Yeah someone else pointed that out (or perhaps it was you in another comment):) This is quite a silly story in the first place - insider trading is serious, but the summary doesn't seem to have been checked particularly thoroughly and this being Slashdot I've not bothered reading the article.
That doesn't justify the 7-2=7 thing. (Let's assume time changes are implicit, being a thoroughbred European as I am I might be forgiven one or two lapses on US timezones.)
"it's still to early to write C++11 code for any real products"
What you seem to mean is it's too early to write C++11 code for any real products if your development team aren't up to speed with it. That's a totally fair statement, but it's clearly not true that it's too early to write C++11 for real products -- we do. We're liable to swap to C++14 as soon as commercial compliant compilers become fully stable and settled (and, of course, that we can convince our IT support to license them, which may take a year or two).
[Caveat: my personal experience with C++ was first with a Borland compiler probably not fully compliant with C++98, and then onto an MS compiler compliant with C++11, and a gap of 12 years. The language I came back to was significantly nicer - for my way of thinking - than the language I left. So I'm rather biased towards C++11 and even more so towards what I see coming up with C++1Y.]
The Federal Reserve announced a change in interest rates at a particular time - 2PM, Washington time. Trades were placed in Chicago 2ms after 2PM. It takes about 7ms for news to get from Washington to Chicago. As a result we can say two things:
1) Someone has been dabbling in insider trading, or has a loose mouth. Either way, if they become known, they're in deep shit. 2) Slashdot editors don't proof-read their submissions, given that the summary states it takes 7ms for a message to get to Chicago, that 2-3ms after 2PM trades took places on the Chicago exchanges, and 7-2=5ms, not the 7ms we were promised was stolen.
The alternative of course is time travel, which I'd much rather was true. A couple of years back we had a couple of crackpot papers on the arxiv that can be interpreted as saying that the Higgs boson was travelling back in time and sabotaging attempts to observe it. Perhaps this is evidence that the Higgs is getting more subtle.
You're more than welcome, thank you for appreciating them. (I did my Masters thesis on acoustic holes in Bose-Einstein condensates, and while I've forgotten most of the details myself I can still be a massive bore on the topic:) )
With acoustic holes probably the easiest scenario is to imagine a sheet of water running downhill, getting faster the whole time. It's important that there is no turbulence and virtually no friction so that the inside of the sheet is basically a "perfect fluid". (This is impossible in reality but it's a good image.) At some point down the slope the flow will go supersonic. Above that point you can fire sound waves back up the slope and they'll move -- slowly, because they're being swept down at the same time, but they'll still move up. Below that point, the flow is supersonic and so the sound wave is swept along with it. The point at which the sheet goes supersonic can be very loosely, hand-wavingly, seen as an "acoustic event horizon" -- no sound wave can escape from over it. When you model it properly, you find that it's a lot more concrete than that and that actually it *can* be described as an event horizon, and the sound waves are moving as if they're light waves in a Schwarzschild geometry, and the analogues go further. (They don't work for perturbations on the hole, though because the underlying physics here is pure Newtonian; nothing to do with gravity at all.) When you look at the situation in a quantum fluid you see that you do get Hawking radiation, too.
Lovely stuff:) Matt Visser is probably the clearest I've read on this topic but on the whole what he writes is for PhD level physicists - but if you can find a popular level article he's written it would be very well worthwhile. Ulf Leonhardt has written some articles on analogue holes (often in optical systems rather than acoustic, but the same broad principles apply) that are worth trying to track down, too.
Calling corn 'wheat' a default is a good way of putting it - it was what I was trying to get across in more words. "Corn" is ultimately related to "Kernel" and does certainly come from "seed", "grain". But the language evolved so that now it's a catch-all for grains, and wheat by default across most of Europe. Of course, I want the kids off my lawn and the language to stop evolving;)
Very true. For my own comfort I tended to stick within pure Fortran programs - I'm still more comfortable in Fortran than in C or C++ - but there were things that were better to do elsewhere, particularly where I had access to a library that I much preferred (say, in C, which happened quite a bit) to what I easily had available in Fortran. Sure, I could have gone hunting but it was a lot easier to build a trivial wrapper around the C library and just call that. I can't actually remember why I didn't like the Fortran interfaces for the GSL that were around but I ended up building wrappers around quite a bit of that at various times.
"That's an almost meaningless statement, unless you define what is "OO" (ten programmers will give you twelve different definitions for that)."
Very true. In this exact context I'm meaning an object containing functions that are contained within its namespace. There's almost certainly actually a way to do that in modern Fortran but I'm not aware of it, and instead I use modules as a rough analogue of a class and select the functions from them that I want to use in a particular method. (I can also get around quite a bit of the issue by overloading the function names in the interface, if it seems that important. Normally it doesn't, to be honest.)
"Eventually somebody will teach the computers to convert the Fortran to a readable and easily understandable modern language - while both keeping the behavior identical and highlighting likely bugs and opportunities for refactoring."
That language will likely be Fortran 2008 or 2015...
Not at all. It might be a bit more monocultured than, say, C++ but there are still more than enough ways to skin the same cat that you end up with a ton of cat parts and a mass of confusion.
A pedantic note - it hasn't been called "FORTRAN" since Fortran 90 was introduced. Otherwise it's nice to see people defending it for scientific applications:)
Oh now, that's a bit harsh. Programming in Fortran isn't something done because people are afraid of work. I genuinely get tired of the incessant Fortran-bashing by people who -- in my experience, at least -- have almost never, if ever, actually used the language or seen why other people do. In most cases they seem to be repeating jokes their lecturers made about the language, jokes that were first written back when FORTRAN 77, with those stupid capitals and all, was the dominant form.
Now, I'm very much not a fan of F77. In fact, I hate the language. It's clunky and decrepit and not suited for modern programming practices. But it's easy to call from later Fortran standards, and each one has vastly improved the situation. Fortran 2008 is a genuinely nice language. True, it's not OO - though you can force it to act almost as if it is - but not everything has to be forced into OO. What it is is extremely good for numerical work, and dealing with arrays in particular in Fortran is a dream after, say, C, or even C++11. The fact it calls F77 routines without effort or pain also helps, since there genuinely is a vast body of code still in F77. (The oldest I came across was F66, ported directly from Fortran IV. Now that really did need to be rebuilt in something approaching a sane language.)
I'm not saying F2008 is "better" than either C or C++11 -- that's a meaningless statement. But there are things that make it a very nice language to use, and other things -- character strings, I'm looking at you -- that make it distinctly unpleasant. Same as any other language, really.
I'd suggest you don't be so pious. I'm for protecting the language as much as anyone else but ultimately it evolves. I don't think this is really about the people employing numerical techniques in science becoming "more poorly educated"; I think it's about your field branching out and attracting new jargon and new uses for the old jargon. It's just what happens.
As it happens, I've spent close to ten years in academia where we build "codes" (typically in Fortran -- 90 or more recent if you were lucky; 77 if you weren't) to solve problems. I have since moved into professional development, chiefly in C++ and occasionally in C#. The use of the spoken language changes and the two fields have different ways to express the same concepts. Ultimately I don't really see a major problem with this.
All that said, misuse the word "corn" and I begin to get extremely irritated so I probably shouldn't be so pious myself...:)
[In British English "corn" doesn't mean maize, it means wheat, or occasionally barley -- more accurately, it means the chief arable crop of an area. When English speakers settled North America, that chief arable crop was maize, hence the American usage. What annoys me isn't Americans calling maize "corn" -- which is entirely valid in both North America and in their dialect of English -- but rather the *British* thinking that corn is maize. It isn't, it's wheat. I also wish they'd get off my God damned lawn.]
evidently you don't feel that bullet points are a useful bit of functionality. fair enough, but there are plenty of people who would disagree with you on that one...
Depends very much on your model of dark energy. I'll go a bit out on a limb and say that we don't have anything approaching a convincing model of dark energy right now, with the best we have being that a cosmological constant exists. We do understand the spacetime of a black hole embedded in a universe with a cosmological constant - it's known as Schwarzschild-de Sitter space - and while that doesn't say how a universe of black holes and a c.c. behaves it's pretty telling that nothing extraordinary happens. But it does rely on a couple of assumtions (well, many more than that, but two significant right now): firstly, that dark energy is a cosmological constant, and secondly that we can describe the interaction of black holes and dark energy through semi-classical analysis. That means that we can use a black hole solution from general relativity and (potentially) a quantum mechanical description of the cosmological constant: assuming the quantum nature of gravity has no effect. Possibly not true. Moreover, dark energy may not be a c.c., or not only a c.c., in which case frankly bets are off, including on how the dark energy would behave inside a black hole. (It's not even immediately obvious it would act as you'd expect a dark energy too. Interior solutions for black holes are very strange beasts.)
I think it really helps to remember that thermodynamics is an *emergent* theory: it's only valid when you're talking about vast numbers of particles. There is nothing, for instance, that stops a few electrons -- even in isolation -- grossly violating the second law of thermodynamics and settling into a state of vanishingly low entropy. Just that, when you look at larger systems they will never, as a system, move to a state of lower entropy.
Putting it another way, look at the gas bouncing around your room right now. That's roughly 75% nitrogen, so let's pretend it's all nitrogen to make life simpler. Go down to the level of a nitrogen molecule. You've got a roughly axially-symmetric molecule, shooting through the air, colliding with other axially-symmetric molecules (at arbitrary angles) and occasionally slamming into the wall. Modelling that single molecule would be excruciatingly tough. Doing it for the, let's say, 10^28 nitrogen molecules in your room right now would be punishing, and also extraordinarily uninformative.
However, we can instead of looking at a nitrogen molecule concoct descriptions of the entire ensemble of nitrogen molecules. When you find concrete ways of describing them as a whole, you're lead to define entropy reasonably early on, and then lead to define temperature and various energies and enthalpies and the rest of the paraphenalia. In short, you get out the entire structure of thermodynamics, *from a system that had nothing to do with it and never mentioned it*. That's emergence: a large collection of objects exhibits behaviour that is entirely unrelated to the underlying physics.
That being so, very small collections of, well, anything, cna violate thermodynamics however they like. On anything like macroscopic scales, no chance. (Well, virtually no chance.)
Along the same lines you might be interested to look at acoustic, or "dumb", black holes, which occur in any viscosity-free, irrotational (barotropic but ignore that one) fluid. The sound waves propagating through such a fluid -- which is totally Newtonian -- act as if they're photons travelling through Schwarzschild spacetime. In principle, we can build these things in Bose-Einstein condensates and, technically, it's already been done. Problem is that we can't measure Hawking radiation from them because at the minute they're way, way too weak. Anyway, point is that the physics governing these is Newtonian (or in the case of a BEC is a collective quantum statistical mechanical thing) but that the *collective* behaviour of the sound waves is that of photons travelling through curved spactime.
I'd say "ignorant" rather than "stupid", making clear that "ignorance" is not perjorative. No-one should ever be ashamed of admitting ignorance, and no-one should ever call themselves stupid for asking an honest question:) I probably can't answer your questions to anything like your satisfaction because I'm bouncing well against the limits of my own ignorance, but at least I might have a slightly clearer perception of things (and therefore make much larger mistakes...)
"If black holes form in the quantum foam wouldn't this phenomena be present within the first few milliseconds of inflation?"
Probably, yes. It would depend on the details of the theory - and indeed whether inflation would occur at all; while inflation is an accepted component of the standard cosmological model let's not forget that it relies on a scalar field (whether physical or effective) whcih has never been observed and is not really in itself realistic, including contrived models that employ the Higgs as an inflaton. But that aside, since it seems very likely that something similar to inflation had to have occurred, then yes, these effects were probably active very early on. Inflation probably diluted the early black holes to an extreme degree though; early motivations for inflation focused more on diluting magnetic monopoles and primordial black holes, along with solving the horizon and flatness problems, than modern motivations do. (If you're interested, the modern motivations are much more that you easily get a "scale-invariant" spectrum of ripples in the extremely early unvierse, which matches observation perfectly. Any alternative to inflation absolutely has to reproduce a nearly scale-invariant spectrum.)
"Would that allow for them to gain enough mass from the density of material surrounding them to not evaporate instantly through Hawking radiation?"
No idea. If inflation were rapid enough, probably not, but no-one could say for certain without a more complete model of quantum gravity.
"If that is possible could early black holes have come about not through supernova but through the quantum foam?"
That's certainly a possibility. Even without this (speculative) support through spacetime spongecake primordial black holes could be sufficiently abundant that they have been repeatedly studied. Any means of support would feed back into the problem and warrant its re-examination.
I would certainly agree that we should take a position of extreme scepticism towards Penrose's claims that quantum gravity gives rise to consciousness.
My contention is that Penrose is one of the greatest general relativists of the mid-late 20th century, and has only been overlooked because Stephen Hawking is in a wheelchair. What I'd judge as Hawking's greatest successes - and they were very great - were in collaboration with Penrose (in the singularity theorems), in collaboration with Ellis (covariant fluid dynamics) or were formulated in that period and aided by conversations with people like Penrose and Ellis (such as Hawking radiation). I would class the three of them as amongst the greatest physicists of the later 20th century, along with people like Kip Thorne, John Wheeler and Stephen Weinberg.
Unfortunately Penrose has also made a lot of strong claims he can't prove, and other speculations that he can argue and seem to make sense when he argues them in person, but which ultimately are very unconvincing. The quantum gravity leads to consciousness thing is certainly one of those.
Please don't hold it against him: the man is an extraordinary physicist.
Same as you shouldn't hold the papers he's put out with Gurzadyan in the last couple of years against him. Penrose has never claimed to be an observational cosmologist, nor a statistician. I believe, though I've never met him to ask in person, that he went along with Gurzadyan's papers because he thought that this was potential evidence for his pre-big bang model of cosmology. Unfortunately the circles on the sky that they identified are very, very definitely *not significant*, no matter how they try and argue it against people who are genuine experts in the field (and much more than I; I'm a weird cross-breed between theorist and observer, and therefore nothing like as good at theory as Penrose and nothing like as good at observation or stats as the people who so easily and convincingly dismissed his papers with Gurzadyan).
In the way you mean it, it doesn't. The event horizon is just that - anything inside of it doesn't interact with anything outside of it. It's simply where the name comes from. A 4-dimensional point in spacetime was dubbed an "event", so two regions of spacetime which can't see each other -- at any point in spacetime -- were said to be separated by an "event horizon". So a blackhole doesn't interact with anything, basically by its very nature.
However, it *does* cause a big curvature in spacetime. The main point is that it's no different from a star. Look at the physical situation: you have a star, which is a body supported by a balance between the pressures generated at the centre by fusion, against gravitational collapse. After some transitions from hydrogen burning up to, say, carbon burning (the end point is different for various stars but the ultimate limit is that stars don't burn iron; you lose more energy than you gain trying that, so it doesn't support a star) the fuel at the centre is exhausted and the star collapses. If it is heavy enough, it simply doesn't stop collapsing.
Now consider the spacetime geometry around it, and idealise a bit. Then before the star starts collapsing we have a massive spherical distribution of matter. Excellent. That's described by a Schrwazschild metric -- *any* non-rotating, chargeless, spherical distribution of matter is described by a Schwarzschild metric. (It's known as Brikhoff's Theorem.) But that will be true as the matter begins to fall across the Schwarzschild radius, assuming the physical conditions are such that it does so rather than bouncing (which depends on a vast number of parameters, including how massive it was in the first place, how fast the outer envelopes are falling when they hit the burnt-out remnants of the core - too fast and they may shatter the core which causes a bounce and ultimately a supernova... except even that may or may not leave behind a remnant white dwarf heavy enough to collapse first to a neutron star and then to a black hole - or it may tear the core apart completely, or end up in one of the intermediate states etc.). There's no reason to assume that the external geometry changes just because something suffers spherical collapse, right? That was true in Newtonian gravity and it turns out it's true in GR too -- the gravity outside a spherical object is the same as if all that object was concentrated at a point in the centre. So a collapsing spherical shell doesn't change the geometry. THe problem here is that the collapsing shell will pass through the event horizon. Nothing dramatic happens here -- a key tenet of GR is that we can always locally (for a given definition of "local" and that may be extremely local indeed) see things as if they're on flat spacetime. For astrophysical black holes that "local" is actually rather large. A coordinate system known in GR is the Painleve-Gullstrand system, which looks a bit odd but describes Schwarzschild space exactly (outside the horizon). Unlike "usual" coordinates, in Painleve-Gullstrand coordinates absolutely nothing untoward happens at the horizon: to something falling through it it looks like normal spacetime. The point of this tedious diversion is that nothign happens to the infalling spherical matter of the star when it passes through its own event horizon.
That then means that a black hole can form perfectly happily; no interaction with the outside universe is needed (and indeed doesn't mean much). If you were stupid or homicidal enough to chuck a colleague in, from your point of view he would mvoe slower and slower and get fainter and fainter as he approached the horizon, and you would never see him reach it.
From his point of view (if we ignore the spaghettification that would actually rip him to bits in most astrophysical holes) there would be nothign strange; he would rapidly cross a horizon he couldn't even identify, and then a microsecond or so later would inevitably slam into a future singularity that he could no more avoid than we can avoid moving into the next minute of our lives.
"how then can gravity escape, considering that the highs has measurable mass, in the gev range?"
The Higgs doesn't carry gravity. The Higgs field imparts mass to fundamental particles (and the Higgs boson is the particle associated with that field, though the particle itself does nothing for mass), but that is a very different thing. Quantum field theorists will describe gravity by *gravitons*, which are also bosons but where the Higgs has spin 0 -- identical from every angle -- the graviton has spin 2. The Higgs has a high mass, while the graviton is massless. Unfortunately this is itself a semi-classical picture, since these quantum field theorists have to specify a background spacetime to propagate a graviton along... utterly defeating the point if you're trying to look at this type of effect. (A massless particle would travel on the same paths as light - so a graviton in this language would evidently be trapped behind the event horizon.)
Instead when you're talking about regions of high spacetime curvature you should drop the language of gravitons and work straight with the geometry. I know a lot of quantum field theorists would mock me for that point, but I think they're as wrong as they think I am. Our best theory/theories of gravity are geometric in origin; the effects of gravity are not caused by a force but rather by curvature in the space we're traveling through. We try and go in straight lines, just those lines are curved. In this language you don't have any questions about gravity "escaping" from a black hole since there is nothing carrying gravity; it's just curvature in spacetime. A gravitational *wave* is a different thing - a ripple in spacetime - and while you'll hear people loosely talking of black holes emitting them, those waves emanate from outside the horizon. No wave will come from inside.
If we fired a Higgs into the black hole, it wouldn't come out again. However, that wouldn't do the mass of any fundamental particles in the area (things like the electron, and the quarks - protons and neutrons are not fundamental and most of their mass comes from binding energies rather than interactions with the Higgs field) because the field itself is still permeating the space outside the black hole.
Hopefully that's cleared at least one or two things up and not made it worse.
Well, certainly this is speculative physics but in this field that's not really something to attack - merely something to be aware of. We don't have a properly working quantum theory of gravity to understand what's actually going on down at this level, so this kind of paper is simply reasoning something that would happen were a particular set of assumptions valid.
Black holes on smaller scales would almost certainly exist, but it does depend on what you mean by "smaller", of course. I don't think anyone would argue that black holes down to the femtometre scale are entirely plausible. The problem on smaller scales comes basically because of the hierarchy problem: gravity is astoundingly weak compared to the other forces. In the context of the field theories that underpin the standard model of particle physics, that means that on scales at which those forces operate, gravity is probably (note "probably") adequately described by semi-classical calculations - quantum fields, but living on a classical background spacetime. It's only on smaller scales, loosely as one approaches the Planck scale, that the quantum effects of gravity would have to be taken into account.
Of course, even that might not be true, but it's the best guess we have at the minute and if we don't investigate ideas that come out of attempts to improve the situation we'll make absolutely no progress at all. I'm not convinced it's worth attacking this type of speculation; effectively what it is is mapping out the boundary of our ignorance and attempting to see at least a facet of what might be going on beyond.
The difference comes basically because the picture behind Hawking radiation is of a virtual particle pair coming out of the vacuum, and then one ending up behind the event horizon. The process by which that virtual pair come into existence is very different to the process suggested for the mini black holes, where so far as I understand it the idea is basically down at the Planck scale there is no stability in an individual "node" of the foam and you get these "black holes" continuously coming in and out of existence -- the concept of spacetime itself is breaking down, because it's a description assuming continuity, and at the Planck scale there *is* no continuity; can't be. Instead we have these little building blocks, each the size of a Planck volume.
Of course, all that could be bullshit too. That's the fun of speculative physics - postulate a picture that might work, and push its edges to try and make predictions (any predictions, something string theory has been pretty weak on) and find behaviour that might break the theory.
TL;DR - without denying anything you're saying, I think the spin you put on it is too critical, it's about trying to see aspects of a theory we can't work with directly.
Slashdot Mirror
Yeah someone else pointed that out (or perhaps it was you in another comment) :) This is quite a silly story in the first place - insider trading is serious, but the summary doesn't seem to have been checked particularly thoroughly and this being Slashdot I've not bothered reading the article.
That doesn't justify the 7-2=7 thing. (Let's assume time changes are implicit, being a thoroughbred European as I am I might be forgiven one or two lapses on US timezones.)
"it's still to early to write C++11 code for any real products"
What you seem to mean is it's too early to write C++11 code for any real products if your development team aren't up to speed with it. That's a totally fair statement, but it's clearly not true that it's too early to write C++11 for real products -- we do. We're liable to swap to C++14 as soon as commercial compliant compilers become fully stable and settled (and, of course, that we can convince our IT support to license them, which may take a year or two).
[Caveat: my personal experience with C++ was first with a Borland compiler probably not fully compliant with C++98, and then onto an MS compiler compliant with C++11, and a gap of 12 years. The language I came back to was significantly nicer - for my way of thinking - than the language I left. So I'm rather biased towards C++11 and even more so towards what I see coming up with C++1Y.]
The Federal Reserve announced a change in interest rates at a particular time - 2PM, Washington time. Trades were placed in Chicago 2ms after 2PM. It takes about 7ms for news to get from Washington to Chicago. As a result we can say two things:
1) Someone has been dabbling in insider trading, or has a loose mouth. Either way, if they become known, they're in deep shit.
2) Slashdot editors don't proof-read their submissions, given that the summary states it takes 7ms for a message to get to Chicago, that 2-3ms after 2PM trades took places on the Chicago exchanges, and 7-2=5ms, not the 7ms we were promised was stolen.
The alternative of course is time travel, which I'd much rather was true. A couple of years back we had a couple of crackpot papers on the arxiv that can be interpreted as saying that the Higgs boson was travelling back in time and sabotaging attempts to observe it. Perhaps this is evidence that the Higgs is getting more subtle.
You're more than welcome, thank you for appreciating them. (I did my Masters thesis on acoustic holes in Bose-Einstein condensates, and while I've forgotten most of the details myself I can still be a massive bore on the topic :) )
With acoustic holes probably the easiest scenario is to imagine a sheet of water running downhill, getting faster the whole time. It's important that there is no turbulence and virtually no friction so that the inside of the sheet is basically a "perfect fluid". (This is impossible in reality but it's a good image.) At some point down the slope the flow will go supersonic. Above that point you can fire sound waves back up the slope and they'll move -- slowly, because they're being swept down at the same time, but they'll still move up. Below that point, the flow is supersonic and so the sound wave is swept along with it. The point at which the sheet goes supersonic can be very loosely, hand-wavingly, seen as an "acoustic event horizon" -- no sound wave can escape from over it. When you model it properly, you find that it's a lot more concrete than that and that actually it *can* be described as an event horizon, and the sound waves are moving as if they're light waves in a Schwarzschild geometry, and the analogues go further. (They don't work for perturbations on the hole, though because the underlying physics here is pure Newtonian; nothing to do with gravity at all.) When you look at the situation in a quantum fluid you see that you do get Hawking radiation, too.
Lovely stuff :) Matt Visser is probably the clearest I've read on this topic but on the whole what he writes is for PhD level physicists - but if you can find a popular level article he's written it would be very well worthwhile. Ulf Leonhardt has written some articles on analogue holes (often in optical systems rather than acoustic, but the same broad principles apply) that are worth trying to track down, too.
You learn something every day! I'm going to look into those, thank you.
Calling corn 'wheat' a default is a good way of putting it - it was what I was trying to get across in more words. "Corn" is ultimately related to "Kernel" and does certainly come from "seed", "grain". But the language evolved so that now it's a catch-all for grains, and wheat by default across most of Europe. Of course, I want the kids off my lawn and the language to stop evolving ;)
Very true. For my own comfort I tended to stick within pure Fortran programs - I'm still more comfortable in Fortran than in C or C++ - but there were things that were better to do elsewhere, particularly where I had access to a library that I much preferred (say, in C, which happened quite a bit) to what I easily had available in Fortran. Sure, I could have gone hunting but it was a lot easier to build a trivial wrapper around the C library and just call that. I can't actually remember why I didn't like the Fortran interfaces for the GSL that were around but I ended up building wrappers around quite a bit of that at various times.
I've long been tempted to get a .net compiler for Fortran. That would make it *really* easy to build some ugly Java.
"That's an almost meaningless statement, unless you define what is "OO" (ten programmers will give you twelve different definitions for that)."
Very true. In this exact context I'm meaning an object containing functions that are contained within its namespace. There's almost certainly actually a way to do that in modern Fortran but I'm not aware of it, and instead I use modules as a rough analogue of a class and select the functions from them that I want to use in a particular method. (I can also get around quite a bit of the issue by overloading the function names in the interface, if it seems that important. Normally it doesn't, to be honest.)
"Eventually somebody will teach the computers to convert the Fortran to a readable and easily understandable modern language - while both keeping the behavior identical and highlighting likely bugs and opportunities for refactoring."
That language will likely be Fortran 2008 or 2015...
Not at all. It might be a bit more monocultured than, say, C++ but there are still more than enough ways to skin the same cat that you end up with a ton of cat parts and a mass of confusion.
A pedantic note - it hasn't been called "FORTRAN" since Fortran 90 was introduced. Otherwise it's nice to see people defending it for scientific applications :)
Oh now, that's a bit harsh. Programming in Fortran isn't something done because people are afraid of work. I genuinely get tired of the incessant Fortran-bashing by people who -- in my experience, at least -- have almost never, if ever, actually used the language or seen why other people do. In most cases they seem to be repeating jokes their lecturers made about the language, jokes that were first written back when FORTRAN 77, with those stupid capitals and all, was the dominant form.
Now, I'm very much not a fan of F77. In fact, I hate the language. It's clunky and decrepit and not suited for modern programming practices. But it's easy to call from later Fortran standards, and each one has vastly improved the situation. Fortran 2008 is a genuinely nice language. True, it's not OO - though you can force it to act almost as if it is - but not everything has to be forced into OO. What it is is extremely good for numerical work, and dealing with arrays in particular in Fortran is a dream after, say, C, or even C++11. The fact it calls F77 routines without effort or pain also helps, since there genuinely is a vast body of code still in F77. (The oldest I came across was F66, ported directly from Fortran IV. Now that really did need to be rebuilt in something approaching a sane language.)
I'm not saying F2008 is "better" than either C or C++11 -- that's a meaningless statement. But there are things that make it a very nice language to use, and other things -- character strings, I'm looking at you -- that make it distinctly unpleasant. Same as any other language, really.
I'd suggest you don't be so pious. I'm for protecting the language as much as anyone else but ultimately it evolves. I don't think this is really about the people employing numerical techniques in science becoming "more poorly educated"; I think it's about your field branching out and attracting new jargon and new uses for the old jargon. It's just what happens.
As it happens, I've spent close to ten years in academia where we build "codes" (typically in Fortran -- 90 or more recent if you were lucky; 77 if you weren't) to solve problems. I have since moved into professional development, chiefly in C++ and occasionally in C#. The use of the spoken language changes and the two fields have different ways to express the same concepts. Ultimately I don't really see a major problem with this.
All that said, misuse the word "corn" and I begin to get extremely irritated so I probably shouldn't be so pious myself... :)
[In British English "corn" doesn't mean maize, it means wheat, or occasionally barley -- more accurately, it means the chief arable crop of an area. When English speakers settled North America, that chief arable crop was maize, hence the American usage. What annoys me isn't Americans calling maize "corn" -- which is entirely valid in both North America and in their dialect of English -- but rather the *British* thinking that corn is maize. It isn't, it's wheat. I also wish they'd get off my God damned lawn.]
I didn't mean to sound argumentative at all! But I did read it entirely the wrong way...
evidently you don't feel that bullet points are a useful bit of functionality. fair enough, but there are plenty of people who would disagree with you on that one...
Depends very much on your model of dark energy. I'll go a bit out on a limb and say that we don't have anything approaching a convincing model of dark energy right now, with the best we have being that a cosmological constant exists. We do understand the spacetime of a black hole embedded in a universe with a cosmological constant - it's known as Schwarzschild-de Sitter space - and while that doesn't say how a universe of black holes and a c.c. behaves it's pretty telling that nothing extraordinary happens. But it does rely on a couple of assumtions (well, many more than that, but two significant right now): firstly, that dark energy is a cosmological constant, and secondly that we can describe the interaction of black holes and dark energy through semi-classical analysis. That means that we can use a black hole solution from general relativity and (potentially) a quantum mechanical description of the cosmological constant: assuming the quantum nature of gravity has no effect. Possibly not true. Moreover, dark energy may not be a c.c., or not only a c.c., in which case frankly bets are off, including on how the dark energy would behave inside a black hole. (It's not even immediately obvious it would act as you'd expect a dark energy too. Interior solutions for black holes are very strange beasts.)
I think it really helps to remember that thermodynamics is an *emergent* theory: it's only valid when you're talking about vast numbers of particles. There is nothing, for instance, that stops a few electrons -- even in isolation -- grossly violating the second law of thermodynamics and settling into a state of vanishingly low entropy. Just that, when you look at larger systems they will never, as a system, move to a state of lower entropy.
Putting it another way, look at the gas bouncing around your room right now. That's roughly 75% nitrogen, so let's pretend it's all nitrogen to make life simpler. Go down to the level of a nitrogen molecule. You've got a roughly axially-symmetric molecule, shooting through the air, colliding with other axially-symmetric molecules (at arbitrary angles) and occasionally slamming into the wall. Modelling that single molecule would be excruciatingly tough. Doing it for the, let's say, 10^28 nitrogen molecules in your room right now would be punishing, and also extraordinarily uninformative.
However, we can instead of looking at a nitrogen molecule concoct descriptions of the entire ensemble of nitrogen molecules. When you find concrete ways of describing them as a whole, you're lead to define entropy reasonably early on, and then lead to define temperature and various energies and enthalpies and the rest of the paraphenalia. In short, you get out the entire structure of thermodynamics, *from a system that had nothing to do with it and never mentioned it*. That's emergence: a large collection of objects exhibits behaviour that is entirely unrelated to the underlying physics.
That being so, very small collections of, well, anything, cna violate thermodynamics however they like. On anything like macroscopic scales, no chance. (Well, virtually no chance.)
Along the same lines you might be interested to look at acoustic, or "dumb", black holes, which occur in any viscosity-free, irrotational (barotropic but ignore that one) fluid. The sound waves propagating through such a fluid -- which is totally Newtonian -- act as if they're photons travelling through Schwarzschild spacetime. In principle, we can build these things in Bose-Einstein condensates and, technically, it's already been done. Problem is that we can't measure Hawking radiation from them because at the minute they're way, way too weak. Anyway, point is that the physics governing these is Newtonian (or in the case of a BEC is a collective quantum statistical mechanical thing) but that the *collective* behaviour of the sound waves is that of photons travelling through curved spactime.
Quite fascinating.
TL;DR: too long, don't bother reading.
I'd say "ignorant" rather than "stupid", making clear that "ignorance" is not perjorative. No-one should ever be ashamed of admitting ignorance, and no-one should ever call themselves stupid for asking an honest question :) I probably can't answer your questions to anything like your satisfaction because I'm bouncing well against the limits of my own ignorance, but at least I might have a slightly clearer perception of things (and therefore make much larger mistakes...)
"If black holes form in the quantum foam wouldn't this phenomena be present within the first few milliseconds of inflation?"
Probably, yes. It would depend on the details of the theory - and indeed whether inflation would occur at all; while inflation is an accepted component of the standard cosmological model let's not forget that it relies on a scalar field (whether physical or effective) whcih has never been observed and is not really in itself realistic, including contrived models that employ the Higgs as an inflaton. But that aside, since it seems very likely that something similar to inflation had to have occurred, then yes, these effects were probably active very early on. Inflation probably diluted the early black holes to an extreme degree though; early motivations for inflation focused more on diluting magnetic monopoles and primordial black holes, along with solving the horizon and flatness problems, than modern motivations do. (If you're interested, the modern motivations are much more that you easily get a "scale-invariant" spectrum of ripples in the extremely early unvierse, which matches observation perfectly. Any alternative to inflation absolutely has to reproduce a nearly scale-invariant spectrum.)
"Would that allow for them to gain enough mass from the density of material surrounding them to not evaporate instantly through Hawking radiation?"
No idea. If inflation were rapid enough, probably not, but no-one could say for certain without a more complete model of quantum gravity.
"If that is possible could early black holes have come about not through supernova but through the quantum foam?"
That's certainly a possibility. Even without this (speculative) support through spacetime spongecake primordial black holes could be sufficiently abundant that they have been repeatedly studied. Any means of support would feed back into the problem and warrant its re-examination.
I would certainly agree that we should take a position of extreme scepticism towards Penrose's claims that quantum gravity gives rise to consciousness.
My contention is that Penrose is one of the greatest general relativists of the mid-late 20th century, and has only been overlooked because Stephen Hawking is in a wheelchair. What I'd judge as Hawking's greatest successes - and they were very great - were in collaboration with Penrose (in the singularity theorems), in collaboration with Ellis (covariant fluid dynamics) or were formulated in that period and aided by conversations with people like Penrose and Ellis (such as Hawking radiation). I would class the three of them as amongst the greatest physicists of the later 20th century, along with people like Kip Thorne, John Wheeler and Stephen Weinberg.
Unfortunately Penrose has also made a lot of strong claims he can't prove, and other speculations that he can argue and seem to make sense when he argues them in person, but which ultimately are very unconvincing. The quantum gravity leads to consciousness thing is certainly one of those.
Please don't hold it against him: the man is an extraordinary physicist.
Same as you shouldn't hold the papers he's put out with Gurzadyan in the last couple of years against him. Penrose has never claimed to be an observational cosmologist, nor a statistician. I believe, though I've never met him to ask in person, that he went along with Gurzadyan's papers because he thought that this was potential evidence for his pre-big bang model of cosmology. Unfortunately the circles on the sky that they identified are very, very definitely *not significant*, no matter how they try and argue it against people who are genuine experts in the field (and much more than I; I'm a weird cross-breed between theorist and observer, and therefore nothing like as good at theory as Penrose and nothing like as good at observation or stats as the people who so easily and convincingly dismissed his papers with Gurzadyan).
In the way you mean it, it doesn't. The event horizon is just that - anything inside of it doesn't interact with anything outside of it. It's simply where the name comes from. A 4-dimensional point in spacetime was dubbed an "event", so two regions of spacetime which can't see each other -- at any point in spacetime -- were said to be separated by an "event horizon". So a blackhole doesn't interact with anything, basically by its very nature.
However, it *does* cause a big curvature in spacetime. The main point is that it's no different from a star. Look at the physical situation: you have a star, which is a body supported by a balance between the pressures generated at the centre by fusion, against gravitational collapse. After some transitions from hydrogen burning up to, say, carbon burning (the end point is different for various stars but the ultimate limit is that stars don't burn iron; you lose more energy than you gain trying that, so it doesn't support a star) the fuel at the centre is exhausted and the star collapses. If it is heavy enough, it simply doesn't stop collapsing.
Now consider the spacetime geometry around it, and idealise a bit. Then before the star starts collapsing we have a massive spherical distribution of matter. Excellent. That's described by a Schrwazschild metric -- *any* non-rotating, chargeless, spherical distribution of matter is described by a Schwarzschild metric. (It's known as Brikhoff's Theorem.) But that will be true as the matter begins to fall across the Schwarzschild radius, assuming the physical conditions are such that it does so rather than bouncing (which depends on a vast number of parameters, including how massive it was in the first place, how fast the outer envelopes are falling when they hit the burnt-out remnants of the core - too fast and they may shatter the core which causes a bounce and ultimately a supernova... except even that may or may not leave behind a remnant white dwarf heavy enough to collapse first to a neutron star and then to a black hole - or it may tear the core apart completely, or end up in one of the intermediate states etc.). There's no reason to assume that the external geometry changes just because something suffers spherical collapse, right? That was true in Newtonian gravity and it turns out it's true in GR too -- the gravity outside a spherical object is the same as if all that object was concentrated at a point in the centre. So a collapsing spherical shell doesn't change the geometry. THe problem here is that the collapsing shell will pass through the event horizon. Nothing dramatic happens here -- a key tenet of GR is that we can always locally (for a given definition of "local" and that may be extremely local indeed) see things as if they're on flat spacetime. For astrophysical black holes that "local" is actually rather large. A coordinate system known in GR is the Painleve-Gullstrand system, which looks a bit odd but describes Schwarzschild space exactly (outside the horizon). Unlike "usual" coordinates, in Painleve-Gullstrand coordinates absolutely nothing untoward happens at the horizon: to something falling through it it looks like normal spacetime. The point of this tedious diversion is that nothign happens to the infalling spherical matter of the star when it passes through its own event horizon.
That then means that a black hole can form perfectly happily; no interaction with the outside universe is needed (and indeed doesn't mean much). If you were stupid or homicidal enough to chuck a colleague in, from your point of view he would mvoe slower and slower and get fainter and fainter as he approached the horizon, and you would never see him reach it.
From his point of view (if we ignore the spaghettification that would actually rip him to bits in most astrophysical holes) there would be nothign strange; he would rapidly cross a horizon he couldn't even identify, and then a microsecond or so later would inevitably slam into a future singularity that he could no more avoid than we can avoid moving into the next minute of our lives.
"you are monopolizing, so I ask you directly."
Yeah, sorry :(
"how then can gravity escape, considering that the highs has measurable mass, in the gev range?"
The Higgs doesn't carry gravity. The Higgs field imparts mass to fundamental particles (and the Higgs boson is the particle associated with that field, though the particle itself does nothing for mass), but that is a very different thing. Quantum field theorists will describe gravity by *gravitons*, which are also bosons but where the Higgs has spin 0 -- identical from every angle -- the graviton has spin 2. The Higgs has a high mass, while the graviton is massless. Unfortunately this is itself a semi-classical picture, since these quantum field theorists have to specify a background spacetime to propagate a graviton along... utterly defeating the point if you're trying to look at this type of effect. (A massless particle would travel on the same paths as light - so a graviton in this language would evidently be trapped behind the event horizon.)
Instead when you're talking about regions of high spacetime curvature you should drop the language of gravitons and work straight with the geometry. I know a lot of quantum field theorists would mock me for that point, but I think they're as wrong as they think I am. Our best theory/theories of gravity are geometric in origin; the effects of gravity are not caused by a force but rather by curvature in the space we're traveling through. We try and go in straight lines, just those lines are curved. In this language you don't have any questions about gravity "escaping" from a black hole since there is nothing carrying gravity; it's just curvature in spacetime. A gravitational *wave* is a different thing - a ripple in spacetime - and while you'll hear people loosely talking of black holes emitting them, those waves emanate from outside the horizon. No wave will come from inside.
If we fired a Higgs into the black hole, it wouldn't come out again. However, that wouldn't do the mass of any fundamental particles in the area (things like the electron, and the quarks - protons and neutrons are not fundamental and most of their mass comes from binding energies rather than interactions with the Higgs field) because the field itself is still permeating the space outside the black hole.
Hopefully that's cleared at least one or two things up and not made it worse.
Well, certainly this is speculative physics but in this field that's not really something to attack - merely something to be aware of. We don't have a properly working quantum theory of gravity to understand what's actually going on down at this level, so this kind of paper is simply reasoning something that would happen were a particular set of assumptions valid.
Black holes on smaller scales would almost certainly exist, but it does depend on what you mean by "smaller", of course. I don't think anyone would argue that black holes down to the femtometre scale are entirely plausible. The problem on smaller scales comes basically because of the hierarchy problem: gravity is astoundingly weak compared to the other forces. In the context of the field theories that underpin the standard model of particle physics, that means that on scales at which those forces operate, gravity is probably (note "probably") adequately described by semi-classical calculations - quantum fields, but living on a classical background spacetime. It's only on smaller scales, loosely as one approaches the Planck scale, that the quantum effects of gravity would have to be taken into account.
Of course, even that might not be true, but it's the best guess we have at the minute and if we don't investigate ideas that come out of attempts to improve the situation we'll make absolutely no progress at all. I'm not convinced it's worth attacking this type of speculation; effectively what it is is mapping out the boundary of our ignorance and attempting to see at least a facet of what might be going on beyond.
The difference comes basically because the picture behind Hawking radiation is of a virtual particle pair coming out of the vacuum, and then one ending up behind the event horizon. The process by which that virtual pair come into existence is very different to the process suggested for the mini black holes, where so far as I understand it the idea is basically down at the Planck scale there is no stability in an individual "node" of the foam and you get these "black holes" continuously coming in and out of existence -- the concept of spacetime itself is breaking down, because it's a description assuming continuity, and at the Planck scale there *is* no continuity; can't be. Instead we have these little building blocks, each the size of a Planck volume.
Of course, all that could be bullshit too. That's the fun of speculative physics - postulate a picture that might work, and push its edges to try and make predictions (any predictions, something string theory has been pretty weak on) and find behaviour that might break the theory.
TL;DR - without denying anything you're saying, I think the spin you put on it is too critical, it's about trying to see aspects of a theory we can't work with directly.
haha two whacking mistakes in a post that claimed it wanted to avoid pedants. i have to try harder in future...