What is "the fabric" of space-time?

The fabric is reality itself There is actually only the fabric and nothing else. Admittedly, the fabric has multiple layers called fields, and it is one particular special layer that is usually referred to as the 'fabric of space-time', and the other layers give rise to what you would call matter and forces. In some ways, these matter and force layers are more simple, and we have a fairly good quantum understanding of these layers. The 'space-time' layer is more tricky, and we have yet to get a good consistent quantum description (although we do have some good ideas.) Our goal in theoretical physics is to have a single simple description of the all of the layers as one unified super-layer - a unified field.How do these layers give rise to what you would call particles, matter and empty space?Empty space is easy, the layer is simply flat in that region. You might think of a single particle as a bump in the layer, a point where the layer is raised up with respect to its neighbouring points. So a single electron would be a bump in the electron layer. An entire planet would be a huge extended bump across multiple layers, involving the electron, photon, quark, gluon layers, and several more. These munmps would then induce a bump in the space-time layer. The 'space-time' layer is called the metric, and it essentially defines a number associated with pairs of points in our layers. We call this number 'distance' and so this metric layer actually gives shape and form to our layers. A bump induced in this layer is essentially changing the distance between points around this bump, and thus 'warping' and 'curving' this shape and form. At the level of General Relativity, we say that mass is telling space-time how to curve. But from the point of view of the layers, bumps in layers rather unsurprisingly cause bumps in other layers.What are these layers/fields made of? They're not made of anything - they are the underlying reality - everything else is made from, or is an aspect of, these fields. However, they are very familiar - they seem to be objects that we know very well from pure mathematics. Now why should that be...?

Neither - both are concepts that arise from the fields. I'm not sure what this means, but I certainly do not see it containing any type of design. Mathematics is many things, but it is not 'designed'... There is an underlying state, yes, but hardly a design, whatever that is. If anything, I see existence as a necessary, unaviodable state.

The former

Why not? An open or flat (hence infinite neglecting topological compactifications) FRLW universe is no different to a closed (hence finite) FLRW universe from the perspective of age. Our Universe could be any of these three (with varying degrees of evidence), and all would have thei earliest point 13.7 billion years ago.You have obviously forgotten much of your graduate cosmology class...

Rubbish - these words don't even begin to apply. If anything, the fields are the only physical, material element of existence. and where exactly did I do this?

Hmmm, I think I have to repeat... and where exactly did I do this?And please stop crow-barring the word "design" into everything - it is meaningless. Do you realise how hilarious this is? It's not that you are desperate to find design in every aspect of the Universe - that wouldn't be too bad. It's that you utterly insist that it is there, and the rest of us are too blind, too stupid, or too desperate to avoid any hint of a creator to see it. How can communication be profitable? I've already stated how I describe it - mathematics.

ADMIT??? I'm not admitting anything. A question was asked and I was explaining.The ocean has waves - does that mean that the ocean is made of waves? That, that makes up the Universe.

PaulK has a very good understanding of what I was saying - you do not, as is abundantly clear by what I am quoting here.

Yes, this is a reasonable description of GR. GR treats space-time and matter as two different entities. I have been explaining the unified picture, where GR and matter are both aspects of some super-fundemental master field. It is the search for the consistent physical theory of this unification that is at the heart of much of modern theoretical physics. Yes, this is true. But mass acting on space-time is very different. 'Forces' concern action-at-a-distance. Mass at a point acts on space-time at that point. The wider-area effect on space-time has nothing to do with the mass, but the properties of space-time. In the usual ball-bearing on rubber sheet, the ball creates the displacement in the sheet at the point of contact, but the surrounding depression is a result purely of that local displacement and the elastic properties of the sheet - it is nothing to do with the mass itself. A graviton is simply the smallest possible fluctuation in space-time, a result of applying standard quantum thinking to GR. In terms of the rubber sheet, it is essentially the quantum of displacement. This not so much brings GR 'down' to the level of force, as brings electromagnetism 'up' from a simple 'force' picture, to the level of a geometric theory. And this must happen as we expect all of the fields (space-time, electromagnetism, strong, weak, matter) to be different aspects of the one unified field.

Please, no replies to this message that do not bear directly on the topic. --AdminRandman, the reason I do not like replying to you is the because of the constant misrepresentation - either of myself or of the ideas I have presented. This becomes very tiresome, especially after two to three years of the same.Just now you have repeatedly and falsely stated that I described the fields as 'nothing'.Right here you have declared that when I have done no such thing.You repeatedly ask me questions that I have already answered, claiming that I have yet to answer! No, you are not still waiting. You have been told repeatedly. I would describe 'it' mathematically, and characterise that 'something' as mathematics. That is all there is. If you want another word, then it would certainly not be design. If anything, in my mind, it would be inevitability. Already answered. That that makes up the Universe is 'physical'.Are you ever going to try reading my answers? Or do you just prefer to claim that I haven't answered them?Edited by Admin, : Add a moderator request.

My best ideas have always come while decompressing Thanks for the compliment. Yes - Wheeler long ago wanted to unify matter with the gravitational field, in a study called geometradynamics. It was compelling, but couldn't fully reproduce the properties of fermions (matter). The extended idea is to use separate metter fields that eventually unify with the gravitational field along with the other gauge (photon, gluon, etc) fields. Good question There has been a rather interesting paradigm shift over the past fifty years. Physics was always concenrned with the modelling of the parameters of physical objects with mathematics. This is the core of Gallilean and Newtonian mechanics, Kinetic Theory, and later with Relativistic Mechanics and Quantum Mechanics. However, as we started to look at Quantum Field Theory, we started to notice that it was no longer the parameters of some physical object that was being described mathematically - it was the object itself. An electron is not some 'ball' that has such and such properties. *only* the properties exist. Once we have decribed the properties mathematically, there is nothing left over to say 'and that's the thing we are modelling'. Contrast this with the mechanics of a ball bearing. It is very difficult to convey just how astounding this is - to reach the bedrock of existence to find that we have run out of 'blobs' to describe. Distinctions are not made, as a distinction in many ways would be unparsimonious - none is required. That's not to say we are at the final level, not by any means. But the levels are now simply layers of intertwined mathematics. And if 2+2=5, how would normal arithmetic work? Mass cannot 'appear'. So I cannot describe how space-time would respond because its occurance demonstrates that what we know of space-time is wrong! Mass is simply a measure of the energy in a volume. But yes, disturbances to space-time, say caused by a binary system, propagate outwards at the speed of light. Not quite - the motion of an object through space is purely dictated by the curvature of that space. That space, however, will be curved by both objects. True, except this becomes very difficult, if not impossible, because of the complexity of the situation - this is non-perturbative, or exact, theory. Much easier is to fourier decompose the field and simply work on individual fourier modes. We can then hopefully build these modes back up again to see the big picture. We have a term for these fourier modes - we call them particles Individual gravitons are phenomenally hard to detect - we probably never will. We haven't even managed to detect unambiguously an entire gravitational wave, never mind one tiny quantum of such a wave! Excellent question (what was that about stupidity?)All objects have a 4-velocity, and these 4-velocities all have the same magnitude - c. In free space, if you are not being acted on by any forces, your 4-velocity has components (c,0,0,0) which in loose translation means that you are travelling at the speed of light in the time direction. What we call 'motion' is a rotation of this vector out of the pure time direction, so that there is a (very small) component in the spatial directions. Thus it is now clear why there is a limit to 3-velocity - it is simply a projection of a rotating 4-vector of fixed magnitude. Now, in curved space-time, what you think of as your time direction *here*, may well not appear to be the same direction over *there*. So you may well see someone else 'moving' but as far as they are concerned, they are 'still'. The obvious example of this is someone in orbit watching someone falling radially towards the earth. Both have their 4-velocities pointing purely in the time direction (both are 'weightless', i.e. experiencing no forces), but they have very different perceived motion. Both are simply following unhindered their respectives paths through time. Compare this with standing on the Earth. here you are being continually accelerated vertically, and you can feel the accelartive force on your body via your feet from the surface of the Earth pushing you up, as you try to follow your natural path through time, which actually points slightly inwards, towards the centre of the planet. So if straight up through time actually takes you inwards towards the centre of the Earth, then the surface of the earth must be travelling outwards, from a 4d perspective

This just bears repeating in case anyone is falling for some of the nonsense spouted elsewhere in this thread. Edited by cavediver, : No reason given.

Oh, so you're an expert on quantum field theory, are you? Obviously not, as this is completely incorrect. No, he's just talking bollocks to impress his lay-audience. He's obviously suceeding.

You show me where in any of Zeilinger's published papers that he states that "Entanglement operates outside of space and time,". Why would we care that QM breaks causality - it is not a relativistic theory!!! What the f'k do you expect? Why are you not pointing out that Newtonian Theory breaks causality? And who cares about Local Realism? That was abandoned long ago.The trouble, as ever, is you are so far out of your depth it's not funny. The only reason I bother posting is to ensure that the peanut-gallery isn't being taken in by your ill-informed blathering.

You show me where in any of Zeilinger's published papers that he states that "Entanglement operates outside of space and time,". Randman, quoting the words is very easy. Understanding this is a whole 'nother ball game. Leave it to the professionals. What was it I said in my last post?