Ah, should have read this before I posted. That's very close to my workflow, except that I export to ePub and clean it up before using Calibre to get it to Kindle.
(Though I don't use LyX - in my experience, which is years out of date now - it produces doggy LaTeX. I find it easier to just code it in Emacs. Kile produces reasonable LaTeX output if you want a GUI though.)
Out of interest, why on Earth are you writing it in Google Docs? When I write things I tend to use LaTeX, which probably strikes most people as even more insane but it compiles up to lovely PDFs, and it's pretty quick to swap it to HTML and build up an ePub or MobiPocket. I could of course write straight in HTML (or in markup which could be easily swapped to both) but I'm very used to LaTeX.
I've not had too many problems converting properly clean RTFs into ePub or MobiPocket and vice-versa using Calibre. I find it's actually a lot easier to build the LaTeX version for printed copies, convert it into the ePub version for an eBook, and then just use Calibre to port it to different formats. I've not had a noticeable issue yet.
"The goal" you talk about is Zubrin's goal, and it's totally laudable if unrealistic. Thing is, we're working in reality. Reality does not recommend bankrupting yourself on a risk when there are better ways of making money nearer home. Mars is a dream and will remain so for a long time. The Moon is realistic but it's very hard to make an economic argument for - or you can bet the Americans or Chinese already would have done.
As for a colony on Mars being realistic and "not any more risky than plenty of other things Americans have done" - name one. Taking off from Earth, leaving Earth orbit, flying out of the van Allen belts and being exposed to the raw solar wind; reaching Mars; landing on Mars; setlting on Mars; surviving well out of your own biosphere for long enough to make it worthwhile; doing *anything* of worth on Mars; lifting off from Mars (doubtless sick from the change in gravity, in air, in food and in everything we take for granted); getting back across space assaulted by the raw solar wind; landing back on Earth; not becoming sick form the shock of exposure to your native environment. It's tough.
Spain finding America was pure economics. Columbus was funded to find a rapid route the far East. What is the economics of chucking money at Mars? The Moon makes some sense. Not much - too expensive - but some. Mars? Nah. And even for the Moon, robots make sense.
The "humanity is safer" argument also doesn't wash with me, I'm afraid. If the Earth goes we're fucked, settlers or no. The settlers won't have the plant life, the resources, the water, the oxygen, or anything more for more than a hundred settlers at an extremely optimistic guess. If humanity goes, what emerged from that population would bear little resemblance to us, if it survived at all.
Yeah but you're forgetting that that imaginary money governs our lives. I'm aware that if the whole world at the same time decided to declare money imaginary we'd be able to do anything - but that's not the reality. Maybe if the developed nations of the world (including India and China, and obviously Russia, the EU and the USA) agreed to do this and fund it by a mutual fund then it would be great - but that won't happen, in all reality. The raw materials may be an investment, if it works out, but it may very well not.
And to be honest, if it *does* work out I can guarantee that any government worth its salt (which is probably most of them because they are at least advised by people who generally know something of what they're talking about) is going to be extremely cautious about risking the lives of their astronauts. The combination of cost - and it *is* an issue, although we may wish the economy to be set up differently - and the danger to human life is too much to do anything other than rely on robots for *at least* the initial stages and probably the bulk of it. It depends what we're doing.
I agere with you, the machines are the way to go, and there are times humans will be better. But the economical thing with humans will involve resources - mines, in particular. Beyond that I honestly cannot see the benefits.
Tourism is a total red herring. The money involved is minimal and the science even more so. We already know how to put people in low Earth orbit; all that the space tourism companies are doing is trying to find a way of putting people in even lower orbit cheaply, and that for a pretty short amount of time. If there's a future in space it's in things that are actually of benefit to humanity - rare earths and metals are the things that spring to mind the most, along with somewhere to let the excesses of industry go unnoticed - rather than any dream.
People have raised the discovery of America. I don't want to offend any Americans but seriously, do you think it was discovered on a dream? If so, you want to go back to your history books. It was discovered on the hope of a short route to the far East. Pure economics. Someone took a gamble, sure, but they weren't funding an expedition for glory, they were funding it for pure money. (If we go further back, the Vikings went for lumber - because it was a lot cheaper to go to northern Canada than it was to go to Norway.) Otherwise people are raising dreams. I've never said dreams aren't great - but they're not reality. Reality is what we can buy and what we can afford, within the system we have.
Also, one final point, you seem to be forgetting that I am not in any way opposed to the exploration of space. What I'm opposed to is throwing away money and resources on *manned* space exploration. We can send ten robotic missions up and have five fail and still be well ahead of where we would be with one manned mission... which could very well fail losing both the money and the trained astronauts. Robots are cheaper, frankly, and a lot less contentious because no-one cares if a robot is splattered across the face of Mars because two teams in NASA used different units.
hahaha. i love the quality of discourse on slashdot.
at least the anonymous coward above bothered to write something sane, even if i disagree with him. it's hard to argue with a "fuck you" because it would just make both of us look like retards.
Good that you post anonymously too - otherwise you may have had to point out that I'm also a theoretical physicist and a cosmologist. The bit you wouldn't know from the bio you read is that my future career also rests on satellites and on governments being willing to pursue space science.
The point, which so many here seem to miss in a curiously emotional response to human space flight, is that science can be advanced *so much further* by unmanned missions than manned missions. Manned missions are extraordinarily dangerous and even more extraordinarily expensive. I simply cannot understand a justification for them. Given that NASA has, and unless another Cold War breaks out will always have, a relatively limited budget do we want to spend that on a wide breadth of science including spaceborn telescopes, satellites to Mercury, satellites to the Sun, satellites to the moons of Jupiter and Saturn, satellites to detect deviations from relativity around the Earth, satellites to Pluto, satellites to test the Pioneer effect, satellites dropping landers designed to dig into the ice of Europa, satellites to return to Titan to explore this weird and beautiful alien landscape better... or do we want to send three men to Mars?
Because it'll cost about the same - and sending the men to Mars will take *longer*. Much longer, and there's a big risk they won't come back.
Seriously.
Take what you want from a bio written tongue-in-cheek but this is the reality. Science is much more advanced by satellites exploring the solar system for us and telescopes probing the universe at larger scales and larger energies than we will ever have direct access to, than it ever will be by putting men on neighbouring planets. The only possible reason I can see for going back out of low Earth orbit is to start exploiting the Moon - and even that the case isn't proven. It will cost untold billions to set up processing plants on the Moon, automated mines, technologies to return large quantities of ore (even processed ore, if we can find a way of processing it on the Moon) to Earth, to service it which may well take human intervention, to actually somehow monetise it. Setting up Moonbases would be beyond the resources of a single country; getting anything back would be equally much, or more.
Do we want a few men experiencing that, for the greater good of fuck all, or do we want science? Both isn't an option because we can't afford it. So what is it? More for less, or a few chosen people experiencing something? If you want the latter, good luck arguing your case - you've got romance on your side, but you don't have economics.
Exactly! Though I don't even knock the military-industrial-congressional complex so much, partly because I'm not American and partly because there's a hell of a lot of money sloshing around in that system and it provides a hell of a lot of jobs and keeps alive a lot of manufacturing.
Yes, I lack the vision to see that spending the equivalent of a small country's GDP on putting three men onto Mars where they'll liable only get radiation poisoning anyway and go insane with tedium is the best thing that could ever happen to Earth!!!!!
Seriously, grow up.
"You're against spending any more money on space exploration"
No I'm not, I'm against spending more money on *manned* space exploration until there's something more useful that can come out of it than a few grainy shots of astronauts bouncing around on the Moon trying to justify their presence there.
"Yet you offer no logical reasons for this"
You're broke. So are we. Flushing untold billions and trillions down the drain to send a few men to Mars is not going to be a sensible plan. The usual retort is to point out the money that goes on the military. The military budget's can't be slashed *that* much. Of course, I guess dreamers such as yourselves don't care about the millions of jobs that are tied to defence contracts across the States alone, let alone in the rest of the developed world, and you're confident that there will never again be a need for an overwhelmingly powerful military force. It must be nice to have such faith in mankind.
"we have hundreds of satellites up there, orbiting the earth, providing vital roles to keep our modern world going"
Wow! Are they manned satellites!?!? I thought they were, you know, unmanned! A bit like robots! Gee.
"The potential for energy generation and mineral extraction are tantalizing"
Yeah, I believe I mentioned the opportunities of hte Moon. Forgive me for not wanting to blow our budgets even further chasing what may turn out to be one massive pipe dream until there is proof that it works. Proof that would not require a human presence, I might add.
"Thanks to Virgin Galactic and other private ventures, in the next five years, we are going to have more humans go to space than we have had in the past fifty years!"
Wheee! Achieving what, precisely? A few enormously wealthy men get to see the curvature of the Earth. The achievement is impressive but I'm waiting to see how getting a few millionaires into orbit is going to provide us with such immense profits as space doubtless provides. Surely we can achieve exactly the same by sending up fifty robots for every fat businessman? Yes. Yes, we could.
Hahahaha! That's your retort? "Fuck you"? Feel free to dream - the rest of us will live in reality glad that the dreamers aren't pissing away what little money is left to us chasing their dreams. Yes, I know the US spends trillions of dollars on the military. That doesn't suddenly mean it's fine to spend hundreds of billions on sending a few ex-pilots into space to achieve something a robot would achieve for a tiny fraction of the cost and much less risk.
You'd also have to make the robots piss urine and shit, well, shit - and process that from organic materials grown on-site. That would be one interesting project, designing that.
And your dream is worth pissing hundreds of billions of dollars down the shitter for? We can all dream, but I've never seen a sensible rationale for putting men any further into space than we already do - frankly, even that is questionable. Going back to the Moon would be an enormous waste of money unless we plan on exploiting its minerals and the fact that we can pollute the far side however much we like, and even that would be prohibitively expensive. Going further than the Moon would be horrifically expensive, horrifically dangerous and ultimately horrifically pointless, and astronauts would return half-insane through the tedium and loneliness. As for tourists, that's always going to remain a pipe-dream. It's just too costly to get out of Earth's gravity well, and *nothing* is going to change that. No new propulsion device can remove the simple truth that it costs that much energy to get away from Earth, and that energy has to come from somewhere, and there is absolutely nothing in the pipeline that could make it cheap enough. Not fusion, nothing. Science fiction is lovely, but reality is harsh and unfortunately we live in reality.
You're talking to astronomers - if you saw any codes we've written you'd know full well that most of us can't program for toffee:) What's pretty much standard is to use the float size built into your compiler. Some people redefine them in the headers of their codes and then just ignore it. I dread to think how much numerical noise has been touted as a result over the history of astronomy, only to vanish when looked at a bit more closely at the cost of only a few hundred man-hours and CPU time. Thankfully not much of it will have been published.
I can guarantee that this isn't the case. Some of us are excessive and use it to sixteen significant figures or so. Seriously, if we're doing calculations we're using C or Fortran. What type of float do you know that stores so many digits? I just do what I think most people do and fill up the number of bits in the float I'm using - and even that's more than needed.
:) That's exactly what I'd like. I'm fine with a menu bar at the top of the screen - it doesn't bother me much one way or the other so long as it's consistent. I just wish Apple would mirror it across the screens.
You try claiming that it's quicker to get to, say, File->Open when it's attached to the screen on the far left and the program you're working with is on the far right. The difference could be anything like 10 pixels compared to more than 3,000. Your argument doesn't make much sense on a multiple screen setup, even if it's fine on a single screen. I like OSX's UI, myself, but only having a menu on one screen when I'm working multiscreen drives me bonkers as well.
1: Are you suggesting that the cosmos is filled with "long nano fibers"? Feel free to model it (properly), write it up rigorously and put it onto the arxiv; I'm sure people would read it. How "long" are you talking? What's the production mechanism? Or are they left behind by alien civilisations...? And yes, terms considering the dust *are* included in analyses. Generally they'll be bundled into systematic errors. There have also been numerous dedicated studies into the effects of dust. (Besides, I'm always happy to ignore the supernova data. Feel free to explain how the long carbon nanotubes can ensure that the CMB and BAO datasets alone combine to constrain \Omega_M=0.3 and \Omega_Lambda=0.7. We don't *need* the supernovae anymore. The fact that CMB+SN1a \approx CMB+BAO is frankly pretty impressive and suggests that the systematics are reasonably controlled.)
2: The cosmological constant is not ruled out by the Bianchi identities. Do you know what the Bianchi identities are? They're *differential identities*. So if I add a term proportional to the metric, and I'm working in a theory (like GR) with a metric-compatible connection, the cosmological constant is allowed by the Bianchi identities. \nabla^\mu G_{\mu\nu}=\nabla^\mu (G_{\mu\nu}-\Lambda g_{\mu\nu}) if \nabla^\mu g_{\mu\nu}=0. Do you have an issue with that? If so, write it up rigorously and put it onto the arxiv. I'm sure people would read it.
3: The Einstein tensor *is* a "second-rank tensor". G_{\mu\nu}=R_{\mu\nu}-\frac{1}{2}g_{\mu\nu}R. R_{\mu\nu} is a tensor. g_{\mu\nu} is a tensor. Are you trying to claim that G_{\mu\nu} isn't a tensor? Or are you proposing that we should use a theory of gravity governed directly by the Riemann and Weyl tensors? Or are you claiming that the Einstein tensor isn't a second-order tensor? Because it is. Because we can write GR like that, of course we can, but still no identity rules out the cosmological constant. Talk of using fourth-order tensors to formulate your theory doesn't change that.
4: Sorry, I wasn't clear. By "phenomenology" I was referring to Robertson-Walker cosmology, not to GR. GR is a theory of gravity. The use of Robertson-Walker metrics is phenomenology. To be brief, the universe is self-evidently inhomogeneous and anisotropic. The CMB is isotropic around the Earth to a high degree. Assuming the Copernican principle, it seems reasonable to then conclude that "on average" (whatever that means; you may be aware that we do not possess a well-defined average of a tensor field) the "universe" (whatever that means; it's normally taken to mean the metric) is homogeneous and isotropic. But those "on average" statements immediately raise a problem: what is the right background. The background is, after all, purely fictional. Worse, while it's perfectly plausible that the average metric of spacetime tends towards Robertson-Walker for sufficiently large domains (perhaps with a radius above 200Mpc or so), it does not at all follow that the dynamics of the universe averaged over sufficiently large domains are themselves Robertson-Walker, due to the nonlinearity of the Einstein equations. What this boils down to is that RW cosmology, while startlingly successful and currently unchallenged by a serious complete competitor, is phenomenology. We don't know if the dark matter term is actually dark matter, a manifestation of relativistic corrections, or the result of a badly-defined average. Exactly the same goes for the dark energy. Until we can solve these issues - which involve pure general relativity and no new physics - RW cosmology is and will remain phenomenology. No worse for that; many great theories are phenomenological. But phenomenology nonetheless.
5: Speculation about negative masses isn't necessarily helpful. If you've got a good reason to postulate negative masses you have to follow through every consequence of such, right it up rigorously, and publish. I can guarantee you'll find people generally hostile to assume that negative mass can exist, so you'll have to make some very persuasiv
"how do we know that the observable universe is the whole universe?"
We don't and it almost certainly isn't; certainly, I doubt many people seriously believe it is.
"What if the Big Bang, was just one of a very large number of 'local' bangs."
Something very close to this idea lies at the heart of "chaotic inflation" which is still pretty much the most widely-used version of inflationary theory. It's occasionally described as a "seething foam of spacetime" with little bubbles popping up through quantum fluctuations eveywhere, and some of them having the right conditions inside to inflate, making another universe.
"If these other universes were far enough away, say a billion billion billion diameters of this universe, would there be any way to detect them? "
Not directly. Indirectly, it would depend on the details of the theory that produced them.
"A re-collapsing universe would also eliminate the conundrum, but it looks as if that is now ruled out."
Why do you say that? Again, it's very dependent on the details of the theory. You might be referring to the Gurzadyan and Penrose papers that were rubbished quite recently. The theory is basically fine, so far as anyone's aware; Penrose hasn't actually published the details for how it all works, but it's a nice enough mathematical trick. (Basically, once everything including black holes has decayed to radiation there's precious little difference between the ultimate future and the ultimate past, so conditions are right for more fluctuations that trigger another big bang. Or something like that. Details are hard to come by.) The problem was the analysis of the CMB - more specifically, the interpretation of that analysis. Find a different prediction from Penrose's model and it'll still be viable to test it. The same goes for any other cyclic model.
No no no you see you make everything out of neutrinos! That way you can get where you're going a couple of days faster than light, which *obviously* opens the universe to exploration because it would only take you about four years to get the nearest star! Building everything, including yourself, out of neutrinos is just an engineering problem and those mighty engineers are just being held back by us pathetic weedy little killjoy fucking PHYSICISTS. Fuck those physicists.
A balloon is actually one of the best analogies anyone's been able to come up with, it just gets explained badly. A balloon is a great analogy because the (2D) *surface* of the balloon acts the same way as the (3D) universe does. Expansion with no centre and everything moving away from everything else. That's why the balloon analogy is used so often and then mangled and misunderstood.
Slashdot Mirror
Ah, should have read this before I posted. That's very close to my workflow, except that I export to ePub and clean it up before using Calibre to get it to Kindle.
(Though I don't use LyX - in my experience, which is years out of date now - it produces doggy LaTeX. I find it easier to just code it in Emacs. Kile produces reasonable LaTeX output if you want a GUI though.)
Out of interest, why on Earth are you writing it in Google Docs? When I write things I tend to use LaTeX, which probably strikes most people as even more insane but it compiles up to lovely PDFs, and it's pretty quick to swap it to HTML and build up an ePub or MobiPocket. I could of course write straight in HTML (or in markup which could be easily swapped to both) but I'm very used to LaTeX.
I've not had too many problems converting properly clean RTFs into ePub or MobiPocket and vice-versa using Calibre. I find it's actually a lot easier to build the LaTeX version for printed copies, convert it into the ePub version for an eBook, and then just use Calibre to port it to different formats. I've not had a noticeable issue yet.
Well, yes. Or you could just send a monkey, but it would be a lot more impressive the other way...
"The goal" you talk about is Zubrin's goal, and it's totally laudable if unrealistic. Thing is, we're working in reality. Reality does not recommend bankrupting yourself on a risk when there are better ways of making money nearer home. Mars is a dream and will remain so for a long time. The Moon is realistic but it's very hard to make an economic argument for - or you can bet the Americans or Chinese already would have done.
As for a colony on Mars being realistic and "not any more risky than plenty of other things Americans have done" - name one. Taking off from Earth, leaving Earth orbit, flying out of the van Allen belts and being exposed to the raw solar wind; reaching Mars; landing on Mars; setlting on Mars; surviving well out of your own biosphere for long enough to make it worthwhile; doing *anything* of worth on Mars; lifting off from Mars (doubtless sick from the change in gravity, in air, in food and in everything we take for granted); getting back across space assaulted by the raw solar wind; landing back on Earth; not becoming sick form the shock of exposure to your native environment. It's tough.
Spain finding America was pure economics. Columbus was funded to find a rapid route the far East. What is the economics of chucking money at Mars? The Moon makes some sense. Not much - too expensive - but some. Mars? Nah. And even for the Moon, robots make sense.
The "humanity is safer" argument also doesn't wash with me, I'm afraid. If the Earth goes we're fucked, settlers or no. The settlers won't have the plant life, the resources, the water, the oxygen, or anything more for more than a hundred settlers at an extremely optimistic guess. If humanity goes, what emerged from that population would bear little resemblance to us, if it survived at all.
Yeah but you're forgetting that that imaginary money governs our lives. I'm aware that if the whole world at the same time decided to declare money imaginary we'd be able to do anything - but that's not the reality. Maybe if the developed nations of the world (including India and China, and obviously Russia, the EU and the USA) agreed to do this and fund it by a mutual fund then it would be great - but that won't happen, in all reality. The raw materials may be an investment, if it works out, but it may very well not.
And to be honest, if it *does* work out I can guarantee that any government worth its salt (which is probably most of them because they are at least advised by people who generally know something of what they're talking about) is going to be extremely cautious about risking the lives of their astronauts. The combination of cost - and it *is* an issue, although we may wish the economy to be set up differently - and the danger to human life is too much to do anything other than rely on robots for *at least* the initial stages and probably the bulk of it. It depends what we're doing.
I agere with you, the machines are the way to go, and there are times humans will be better. But the economical thing with humans will involve resources - mines, in particular. Beyond that I honestly cannot see the benefits.
Tourism is a total red herring. The money involved is minimal and the science even more so. We already know how to put people in low Earth orbit; all that the space tourism companies are doing is trying to find a way of putting people in even lower orbit cheaply, and that for a pretty short amount of time. If there's a future in space it's in things that are actually of benefit to humanity - rare earths and metals are the things that spring to mind the most, along with somewhere to let the excesses of industry go unnoticed - rather than any dream.
People have raised the discovery of America. I don't want to offend any Americans but seriously, do you think it was discovered on a dream? If so, you want to go back to your history books. It was discovered on the hope of a short route to the far East. Pure economics. Someone took a gamble, sure, but they weren't funding an expedition for glory, they were funding it for pure money. (If we go further back, the Vikings went for lumber - because it was a lot cheaper to go to northern Canada than it was to go to Norway.) Otherwise people are raising dreams. I've never said dreams aren't great - but they're not reality. Reality is what we can buy and what we can afford, within the system we have.
Also, one final point, you seem to be forgetting that I am not in any way opposed to the exploration of space. What I'm opposed to is throwing away money and resources on *manned* space exploration. We can send ten robotic missions up and have five fail and still be well ahead of where we would be with one manned mission... which could very well fail losing both the money and the trained astronauts. Robots are cheaper, frankly, and a lot less contentious because no-one cares if a robot is splattered across the face of Mars because two teams in NASA used different units.
hahaha. i love the quality of discourse on slashdot.
at least the anonymous coward above bothered to write something sane, even if i disagree with him. it's hard to argue with a "fuck you" because it would just make both of us look like retards.
Good that you post anonymously too - otherwise you may have had to point out that I'm also a theoretical physicist and a cosmologist. The bit you wouldn't know from the bio you read is that my future career also rests on satellites and on governments being willing to pursue space science.
The point, which so many here seem to miss in a curiously emotional response to human space flight, is that science can be advanced *so much further* by unmanned missions than manned missions. Manned missions are extraordinarily dangerous and even more extraordinarily expensive. I simply cannot understand a justification for them. Given that NASA has, and unless another Cold War breaks out will always have, a relatively limited budget do we want to spend that on a wide breadth of science including spaceborn telescopes, satellites to Mercury, satellites to the Sun, satellites to the moons of Jupiter and Saturn, satellites to detect deviations from relativity around the Earth, satellites to Pluto, satellites to test the Pioneer effect, satellites dropping landers designed to dig into the ice of Europa, satellites to return to Titan to explore this weird and beautiful alien landscape better... or do we want to send three men to Mars?
Because it'll cost about the same - and sending the men to Mars will take *longer*. Much longer, and there's a big risk they won't come back.
Seriously.
Take what you want from a bio written tongue-in-cheek but this is the reality. Science is much more advanced by satellites exploring the solar system for us and telescopes probing the universe at larger scales and larger energies than we will ever have direct access to, than it ever will be by putting men on neighbouring planets. The only possible reason I can see for going back out of low Earth orbit is to start exploiting the Moon - and even that the case isn't proven. It will cost untold billions to set up processing plants on the Moon, automated mines, technologies to return large quantities of ore (even processed ore, if we can find a way of processing it on the Moon) to Earth, to service it which may well take human intervention, to actually somehow monetise it. Setting up Moonbases would be beyond the resources of a single country; getting anything back would be equally much, or more.
Do we want a few men experiencing that, for the greater good of fuck all, or do we want science? Both isn't an option because we can't afford it. So what is it? More for less, or a few chosen people experiencing something? If you want the latter, good luck arguing your case - you've got romance on your side, but you don't have economics.
This post should be modded up for the line 'The universe says a big "fuck you" to dreamers all the time. Welcome to adulthood!'
Exactly! Though I don't even knock the military-industrial-congressional complex so much, partly because I'm not American and partly because there's a hell of a lot of money sloshing around in that system and it provides a hell of a lot of jobs and keeps alive a lot of manufacturing.
Yes, I lack the vision to see that spending the equivalent of a small country's GDP on putting three men onto Mars where they'll liable only get radiation poisoning anyway and go insane with tedium is the best thing that could ever happen to Earth!!!!!
Seriously, grow up.
"You're against spending any more money on space exploration"
No I'm not, I'm against spending more money on *manned* space exploration until there's something more useful that can come out of it than a few grainy shots of astronauts bouncing around on the Moon trying to justify their presence there.
"Yet you offer no logical reasons for this"
You're broke. So are we. Flushing untold billions and trillions down the drain to send a few men to Mars is not going to be a sensible plan. The usual retort is to point out the money that goes on the military. The military budget's can't be slashed *that* much. Of course, I guess dreamers such as yourselves don't care about the millions of jobs that are tied to defence contracts across the States alone, let alone in the rest of the developed world, and you're confident that there will never again be a need for an overwhelmingly powerful military force. It must be nice to have such faith in mankind.
"we have hundreds of satellites up there, orbiting the earth, providing vital roles to keep our modern world going"
Wow! Are they manned satellites!?!? I thought they were, you know, unmanned! A bit like robots! Gee.
"The potential for energy generation and mineral extraction are tantalizing"
Yeah, I believe I mentioned the opportunities of hte Moon. Forgive me for not wanting to blow our budgets even further chasing what may turn out to be one massive pipe dream until there is proof that it works. Proof that would not require a human presence, I might add.
"Thanks to Virgin Galactic and other private ventures, in the next five years, we are going to have more humans go to space than we have had in the past fifty years!"
Wheee! Achieving what, precisely? A few enormously wealthy men get to see the curvature of the Earth. The achievement is impressive but I'm waiting to see how getting a few millionaires into orbit is going to provide us with such immense profits as space doubtless provides. Surely we can achieve exactly the same by sending up fifty robots for every fat businessman? Yes. Yes, we could.
Hahahaha! That's your retort? "Fuck you"? Feel free to dream - the rest of us will live in reality glad that the dreamers aren't pissing away what little money is left to us chasing their dreams. Yes, I know the US spends trillions of dollars on the military. That doesn't suddenly mean it's fine to spend hundreds of billions on sending a few ex-pilots into space to achieve something a robot would achieve for a tiny fraction of the cost and much less risk.
You'd also have to make the robots piss urine and shit, well, shit - and process that from organic materials grown on-site. That would be one interesting project, designing that.
And your dream is worth pissing hundreds of billions of dollars down the shitter for? We can all dream, but I've never seen a sensible rationale for putting men any further into space than we already do - frankly, even that is questionable. Going back to the Moon would be an enormous waste of money unless we plan on exploiting its minerals and the fact that we can pollute the far side however much we like, and even that would be prohibitively expensive. Going further than the Moon would be horrifically expensive, horrifically dangerous and ultimately horrifically pointless, and astronauts would return half-insane through the tedium and loneliness. As for tourists, that's always going to remain a pipe-dream. It's just too costly to get out of Earth's gravity well, and *nothing* is going to change that. No new propulsion device can remove the simple truth that it costs that much energy to get away from Earth, and that energy has to come from somewhere, and there is absolutely nothing in the pipeline that could make it cheap enough. Not fusion, nothing. Science fiction is lovely, but reality is harsh and unfortunately we live in reality.
You're talking to astronomers - if you saw any codes we've written you'd know full well that most of us can't program for toffee :) What's pretty much standard is to use the float size built into your compiler. Some people redefine them in the headers of their codes and then just ignore it. I dread to think how much numerical noise has been touted as a result over the history of astronomy, only to vanish when looked at a bit more closely at the cost of only a few hundred man-hours and CPU time. Thankfully not much of it will have been published.
I can guarantee that this isn't the case. Some of us are excessive and use it to sixteen significant figures or so. Seriously, if we're doing calculations we're using C or Fortran. What type of float do you know that stores so many digits? I just do what I think most people do and fill up the number of bits in the float I'm using - and even that's more than needed.
:) That's exactly what I'd like. I'm fine with a menu bar at the top of the screen - it doesn't bother me much one way or the other so long as it's consistent. I just wish Apple would mirror it across the screens.
You try claiming that it's quicker to get to, say, File->Open when it's attached to the screen on the far left and the program you're working with is on the far right. The difference could be anything like 10 pixels compared to more than 3,000. Your argument doesn't make much sense on a multiple screen setup, even if it's fine on a single screen. I like OSX's UI, myself, but only having a menu on one screen when I'm working multiscreen drives me bonkers as well.
1: Are you suggesting that the cosmos is filled with "long nano fibers"? Feel free to model it (properly), write it up rigorously and put it onto the arxiv; I'm sure people would read it. How "long" are you talking? What's the production mechanism? Or are they left behind by alien civilisations...? And yes, terms considering the dust *are* included in analyses. Generally they'll be bundled into systematic errors. There have also been numerous dedicated studies into the effects of dust. (Besides, I'm always happy to ignore the supernova data. Feel free to explain how the long carbon nanotubes can ensure that the CMB and BAO datasets alone combine to constrain \Omega_M=0.3 and \Omega_Lambda=0.7. We don't *need* the supernovae anymore. The fact that CMB+SN1a \approx CMB+BAO is frankly pretty impressive and suggests that the systematics are reasonably controlled.)
2: The cosmological constant is not ruled out by the Bianchi identities. Do you know what the Bianchi identities are? They're *differential identities*. So if I add a term proportional to the metric, and I'm working in a theory (like GR) with a metric-compatible connection, the cosmological constant is allowed by the Bianchi identities. \nabla^\mu G_{\mu\nu}=\nabla^\mu (G_{\mu\nu}-\Lambda g_{\mu\nu}) if \nabla^\mu g_{\mu\nu}=0. Do you have an issue with that? If so, write it up rigorously and put it onto the arxiv. I'm sure people would read it.
3: The Einstein tensor *is* a "second-rank tensor". G_{\mu\nu}=R_{\mu\nu}-\frac{1}{2}g_{\mu\nu}R. R_{\mu\nu} is a tensor. g_{\mu\nu} is a tensor. Are you trying to claim that G_{\mu\nu} isn't a tensor? Or are you proposing that we should use a theory of gravity governed directly by the Riemann and Weyl tensors? Or are you claiming that the Einstein tensor isn't a second-order tensor? Because it is. Because we can write GR like that, of course we can, but still no identity rules out the cosmological constant. Talk of using fourth-order tensors to formulate your theory doesn't change that.
4: Sorry, I wasn't clear. By "phenomenology" I was referring to Robertson-Walker cosmology, not to GR. GR is a theory of gravity. The use of Robertson-Walker metrics is phenomenology. To be brief, the universe is self-evidently inhomogeneous and anisotropic. The CMB is isotropic around the Earth to a high degree. Assuming the Copernican principle, it seems reasonable to then conclude that "on average" (whatever that means; you may be aware that we do not possess a well-defined average of a tensor field) the "universe" (whatever that means; it's normally taken to mean the metric) is homogeneous and isotropic. But those "on average" statements immediately raise a problem: what is the right background. The background is, after all, purely fictional. Worse, while it's perfectly plausible that the average metric of spacetime tends towards Robertson-Walker for sufficiently large domains (perhaps with a radius above 200Mpc or so), it does not at all follow that the dynamics of the universe averaged over sufficiently large domains are themselves Robertson-Walker, due to the nonlinearity of the Einstein equations. What this boils down to is that RW cosmology, while startlingly successful and currently unchallenged by a serious complete competitor, is phenomenology. We don't know if the dark matter term is actually dark matter, a manifestation of relativistic corrections, or the result of a badly-defined average. Exactly the same goes for the dark energy. Until we can solve these issues - which involve pure general relativity and no new physics - RW cosmology is and will remain phenomenology. No worse for that; many great theories are phenomenological. But phenomenology nonetheless.
5: Speculation about negative masses isn't necessarily helpful. If you've got a good reason to postulate negative masses you have to follow through every consequence of such, right it up rigorously, and publish. I can guarantee you'll find people generally hostile to assume that negative mass can exist, so you'll have to make some very persuasiv
Given that the entire topic of other "universes" is totally and utterly theoretical, yes. (In a manner of speaking, of course.)
To think I never knew this. You learn something every day.
fucking theoretical physicists. they need to be stamped out. with EXTREME prejudice.
Aha, I see. I didn't even know you could check what the mods were for, which probably says a lot about me.
"how do we know that the observable universe is the whole universe?"
We don't and it almost certainly isn't; certainly, I doubt many people seriously believe it is.
"What if the Big Bang, was just one of a very large number of 'local' bangs."
Something very close to this idea lies at the heart of "chaotic inflation" which is still pretty much the most widely-used version of inflationary theory. It's occasionally described as a "seething foam of spacetime" with little bubbles popping up through quantum fluctuations eveywhere, and some of them having the right conditions inside to inflate, making another universe.
"If these other universes were far enough away, say a billion billion billion diameters of this universe, would there be any way to detect them? "
Not directly. Indirectly, it would depend on the details of the theory that produced them.
"A re-collapsing universe would also eliminate the conundrum, but it looks as if that is now ruled out."
Why do you say that? Again, it's very dependent on the details of the theory. You might be referring to the Gurzadyan and Penrose papers that were rubbished quite recently. The theory is basically fine, so far as anyone's aware; Penrose hasn't actually published the details for how it all works, but it's a nice enough mathematical trick. (Basically, once everything including black holes has decayed to radiation there's precious little difference between the ultimate future and the ultimate past, so conditions are right for more fluctuations that trigger another big bang. Or something like that. Details are hard to come by.) The problem was the analysis of the CMB - more specifically, the interpretation of that analysis. Find a different prediction from Penrose's model and it'll still be viable to test it. The same goes for any other cyclic model.
No no no you see you make everything out of neutrinos! That way you can get where you're going a couple of days faster than light, which *obviously* opens the universe to exploration because it would only take you about four years to get the nearest star! Building everything, including yourself, out of neutrinos is just an engineering problem and those mighty engineers are just being held back by us pathetic weedy little killjoy fucking PHYSICISTS. Fuck those physicists.
A balloon is actually one of the best analogies anyone's been able to come up with, it just gets explained badly. A balloon is a great analogy because the (2D) *surface* of the balloon acts the same way as the (3D) universe does. Expansion with no centre and everything moving away from everything else. That's why the balloon analogy is used so often and then mangled and misunderstood.