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Another piece of the puzzle of life. Seems to present very primitive form of cell differentiation, with only two types of cells. A billion year old fossil, which provides a new link in the evolution of animals, has been discovered in Torridon, Scotland. https://phys.org/news/2021-04-billion-year-old-fossil-reveals-link-evolution.html The organism was spherical in shape, suggesting also that cellular differentiation, "tissue" formation, and body plan were very primitive. https://www.cell.com/current-biology/fulltext/S0960-9822(21)00424-3

A number of interesting facts/data came to mind when I saw this question. [1] Scientific theories are models we use based on known data...[2] The dual nature of light/photons...[3] the fact that light/photons have no rest mass...a photon is a quanta of light or a bundle of the smallest amount of energy we can measure. Considering all that data, I came to the average sensible lay person's conclusion that a photon would have no shape. But like any good sensible lay person, I did some checking...https://physicsworld.com/a/how-to-shape-photons-using-a-trapped-atom/#:~:text=A photon is a quantum,photon's temporal shape or mode. "A photon is a quantum of light that can be described as a packet of waves that travel through space. A photon’s wavefunction is spread out over time and the specific nature of that distribution is the photon’s temporal shape or mode". :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: then this.....https://cosmosmagazine.com/physics/what-shape-is-a-photon/ What shape are photons? Holography sheds light: Hologram of a single photon reconstructed from raw measurements (left) and theoretically predicted (right). Credit: FUW :::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: https://www.mat.univie.ac.at/~neum/physfaq/topics/shape.html The shape of photons and electrons: extract: "A free photon can have the shape of an arbitrary solution of Maxwell's equation in vacuum. But only very special solutions are controllable and hence useful for experiments or applications. Upon production in a laser, photons are more or less localized (not precisely, this is impossible, as photons cannot have an exact position, due to the lack of a unique position operator with commuting coordinates); often only in the transversal direction of the beam - then you don't know where it is in the beam, except probabilistically. For photons on demand (that you can program to transmit information) you need to know when and where you transmit the photon, so it must be well-localized. Of course, a slit or a half-silvered mirror delocalizes a photon, and only a measurement (or decoherence along the way) relocalizes it. This enables interference effects. In these cases, the photon stops being particle-like and behaves just like an arbitrary excitation of the e/m field, i.e., like a wave. The particle picture of light is good only in the approximation where geometric optics is applicable. This has been known for almost 200 years now. The paradoxes and the alleged queerness of quantum theory both have their origin in misguided attempts to insist on a particle picture where it cannot be justified" ::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: Hope that helps............

From those lectures on quantum mechanics that I looked at on YouTube, it follows that the photon has no shape or trajectory. A photon has only two points, where it was born and where it was absorbed. Thus, the photon is a "black box", as it is arranged from the inside, we do not know.

Well spotted. (+1) I note that Martin Brasier is credited as a co-author. Brasier played a significant role in the identification and analysis of Pre-Cambrian micro-fossils and their evolution. He died in a car accident six or seven years ago. The organism's Linnaein name, Bicellum brasieri, presumably commemorates him and his role in this work. His popular book Darwin's Lost World, is an excellent read. I love such work that puts another (unnecessary) nail in the coffin of those Creationists who fail to understand what occurred in the previous billion years to enable the Camrbian Explosion.

My limited, chemist's understanding of QM is that you can't really speak of an "objective" EM field configuration for a single photon. If you could, it seems to me it would be a classical object rather than a QM one. But I think we probably now need a real physicist's input.

I tend to agree with @Prometheus. I find it difficult to see the paradox because there are so many unknowns. Let me give you an example: In recent years it's been discovered that there are microorganisms living underground and in the marine bottoms with life cycles completely disparate from those imposed by the Sun. This suggests that we are barely starting to understand the limits of life in our own planet. I would add the ethological argument. Namely: Why would another civilisation want to be seen by us? Predation, parasitism, territoriality, and other similar patterns in which one organism takes advantage of another are very common in Nature. Not always or necessarily to the advantage of one, the other, or both. Then there is the issue itself of how Fermi conceived of the question. It was a very informal argument arising from a conversation, that he later tried to make into a scientific argument, but I don't think he ever made it very rigorous or attempted to do so. Then came Drake and his equation. That's a more serious attempt at setting up the question. But still, so many unknowns... And going back to the original argument from Fermi, it sounds suspiciously similar to an argument from silence: We don't see any evidence of this, thereby it never happened. The way in which this kind of argument can mislead you has been extensively analysed in classical studies, archaeology, and all sciences that have to do with studying the past.

I, too, suspect that it's iron stains. The stains sometimes appear at the spot where I pour the salt into the pools. The salt I use is highly refined pool salt - ultra-fine pure white crystalline salt. However I don't think they remove all the contaminants, too costly. Here's what Fishel Pools says about pool salt: I think you're right about the chelation, here's what I found at PubMed: Amazing stuff, hey?

Those stains look like iron salts to me. You'll have to explain to me why you associate them with salt, as I'm a Brit and we don't have many outdoor swimming pools here. Do you use salt to treat the water in some way? Could it have iron as a contaminant, like the rock salt we put on the road in winter, which always looks a bit pink or brown? Chemically, I would expect ascorbic acid to form a "chelate" with iron Fe³⁺ ions, which is a sort of cage molecule enclosing it. This could serve to dissolve the iron salts off the sides of the pool, if that it what it is.

I don't understand why it's considered a paradox. If you take something like the Drake equation, there are lots of parameters we have little idea about, such as fraction of planets suitable for life on which life actually appears or fraction of intelligent life that develops detectable technology. It's quite possible that these parameters are such that a technological civilisation on average only appears, say, 0.7 times in the entire life a galaxy.

First amendment of the US constitution: Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances. So the "right of Freedom of speech" pertains to the limits the US government has in this manner. It does not matter if the term "freedom of speech" already existed or who first coined it.

This does not follow. The population of slaves can outnumber the population of the elites without outnumbering the population of non-slaves (i.e. white people, predominantly). It depends on what fraction of the population of non-slaves is considered elite. It's not as if every single family owned slaves, and, of course, not everyone is an elite.