MigL

Maybe White Holes are composed of SuperSymmetric Particles. Oh wait ... They're predicted by the models, but don't exist either.

We have members who are dyslexic. We just like to hear your thoughts and opinions, not those generated by a 'group-think' server. Look into the Wheeler- DeWitt Equation, and ask as many questions as you like. I'm sure the discussion will gain all of us a better understanding.

Of course BHs exist. But your statement was 'As white hole should act with positive radiation pressure, shouldn't black hole act with negative?' and since WHs don't exist, they don't act with positive radiation pressure, so BHs don't need to act with negative radiation pressure. Does that clarify my position ?

You have an idea; but it is an old one, and there is no need for AI. See here Wheeler–DeWitt equation - Wikipedia

Or, we can still believe in CPT symmetries, BUT, White Holes simply do not exist.

No. We won't call you at all.

Why ask us; ask your Priest or spiritual leader. Either you're weird, or have some other issue, which means you shouldn't be using social media to get a diagnosis, but a licensed professional.

If Russia used nukes in a war of aggression, they would lose the support of China, India, and the 'crazy' states. I would say, even now, some of his military commanders must be questioning Putin's choices, but are afraid of pushing back for fear of getting pushed out of windows. Once it becomes clear that Putin intends to sacrifice everyone if he can't get what he wants, they, and the population, will push back, and take him out. Remember B Yeltsin standing on top of a tank holding a Russian flag, and the Armed Forces backing down ? Not all Russians are crazy.

Just because the model we have imagined and used says something can happen, does not mean reality has to comply. White Holes would be a lot easier to find than Black Holes, in fact, they would be among the easiest things to spot possible. Wer have detected thousands of BHs, some in galaxies 10 Billion years distant/ago, and we have actual photos of closer ones. NO White Holes have ever been detected. So basing your premise on how White Holes should act is a non-starter.

Primordial means they were formed in the hot, dense state shortly after the Big Bang event, not prior to it. Quantum fluctuations in the pre-inflationary universe would have led to regions of extremely high energy density, which would have gravitationally collapsed to BHs after inflation. The usual calculation involves upscaling from a quantum fluctuation with the inflation factor, and it predicts PBHs of fairly small size, prone to 'evaporation' by Hawking Radiation, and which may have evaporated by now. Hoever, the possibility exists that as these PBHs formed during the hot dense plasma stage, they grew very large through accretion, and formed the 'seeds' that became eventual galaxies. It is possible that some of the later formers, gobbled up their surrounding plasma too quickly, and were left 'bare', with no material to form galaxies around them, as the plasma, or eventual matter, had become much less dense. These would obviously be much larger than stellar BHs, and would probably only be found away from galaxy clusters ( voids maybe ? ), and through Gravitational lensing. Now, if you were to compress the ( observable ? ) universe back together, as suggested by "Big Bounce', everything would eventually be forced into a universal merged Black Hole, and we know of no mechanism which would allow for the 'bounce back' other than evaporation ( into where ? ), so I don't know how anything can 'survive' the collapse. I don't think Penrose's Cyclic Cosmology allows for full collapse into BH state

The AGM-114L is carried by helicopters ( L is for Longbow Apache ). and, due to its active mm-wave radar guidance, it can be used as a 'fire-and-forget' ordinance against other slow-moving aerial vehicles. But obviously, not jets.

What is 'real' ? Something that affects you in some way ? That you can see, smell, hear, touch, or detect with various equipment ? Because that star that went supernova a thousand years ago could not affect you in any way whatsoever a thousand years ago. But the image, which travels at the speed of light, along with any gravitational anomalies whose information travels at the speed of light, and any radiation, like neutrinos, which travel a little slower than the speed of light, are the effects that make it 'real'. By your definition, the Sun could be going nova as I type, yet it has no effect on me and I cannot detect it in any way for 8.5 min., so how is it 'real' ? Yet in 8.5 min. it will absolutely be real.

Thanks @studiot . looking forward to it.

Yeah. I think the 'anti-time' discussion ran its course awhile ago. But the tangential discussions have proved interesting.

Have a great time in Sicily; the cactus fruit, or 'prickly pears', are great.

Hellfire missiles don't bounce. Here is the detonation sequence for a Hellfire missile... "A Hellfire missile is launched, guided by laser or radar to its target, and upon impact, an M820 fuze activates the warhead's detonating mechanism. The fuze requires electrical power and significant forward acceleration (greater than 10 Gs) to arm itself. Once armed, it initiates the detonation sequence for the warhead, which can be a HEAT (High Explosive Anti-Tank) charge designed to penetrate armor or a thermobaric charge that disperses and rapidly burns. " And who, in their right mind, would fire a Hellfire missile at an unidentified object. Air forces, and armies, of all Hellfire operators have strict rules of engagement, requiring positive identification of targets. Could this have been simply testing of the guidance system of an unarmed Hellfire missile ?

Maybe I should add this to the 'Today I Learned' thread ...

I thought that was Syracuse in Sicily ( Southern Italy ). Maybe Ken can do another 'deep dive' and find out why ice levels seem to be disappearing at a faster rate in the Northern hemisphere as compared to the Southern. The slope of the ice loss graph seems much steeper for Greenland than Antartica; is the greater land mass just a larger heat sink or are other factors at play ?

Yeah. As TheVat mentions, in spherically symmetric systems, spherical polar co-ordinates can vastly simplify solutions. One example would be the solution of the Schrodinger equation for the Hydrogen atom. It is a partial differential equation in (radius, theta, phi) where we can use separation of variables, as the spherical symmetry allows the 'removal' of the angular co-ordinates (theta, phi) leaving a differential equation in one variable (radius), that even I can solve. I'm sure it could be done by someone ( else ) in cartesian co-ordinates, but it would be extremely messy.

I would think that the concept of a 'metric space' is more fundamental. "A set with the notion of distance between its elements." from Wiki. The corresponding metric, is then, the mathematical tool to measure those distances. And the example most people are familiar with is 3D Euclidian space with its usual distance between points. But another example would be on a sphere with angular distance. And not necessarily on a manifold, it could be the 'relation' between members of a set that aids transforms between them. My apologies if the terms I use aren't up to Studiot's standards, but this isn't my area of expertise.

Thanks guys.

V Putin doesn't care about ruining land, even his own. Look at what the former USSR did to Chernobyl, the draining of the Aral Sea, attempted nuclear extraction of their 'oil sands' equivalent, ground-based nuclear tests, and much more. He doesn't care about the people; he'll be in Moscow or St Petersburg. If the US does nothing about it, which is likely considering the President, I doubt Europe will do anything about it either. France possesses almost 300 strategic M51 submarine-launched nukes for deterrence but has as few as 20 TN81 tactical nukes. The UK gave up their air launched tactical nukes about 30 years ago and only have strategic Trident Submarine deterrence. I don't think either of them will launch hi-yield strategic ballistic missiles at Moscow/St Petersburg. Apparently the UK has ordered an additional 12 F-35As, with the capability of carrying tactical nuclear missiles or bombs and IIRC France was to build a model of the Rafale specifically for the carriage of tactical nukes ( although, not being 'stealth', I don't know how far it would get into heavily defended Russian airspace ) so maybe they will be both re-introducing tactical battlefield nukes.

Maybe if you'd looked up my reference on space-time diagrams Spacetime - Wikipedia Spacetime diagram - Wikipedia You would have realized that a light cone is a space-time diagram rotated about the time axis. And that any horizontal line, or plane as you describe, is space-like, and involves faster than light information transfer or motion: you know that's impossible, right ? ( actually, true horizontal implies instantaneous transfer or motion ) Until you exorcise these non-sensical preconceptions you have, by doing some basic research, or asking questions, you will be always pitching assertions that don't make sense. No matter how long you make your posts !

Do you realize that nothing Mars does can ever affect you before 22 minutes have passed ??? It could blow up, it could vanish, or even become a Black Hole; the fact is, it is not happening 'now', it is happening 22 minutes from 'now', as that is the only time it will have any effect on you that you can detect. Before the 22 minutes, you have no idea what, if any, changes have occurred and it might as well be in another space and time, for all you know. What were you told about 'common sense' and relativistic effects ? And what relativistic 'observations' have you made that are explained by your conclusions ? Anyone or any detection equipment in the same frame would not notice anything. If you and I are in space and a satellite passes by us, would you notice differently if I said I couldn't tell who is actually moving, us or the satellite ? No consideration involved; you are a peer. But we expect a little better from someone who's been active on this forum for over a dozen years, and has taken 'Physics at a University level". So why not learn about frames of reference, in what circumstances relativistic effects become noticeable ( and NOT common sense ), and the proper use of space-time diagrams ( light cones ), so you can make sensible contributions to the conversation ?

No wonder you're so confused about the science. You post one thing, and someone gives you advice on the proper reasoning and references, which you then ignore, and post another absurd claim regarding a different subject. Your scatter-brained postings are confusing to everyone else also. I think you need a hobby other than science.