General relativity

Let me express in another way why Michele78 is right.

Physics deals with measurements of distance and time. The concept of space-time is entirely about the relationships between different such measurements. The concept of space is merely part of that of space-time, and can never be separated entirely.

So to say "space does not exist" is first of all to forget 20th century physics (by forgetting its inextricable relationship with time) and secondly to be in denial about the fact that experiments confirm in great detail the predictions of general relativity about the relationships between different measurements of time and distance.

"I do not reject geometry, I said there is no space"

Uh?! Sorry, but what geometry is about for you?

Geometry *is* the mathematical description of space. Then you decide the dimensionality of your space. If you discuss space, in any form, you are doing geometry. Oversimplifying a bit, "space" is a nice geometrical construction in your head, which is useful to predict and compute  measured distances between objects and how they change in time

So, "geometry without space" is a totally self-contradictory, nonsense statement.

If you do classical mechanics, you use coordinates (x,y,z) to describe positions, differences of these to define distances, derivatives w.r.t. time to define velocities, and so on. You are then working with a 3D Euclidean space.That's your geometry

You can of course add/remove dimensions and/or change the definition of distance, which is basically working in a curved space. If you are happy with geometry, you are happy with GR, because that is what GR is: geometry. And that is what space-time is, just geometry in your head. If this geometry is successful to predict the distances and the motions you measure with your ruler and your clock, then your theory works.

If you want to work in a grid with discrete values of time and x,y,z, you have however to redefine all properties of your objects, and, I stress that again, what you call particles do not coincide with any definition of particle in Physics.

You seem to lack arguments. Still waiting for a mathematical definition of particles and fields, and related quantities, without space. Still waiting for examples of experimental tests of your "theory".

agreed.

Just to specify better, if one says that on all tested scales space time is  continuous, and geometrically described by GR (with some possible, specific, modifications on cosmological scales, which however do not change the structure of the theory), but on very small sub-Planckian scales it might have a discrete structure, yet to be really understood, I would not object to that, of course.

Still, a "space particle" does remain nonsense. Space (-time) is where all physical events, particles included, are defined in first place.

It is also nonsense to invent particles with funny names, outside of any theoretical context and mathematical formalism, and without providing any, at least potential, experimental test that could reveal such objects.

I guess anyway, at this point, that keeping on with this discussion would just start an infinite loop with no hope for further improvements, or reciprocal understanding. Hence I will stop here and move on.

Ok, as I said, I think this discussion will never lead anywhere and I call myself out of it. I am just going to specify better what I was saying earlier, since it seems that it was interpreted in a misleading way. When I say stuff like  "spacetime is continous on tested scales, but it might have a discrete nature on small scales", the meaning is, of course, that spacetime can be mathematically described as continuous on observed length and energy scales. This successfully predicts observations. If there is a discrete nature of space-time (which is by no means a granted fact anyway; it is just a possibility arising in some fundamental models), this necessarily affects only very small, sub-Planckian scales. These scales are yet untested, and have no effect on current observations. Such discrete nature can be then totally ignored both when we study subatomic particle collisions at LHC, for example, and when we study the largest accessible scales in the Universe, or anything else in between these two extrema. 

It is the same -just to pick one example- as when we consider electromagnetic phenomena. We know that the electromagnetic field, at a fundamental level, requires a quantum description, which leads to energy being carried in "quantum packets" called photons. However, if we are dealing with macroscopic scales, it is perfectly correct (and the only reasonable thing to do) to describe light propagation in terms of classical waves, to use Maxwell equations and to adopt a classical defintion of the electromagnetic field. In this description, quantization never appears, and energy is continuously distributed in space. It is just that the typical energy of the systems under study are much larger than the energy carried by the single photon, so that the quantum nature of the field can be totally ignored.

Likewise, if you want to know the mass of the ocean you do not care that it is an integer multiple of the mass of a water molecule. You just treat the ocean as a continuous fluid with a given density.  

Or, another example, if we study motions of planets and satellites, or rockets, around the earth and in the solar system, Newtonian Physics is the way to go. Surely one does not use GR (unless for some effects, or for very high precision tests), which is equivalent to Newtonian Physics for small gravitational potentials. 

By "equivalent" one means once again that, when used to carry out calculations to predict results of experiments (the only thing that ultimately matters in Physics, and that decides whether a theory is correct or not), Newtonian Physics and GR predict the same numbers in this small gravity regime. And by "same numbers" one means that the differences between the two approaches are so small to be undetectable.

All Physics is like that. It is made of effective theories. Mathematical models that predict observations correctly, within a given range of length scales, energies, masses, and so on.

Michele;  " still space particle is nonsense, space - time is where it is ... "

Happy 100th anniversary.

Guess that means it may be another 100 years before most people figure out how wrong General Relativity really was.  Sure hope ever one is happy..

Back in the real world, there have been increasingly loud whispers in recent times about some exciting results from the attempts to detect gravity waves. It's now been announced that there will be a press conference tomorrow. As most people here know, gravity waves are a subtle and very precise prediction of general relativity which have never been directly detected, but have been indirectly confirmed as described in the OP of this thread.

Exciting, this! Like the confirmation of the existence of the Higgs by the LHC. I wonder how robust the results will be?

If it is true, the door to gravitational wave astronomy will be open.

It definitely seems true

Apparently it is a detection of GW from BH merging and people speak of >5 sigma evidence. We'll see tomorrow if rumors were accurate.

In order to have a "back in REAL world" , one must get real first.  There are no Black Holes.  BHs are a figment of General Relativity.    One can not detect GWs from a HB if there are none.   Not even with 100 sigma.   Black Holes are not at the center of a galaxy,  a center of a galaxy is at the center of a galaxy.  The centers are reasonably stable.  The centers do not disapear into an empty point and void of space as BHs are said too.