A Question from a Non Scientist

[Daphne Bagshawe]

Would one of the scientists here answer a question for me. If the Branes theory of many universes copes with the technical problems of the singularity via collisions, how does this do anything except transfer the philosophical problems from the singularity to the Branes? I am still asking what preceded the Branes and where did they come from.Can there be a dimension with nothing in it or with no properties. If not how did these characteristics arise? If time is a function of matter is it correct to say that there was nothing before the first existing property? If this is so then are all universes in fact eternal because all time is within them. I hope all you physicists will not mind being joined by a rather lowly philosopher.

 

[selfAdjoint]

Welcome to PF Daphne!

Physiscists don't explicitly concern themselves with the philosophical consequences of their theories, although one might say they keep an eye cocked for them, and will expound them when coming to write popularizations.

The tacit assumption of the colliding branes scenario is that the branes have "always" existed, and the collision is just one of an ongoing sequence of such events that has no beginning or end. Thus from a philosophical angle colliding branes gets us away from the "hard beginning" implicit in the big bang and back to a new form of the steady state cosmology.

 

[marcus]

Would one of the scientists here answer a question for me. If the Branes theory of many universes copes with the technical problems of the singularity via collisions, how does this do anything except transfer the philosophical problems from the singularity to the Branes? I am still asking what preceded the Branes and where did they come from.Can there be a dimension with nothing in it or with no properties. If not how did these characteristics arise? If time is a function of matter is it correct to say that there was nothing before the first existing property? If this is so then are all universes in fact eternal because all time is within them. I hope all you physicists will not mind being joined by a rather lowly philosopher.

[EDIT: I see after posting that selfAdjoint has already responded in nice concise form. but I will leave this up anyway in case it sheds additional light]

Daphne I think this thread would do better in philosophy forum and I hope it is moved there, because I think you are raising the question

Where did it all come from?

this is not a physics question, or strictly speaking even a scientific question

In science the aim is to MODEL WHATEVER CAN BE OBSERVED in a way that assumes as little as possible and PREDICTS as much as possible, so that the model can be TESTED.

A singularity just means a point or region where the model fails----where it starts to produce meaningless numbers or infinities. The vintage 1915 model spacetime fit the observations very nicely back to a moment where it failed and produced infinities. this was recognized as a sign something was wrong and it has been improved now so that it doesn't do that.

Here is an sample from a modern theory (LQC) that removes the singularity:
http://arxiv.org/abs/gr-qc/0509075
Using the LQC model one can continue extrapolating time back PAST the place where the 1915 theory had a "big bang" singularity and into a prior contraction stage. The new model will have slightly different predictions about the microwave background, which are being worked out. This will allow it to be TESTED by looking for a kind signature or trace left over in the microwave background of expanded primordial light. Then if the LQC model does not check out it can be discarded and replaced with something better.

BUT NO MATTER HOW GOOD THE MODEL GETS YOU CAN ALWAYS ASK WHERE DID IT ALL COME FROM because that is a philosophical or religious or literary or mythological question. The model is not supposed to give an answer to "where did it all come from" which is not a scientific question.

What I am telling you is something out of philosophy of science. A cosmology model can be thought of as a machine which is consistent with past observations and predicts future observations (so that a wrong outcome can refute it) and the machine is not supposed to break down at some moment in the past, because that would be a glitch where it fails to apply, a limit on its applicability, a singularity. A breakdown at some past instant leaves a huge inelegant trash heap of explaining to do, like how did all these initial conditions get determined!

Remember the game is to use the simplest assumptions and derive the most detailed and precise observations from them. To PREDICT THE MOST FROM THE LEAST.

but even though you arrive at what is currently the simplest available most perfectly predictive model---- no matter how simple and elegant it is someone can still come along and ask "Where did it all come from?"-----and that simply moves the discussion out of the science department and into the realm of philosophy.

 

[marcus]

WOW, great Jehosephat etc.
it is highly providential that Daphne dropped in here because she could have been thinking that the cousins could use some of her experience with coping with religious issues in education in a civilized multifaith committee manner at the UK county level.

As it happens we in USA are having a very unfortunate time of it just now because we have handled the business of the division of Church and State very poorly and alienated and radicalized a large segment of the cultural and religious Stay-puts who are now blockvoting against their own rational and economic selfinterest and supporting a cruel and stupid foreign adventure and it is simply destroying the USA and even somewhat the prior-established global system.

This is tragic and it stems from issues connected to religious custom and doctrine. But look at THIS

http://eastsussex.gov.uk/yourcouncil/about/committees/meetings/sacre.htm

this is something which the UK people invented. If Daphne Bagshawe lives in UK then she probably can tell us about this. In particular if she lives in East Sussex. It is a COMMITTEE where you get all sorts of religious leaders (islam, baptist, quaker, buddhist, jewish, RC, Church of England, Russian orthodox you name it!) and get them together with COUNTY COUNCILMEMBERS and have a civilized conversation about how can we accommodate each other.

Forget about the big bang, people! we are in an emergency where the religious right is destroying the country and we made a mistake somewhere along the way and brought this on. This is what the British are for they have ideas of how to deal with problems that we didnt think of and we should learn from them when we have difficulties.

So please find the proper forum for Daphne (if she is knowledgeable about UK church/state institutions like this SACRE committee) and let us ask her questions!

SACRE means "standing advisory council on religious education"

sorry if this is just a "wild surmise" (a wild guess that D.B. is an east sussex yookay person) as in

or like stout cortez when with eagle eyes
he stared at the pacific, and all his men
looked at each other with a *wild surmise*
silent upon a peak in darien

that kind of wild surmise (that DB was chairman of that committee until she stepped down, the minutes show, on 14 June 2004, heh heh must have left her with a lot of philosophico-scientific questions on her mind, if it is that DB)

hello daphne, do you have any ideas?

 

[Daphne Bagshawe]

Hi Marcus Yes I was Chairman of our SACRE here in East Sussex where I was also Chairman of the whole Council but my question is not in my mind at any rate connected with that. I am very interested in modern Physics though I have no training in it. I try to understand what it is telling me about the nature of matter and time and I wondered how the new Branes analysis shed light on the start of our own Universe and then of course the start of everything else. I am grateful for the replies and am mulling them over. Thanks for replying. I do not assume that our experience in the UK would be useful in the US but of course I would be very happy to explain how our SACRES work and what they achieve over here

 

[marcus]

Hi Marcus Yes I was Chairman of our SACRE here in East Sussex where I was also Chairman of the whole Council but my question is not in my mind at any rate connected with that. I am very interested in modern Physics though I have no training in it. I try to understand what it is telling me about the nature of matter and time and I wondered how the new Branes analysis shed light on the start of our own Universe and then of course the start of everything else. I am grateful for the replies and am mulling them over. Thanks for replying. I do not assume that our experience in the UK would be useful in the US but of course I would be very happy to explain how our SACRES work and what they achieve over here

thanks for replying to my somewhat disorderly and clamorous post, Daphne. I was uncontrollably excited at the moment, when it occurred to me that UK might have invented an institution to help diverse religious groups be comfortable with science education. a sore point. almost a kind of vendetta against darwin going on.

However given that your expressed concern is with physics, and cosmology in particular, we should put the SACRE discussion on hold and address your questions.

I will try to help. selfAdjoint, who is knowledgeable and courteous, will certainly be back. we may get help from quite a few other people---I hope to your eventual satisfaction

 

[marcus]

In the meantime, until selfAdjoint gets back and can describe the brane scenarios, won't you have a look at these two papers

http://arxiv.org/hep-th/0505154
Reconstructing the Universe

http://arxiv.org/hep-th/0509010
The Universe from Scratch

just click on "PDF" to get a download of the whole paper, and flip through to see if there are any pictures. just read the first paragraph of the introduction and glance at the conclusions. to get an idea

this is the socalled CDT model. a rival to branes, and to LQC
you should get to know all three, not just branes
people are getting good at modeling the emergence of spacetime
it is actually exciting, there are new ideas taking shape

 

[selfAdjoint]

Here is a pretty good resource on one of the colliding brane models (there are several). It's from a talk given last year, so it's fairly up-to-date: http://www.arxiv.org/abs/astro-ph/0401579 The way to see the full text is just the same as for Marcus' CDT citations, the link takes you to the abstract and you click on PDF (assuming you have a reader for that).

Here are a couple of quotations from the paper to give the flavor. The word alternate in the first one refers to big bang/inflation cosmology. The singularity referred to in the second quotation is not the big bang, but rather the singular physics where/when the branes collide. The various references in brackets are available from the full text; many of them are links if you want to follow up.

The most serious candidate for a viable alternative account of cosmic his-
tory is the cyclic model of the universe [2, 3, 4, 5]. It proposes that time did not
begin at the big bang; rather, our current period of expansion is one out of an
infinite number of cycles. Each cycle consists of: (i) a hot big bang phase dur-
ing which large-scale structure forms, (ii) a phase of slow, accelerated expansion
which dilutes the universe, (iii) a phase of slow contraction during which nearly
scale invariant density perturbations are generated, and (iv) a big crunch/bang
transition at which matter and radiation are created and the next cycle is trig-
gered.

and

Our analysis relies on the assumption of a successful transition across the
singularity, as proposed in [3]. While there has been ample literature on the
subject recently [12], a formal proof within string theory is still lacking. It is
worth emphasizing, however, that the singularity featured in cyclic models is one
of the mildest imaginable. As such it constitutes our most hopeful candidate of
a singularity that could be resolved in string theory. For our purposes, we shall
assume the proposal of [3] for going through the bounce as well as that of Tolley
et al. [4] for the passage of density perturbations.

So you see they assume recurring collision events within a continuous time frame.

 

[marcus]

...
Here are a couple of quotations from the paper to give the flavor...

Daphne, people here, myself included, can also provide simplified paraphrase. We just have to understand what level works for you, which can take some trial and error.

Ask repeatedly to have stuff explained, as required.

To reinforce what sA just said, it is also good to have at least some minimal exposure to original sources----journal articles. If you can scan them to find comprehensible passages, and avoid getting bogged down, you will get some firsthand impressions and that way not be wholly dependent on popularized accounts.

 

[CJames]

Here is a pretty good resource on one of the colliding brane models (there are several). It's from a talk given last year, so it's fairly up-to-date: http://www.arxiv.org/abs/astro-ph/0401579 The way to see the full text is just the same as for Marcus' CDT citations, the link takes you to the abstract and you click on PDF (assuming you have a reader for that).

Here are a couple of quotations from the paper to give the flavor. The word alternate in the first one refers to big bang/inflation cosmology. The singularity referred to in the second quotation is not the big bang, but rather the singular physics where/when the branes collide. The various references in brackets are available from the full text; many of them are links if you want to follow up.




and



So you see they assume recurring collision events within a continuous time frame.

I thought that observations of background radiation showed the universe was probably flat and open, no big crunch. Was that an overstated conclusion that has since been refuted?

 

[mccrone]

Hi Daphne

A cynical point about clashing branes scenarios - string theorists are desparate for testable theories at the moment and so unlikely stories get promoted on the grounds that they are at least testable. It is a way of keeping funding rolling.

On your more general point, you will find that physicists are indeed fairly myopic about the metaphysics of what they are doing. Marcus expresses the epistemological orthodoxy.

If you study epistemology, you will recognise a reasonably clear division between science as philosophy (truth models) vs science as technology (control models). Most scientists are a little confused as to which they are doing, and some even think the two styles of modelling are the same!

If you are seeking a different metaphysical slant to the conventional reductionist/atomist equation of getting something from nothing, you can consider the alternative based on the notion of ontic vagueness - getting crisper somethings as a development or phase transition from vaguer states of potential. A potential is a realm where everything is possible, even if nothing has actually happened. In physical terms, you might be talking about spacetime fluctuations over every scale - a chaos of dimensionality. Then via a phase transition or symmetry breaking you would have this disoriented realm line up to make a smoothly coherent system. You would get a crisper something from a vaguer everything.

Time would be also vaguer in the "prior" vagueness. So there would be "time", but not as we know it Jim - a smooth progressive flow.

To make sense of this approach, you have to have some model for how a system can self-organise out of a vague chaos. Here you can tap into dissipative structure theory, or pan-semiotics, or scalar hierarchy theory, or some of the other interesting approaches available in complexity science.

 

[marcus]

Would one of the scientists here answer a question for me. If the Branes theory of many universes copes with the technical problems of the singularity via collisions, how does this do anything except transfer the philosophical problems from the singularity to the Branes?

Dear Daphne, as distinguished visitor you honor us by your question. Please do not be dismayed if you hear shouting.

BTW I was trained as mathematician, not physicist, so cannot call myself a scientist but nevertheless beg your indulgence to reply to the question, as one who, in his retirement, took up with the quantum physics of spacetime ("quantum gravity" for short since gravity is the geometry of spacetime).

If the Branes theory of many universes copes with the technical problems of the singularity via collisions, how does this do anything except transfer the philosophical problems from the singularity to the Branes?

I do not think brane-cosmology copes especially well with the singularities of the classical theory, or with anything else----am inclined rather to view it as a passing fashion. But IF IT DID cope in a creditable way then indeed IT WOULD "transfer the philosophical problems from the singularity to the Branes."

One does not need such an elaborate set-up as extra dimensions with loose branes bumping----if one wants to cure the classical singularities by quantizing the classical (1915) theory.

This is one of the main points being made at next month's Loops 05 conference at Potsdam outside Berlin----October 10-14.
http://loops05.aei.mpg.de/
Pretty much the whole of Friday is devoted to talks about LQC removing the singularities of classical cosmology. It does so without having to assume any extra dimensions

Occam's razor. (Dimensions, and other) entities are not to be multiplied unless necessary.

My guess is that brane-cosmology will dissipate with time. Actual working cosmologists, judging by the papers on file at arxiv.org, are not much interested in brane models.

If you wish, have a look at the Loops 05 conference programme
http://loops05.aei.mpg.de/index_files/Programme.html

If you look at Friday you see Roy Maartens of University of Portsmouth talks at 12:20, followed by Abhay Ashtekar of Penn State and from then on it is all cosmology, and testing loop cosmology, and removing the classical singularities etc. for the rest of the day.

Loop quantum cosmology (LQC) is undergoing rapid growth, people are entering the field and the number of papers per year is increasing.

On the other hand the number of papers mentioning "brane" in the abstract has been declining from 2001 to present. One can easily check this with the Harvard abstracts search engine. I would not venture to interpret this but the decline in the number of brane papers per year is fairly clear.

So you could modify your question and bring it more up to date by recasting it:
"If the LQC theory of copes with the former classical singularity by getting rid of it and extrapolating time back to an earlier contracting phase, how does this do anything except transfer the philosophical problems from the singularity to the LQC model itself?"

And I think that philosophically it does NOT do much else. If you were to ask that rhetorically I would have to immediately agree with you. If you said "It doesn't solve any philosophical problems at all, does it? It just gives them a different technical shape and setting." I would have to say "Right."

But IMO the model is not intended to solve philosophical problems. Rather it is supposed to be simple (which LQC is rather) and to fit the data and to make predictions about future observations so it can be tested. That it seems to do or to be in the process of doing. Roy Maartens would be one to ask about that, he devises ways of TESTING theories and he has worked both with branes and with LQC. He is not committed to one quantum cosmology or another, that is not his line, he is more the pragmatic "phenomenologist" type. Also he nags theorists to make testable predictions (nagging is also a phenomenologist's privilege and duty) and checks their sums.

In fact a way to get a good unbiased report on all this would be to telephone Prof. Maartens, since you are in UK.
An academic should listen to an East Sussex Councilor. By jove, I will get you his email too, if I can find it. Then you shall have all this from the horse's mouth. But write him before he leaves for Germany to give his talk.

this is a list of all Prof. Maarten's papers since the arxiv began
http://www.arxiv.org/find/grp_physics/1/au:+Maartens_R/0/1/0/all/0/1
there are 95 in all, on the arxiv. (before 1992 preprints were not archived electronically). You can see many many about branes. but lately quite a few about LQC.

here is his Uni Portsmouth page with photo (to recognize him on chance encounter) and email
http://www.tech.port.ac.uk/staff/index.php?id=125
http://www.tech.port.ac.uk/staffweb/maartenr/

South African, PhD 1980. here is the abstract of the invited talk he is to give at the conference Friday 14 October:

Speaker: Prof. Roy Maartens
Title: COSMOLOGY AND QUANTUM GRAVITY
Abstract: I will review the basic features of the standard, classical model of cosmology, which is based on General Relativity, and how this model accounts for observed properties of the universe. Modifications to General Relativity that are inspired by quantum gravity need to be tested against cosmological observations. This is one of the key tests for any candidate quantum gravity theory. I will discuss in general terms some of the difficulties involved in this aim, and what is needed from theorists in order to achieve this aim. In particular, I will compare some of the features of stringy cosmology and loop quantum cosmology.

 

[marcus]

Geeze, looks like Daphne lives some 50 miles from Portsmouth and she is asking about quantum cosmology models like brane (and should also be considering Loop) and the little-known world authority on comparing and testing these quantum cosmology models is living 50 miles away. Like, hey Daphne, drive over and have lunch.

But on what pretext? She doesn't know enough yet to converse with the guy. Unless he is a natural-born pedant and loves explaining.

East Sussex is where the normans landed, if I remember. unless I'm mistaking it for somewhere else, Kipling wrote a little book about the area and its history.

 

[Daphne Bagshawe]

Thanks from a non scientist

Thanks to everyone who has tried to help me understand some of these current hot topics. As I am not a scientist it will take me some time to absorb information from the various original papers recommended but I am going to have a go and when I have done so I will come back to the board. Meanwhile a couple of comments on what you have variously said so far. I do now more clearly understand the distinction between the observe and predict science and the observe and explain science .It occurs to me that predictive verification could be a chimera in that it does not of itself guarantee an explanation.The ancients who thought the Sun rolled across the sky in a chariot were correctly able to predict its return but their explanation of the phenomenon was false.I am surprised at the consensus that "where did it all come from " is not a Scientific question. If it could be shown that matter could suddenly arise in a vacuum for example , then the question would be answered by a proof that things do not have to come FROM anywhere.Although I am delighted to discover I live close to one of the leading figures in this field I do not think I understand enough about the subject yet to justify taking up his time but I'm working on it.! Finally I am aware how justifiably depressed many scientists are at what they see as the rejection of rational scientific discovery by religious people.In my view all religious people should listen and learn from scientists. You folk are describing and explaining how things ARE.How can that be anything other than beneficial ? I admire you all very much. Best wishes Daphne

 

[selfAdjoint]

Thank YOU for that most intelligent response. The problem with "why" questions is that you get into philosophical trouble. As Aristotle pointed out, either you have an infinite regress of causes or you have a first cause. And as Kant pointed out, both the statement that causes go back forever and the statement that there was an uncaused caused are incoherent - we can't handle them rationally.

 

[Chronos]

Indeed, SA has captured the whole dilemma in a nutshell. Questions like 'How did the universe originate' do not lend themselves to the scientific method. In science you must quantify your answer for it to be meaningful. How do you identify and quantify the factors necessary to predict the emergence of the universe?

 

[marcus]

Indeed, SA has captured the whole dilemma in a nutshell. Questions like 'How did the universe originate' do not lend themselves to the scientific method. In science you must quantify your answer for it to be meaningful. How do you identify and quantify the factors necessary to predict the emergence of the universe?

Daphne has just passed thru this farflung outpost and reviewed the troops, gentlemen, and we have received her commendation.

BTW has anyone read Kipling's little book about East Sussex, the area around Pevensey Bay (where norman landed). It is called Puck of Pook's Hill and nominally for children.

Now that Daphne has graciously achieved closure on her initial segment of this thread, and appears to have returned to East Sussex County Council business, and to her Life, we can all kick off our loafers and relax. Of course we all KNOW how the universe arose---it grew out of Shiva's navel---but we can't say this in front of Daphne because that wouldn't be scientific and we are supposed to talk like proper scientists.

Yes the details are that Shiva was asleep on a 7 headed cobra that was floating on the timeless infinite ocean. And as he slept a lotus grew out of his navel. And a little head poked up out of the lotus---it was Brahma! And Brahma thought it would be nice to have universe for his and Shiva's amusement, so he created the whole universe!

And Shiva and Brahma are to enjoy the universe for 50 billion years (called a kalpa or the Day of Brahma) and then it all goes back into Shiva's navel and he sleeps for another 50 billion years (called the Night of Brahma) and then it starts over.

And we aren't even in the first cycle. I forget what cycle we are in already.

 

[rtharbaugh1]

So I guess all this speculation about first principles is really no more than what I tell waitresses about why I am studying geometry...it keeps the Alzheimers (pronounced "Old Timer's) disease away. As we used to say in the Infantry, stay alert, stay alive. I don't recall anyone ever asking why about that.

In another close encounter of the restaurant kind, I once had a conversation with a passing lesbian who told me she was thinking of switching. I wasn't able to be of any assistance there. So we talked about physics, among other things. I explained my big T.O.E., and she asked me if it was any good for making weapons. I said I didn't think so. Too bad, she said. Turned out I wasn't much use to her at all, but we had a nice talk.

The Shiva story is warm and clever and makes us all feel as pleasent as eating lotus root. But it isn't really of any use to anyone, except to show the futility of thinking about it. I still prefer to delude myself into thinking we can do better than that.

So far, the only really interesting thought I have had about fractals in regard to CDT has been that we see fractals at all scales, so what is special about the appearance of fractals at very short length scales? I presume that there really is something interesting about fractal geometry at very short length scales, but I still don't know what it is. Only the general idea of receeding self-similar lotus petals at the heart of everything does seem to take some of the nerve out of the singularity question.

Maybe it will be useful sometime to have a device capable of erasing this quarter of the galaxy, I don't know. I have no need for that much power today and doubt I would be comfortable having it in the hands of our present governments...any of them. Still, when cutting firewood I do long for anti-gravity or at least a sky-hook or something to make carrying it easier. And .99c travel could be quite interesting. I should think I would like to find out if the universe is infinitely random or if it repeats itself from time to time. I wonder if it ever begins to drool and mumble as it tells the same old stories to itself, over and over.

Meanwhile I think I have found an error in Barnsley's pedagogy. It is too complicated to present here and I am full of self doubt. Maybe it just looks like an error because I still don't really know how to read his notation. In short he says that if A,B, and C are sets in a Hausdorff space, and B is a subset of C, then the distance from A to C is always less than or equal to the distance from A to B. But this does not seem to me to be true if A is a subset of B or of C. I think maybe he was neglecting that possibility.

I noticed no one mentioned black hole evaporation in response to Daphne's question about something from nothing.

Well, I have an invitation for after-dinner conversation over vats of pickled beets and canning jars, so I'll end here. It is supposed to freeze for sure tonight, and all my neighbors are working with their produce. Maybe I'll put in a garden next year.

Be well,

Richard

 

[marcus]

Maybe it just looks like an error because I still don't really know how to read his notation. In short he says that if A,B, and C are sets in a Hausdorff space, and B is a subset of C, then the distance from A to C is always less than or equal to the distance from A to B. But this does not seem to me to be true if A is a subset of B or of C. I think maybe he was neglecting that possibility.

Richard if A is a subset of C then the distance from
A to C is zero, is it not?

and zero is less than or equal to any other distance including that from A to B (which could also be zero and that wouldn't hurt)

Ah, but I see you are busy pickling beets, so i will not get your attention for a while.

so I think perhaps the author has not made a mistake after all

 

[marcus]

Richard spacetime may well be fractals all the way down, as follows


if CDT is right then the microscopic spacetime structure is tree-like, branchy
(and only to us crude macro-animals looks 4D at large scale)

But if LQG is right (also) then at very large scale OUR UNIVERSE BRANCHES and is part of a treelike structure, because every black hole connects to a new big bang and a new future, that goes "out the bottom" and so TIME FORKS in a very forky way because one tract of universe like ours can have thousands of black holes and thus thousands of forkpoints.

so OUR SPACETIME IS AT VERY LARGE SCALE A FORKY THING that could be the microscopic structure of somebody else's spacetime one level up and his would again look 4D because he is a crude creature analogous to us.

and HIS universe could be doing the same Hole-Bang connection and creating its own branchy structure which could be the microscopic basis for yet another layer

And if layers can build up, turtle upon turtle, then they be imagined descending turtle beneath turtle. and so whoever it was who said it may have been right, that it is turtles all the way (up as well as) down.

or fractals if you like

 

[Daphne Bagshawe]

From Daphne

I haven't quite gone back to Sussex duties yet as I have been seduced by this site.If B is a subset of C then the distance from A to B is surely identical to the distance from A to C. I think it could only be less if B were an intersect of A and C.I shall try to read the original papers recommended and see if my questions are made redundant by a deeper understanding. Pip Pip D

 

[rtharbaugh1]

Definitely turtles all the way down.

See if I can remember anything of yesterday's reading. In Hausdorff space, a distance is measured differently from the metric we use when in Manhattan, or in a cornfield down in Surrey. Even in close spaces, locally flat, that may be curved on a much larger scale, the metric affects the value of d, the distance. So Marcus, the metric acts locally as well as at cosmic and at microscopic scales. The metric tells you the rules for calculating the distance d, except in Hausdorff space we honor this distance exceptionally by giving it its own letter, just little old h. ( I have not yet given any consideration to the possibility that there may be some relation between Hausdorff h and Planck h, which we more often see as h-bar, just a factors difference from h. Not to get distracted.)

So in Hausdorff space, we measure things differently. The distance metric h in H space from set A to set B is found by the following: find the point in A which is most distant from any point in B, and measure straight from that point to the nearest point in B.

It works easily with circle sets like Venn diagrams, IIRC the name Venn correctly. It also works with very complicated sets like those seen in many fractal images. The interesting thing about this metric is that the distance from set A to set B is calculated differently and so may not be the same as the distance from set B to set A. That looks familiar. In formula, (AB) is not equal to (BA).

Well that is from memory and I have no doubt forgotten, distorted, baldlerized and misrepresented parts of it. I think I may have to work up to presenting diagrams and formula if we want to go further into this. Not tonight.

The pickled beets smelled wonderful, earthy and sweet. The steam in the kitchen was throaty and condensed into droplets on the sharp cold windowpanes. We talked physics and society and listened to Thelonious Monk along with John Coltrane. There were dense spirits rising up from the bags of ripening tomatoes, suprised carrots, Kale and Broccoli, peppers, onions, garlic, and spinach. We needed more counter space and talked of building a summer kitchen, a root cellar, a food storage barn for the pumpkins and squash. Maybe next year, maybe.

be well,

Richard

 

[marcus]

I haven't quite gone back to Sussex duties yet...I shall try to read the original papers recommended and see if my questions are made redundant by a deeper understanding...

Since you are still our guest, I think it would be best if we save this thread for responding to your questions.
It is easy to get hooked on message boards-----some science issues are especially seductive, such as cosmology and biology, where did it all come from (the question is always there even though one tries to repress it) how could this have happened, how could we, you, I have gotten here. and tigers.

About reading original sources (peer-review journal grade research papers) please take my suggestions with a grain of salt!
they are mainly just to SCAN lightly to get a notion of how workers in a given line of investigation talk. not to get bogged down.

you are always welcome to try to get people here to paraphrase, and try to express simply, what the essential ideas are. You are not being condemned to read technical stuff!

However if you ask people like us to explain, you will often have to ask again and again until we get the explanation right. We are often confused, or insufficiently knowledgeable, or inept in our explanations. So the questioner must be patient and even stubborn.

Also sometimes questions go for several days or a week without response just because no one feels like answering.

so it is not a bed of roses. But I still encourage and invite you to persist. I think we all like having you around.

About those technical papers. the only CDT one that MIGHT work for you is filtering out the easier parts of "The Universe from Scratch"
http://uk.arxiv.org/abs/hep-th/0509010
It was written for NONSPECIALISTS as a survey article commissioned by the UK journal "Contemporary Physics". Nonspecialists means other scientists including physicists who are not specialists in quantum gravity.
So it is not a piece of cake. It is tough. But it does not have a lot of equations and one CAN make sense of fairly large sections.

Renate Loll, the main author, was trained at London Imperial and by good fortune writes a good clear English style. (comes from Aachen I believe).
I'm a fan of hers. I collect CDT gossip in the thread called "Quantum Graffiti"

have to go, be back later.

 

[CJames]

Richard spacetime may well be fractals all the way down, as follows


if CDT is right then the microscopic spacetime structure is tree-like, branchy
(and only to us crude macro-animals looks 4D at large scale)

But if LQG is right (also) then at very large scale OUR UNIVERSE BRANCHES and is part of a treelike structure, because every black hole connects to a new big bang and a new future, that goes "out the bottom" and so TIME FORKS in a very forky way because one tract of universe like ours can have thousands of black holes and thus thousands of forkpoints.

so OUR SPACETIME IS AT VERY LARGE SCALE A FORKY THING that could be the microscopic structure of somebody else's spacetime one level up and his would again look 4D because he is a crude creature analogous to us.

and HIS universe could be doing the same Hole-Bang connection and creating its own branchy structure which could be the microscopic basis for yet another layer

And if layers can build up, turtle upon turtle, then they be imagined descending turtle beneath turtle. and so whoever it was who said it may have been right, that it is turtles all the way (up as well as) down.

or fractals if you like

Wait, so only LQG predicts that black holes lead to other universes. I thought that was a prediction of general relativity? Also isn't their some theory that each of these universes has a different physics, as in each one is basically an evolution of the last one? Is that a theory or a hypothesis, and by what mechanism does that take place? It sure would be nice if that were the case, because it would provides an origin of some kind for the physics that exist in our universe (though not an ultimate origin, since in this case their would be infinite universes). Also, could somebody answer my previous question about the size and shape of the universe? I thought our universe had basically been demonstrated as flat and infinite and that it wouldn't collapse based on data from the cosmological background radiation. Sorry for all the questions. I'm still sitting through boring Newton physics in school. I want to get to the good stuff!

 

[marcus]

... I'm still sitting through boring Newton physics in school. I want to get to the good stuff!

please learn the stuff that works and has been tested as well as you can, CJ. the people on the edge are many of them chasing the conjectured goose.

no one guarantees that anyone approach will eventually develop into a complete theory and be empirically confirmed

 

[CJames]

Yeah but general relativity and QM have been tested but they are actually interesting...ahem...I mean...uh, no I don't care if it's interesting, just if it works...

Yes, I admit it, I am guilty of searching for knowledge only because it is so bizarre and weird. If the world were Newtonian I would not be interested in physics at all. Anyway, could you at least point me in the direction of where I could find answers to some of the questions I just asked?

 

[marcus]

Wait, so only LQG predicts that black holes lead to other universes. I thought that was a prediction of general relativity? Also isn't their some theory that each of these universes has a different physics, as in each one is basically an evolution of the last one? Is that a theory or a hypothesis, and by what mechanism does that take place?...!

Gen Rel does not predict that holes lead to bangs, it just breaks down and gives meaningless answers and will not let you go past.
that is what a singularity is.
you go back far enough in time and Gen Rel blows up and you can't go back any further

but almost since the word go (1925, Heisenberg) people have expected that quantizing Gen Rel would get rid of the singularities. the Heisenberg uncertainty principle already suggests that you cannot get matter concentrated with infinite density (as happens at classical GR singularities) because the uncertainty principle suggests that you cannot pin things down within very narrow confines

I am not giving you a rigorous argument, just saying that quantum "fuzziness" has always seemed incompatible with these ideal points with their infinite curvature and density. So it was always suspected that if we could only make a quantum theory (with uncertainty) of the geometry of spacetime then it would NOT break down and give meaningless infinities and the SINGULARITIES WOULD GO AWAY.

but for many decades people tried without success to quantize Gen Rel and make this happen. the first success was by Martin Bojowald in 2001
"absence of singularity in Loop Quantum Cosmology"
I'll get the link in case you want to look at it. historic landmark in a sense
http://www.arxiv.org/abs/gr-qc/0102069
Absence of Singularity in Loop Quantum Cosmology
Martin Bojowald
4 pages, 1 figure
Journal-ref: Phys.Rev.Lett. 86 (2001) 5227-5230
"It is shown that the cosmological singularity in isotropic minisuperspaces is naturally removed by quantum geometry..."

only this year (or maybe last year) that the hole singularity was found not to be there (in the LQG treatment). that is what everyone always suspected, but it had to be derived step by step as a consequence of the model.

SO AS OF NOW we can say that yes it is possible for hole to connect to bang (in the context of a still unconfirmed model) which it was not in standard Gen Rel with a standard black hole. In the classical framework, when a star collapsed to hole, you didnt automatically get a new universe.
But it looks like you might in LQG (that is what the new paper by Ashtekar and Bojowald is about)
======================

Now the more interesting part of your post is where you appear to be referring to the Lee Smolin idea of CNS (COSMOLOGICAL NATURAL SELECTION) which is an evolution idea based on the assumption that hole continues to bang. Smolin published a book around 1997 called THE LIFE OF THE COSMOS where he talks about this. And I think he discusses it in his popular book called THREE ROADS TO QUANTUM GRAVITY, which I have not read.

If you want to read about it in a free download there are several things online, I can get the links.

The idea is that everytime there is a collapse to hole physics gets altered just slightly so the constants in the next universe are a bit different, slightly different ratios of particle masses, slightly different ratios of forces, slightly different periodic table of the elements. nearly the same but not exactly.

so having black holes is like having offspring, and the daughters are slightly different from the mother, and so there can be a kind of evolution (with selection favoring universes that condense a lot of stars that are massive enough to collapse to holes instead of just to slowly cooling white dwarf or neutron star cinders---the eventual fate of less massive stars)

If you don't want to buy or borrow Smolin books, here are some things about this on arxiv
http://www.arxiv.org/abs/hep-th/0407213
Scientific alternatives to the anthropic principle
Lee Smolin
this is not written for general audience, it was written to be a chapter in a book to be published by Cambridge University Press that is in the "philosophy of science" department. it may not be perfect, but it has comprehensible parts about the CNS idea, if you can find them

a critical discussion of the CNS idea is in
http://www.arxiv.org/abs/gr-qc/0205119
Is there a Darwinian Evolution of the Cosmos? - Some Comments on Lee Smolin's Theory of the Origin of Universes by Means of Natural Selection
Ruediger Vaas

Rudy Vaas is a good writer, or he can be a good writer sometimes. So it can be almost as quick to learn about CNS from Vaas as from Smolin. He also does not use equations and formulas because he is more of a "philosophy of science" person than a physicist. But again this is not written for popular media.

the thing is, these sources are free for download. so if you find that you can use them and they suit your purpose then it saves time and/or money

 

[marcus]

Yeah but general relativity and QM have been tested but they are actually interesting...ahem...I mean...uh, no I don't care if it's interesting, just if it works...

Yes, I admit it, I am guilty of searching for knowledge only because it is so bizarre and weird. If the world were Newtonian I would not be interested in physics at all. Anyway, could you at least point me in the direction of where I could find answers to some of the questions I just asked?

:rofl: :rofl: :rofl:

nice friendly use of irony. I think I know what you mean.
share your fascination with theories that are interesting
(although the rulebook of the scientific method does not talk about that)

keep reminding me and the rest to point in the direction as best we can of what you want, otherwise we forget, as at a noisy party, what it was you were looking for

 

[Garth]

I haven't quite gone back to Sussex duties yet as I have been seduced by this site.If B is a subset of C then the distance from A to B is surely identical to the distance from A to C. I think it could only be less if B were an intersect of A and C.I shall try to read the original papers recommended and see if my questions are made redundant by a deeper understanding. Pip Pip D

Hi Daphne!
I'm in Surrey, not too far from you, as an Anglican priest and a member of this crazy gang I'm also interested in the questions you have been asking.

And Shiva and Brahma are to enjoy the universe for 50 billion years (called a kalpa or the Day of Brahma) and then it all goes back into Shiva's navel and he sleeps for another 50 billion years (called the Night of Brahma) and then it starts over.

Actually Day of Brahma= 8.62 Gyr.
Now if H = 71 km/sec/Mpc then Hubble Time = 13.8 Gyr and the universe's age in the Einstein-de Sitter model is 9.2 Gyr!
Pretty good of those ancient Hindus to get E-d S to within 6% error!

Garth

 

[marcus]

Hi Daphne!
Actually Day of Brahma= 8.62 Gyr.

there is evidently some difference among sources, my parents' edition of the britannica, in the Indian Religion article, said the Day of Brahma is
50 billion years.

but since reading that I have come across several different estimates, i forget what but your figure of 8.62 billion years is right in there.

as the britannica and I use the word, "billion" is 10⁹ is the same as "G" for "giga"

 

[dubmugga]

...because every black hole connects to a new big bang and a new future, that goes "out the bottom" and so TIME FORKS in a very forky way because one tract of universe like ours can have thousands of black holes and thus thousands of forkpoints.

sounds like the landscape problem of many worlds with the potential for infinite vacua arising from channelling energy to different universes via black holes/white holes and inflation taking over from there...

...in which case i still prefer to think of foamy bubbles in a bath all connected instead of trees forking like wise at the quantum level

...so what makes our universe so special ?

apart from the fact that I'm in it !

 

[Garth]

"Many worlds", "multiverses", "Black holes giving birth to new universes", "Exotic non-baryonic Dark Matter", "Dark Energy", can anybody show me one of these? (Apart from our own universe that is).

Perhaps we ought to be discussing how many of these hypothetical entities can dance on the head of a pin.

Just a thought.

Garth

 

[Daphne Bagshawe]

Hello everyone. In pursuing my own self education I am still thinking about time and matter.It would seem that one cannot have time without matter but of course since matter does exist and time also ,we must be able to think back to the dawn of matter and the start of time. Then I thought how interesting it is that the one section of time we can NEVER know is the present. All sense perceptions take time to be processed by the brain. Therefore whatever we see or study is always a looking back at what it was when we first received the sense impression and that was always at a time in the past. All we can ever know is the past . Is this true?

 

[marcus]

Hello everyone. In pursuing my own self education I am still thinking about time and matter.It would seem that one cannot have time without matter but of course since matter does exist and time also ,we must be able to think back to the dawn of matter and the start of time. Then I thought how interesting it is that the one section of time we can NEVER know is the present. All sense perceptions take time to be processed by the brain. Therefore whatever we see or study is always a looking back at what it was when we first received the sense impression and that was always at a time in the past. All we can ever know is the past . Is this true?

Hi Daphne, so nice to hear from you.

Your conversations here are one of my nicest memories of some2 or 3 years back.
Sadly a gentle and deeply educated person who was here, selfAdjoint, is no more. he was one who had the most to say to you in earlier days.

Before I try to reply to your post I want to say that you taught me something about how society can accommodate people's religious habits and impulses namely by having a COUNTY COMMISSION to which all the certified priests rabis pastors ministers are invited, as long as they behave civil fashion to each other and they can talk about what should be said in school about religion. That seems extremely reasonable to me and would have saved society in this country much sorrow. Because it kind of TAMES the religious leaders and domesticates them in a certain way. They have to be willing to talk reasonably to each other (which ours cannot always do) or else they don't get to belong to the club.

I forget what your county commission is called. Maybe you would refresh my memory. And it seemed to me you had the honor of being the CHAIRperson of the commission, well that is a very useful role to play in society!

Because in the long run the harmony between science and religion----especially between cosmology and religion and biology and religion---is one of the keys to honorable human survival and ...

well I will stop and try to reply to your post.

i think we all have a stake in helping you with whatever selfeducation you want to undertake

All we can ever know is the past . Is this true?

In the sense of knowing something empirically, by the experience of our senses, we only know past events. So I would agree that what you say is true.

Let's forget about different kind(s) of knowing that might be more like knowing mathematical facts based on tautology, facts about language, definitions and their logical consequences.

 

[marcus]

Hello everyone. In pursuing my own self education I am still thinking about time and matter.It would seem that one cannot have time without matter but of course since matter does exist and time also ,we must be able to think back to the dawn of matter and the start of time...

Daphne if your position in the county government gives you access to a subscription of NATURE magazine, please do me (and some of the rest of us) the favor of going to the online subsidiary publication NATURE PHYSICS and reading the brief article by Martin Bojowald titled "What happened before the Big Bang?"

Here is the abstract summary:
http://www.nature.com/nphys/journal/vaop/ncurrent/abs/nphys654.html

I cannot read the rest of the article, because I do not have a subscription. The article will come out in hardcopy in August, and appear on the library shelves in the usual way, whereupon I shall eagerly read it. But for now I cannot.

An especially interesting thing about Bojowald's recent work is that he has discovered a kind of indeterminacy principle that VEILS the contracting phase that preceded the expanding phase which we are in. According to the model he is using, there was a bounce at very high density and temperature, when gravity becomes repellant due to a quantum correction, and contraction gave way to expansion. The matter and time we know date from then. But Bojowald recently uncovered a mathematical limitation on our knowledge of conditions in the prior contracting phase (at least within the confines of his quantum cosmology model).

Here's a Penn State University press release about Bojowald's research and this paper:
http://www.eurekalert.org/pub_releases/2007-07/ps-whb062907.php

You may recall that I suggested you give Roy Maartens a ring and have lunch or visit him at his office in Portsmouth, not far from where you live in Sussex IIRC (if I remember correctly). Good solid worldclass cosmologist, espousing no particular model---believes in testing them all.
He would be able to appreciate your situation and tell you exactly what you need to know. Including what questions haven't been answered yet.

If you are still chairperson of that county committee then Maartens has got to take an interest and be willing to spend a few minutes with you. Besides he seems like a nice young fellow who wouldn't be hard to chat with even without the official angle.

In the meantime don't let anyone persuade you that time began at some moment 14 billion years ago. there are different models---some continue back before then, and some break down at that point---so far the data does not tell us which to prefer (both kinds of model fit the observations)

Oh bother! I see that you stepped down from your SACRE position in 2004. Well, past tenure still counts. But maybe we will have to do Maartens duty as his surrogates.
===========================
UPDATE Roy Maartens is director of an institute
Institute of Cosmology & Gravitation
Mercantile House, University of Portsmouth, Portsmouth PO1 2EG, UK
Tel/fax: +44 (23) 9284 5147/ 5626

Here is his email, replace AT by symbol @
roy.maartens AT port.ac.uk

Here is a homepage sort of thing
http://userweb.port.ac.uk/~maartenr/[/URL]

Here is the Institute homepage:
[url]http://www.icg.port.ac.uk/[/url]