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I think the word we're all fumbling for here when we say 'reality' is in fact 'ontology'. One of the most important lessons of 20th-century physics is, I think, Nature doesn't care a great deal about our entities. I think @swansont, @MigL, @beecee, and myself; and perhaps most eloquently @DrDon have drawn arguments along these lines. Nature is probably connected all the way down to the most fundamental level. That's why such a thing as unification of physical laws is possible in the first place. But distinctions emerge. It is the business of physics to elucidate what connections/distinctions appear/disappear, and when (at what scale) they are relevant. Entities don't present themselves as 'solid' immovable categories; rather, as useful instruments for the scale of description given. Terms as bosonization (a fermion can be seen as a pair of bosons with a 'twist' between them), dualities (a strongly-coupled interaction in one region of space can be seen as a weakly-coupled one on the boundary of that region) etc., strongly suggest that any entities that we may propose are simply instrumental, and what emerges as really robust are physical principles, patterns, rather than 'things'. Lorentz invariance, locality, unitarity, symmetries and conservation laws. Those are the main characters in this play. Weinberg was a master at bringing out how they interplay. Einstein was one of the most brilliant theorists of all time, but this revolution caught him at a point in his life when he was already too set in his --ontological?-- ways. Weinberg was able to take home the lesson much more efficiently for what the 2nd half of the 20th century physics needed. Maybe nothing is, and everything emerges, in some kind of bootstrap mechanism of substantiation of entities in a grand cosmic scheme of which the building blocks are actually patterns and principles, and not things. --I'm getting blah, blah. I'm also glad that professor Lincoln has spent some time among us, be it ever so briefly.

Sure, if you're interested. Let me PM you as soon as I have the time to write some words to explain what it's about. It would be quite off-topic and improper here.

This is an approach to ontology that is sometimes called a "bundle theory, " and goes way back to David Hume. Physical entities, rather than having any sort of substance, are construed as bundles of properties. They ARE their properties, rather than some thing that HAS properties. (plus one to your whole post, BTW) I think bundle theory is quite germane to modern physics, which as @swansont noted is pretty much a black box operation insofar as Aristotlean "stuff" is concerned.

The above was in response to my: QUOTE Near the end of Lecture 15, "The Awesome Evidence for General Relativity", at the 28:30 mark, Prof. Lincoln perorates: "I hope I've convinced you that there are very good reasons that general relativity has been very clearly validated. I mean I know that it's very weird to think of gravity as the bending of space and time, but it's just literally impossible to believe otherwise these days." So, pace other contributors to the thread--perfectly entitled to their opinions--who have told us that no one knows what gravity is, or science cannot answer questions such as what gravity is, clearly, Prof. Lincoln does not share your skepticism. The good professor is not only telling us what gravity is (It's the bending of space and time), but that to believe that gravity is anything other than the bending of space and time is not possible. A tad hyperbolic if you ask me, but hey, I toss it out here for consideration. UNQUOTE Since the professor is now with us, perhaps he'd be kind enough to expatiate. Am I reading too much into what you said, sir?

Join the club! I have been known to edit my posts three or four times!

Indeed, thanks for pointing that out. I am notoriously bad at proof reading my posts as they are generally more of a stream of thought thing that I do between doing other things, so my general apologies for having to put up with them. I did correct it now but now am unsure whether I should have. Anyway...

I always found that that to be bit of a a convenient excuse. See, folks do not have abhorrent believes, but it is because someone made them so. There are a few issues with that statement. The first is the use of political correctness of a pejorative of the right to criticize the left. In reality, there has always been an Overton window that determined what is palatable. The phrase PC has been weaponized by the right to shut down every criticism (justified or not) that stem from progressive ideas. In all honesty neither side is doing well with fostering dialogue, however it seems to me that the right has created a whole ecosystem to systematically shut them off from discourse, which is now exemplified by the presence of an alternative right-wing reality in which things like, say global warming or COVID-19 simply does not exist and antifa has taken over the government. If you want to follow this route and where the origins are, you won't find those in the opposite camp. There is a large body of research now which discusses this in more detail, but in short, it is not a reactionary or even new phenomenon. It follows a long tradition of right-wing patterns which elements of authoritarianism and xenophobia which are rolled into a zero-sum worldview. The only new thing is really the amplification of signals from all sides via the internet which allowed folks in fringe to create and maintain their own alternative universe. It should also be noted that one of the hallmark of these fringes is the duality of a) being heroes of their narratives but b) at the same time being downtrodden and forced to action by the enemy. The narrative that the left forces them to believe in crazy stuff because they have taken over mainstream media and science, is just another element to it.

One other thing - magnetic dipole fields drop off as 1/r^3, while gravity drops off as 1/r^2, so even if you could get a solar system to work (you can't have everything attract, as Janus pointed out), it doesn't follow the pattern we see — the planets and moons etc. follow a 1/r^2 attraction.

Magnetic fields have polarity. You have a North and South pole. Like poles repel each other and unlike poles attract. The poles always occur in pairs (a magnet will always have both North and South poles) Because of this, it is possible to arrange the poles in such a way that all the poles cancel each other out and you get no net attraction or repulsion. Gravitational fields have no polarity. They are purely attractive; mass attracts mass. The more mass, the greater the attraction. There is no way to arrange things to get a repulsion or cancellation. But, compared to magnetic fields, gravity is very weak, and it take a considerable amount of mass for this attraction to be easily measured. But, as swansont has already noted, we have measured gravitational attraction between relatively small masses. The earliest such measurement was done by Henry Cavendish in 1797. He took two brass* spheres which were placed on the ends of a long rod which, in turn, was hung from a piano wire at its midpoint. Two more larger Brass spheres were placed near the suspended spheres so that any attraction between them would rotate the rod and twist the piano wire. Then, by measuring how much rod rotated, and knowing how much torque it would take to twist the wire by that amount, he could work out just how much force was attracting the spheres to each other. And since he also knew the mass of the spheres, he was able to derive the constant of proportionality for gravity. This, in turn allowed him to work out the mass of the Earth. Up until then, while we could measure how much gravitational force there was between the Earth and an object of a known mass, and we knew how far the object was from the center of the Earth, we were still left with two unknowns: the mass of the Earth, and the gravitational constant of proportionality. Knowing either one would allow us to work out the other. Cavendish's experiment gave us the value of the gravitational constant, which meant he could now calculate the Earth's mass. Because of this, Cavendish has been referred to as "The man who weighed the Earth". *he used brass as it had no magnetic properties that could have skewed the results.

OK...this is Don Lincoln here. My name was invoked and a little bird came and suggested I pop in. I have not read all of the chat above. Regarding gravity and belief. First, belief is a non-scientific word....or at least it has lots of really ridiculous connotations. When a scientist says that they believe in a theory, they're just being sloppy. (And I include me in that. But language is language and we do the best we can.) "Belief" to a scientist simply means in this context, that the theory is consistent with all relevant known data and we can take it as an approximation of the truth. Now, on gravity. It's very clear that Einstein's formulation is more accurate than Newton's or, for that matter, any other suggested theory of gravity. It's also eminently clear that general relativity fails at small sizes and very high gravitational fields. For that, we will need a theory of quantum gravity. Some ideas have been put forward, but none have been validated in any way, meaning to all intents and purposes, we have no believable theory of quantum gravity. However, given the established validity of general relativity, it follows that that when quantum gravity is evaluated for gravitational fields not strong enough to manifest their quantum behavior, that the predictions will be effectively identical to general relativity. From that, we can infer that the bending of spacetime will be valid in quantum formulations as well, although there may be additional explanatory insights. Accordingly, I feel quite comfortable in saying that I believe in general relativity in the realm in which it is applicable. Similarly, I believe in Newtonian gravity in the realm in which it is applicable. After all, we shot the New Horizon probe to Pluto - traveling billions of miles, passing by several planets, and NASA hit a target 10 km in size. Newton works. Einstein works. Well, until they don't. That's all of science. Theories work as long as they work. One other piddly point. Our current understanding of gravity is qualitatively different from the other known forces. Sure. Some of you have been discussing the meaning of the word force. Classically, it means something that has the potential to cause an object's velocity to change according to some reference frame. At the quantum level, it has a somewhat different meaning. There it means that the phenomenon can effect some sort of change, be it changing velocity or causing particle decay. The fact that the word has a nuanced meaning depending on the size scale at which it is being evaluated implies that the word is fuzzy and anybody trying to nail it down, will fail. This brings up a more important point is that the mapping of words onto scientific concepts is a dangerous endeavor. It is highly unlikely that any word can be mapped into a concept so well that it is impossible to find an exception. There will aways likely be a qualification of some sort. Accordingly, don't hold onto words very hard. They will fail you. Instead, understand the more nuanced scientific principle for which the word is nothing more than an imperfect and ultimately inaccurate placeholder. For the person who complained about the videos being at a commercial site. Well, I've worked for over three decades learning this stuff. I spent half a year writing the lectures, which comprise 12 hours of clearly-explained advanced science. I spent a week filming the project and many hours ensuring that the quality of the video and audio product was high. And someone has the temerity to suggest that I and the production company shouldn't be compensated for that effort? It's like whining that someone won't come and paint your house. Go ahead - enroll in the streaming service - you will have access to an astonishing amount of knowledge and expertise, translated in such a way that non-experts can understand a portion of the more complex ideas. BTW I was a solid presence at SPCF for a long time, but I will not be a regular here. I have just contracted my 5th or 6th book and that will take enough time that active involvement here is simply not in the cards. Cheers....

In the reality of prison systems, there are further considerations beyond punishment. Being locked in a cage does not 'fit' any crime, except kidnapping. The only lesson incarceration teaches is: "We are afraid of you." That's not something I particularly want to teach to an angry boy, growing into a bitter man behind bars. All crimes may have appropriate fitting punishments, but very few of those are ever tried. For instance, parole is not an alternative to prison: it's just finishing the prison sentence outside in order to liberate prison space to punish somebody else. The aftermath of incarceration is often worse for the ex-convict that the prison sentence, because now he's expected to be independent, even though he isn't really free, doesn't have the rights of a citizen, can't fit into a community, isn't accepted, isn't hired for a decent job; can't be respected or useful or happy. Which explains the recidivism rate: we are taking individual law-breakers and turning them into career criminals. (No, not the depraved 0.1% of criminals that belong in a maximum security hospital, but the 99.9% who commit rational or impulsive ordinary crimes.)

Turn it the other way around - if healthcare workers refuse vaccination and they become a vector for Covid transmission, should they be legally liable for medical/funeral/other expenses of those who get sick as a result? Should their employers face legal sanctions for failure to insist on vaccination? Seems to me there are duties of care that override any personal "free" choice.

Mae West would have been impressed. She said ... "Is that a pistol in your pocket, or are you just glad to see me ?" You have a whole universe in yours !

@joigus A very thoughtful post you've offered there with a great deal to ponder. As it happens, and for all it's worth, my own proclivities in these matters would be located somewhere towards the antirealist end of the spectrum, which would seem to put me in good company here. That said, the realists do have some pretty powerful arguments on their side that I think have to be acknowledged and addressed. So let me play devil's advocate here for a while. (Bliss on tap! Ooh ah!) Take a look, if you will, at the following list of subatomic particles which, we are told, have been discovered since the year 1800. https://en.wikipedia.org/wiki/Timeline_of_particle_discoveries Now, I assume the entities on the list, with the exception of any serendipitious discoveries (X-rays?) which just kinda popped up out of the blue prior to starring in any bright spark's PhD dissertation, were originally posited as theoretical entities, perhaps regarded as "useful fictions" to begin with, much as atoms were until roughly a century ago. We might have been told that to enquire into the existence of such spooks was to perpetrate the heinous sin of metaphysical speculation. Science can't answer questions like that. Just shut up and calculate, etc., etc. Given, however, that these spooks were subsequently "discovered" . . . well, to my untrained ears, discovery pretty much entails reality. And if they're real, is it not the case that physics is--at least to some degree--describing reality for us? Speaking as a physicist (I assume you are), do you consider the entities on the list to be real? If not, why not? If yes, how do you reconcile these additions to our ontological inventory with the passage of yours which I have quoted below?

Maybe it’s because theres different types of gravity

No, it doesn't. Your own personality determines how you communicate - including whether you can adapt your communication style to different personalities. The fact that a lot of executives buy into something doesn't prove that something is useful; it just means that executives tend to latch onto the latest fad, buzz-word and "cutting-edge tool" in order to avoid making actual independent decisions and make fewer attributable mistakes. Of course it is. It's also quite common to to believe that the sun goes around the earth and the Corona virus vaccine contains nannomikes. No, that's not a fair comparison. Executives are not wingnuts; they're just conformist and credulous. They'll buy whatever they can be convinced will improve their effectiveness. Since the psychologists are committed to this fad, the executives take that as proof that it works: after all, it's Scientific. .... is it?