Yeah, this reminded me of how much fun I had playing Netrek once upon a time.
So, just to see if anyone's still playing Netrek today, I immediately followed the link in the FA, went to netrek.org, and downloaded what their webpage had as the latest Linux client. Attempting to run it, I got "sorry, but this client has expired; you need to download a current one from ftp.netrek.org." I guess that's a clue as to the vitality of the community . . . .
This makes no sense, since ultimately *all* device access is in the kernel. It's OS design 101.
No, it makes perfect sense -- it's just confusing because of an odd use of terminology (at least as compared to Windows).
When people complain about printer drivers under Linux, they're not talking about kernel modules -- what most of us would think of as "drivers" in the traditional sense. Linux already has USB/parallel port/whatever kernel modules that handle everything related to the communication with the device. The complaint is in the "device-specific-properties" end; since the USB/parallel port/whatever kernel modules are generic, handling only the lowest layers of how communications on the bus takes place, they don't know anything about the type of data the device expects.
To make a useful-but-not-quite-right analogy, your network interface card knows about how to send 1s and 0s over the net; but it doesn't know anything about what kind of sequences of 1s and 0s will make sense to anything on the other end. Instead, you've got software layers above it that are responsible for taking a bunch of outgoing data and cutting it up into an ordered sequence of chunks wrapped in headers to allow re-assembly (the TCP part), then wrapping them in shipping headers so they'll reach their destination (the IP part), before sending them to the NIC. But even those software layers don't know that the device on the other end will be passing this data to a web browser; so the chunk of data being sent better look like sensible HTML. That's taken care of by other layers of software in user space.
In Linux, kernel modules handle the communication with the device; but they don't know (and don't care) what form the device is expecting the data to be in. For printers, that's handled by a separate "filter" layer that comes before the kernel modules do their work. The filter layer is typically some sort of translation program that runs in userspace, takes a stream of data as input (from a file, from another program, or whatever), and encodes it into some other form and/or breaks it into chunks and/or wraps it in headers. The "encoding into some other form" would include putting in the stuff that exploits specific printer features. It's these filters which are sometimes missing or feature-incomplete in Linux, and are what people refer to when they talk about printer drivers.
You don't get it. They're kernel developers, and they're asking about kernel modules, which are an entirely different type of thing from userspace drivers. They're asking for suggestions on what devices that need kernel modules to work are unsupported. Telling them to work on printer drivers is like responding to water company employees who've rehabilitated all the water mains and are asking what other water-system related work needs doing with "why don't you fix the town electrical grid?" They're working on what they know how to work on; and they're asking "within the domain of this stuff that we know how to work on, what still needs doing?"
One thing you did NOT mention is that WN does not communicate with other airlines. If your flight is delayed 7 hrs, you do not have the option to fly the United flight that leaves in 1 hr and has open seats... unless you want to pay for a second ticket on United, that is!
Fortunately, since you never end up delayed 7 hours on Southwest -- that only happens with airlines like United -- this issue doesn't arise.
Of course, now you're going to give me some one-of-a-kind horror story to the contrary. But I've flown a lot, a huge honking lot, including lots of trips on AA, UAL, US Air, and Southwest. With AA I've experienced bad delays, and with UAL and US Air I've had horrific experiences. With one exception -- getting grounded in Chicago by a snowstorm that shut down Midway and every airline there -- I haven't had a single > 10 minute delay with Southwest. Never. Not one.
I agree, and frankly I'd be glad as hell to start hearing about some head honcho guys getting picked off by snipers, or whatever. I'm not even fucking joking. I am getting REALLY SICK of hearing about peoples' lives being totally fucked up because they downloaded some music and left Kazaa running while they were sleeping, or whatever.
Comments like these might make some kind of sense if we were talking about evil corporations treating us badly because we're trying to breathe, or eat, or something like that. Instead, we're talking about downloading music, and making it available for others to download -- music that's not too hard to obtain by legal means, while at the same time plenty of music that's not similarly encumbered with restrictions is easily available. Are you honestly telling me that you're completely incapable of surviving without a copy of that new Coldplay song? Because otherwise, the whole "rise up violently against the evil corporations" stuff seems beyond the valley of the shadow of absurd. It's like getting mad at your parents and throwing stuff around the house because they wouldn't give you a cookie.
Hey Mr. B, what's the status of actually relating the T-F/F-J (or whatever the unified relation is to be called now) to galaxy formation?
It's been 5 1/2 years since I left extragalactic astronomy to become a hermit; but my last memory was that we hadn't gone very far in explaining the slope of the relation. Obviously it's steeper than one expects with a constant mass-to-light ratio and simple gravity (especially the Faber-Jackson relation, if you take stellar velocity dispersion on face value, which I guess this work and Ben's previous work would argue not to do). A mass-dependent (M/L) isn't at all surprising, and simulations of galaxy formation in a cosmological context (e.g. Evrard, Summers and Davis; Hernquist and Katz; etc.) did indeed predict as such -- but not with a slope sufficient to explain the T-F relation. They got close, but not quite there. That's how things stood five and a half years ago; is this no longer true? Do we understand the origin of the relation now?
There's a lesson to be learned -- when you share your information, expect others to take advantage of it if they can find a way to make a gain that doesn't hurt you.
The part in bold is the part you're not getting.
The information that you submitted is probably still there in FreeDB, or was perfected by someone else. It doesn't go away.
Actually, some did. A lot of user-contributed content had to be replaced as a result, and it's not clear that all of it ever has been.
Re:I'd rather have some NICs, soundcards, etc.
on
Quad PCIe Motherboard
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· Score: 1
Why would a soundcard need a 16 lane PCI-e slot? How many channels of sound are you sampling anyway?
16, at 96 or even 192 kHz. People who do serious audio work do it with cards requiring a lot more than consumer soundcards like the latest offering from Creative.
WTF are you people buying that you don't want traced?
Donating money to an out-of-power political party? Or to an environmental group, or a group that opposes religious influence on science education in schools? Going to a gay club? Any one of a zillion other things that the dominant political party, or its religious/corporate backers, would rather you not do?
I don't think that people are afraid of getting spotted doing something illegal. I think a lot of people are concerned over a perceived erosion of rights in the U.S. (cf. the outcry over everything from the USA PATRIOT act to the DMCA). Whatever you may think of that concern -- whether you think worry over declining rights is valid or a load of hooey -- there is bound to be much more worry if you are concerned about it, and simultaneously are looking at a decline in personal privacy.
"observation that clusters of galaxies had to have a lot of mass not shining in the visible spectrum in order to be bound objects"
What is the problem here? Does an Oort cloud 'shine'? If the interstellar spaces were crowded with planet-sized bodies, would these 'shine'? Can't this 'missing matter' merely be rocky or icy crud between the stars? I've often suspected that interstellar navigation might be *extremely* dangerous due to such obsticals, but wouldn't they count as 'dark matter'?
Certainly rocks and ice would count as dark matter. The trick is figuring out how to put a large fraction of the baryonic mass of the Universe in that form. That's effectively impossible given what we think we know about star formation, galaxy formation and the history of both. Furthermore, we have now (by a variety of techniques) mapped out the way in which the overall mass (and thus the dark matter, since it dominates the mass) is physically distributed in galaxies and clusters; on both scales, it's nothing at all like you'd expect the rocky/icy matter left over from disks around young stars and so forth to be distributed.
"One of the observational lynchpins of the model is its set of predictions for light element abundances."
So is this setting a limit on how 'crowded with crap' the interstellar medium could be? And if we discover that its thicker than this, then relativity is in trouble?
Big Bang Nucleosynthesis sets a limit on how much baryonic matter there can be in the Universe. That limit is in turn consistent with the prediction for the same quantity made from observations of signatures of density fluctuations in the early Universe left in the cosmic microwave background radiation. If it turned out that there was more baryonic matter around than these constraints allow, enough to explain away all dark matter, then that would be a problem for the Big Bang model. There's no evidence of this, however. People have put a lot of effort into detecting various types of baryonic dark matter, with some amount of success; but the quantities involved don't come close to solving the dark matter problem. And it's hard to imagine a physically plausible theory and history of star formation which would allow it.
"it was discovered that the space between galaxies in clusters is filled with a 10-100 million degree gas (well, plasma) known as the intracluster medium or ICM"
Ok so suppose one were in a spacecraft in one of these clouds of 'plasma' and one stuck a thermometer out of the hull, would it *really* show such a high temperature? Would it not be a cold 'vacuum' out there... even thinner and colder than the 'vacuum' of our own solar system?
Or is the high temperature somehow taken as an aggregate temperature for a large volume of space with small quantities of gas particles or ions whizzing about at extremely high speed and therefore the point temperature at any given location in that cloud would actually be quite low?
I'm not sure what you mean by a "cold vacuum," and your comments about temperature don't make sense to me.
Temperature is, by physical definition, a measure of the average kinetic energy of the particles involved. The intracluster medium has 10-100 million degree temperatures ascribed to it because the measures of the kinetic energy of its particles show that it has that much energy. Your thermometer might not show such a temperature, because thermometers work by exchanging heat with the surroundings until they come to thermodynamic equilibrium together; that wouldn't happen for a thermometer stuck into the intracluster medium for a little while since the interaction rate would be pretty low. But the ions and free electrons that make up the intracluster medium really are whizzing around that fast.
We observe the intracluster medium in the X-ray band. An analysis of the energy spectrum of the X-rays emitted shows it to be mainly thermal bremsstrahlung radiation, and from the
This begs one to ask, if we keep finding these galaxies that are emitting energy but no light, is this dark matter or is it just normal matter that we just haven't been able to find yet? There might be a hell of a lot more dust out there than we thought there was originally.
Certainly some of the dark matter is in baryonic (i.e. normal) matter. In fact, it's interesting to note that the the first "missing matter" found was baryonic. While the rotation curves of spiral galaxies provide the most clear-cut evidence for missing matter at present, the history of the dark matter problem started much earlier, with Fritz Zwicky's observation that clusters of galaxies had to have a lot of mass not shining in the visible spectrum in order to be bound objects; their galaxies were moving too fast for clusters to be gravitationally bound objects otherwise. Then, starting in the 1960s, a significant fraction of that dark matter was found when it was discovered that the space between galaxies in clusters is filled with a 10-100 million degree gas (well, plasma) known as the intracluster medium or ICM. In very large clusters, the ICM can have several times as much mass as the mass of all the cluster galaxies. That was a good sized chunk of the missing matter on cluster scales, right there.
However, despite that, it still left most of the apparent mass of galaxy clusters unaccounted-for, a situation that remains today. And that's been the same story with pretty much all the dim or dark baryonic matter we've found since then: it's crucial to know about, since it has important things to tell us about the evolution of the Universe, the history of galaxy formation, etc., but it doesn't make a big impact on the dark matter problem. Our measurements of the compnents of the density of the Universe are at low redshift, and we don't know what the low-redshift counterparts of these high-redshift ultraluminous IR galaxies are. But if they turn out to be something we haven't yet detected, and thus it turns out we've underestimated the number of low-redshift galaxies by a factor of three (very doubtful), that still won't put an appreciable dent in the dark matter problem. There's just so much dark matter out there to find, compared to the amount of known baryonic matter.
Finally, it's worth noting that if baryonic matter were able to explain away all the dark matter, that would actually pose a serious problem for the standard relativistic hot big bang model. One of the observational lynchpins of the model is its set of predictions for light element abundances. We think we know all the relevant physics at the energies of nuclear processes; that, combined with the evolution of the background Universe as dictated by the Big Bang model, allows one to calculate the abundances of light elements. It turns out that the theory of Big Bang Nucleosynthesis is able to make pretty good predictions for the abundances of hydrogen, helium, lithium, etc., provided the density of the Universe in baryons is within a small range. The predicted values are significantly larger than the contribution to the mass density of the Universe from the luminous matter in galaxies, so we already expected that that there would be some baryonic dark matter. But the predicted values are also much much much smaller than the apparent density of the Universe in dark matter. In other worse, if Big Bang Nucleosynthesis is correct, you expect there to be baryonic dark matter, but you also expect much much more non-baryonic dark matter. Of course, that doesn't mean that all the dark matter isn't baryonic -- nature is under no obligation to follow our theories! -- but the theory's done reasonably well up to know, so it's worth remembering and is a reminder to be careful.
Gates also contributes a lot of money to charity. One might think that doesn't mean much since he's the richest guy in the world. I say to them, alright, you donate the same percentage of your wealth to the poor.
This is a silly argument. Someone who makes a million dollars a year finds it much easier to donate half their income to charity than someone who makes $40,000 a year. For Bill Gates, this is even more true. He could donate 99% of his income and live more comfortably than the vast majority of Americans; in contrast, very few people in the U.S. could donate 99% of their income to charity and still make enough money per year to stave off homelessness.
Note that I'm not saying that Bill Gates is stingy; that's not my point. I'm merely saying that your argument is absurd.
I tried FlightGear last week (under Windows) and it was awful! My machine is no super computer (3.2Ghz P4 and a Ge4600Ti) but I expected more than 2-8fps.
I would expect it too. Most FlightGear Windows users get framerates comparable to what the Linux users get; and your framerates are well below what they should be. I have a comparable or slightly less powerful machine than yours (XP2000+, GF4 Ti4600) and typically get framerates that are an order of magnitude higher than what you're getting (it depends, of course, on the plane, the area, etc.). So something's wrong on your end. Apart from all the usual "check your driver" crap -- I don't think that's it, you've said FS2004 runs well, but it doesn't hurt to make sure -- I'd check the default configuration for FG. People who have complained of absurdly low FlightGear framerates in Windows in the past have often turned out to have FG configuration issues like their visibility turned up to an absurdly high range (e.g. 200km, causing FG to have to worry about all ground structures within 200km, which takes a lot of memory, which causes thrashing, which slows down the machine).
I'd also check your version; old versions of FG and the libraries on which it's based (especially plib) were much less powerful than the current. If you still can't solve the problem, and you're feeling helpful, please do subscribe to the
flightgear-users or flightgear-devel mailing list and post your problem. Your framerates are abnormally low, and if the problem really is with FlightGear rather than with your setup, then the FlightGear developers would certainly like to get it fixed.
By comparison MS Flight Sim 2004 runs smoothly and looks great
No argument. FS2004 is a great piece of work. I have some knocks on it, but they're mostly because it's not fundamentally the software I'd want it to be, rather than what it is (see below). Compared to its goals, it's fabulous.
- as well as having well regarded flight dynamics,
This is one thing I'd take a bit of exception to. Among real-world pilots who have moved to FG from MSFS, including FS2004, the most common complaint about MSFS has been the realism of the flight dynamics modelling. Among non-pilots who try FG after MSFS, the most common "complaint" by a wide margin has been "the Cessna keeps pulling to the left as I go down the runway and try to take off! FlightGear has a bug!" -- which is, in fact, not a bug.
That's not to say that the modelling of flight dynamics in FlightGear has no problems -- it does. But on the whole, I'd pick it over MSFS. A large fraction of the core FlightGear developers are aero engineering types (some with Boeing and NASA), so it's no surprise that this is where it'd do best. On the other hand . . .
a excellent weather modelling
Yes, here's an area that FG really lacks. It draws clouds well as scenery; but flying through/among the clouds isn't done well. And all the rest of weather -- rain, snow, icing, etc. -- is really nonexistent, and these are important things, especially for pilots. It's not like the FG developers aren't aware of this, and this is an area where slow, halting steps are
finally being taken.
and a pretty comprehensive ATC system.
This, too, is an area where FG lacks; but it's an area of current development, even more than the weather issues, if I'm following people's conversations correctly.
The problem is that producing a game requires much more focus and many more resources than 99.9% of OS projects have access to. What's really needed is a high quality, high level OS game engine. Something that hides all the OpenGL/SDL details, that's easy for programmers to pick and use, that's easy extensible, that's cross platform, that builds with multiple compilers and that doesn't require hundreds of lines of code just to initalise.
I'm sure you know this, but what's needed from a g
Dark matter isn't mysterious or unordinary. Dark matter is usually extremely cold but otherwise ordinary matter. Because it's so cold, it can't emit light, hence "dark" matter. So, while they did discover dark matter in the sense that most astrophysicists use the term, they did not discover the really weird stuff.
You have, however, picked up on an important distinction. They found dark matter, but what they really need to find is dark energy. Dark energy is thought to comprise something like 70% of the energy of the universe, and yet, even today, it is a complete mystery.
I dunno whether you're confused about this stuff, but your post makes some statements which are at least confusing, and possibly wrong, depending on what you meant (I can't really tell). So to clarify, for anyone who cares: the energy content of the Universe appears to have three components:
visible baryonic matter (about 2% of the total);
dark matter, of which a small fraction is expected to be nonluminous baryonic matter (about another 2% of the total), and the majority of which is expected to be (hypothesized but not yet discovered) non-baryonic matter (about 23% of the total);
the absolutely horribly named "dark energy", which from a particle physics perspective can be thought of as a vacuum energy density, and from a General Relativity/Friedmann Equations point of view can be thought of as a cosmological constant (about 73% of the total).
I have no idea whether you're still reading, it being two days later. But I just noticed your reply, so I'll go ahead and respond. But the first thing I need to say is that again, your response is replete with comments that indicate that you don't really understand what the Big Bang model is and is not, and in particular the difference between the Big Bang model and the standard cosmological model as a whole (of which the Big Bang model is but a component). Quantum fluctuations of the vacuum, for instance, are an important component of the standard cosmological model, but have absolutely nothing to do with the Big Bang model. It's sorta like the difference between "physics" and "thermodynamics." Ohm's Law is a part of physics; it is not a part of thermodynamics, even though thermodynamics are a component of physics. The scope of the Big Bang model -- what it describes, explains, and predicts -- is only a segment of the larger standard cosmological model. There are many uncertainties in the standard cosmological model, and some of its parts are doubtless wrong. However, that component of it that relates the large-scale evolution of space to the energy content of the Universe, that we refer to as "the Big Bang model," is on pretty sturdy ground.
You're absolutely right that an accelerating universe doesn't disprove a Big Bang; I thought about that right after I posted. I'm not sure why I threw that in.. I was thinking about what initial conditions of the Big Bang we can try to deduce from observational data. An accelerating universe does however, make us step back, and consider that there must be "more to it" than a big explosion acted on merely by gravity.
And already we're into trouble. I really don't mean anything personal by this, I promise. But your lack of understanding of what the Big Bang model is, explains, and predicts, is illustrated by the last sentence you've written here.
The Big Bang model does not involve "a big explosion" of any kind. Qualitatively, the Big Bang model posits that a long time ago, the contents of the Universe were everywhere very hot and very dense, and that since then, space has been expanding and those contents have been cooling because of that expansion. That's it. That's all. Note that I didn't say anything at all about a singularity, or the beginning of time, or stuff exploding out from a point, or anything like that; none of these are part of the Big Bang model. It is true that by blindly extrapolating the Big Bang equations of evolution (the Friedmann equations) backwards, one arrives at a spacetime singularity; but we have no idea whether it's valid to do that, since in doing so one necessarily speaks of times when the average energy of the stuff in the Universe is higher than reached in any experiment humans have ever done (up to infinitely high energies as one approaches the putative singularity). We don't know what the physics of the Universe was like at temperatures higher than about 1 TeV (about 10^16 degrees). We have theories, but we have no idea whether those theories are correct, because no one has been able to do experiments that can test or falsify them. All we can talk about is the domain over which we understand the physics. From that, we argue that the Universe was once very very dense and hot, and it's been expanding and cooling ever since.
If you believe that as you look at larger and larger scales, the mass/energy distribution in the Universe converges towards homogeneity and isotropy, and if you believe that general relativity is an accurate description of the behavior of gravity on large scales, you're stuck with the Big Bang model: those two assumptions require the Big Bang model. The first of those two facts tells you something important about the structure of space on large scales (i.e. that it can be described by the so-called Robertson-Walker metric); the second gives you a set of equations that related the structure of space, and its evolution, to the mass/energy content of the Universe.
One is the red shift... everything is accelerating away from us. I've heard the 'raisins in bread' theory, that everything just gets farther from everything else. I can understand that... but that would mean uniform continued expansion, and it would also mean that the universe had a dead-center. Being outside that center, things should be accelerating at different rates relative to earth.
Another problem is the age of the universe as determined by looking deep into space and saying "ah, theres the edge! and if we look in the opposite direction at the same deep distance there it is again! the edge of the universe! the universe must be N billion years old." Uniformity as described in the parent post would put earth at the dead center if the universe were expanding and we really were looking at the edge of it.
Once again, as a previous poster suggested, you really need to take the time to learn about physical cosmology before exclaiming that "parts of the Big Bang theory . ..just don't make sense." You're right that the things you say in your paragraphs above don't make sense; where you're wrong is in your belief that these are in some way part of the Big Bang model. You don't understand what the model says. You are asserting what you think it says -- assertions that are wrong -- and then pointing out absurdities about those assertions. But what you're saying is irrelevant since the Big Bang model isn't like that.
It is perhaps the best CURRENT explanation. But it is not as good a theory as it was even a few years ago. There are questions that the Big Bang theory has no explanation for.
Sigh.
Before going any further into your post, it's important to to remember that there is an enormous difference between the (Relativistic Hot) Big Bang model, and the standard cosmological model (of which the Big Bang model is a component). There is more to the standard cosmological model than just the Big Bang model, which really only describes the evolution of the spatial scale factor and the dynamics of the fluids contained in space. This is an important point: all three of the "issues" you reference (flatness, the acceleration of the expansion, and the so-called horizon problem) are not problems with the Big Bang. Well, the middle one (the accelerating expansion) isn't a problem at all, of any sort, and someone who suggests it is doesn't understand physical cosmology. The other two may indeed turn out to be problems for the standard cosmological model, but most emphatically are not problems with the Big Bang model, since they lay outside its domain.
It's a bit like suggesting that there must be something wrong with the round-Earth model because it doesn't explain why we get tornados. It's not part of the domain of applicability of the Big Bang model to answer the question of why the flatness and horizon problems exist. OTOH, our overall model of cosmology had better explain the flatness and horizon problems. If it doesn't, and is superseded by something else, that something else will almost certainly contain within it a description of the dynamics of the expansion that looks just like the Big Bang model.
As for your statement that the Big Bang model "does not explain the increasing evidence that the expansion of the universe is actually accelerating" . ..this is a bizarre statement, since it seems to suggest that the Big Bang model somehow predicts or requires that the expansion of the Universe not be accelerating. This is not true. Under the Big Bang model, the dynamics of the expansion are determined by a set of properties of the Universe (e.g. the density of the Universe in normal matter, the density of the Universe in relativistic fluids such as photons, the vacuum energy density of the Universe, etc.). The Big Bang model does not make predictions about the values of these parameters; it merely provides a mathematical framework that allows you to deduce "if these are their values, then this is what will happen." Non-zero cosmological constant models with accelerating expansion are not only permissable under the Big Bang model, but have been actively considered by theorists in different contexts for a very long time, since long before Bob Kirshner and Saul Perlmutter's research groups started turning out their data on the high-z Hubble diagram using Type Ia supernmova data. In fact, if you were to ask Kirshner or Perlmutter or Adam Riess or Brian Schmidt or anyone else associated with these projects, they'd tell you that one of the neat things about their evidence of acceleration is that they place constraints (which are non-zero) on the vacuum energy density of the Universe; those constraints come from the Big Bang model.
Your statement about fine-tuning in the context of the flatness problem is a little off. What would have been more disturbing to cosmologists is if the Universe were not flat, but were near flat. A Universe which is flat at early times stays flat; a Universe which is even slightly positively or negatively curved is driven away from flatness very very quickly. This was the fine-tuning problem that worried cosmologists before the BoomerANG and MAP results -- data seemed to suggest that the Universe was only slightly negatively curved, which in turn implied at very early times a Universe infinitely close to flat but not flat. There are a variety of physical theories out there to explain why the Universe would be flat; to explain w
Slashdot Mirror
The abstract refers to card games as an example of its applicability. The actual text of the patent is more expansive.
Yeah, this reminded me of how much fun I had playing Netrek once upon a time.
So, just to see if anyone's still playing Netrek today, I immediately followed the link in the FA, went to netrek.org, and downloaded what their webpage had as the latest Linux client. Attempting to run it, I got "sorry, but this client has expired; you need to download a current one from ftp.netrek.org." I guess that's a clue as to the vitality of the community . . . .
Slashdot covered this story back in June.
No, it makes perfect sense -- it's just confusing because of an odd use of terminology (at least as compared to Windows).
When people complain about printer drivers under Linux, they're not talking about kernel modules -- what most of us would think of as "drivers" in the traditional sense. Linux already has USB/parallel port/whatever kernel modules that handle everything related to the communication with the device. The complaint is in the "device-specific-properties" end; since the USB/parallel port/whatever kernel modules are generic, handling only the lowest layers of how communications on the bus takes place, they don't know anything about the type of data the device expects.
To make a useful-but-not-quite-right analogy, your network interface card knows about how to send 1s and 0s over the net; but it doesn't know anything about what kind of sequences of 1s and 0s will make sense to anything on the other end. Instead, you've got software layers above it that are responsible for taking a bunch of outgoing data and cutting it up into an ordered sequence of chunks wrapped in headers to allow re-assembly (the TCP part), then wrapping them in shipping headers so they'll reach their destination (the IP part), before sending them to the NIC. But even those software layers don't know that the device on the other end will be passing this data to a web browser; so the chunk of data being sent better look like sensible HTML. That's taken care of by other layers of software in user space.
In Linux, kernel modules handle the communication with the device; but they don't know (and don't care) what form the device is expecting the data to be in. For printers, that's handled by a separate "filter" layer that comes before the kernel modules do their work. The filter layer is typically some sort of translation program that runs in userspace, takes a stream of data as input (from a file, from another program, or whatever), and encodes it into some other form and/or breaks it into chunks and/or wraps it in headers. The "encoding into some other form" would include putting in the stuff that exploits specific printer features. It's these filters which are sometimes missing or feature-incomplete in Linux, and are what people refer to when they talk about printer drivers.
You don't get it. They're kernel developers, and they're asking about kernel modules, which are an entirely different type of thing from userspace drivers. They're asking for suggestions on what devices that need kernel modules to work are unsupported. Telling them to work on printer drivers is like responding to water company employees who've rehabilitated all the water mains and are asking what other water-system related work needs doing with "why don't you fix the town electrical grid?" They're working on what they know how to work on; and they're asking "within the domain of this stuff that we know how to work on, what still needs doing?"
It's been all downhill since Hunt the Wumpus.
Fortunately, since you never end up delayed 7 hours on Southwest -- that only happens with airlines like United -- this issue doesn't arise.
Of course, now you're going to give me some one-of-a-kind horror story to the contrary. But I've flown a lot, a huge honking lot, including lots of trips on AA, UAL, US Air, and Southwest. With AA I've experienced bad delays, and with UAL and US Air I've had horrific experiences. With one exception -- getting grounded in Chicago by a snowstorm that shut down Midway and every airline there -- I haven't had a single > 10 minute delay with Southwest. Never. Not one.
I agree, and frankly I'd be glad as hell to start hearing about some head honcho guys getting picked off by snipers, or whatever. I'm not even fucking joking. I am getting REALLY SICK of hearing about peoples' lives being totally fucked up because they downloaded some music and left Kazaa running while they were sleeping, or whatever.
Comments like these might make some kind of sense if we were talking about evil corporations treating us badly because we're trying to breathe, or eat, or something like that. Instead, we're talking about downloading music, and making it available for others to download -- music that's not too hard to obtain by legal means, while at the same time plenty of music that's not similarly encumbered with restrictions is easily available. Are you honestly telling me that you're completely incapable of surviving without a copy of that new Coldplay song? Because otherwise, the whole "rise up violently against the evil corporations" stuff seems beyond the valley of the shadow of absurd. It's like getting mad at your parents and throwing stuff around the house because they wouldn't give you a cookie.
Hey Mr. B, what's the status of actually relating the T-F/F-J (or whatever the unified relation is to be called now) to galaxy formation? It's been 5 1/2 years since I left extragalactic astronomy to become a hermit; but my last memory was that we hadn't gone very far in explaining the slope of the relation. Obviously it's steeper than one expects with a constant mass-to-light ratio and simple gravity (especially the Faber-Jackson relation, if you take stellar velocity dispersion on face value, which I guess this work and Ben's previous work would argue not to do). A mass-dependent (M/L) isn't at all surprising, and simulations of galaxy formation in a cosmological context (e.g. Evrard, Summers and Davis; Hernquist and Katz; etc.) did indeed predict as such -- but not with a slope sufficient to explain the T-F relation. They got close, but not quite there. That's how things stood five and a half years ago; is this no longer true? Do we understand the origin of the relation now?
Pong.
The part in bold is the part you're not getting.
The information that you submitted is probably still there in FreeDB, or was perfected by someone else. It doesn't go away.
Actually, some did. A lot of user-contributed content had to be replaced as a result, and it's not clear that all of it ever has been.
16, at 96 or even 192 kHz. People who do serious audio work do it with cards requiring a lot more than consumer soundcards like the latest offering from Creative.
This has nothing to do with galaxy clusters; it's a cluster of stars in our own Milky Way.
Donating money to an out-of-power political party? Or to an environmental group, or a group that opposes religious influence on science education in schools? Going to a gay club? Any one of a zillion other things that the dominant political party, or its religious/corporate backers, would rather you not do?
I don't think that people are afraid of getting spotted doing something illegal. I think a lot of people are concerned over a perceived erosion of rights in the U.S. (cf. the outcry over everything from the USA PATRIOT act to the DMCA). Whatever you may think of that concern -- whether you think worry over declining rights is valid or a load of hooey -- there is bound to be much more worry if you are concerned about it, and simultaneously are looking at a decline in personal privacy.
"observation that clusters of galaxies had to have a lot of mass not shining in the visible spectrum in order to be bound objects"
What is the problem here? Does an Oort cloud 'shine'? If the interstellar spaces were crowded with planet-sized bodies, would these 'shine'? Can't this 'missing matter' merely be rocky or icy crud between the stars? I've often suspected that interstellar navigation might be *extremely* dangerous due to such obsticals, but wouldn't they count as 'dark matter'?
Certainly rocks and ice would count as dark matter. The trick is figuring out how to put a large fraction of the baryonic mass of the Universe in that form. That's effectively impossible given what we think we know about star formation, galaxy formation and the history of both. Furthermore, we have now (by a variety of techniques) mapped out the way in which the overall mass (and thus the dark matter, since it dominates the mass) is physically distributed in galaxies and clusters; on both scales, it's nothing at all like you'd expect the rocky/icy matter left over from disks around young stars and so forth to be distributed.
"One of the observational lynchpins of the model is its set of predictions for light element abundances."
So is this setting a limit on how 'crowded with crap' the interstellar medium could be? And if we discover that its thicker than this, then relativity is in trouble?
Big Bang Nucleosynthesis sets a limit on how much baryonic matter there can be in the Universe. That limit is in turn consistent with the prediction for the same quantity made from observations of signatures of density fluctuations in the early Universe left in the cosmic microwave background radiation. If it turned out that there was more baryonic matter around than these constraints allow, enough to explain away all dark matter, then that would be a problem for the Big Bang model. There's no evidence of this, however. People have put a lot of effort into detecting various types of baryonic dark matter, with some amount of success; but the quantities involved don't come close to solving the dark matter problem. And it's hard to imagine a physically plausible theory and history of star formation which would allow it.
"it was discovered that the space between galaxies in clusters is filled with a 10-100 million degree gas (well, plasma) known as the intracluster medium or ICM"
Ok so suppose one were in a spacecraft in one of these clouds of 'plasma' and one stuck a thermometer out of the hull, would it *really* show such a high temperature? Would it not be a cold 'vacuum' out there... even thinner and colder than the 'vacuum' of our own solar system?
Or is the high temperature somehow taken as an aggregate temperature for a large volume of space with small quantities of gas particles or ions whizzing about at extremely high speed and therefore the point temperature at any given location in that cloud would actually be quite low?
I'm not sure what you mean by a "cold vacuum," and your comments about temperature don't make sense to me.
Temperature is, by physical definition, a measure of the average kinetic energy of the particles involved. The intracluster medium has 10-100 million degree temperatures ascribed to it because the measures of the kinetic energy of its particles show that it has that much energy. Your thermometer might not show such a temperature, because thermometers work by exchanging heat with the surroundings until they come to thermodynamic equilibrium together; that wouldn't happen for a thermometer stuck into the intracluster medium for a little while since the interaction rate would be pretty low. But the ions and free electrons that make up the intracluster medium really are whizzing around that fast.
We observe the intracluster medium in the X-ray band. An analysis of the energy spectrum of the X-rays emitted shows it to be mainly thermal bremsstrahlung radiation, and from the
This begs one to ask, if we keep finding these galaxies that are emitting energy but no light, is this dark matter or is it just normal matter that we just haven't been able to find yet? There might be a hell of a lot more dust out there than we thought there was originally.
Certainly some of the dark matter is in baryonic (i.e. normal) matter. In fact, it's interesting to note that the the first "missing matter" found was baryonic. While the rotation curves of spiral galaxies provide the most clear-cut evidence for missing matter at present, the history of the dark matter problem started much earlier, with Fritz Zwicky's observation that clusters of galaxies had to have a lot of mass not shining in the visible spectrum in order to be bound objects; their galaxies were moving too fast for clusters to be gravitationally bound objects otherwise. Then, starting in the 1960s, a significant fraction of that dark matter was found when it was discovered that the space between galaxies in clusters is filled with a 10-100 million degree gas (well, plasma) known as the intracluster medium or ICM. In very large clusters, the ICM can have several times as much mass as the mass of all the cluster galaxies. That was a good sized chunk of the missing matter on cluster scales, right there.
However, despite that, it still left most of the apparent mass of galaxy clusters unaccounted-for, a situation that remains today. And that's been the same story with pretty much all the dim or dark baryonic matter we've found since then: it's crucial to know about, since it has important things to tell us about the evolution of the Universe, the history of galaxy formation, etc., but it doesn't make a big impact on the dark matter problem. Our measurements of the compnents of the density of the Universe are at low redshift, and we don't know what the low-redshift counterparts of these high-redshift ultraluminous IR galaxies are. But if they turn out to be something we haven't yet detected, and thus it turns out we've underestimated the number of low-redshift galaxies by a factor of three (very doubtful), that still won't put an appreciable dent in the dark matter problem. There's just so much dark matter out there to find, compared to the amount of known baryonic matter.
Finally, it's worth noting that if baryonic matter were able to explain away all the dark matter, that would actually pose a serious problem for the standard relativistic hot big bang model. One of the observational lynchpins of the model is its set of predictions for light element abundances. We think we know all the relevant physics at the energies of nuclear processes; that, combined with the evolution of the background Universe as dictated by the Big Bang model, allows one to calculate the abundances of light elements. It turns out that the theory of Big Bang Nucleosynthesis is able to make pretty good predictions for the abundances of hydrogen, helium, lithium, etc., provided the density of the Universe in baryons is within a small range. The predicted values are significantly larger than the contribution to the mass density of the Universe from the luminous matter in galaxies, so we already expected that that there would be some baryonic dark matter. But the predicted values are also much much much smaller than the apparent density of the Universe in dark matter. In other worse, if Big Bang Nucleosynthesis is correct, you expect there to be baryonic dark matter, but you also expect much much more non-baryonic dark matter. Of course, that doesn't mean that all the dark matter isn't baryonic -- nature is under no obligation to follow our theories! -- but the theory's done reasonably well up to know, so it's worth remembering and is a reminder to be careful.
Gates also contributes a lot of money to charity. One might think that doesn't mean much since he's the richest guy in the world. I say to them, alright, you donate the same percentage of your wealth to the poor.
This is a silly argument. Someone who makes a million dollars a year finds it much easier to donate half their income to charity than someone who makes $40,000 a year. For Bill Gates, this is even more true. He could donate 99% of his income and live more comfortably than the vast majority of Americans; in contrast, very few people in the U.S. could donate 99% of their income to charity and still make enough money per year to stave off homelessness.
Note that I'm not saying that Bill Gates is stingy; that's not my point. I'm merely saying that your argument is absurd.
Oops. This is the link for plib.
I tried FlightGear last week (under Windows) and it was awful! My machine is no super computer (3.2Ghz P4 and a Ge4600Ti) but I expected more than 2-8fps.
I would expect it too. Most FlightGear Windows users get framerates comparable to what the Linux users get; and your framerates are well below what they should be. I have a comparable or slightly less powerful machine than yours (XP2000+, GF4 Ti4600) and typically get framerates that are an order of magnitude higher than what you're getting (it depends, of course, on the plane, the area, etc.). So something's wrong on your end. Apart from all the usual "check your driver" crap -- I don't think that's it, you've said FS2004 runs well, but it doesn't hurt to make sure -- I'd check the default configuration for FG. People who have complained of absurdly low FlightGear framerates in Windows in the past have often turned out to have FG configuration issues like their visibility turned up to an absurdly high range (e.g. 200km, causing FG to have to worry about all ground structures within 200km, which takes a lot of memory, which causes thrashing, which slows down the machine). I'd also check your version; old versions of FG and the libraries on which it's based (especially plib) were much less powerful than the current. If you still can't solve the problem, and you're feeling helpful, please do subscribe to the flightgear-users or flightgear-devel mailing list and post your problem. Your framerates are abnormally low, and if the problem really is with FlightGear rather than with your setup, then the FlightGear developers would certainly like to get it fixed.
By comparison MS Flight Sim 2004 runs smoothly and looks great
No argument. FS2004 is a great piece of work. I have some knocks on it, but they're mostly because it's not fundamentally the software I'd want it to be, rather than what it is (see below). Compared to its goals, it's fabulous.
- as well as having well regarded flight dynamics,
This is one thing I'd take a bit of exception to. Among real-world pilots who have moved to FG from MSFS, including FS2004, the most common complaint about MSFS has been the realism of the flight dynamics modelling. Among non-pilots who try FG after MSFS, the most common "complaint" by a wide margin has been "the Cessna keeps pulling to the left as I go down the runway and try to take off! FlightGear has a bug!" -- which is, in fact, not a bug.
That's not to say that the modelling of flight dynamics in FlightGear has no problems -- it does. But on the whole, I'd pick it over MSFS. A large fraction of the core FlightGear developers are aero engineering types (some with Boeing and NASA), so it's no surprise that this is where it'd do best. On the other hand . . .
a excellent weather modelling
Yes, here's an area that FG really lacks. It draws clouds well as scenery; but flying through/among the clouds isn't done well. And all the rest of weather -- rain, snow, icing, etc. -- is really nonexistent, and these are important things, especially for pilots. It's not like the FG developers aren't aware of this, and this is an area where slow, halting steps are finally being taken.
and a pretty comprehensive ATC system.
This, too, is an area where FG lacks; but it's an area of current development, even more than the weather issues, if I'm following people's conversations correctly.
The problem is that producing a game requires much more focus and many more resources than 99.9% of OS projects have access to. What's really needed is a high quality, high level OS game engine. Something that hides all the OpenGL/SDL details, that's easy for programmers to pick and use, that's easy extensible, that's cross platform, that builds with multiple compilers and that doesn't require hundreds of lines of code just to initalise.
I'm sure you know this, but what's needed from a g
Dark matter isn't mysterious or unordinary. Dark matter is usually extremely cold but otherwise ordinary matter. Because it's so cold, it can't emit light, hence "dark" matter. So, while they did discover dark matter in the sense that most astrophysicists use the term, they did not discover the really weird stuff.
You have, however, picked up on an important distinction. They found dark matter, but what they really need to find is dark energy. Dark energy is thought to comprise something like 70% of the energy of the universe, and yet, even today, it is a complete mystery.
I dunno whether you're confused about this stuff, but your post makes some statements which are at least confusing, and possibly wrong, depending on what you meant (I can't really tell). So to clarify, for anyone who cares: the energy content of the Universe appears to have three components:
He's the most famous athlete in the world. (yes, more than Jordan) That said, he sucks. (yes, that's an opinion)
I just checked my firewall logs for the last several days, and haven't seen a single hit on 3306.
I have no idea whether you're still reading, it being two days later. But I just noticed your reply, so I'll go ahead and respond. But the first thing I need to say is that again, your response is replete with comments that indicate that you don't really understand what the Big Bang model is and is not, and in particular the difference between the Big Bang model and the standard cosmological model as a whole (of which the Big Bang model is but a component). Quantum fluctuations of the vacuum, for instance, are an important component of the standard cosmological model, but have absolutely nothing to do with the Big Bang model. It's sorta like the difference between "physics" and "thermodynamics." Ohm's Law is a part of physics; it is not a part of thermodynamics, even though thermodynamics are a component of physics. The scope of the Big Bang model -- what it describes, explains, and predicts -- is only a segment of the larger standard cosmological model. There are many uncertainties in the standard cosmological model, and some of its parts are doubtless wrong. However, that component of it that relates the large-scale evolution of space to the energy content of the Universe, that we refer to as "the Big Bang model," is on pretty sturdy ground.
You're absolutely right that an accelerating universe doesn't disprove a Big Bang; I thought about that right after I posted. I'm not sure why I threw that in.. I was thinking about what initial conditions of the Big Bang we can try to deduce from observational data. An accelerating universe does however, make us step back, and consider that there must be "more to it" than a big explosion acted on merely by gravity.
And already we're into trouble. I really don't mean anything personal by this, I promise. But your lack of understanding of what the Big Bang model is, explains, and predicts, is illustrated by the last sentence you've written here.
The Big Bang model does not involve "a big explosion" of any kind. Qualitatively, the Big Bang model posits that a long time ago, the contents of the Universe were everywhere very hot and very dense, and that since then, space has been expanding and those contents have been cooling because of that expansion. That's it. That's all. Note that I didn't say anything at all about a singularity, or the beginning of time, or stuff exploding out from a point, or anything like that; none of these are part of the Big Bang model. It is true that by blindly extrapolating the Big Bang equations of evolution (the Friedmann equations) backwards, one arrives at a spacetime singularity; but we have no idea whether it's valid to do that, since in doing so one necessarily speaks of times when the average energy of the stuff in the Universe is higher than reached in any experiment humans have ever done (up to infinitely high energies as one approaches the putative singularity). We don't know what the physics of the Universe was like at temperatures higher than about 1 TeV (about 10^16 degrees). We have theories, but we have no idea whether those theories are correct, because no one has been able to do experiments that can test or falsify them. All we can talk about is the domain over which we understand the physics. From that, we argue that the Universe was once very very dense and hot, and it's been expanding and cooling ever since.
If you believe that as you look at larger and larger scales, the mass/energy distribution in the Universe converges towards homogeneity and isotropy, and if you believe that general relativity is an accurate description of the behavior of gravity on large scales, you're stuck with the Big Bang model: those two assumptions require the Big Bang model. The first of those two facts tells you something important about the structure of space on large scales (i.e. that it can be described by the so-called Robertson-Walker metric); the second gives you a set of equations that related the structure of space, and its evolution, to the mass/energy content of the Universe.
Another problem is the age of the universe as determined by looking deep into space and saying "ah, theres the edge! and if we look in the opposite direction at the same deep distance there it is again! the edge of the universe! the universe must be N billion years old." Uniformity as described in the parent post would put earth at the dead center if the universe were expanding and we really were looking at the edge of it.
Once again, as a previous poster suggested, you really need to take the time to learn about physical cosmology before exclaiming that "parts of the Big Bang theory . . .just don't make sense." You're right that the things you say in your paragraphs above don't make sense; where you're wrong is in your belief that these are in some way part of the Big Bang model. You don't understand what the model says. You are asserting what you think it says -- assertions that are wrong -- and then pointing out absurdities about those assertions. But what you're saying is irrelevant since the Big Bang model isn't like that.
Sigh.
Before going any further into your post, it's important to to remember that there is an enormous difference between the (Relativistic Hot) Big Bang model, and the standard cosmological model (of which the Big Bang model is a component). There is more to the standard cosmological model than just the Big Bang model, which really only describes the evolution of the spatial scale factor and the dynamics of the fluids contained in space. This is an important point: all three of the "issues" you reference (flatness, the acceleration of the expansion, and the so-called horizon problem) are not problems with the Big Bang. Well, the middle one (the accelerating expansion) isn't a problem at all, of any sort, and someone who suggests it is doesn't understand physical cosmology. The other two may indeed turn out to be problems for the standard cosmological model, but most emphatically are not problems with the Big Bang model, since they lay outside its domain.
It's a bit like suggesting that there must be something wrong with the round-Earth model because it doesn't explain why we get tornados. It's not part of the domain of applicability of the Big Bang model to answer the question of why the flatness and horizon problems exist. OTOH, our overall model of cosmology had better explain the flatness and horizon problems. If it doesn't, and is superseded by something else, that something else will almost certainly contain within it a description of the dynamics of the expansion that looks just like the Big Bang model.
As for your statement that the Big Bang model "does not explain the increasing evidence that the expansion of the universe is actually accelerating" . . .this is a bizarre statement, since it seems to suggest that the Big Bang model somehow predicts or requires that the expansion of the Universe not be accelerating. This is not true. Under the Big Bang model, the dynamics of the expansion are determined by a set of properties of the Universe (e.g. the density of the Universe in normal matter, the density of the Universe in relativistic fluids such as photons, the vacuum energy density of the Universe, etc.). The Big Bang model does not make predictions about the values of these parameters; it merely provides a mathematical framework that allows you to deduce "if these are their values, then this is what will happen." Non-zero cosmological constant models with accelerating expansion are not only permissable under the Big Bang model, but have been actively considered by theorists in different contexts for a very long time, since long before Bob Kirshner and Saul Perlmutter's research groups started turning out their data on the high-z Hubble diagram using Type Ia supernmova data. In fact, if you were to ask Kirshner or Perlmutter or Adam Riess or Brian Schmidt or anyone else associated with these projects, they'd tell you that one of the neat things about their evidence of acceleration is that they place constraints (which are non-zero) on the vacuum energy density of the Universe; those constraints come from the Big Bang model.
Your statement about fine-tuning in the context of the flatness problem is a little off. What would have been more disturbing to cosmologists is if the Universe were not flat, but were near flat. A Universe which is flat at early times stays flat; a Universe which is even slightly positively or negatively curved is driven away from flatness very very quickly. This was the fine-tuning problem that worried cosmologists before the BoomerANG and MAP results -- data seemed to suggest that the Universe was only slightly negatively curved, which in turn implied at very early times a Universe infinitely close to flat but not flat. There are a variety of physical theories out there to explain why the Universe would be flat; to explain w