joigus

OK. Let's take it piecewise: In your model, what is gravitationally coupled to what?

So how do you know both concepts, nothing and something really make sense, as mutually exclusive categories? Perhaps nothing and something, assuming they make sense, are interpenetrating, or implicating each other in some kind of circularity: There is nothingness in every somethingness (absence of a concrete substance that we can pin down as 'the thing in itself' --Kant-- in every observation we make). And also, maybe, there is somethingness in every nothingness (some non-removable features even after you remove every observable aspect). Can you guarantee that that 'nothing' and that 'something' are amenable to the application of such a thing as a 'boundary', so one is 'here', and the other is 'there'? Or maybe that boundary refers to logic, and not space? The concept of boundary seems to imply space.

As Swansont said: Gravitons move at speed c (they have no rest frame). Gravitons have spin 2. Gravitons are massless, so they cant have any characteristic length (radius of rotation). I see other problems (not completely unrelated): \( i \) seems to be an inverse length squared. But no 'internal' parameter describing a graviton can have length dimensions. Gravitons are not sources of gravitation, but the 'messenger particles' that carry it. Gravitons must have 'wave function' (field amplitudes) if we want them to obey quantum mechanics. Seems like you're trying to formulate an alternative physics, rather than modelling the known one.

Consequences for eyesight: Now serious. I'm sure there are some benefits in not doing something (anything) for a while, and giving it a rest, even if it's a regular body function. Eg: fasting for some reasonable time, I'm sure, has some benefits and somehow replicates better the kind of scenario we evolved in. If you're having sex several times a day, or masturbating, or just being sexually aroused without relief, it may be detrimental for obvious reasons. None of these activities are good for you if you practice them excessively. It just makes sense. As Phi said:

In the decades after Einstein's 'magic year' of 1905, physicists came to understand* that trying to set apart energy, \[ E=\frac{mc^{2}}{\sqrt{1-v^{2}/c^{2}}} \] and 'dynamic mass', \[ \textrm{inertia}=\frac{m}{\sqrt{1-v^{2}/c^{2}}} \] was quite futile, as they are proportional to each other with a universal constant as proportionality factor. Today, we no longer call mass this velocity-dependent quantity. We just call it kinetic energy. That's what it is. As to 'rest mass', it's just 'rest energy'. You can think of it as some kind of potential energy. If the body can't be broken apart by any process (decay, high-energy collisions), it still has this residual energy. As an example, if a body of rest energy mc2 (or \(m \), if you will; it's just a matter of units) decays into pieces of respective rest energies m1 and m2 , we know the liberated energy is (removing the unnecessary index 0 for 'rest', as mass is always rest energy), \[ \triangle E=\triangle mc^{2}=mc^{2}-m_{1}c^{2}-m_{2}c^{2} \] This is energy that we can understand as previously contributing to the internal cohesion of the particle that has just decayed, and no longer is contributing to forming the masses m1 and m2 , but contributing to the kinetic energy of the decay products, now moving with speeds v1 and v2 . Spacetime Physics; Edwin F.. Taylor, John Archibald Wheeler

Not sure that having wet biology is the key, @StringJunky, although it may be a factor. To me, and I'm speaking from intuition alone, the key would be having algorithms cooperate with other algorithms, and compete against still other, and produce offspring algorithms whose success is measured against relatively slowly-changing environmental conditions (as compared to the reproduction rate of such algorithms, so that anything like 'adaptation' even starts to make sense). IOW, a dynamics of competition and self-replication that mimics that of living organisms, and dispose of those organisms that don't fit the bill, so as to guarantee they don't have offspring algorithms. Given that we know for a fact that evolution of cognitive organs came about in the context of evolution of sufficiently autonomous structures in such a way at least once, it's a reasonable guess that something similar would likely happen again. Introduce cooperative self-replication (AKA sex), and evolution would speed up considerably. It is arguable that algorithms already have "awareness": Being able to probe the environment and store information about it however ephemeral, is some kind of primitive 'conscious' process. Self-awareness is just one step ahead: Being able to recognize clusters of data as other instances of algorithm and infer, by some kind of division self/other that the invisible 'self' variables (invisible because they're sacrificed to represent the universe outside) must be. Is awareness, consciousness, you name it, some kind of universal principle that operates in general; but in a very diffuse and ineffectual way mostly everywhere, while only in the way we experience it when a certain division inside (self) outside (universe) is established as a relevant "state variable" of the system, and cognitive connections as well in the internal states of these specially sophisticated physical systems? We don't know. I digress. The upshot (my guess) is: Let algorithms compete and cooperate among them, and have sex, and be anything like successful/unsuccessful, and there will be (some kind of) self-awareness at some point. In fewer words: Let there be Darwinian algorithms and there will be self-awareness.

IMO, brilliant explanation, Studiot.

The roots of science as we know it, I think, are already present in Roger Bacon and Galileo. It's this emphasis on observation and careful measurement that really did it. I see some kind of fruitful meandering from the empirical side (Francis Bacon) to the mathematical/rational part (Descartes). Advances have come in successive emphasis on one and the other. Aristotle (empirical emphasis) got his physics badly wrong. Much later, Descartes (pure reason, mathematics) got his biology of sorts badly wrong. I think this tension echoes through the centuries even today (cosmology; multiverse, pre-big-bang scenarios). "Greater" as more efficient, more influential at the grassroots level, more present in people's minds if only to the effect of disagreeing with it, or setting in motion waves of counter-opinion, or even just wondering what it means or implies, I think science is more influential than philosophy. I can hardly think of anything like the denial campaigns on global warming and the possible human influence on it would have happened had it been a question on purely philosophical epistemology.

Thanks for the mention. I'm in the middle of reading the thread so far. I'm no expert on Islam; rather, a person very interested on the history of Islam, and still largely learning about it. After the Rashidun Caliphate (632-661) and the Umayyad Caliphate of Damascus (661-750), which are characterized by waves of conversion, civil wars, internal dissent on interpretation of the Q'uran, etc., comes the Abbasid Caliphate (750–1258) (1261–1517). This first period of the Abbasids is the one that we traditionally associate to the flourishing of, not only science, but also religious studies, poetry, astronomy, and what not; mainly in Baghdad. The scholars' capital, so to speak. The date 1258 corresponds to the fall of Baghdad under the Mongols, which caused the destruction of vast amounts of scholarly treasures. Baghdad, and the Islamic world, never recovered from this blow. But people (scholars from the three monotheistic traditions) survived, and for a while formed a thriving community in Toledo during 12th-13th centuries, even previous to the final blooming of modern science as we know it mainly in Italy. They were kind of intellectual refugees. Then it was Italy who took the torch, and finally many ideas from (not just) the Greeks, but also India (eg, the concept of zero) and Babylon (eg, hexadecimal system), and very importantly, the Arabic numerals, which really gave rise to the scientific side of the Renaissance. The most relevant Muslim countries that have undertaken any kind of attempt at a scientific comeback are of course, Turkey (under Mustafa Kemal Atatürk) and Pakistan (under Liaquat Ali Khan). These are the highlights on Islam and science as I know them at this stage. I've filled in some details from Wikipedia, of course. BTW, this is a very nice thread, @studiot.

Very elegant explanation, as well as @Janus'.

Yeah, it must have been about that time. But the theory put me to sleep almost immediately. Fields are entities that vary in space/time. Is space an entity that varies in space? The metric is a field, matter and radiation are fields, etc. They are because they sit in space time. But 'space-time sits in space-time' doesn't make a lot of sense. I wanted to upvote MigL's last comment, but the voting function is not working for me.

You mean the odderon is the Higgs? I'm assuming God particle = Higgs. Higgs and odderon have different spins. Odderon is an odd number of gluons (spin 1); Higgs is spin 0. How do you get zero from an odd (algebraic) sum of ones? For some reason, I can't sleep. Normally I would be sleeping peacefully now.

🤣 It's a beaut, Moon. Didn't even notice the music. Although second time round I did turn it off, to just concentrate on the fish.

Agreed. It doesn't have to be a sophisticated equation. The old quantum theory, eg, was a set of ideas with a crude mathematical formulation relating particle attributes like energy and momentum to wave-like properties like frequency and wavelength. Then came the Schrödinger equation, which is of course a more powerful version of these ideas. In physics and chemistry, at least, you can't even start to build anything without at least a crude mathematical statement.

Nice video explaining the whole thing:

I just use \[ (and the closing square brace) for centred (display) equations and \( (and its closing round brace) for inline maths. It seems to interact well with the MathJax "engine".

You mean, \[\int (f(x)+ dy/2)dx= \int f(x)dx+ \frac{1}{2}\int dydx\] \[ \frac{1}{2}\int dydx \] Yes you're right it looks like that, but it's not a double integral, as \( dy\left( x \right) = y'\left( x \right) dx \). But the whole point is OP mistakenly thought the second-order differential made a difference in the evaluation of the integral, while it doesn't.

\[\int (f(x)+ dy/2)dx= \int f(x)dx+ \frac{1}{2}\int dydx\] \[ \frac{1}{2}\int dydx \] Inline: \( dy\left( x \right) = y'\left( x \right) dx \).

Negative mass poses other problems: I'm not 100 % sure that you can't still play with these things in a speculative way by carefully distinguishing: 1) Active gravitational mass (as source of the gravitational field) 2) Passive gravitational mass (as reacting to a gravitational field) 3) Inertia And complicating the picture of how they interplay by introducing assumptions that extend the Bondi-Bonnor model. But negative mass is a completely different matter. Keep in mind that the Einstein relation between energy and momentum leaves you with, \[ E^{2} = \pm \sqrt{\boldsymbol{p}^2 + m^2 c^4 } \] Time orientation is on the plus minus determination of the square root, not on the sign of the mass.

Neutrinos hardly interact at all. As MigL said, how are they supposed to interact with macroscopic skyrmions? What's the mechanism? How do you focalise a beam of electron neutrinos so as to guarantee that they keep at a distance of a fraction of a nanometer from a lattice? Why should they invert their mass? And if they do, tachyonic quantum fields do not travel faster than light, and they do not have negative mass, but imaginary: https://en.wikipedia.org/wiki/Tachyonic_field (My emphasis.) I will also quote a sentence that I once heard Lenny Susskind: "Only crackpots think tachyons go faster than light"

Clarification: I meant that as per Holmes' claims; I did not mean that you were actually to blame. Sorry for being ambiguous. My distinct impression is that you always, at the very least, make constant efforts to support what you say on documents or arguments. Also, I tried to remind Holmes how their comments on L. Krauss are nothing short of a slur: "Krauss of all people?" "his shenanigans", and I quoted. Holmes is a bit enigmatic to me. I don't know where they're going. They've played a wildcard, and then dropped it, and then taken it again with a different value... I would like to know why. I'm kinda curious how one who's tasted the elixir of science can part ways with it and embrace the word that stands for anything. mess-posted with @iNow

Inspired by one of @beecee's previous posts: Here's a very interesting piece of interview in which Sagan explains my "semantic" point very eloquently, I think: I'll let Sagan do the talking and take a break from the conversation. Another thing. You've filed some ad-hominem-attack complaints here --If I'm not mistaken @iNow was to blame. iNow takes no prisoners, granted, but let's be fair...

I recommend you Susskind's Theoretical Minimum (Quantum Mechanics). You should have no problem following the main ideas and equations. Then his lectures on QFT to get an idea of what this renormalisation business is all about. I picture you as the ideal person for his approach: with a sound knowledge of physics but having fallen somewhat out of touch. The other lectures I provided are just to get a flavour of what the problems are. They're difficult for me too. I think the right way to tackle theoretical physics lectures is: I know I won't digest 100 % of this material. Let's see if I can understand the key ideas. And keep going. Things start clicking after a while. You probably know very well from your experience studying GR years ago. You can always forget about the equations for a while and concentrate on the words.

I think the question can be approached on a number of levels. For starters, quantum mechanics makes time a very special parameter. You need a distinguished time that goes hand in hand with a so-called Hamiltonian of the system (the energy operator). This Hamiltonian is also the mathematical operation that embodies time translation for the system. GR, on the contrary, has no special time. There is no preferred coordinate system in GR. If you have no special time, you have no special Hamiltonian, which means you have no special time-updating law for the state. So right from the start, the symmetries of GR don't bode well with the special needs of QM. This difficulty though, can be overcome AFAIK. One formalism that does it is the so-called Ashtekar variables, that allow you to include all the constraints of GR into a significant set of variables that are amenable to quantization. And they give you a Hamiltonian. But a lot of preliminary work is needed to get there. In any case, as @studiot suggests, the conceptual bases are quite different. Then there is the question of the perturbative structure of the theory, as @MigL pointed out. The theory is non-linear, has more field variables, and the loop calculations become intractable pretty soon. This, in and of itself, would not be catastrophic, as Yang-Mills fields (in the non-Abelian case, which is strong nuclear force) are also self-interacting and have a richer field-variable structure. But YM fields are far better-behaved than gravitation at short-distance (large-momenta) scales. The theory is free at short distances (large momenta), while gravity is just the opposite. Gravity, also, has no polarity and is thermodynamically exceptional. This bad large-momentum behaviour connects with what today is considered the ultimate reason why gravity is so unwieldy to a quantum treatment: the dimensions of the gravitational coupling constant. It is dimensionful (and badly so), as opposed to the dimensionless character of QED, QCD, and EW coupling constants. Renormalization crudely consists in decreeing a maximum momentum Λ for every scale that we wish to study, and then prove that the observables inferred from the quantum scattering amplitudes can be expanded as a sum of two parts, one that remains under control (finite), plus a logarithmically divergent one (scale independent). Now, you cannot do that with gravity. There are two technical ways to characterize this in words: 1) Gravity doesn't look like a scale-independent quantum field theory at large momenta 2) The large-energy spectrum of gravity is black-hole dominated Equivalence of both is discussed at: https://arxiv.org/pdf/0709.3555.pdf It's quite technical, in spite of the title, but enough words can be found there so that a crude idea of what goes on can be obtained. There is a last-ditch attempt in QFT to make quantum gravity renormalizable, and that's called asymptotic safety, initiated by Steven Weinberg, and it's based on hoping for a point in the phase space where this bad behaviour is saved by a so-called fixed point of the beta function (a function that monitors the renormalization behaviour when you shift the cutoff). But it takes a lot of guesswork and I don't know what the state of the art is at this point. Then comes supersymmetry. It's a big hope, because supersymmetry leads to much cancellation of infinities. New technologies have been developed in recent years, like calculations using the formalism of maximally-helicity-violating scattering amplitudes. It's a technology that involves massless gauge bosons, always leads to finite calculations, but is considerably more abstract, because it uses expansions of the amplitudes that cannot be understood as local quantities (at a point), and it involves twistors, which entails expanding space-time points into pairs of massless spin-1/2 wavefunctions (Weyl spinors). Two interesting lectures on the subject. The 1st one is more technical, but again, enough worded arguments are given so that one can get an idea of what goes on. Quantum gravity and its discontents (by Stanley Deser, 2010): Quantizing gravity and why it is difficult (Leonard Susskind, 2013):