assimilating and questioning new ideas. I have no idea of your actual age. The avatar is of a young person but you don't seem that. You don't have fixed set ideas AFAICS.

 

It's risky getting into these borderline philosophical areas like what is distance what is time what is motion. How do we do geometry if we don't do it the way it is taught to adolescents in Middle School? What causes Euclidean geometry to work---why is it such a good fit to reality in ordinary circumstances? Part of the risk is that I will say something wrong and have to take it back or try to put it another way. Part of the risk is that by engaging these questions prematurely Michel just gets confused.

 

Like rock climbers, be sure you have a safety rope. Be sure you can go back to your earlier world view, your previous practical understanding of time distance motion. In case of a wrong move, or somebody's foot slips.

 

Michel, I haven't read every recent post on the SFN forums. I know only a small part of what you have written.

 

So please fill me in. Are you familiar with those red and blue blotchy oval sky maps of the microwave background?

Produced using data from various spacecraft missions: COBE in the 1990s, WMAP in the 2000s. And now Planck for the next couple of years. Until its liquid helium runs out.

 

Do you have a mental picture of the black body thermal radiation curve? Not exact I mean, just a rough picture. The kind of lop-sided bell curve?

It's a fairly deep feature of nature. Max Planck got the concept of it in 1900 and it triggered quantum mechanics. There is a different curve for each temperature. They all look the same, just morphed right or left to favor higher or lower wavelengths. Same lopsided bellcurve shape but the peak is at a different place. The curves plot radiation intensity versus wavelength, or alternatively they plot intensity versus frequency.

 

I have some things I want to say about time distance and motion. But first I want to make sure those oval maps of the CMB sky temperature are familiar. And also to mention that the way radiation sky temperature is measured is to gauge the intensity in each small wavelength bracket and plot a curve---and compare that observed curve with the theoretical one that Max Planck discovered. Adjusting the temperature parameter in the theoretical curve, so you get the snuggest fit to the data, ultimately tells you the temperature of the observed radiation.

 

I'm no great expert on the CMB, just have a common-sense understanding of it as an interested bystander. I want to check to make sure that we are on common ground here. That you have some comparable familiarity. Both on the same page. I'll explain why later.

===============================

 

Well, I guess I'll go ahead and say a bit without waiting for response to the above.

 

In mainstream cosmo it is generally assumed the oval CMB temperature sky map is a photograph of the ancient universe (AU). Absolute motion relative to the AU is clearly revealed by a doppler dipole. In preparing the map, our own motion is already deducted. The solar system is moving about 370 km/s in the direction of the Leo stars and that causes a hotspot in the initial map of observations. And that hotspot is taken out already when you see the map.

 

So we have a universal idea of a stationary observer (not moving with respect to AU) and we map the sky from the ideal standpoint of a stationary observer who dropped out of the solar system and of our galaxy at a certain moment. It doesn't make a lot of difference because 370 km/s is so slow. It's all approximate anyway. But that's the ideal.

=================================

 

On the topic of motion in general. In order to define and talk about motion you seem to need a specified observer. At least a definitely specified imaginary observer.

The ideas of time and distance depend on the observer. Also the choice of which events are simultaneous. It seems to me that for spatial distance to have a meaning, it has to be between simultaneous events. Otherwise the separation is a mix of temporal and spatial separation. It seems you can get different answers for distance depending on how you measure.

It is often said that in cosmo there is no one obvious most natural definition of distance. There are several distances---Wright's calculator gives several and there are others.

 

=================================

 

On the other hand in practice the situation is not as vague as that suggests because a lot of the actual work is done using an unambiguous idea of distance based on observers stationary with respect to the ancient universe. Not moving with respect to CMB. It is one of the easiest things to refer to, a kind of obvious landmark.

 

Before the CMB was observed, they already had the same idea of stationary, they just called it "comoving with the Hubble flow". That means stationary with respect to the expansion process as a whole. There are other ways of telling that we are moving 370 km/s in the direction of the Leo stars. One doesnt need the CMB, but that is the modern accurate way.

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Sidebar ... Michel, my apology for getting your name wrong. My brother's name is Michael, and my trifocals warp images a little. I just didn't look carefully enough. A common failing on my part. Like your pencil analogy, too. Your idea is expressed in a way that even a layman ( like me ) can visualize. Further sidebar. My neighbors on the island I mentioned were named Karragorges. Shortened to Karras. Good greek family. And great neighbors.

 

Martin, thank you for that explanation. I changed from your box to the 100^3 ft vacuum chamber in an attempt to provide a 'better' picture of the properties/forces involved. I think all the forces from sub-planck to the galactic and beyond are interelated.

 

Certainly, I may be seeing non-existent relationships here, but I need to fully dis-prove them before I can move forward.

 

Ok. That said ... My 'hypothetical' relationship between the dispersion of gasses and the galaxies motion relative to us, and the backround does not appear IMO contradictory.

 

I do have a good grasp, I think , of the difference between recession and 'ordinary' motion.

 

Space 'smoothing' out the bumps would have only ( essentially ) gravity, and EM working against it. That 'endless battle' you mentioned.

 

It is my thinking that the energy stored within the 'fabric' of space is universal and generally isotropic. It would apply across the board. Shoving/pulling atoms/molecules would require much less 'force' than shoving a galaxy. But if the force is constant, the acceleration ( increase in velocity ), whether to an obsever in motion ... us ... or to a 'fixed' point observer could appear as the galaxies appear now.

 

I have not suggested that galaxies are getting closer to anything, nor that galaxies have exceeded C relative to CMBR. Or for that matter, have anything other than velocities consistent with angular momentum relative to a fixed point. In my view, everything ( matter ) will move farther apart relative to each other. Space being what it is, it will treat everything equally, subject only to and restricted by laws of inertia, angular momentum, EM, and gravity.

 

I am sorry I was less than clear in my changing of the experiment. I never meant for you to visualize the 'box' inside the vacuum chamber. I was more concerned ( as I mentioned before ) about the RATE of acceleration of the atoms/molecules as they attempt to reach equidistance when released from one end of the vacuum chamber. I understand ( somewhat ... lol ) the effect temperature has on the relative motions of atoms. Temperature is just another phenomena associated with matter/energy, and of course that is another dynamic that needs to be factored in.

 

Thank you, as always for allowing me this format to express my thoughts.

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Martin, my photo has been taken today with a VLT focusing on a point 41 LY from us. No kidding, on the picture I am about 8 years old. Today I am 49. I am architect, no physicist, quite far from my standard occupation. I won't tell you the story of my life. Some other time maybe. I like your posts because they are quite (not nervous), coherent and full of content.

 

Back to the point. I didn't expect anything of what you said. I was waiting for something like the Scale Factor. Correct me, but the expansion of space is often mentionned as a "scale factor", which is a very weird and difficult concept for common people. The scale factor is this instance related to "increasing-distance-due-to-the-expansion-of-space-without-motion". I have to admit I have lost exactly the point I wanted to raise. My mind goes at speed near to C and my typing like a snail. There is so much to say. I think that this search for immobility is wrong. Also I think that Newton was more relativist than Einstein, and if Isaac was still there, he would laugh at us. Also I am sure that something is wrong at the basis of our understanding of physics. Not being a physicist, I am "Out of the dance" (as we say in Greek), so I can throw ideas freely. Ridicule does not reach me.

Ah, I am Belgian french-speaking, I live & work in Greece now than 25 years. I speak & write fluent Greek language. I have 2 eyes, a mouth, etc. I like beer (belgian beer of course). Genealogically speaking, I am your cousin. And I can follow what you wrote about CMB.

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Martin, my photo has been taken today with a VLT focusing on a point 41 LY from us. No kidding, on the picture I am about 8 years old. Today I am 49. I am architect, no physicist, quite far from my standard occupation. I won't tell you the story of my life. Some other time maybe. I like your posts because they are quite (not nervous), coherent and full of content.

 

Back to the point. I didn't expect anything of what you said. I was waiting for something like the Scale Factor. Correct me, but the expansion of space is often mentionned as a "scale factor", which is a very weird and difficult concept for common people. The scale factor is this instance related to "increasing-distance-due-to-the-expansion-of-space-without-motion". I have to admit I have lost exactly the point I wanted to raise. My mind goes at speed near to C and my typing like a snail. There is so much to say. I think that this search for immobility is wrong. Also I think that Newton was more relativist than Einstein, and if Isaac was still there, he would laugh at us. Also I am sure that something is wrong at the basis of our understanding of physics. Not being a physicist, I am "Out of the dance" (as we say in Greek), so I can throw ideas freely. Ridicule does not reach me.

Ah, I am Belgian french-speaking, I live & work in Greece now than 25 years. I speak & write fluent Greek language. I have 2 eyes, a mouth, etc. I like beer (belgian beer of course). Genealogically speaking, I am your cousin. And I can follow what you wrote about CMB.

 

And my further apologies for assuming you are greek! Lol. ( and for any lack of coherency!! )


Merged post follows:

Consecutive posts merged
Michel wrote:

 

" ... taken today with a VLT focusing on a point 41 LY from us."

 

Never want to correct you, as you have been very kind, but you are incorrect on this. ( I think ) True, the focal point is 41 years in the past, but the actual location of that point would not be 41 LY from us.

 

To calculate that point we need to figure out where you were on Earth at that moment, the correct point in orbit around the sun, the sun's position in the galactic arm, and the galaxy's position in relationship to CMBR.

 

The following is from another forum where I make an attempt to debunk Time Travel.

 

Kind of off-topic, but as long as I am waiting for further input ....

 

Time travel is impossible.

 

It is irrelevant whether or not the physics suggests it is possible.

 

Here are the most critical reasons why.

 

The sun is moving THROUGH space relative to the galactic arm at around 20 kilometers per second.

 

Our galactic spiral arm is moving THROUGH space at about 220 kilometers per second relative to the center of the galaxy.

 

Earth is moving THROUGH space relative to the sun at about 30 kilometers per second.

 

Earth is spinning at about .5 kilometer per second at the equator.

 

We do not 'take' space along with us. We move THROUGH it.

 

If you were to travel back in time just 1 second in the past, you would find yourself at a completely different location.

 

Perhaps a couple hundred kilometers underground. Or out in space.

 

10 minutes in the past puts you a hell of a long way from Earth.

 

Not only does your machine have to transport you through time, but it must move you physically to another location.

 

500 years in the past? 34,689,600,000 kilometers from your starting location.

 

Hmmmm. Wonder what the energy requirements are to move 200 pounds about 35 billion kilometers instantaneously?

 

Better make sure your airbag is functional, and buckle your seatbelt. Tight.

 

Good luck!

 

 

Darn it. I made another error. Multiply that 35 billion by 550 kps. That's the speed of the Milky Way galaxy, relative to the cosmic backround radiation.

 

Hmmm. Let's see. That would be about 19,250,000,000,000 kilometers from your original location in space on that 500 year journey into the past.

 

I'm going to say that is about 2 lightyears. Instantaneously. My math is probably not very accurate. But you get the point.

 

Interesting, isn't it that time travel is also faster-than-light travel.

 

Hope the other end of your worm hole has GPS.

 

Not looking very promising .....

 

So Michel, assuming my math isn't too granular ( lol ) That focal point is about .16 LY from our current position.

 

Of course, we can't add all these up in a linear ( straight line ) fashion, so the real distance will be considerably less .....

Edited by pywakit
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... waiting for something like the Scale Factor. Correct me, but the expansion of space is often mentionned as a "scale factor", which is a very weird and difficult concept for common people.

 

Let's humanize the scale factor. In around 1922 a wonderful young Petersburg russian named Alex Friedman came up with a formula for distance, technically a metric, that had a scale factor a(t) that could vary with time.

 

He had a ridiculously bulbous head, like a lightbulb, or a comicbook alien.

And at one time he held the world record for altitude. Ballooning.

Probably without proper oxygen equipment. Incredible nerve, an adventuresome curious guy.

 

So part of the formula had this factor a(t) multiplying it.

It was a spacetime metric. The spatial part had the scalefactor on it.

 

The amazing thing was that this metric was a solution to the 1915 equation of General Relativity. It was a solution that Einstein had not thought about and it seemed so strange to Einstein that at first he totally rejected it. But after a while he got around to agreeing and he recommended Friedman's paper for publication in the Zeitschrift für Physik.

 

In Cyrilic his name is spelled with one n, Friedman, but the German spelling is Friedmann, so in an encyclopedia you will likely see it either way.

 

Soon after publishing his papers, which provided the model still used by all cosmologists, the young Friedman died of typhoid fever. That was 1925 as I recall.

 

Look him up, he gave us the scale factor and the Friedman model. A Belgian named Lemaître later came up with something similar---so some people call it "Friedmann-Lemaître". Call it whatever, it's the math model of the universe that gives a meaning to the scale factor, an increasing function of time a(t) that describes the expansion-history of space.

 

The 1915 Einstein equation governs metrics. Metrics specify a geometry of the universe. That's what it's about. To be interesting, a metric has to be a solution of the Einstein (Gen Rel) equation.

 

http://www-history.mcs.st-and.ac.uk/Biographies/Friedmann.html

 

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

Edited by Martin
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Martin, I very much appreciate the reminder that science has a human face. Fascinating thumbnail on Friedmann. Such a pity he died so young. Again, I feel quite inadequate in the presence of minds like Friedmann's, Einstein's ... and yours. I'm grateful to have any skills at all ....

 

Although it is highly unlikely ( impossible? ) I will ever achieve anything comparable to the great minds of the past ... or present ... I found this summation comforting.

 

... Friedmann is seen as a profound, independent-minded, and daring thinker who destroys scientific prejudices, myths and dogmas; his intellect sees what others do not see, and will not see what others believe to be obvious but for which there are no grounds in reality. He rejects the centuries-old tradition which chose, prior to any experience, to consider the Universe eternal and eternally immutable. He accomplishes a genuine revolution in science. As Copernicus made the Earth go round the Sun, so Friedmann made the Universe expand.

 

I would consider it the greatest honor to be able to contribute to humanity's understanding of the universe. Clearly not an easy task, and perhaps I simply lack the capacity. Challenging conventional wisdom ( whether religious, political, or scientific ) is without a doubt a masochistic endeavor. But there has never been another option open to me ... you are what you are.

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The 1915 Einstein equation governs metrics. Metrics specify a geometry of the universe. That's what it's about. To be interesting, a metric has to be a solution of the Einstein (Gen Rel) equation.

 

Any metric can be a solution to the field equations if we allow it to define the matter content.

 

You have to decide if a metric is "physical" by considering if the matter content is reasonable (via energy conditions say) and/or the geometry is not pathological say no CTC's or be globally hyperbolic (causally well behaved).

 

It is not really so amazing that the FRW metric satisfies the field equations, the interesting things is that is describes a homogeneous and isotropic space-time. This is independent of the field equations and thus any metric theory of cosmology that requires a homogeneous and isotopic universe will have the FRW metric as a solution.

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