joigus

No, I'm sure I made a mistake there. RuBisco is about Calvin-Benson cycle, right? Producing sugars. 😅 Thanks for catching me. OK. Thank you. I'm dabbling on chemistry/biochemistry, so some of the details went over my head, but I think I got the gist of it. Were those oxygenation events really that sudden? The banded iron formation suggests some kind of periodicity in that massive oxidation of the oceanic iron. Could a picture that you just sketched be compatible with some kind of periodicity? The closest I know from my past study of differential equations is the periodicity in populations that appears in models of competing species, like the Volterra model, which is about a predator-prey dynamics. Does a pattern like that make any sense at all in biochemistry of the oceans? I address this mainly to @CharonY and @exchemist, but feel free to answer other members, of course. Calvin-Benson always reminds me of underwear 😆

Very interesting thread and comments... RuBisco is the single most abundant protein on the biosphere. I would be surprised that it didn't have to do with major oxygenation events in the past. But the origins of this oxygenation event may be buried in complexity.

😆 I would seriously would like this conversation to get back on its tracks. I don't know what relevance monoidal categories would have in the conversation. Or functors and categories, or metrics of algorithmic complexity (those I think came up in previous but related thread and were brought from out of the blue by offended member.) Mentioned offended member then shifts to using terms as "efficient" or "surprising," apparently implying some unspecified technical sense. Summoning highfalutin concepts by name without explanation and dismissing everything else everyone is saying on the grounds that... well, that they don't live up to your expectations in expertise, I don't think is the most useful strategy. I think entropy can be defined at many different levels depending on the level of description that one is trying to achieve. In that sense, I think it would be useful to talk about control parameters, which I think say it all about what level of description one is trying to achieve. Every system (whether a computer, a gas, or a coding machine) would have a set of states that we can control, and a set of microstates, that have been programmed either by us or by Nature, that we can't see, control, etc. It's in that sense that the concept of entropy, be it Shannon's or Clausius/Boltzmann, etc. is relevant. It's my intuition that in the case of a computer, the control parameters are the bits that can be read out, while the entropic degrees of freedom correspond to the bits that are being used by the program, but cannot be read out --thereby the entropy. But I'm not sure about this and I would like to know of other views on how to interpret this. The fact that Shannon entropy may decrease doesn't really bother me because, as I said before, a system that's not the whole universe can have its entropy decrease without any physical laws being violated.

My code seems to have worked. True colours in full view.

Samuel Butler Yes. As many have said or implied before, the egg is the arrangement of genetic material to be tested against the environment. The chicken is but the sequence of later developmental stages of that egg, set against different kinds of environments: pre-natal, peri-natal, young, reproductive, post-reproductive. There's no chicken that didn't come from an egg. There are thousand upon thousands of eggs that never make it to become a chicken.

What's with the quotation marks? You seem to imply that no word in a code like Swedish would be surprising. What word in Swedish am I thinking about now?

I thought the last one was a Namib elephant, but I don't think it is. It's probably a big tusker from Tsavo, in Kenya. https://www.theguardian.com/environment/gallery/2019/mar/20/the-last-of-africas-big-tusker-elephants-in-pictures Thanks for the pictures. That's exactly what it looks like. Thank you.

As to scale symmetries in general, studying the invariance properties of a certain theory under re-scalings can be a useful tool, but I wouldn't try to read too much into it physically*. The reason is that, while symmetries as rotations and translations have a very transparent, very direct interpretation, that's not the case for scale transformations. Rotations can be easily viewed from the active point of view. I can rotate a piece of experimental equipment; I can rotate the whole laboratory (active transformations). I can think of extrapolating this operation to include the whole universe. In that purely theoretical, ideal, scenario, actually rotating the whole universe would be mathematically equivalent to the inverse passive transformation (simple re-labelling of coordinates) of my frame of reference. Same goes for translations. You can't do the same with scalings. IMO, you would have to be very careful to explain how these observers could tell that their scales change from point to point or region to region (continuously as you move from one to the other?). I think @studiot has made this point before, and what I'm doing basically is rephrasing, or ellaborating a little bit on what he said: That's what I meant by 'slippery slope.' *By 'physically' I mean considering different observers that 'see' different scales. How do they know?

Maybe he's somebody else's brother and she's somebody else's sister. But I think they're cousins. https://en.wikipedia.org/wiki/John_C._Baez#Family Anyway, he explains there why length and mass can't scale independently from each other.

The quote is due to Baez.

Google: Search string: "half life of uranium 238" Google: Search string: "how abundant is uranium on earth" Google: Search string: "most abundant radioactive materials on earth" Wikipedia: https://en.wikipedia.org/wiki/Uranium Iso­tope Abun­dance Half-life (t1/2) Decay mode Pro­duct 232U syn 68.9 y SF – α 228Th 233U trace 1.592×105 y SF – α 229Th 234U 0.005% 2.455×105 y SF – α 230Th 235U 0.720% 7.04×108 y SF – α 231Th 236U trace 2.342×107 y SF – α 232Th 238U 99.274% 4.468×109 y α 234Th SF – β−β− 238Pu Radiation is dangerous, but how dangerous it is depends on how exposed you are to it, as well as the radiactive material. Radioactive materials are present in many rocks, as eg. granite, but not so concentrated that they will give you cancer in any noticeable time.

Purpose is indistinguishable from the illusion of purpose.

Right. The emphasis was meant on the 'big.' There was a time when we were new too, remember? It's been knocking at our door for so many decades that it still sounds new. You could say it's the future of physics, it's always been, and it always will be.

I'll take a closer look at it later, but let me tell you physics is not just about making sense. Lord Kelvin's theory of electromagnetic knots made perfect sense, yet it's not what Nature is like. I have some comments to make about this idea of observer-dependent scaling. It's akin to a slippery-slope kind of argument, but for good reasons. Maybe tomorrow.

Ah, I missed this, @MigL. I'm sorry. Let me get back to you later. It's based on some musings by Leonard Susskind. During his lectures on supersymmetry, he laments that SUSY probably is telling us something very deep, but we still don't know what it is. I'm quoting him almost literally. Essentially it rests on the (mathematical) fact that the SUSY generators, that exchange boson for fermion, can be arranged in a way that produces space-time translations. Now that could be just a mathematical mirage, but it seems very profound. Another one is that, when you put superspace variables (anticommuting complex coordinates) together with space-time, the Lagrangians of relativistic quantum field theory appear as if by (mathematical) magic. That's what I mean by "really compelling." Now, I think you know me enough to know that I don't easily fall for 'big' new ideas that have to do with forcing the mathematics. I'm convinced that the way to go is to look at the mathematical form that we know to be right, while trying to interpret it in a way that opens the way to an extrapolation. I'm not sure I'm explaining myself very well. Maybe tomorrow. (Famous last words.)

https://math.ucr.edu/home/baez/lengths.html You don't contemplate quantum mechanics, that's why you don't understand. The world is quantum. \( \frac{\hbar}{mc} \) is a length. It's the length scale from which you must start making quantum relativistic corrections. You can't leave quantum mechanics out of the story. Otherwise your story is not about the real world. It's about a fantasy world. Solids are subject to quantum mechanics too.

Mass scales as inverse length. By together, I didn't mean the same way.

(My emphasis.) Who gave it? And are you a co-author? x-posted with Swansont. In any case, mass and length scale together due to relativity and quantum mechanics, so no, you can't pull this off. Unless you explain very good reasons why \( \hbar \) and c (speed of light) are irrelevant in physics.

I think they're insurmountable. If the universe were made of just photons and neutrinos on a scale-invariant background, it would display scale invariance, but it isn't, so it doesn't. MigL has given a nice cosmological account that complements Markus'. I think the argument, when you consider the quantum theory, becomes even more involved, as you would have to prove that the beta function --the function that tells you how the interaction scales with energy, and thereby with length-- vanishes. I don't know how massless physicists would feel in a universe like that, but it's been known for a while that it doesn't work. I don't understand how the equivalence principle allows you to pull this off. If anything, the EP tells you that free-falling local observers cannot tell they're falling, so the standard model would be still there, in all its locally-valid glory, telling you the universe is not scale-invariant... I also hope you don't mean special-relativity length contraction & time dilation. That's nothing like scale invariance...

Emmy Noether's case is particularly poignant for me, because of the ratio (treatment she got)/(genius)x(human qualities). Plus the theorem that bears her name is my favourite of all mathematical physics. She seems to have been an extremely nice person too. But yes, there are many. Many who had it worse than Noether too. Absolutely. Standard bearers. Jane Goodal in particular is one of my heroes. I was in two minds about posting this. Most women prefer day-to-day action, rather than this kind of gestures. But then I thought, what the hell. I couldn't not do it.

Thanks for your interest. Your numbers 1, 2, and 6 are in my heart too. Another one is American biologist Barbara McClintock, discoverer of transposable genes.

LOL.

She must have been a great teacher! Edit: I'll never forget Mercedes Serra, she taught me maths and physics. I wonder what became of her.

Cometh the comedian, cometh the comedown. And cometh the comet, cometh the final homecoming. You still haven't told me your favourite woman in science, DR.

"Fighting" encompasses so many things... You forgot to tell me your favourite woman in science, @dimreepr.