MikeAL

Cheers.

Thanks for clearing that up. That makes a lot of sense. One quick question though. Sure, I get the density redistribution toward the galaxy locales, and can accept the drop in average density as such a large outlier now has a dispropotionately low density, but I don't see how that would increase the volume of the universe, unless density is a constraining factor to expansion.

Hey Mordred, the sentence is a bit ambiguous for me. Are you referring to the release of energy from matter through entropy? Or are you saying that even if the universe only contained matter and no space, that the matter would expand? - I'm not sure which you want me to consider it. Right, the necklace effect, or bubble wrap appearance with matter sunk into slender corridors. I take your point on the latter definitely. The distribution has changed. Can we say that the gravitational field has weakened? - Ah, not the field no, unless weakening is a directional measure. That is what I was alluding to with a weakening field due to expansion at the beginning of the thread. So, in a way, you agree with the idea but think it was clumsily worded? Since then though, the information we've discussed seems to say that total energy does not stay constant - that the new space brings with it everything it needs, including energy, and does not acquire the properties but instead is born with them. - the permittivity doesn't change with expansion. Is this wrong? So, for example, because the gravitation feels is distorted by matter to different degrees, that implies an 'elastic' component - an energy component. For permittivity not to change wouldn't that mean that space must bring it's own energy with it rather than diluting the existing space? - thus in a sense suggesting it is prefabricated? The total energy of the photon remains the same but the distribution of that energy has... been converted to mass.... I don't know. Are you saying when it traverses a gravitational field bent by matter part of its energy is converted into mass and the loss of apparent energy as it pulls away causes it to appear redshifted? You totally got me on this one Mordred. You're going to have to explain it to me again. What is the connection? Yeah, that's fine. A little bit of philosophy helps focus the ideas. I'm just saying that imagining it this way has helped me get my head around some mind bending stuff. Probably also led me astray.

Well, I don't want to open up a theory on the matter, but I believe that the why only becomes a problem when we consider mass and energy and space as discreet entities. I kind of see it as all twisted together with one form dominant over another in different contexts. I don't think this is anyway unique thinking on my part, especially these days, but I think it is helpful. I think there are two different types of why here though. There is the why does the apple fall to the ground why, which creates the theory (which is a type of philosophy) and there is the why that is more existential and certainly philosophically based. No, I didn't say it did. His conclusion seemed incongruent with his introductory remarks however. No, I don't think it's an accounting trick. I think he is referring to the gravitational field being inverted in dark energy, such that the center of the field is a hill as opposed to the trough we find that matter creates - and thus repelling mass from it. It may have been invented to solve a few problems with GR, but I think it has moved on a bit from there. Do you disagree?

Why do you say we have no idea? Einstein gave us an explanation. Have we reached the point of abandonment of his theory in our own thinking? Einstein did prove his theory with countless experiments with time, lensing and gravitational calculations. He said gravity was a field. As scientists do we not accept this and try and work forward from there to determine the implications as they apply to other universal phenomenon- even if it leads us to a point of ultimate contradiction (thus disproving the theory)? This is an intriguing reference, Strange (http://www.preposterousuniverse.com/blog/2010/02/22/energy-is-not-conserved/). I'm going to let it sink in a bit - well actually I'm going to try and write it out here to see if I can get it right. Point 1: Because space is changing, the energy of the particle is transferred to it, thus the energy of the particle (of the photon) is not truly lost, thus there is no violation of conservation rules. Quote: ''Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is changing, the total energy of those particles is not conserved." Then it uses this example to say: Quote:"In the case of dark energy, that evolution is pretty simple: the density of vacuum energy in empty space is absolute constant, even as the volume of a region of space (comoving along with galaxies and other particles) grows as the universe expands. So the total energy, density times volume, goes up." OK, I agree and that's what this thread's been banging on about as being a bit weird... but then: Quote: "This bothers some people, but it’s nothing newfangled that has been pushed in our face by the idea of dark energy. It’s just as true for “radiation” — particles like photons that move at or near the speed of light. The thing about photons is that they redshift, losing energy as space expands. If we keep track of a certain fixed number of photons, the number stays constant while the energy per photon decreases, so the total energy decreases. A decrease in energy is just as much a “violation of energy conservation” as an increase in energy, but it doesn’t seem to bother people as much. At the end of the day it doesn’t matter how bothersome it is, of course — it’s a crystal-clear prediction of general relativity." This crescendo of the argument seems to me to fall to pieces because it seems to be saying in the first instance that there was no violation, only a reshuffling between space and particles due to the dynamic nature of both. However new space, with new energy - the increase in energy - they speak of, is not energy flowing from existing space into particles, but from new space into particles. Quote: "In particular, a lot of folks would want to say 'energy is conserved in general relativity, it’s just that you have to include the energy of the gravitational field along with the energy of matter and radiation and so on.' Which seems pretty sensible at face value." "And in my experience, saying “there’s energy in the gravitational field, but it’s negative, so it exactly cancels the energy you think is being gained in the matter fields” does not actually increase anyone’s understanding — it just quiets them down." Here it seems to be suggesting that some people believe the gravitational field energy is weakening (I assume) to compensate. - which was the thread question. Quote: "There’s nothing incorrect about that way of thinking about it; it’s a choice that one can make or not, as long as you’re clear on what your definitions are. I personally think it’s better to forget about the so-called “energy of the gravitational field” and just admit that energy is not conserved." I think this above part is the debate that we have been having here. However, after this discussion you guys, I now have a problem with saying the field is weakening, because of the permittivity of space remaining unchanged. It seems like the new space that enters our universe comes prefabricated with field conductivity and even field energy (potential- the gravitational field can be bent to different degrees and will regain form). - Yes I am aware I am referring to the field as being real. True. In fact the appearance of prefabricated space really suggests it's not. I had always assumed that the new space acquired the properties of the old space, thus leading me to think it would dilute it - it appears not so. If any theory is wrong, according to observational and experimental data, then it is modified and/or discarded and a new theory formulated that better describes the universe around us. We know gravity exists...we have two models that describe those effects to varying degrees of precision, and the knowledge has taken us to the Moon, sent probes to all the planets, and enabled us to understand the universe reasonably well. I agree with you Beecee. I meant if disproven/superceded and it was still being used as a tool then it was a convenience, but no longer a tenable theory. I don't know if I saw you Feyman video on magnets, although I do have vague recollections of watching an interview where he talked about them to a reporter (you might have put me onto that last time). Always good to read your comments.

I'm rushing a bit as I'm already late for work, but how do you know we are in an infinite system? Multiverses, an singular infinitely spread universe, what is your basis for saying this?

I can't find the quote I'm after with this, but you said that space could still be infinite if we consider it as starting at the BB? Do you mean infinite expansive potential or infinite at the time of the BB?

So what you're saying is that a theory is a philosophy about how things work, and so long as it the ball still comes out chute B then alls good, it doesn't really matter how it got there. I take your point it seems reasonable, but I also disagree strongly with it. We find for example that while the philosophy can predict the outcome for one event, it may be completely wrong for another. The theory is thus incorrect, but may still be convenient. It seems at any rate that philosophy is inextricably linked to science. The good thing about science though, compared to philosophy is that we aren't trying to ponder the conscious self, because we have a real, live playground out there that we can throw rocks into. We know, for example that masses are attracted to each other. We say gravity resides in the gap between them. Best theories tell us it's a universal gravitational field that the masses are bending around themselves. Some masses are able to bend the gravitational masses better than others - the fact that the field can be bent to different degrees or bent at all tell us therefore that the field has properties that interact with physical forms. We know, according to best theories, that new space is mushrooming out into our universe causing it to expand. I was wondering the effect such new space would have on the properties of the fields - why don't they diminish? It seems that this new space has the same properties as old space- and that the properties - including the fields of old space are not diminished. Strange has pointed out that The permittivity of space is unchanged. We know that vacuum space has a quantum energy value. "According to present-day understanding of what is called the vacuum state or the quantum vacuum, it is "by no means a simple empty space".[1][2] According to quantum mechanics, the vacuum state is not truly empty but instead contains fleeting electromagnetic waves and particles that pop into and out of existence. In fact, the energy of a cubic centimeter of empty space has been calculated figuratively to be one trillionth of an erg (or 0.6 eV).[8] ]https://en.wikipedia.org/wiki/Vacuum_state The first law of thermodynamics states: The first law of thermodynamics is a version of the law of conservation of energy, adapted forthermodynamic systems. The law of conservation of energy states that the total energy of an isolated system is constant; energy can be transformed from one form to another, but can be neither created nor destroyed. https://en.wikipedia.org/wiki/First_law_of_thermodynamics So I guess the question at the heart of my question, is why doesn't an expanding universe contradict the first law of thermodynamics? Sorry about making it so hard for you guys.

I disagree. A theory is correct when it is correct. Any other time, a theory is simply a convenience. Well, Quantum Mechanists may argue the point with you on that one, but even is physics is a little too pointed a definition, certainly science will try to tell us what the universe is made of. I mean, if it doesn't then what are we waiting for, let's start a new branch of science right now.

I think you guys are the philosophers. I am not pondering the meaning of the word 'real' and having existential epiphanies as I chant mantras under a waterfall. I am referring to the sharp distinction between mathematics and physics. In physics, mathematics is an overlay, that attempts to explain what is in our universe. It is not the other way around. The universe is not an abstract imaginary form used as an overlay for mathematics. There is a difference between something being right or wrong, knowing and not knowing, existing or not existing. We know something we call gravity is causing objects with mass to be attracted toward each other. Our current best theories tell us this is because of a gravitational field. If you tell me the field is not real, then what you are in effect saying is that the theory is incorrect. This is incorrect. Physics uses as it's primary tool mathematics, in order to explain our universe - our very real universe. If you need a frame of reference for real, start with yourself and your world, and take it from there.

abstract adjective ˈabstrakt/ 1. existing in thought or as an idea but not having a physical or concrete existence. Although we can’t see these fields directly, we’ll find they are physically real and not just something scientists invent to concoct theories and make calculations. P77-78 Tales of the Quantum, Understanding Physic’s Most Fundamental Theory – Art Hobson. I do take your point Mordred. At the end of the day though this little old planet of ours keeps doing elipses around the sun and it ain't touchin' it. Something is out there... do you agree, or is it just volume?

So, like, when he said, "Fields are properties of space itself." P77, or "Although we can’t see these fields directly, we’ll find they are physically real and not just something scientists invent to concoct theories and make calculations." P77-78 he was just speaking philosophically?

Well, I'm not that familiar with him outside of this book, but a quick search says he is: Art Hobson Professor Emeritus of Physics University of Arkansas https://sites.uark.edu/ahobson/ I don't see how a professor of physics could get the basics so wrong.

I also like how, with the exception of BeeCee, everyone is staying well clear of the Art Hobson quotes. Once I am done with my description, and recorded all the wonderful and intriguing facets of the universe in mathematical language, will you then deny the whole thing exists?

No at all. My objection is having used the mathematics to model the universe, you then throw away the universe and say all that exists is the mathematics. We went and threw mathematics over the gravitation field so we could see how it works, now we have turn around and said the field is not really there at all, it is just a mathematical abstraction (unless you mean extrapolation, which is different) It seems to me you want to scrape off the icing and throw away the cake.