joigus

Look up the words "chirality in Nature" and you'll find more wonderful examples of this. Chirality is the property of being distinguishable from your mirror image. https://en.wikipedia.org/wiki/Chirality I don't know whether it's related, but for most proteins, only one chiral version is present in Nature, at least in this part of the galaxy. The left-handed version is here, but the right-handed version is not, or is biologically irrelevant.

As Swansont is trying to tell you, the sphere is only for calculational purposes. There's no spherical symmetry. You place a sphere like that any place you want in the universe and calculate acceleration as due to the effect of gravitational attraction from all mass contained in that sphere. Resulting acceleration (which is an overall property of the whole universe) can be positive, negative, or zero, depending on relation between mass density and acceleration parameter, similar to escape velocity possible situations. Susskind makes that very clear in those lectures, as far as I can remember. It may be a bit puzzling that you can get the result from a calculation that involves an imaginary sphere, but that's the magic of Newton's theorem. It's not a sphere that's causing that acceleration. Or, perhaps, if you like a sphere of infinite radius of which any other sphere is at its centre.

I also think it's impressive, perhaps tantalising. But no paradigm seems to have been overturned. It seems that the most important surprise factor comes from the good state of preservation, rather than it beeing completely unexpected. I wouldn't be surprised either if new discoveries converge to a picture in which some of what we think to be 'modern features' actually arose much farther back, which seems to be the direction this finding is going.

Yeah. Most of those failure points will be relevant during deployment. And a big part has to do with operating the Sun shield. The telescope must work at 6K on average, and it seems that the most difficult part was to guarantee that this gravitating laboratory cools down to the required level. It's a matter of months. We've got some more waiting to do.

LOL. I meant, it's a ho, ho, ho.

Weather is OK. It's a go. https://www.bbc.com/news/science-environment-59782057 Live:

Here it is: What's appealing about this line of thinking is that it proposes to combine well-known principles of physics in unexpected ways, rather than guess unexpected principles of physics in well-known ways. The first technique has always met much more success than the second.

At smaller scales dark matter doesn't really play that much of a role. It's when you get to the region of galactic haloes when it starts to kick in. That's why you don't consider it when solving problems like, eg., the perihelion of Mercury. It's very sparse and apparently nucleates around the galaxies, but at very long distances in comparison with atomic matter. As there are no collisions, it doesn't fall anywhere near the galactic centres in any significant amount. Einstein's equations OTOH seem to me to be formulated as some kind of compromise --a brilliant and predictive one to be sure. The Einstein tensor does not saturate all the possible geometric degrees of freedom. The other degrees of freedom are coded in the Weyl tensor. They can also be generalised in several ways, like including torsion, complexifying them... They seem so inviting for generalisation. Although this is nothing but a hunch. It also has to be said that the attempts have been many, and nobody so far seems to have been able to extend Einstein's predictions significantly. As to primordial BHs, it's very appealing. But how big can they grow before there would be noticeable effects? I don't think you mean dark matter haloes are made up of SMBHs. We would have seen them already by their lensing effects. Plus the masses would be so out there. I'm probably just expressing my preferences. We really need the data James Webb will provide.

I trust any third-rate archaeologist of the 21st century a thousandfold more than an army of thirty thousand Maimonides. Maimonides hadn't the faintest idea what carbon dating was about, or what the Hebrew pastoral and agricultural people of the Bronze Age had to deal with on a daily basis --because he didn't dig the ground in search of refuse food, or ancient manuscripts, or even excrements.--, or what the layers of destruction of ancient cities looked like. A city like Meggido was destroyed thousands of years before Maimonides was born, and yet, archaeologists of the 21st century have seen, sifted through, and analysed to the minutest details every inch of terrain in that city and many others like it, and consequently are much more intimate with what those people thought, their dreams, their hopes, their fantasies, than Maimonides would have even dreamt of.

How do we know this?

OK. I changed my mind: 1) Really a signal that Einstein's equations must be modified at long distances 2) Exotic particles coming from super-symmetric extensions of the standard model of elementary particles 3) Swarms of little black holes (that for some reason do not evaporate)

Don't we all do? Sorry for getting sidetracked from main topic, apophenia.

Beautiful. Man with watch always knows the time, man with two watches is never sure, man with Bach feels time's substance.

Honestly? I can't remember the last time I said to myself, 'I pulled it off'. One exception. My boss asked me months ago: Why do you come biking to work? --She didn't like it. I said, 'it's part of my lifestyle'. And she never bothered me again about it.

I had missed important aspects of this note. I'm sorry. I'm also sorry that most of my comments here went either unnoticed or misunderstood. As I'm sure you know, there is an ages-old technique called maieutics, used by Socrates, part of which consists in --precisely-- following the argument of the proponent to the ultimate conclusions, so as to prove that there's a fatal flaw --or many, or insurmountable, as the case may be. Presenting opposition sometimes presents you also with the problem of the opponent adopting an aggressive stance that doesn't allow you to deploy any further arguments; while entering their logical framework allows you, in a manner of speaking, to set up a logical time bomb that I've found through the years to be far more effective than engaging in simple gainsay exercises.

Thanks, Phi. I'd actually read that, but I had forgotten. I'm getting old, you know.

Thanks for reminding me. I've changed my mind at least a couple of times about what a plausible explanation might be. @MigL, if it's not too much trouble, could you lead me to that thread? The one @beecee linked to --though very interesting and certainly related-- is not the one you're referring to, I think.

We do know what it is not: Not hot, not atomic, not electrically charged. There are some other nots. Some candidates to explain what it is are: 1) Swarms of little black holes 2) Exotic particles coming from super-symmetric extensions of the standard model of elementary particles 3) Really a signal that Einstein's equations must be modified at long distances (ordered according to my personal preferences)

Thanks. I'm a sucker for everything Steven Pinker. I've recommended to take a look at his views at least once on these forums. Very nice books he has on language and cognition, etc. Also many interesting talks on Youtube. First time I read or heard about prior probability fallacy was a long time ago --and it wasn't Pinker who explained it, I don't remember now who it was--. It blew my mind. It was the feeling of how vulnerable we all would be if something like that were to happen to us. I think --and always thought ever since-- that it should be explained to children at as early an age as possible. I wish there was a way to create a permalink to these questions. I know some common fallacies are mentioned somewhere on the forums.

Relished it! This is my contribution to your subtopic: And the original: Goosebumps, honest. Bach reigns supreme. Enough said.

Final preparations for James Webb telescope: https://blogs.nasa.gov/webb/2021/12/18/nasas-webb-space-telescope-launch-confirmed-for-dec-24/?utm_source=FBPAGE&utm_medium=NASA's+James+Webb+Space+Telescope&utm_campaign=NASASocial&linkId=144816059&fbclid=IwAR1B123ZizvSW9293DGEWK3OACEfQfmuH5CUoqnOFji34qmP0k6HHqLzxbI We may be entering a new era of astrophysics and cosmology. Fingers crossed. After LIGO's enormous success, this looks very promising. Primordial BHs are my favourite explanation of DM.

This has reminded me of, (My emphasis.) Interesting approach, the 'cognitive' one. Angel = hidden mechanism that people (especially in ancient times) indulged in very often --anthropomorphisation of just about everything they didn't understand. I value this approach. I wish I understood it better. I rather lean towards the archaeological/historical perspective,* which is the direction in which I've tried --unsuccessfully, I have to say-- to bring the discussion. To me, the closest we can get to understanding how or why these old timers came up with this angel stuff, is by digging under the ground and then thinking rationally about what their possible motivations must have been. The fact that these intermediaries between people and the gods had wings --Sumer, Akkad, Babylon's cherubim-- does not surprise me at all. Birds appear as symbols of deities as far back as Gobekli Tepe --end of the last glacial period ca. 11000 years ago. In other early human settlements birds also appear depicted as taking the decapitated bodies of the dead. The bird appears strongly in Egypt too. It must have symbolised a connection between the living and the dead for obvious reasons. In the case of Gobekli Tepe, it's vultures we're talking about. Now, it doesn't take a long stretch of the imagination to conjecture a possible reason why people believed that vultures were sacred beings in charge of helping the transit of the deceased to the netherworld. One small step, I think, takes the average Bronze-Age sophisticated mind from different kinds of birds to different kinds of angels. * They're not mutually exclusive, of course.

Verily I say unto you that the platypus of the Lord you will face in the centuries to come, and it will have the appearance of a mixture betwixt a beaver --which, again, you're clueless about-- and a duck. That would've been pretty convincing.

So do platypuses, but the Bible seems to have been clueless about them.

OK. I don't really know. But I know better than to believe in angels. The best vantage point is that of asking questions. Like, Why do angels have two bird-like wings, like avians, and no mechanism to correct for direction (tail wings) which is essential to fly? Are their wings just ornament? The design that's presented in current mythology is a desaster, from an engineering POV. Perhaps they use a bat-like design with membranes that can bend more freely? Do they succumb to temptation? Or perhaps they did only before the beginning of history, and then things went perfect OK from then on? And thousand and thousands more questions that I won't entertain anymore, because there's only so much time I can spend on a monumentally stupid idea, like 'angels exist'. Bots do exist, OTOH.