Markus Hanke

Basically, the concept is meaningful only if it is independent of the specific path taken between the two events. This requires the presence of certain symmetries - which not all spacetimes have. For example, consider what happens if the spacetime is not stationary, such as in a binary star system. The work required to escape to infinity from any point within this system depends not only on where that point is, but also on when the escape happens, and what specific trajectory is taken. In other words, it depends on the path taken through spacetime, the metric of which now explicitly depends on both time and space coordinates. As such it isn’t possible to assign a single unique value that signifies gravitational potential to any point in that spacetime.

I didn’t mean to suggest that. Of course this needs to be done according to the proper rules and procedures of differential geometry in spacetime - the language of exterior calculus naturally lends itself to this. I remember MTW has a section that shows the proper procedure to construct volume integrals on semi-Riemannian manifolds; it’s that I was thinking of.

In 4D, you account for both space and time. If a boundary is contracted in space, it is expanded in time by the same factor, leaving the overall volume in spacetime unchanged. Or to put it more technically - the volume element in 4D is an antisymmetric tensor, so any volume constructed from it by integration will be a covariant quantity.

Well, the universe is a 4D structure, yes. But my main point was that in order to find quantities that all observers can agree on (ie that are independent of reference frame), you need to always go into 4D. So, length (3D) and time (1D) depends on observer, but hypervolume (4D) does not, for example. So the ontology of objects in spacetime is 4D.

Perhaps I should have been a bit more precise - it’s measurements of length that are relational, and the relationship depends on angles and orientation in spacetime. In practice that means that length contraction is observed along the direction of motion, but not perpendicular to it. Thus, for example, the initially spherical gold ions in the RHIC become flattened disks in the lab frame - and physically behave like flattened disks at the point of collision. So no, shape also depends on the observer. If you want to know about properties that do not depend on the observer, you need to consider all four dimensions of spacetime, and not just 3D measurements. For example, the train you previously mentioned would trace out a (4D) hypervolume in spacetime between two given events; this would be a quantity all observers agree upon, even if they don’t agree on isolated measurements of space and time. Thus, ontologically there are covariant and invariant quantities - but only in 4D. You always need to consider both space and time. It’s only our cognitive habit of separating these that creates confusion and misconceptions.

It is meaningless to ask about “size” separate from a specific observer, since this measurement designates a relationship between two frames in spacetime. It’s not an intrinsic property. Thus there’s no contradiction, because we are dealing with relational properties, so the ontology of this is also strictly relational. In other words - all observers are right, but only in their own local frames.

This is just getting bizarre now.

Can you not see that you are going down a very slippery slope here? You are now starting with a conclusion (‘photons must be waves‘), and try to force available data to fit that predetermined solution. This is the opposite of the scientific method. The correct explanation is already given in the experiment which I linked - the rest of your post is just wild speculation that doesn’t even seem to be related to the specifics of the LHC setup, or even to any established particle physics. To be honest, I think we’re done here.

They have been observed at the LHC in March 2019, with a statistical significance of ~8 sigma, which is way above the ‘discovery’ threshold: http://cdsweb.cern.ch/record/2667214

I have quite fond memories of my years on the Atari ST...for all its faults it was nonetheless a great machine, with a nice community of users around it. I taught myself to program on it, in several languages. I was really into it at the time!

These two languages were designed for different purposes, and work according to different paradigms, so they are not easily comparable. There will be things that are easier to implement in LISP, and other things that are easier to do in Java; it really depends on what you are trying to achieve. I did some LISP programming back in the 80s on an Atari ST - I never warmed to the language, I found it tedious and obtuse, and quite hard to learn; but maybe that’s just because I was too used to BASIC, C, Modula-2, and Assembler.

Funny, I’ve had a similar experience. I’m generally good with languages (fluent in 2, varying levels in another 7, several more on my ‘to learn’ list), but French really didn’t do it for me, even after five years of formal study in High School.

This is not how a gravitational singularity is defined - the actual definition is that it is a region of spacetime that is geodesically incomplete. I should also mention that singularities are not all point-like, and that they technically are not part of the manifold. No. The type of black hole you appear to be discussing (there are many different types with very different properties!) exists in vacuum, so the energy density is everywhere zero. Also no. Geodesic incompleteness is an invariant property on which all observers agree. And the central message of relativity is actually the exact opposite - that the world is described in terms of covariant and invariant properties subject to certain symmetry groups. Yes it is. Gravitational waves are described by the same mathematical objects as any other gravitational field. They are essentially a time-dependent gravitational field that oscillates in a specific way. Every gravitational radiation field has a source by which it is generated, so this distinction does not exist.

I think you typed this just as I moved the thread

! Moderator Note Moved to ‘Speculations’ section.

I am genuinely of the opinion that all my replies were direct responses to something you posted, and didn’t ignore the salient points; and yes, I had to repeat myself - several times over - because there is only one mechanism explaining these observations, so there are only so many responses one can possibly give. How about the colliding gold ions at the RHIC, which I referenced earlier? I personally feel that’s an even better example, because the experiment can be repeated in a controlled manner in a lab, and contains fewer unpredictable variables.

The very title of the thread already gave it away right from the start, but I had been hoping that explaining the theory plus listing experimental evidence might have had some effect at least. Sadly though, at this point the best term I can think of to describe this thread is ‘sealioning’.

This appears to be better suited for a new, dedicated thread; it doesn’t quite fit into this discussion.

This isn’t a contradiction at all, because these are different observers performing a measurement the outcome of which is observer-dependent, since they’re measuring something that isn’t intrinsic to the train, but describes only their relationship to it. It seems to me that we are just repeating both question and answer over and over again, to no avail at all it seems. So let me ask you this - are you actually interested in the explanation, or have you made up your mind already that relativity must be wrong? Just be honest.

The invariance of c is a direct consequence of Lorentz invariance, so any experiment testing this symmetry would verify that finding. There is a large body of such experimental tests. But you don’t even need any reference to relativity for this, because it also follows directly from Maxwell’s equations - the propagation velocity of light in vacuum depends only on vacuum permittivity and permeability, and nothing else. So it is naturally invariant between frames, since these are fundamental constants. And I think we can all agree that Maxwell is not under contention.

The particles are one meter apart as seen from a specific frame of reference. A different observer will measure a different distance. All observers are right, in their own frames. A specific Length is thus a relational property, and not somehow intrinsic to the object. I guess-timate that this has been pointed out now at least ~10 times or so, in different ways be different posters.

I’m an amateur science enthusiast; I’m also a Buddhist monk. In principle you are right - the issue should not be of concern in Buddhism. In practice though it depends on which of the many schools you look at, and even who you are talking to. Many Buddhists very much do have various supernatural elements in their world view, or interpret some of the central ideas in supernatural ways; scriptural literalism and fundamentalism sadly also happens. In fact, those Buddhists who don’t do any of those things are very much in the minority. I personally see no issue (or else I wouldn’t be on here), since my ‘personal Buddhism’ does not contradict any scientific findings that I am aware of, and vice versa - they are very much dealing with two separate domains of enquiry, both of which are limited in their applicability.

Yes, of course. But what I meant here isn’t the maximum correlation (which is always 1 of course), but how it is distributed as a function of detector angle in the classical Bell experiment (graph taken from Wiki). You can see the quantum correlation is stronger than classical correlation (local realism):

Not when they are hitting the screen - they behave like particles there. They also behave like particles in other circumstances, such as eg the photoelectric effect. Apart from this being inconsistent with the specific experiment linked to by swansont, it also runs counter to double-slit type experiments done with quantum objects other than light, which don’t exhibit the property of polarisation. As already pointed out numerous times, the observed effects are independent of the nature of the quantum object - they happen with photons, but also with electrons, C60 molecules, or any other quantum object. The common denominator is always the availability of which-path information.

I must admit I’m confused about the last few comments. Entanglement is a correlation between measurement outcomes, in the sense that the multi-partite system is non-separable. Knowing whether a system is entangled requires one to take measurements on all parts, and then bring the results together and compare them. The only thing special about quantum entanglement is that the correlation is stronger than classically allowed.