Green Baron

It is not nonsense and by all means worth mentioning. It is try to deal with the shortcomings of the "pure" Theia impact hypothesis by extending it to a much more energetic impact. If it has something to it it'll be further discussed. Edit: generally marine invertebrates are good environmental indicators and index fossils, specifically sponges during earlier periods, corals especially in and since the Jurassic and other invertebrates like foraminifera, molluscs, bivalves, brachiopods.

True, but we think that earth was almost "ready" ~ 4.5 billion years before now, at the beginning of the Hadean

A hypothesis is a testable assumption about a phenomenon, based on observation. The giant impact hypothesis for the moon is founded on chemical analyses and orbital mechanics. It has been refined with observations of other moons, meteorites, our model of the forming of the solar system and its bodies, and undergoes modelling and simulations. It has its unresolved problems. That's why people are working on it and on possible alternatives. 3 of which have been ruled out, as one can take from the links. I will not bore you with reciting their contents ;-)

Oh, you've noticed :-) Many of them are adjustments or extensions of the giant impact hypothesis, as is the one in the OP. Good news: it is all in discussion. There is a lot of info on it in the links in this thread.

You get that impression if you only read the popular headlines. As soon as you look into it it becomes clear that it is the name for a hypothetical body from the giant impact hypothesis, nothing more and less. Edit: I used it only because it is common and i ddidn't want to cut&paste giant impact hypothesis over and again.

Yeah, don't let this get too wild. Ease of explanation is what drives research. If you start thinking around several corners to support an upcoming hypothesis (edit: while simpler explanations are there) something is wrong with your base model. The Theia hypothesis is around for several decades now and not widely doubted, though maybe in need of more adjustments. The paper in the OP also misses out on some things there. Here's some reasonable pop science: Very basic: https://starchild.gsfc.nasa.gov/docs/StarChild/questions/question38.html A variant: https://www.nasa.gov/topics/solarsystem/features/moon_formation.html The classic model: http://curious.astro.cornell.edu/our-solar-system/the-moon (skip down to questions in that link, @Cassel, they are answered there) Somewhat advanced, just to show that the ideas are in development, without any preferences from my side: http://advances.sciencemag.org/content/3/1/e1602365 Addressing the angular momentum problem with many impacts instead of a big one: https://www.nature.com/articles/ngeo2866 ... and so on. You see, nothing is carved in basalt or iron ;-) Edit: this is the second time in my life that i recommend a Wikipedia article. Changing times ...

Two impacts coinciding in that manner are improbable. In terms of parsimony the giant impact hypothesis is the "easier" variant. It is taken into account (and widely favoured) because orbital mechanics almost exclude a capturing. A planet clears its path, throwing smaller objects out or in or incorporates them, that's what makes it a planet. And the fact that earth and moon are so similar in their isotopic compositions suggest a common origin, there is little doubt. The moon started orbiting close to earth, slowly leaving since then in exchange for friction energy from tidal forces. Simulations suggest that the moon initially might have been very close to earth, like a couple of radii, though this has great uncertainties. I am not sure if capturing of the moon is in discussion any more. The web has a lot of information on the Theia impact hypothesis and its development, in publications, on the space agencie's sites, EGU and AGU publications and almost all of the geoscience journals. It will not be easy to replace it ;-)

Yo ! :-) Io (Moon)

It is not a theory, neither is the giant impact hypothesis (Theia). That is a problem i see too. And the cloud would loose much material at the edge. https://agupubs.onlinelibrary.wiley.com/doi/abs/10.1002/2017JE005333 I didn't watch the video but overflew the corresponding article. Theia is generally accepted but like any hypothesis not unquestioned. But it is the best explanation for the observations of the compositions of moon and earth, it was developed when we got samples from the moon during the Apollo programme. Earth was already differentiated at that point and the impact almost destroyed its mantel (one can find simulations), but left the core intact. The synestia proposal came up a year or two ago, being an extension to the Theia impact with a much bigger event that vapourized both bodies but was just not strong enough to fully disperse the resulting cloud. They say this explains better compositional differences, which exist but are few. It has in my opinion three problems: First the mentioned impulse that could keep the cloud from condensation. The impulse question is not addressed in the synestia hypothesis. Second is that Theia explains better the slow receding of the moon to higher orbits over geological times because it formed very close to earth and has since then wandered to its current orbit. I would need more modelling because i'd expect an impact that vapourizes a differentiated planet's core would also disperse the resulting cloud, leaving nothing "valuable" behind. Third is composition: The lighter material at the edge of the cloud would have a high probability of escape. I am unsure if the composition with volatiles and mantle material can be explained with subsequent impacts after such an event alone. tl,dr: Theia is not unquestioned, but the most accepted hypothesis for moon forming for now. Which does not mean that this is a frozen state of research :-) We'll see if this approach will be discussed any further in the future.

Hmm, i can imagine that he knows how to circumnavigate the block, but maybe he is a good guy, leaves it be, and watches in peace and quiet after school ;-) --------- There was no firing up of the Hopper this week, or have i missed it ?

well, in this case, sorry for the a, but Kiruna 8.000 ton ore trains hauled by 15.000hp electric locomitives between the mine in Kiruna and the port in Narvik. n.b.: i read that the recuperated brake energy when running down from the mine to the harbour is sufficient for the empty train to return.

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Lofoten Where Slartibartfast was in top form :-) Beautiful landscape, b.b.b.ut c.c.c.old.

Amateur radio has shot up cubesats. So maybe, for the eager, start with an amateur radio license ?

Ebro (river) Name giver for the Iberian peninsula. And has seen 1.2 million years of hominin pre- and history.

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"Eyewitness Account", by Stanislaw Lem. Anyone knows that humoristic take on different social models, set on a planet with two (originally 3) antagonizing powers ? The ones have transformed their natural surroundings into an extremely benign intelligent sphere the provides everyone with everything and keeps people from hurting themselves or others, the others have chosen a more rudimentary way of life, live inside the cadavers of giant lizards which they move with handles and so. Being sent to the back is sort of a punishment ... Needless to explain that both hemispheres are not friends. A third, now extinct form has tried the same as the first group, but two such spheres could not co-exist. And yes, that had a poltical background. If you stumble upon it, read it. Back under the shower :-) Edit: o, crap, it apparently has not been translated into English. Guys, this is rare but in this case you're missing something. Original Polish "Wizja lokalna", German "Lokaltermin". But it is not suitable for a casual or learning speaker. Lem was an intellectual person.

Well, there's an abstract. Which doesn't deliver much real world information. tbh, judging from a short overview there is nothing in there we do not already know. Only difference is that the information was reviewed with a strong "i see what i want to see" bias. Which makes the Journal of Astrobiology the right place for it :-) Was i too quick to judge ? I don't think so, for example the "stromatolites" thing, which is presented as if but actually has no proper publication and is only a rumour, derived from a blurry image, if i am not mistaken. To me they don't even remotely resemble earth-like stromatolites. But i know for sure and out of experience than one should never judge geological formations from afar. 1st semester geoscience ;-) The next rovers, Mars 2020 and ExoMars will tell us more ! Edit: a short search questions the ALH84001 argument as well: https://www.spiedigitallibrary.org/conference-proceedings-of-spie/3755/1/Morphological-behavior-of-inorganic-precipitation-systems/10.1117/12.375088.short?SSO=1 tl, dr: You see what you want to see and as long as there are other explanations the shape of an object alone is not an argument for extraterrestrial life. And may i add, not even for intrat. life as a review of some very old indirect traces of life has shortly revealed ;-)

Take your time for this one:

An a, let me see ... Andaman Islands ... where recently a "missionary" got a call he could not miss. A call to meet his deity :-)

I guess it'll be a long monotonous noise, if one wouldn't apply any modulation. One could pack the 4 different "notes" in groups, apply some sot of modulation, change speed, ... then it would be a shorter less monotonous noise. Who remembers analogue modems' handshake sounds ? Or cassettes ?

Totally depends on the culture and their perception of their deities/gods/spiritual concepts. The star could simply be a symbol for the god, or signal the deities wakeup/bedtime, or be a vehicle for him/her, or just a signal to do/leave something irl, whatever. Just because they were portrayed as representing something in the shape of something from the real world (a humanoid, an animal, a hybrid, a contraption like a cart or so) doesn't mean they were restricted to that behaviour. Some of them could fly, or travel between the real world and a spiritual level of any sort (typical for shamanism and derived beliefs), live under the sea (in an octopus' garden), play roles as messengers, show benign or malign behaviour of sorts, beat each other up, change shape and form, etc.

Yeah, justice is frequently tossed around. Ooops ... :-) Mesopotamian (Babylonian) astronomers tracked Jupiter i recall having read somewhere. I think it held the name of their respective deity-in-chief Maruk (?) Martok (?) no that's Star Trek :-) as well, just as it did in antique Greece (Zeus), from whom he was taken over by the Romans and rebranded Jupiter.

There apparently has been a hearty discussion among geneticists around the concept of "junk DNA" and its amount in the human genome, after the ENCODE project claimed that 80% of the human DNA is functional, either directly encoding proteins or controlling the expressions of other parts of the genome. The last word has not been spoken yet :-) Back to the case: if i understand it correctly, digital information is represented in the 4 bases, DNA synthesized and bottled. "Hey, don't spill my backup !"

Well, the Romans obviously named Jupiter Jupiter and the name was traded through the Middle Ages. But it has different Names in different cultures. In modern times it was chosen to name planets after Roman deities, so Jupiter just kept its designation. One could as well have chosen Arabic names, as in high Middle Ages their astronomy was more advanced. But now it is as it is, and i too think that by coincidence the boss of the Roman pantheon became the boss of planets :-)