Precious few stars in our vicinity are going to go supernova anyway. Arcturus probably will but i don't think any of the others are anything like big enough. Sirius is the only other possibility within I think 30 light years or so, and for some reason I'm getting the dim memory of being told (at uni) it's too small. Supernovae are really not that common.
actually it needs basically dark energy. if you believe that dark energy is responsible for the acceleration of the cosmos, you are lead to believe that alcubierre solutions are viable. an enormous caveat is that you also have to believe that quantum gravitational effects won't destroy the system. you also have to believe that it's a *physical* solution; like pretty much every solution in relativity it assumes that it is the *entire* spacetime, past, present, future and all the way to spatial infinity. that's never going to be the case. even in deep interstellar space you've got an absurdly complicated mess of "solutions" coming from the various combined star systems and their planets. the spacetime around you is only locally flat; the asymptotic infinities bear only an approximate resemblence to those of flat spacetime, and the overall causal structure is very different (you'll run into a black hole along a multitude of directions, if nothing else.)
and we have no clue if you can still make something like a "warp drive" solution viable, even assuming we can harness dark energy as a source, which even assumes it exists in the first place.
so it's a tricky issue - even trickier than you say, even though such a material *is* theorised to exist.
That's entirely possible. I found it no more annoying than sudo perhaps not least because I'd been an admin on Solaris and Linux boxes at work for ages, so I knew what it meant. My Dad.... no.
err, you've only used uac on a machine where you're logged in as a user with admin rights, then. anyone who uses a machine with admin rights as default deserves what he gets, no matter what the os. using linux with admin rights by default is pretty fucking stupid, i'm sure you'd agree - let alone using *windows* with admin rights which is insanity.
if you run as a user without admin rights, windows vista uac demands an admin password. how good that implementation is i don't know - no doubt there are ways around it, i don't know. but it's an authentication screen demanding sys admin rights.
if you already run as an admin then it's your own bloody fault what happens to the computer. and unlike *nix sudo, it does demand an admin password, not your own password (at least, not hte way it's set up by default). how much a security gain potentially needing two passwords (compromised account + admin) is compared to one (compromised sudoers account) is is totally debatable, of course, but at least the way vista set uac up as default you needed an admin password if your user account wasn't admin.
so all but two paragraphs of your rant are, to be fair, based on something that's pretty much false (unless the windows box was set up by an idiot who automatically runs as admin - which i guess even you'd admit is pretty dumb even in a linux box; and at least there the windows machine still says "do you want to do this?" while when i've run as root on a linux or osx machine they've tended to trust that i'm running as root therefore i can do quite a bit without prompting) but did let you talk about "dumb, paranoid Windows users" and bask in your self-satisfied linux glory. well done, i salute you.
"Pro-Microsoft posts will lead many to brand you a 'Microsoft Astroturfer'."
which is impressive given i also said their security record is shit and the w7 kernel is stuffed with security flaws... ah well, i've never bothered karma whoring.
i gave up trying to educate people in security when about ten years back i tried to explain to my dad (who is far from an idiot with computers compared with others i know, who are far from idiots in real life) why it's a bad idea to run as an admin and why you log into your computer each time. he didn't understand. too stuck on the old single-user model he'd seen with the sinclair spectrum, dos 5, dos 6, windows 3.1, windows 95 and windows 98.
i *think* he gets it by now, but his machine is still single-user admin rights. so i despair.
I'd say I don't know who'd do anything different but then I remember my parents' W7 machine is set up as single-user, automatic login and user has rights. So UAC is just a click-through and totally pointless.
I've run Windows as a limited user ever since 2000. My experiences with Vista are by no means typical of normal people, and since I'm primarily a desktop user (plus latex plus intel fortran plus xming plus emacs) are also by no means typical of every Vista user...
Yes, I did, I got it before SP1. I had Ubuntu dual-booting on the machine at the same time and was running a Macbook with Tiger, followed by Leopard. (I think I had openSuSE and Arch on the machine at various points too but I defaulted to Ubuntu after a while.) I honestly didn't notice much difference (unlike the entertainment of watching mod points go up and down on that post:) ) -- at least in how annoying it was.
W7's approach of letting you set the level of UAC introduced an extra security flaw. That was really my only point... Off-topic, and so far as I know, accurate, and backed up by a totally subjective judgement on Vista's UAC vs sudo and OSX's authentication prompt.
MS *tried* to fight it (in part) by effectively adding a GUI sudo prompt into Windows Vista. A million people -- including Linux users posting on Slashdot -- immediately flew into fits of nerd rage about how annoying it was to have a GUI sudo prompt. (I never saw an issue with it myself, actually. Seemed no more irritating than going sudo on Linux or OSX's own authentication prompt. Unlike many, I actually really quite liked Vista, although I use OSX most of the time.) MS listened to their users and allowed them to scale it back in Windows 7, creating a million new security holes and causing a million people -- including Linux users posting on Slashdot, although not necessarily the same ones -- to complain about security flaws in Windows.
MS have made many stupid mistakes over their history and not least due to the ancient and creaking XP (and, even worse, the immediately-owned ME) have a history of shit security. Thing is they tried to patch it up in an easy way and people bitched and puled enough that they had to make it less secure again.
That, of course, ignores the other few million security flaws riddling the kernel. I'm just talking about the UAC here.
Ah, I think I see your issue. The quick answer is that (if you believe the big bang model, and it's extremely hard to get a CMB from other models that fits observations; Hoyle tried quite a few times and he could get a blackbody, somewhat unconvincingly, but he couldn't get the right anisotropies on it) the CMB isn't bouncing around -- we see different photons the whole time. I'll try and explain. Let's say for the sake of argument that the universe is closed because it makes our conceptual job a bit easier. The same arguments would apply to flat and open, but let's not play around with infinities if we don't have to.
So we've got a finite universe, and it's totally filled with different types of matter. Filled to the brim. Most importantly, it's got hydrogen nuclei (which I might slip up and call "baryons"; that's true, so far as it goes, but there are many more baryons than hydrogen nuclei....) and it's got photons and electrons. It also has some helium nuclei but they're relatively unimportant. These fluids are tightly entangled to one another because the universe is hot enough that the photons immediately ionise hydrogen, sending electrons flying out of the atoms and back into the plasma. This is going on *everywhere in the universe* -- in the same way that we're pretty certain that everywhere in the universe right now planets are orbiting suns.
Then the universe cools enough that photons suddenly don't have the energy to ionise hydrogen. This happens everywhere in the universe at the same "moment" (ignoring for now issues of time in general relativity, which just confuse the issue; let's instead say that it happens at the same "scale factor", which you can view as characterising how much space has expanded from a certain point, normally set as today). Then the point in the universe that would become the home of the Earth received CMB photons immediately after its formation (and was drenched in ultra-high energy gamma radiation). The universe expands, and a few years later the point the Earth will be in is receiving photons that were emitted a few years beforehand - which the expansion has stretched, cooling them down. Twenty years later, it's receiving photons that have been stretched by 20 years' worth of expansion. Each time it's receiving photons that were emitted further and further away from it at the formation of the CMB.
The same goes as the universe continues to evolve. Today, the Earth is receiving photons that were emitted when the universe grew cold enough to form hydrogen atoms - from points which were far enough away that it took more than 13 billion years for them to reach us.
This wouldn't work if the matter in the universe were all concentrated in a few points. Instead you'd have had a wash of photons that end as those from the points furthest away from us reach us. (In the jargon, it ends when the points furthest away enter our past light cone.) But that's not the big bang model, which smears the matter in the early universe out across the whole thing pretty much evenly.
If the radius of curvature of the universe was sufficiently low, we'd now be seeing photons getting to us that have done the entire circuit. The effect of that is particular patterns on the observed CMB, which haven't been seen. That's one way of constraining the size of the universe (if you assume a trivial topology) or of constraining the topology. And yes, observations will only ever directly be able to put limits on the radius of curvature; there is no way of telling from this kind of argument whether the universe is actually flat or not.
Of course, all this relies on you accepting big bang cosmology, but it does better than any conflicting theory I've ever heard of, for all the issues that crop up.
The Earth being at the centre of things is one such conflicting theory -- I don't think anyone proposing these actually wants to put the Earth at the centre of the universe, not seriously. The Copernican principle is deeply ingrained in us, hence your objection to it, I guess. I don't want
The first analogy I was taught at university is still a really good one. Imagine being at the centre of an infinite football stadium and the crowd are cheering. At one moment for whatever reason, they all stop. What do you hear? You hear the final echo coming towards you from evermore distant rows of seats. This goes on forever, just with the sound getting fainter at fainter.
The CMB is the same kind of thing. Back in the early universe when it was younger than about 370,000 years old the temperature was *way* too high for hydrogen to form, so it was a massive mess of protons, electrons and photons. (And neutrinos but the temperature by then was way too *low* for those to interact much.) Sure, electrons would combine with protons to condense into hydrogen but an absurdly high-energy photon would immediately smack it back out again. But at about 370,000 years old the universe was cold enough that suddenly there weren't high-enough energy photons around to do that (remember they have to be about 13.6eV.) So suddenly there's a "last scattering surface" formed - the photons suddenly stream free.
Effectively the CMB is just a photograph of the universe as a baby. It's not coming from the edge of the universe at all; it's all around us because it happened to the entire universe at about the same time. Of course, since then light from the CMB has propagated across the universe and been manipulated in various ways -- the most significant are the "integrated Sachs-Wolfe effect" which is what happens when light falls into a gravity well that shrinks due to cosmic expansion before it climbs back out again; the "Sunyaev-Zel'dovich effect" which is how badly galaxy clusters fuck up the light as it comes through; and "reionisation" which is when the first stars lit up, massive, powerful beasts that immediately stripped most of the hydrogen in the universe back into protons and electrons again (which then got in the way of the CMB, though mainly influencing its polarisation rather than anything else).
The smoothness of the CMB is *evidence* for a Big Bang cosmology for a couple of reasons. First, the fact we see it as so smooth -- and it is, unarguably; it's to one part in 10^4 if you wipe a Doppler effect which is normally attributed to our velocity with respect to the CMB though there are other explanations -- strongly suggests that the universe was exceptionally smooth when it formed. If you put that into general relativity you're driven pretty much uniquely to Big Bang cosmology. If instead you take an alternative approach then when you set the initial conditions for a Big Bang cosmology, normally at about the first second so you're safely away from the splittings of the forces and from nucleosynthesis (meaning you can firmly say "I have about 75% hydrogen, 25% helium and traces of everything else), one of the things you find you're required to do is to set the photons up to be totally smooth. By the time you hit the CMB that's still there because all the ripples caused by the interactions are extremely small up until the universe is much, much older.
No idea if that helps persuade you, of course.
As for topology, the CMB is a great place to look because of the propagation of the light since the formation. It's not that it maps the edge of the universe; it doesn't, at all. It's just a bath of microwaves left over from when the universe got to the right temperature. What it does do is give us hints about the paths photons have taken since. We've got very good guesses to what the ripples on the CMB look like (check out http://en.wikipedia.org/wiki/WMAP for the current state of the art, or http://en.wikipedia.org/wiki/Planck_(spacecraft) for the eagerly-awaited data) which seem very solid. So you can look for any odd changes in that coming from, for example, a donut-shaped universe. The easiest way is to look for "circles in the sky" which are a signal that the light has wrapped around and com
...what's that got to do with anything? I don't think a couple of NASA teams cocked up and splattered a probe across the face of Mars because they had an argument about what a galaxy is. Did you miss "in this context"?
Even if we follow your weird jumps of topic, it still has nothing to do with anything. What we choose to call a galaxy is a matter of nomenclature, taxonomy. Whether we use metric or Imperial measures is a choice of units. There is absolutely no comparison between them. A choice of taxonomy is ultimately a choice of how to present things to the general public. A choice of units is a choice of how to address the problem. A NASA team not saying they're using inches instead of centimetres is a sackable offense. They could have "communicated their ideas clearly" to the other teams (stretching the use of the word "idea" here) simply by writing 10" instead of 10 on their reports. They didn't. That's not the fault of any definitions and it's not even the result of working in Imperial units. It's their fault for being ham-fisted and incompetent. The ability is there to communicate clearly and has been since Imperial and metric units were first codified.
There's no comparison between the situations whatsoever.
Yes, they have. Not quite that way, but yes. The conclusion is that if the universe has a non-trivial topology, it's scale is much bigger than the current "radius of the universe" (actually much bigger than the current Hubble length) because no evidence of this kind of thing has been seen. They've tested for if the universe is spherical, which is probably closest to what you're meaning, although in that case there are many other effects that we would see extremely clearly and simply don't. They've tested for whether it's donut-shaped. They've tested for whether it's shaped like a football (as in a soccer ball). They've tested a few other weird configurations. No evidence yet, except a very slight tendency towards the universe possibly being very, very slightly spherical -- if it is, the radius of curvature is extremely large.
virialisation. there are scales beyond which objects are not viralised, which can be taken to mean they're not gravitationally bound to one another. gravitationally *influenced*, yes, but not bound. there's a clear enough definition.
or, if you like, if you're talking galaxies and clusters of galaxies, you can call them "gravitationally bound" when they detach from the hubble flow. the "hubble flow" is the expansion of the universe as a whole. when objects are close enough together, their gravitational attraction to one-another overcomes the cosmological expansion. at that point they "detach" from cosmology.
it's a loose way of saying it but a physically lucid one. a more precise way would be to say that when a perturbed robertson-walker metric (which underpins cosmology) no longer adequately describes a cluster of galaxies, that cluster has probably detached from the hubble flow. the cluster will be described by some horrific pseudo-spherical metric and not robertson-walker. to the rest of the universe it may as well now be a solid block. that's the point you could call it "gravitationally-bound".
"except in this case, it need defining so we can catalog the finds appropriately."
No it doesn't. Trust me, no it doesn't. Go and hunt out the latest SDSS data release. Do you see a million arguments and complaints that people can't quite tell whether they should include something or not in case it's a galaxy or not? No, because they don't care. It's a massive catalogue of galaxies. No-one cares what "galaxy" means; it's just a catalogue of all the luminous matter the SDSS can see.
Or let's go a bit more technical. An important subset of the Sloan are the luminous red galaxies. How are these defined? Well, for the general public, they're "luminous", "red" and "galaxies". That's all anyone actually needs to know. Defining them for the actual Sloan analysis is much tougher and is done first with a lot of cuts based on redshift (itself tricky to identify and normally done photometrically because of the sheer number of galaxies in the survey) and then cuts based on "colour" (ie luminosity in a particular frequency band). And it's much, much harder and more convoluted than it sounds, and I don't actually understand much more than this myself. Is there any point going into all of that for a press release? No, you just say "we picked out the most luminous, red galaxies from the survey". Who seriously needs anything more? No-one except other astronomers, who don't really care if they call it a "galaxy" or not because it's the science that's important and not the taxonomy. I know how sententious that sounds but unfortunately it's true, the important things are the results you get, not some petty little argument about whether this is a "luminous red galaxy" or a "fairly luminous, almost red possibly galaxy".
The same goes with every single catalogue. Back at the start of it all, Messier just made a massive list of "nebulae". These days we know some of his nebulae were what we not call nebulae, others were what we call globular clusters and others were what we call galaxies, but we still use the Messier catalogue numbers. As a rough guide, in any catalogue we need to know: redshift (or straight distance if it's near enough to get distance from, say, Cepheids), total luminosity, rotation curves if possible, morphology which is closely related to the rotation curves, stellar luminosity and mass distribution, and other things like that. We don't actually need to tag the word "galaxy" onto things, no matter how much you might want us to. It's totally unimportant.
But... in this context - and it's seriously useful to stay in context - scientists *can* effectively communicate their ideas. Clearly, too. No-one outside of astronomy gives the slightest fuck what the difference is between a large globular cluster and the smallest of dwarf spheroidals, and neither should they. I can make it clear in the context what I'm meaning by "galaxy" and the word is loose and flexible enough that it can fit what I want. The only people I've encountered who care are people who wanted to be astronomers but either didn't or couldn't get good grades on the degree. The kind of people who are in it for the pretty pictures and not the science -- basically, butterfly collectors of the heavens.
(There's nothing wrong with the pretty pictures, by the way. I got into astronomy through star-gazing and popular astronomy books, the same as anyone. Just that there's more to it than taking a photo through a camera and sticking it on some website.)
Not content with making us all look like total fuckwits with the whole debate over what makes a planet - as if it matters in the slightest - some dingus is going about kicking up a fuss about what identifies a galaxy. Seriously, who gives a toss? The important thing is the science, which doesn't change whether we call a particular virialised cluster of stars a "cluster", a "galaxy" or "peter". The taxonomy is beyond unimportant.
The only place I can see that this kind of thing has is in education (and, yes, perhaps talking with the general public). And even in that case... who cares? Who said that we have to have some serious rigorous definition for everything we say when communicating in a general manner? I can sit there and have a loose definition of the word "galaxy" that changes depending on context and not only will the journalist not notice any slight changes but *they won't care*, and neither will their readers.
Stirring up something like this, though, just makes us look like a pack of dithering idiots who don't know what we're talking about.
So far as I'm aware, the convention is simply to centre your coordinate system at the most convenient point, which depends what you're wanting to do. You can always transform to a different reference frame. It's not actually *that* important. For doing the Earth/Sun system you'd most likely just lock it to the Sun since the difference between that frame and the centre-of-momentum frame of the Earth/Sun combined is utterly negligible. For the Earth/Moon system you might put it at the centre-of-momentum frame of the two or just lock it to the Earth. For Pluto/Charon you'd use the centre-of-momentum frame because Charon's orbit would look totally weird.
Just depends what you're interested in, really, and it's not that important since you can always swap to a different frame. As you say, you just pick by mathematical aesthetics -- which, in this context, boil down to numerical simplicity. Use whatever codes up best.
Actually I didn't check if it was reverted or if someone went through removing all the tags. Probably doesn't make any odds either way (I can't even remember what article it was now, either, so I can't spend a pathetic evening hunting through its change-log -- which I'm ashamed to say I'd probably do).
I didn't even know about the {{unreferenced}} tag, but I suspect those would've been removed as well since I did scatter [citation needed] absolutely everywhere.
Also, I'm amazed my post got modded up and not down. I don't really understand/. sometimes...
And then someone changes it back. Unless you're unemployed and have absolutely no life you can't win; people camp on their favourite page and revert a few times. Then it gets locked down through too many reversions and they go running and crying to some admin for "arbitration" which they win because they've got a longer history on Wikipedia. This happens regardless of whether you, as a genuine expert in the field with access to relevant, well-sourced citations, are right or wrong.
Wikipedia isn't knowledge by democracy, it's knowledge by whoever can spend the most time camping.
I spent a while doing that on every article I could find. Almost every article on Wikipedia is grossly deficient in citations if you follow the regulations some nerd throws at you. So I got fed up and went to one of the more objectionable's favourite page and started adding [citation needed] after every factual statement that lacked verification. There's a shocking amount of things that are just accepted on pretty much any Wikipedia article.
I got banned for a few days for that.
I think I'm going to go back to it, actually, and see if I can get the whole IP range of my city knocked out.
I finished my degree in 2002 before laptops were regularly used in lectures, although a few people with alleged learning difficulties were quite happy to sit there and waste time on them. Since then though I've been to a lot of academic conferences and the laptops being used during seminar sessions are seriously irritating. Not just the glowing screens of people sitting on Facebook or Gmail or a news website (showing an utter contempt not just for the speaker but also the taxpayer who paid for them to attend the conference in the first place with the intention of taking part), but the endless clattering of the keys. It's surprisingly a bit less annoying (for me, at least) to *present* talks to a room of people on laptops, probably because I'm not distracted by the screens, but it still irritates me.
God knows what it'll be like when I start lecturing. I might set up an open "UNI WIRELESS" network and harvest everyone's Facebook emails and deface their profiles in protest, the rude cunts. Granted, I'll be sacked, but at least I can sell my story to the papers and get a couple of days' worth of irate howling from the red-tops.
"Oh, that's interesting. That toy model that has nothing to do with what we work on bar a couple of brief justifications and hand-waving about branes in 11D gravity implying we can work with branes in 5D gravity even though we have no dimensional reduction mechanism that we can trust that does this, is ruled out. That's interesting."
Slashdot Mirror
Precious few stars in our vicinity are going to go supernova anyway. Arcturus probably will but i don't think any of the others are anything like big enough. Sirius is the only other possibility within I think 30 light years or so, and for some reason I'm getting the dim memory of being told (at uni) it's too small. Supernovae are really not that common.
actually it needs basically dark energy. if you believe that dark energy is responsible for the acceleration of the cosmos, you are lead to believe that alcubierre solutions are viable. an enormous caveat is that you also have to believe that quantum gravitational effects won't destroy the system. you also have to believe that it's a *physical* solution; like pretty much every solution in relativity it assumes that it is the *entire* spacetime, past, present, future and all the way to spatial infinity. that's never going to be the case. even in deep interstellar space you've got an absurdly complicated mess of "solutions" coming from the various combined star systems and their planets. the spacetime around you is only locally flat; the asymptotic infinities bear only an approximate resemblence to those of flat spacetime, and the overall causal structure is very different (you'll run into a black hole along a multitude of directions, if nothing else.)
and we have no clue if you can still make something like a "warp drive" solution viable, even assuming we can harness dark energy as a source, which even assumes it exists in the first place.
so it's a tricky issue - even trickier than you say, even though such a material *is* theorised to exist.
That's entirely possible. I found it no more annoying than sudo perhaps not least because I'd been an admin on Solaris and Linux boxes at work for ages, so I knew what it meant. My Dad.... no.
err, you've only used uac on a machine where you're logged in as a user with admin rights, then. anyone who uses a machine with admin rights as default deserves what he gets, no matter what the os. using linux with admin rights by default is pretty fucking stupid, i'm sure you'd agree - let alone using *windows* with admin rights which is insanity.
if you run as a user without admin rights, windows vista uac demands an admin password. how good that implementation is i don't know - no doubt there are ways around it, i don't know. but it's an authentication screen demanding sys admin rights.
if you already run as an admin then it's your own bloody fault what happens to the computer. and unlike *nix sudo, it does demand an admin password, not your own password (at least, not hte way it's set up by default). how much a security gain potentially needing two passwords (compromised account + admin) is compared to one (compromised sudoers account) is is totally debatable, of course, but at least the way vista set uac up as default you needed an admin password if your user account wasn't admin.
so all but two paragraphs of your rant are, to be fair, based on something that's pretty much false (unless the windows box was set up by an idiot who automatically runs as admin - which i guess even you'd admit is pretty dumb even in a linux box; and at least there the windows machine still says "do you want to do this?" while when i've run as root on a linux or osx machine they've tended to trust that i'm running as root therefore i can do quite a bit without prompting) but did let you talk about "dumb, paranoid Windows users" and bask in your self-satisfied linux glory. well done, i salute you.
"Pro-Microsoft posts will lead many to brand you a 'Microsoft Astroturfer'."
which is impressive given i also said their security record is shit and the w7 kernel is stuffed with security flaws... ah well, i've never bothered karma whoring.
i gave up trying to educate people in security when about ten years back i tried to explain to my dad (who is far from an idiot with computers compared with others i know, who are far from idiots in real life) why it's a bad idea to run as an admin and why you log into your computer each time. he didn't understand. too stuck on the old single-user model he'd seen with the sinclair spectrum, dos 5, dos 6, windows 3.1, windows 95 and windows 98.
i *think* he gets it by now, but his machine is still single-user admin rights. so i despair.
I'd say I don't know who'd do anything different but then I remember my parents' W7 machine is set up as single-user, automatic login and user has rights. So UAC is just a click-through and totally pointless.
I've run Windows as a limited user ever since 2000. My experiences with Vista are by no means typical of normal people, and since I'm primarily a desktop user (plus latex plus intel fortran plus xming plus emacs) are also by no means typical of every Vista user...
wow. ok, i didn't encounter that. i did have two in a trot but it was rare enough that it didn't get in my way. mileages vary, of course.
Yes, I did, I got it before SP1. I had Ubuntu dual-booting on the machine at the same time and was running a Macbook with Tiger, followed by Leopard. (I think I had openSuSE and Arch on the machine at various points too but I defaulted to Ubuntu after a while.) I honestly didn't notice much difference (unlike the entertainment of watching mod points go up and down on that post :) ) -- at least in how annoying it was.
W7's approach of letting you set the level of UAC introduced an extra security flaw. That was really my only point... Off-topic, and so far as I know, accurate, and backed up by a totally subjective judgement on Vista's UAC vs sudo and OSX's authentication prompt.
MS *tried* to fight it (in part) by effectively adding a GUI sudo prompt into Windows Vista. A million people -- including Linux users posting on Slashdot -- immediately flew into fits of nerd rage about how annoying it was to have a GUI sudo prompt. (I never saw an issue with it myself, actually. Seemed no more irritating than going sudo on Linux or OSX's own authentication prompt. Unlike many, I actually really quite liked Vista, although I use OSX most of the time.) MS listened to their users and allowed them to scale it back in Windows 7, creating a million new security holes and causing a million people -- including Linux users posting on Slashdot, although not necessarily the same ones -- to complain about security flaws in Windows.
MS have made many stupid mistakes over their history and not least due to the ancient and creaking XP (and, even worse, the immediately-owned ME) have a history of shit security. Thing is they tried to patch it up in an easy way and people bitched and puled enough that they had to make it less secure again.
That, of course, ignores the other few million security flaws riddling the kernel. I'm just talking about the UAC here.
Ah, I think I see your issue. The quick answer is that (if you believe the big bang model, and it's extremely hard to get a CMB from other models that fits observations; Hoyle tried quite a few times and he could get a blackbody, somewhat unconvincingly, but he couldn't get the right anisotropies on it) the CMB isn't bouncing around -- we see different photons the whole time. I'll try and explain. Let's say for the sake of argument that the universe is closed because it makes our conceptual job a bit easier. The same arguments would apply to flat and open, but let's not play around with infinities if we don't have to.
So we've got a finite universe, and it's totally filled with different types of matter. Filled to the brim. Most importantly, it's got hydrogen nuclei (which I might slip up and call "baryons"; that's true, so far as it goes, but there are many more baryons than hydrogen nuclei....) and it's got photons and electrons. It also has some helium nuclei but they're relatively unimportant. These fluids are tightly entangled to one another because the universe is hot enough that the photons immediately ionise hydrogen, sending electrons flying out of the atoms and back into the plasma. This is going on *everywhere in the universe* -- in the same way that we're pretty certain that everywhere in the universe right now planets are orbiting suns.
Then the universe cools enough that photons suddenly don't have the energy to ionise hydrogen. This happens everywhere in the universe at the same "moment" (ignoring for now issues of time in general relativity, which just confuse the issue; let's instead say that it happens at the same "scale factor", which you can view as characterising how much space has expanded from a certain point, normally set as today). Then the point in the universe that would become the home of the Earth received CMB photons immediately after its formation (and was drenched in ultra-high energy gamma radiation). The universe expands, and a few years later the point the Earth will be in is receiving photons that were emitted a few years beforehand - which the expansion has stretched, cooling them down. Twenty years later, it's receiving photons that have been stretched by 20 years' worth of expansion. Each time it's receiving photons that were emitted further and further away from it at the formation of the CMB.
The same goes as the universe continues to evolve. Today, the Earth is receiving photons that were emitted when the universe grew cold enough to form hydrogen atoms - from points which were far enough away that it took more than 13 billion years for them to reach us.
This wouldn't work if the matter in the universe were all concentrated in a few points. Instead you'd have had a wash of photons that end as those from the points furthest away from us reach us. (In the jargon, it ends when the points furthest away enter our past light cone.) But that's not the big bang model, which smears the matter in the early universe out across the whole thing pretty much evenly.
If the radius of curvature of the universe was sufficiently low, we'd now be seeing photons getting to us that have done the entire circuit. The effect of that is particular patterns on the observed CMB, which haven't been seen. That's one way of constraining the size of the universe (if you assume a trivial topology) or of constraining the topology. And yes, observations will only ever directly be able to put limits on the radius of curvature; there is no way of telling from this kind of argument whether the universe is actually flat or not.
Of course, all this relies on you accepting big bang cosmology, but it does better than any conflicting theory I've ever heard of, for all the issues that crop up.
The Earth being at the centre of things is one such conflicting theory -- I don't think anyone proposing these actually wants to put the Earth at the centre of the universe, not seriously. The Copernican principle is deeply ingrained in us, hence your objection to it, I guess. I don't want
The first analogy I was taught at university is still a really good one. Imagine being at the centre of an infinite football stadium and the crowd are cheering. At one moment for whatever reason, they all stop. What do you hear? You hear the final echo coming towards you from evermore distant rows of seats. This goes on forever, just with the sound getting fainter at fainter.
The CMB is the same kind of thing. Back in the early universe when it was younger than about 370,000 years old the temperature was *way* too high for hydrogen to form, so it was a massive mess of protons, electrons and photons. (And neutrinos but the temperature by then was way too *low* for those to interact much.) Sure, electrons would combine with protons to condense into hydrogen but an absurdly high-energy photon would immediately smack it back out again. But at about 370,000 years old the universe was cold enough that suddenly there weren't high-enough energy photons around to do that (remember they have to be about 13.6eV.) So suddenly there's a "last scattering surface" formed - the photons suddenly stream free.
Effectively the CMB is just a photograph of the universe as a baby. It's not coming from the edge of the universe at all; it's all around us because it happened to the entire universe at about the same time. Of course, since then light from the CMB has propagated across the universe and been manipulated in various ways -- the most significant are the "integrated Sachs-Wolfe effect" which is what happens when light falls into a gravity well that shrinks due to cosmic expansion before it climbs back out again; the "Sunyaev-Zel'dovich effect" which is how badly galaxy clusters fuck up the light as it comes through; and "reionisation" which is when the first stars lit up, massive, powerful beasts that immediately stripped most of the hydrogen in the universe back into protons and electrons again (which then got in the way of the CMB, though mainly influencing its polarisation rather than anything else).
The smoothness of the CMB is *evidence* for a Big Bang cosmology for a couple of reasons. First, the fact we see it as so smooth -- and it is, unarguably; it's to one part in 10^4 if you wipe a Doppler effect which is normally attributed to our velocity with respect to the CMB though there are other explanations -- strongly suggests that the universe was exceptionally smooth when it formed. If you put that into general relativity you're driven pretty much uniquely to Big Bang cosmology. If instead you take an alternative approach then when you set the initial conditions for a Big Bang cosmology, normally at about the first second so you're safely away from the splittings of the forces and from nucleosynthesis (meaning you can firmly say "I have about 75% hydrogen, 25% helium and traces of everything else), one of the things you find you're required to do is to set the photons up to be totally smooth. By the time you hit the CMB that's still there because all the ripples caused by the interactions are extremely small up until the universe is much, much older.
No idea if that helps persuade you, of course.
As for topology, the CMB is a great place to look because of the propagation of the light since the formation. It's not that it maps the edge of the universe; it doesn't, at all. It's just a bath of microwaves left over from when the universe got to the right temperature. What it does do is give us hints about the paths photons have taken since. We've got very good guesses to what the ripples on the CMB look like (check out http://en.wikipedia.org/wiki/WMAP for the current state of the art, or http://en.wikipedia.org/wiki/Planck_(spacecraft) for the eagerly-awaited data) which seem very solid. So you can look for any odd changes in that coming from, for example, a donut-shaped universe. The easiest way is to look for "circles in the sky" which are a signal that the light has wrapped around and com
...what's that got to do with anything? I don't think a couple of NASA teams cocked up and splattered a probe across the face of Mars because they had an argument about what a galaxy is. Did you miss "in this context"?
Even if we follow your weird jumps of topic, it still has nothing to do with anything. What we choose to call a galaxy is a matter of nomenclature, taxonomy. Whether we use metric or Imperial measures is a choice of units. There is absolutely no comparison between them. A choice of taxonomy is ultimately a choice of how to present things to the general public. A choice of units is a choice of how to address the problem. A NASA team not saying they're using inches instead of centimetres is a sackable offense. They could have "communicated their ideas clearly" to the other teams (stretching the use of the word "idea" here) simply by writing 10" instead of 10 on their reports. They didn't. That's not the fault of any definitions and it's not even the result of working in Imperial units. It's their fault for being ham-fisted and incompetent. The ability is there to communicate clearly and has been since Imperial and metric units were first codified.
There's no comparison between the situations whatsoever.
Yes, they have. Not quite that way, but yes. The conclusion is that if the universe has a non-trivial topology, it's scale is much bigger than the current "radius of the universe" (actually much bigger than the current Hubble length) because no evidence of this kind of thing has been seen. They've tested for if the universe is spherical, which is probably closest to what you're meaning, although in that case there are many other effects that we would see extremely clearly and simply don't. They've tested for whether it's donut-shaped. They've tested for whether it's shaped like a football (as in a soccer ball). They've tested a few other weird configurations. No evidence yet, except a very slight tendency towards the universe possibly being very, very slightly spherical -- if it is, the radius of curvature is extremely large.
virialisation. there are scales beyond which objects are not viralised, which can be taken to mean they're not gravitationally bound to one another. gravitationally *influenced*, yes, but not bound. there's a clear enough definition.
or, if you like, if you're talking galaxies and clusters of galaxies, you can call them "gravitationally bound" when they detach from the hubble flow. the "hubble flow" is the expansion of the universe as a whole. when objects are close enough together, their gravitational attraction to one-another overcomes the cosmological expansion. at that point they "detach" from cosmology.
it's a loose way of saying it but a physically lucid one. a more precise way would be to say that when a perturbed robertson-walker metric (which underpins cosmology) no longer adequately describes a cluster of galaxies, that cluster has probably detached from the hubble flow. the cluster will be described by some horrific pseudo-spherical metric and not robertson-walker. to the rest of the universe it may as well now be a solid block. that's the point you could call it "gravitationally-bound".
"except in this case, it need defining so we can catalog the finds appropriately."
No it doesn't. Trust me, no it doesn't. Go and hunt out the latest SDSS data release. Do you see a million arguments and complaints that people can't quite tell whether they should include something or not in case it's a galaxy or not? No, because they don't care. It's a massive catalogue of galaxies. No-one cares what "galaxy" means; it's just a catalogue of all the luminous matter the SDSS can see.
Or let's go a bit more technical. An important subset of the Sloan are the luminous red galaxies. How are these defined? Well, for the general public, they're "luminous", "red" and "galaxies". That's all anyone actually needs to know. Defining them for the actual Sloan analysis is much tougher and is done first with a lot of cuts based on redshift (itself tricky to identify and normally done photometrically because of the sheer number of galaxies in the survey) and then cuts based on "colour" (ie luminosity in a particular frequency band). And it's much, much harder and more convoluted than it sounds, and I don't actually understand much more than this myself. Is there any point going into all of that for a press release? No, you just say "we picked out the most luminous, red galaxies from the survey". Who seriously needs anything more? No-one except other astronomers, who don't really care if they call it a "galaxy" or not because it's the science that's important and not the taxonomy. I know how sententious that sounds but unfortunately it's true, the important things are the results you get, not some petty little argument about whether this is a "luminous red galaxy" or a "fairly luminous, almost red possibly galaxy".
The same goes with every single catalogue. Back at the start of it all, Messier just made a massive list of "nebulae". These days we know some of his nebulae were what we not call nebulae, others were what we call globular clusters and others were what we call galaxies, but we still use the Messier catalogue numbers. As a rough guide, in any catalogue we need to know: redshift (or straight distance if it's near enough to get distance from, say, Cepheids), total luminosity, rotation curves if possible, morphology which is closely related to the rotation curves, stellar luminosity and mass distribution, and other things like that. We don't actually need to tag the word "galaxy" onto things, no matter how much you might want us to. It's totally unimportant.
But... in this context - and it's seriously useful to stay in context - scientists *can* effectively communicate their ideas. Clearly, too. No-one outside of astronomy gives the slightest fuck what the difference is between a large globular cluster and the smallest of dwarf spheroidals, and neither should they. I can make it clear in the context what I'm meaning by "galaxy" and the word is loose and flexible enough that it can fit what I want. The only people I've encountered who care are people who wanted to be astronomers but either didn't or couldn't get good grades on the degree. The kind of people who are in it for the pretty pictures and not the science -- basically, butterfly collectors of the heavens.
(There's nothing wrong with the pretty pictures, by the way. I got into astronomy through star-gazing and popular astronomy books, the same as anyone. Just that there's more to it than taking a photo through a camera and sticking it on some website.)
Not content with making us all look like total fuckwits with the whole debate over what makes a planet - as if it matters in the slightest - some dingus is going about kicking up a fuss about what identifies a galaxy. Seriously, who gives a toss? The important thing is the science, which doesn't change whether we call a particular virialised cluster of stars a "cluster", a "galaxy" or "peter". The taxonomy is beyond unimportant.
The only place I can see that this kind of thing has is in education (and, yes, perhaps talking with the general public). And even in that case... who cares? Who said that we have to have some serious rigorous definition for everything we say when communicating in a general manner? I can sit there and have a loose definition of the word "galaxy" that changes depending on context and not only will the journalist not notice any slight changes but *they won't care*, and neither will their readers.
Stirring up something like this, though, just makes us look like a pack of dithering idiots who don't know what we're talking about.
So far as I'm aware, the convention is simply to centre your coordinate system at the most convenient point, which depends what you're wanting to do. You can always transform to a different reference frame. It's not actually *that* important. For doing the Earth/Sun system you'd most likely just lock it to the Sun since the difference between that frame and the centre-of-momentum frame of the Earth/Sun combined is utterly negligible. For the Earth/Moon system you might put it at the centre-of-momentum frame of the two or just lock it to the Earth. For Pluto/Charon you'd use the centre-of-momentum frame because Charon's orbit would look totally weird.
Just depends what you're interested in, really, and it's not that important since you can always swap to a different frame. As you say, you just pick by mathematical aesthetics -- which, in this context, boil down to numerical simplicity. Use whatever codes up best.
Actually I didn't check if it was reverted or if someone went through removing all the tags. Probably doesn't make any odds either way (I can't even remember what article it was now, either, so I can't spend a pathetic evening hunting through its change-log -- which I'm ashamed to say I'd probably do).
I didn't even know about the {{unreferenced}} tag, but I suspect those would've been removed as well since I did scatter [citation needed] absolutely everywhere.
Also, I'm amazed my post got modded up and not down. I don't really understand /. sometimes...
And then someone changes it back. Unless you're unemployed and have absolutely no life you can't win; people camp on their favourite page and revert a few times. Then it gets locked down through too many reversions and they go running and crying to some admin for "arbitration" which they win because they've got a longer history on Wikipedia. This happens regardless of whether you, as a genuine expert in the field with access to relevant, well-sourced citations, are right or wrong.
Wikipedia isn't knowledge by democracy, it's knowledge by whoever can spend the most time camping.
I spent a while doing that on every article I could find. Almost every article on Wikipedia is grossly deficient in citations if you follow the regulations some nerd throws at you. So I got fed up and went to one of the more objectionable's favourite page and started adding [citation needed] after every factual statement that lacked verification. There's a shocking amount of things that are just accepted on pretty much any Wikipedia article.
I got banned for a few days for that.
I think I'm going to go back to it, actually, and see if I can get the whole IP range of my city knocked out.
No.
Good luck teaching that to the world. I'm losing count of how many times I see that mistake made, and not always by non-native speakers.
I finished my degree in 2002 before laptops were regularly used in lectures, although a few people with alleged learning difficulties were quite happy to sit there and waste time on them. Since then though I've been to a lot of academic conferences and the laptops being used during seminar sessions are seriously irritating. Not just the glowing screens of people sitting on Facebook or Gmail or a news website (showing an utter contempt not just for the speaker but also the taxpayer who paid for them to attend the conference in the first place with the intention of taking part), but the endless clattering of the keys. It's surprisingly a bit less annoying (for me, at least) to *present* talks to a room of people on laptops, probably because I'm not distracted by the screens, but it still irritates me.
God knows what it'll be like when I start lecturing. I might set up an open "UNI WIRELESS" network and harvest everyone's Facebook emails and deface their profiles in protest, the rude cunts. Granted, I'll be sacked, but at least I can sell my story to the papers and get a couple of days' worth of irate howling from the red-tops.
"Oh, that's interesting. That toy model that has nothing to do with what we work on bar a couple of brief justifications and hand-waving about branes in 11D gravity implying we can work with branes in 5D gravity even though we have no dimensional reduction mechanism that we can trust that does this, is ruled out. That's interesting."