joigus

Another philosopher venturing into the deepest scientific caves without the lantern of maths...

Mass really is rest energy. That's all it is. You have to think of mass as some kind of cohesion energy. Mass is the energy that a piece of matter still has even if you take it to a standstill. (To understand this you need Einstein's theory of special relativity). A world with no mass is conceivable. It would look the same at every length scale. A world with no energy is nearly unconceivable, OTOH. I agree with @Mordred that those are not necessarily bad questions. They're good --if hard-- questions. Mixing --that Mordred mentioned-- further complicates things: Particles with well defined mass don't have other quantum numbers that well defined. They are quantum superpositions of states with different quantum numbers (analogues of electric charge). Some particles are so-and-so percent of this particle and so-and-so percent of that other particle. And this "mixing angles" (that determine how much of this and how much of that there is) are fixed that way since the beginning[?] of the universe... It's very confusing. My advice would be: Don't think about mixing for the time being. In QFT, mass is a mess. In Newton's mechanics, it's simple because it's a primitive concept and doesn't have to be justified. (Sorry I wrote "sofisticated" instead of "sophisticated". I'm bilingual, and I get the spelling of Latin/Greek-root words wrong when I'm writing in a hurry.)

Why? A world made of photons would gravitate. It's energy that's the source of gravitation, not mass. All fields are quantum fields. They should be. It's just that people haven't been able to make sense of quantum gravitational fields so far.

No problem. You must think of quantum fields as things of which it makes sense to think of them as "being there" but in a vacant state. The field people usually refer to is the vacuum of the Higgs field. One has to spend considerable amount of energy (and money) to take it to an excited state with occupation number = 1.

It's not either/or. Quarks cannot exist as individual massive particles, and protons aren't the smallest hadrons (strong interactive particles). Mesons are short-lived but real enough, and are composites of quark-antiquark. And they are smaller than protons. The so-called Higgs multiplet is actually a quantum field with 4 degrees of freedom. 3 of them are called Goldstone bosons and they're the ones that massless particles swallow up in order to acquire mass. The left over degree of freedom is what we call the Higgs boson. So trying to picture what happens in terms of an actual "swarm of Higgs particles" flying around is the wrong way to picture it. This leftover DOF of the Higgs multiplet is normally unoccupied. Occupation number = 0, in the QFT parlance. So it's not really there. You have to actually provide a lot of energy to make it show up. The swallowed up DOFs are what's dragging the massless particles to make them look as they've got mass. I don't know whether that answers your question, if only to clarify that the actual picture is a bit more sofisticated than particles modifying other particle's trajectories. Did that help at all? It's all energy that's the source of gravity, not only mass, and certainly not just the Higgs field.

Vagueness cannot be proven false, but that is no virtue. Try to contradict this: "There is something about something that could explain something in some cases." It's falsifiable ideas that get the ball rolling. There are other things: Explanatory power, prediction, economy of ideas, etc.

Niels Bohr said it. But he didn't say QM is absurd. To say that QM is extremeley counter-intuitive is one thing. Quite a very different thing is to say that it is absurd. No physicist would say such a silly thing. The quote is frequently phrased as, After a few weeks you're over it, as you should if you want to do physics and complete the exercises. An uneasiness can stay with you for a while, but then you finally accept it. Why wouldn't you? It's the way things behave. Conservation of energy is a local conservation principle, within the allowance of Heisenberg's uncertainty principle, even in QM. So we know this not to be true. It is well known that QM introduces a tension between reality (the possibility that the output of an experiment can be predicted with certainty for certain groupings of observables) and locality (the fact that information, energy, angular momentum, and every other conserved quantity must propagate through space, and cannot disappear here and appear there, so to speak). If you want to introduce a model that proposes non-local propagation of the amplitudes, it would be strange, but I don't think it could be ruled out based of first principles. But you've done nothing of the kind. You haven't introduced any hypothesis. You just have a vague idea: Something non-local happens that somehow explains something in some cases. Not the most promising of starts.

This is not a conceptual problem for quantum mechanics. Then you just dissolve into vagueness: "it would be like", "a certain behavior", "would be like" three or four more times, "more or less energy" etc. Too vague to even make sense. And no, particles cannot exceed the speed of light, not even "in some cases." So-called virtual particles --if that's what you're refering to--, are not actual particles, they are modes of the quantum field that cannot be measured but must be included in the calculations.

It would be, not only presumptuous, but plain stupid for me to disagree with you. I'm keenly aware of this, yes. And I was for a while thinking about making due qualifications --retroviruses, that you mention, for which RNA goes to DNA, and prions, which I implied without mentioning them, and have to do more with folding or packaging of proteins of "chaperoning" as I understand. That's why I chose the prions as an (admittedly extreme) example of how the doings of the proteins more heavily determine what the brain ultimately looks like, does or doesn't do than the other way around. I introduced that example precisely because the OP was about the brain in particular. Francis Crick famously regretted having called this DNA-to-RNA-to-protein predominant flow of information a "dogma". Dogma is something accepted without question, while paradigm is just a typical example of a pattern. It is unfortunate that so many people use the word "paradigm" more pompously than it deserves, IMO. A paradigm is just a typical example of something. But you're totally right, of course. It's more complicated that that, with lots of feedback going on from the organ level to the molecular level, and back.

I was thinking the same thing: WTH are Calabi-Yau manifolds doing here? A picture is a picture is a picture...

You've had excellent responses already. You seem to be looking for a video though. Here's one just as a sample: Of course, as they've told you, it's not about the brain monitoring the process, but about regulatory sequences being activated/silenced, etc depending on the signaling going on. In order to understand all of this, you need to have a grasp of the paradigm of molecular biology: replication --> transcription --> translation from DNA to protein, which is almost always the case in bio. As an extreme case of the complete opposite happening (proteins acquired somewhere else determining the brain's behaviour), bad protein packaging can give you a brain going horribly wrong. Those are called spongiform encephalopathies.

Obviously. grav force/strong force is a dimensionless number, and represents a natural scale in Nature. Newtons OTOH are just some convenient units useful on the Earth for weighing bricks and such. My own favourite unit of force is the Jocular, and one Jocular is equal to 1020 N. Your coincidence has just vanished when expressed in Joculars. I concur with the other objections expressed, btw.

Good tip too. Thanks for the recommendations and welcome back.

Sorry you see it as though I wasn't trying to help. I was. I thought it was more urgent that you learn to handle dimensions than it was for you to handle vector addition. As an old professor of mine said, 'If you want to be able to write Chinese poetry, your first goal should be to be able to write Chinese'. I wish you best of luck with your Chinese poetry.

You said, This is not dimensionally consistent. All physical equalities must be dimensionally consistent. It can happen though that when a dimensional quantity is a universal constant, you can choose it to be one, and there is a dimensional reduction. AFAIK, the centimeter is not a universal constant.

How come you multiply force times distance to get a force? The result would have to be a work, energy, torque... (Never mind the mixed units, as you should convert cm to m.) This should be homework, right?

I sometimes wonder why people can't sense the imminent possibility that someone special is risking all their money on a Ponzi scheme. Nearly as life-threatening as bullets, when you think about it.

Sorry. I was editing and it came out by mistake. I'm working on a proper answer. Ok. Here's my answer. As @StringJunky said. You need enzymes, if you want to digest anything. If you have molecules that constitute cellular walls it makes a lot of sense that they be stable under a wide range of conditions. Eukaryotes use phospholipids as cellular walls, with the phosphoric group pointing out, and the fatty acid pointing in. I think there are good evolutionary reasons why no eukaryot would 'want' to evolve an enzyme that digests cellular membrane, as it is shared by all eukaryotes in the form of a double layer, like this: It would be like a suicide mechanism for all eukaryotes. Why do it? It's not because nature can't do it. Nature can, if it sets its non-mind to it. Think about N2. A sturdy molecule if there is one. Yet organisms have developed enzymes to break it. But why break down something that's the first chemical step to make you?

I don't think Gen Z people today can imagine what it was like. Daily life went on like none of that was happening though. Our parents and grandparents had seen much much worse.

Maybe. Or maybe just a tad less compelling. The Cold War was a crazy, crazy time. But I think that just substitutes the D in MAD for some sort of different acronym, like UD (unacceptable damage)?

I think nuclear power is a deterrent, not an actual tit-for-tat mechanism. This, I think, was well understood by the '60s by the likes of Robert McNamara and others. The MAD principle guarantees that. The actual tit-for-tat takes place on a whole different level once the MAD is guaranteed. It creates a fulcrum for other forces to operate, that's all. BTW, I also think "political scientist" is a contradiction in terms.

Very well explained here: https://en.wikipedia.org/wiki/Innumeracy_(book)

The more I think about superdeterminism, the more I think it's possible and, as Hanke said, untestable. Is it possible that back in a remote past of a preinflationary period lies the key to every happenstance in the universe? It's possible. It's a matter of plausibility perhaps. Occam's razor is sharp indeed. One should be, shouldn't one?

Aaah. I'm a stickler for precise terms. As if that was the problem with the present crossroads we're in. It's probably not. Revealed does have a religious sound to it though...

Ok. For the record, I think you're right that Genady's metric just describes flat spacetime, and that this argument that I'm giving is really clutching at straws. I was exposed to Schwarz's/Clairaut/Young theorem in the past and I remembered that if a function is not C2 (never mind the only non-continuous derivatives being the diagonal ones) the conditions of the theorem are no longer satisfied and it could happen that some devilish argument gives you a contradiction. I just don't know. Thereby my question "are you sure?" which I should have formulated more clearly. My intuition tells me that fxy and fyx could give you problems, but fxx and fxx is the same thing no matter what the continuity status is, because x is the same thing as x, as you rightly imply. Another part that makes me think that you're right even from the POV of a rigorous proof is that the distributions involved are Heaviside's, the delta, and its derivative. And those are extraordinarily well-behaved as long as you never integrate them against functions that don't fall to zero fast enough at infinity. All functions we use in physics fall to zero pretty fast, so no problem there. As to your question for me, if by "pathological" you mean "not continuous", it's not possible to have a composition of two functions, one continuous, and the other not, that gives you a continuous function. So my answer would be no. What does happen sometimes is that, trying to solve EFE, we get bad coordinate systems, and we must use singular coordinate transformations that mend the "singularities" that were never there in the first place. I do know that that's what happens with the Kruskal-Szekeres coordinates. After all, the composition of two singular transformations can restore continuity, exactly as 1/u (singular at u=0) with u=1/x (singular at x=0) becomes just x (continuous everywhere). It indeed is.