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Post by Progenitor A on Mar 18, 2015 15:25:32 GMT 1
At very high densities inflationary theory says that gravity becomes repulsive not attractive. Yes, but obviously without any explanation else why do black holes not explode? We have been talking about negative gravitational energy, not force. Ah, but you went to some lengths to explain that gravitational energy is negative because of the direction of the gravitational force With these two misunderstandings (among others) your argument collapses. 'Fraid not old chap 1. I do not misunderstand the statement that inflationaary theory demands gravitational repulsion at high densities of matter. I simply question it - but of course there is no explanation of this strange phenomenon 2. You attributed negative gravitational energy to the direction of gravitational force, therefore if the force field reverse in direction, then logically the energy reverses to positive energy
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Post by mrsonde on Mar 20, 2015 7:18:22 GMT 1
You are saying that the Universe does, in reality, have dimensions, (space-time)? Yes. And probably others, of course, if string theory is along the right lines. Yes. The basic axioms of arithmetic and by extension set theory are I think understood now, since the 30s - they are so basic I would suggest that they apply to any possible world, not just the one that exists - hence their apparently purely ideal character. Geometry is different - there you generate entirely different universes according to your starting axioms. And I answered you. It is an affine manifold - giving the feature at least of the dimensions of space-time - that has a certain geometry that is able by its nature to generate energetic forms. Including us. We are able to understand that real world, at various levels of approximation, because of the fundamental nature of logic discussed above. We are yet to fully understand the nature of the geometry of that universe as a whole - when we do, if we do, all our various physical theories will be seen to be partial representations, largely arithmetical approximations that would be "true" if that geometry had been very slightly different. Those arithmetical results will remain, though no doubt made even more precisely predictive, but our conceptual understanding of them will be radically different. Many hypothesised empirical representations of those mathematical formulations will disappear entirely, seen as mere artifacts symbolically standing in for our lack of understanding of that real geometry - dark matter, for example, is my guess (implied at present by the arithmetical results of measurements using our current theories), or, probably the most fundamental concept in quantum theory and particle physics, the property of "spin".
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Post by mrsonde on Mar 20, 2015 7:40:21 GMT 1
Nay - Nick has confused himself totally by dragging in this purely speculative notion of gravitational repulsion. This wasn't his original contention at all, and it's not what is generally meant by "negative energy". What Hawking meant by it, in the quote he gave to support the idea that it was a respectable notion in physics, is purely and simply gravitational attraction, based on the observation that to accelerate requires energy - that is, Galileo's observation that inertial mass and gravitational mass are equivalent (satisfactorily explained as far as I'm concerned by GR, with no need for any hypothesis of "negative energy" - or "positive energy" for that matter - whatever.)
But here's a prime example of what I've been referring to in the little side discussion with F above. The idea that a rapid phase of expansion occurred at a very early stage of the universe seems indispensable, with our present theories at least. It's an arithmetically necessary implication, given our best measurements (of size, charge, gravitation) extrapolated back to that density. When or if we ever understand what the geometry of the universe is that will be seen to be necessary, not contingent - no hypothesised novel circumstances or properties will be required to explain it. Your proposed counter-example of a black hole is obviously along those right lines: no "repulsion" is required to produce a white hole from a black, merely the extension of the space-time metric into a separate manifold (a "Big Bang").
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Post by mrsonde on Mar 20, 2015 8:08:58 GMT 1
Though it's just occurred to me that in such a scenario such a new manifold, spatio-temporally separate but connected geometrically, would from our point of view have all the properties that we measure directly and equivalently reversed. From our point of view time would "flow" in the opposite direction, the charge of an electron would be the charge of a positron, matter would be anti-matter and vice versa, etcetera. In this sense I suppose there is some validity in talking of such a property as "negative energy". However - gravitation would still be attractive, in that universe as in this one (or any possible universe beyond.)
One might object, no doubt: what about the mooted acceleration of the cosmic expansion? Another example of an arithmetical implication of current theories - no empirical observation whatever, just as in the case of dark matter, would be my response.
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Post by fascinating on Mar 20, 2015 10:47:39 GMT 1
You are saying that the Universe does, in reality, have dimensions, (space-time)? Yes. And probably others, of course, if string theory is along the right lines. Yes. The basic axioms of arithmetic and by extension set theory are I think understood now, since the 30s - they are so basic I would suggest that they apply to any possible world, not just the one that exists - hence their apparently purely ideal character. Geometry is different - there you generate entirely different universes according to your starting axioms. And I answered you. It is an affine manifold - giving the feature at least of the dimensions of space-time - that has a certain geometry that is able by its nature to generate energetic forms. Including us. We are able to understand that real world, at various levels of approximation, because of the fundamental nature of logic discussed above. We are yet to fully understand the nature of the geometry of that universe as a whole - when we do, if we do, all our various physical theories will be seen to be partial representations, largely arithmetical approximations that would be "true" if that geometry had been very slightly different. Those arithmetical results will remain, though no doubt made even more precisely predictive, but our conceptual understanding of them will be radically different. Many hypothesised empirical representations of those mathematical formulations will disappear entirely, seen as mere artifacts symbolically standing in for our lack of understanding of that real geometry - dark matter, for example, is my guess (implied at present by the arithmetical results of measurements using our current theories), or, probably the most fundamental concept in quantum theory and particle physics, the property of "spin". Thanks for the reply (not all of which I understand). You had earlier written "You can call maths a language if you want, but it's one that can be defined entirely self-referentially - there is no need for any "things" outside of it to define it ostensively. ". I thought that you were implying that mathematics had no connection with the real world. But you have now said "The basic axioms of arithmetic ..... apply to any possible world, not just the one that exists". So I'm happy!
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Post by mrsonde on Mar 21, 2015 11:28:18 GMT 1
What don't you understand?
It can be and is applied to the world.
Yeah, why so happy? I very much doubt you'd be quite so happy if you knew what those axioms are! In any case, the general point is that the universe has not been constructed according to those axioms, as an architect might follow a blueprint or the taxman calculate your tax code. This is what this generation of theoretical physicists seem to believe - many of them state such nonsense as some sort of "discovery", at any rate. (There's even a respectable and growing group of cosmologists who say the universe and everything in it (that we can observe) is so obviously mathematical in nature that it must be a computer code, written by a programmer in the future - or, rather, in the real universe, the one we can't see but must exist outside the computer we're all stuck in and being generated by.) The same goes for geometry, incidentally, in my opinion - this field only seems less "pure" or ideal than arithmetic or logic because we're comparatively at a much earlier stage of understanding it.
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Post by nickrr on Mar 22, 2015 18:25:31 GMT 1
No - Nick has simply stated the basics of inflationary theory. To be fair I should probably have used the term "inflationary field" rather than gravitational repulsion because no-one knows exactly what this repulsive force is.
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Post by Progenitor A on Mar 23, 2015 8:19:03 GMT 1
No - Nick has simply stated the basics of inflationary theory. To be fair I should probably have used the term "inflationary field" rather than gravitational repulsion because no-one knows exactly what this repulsive force is. Hmm... 'inflationary field' eh? A not-very-elegant-way of getting out of the conundrum of 'repulsive gravity' and what happened to all that excess energy when the gravitational field reversed to an attractive force
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Post by nickrr on Mar 23, 2015 8:41:35 GMT 1
Not sure what point you are trying to make but I was just pointing out that you didn't seem to understand one of the most basic points of inflationary theory.
That you don't understand what we are talking about.
Inflationary theory is still probably the best candidate to explain such things as the flatness and smoothness of the universe, various aspects of the cosmic background radiation among others. Of course it's not considered proven and not everyone agrees with it but your bland assertion that no-one agrees with it is nonsense - unless of course you can provide some evidence but as usual this is sadly lacking in any of your comments.
The two halves of this statement appear contradict one another. Are you trying to say that because QM is probabilistic it can't give predictions agreeing with the real world? If you are it's a nonsensical statement. And of course any predictions come with a margin of error - all scientific results should do, that's how science works.
My opinion is the same as Feynman's, "I think I can safely say that nobody understands quantum mechanics", which is exactly what I've been saying. All we have is the maths. The irony is that this appears to be exactly what you are saying in the second part of this quote - again you have managed to contradict yourself. And you then compound the confusion by saying that I'm denying exactly what I'm proposing.
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Post by Progenitor A on Mar 23, 2015 10:05:52 GMT 1
Not sure what point you are trying to make but I was just pointing out that you didn't seem to understand one of the most basic points of inflationary theory. Nor, do I suggest, does anyone else! That you don't understand what we are talking about. Your arrogance is misplaced Inflationary theory is still probably the best candidate to explain such things as the flatness and smoothness of the universe, various aspects of the cosmic background radiation among others. Whilst containing many inponderables which cannot be expalined Of course it's not considered proven Of course not and not everyone agrees with it Of course but your bland assertion that no-one agrees with it is nonsense The truth of this assertion is that you agree with it! - unless of course you can provide some evidence but as usual this is sadly lacking in any of your comments. Impossible of course!
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Post by mrsonde on Mar 23, 2015 18:01:13 GMT 1
I'll join in with this entetaining debate at a later date - I suspect from the density of my typos that I've been cerebrating a little too much this afternoon. See ? That should be celebrating. I shll return to it.
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Post by mrsonde on Mar 27, 2015 2:12:57 GMT 1
No - Nick has simply stated the basics of inflationary theory. To be fair I should probably have used the term "inflationary field" rather than gravitational repulsion because no-one knows exactly what this repulsive force is. No one knows what it is full stop - no "exactly" about it. It's purely a "what if".
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Post by mrsonde on Mar 27, 2015 2:55:32 GMT 1
The point I am trying to make is simply to contradict your apparent claim that it is an implication of a theoretical explanation called "inflation" that gravity becomes repulsive rather than attractive. It is not. It is, as I've pointed out, merely a "what if" hypothesis. That is, in fact, the whole crux of the theory.
Unlike you, I suppose? You're the one that's been arguing that force and energy are equivalent, aren't you? That one is the reverse face of the other, and that together they always balance each other out? What sense are we to make of your claim that gravitation is "negative energy" now?
I don't particularly disagree with the conclusion that there must have been a rapid phase of expansion at a very early stage of the universe, if one accepts the various preceding stages of the Big Bang theory. That seems to be a necessary implication of these theories. What I'm disagreeing with is that there is any implication that this expansion was caused by repulsive gravitation. That is obviously the desperate resort of someone who can't think of any rational explanation - let's pretend everything we know about the universe was completely different at that point so things work out. What I also disagree with - because I do know what I'm talking about (as far as Guth has been able to manage to explain himself, at least) - is that this hypothesis is at all derived from any features of evidenced theory. It's entirely ad hoc, generating the evidence.
You're using "Inflationary theory" to refer to two different things. As I've said, the idea that there was such an expansion seems to be necessary, if one accepts the preceding hypothetical conditions. With the hypothesis that such a rapid inflation occurred, with a slight assymetry of course (another ad hoc hypothesis), then you'd get the features you mention - though as with any other observation, you'd get those with a wide range of alternative theories, of course. How you determine which of these alternatives is "the best candidate" is anyone's guess. Clearly you're not employing the usual desiderata of Occam's Razor, because you seem to have resorted to the entirely ad hoc hypothesis that at this stage of the universe gravity woked in the opposite manner than it works thereafter, without any explanation or even attempt at one.
No, it's not. Not even Guth agrees with his original theory. As I said, it's moved on.
I'm the only one in this whole thread who has provided a single shred of evidence. You merely make outrageous claims to omniscience, and when challenged to support your arrogance find some offhand comment in a popular science book, or a glib video on YouTube by a Star Trek fantasist. I'm still waiting for you to provide a single link to a reputable scientific site making use of any corroborated physical theory that uses a quantity of "negative energy". You can't do that, I know, so let's see a link to any explication that gives the slightest theoretical support to your contention that there is theoretical grounds for supposing that gravitation must reverse at this inflationary period. There aren't any. Are there? It's an invention - no evidential support, and no theoretical background.
No. The real world is actual.
Yes.
No, it's not. It's the basic problem of quantum mechanics. There is absolutely no theoretical explanation of how you arrive at the actuality of a "collapsed wave function". None whatsoever. Would you like a long list of quotes from a long list of the leading theoreticicans in quantum theory making exactly that point?
No, it's not. That's your belief of how science work. You believe it is primarily mathematical.
Again, that's your belief - your opinion. Examined dispassionately, in detail, it's complete nonsense. "We only have the maths" means nothing. Literally, nothing.
On the contrary - you've been saying that you understand it, and anyone who disagrees with you does not.
This is utter drivel. As I say, I very much doubt that even you know what on earth you mean by this. You;re saying that quantum theory - and further, from what you've said previously, all other physical theories, all our knowledge about the "real world" - is nothing more than, say, a times table?
We observe the world, sir. It has regularities. It has dimesional stability, so we can measure it, and work out proportional ratios amongst those measurements. That's the maths in physics. Then we work out theories attempting to explain those regularities and those ratios - not by inventing new maths, but by hypothesising unobserved structures that would give rise to them, and seeing whether the implications of those structures pertain should they be real and effective.
I contradict myself nowhere. You merely don't understand. Feynman is not saying that no one understands the maths!!!
God knows what that means - you require no help in compounding your own confusion, believe me.
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Post by fascinating on Mar 28, 2015 9:21:57 GMT 1
It is understandable that, when discussing quite deep scientific/philosophical questions like this, the people can misunderstand what the other is saying, and with misunderstandings, a discussion can become increasingly heated (but not more lit) and begin to turn into a slanging match.
I see a need to lay aside insults, like mrsonde calling nickrr's statment "gibberish" or nickrr saying that mrsonde does not know what he is talking about. Take each statement and, without emotion, analyse it and say why you think it is wrong.
Consider this statement by Nickrr and mrsonde's reply
I can see that "we only have the maths" probably means that we can only see what is really happening - or let's say make useful calculations of what might actually happen in the quantum realm - using maths, and only maths will tell us. Maybe nickrr can agree that we have some interraction with the "real" world and we make observations of it. Nobody came to be aware of the quantum mechanical world simply by sitting in a university library and making mathematical calculations.
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Post by mrsonde on Mar 29, 2015 13:41:08 GMT 1
If a statement is gibberish it's no insult to say so. If someone doesn't know what he's talking about it isn't an insult to point it out either.
Yes, of course - but that should be an and and not an instead. Nickrr may well be in need of your de haut en bas lecture, but I can do without such pomposity, thanks. Give me insults any day.
Quite true.
That's not what the statement says, and it's not what Nickrr and the mathematical physicists like him mean by the assertion. If that's all it meant it's an utterly trivial truism - read back through the thread if you don't understand the philosophical viewpoint nickrr is expressing here.
If he does, the assertion that "we only have the maths" is nonsensical, is it not?
Unfortunately, that isn't true, which is where the viewpoint nickrr's propagating derives from. It originated in quantum mechanics, but has become even more the case in cosmology.
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