How does gravity work?

How does science work? And what's all this about quantum mechanics?

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wtf
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Re: How does gravity work?

Post by wtf »

uwot wrote: It's all in the blog.
It's what's in your blog that led me to these questions and issues. Maybe I just don't understand your blog. As far as I can tell you are just saying that gravity is or is caused by the density of matter. But we already know that. You haven't explained anything. It's like saying fire is hot stuff from the big bang and ice is cold stuff from the big bang and gravity is all the stuff from the big bang.

In other words you are saying that matter returns to its natural place. This is exactly the viewpoint of Aristotle on gravity.
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Cerveny
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Re: How does gravity work?

Post by Cerveny »

uwot wrote:
Cerveny wrote:...
There would be found a few unimportant trinkets: "dark matter" (70% of the Universe) and eighty years of hopeless quantization of GTR...
You are getting dark matter mixed up with dark energy. Dark matter is reckoned to be something shy of 30%, while it is dark energy that is almost 70%; it is the left overs from that which is the visible universe.
Both are posited to account for the observable behaviour of the visible universe. In the case of dark matter, the issue is that galaxies do not contain enough visible matter to generate the gravity that would prevent them flying apart at the rate they are spinning. Dark energy is the hypothetical explanation for the fact that the expansion of the universe appears to be accelerating. The clue is in the name, the cause of these phenomena is not clearly understood, hence 'dark'. As it happens, they are likely to be the subject of my next post.
That GR and QM aren't easily compatible has no bearing on the fact that both describe what they describe extremely accurately.
Anyway, do you have an explanation for the phenomena?
Both mentioned problems follow from wrong gravitational theory. GTR does not suppose discrete structure of physical space, its dynamical "viscosity" and repulsive gravitational force (antimatter). BTW, I really very appreciate your effort and ability to express your point of view at mainstream physics in your blog:)
uwot
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Re: How does gravity work?

Post by uwot »

wtf wrote:Maybe I just don't understand your blog.
Maybe I'm not explaining it very well, but it's meant to be in the form of a logical argument; each post presenting the evidence for a particular premise, or clarifying a point. The structure is more or less as follows:
Where did the universe come from?
The red shift of galaxies is best explained by the Doppler effect, which implies that the universe is expanding.
By reversing the process, you have a contracting universe, but there is no apparent cut-off point where the universe had a particular size and calling that the beginning. Bertrand Russell made the point that there is no logical contradiction in claiming that the universe began 5 minutes ago, complete with the holes in his socks. That might seem ridiculous, but claiming that the universe was created with any size or structure is problematic for the same reason.
The conclusion is that the smaller and simpler the starting point, the less trouble you have explaining it. That doesn't explain why there was a big bang, frankly, I have no idea. As has been pointed out, Lawrence Krauss has attempted to show that you can get something from nothing, and there is no end to the religious nuts who will trot out some version of the ontological argument. In my view, the former is mathematical sophistry, and the latter is just piss poor sophistry.
What we do know is that there is a bunch of phenomena that looks like a universe.
What is the universe made of?
Assuming the simplest origin of the big bang, an infinitesimal point with one component, it is further assumed that this point is actually made of something identifiably 'physical'. To mathematical physics, the relevant properties of quantum fields are the demonstrable effects they have on matter. The maths is very difficult, but breathtakingly accurate. There is no question that the fields of influence described by physicists are real. The philosophical question is what is the mechanism that causes the influence? According to quantum field theory, matter/energy are just excitations in various quantum fields. Following on from the assumption that the universe is actually made of something, fermions are one type of excitation...
What are photons?
...and bosons are another.
How do prisms work?
This is establishing the principle that particles travel through different media at different velocities and that the acceleration manifests as a change of direction, where the incidence is other than 90 degrees.
A medium such as air can be condensed and rarefied, thereby changing its refractive index...
How does gravity work?
...big bang stuff is a medium more like air than glass, so its refractive index is dependent on its density. The density diminishes according to an inverse square law, so does the refractive index, so does the acceleration, so does the change of direction, so does gravity.

There are a number of assumptions and extrapolations involved, any or all of which could be wrong. We simply don't know whether the universe is actually made of some material with physical properties, but we know a lot about how it behaves. All I'm doing is taking that behaviour and slapping it on to some actual stuff.
uwot
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Re: How does gravity work?

Post by uwot »

Cerveny wrote:Both mentioned problems follow from wrong gravitational theory.
Depends what you mean. Einstein's field equations work very well, so any alternative has to be at least as good. Whether the mechanism he proposed, warped spacetime, is the actual cause is a different issue. It may or may not be, but the mathematical model based on that hypothesis is very accurate.
Cerveny wrote:GTR does not suppose discrete structure of physical space, its dynamical "viscosity"...
Yeah; that's more or less the point I was making to wtf.
Cerveny wrote:...and repulsive gravitational force (antimatter).
I don't know of anyone who claims that dark matter is anti-matter. In fact it is demonstrable that anti-matter is subject to gravity, exactly like regular matter.
Cerveny wrote:BTW, I really very appreciate your effort and ability to express your point of view at mainstream physics in your blog:)
Thank you for saying so.
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Cerveny
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Re: How does gravity work?

Post by Cerveny »

uwot wrote:
Cerveny wrote:Both mentioned problems follow from wrong gravitational theory.
Depends what you mean. Einstein's field equations work very well, so any alternative has to be at least as good. Whether the mechanism he proposed, warped spacetime, is the actual cause is a different issue. It may or may not be, but the mathematical model based on that hypothesis is very accurate.
Cerveny wrote:GTR does not
Cerveny wrote:...and repulsive gravitational force (antimatter).
I don't know of anyone who claims that dark matter is anti-matter. In fact it is demonstrable that anti-matter is subject to gravity, exactly like regular matter.
- Can you name any (model)? But please do not mention GPS (GTR is not used here at all) and do not mention a calculation of the orbit of Mercury (the same formula had been clasically calculated by Paul Gerber before Einstein)
- I only critize that GTR does not work with gravitational repulsion. I do not compare dark matter with antimatter.
wtf
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Re: How does gravity work?

Post by wtf »

uwot wrote: ...big bang stuff is a medium more like air than glass, so its refractive index is dependent on its density. The density diminishes according to an inverse square law, so does the refractive index, so does the acceleration, so does the change of direction, so does gravity.
I don't think that's true in any way other than metaphorical. Do you mean all this as a metaphor? The refractive index of big bang stuff? Metaphor or analogy maybe, but not actual physics as far as I know.

ps -- I found this thread over at PhysicsForums. They were discussing whether gravity is refraction. I didn't read it all. I don't think they agree with you but at least someone has made the same suggestion as you have. https://www.physicsforums.com/threads/c ... ct.119096/
uwot
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Re: How does gravity work?

Post by uwot »

wtf wrote:The refractive index of big bang stuff? Metaphor or analogy maybe, but not actual physics as far as I know.
More analogy than metaphor. This is what Peter Higgs said shortly after the discovery of the boson named after him:

"The trouble is that when I try to explain it in the way I would prefer, there are so many people that don’t know the 18th-century physics that is needed. I explain it as being somewhat like the refraction of light through a medium.

The model I came up with in 1964 is just the invention of a rather strange sort of medium that looks the same in all directions and produces a kind of refraction that is a little bit more complicated than that of light in glass or water. This is a wave phenomenon but you can translate it into the language of particles by waving your hands and muttering the magical names of Einstein and de Broglie [who formulated the idea that waves could have particle properties, and vice versa]." https://www.newscientist.com/article/dn ... by-a-wave/

What I'm trying to do is introduce the concepts of physics using everyday experiences. This inevitably results in simplification, but the basic ideas are completely mainstream physics. The problem is, as Higgs alludes to, even many physicists don't understand the physics, in particular, they sometimes don't understand the difference between fields of influence, which are their nuts and bolts, and physical fields. This goes back to Newton and hypotheses non fingo, he couldn't tell you why gravity works, but for the purposes of physics, that doesn't actually matter. Same with Einstein; he couldn't tell you why matter warps spacetime, but the field equations work, so why should physicists care? Some do. Some don't. Anyway, rather than clog everything up with different quantum field theories, you can, in my opinion get a grasp of what they are arguing from the drawings of a stickman, as I use. If you want to understand it in depth, the best thing to do is enrol on a physics degree course.
wtf wrote:ps -- I found this thread over at PhysicsForums. They were discussing whether gravity is refraction. I didn't read it all. I don't think they agree with you but at least someone has made the same suggestion as you have. https://www.physicsforums.com/threads/c ... ct.119096/
They were talking about gravity waves refracting, which is slightly different, but thank you for the link.
wtf
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Re: How does gravity work?

Post by wtf »

uwot wrote: More analogy than metaphor.
So after all this you agree that you are not talking physics, you're just making an analogy. Like a bowling ball on a rubber sheet deforming a coordinate system drawn on the sheet. Not physics, but rather a fable for the tourists.

Yes? After all this back and forth you admit this?
uwot
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Re: How does gravity work?

Post by uwot »

Cerveny wrote:- Can you name any (model)?
I think you mean test. Well, the detection of gravity waves by LIGO is one.
Cerveny wrote:- I only critize that GTR does not work with gravitational repulsion.
It's not that GR doesn't work with gravitational repulsion necessarily, there is clearly a phenomenon that is not predicted the theory. Nonetheless, GR still works very well on the scale that we can measure it under controlled conditions.
Cerveny wrote:I do not compare dark matter with antimatter.
Fair enough.
uwot
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Re: How does gravity work?

Post by uwot »

wtf wrote:
uwot wrote: More analogy than metaphor.
So after all this you agree that you are not talking physics, you're just making an analogy. Like a bowling ball on a rubber sheet deforming a coordinate system drawn on the sheet. Not physics, but rather a fable for the tourists.

Yes? After all this back and forth you admit this?
Hm. Is that the thing that matters to you? In the rest of the post I said I am trying to introduce the concepts of physics using everyday experiences, which inevitably involves analogy. The use of the prism is an analogy, for instance. But as I also say, I think it is probable that the universe is actually made of something material; so in that sense, big bang stuff is just a name for whatever that material is and not an analogy in the way that a rubber sheet is a two dimensional representation of four dimensional spacetime. If it helps, I have no objection to you substituting 'spacetime' for 'big bang stuff'.
Wyman
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Re: How does gravity work?

Post by Wyman »

wtf wrote:
uwot wrote: More analogy than metaphor.
So after all this you agree that you are not talking physics, you're just making an analogy. Like a bowling ball on a rubber sheet deforming a coordinate system drawn on the sheet. Not physics, but rather a fable for the tourists.

Yes? After all this back and forth you admit this?
Reading through this thread, I was waiting for you to say something positive - i.e. 'talk physics.' But all I see are polemics. How do you distinguish 'doing physics' from metaphor or analogy when talking of the different models out there? Engineering GPS satellites, nuclear plants, designing ballistic missiles? When physicists try to talk about the origins of the universe, they seem to me to be grasping at metaphors as well. I think the good ones admit as much.
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Re: How does gravity work?

Post by uwot »

Wyman wrote:Reading through this thread, I was waiting for you to say something positive - i.e. 'talk physics.' But all I see are polemics.
Well, this thread relates to a blog, which you may or may not wish to read, but this is a philosophy forum, after all.
Wyman wrote:How do you distinguish 'doing physics' from metaphor or analogy when talking of the different models out there?
Personally, I think helps to distinguish between physics and philosophy. An example I sometimes use is general relativity and the difference between the field equations, which is physics, and the warped spacetime model it is predicated on, which may or may not be true, but makes no difference to the efficacy of the maths. Taking an instrumentalist view of physics, spacetime is metaphysical, hence one's attitude towards it is philosophical.
Wyman wrote:Engineering GPS satellites, nuclear plants, designing ballistic missiles?
Sponges, bricks, prisms, surfboards and cars as it happens.
Wyman wrote:When physicists try to talk about the origins of the universe, they seem to me to be grasping at metaphors as well. I think the good ones admit as much.
No doubt, but if you read the blog, you will see that while I use analogies to explain specific concepts, I don't make any claim about the origin of the universe.
Wyman
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Re: How does gravity work?

Post by Wyman »

uwot wrote:
Wyman wrote:Reading through this thread, I was waiting for you to say something positive - i.e. 'talk physics.' But all I see are polemics.
Well, this thread relates to a blog, which you may or may not wish to read, but this is a philosophy forum, after all.
Wyman wrote:How do you distinguish 'doing physics' from metaphor or analogy when talking of the different models out there?
Personally, I think helps to distinguish between physics and philosophy. An example I sometimes use is general relativity and the difference between the field equations, which is physics, and the warped spacetime model it is predicated on, which may or may not be true, but makes no difference to the efficacy of the maths. Taking an instrumentalist view of physics, spacetime is metaphysical, hence one's attitude towards it is philosophical.
Wyman wrote:Engineering GPS satellites, nuclear plants, designing ballistic missiles?
Sponges, bricks, prisms, surfboards and cars as it happens.
Wyman wrote:When physicists try to talk about the origins of the universe, they seem to me to be grasping at metaphors as well. I think the good ones admit as much.
No doubt, but if you read the blog, you will see that while I use analogies to explain specific concepts, I don't make any claim about the origin of the universe.
My comment was directed at the other guy - wtf. Sorry I wasn't clear.
Wyman
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Re: How does gravity work?

Post by Wyman »

I have a question. You talk of a mathematical model of a physical model of the universe. Why two models? Why not just a mathematical model?

I remember watching a video of a Feinman lecture about models. He presented two models of gravity in which the maths were the same. He basically said that the physical models were merely psychological tools for solving problems. He distinguished two philosophies towards models - the Greek, which is deductive; and the Babylonian, which is ad hoc - bits of model here and there, changing from one to another as the need arises. He advocated for the latter, claiming the Greek philosophy is artificially limiting. Interesting lecture, it's on youtube.
wtf
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Re: How does gravity work?

Post by wtf »

Wyman wrote:I remember watching a video of a Feinman lecture ...
Thanks Weiman.
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