> and whose to say that the Universe doesn't oscillate?
That possibility is still definitely on the table, but it's losing support.
It has almost no support in the mainstream cosmological community, and hasn't for quite a while.
A universe that slows, stops, and falls back in a "Big Crunch" is a negative curvature universe. A universe that expands infinitely is a positive curvature universe. Between them you have a precise zero-point, a "flat" zero curvature universe where the expansion rate slows infinitely close to zero.
Actually, this is backwards. Traditionally, it's been positively curved universes that recollapse, while negatively curved universes converge towards a free expansion where the expansion scales linearly with time (that is, as the age of the Universe doubles, everything expands by a factor of two). So that's backwards. But also, in that traditional view, flat universes expand infinitely as well; they simply asymptotically approach (but never quite reach) an end to the expansion (I think you were trying to say that, but I wanted to make it clear).
But importantly, this view has neglected the possibility of a nonzero vacuum energy, or cosmological constant. That's why I used the adverb "traditionally" above -- traditionally, we've assumed there to be no vacuum energy, and set the cosmological constant to zero. We now have significant observational evidence that this was wrong. In the presence of a cosmological constant, it's no longer possible to simply say "negative curvature = expands forever, zero curvature = expands forever but asymptotically approaches stopping, positive curvature = recollapse." Those simple relations between curvature and fate no longer hold if there's a cosmological constant.
It's true that the energy content of the Universe drives the time-evolution of its expansion; it's also true that the energy content of the Universe determines its curvature. But the presence of a cosmological constant changes the Friedmann equations in such a way that that simplistic correlation between curvature and how the expansion will proceed no longer holds true.
This is illustrated by the apparent situation with our own Universe (see below).
There are very strong theoretical reasons to think that the universe has exactly zero curvature - precisely on the balancing point. On the other hand recent observations seem to suggest accelerating expansion, possibly runaway positive curvature taht would eventually rip apart everything - the Earth, atoms, even protons.
Actually, we have strong observational evidence that the Universe is flat (that is, has zero curvature), from observations of the primary anisotropies in the cosmic microwave background.
At the same time, you're correct that recent observations indicate an acceleration to the expansion. But this is not contradictory when a vacuum energy exists. In fact, a vacuum energy is the only way to get an accelerating
expansion; a negative curvature universe with no cosmological constant does expand infinitely, but that expansion does not accelerate.
OK, here's a batch more response. I hope this is interesting . . .
The temperature of the cosmic background radiation was a retrodiction, not a prediction. Alpher and Herman got the closest, with a prediction of 5 Kelvins, but
what you don't often hear is that the prediction was later adjusted to 28 Kelvins.
This is pretty commonly brought up by proponents of alternative cosmologies. I've had discussions with proponents of several in the past, and this frequently gets mentioned. It's unfortunate, because most people realize that this is pretty much a red herring. No prediction of the cosmic microwave background's blackbody temperature prior to the CMBR's discovery was ever thought very likely correct, since making the prediction required as mathematical input other cosmological parameters which had not yet been measured with any precision at all. The mere existence of the microwave background, and that it should be so uniform and such an incredibly good blackbody (at this point, the best blackbody ever observed anywhere) were the real predictions; and their success actually is pretty impressive -- more impressive than they might seem at first glance.
To elaborate . ..we know what temperature the background radiation would have had to be at at the time of decoupling/recombination, just because of atomic physics. In order to predict what the temperature is now, one has to know how much the Universe has expanded since then. How do you know that? How do you
know how much the Universe has expanded since recombination? (phrased differently, how do we know what the redshift of the surface of last scattering is?) We
know it now from the current microwave background temperature; but that's of course pretty useless if what you're trying to do is predict the current CMBR temperature. Well, there are ways you can guess. For instance, if you think
you know that the Universe is flat, and that the contribution from vacuum energy is zero; and presuming you know what the Hubble constant is now; and presuming
you know what the energy density of the Universe in matter is now; and given the fact that you know what the radiation energy density had to have been at recombination (because you know what its temperature had to be, from atomic physics);
from these things, you can calculate what the microwave background temperature now ought to be.
How well do you think those things were known then?
And suggesting that that implies a mark against the Big Bang model makes no logical sense. It would be analogous to the following: suppose I'm building a circuit from scratch, having first designed it using what I know of circuit theory from classical electromagnetism. I build it, and my circuit doesn't work as I expected. I then learn that the dielectric constant I'd assumed for a material I
used in my homemade capacitors was wrong, and consequently I'd figured them to have a different capacitance than what they actually had when I built them . ..so of course my circuit didn't work like I thought it would. Apparently, the people who find fault with early guesses at the current CMBR temperature would conclude that the failure of my circuit indicates that circuit theory is incorrect;
but that's false. Like circuit theory, the Big Bang model establishes mathematical relationships between physical parameters of the system it describes. Put the wrong values into the equations, and you'll get wrong values out, which then
won't match subsequent observations. Of course, with what we know now of the cosmological parameters, everything is perfectly consistent, without any tweaking
of the Big Bang model whatsoever.
It is the mere existence of the microwave background -- its omnidirectional uniformity and amazing blackbody spectrum -- that is the prediction of interest. And contrary to assertions from people, these are extremely hard to contrive in other ways. Such alternative sources for the CMBR typically involve a local origin, in
First of all, thanks for coming in with some specifics. Not that I agree with them, but at least now there are things which are not vaguaries to which I can respond.
Unfortunately, responding adequately is going to take a lot of time and a lot of space. I don't know who's still reading this at this point, but I'm going to have to do this over several replies and over time. I hope that's OK.
The "flat universe" case gives a Hubble constant of 65 km/s/Mpc (megaparsec). This amounts to an age of the universe of ~10 billion years. This is one of the "age paradoxes" that have led to some of the more interesting revisions and proposed revisions.
No, this is a false representation of things. It is not the case that an assumption of a flat universe requires a Hubble parameter of 65 km/s/Mpc; it is not the case that a flat universe with a Hubble parameter of 65 km/s/Mpc necessarily indicates an age of 10 Gyr. There was an "age problem" at one point -- a discrepancy between the age of some of the oldest objects in the Universe (globular clusters) with the age of the Universe inferred from its expansion -- but that problem has been resolved, and without any revision to the Big Bang model at all.
To elaborate:
In the Big Bang model, estimating the age of the Universe through the expansion
is possible because the age is functionally related to three things: the Hubble parameter; the large-scale geometry of space (the curvature), induced by the mean energy density; and the relative contributions to the mean energy density from components which scale differently with the expansion of the Universe (e.g. radiation, which scales inversely with the fourth power of the expansion; matter,
which scales inversely with the third power of the expansion, and vacuum energy/cosmological constant, which does not change with the expansion). Knowledge of
all of these things is required to make a prediction of the age of the Universe
from the expansion.
It's true that through the 80's and much of the 90's, there was a perception that there was an age problem: globular cluster ages were suggesting you needed the Universe to have been around for as much as 15 Gyr; requiring an expansion age at least that long seemed (based on what we knew of the other parameters) to require a Hubble parameter as low as 50 km/s/Mpc, which observations did not favor. But in the last 7-8 years, three observational results have occurred which have caused the age problem to disappear. Note that I said observational; no adjustment of the Big Bang model was involved at all.
The first observational result was the lowering of globular cluster ages estimated from observations. This occurred for a number of reasons, the most significant of which was the recalibration of the distance ladder that came from better parallax distance measures to local reference stars from the Hipparcos satellite. Hipparcos observations determined that local reference stars were about 10% farther away than previously thought; this increased the distances to globular clusters, and therefore the luminosities of main sequence turnoff on their HR diagrams. By the summer of 1998, the globular cluster folks were going to conferences quoting maximum ages of just above 13 Gyr.
The second observational result was the lowering of estimates of the Hubble parameter that also came from recalibrations of the distance ladder, which in turn came from two things: the Hipparcos results mentioned previously; and the excellent observations of Cepheid variables that were the main objective of the Hubble Key Project. These brought the observed value of the Hubble parameter down from its previously favored value of around 75 km/s/Mpc or so to values of 65-67 km/s/Mpc, increasing ages estimated through the expansion by 11-15%. These two results dealt with much of the discrepancy between the two ages, but did not resolve it completely.
The third observational result was a dramatic improvement in the determination of th
Well, the BB story has gone along for so much time... some new data whacks it, ok... small nudge and it's consistent.
Can you give an example?
Some new research threatens boatloads of papers, ok... mop it under the rug.
Can you give an example?
Average, uninitiated scientists can't make heads or tails of the nasty slew of hypotherical particles and their family relations (that HAS to be true because it fits the model!)... oh, they're just ignorant.
The Big Bang model makes no predictions whatsoever about the existence of any hypothetical particles, let alone a "nasty slew." The only particles required to be present for the Big Bang model to make accurate predictions are those expected to still be relativistic at the time of Big Bang Nucleosynthesis: namely, the three families of baryons and leptons that we've already detected in experiments here on Earth. In fact, when the BBN calculations were first done, it was discovered that the predictions only made sense if there were three or fewer families of fundamental particles. At that time, we only knew of two for sure. We've since discovered the third in particle accelerators, and measurements of the decay width of the Z0 particle 13 years ago confirmed that no more than three such families could exist. So, contrary to your statement, the Big Bang model not only doesn't predict a "nasty slew of hypothetical particles," but at this point it doesn't predict any hypothetical particles at all, and indeed sets a limit on how many light ones can exist.
It looks to me like you don't know what the Big Bang model actually says. And it looks to me like you don't know what's not the Big Bang model -- that is, what are other ideas that are taken seriously as part of the standard cosmology but are not part of the Big Bang model itself because they deal with cosmological topics that the Big Bang model does not directly address.
Hmm, I've grocked EM and some quantum physics (the basics: Schroedinger, Fermi and the avg undergraduate stuff in a Solid State Phy course) and never got the Alice in Wonderland feeling.
Really? Wow. One of the reasons I loved quantum so much, through undergrad and grad school, was how something that seemed so "Alice in Wonderland"-y to me could be so solidly borne out by experiment. I mean, tunnelling through potential barriers? Come on. But amazingly enough, the answers come out right.
You might argue that modern cosmology can account for all the data (or just give it enough time and it will) but anyone can shoehorn a dataset in a model... just add some epicycles, a nudge here, a constant there... it'll all fit.
But can you give me some examples of how this has gone on, with respect to the Big Bang model?
Our cosmological understanding has undergone a tremendous amount of change in the last 20-25 years, as cosmology has gone from a data-starved science to a data-rich one. Lots of ideas have been put forward, "tweaked" (as you say), shot down, resuscitated, etc. None of that has to do with the Big Bang model. People have definitely tried to massage pet theories when data has come in that didn't quite fit (the topological defect folks -- cosmic strings, etc. -- come to mind); but those theories were not the Big Bang model.
It really seems to me like you don't know, of the set of ideas that make up the standard cosmology and those additional ideas that are taken seriously but not yet fully accepted, what's part of the Big Bang model and what isn't. The popular press carries some of the blame for this -- the phrase "the Big Bang model" is all the cosmology most newspaper science writers know, so when results have challenged cosmological orthodoxy, they've sometimes been described as challenges to the Big Bang model, even though in actuality they've typically said nothing whatsoever one way or the other about the Big Bang model.
> Yes, and no: depending on who you talk to, and the definition of Universe.
> The best one I can come up with is "all space which is connected (in a
> mathematical sense) and includes me at the present time". In that sense,
> regions of black holes are another Universe, for instance.
>
> There are other statements like "the Universe is everything that can be observed",
> which is a much more limiting definition (fundamentally, there's a ton of
> spacetime outside all of humanity's forward and backward light cones), or "the
> Universe is everything", which, well, pretty much occludes all "outside"-ness,
> because as soon as you find something outside, it's not outside. Oookay.
Is it meaningful to talk about the portions of the universe that are outside our light cones as being mathematically connected to us? You can say that they were, but not that they are. There's no such thing as an instantaneous "now" snapshot of the universe, just a snapshot of the current surface of the backwards light cone. In practice, "everything that I can observe" and "everything that is connected to me" refer to the same thing.
I shouldn't speak for the poster to whom you were replying, but I'm pretty sure that he was using the phrase "mathematically connected" in a topological sense, rather than referring to causal connection. If one meant connected in a causal sense, then you're absolutely correct that that means the backwards light cone by definition, and therefore means what I can observe. But you can also talk about the topology of space, and whether the Universe is simply connected, connected, etc.
I think that's how it was meant; and that definition is different from what's observable.
It's just yet-another-inconsistency in the n-th hack to the BB theory introduced to clean up previous gripes.
Can you be more specific? What's the inconsistency here, with what is it inconsistent, and how does that inconsistency speak to the Big Bang model as a whole, specifically? I'm not saying you're wrong (yet); I just can't address your statement directly because it's too vague.
There are without question unsolved problems in cosmology (thank heavens; otherwise, cosmologists would have little to do). I'm interested in your careful argument as to why those problems cannot be solved in the context of the Big Bang model, and therefore falsify it. To me, it seems like you're saying "Since we don't understand how tornadoes form, it's time to realize that the `spherical Earth' model is a failure." That analogy probably seems silly to you, since we have lots of evidence to support the idea of a (nearly) spherical Earth. But we have lots of
evidence that supports the Big Bang model as well, including non-trivial advance predictions borne out by subsequent observation.
The Big Bang model will be falsified if and when a prediction it makes is shown to be false. But that hasn't happened here: the Big Bang model does not make predictions about the specifics of the mass distribution or galaxy formation. Those are topics of importance in cosmology, but they do not directly speak to the veracity of the Big Bang model. Only if the general constraints the Big Bang model places upon galaxy formation are such that these observations should be impossible is there a problem for the Big Bang. Nobody's shown this to be true.
It is true that these observations, if correct, pose a challenge to the standard cosmological model. But there's more to the standard cosmological model than just the Big Bang model.
> This surprise has nothing to do with distance from the "center" of the big bang,
> since there is no center
I've heard this before, and although I don't disagree with it, I've never been able to wrap my brain around it. It seems to me that any explosion has a center, or a point of origin. Even one that expands out into "nothing" like the Big Bang did/is.
This is, unfortunately, a flaw in the name of the model. It conjures up the idea of an explosion of material into surrounding empty space, which is not what the Big Bang model describes. The expansion of the Universe is an expansion of space itself. The galaxies grow farther apart not because they are moving away from each other through space, but because space itself is expanding between them.
Not that that necessarily makes things easier for you. Fundamentally, this points out a failure of one of our most useful way of understanding thimgs: to relate them to things we already understand, or with which we are already familiar.
For instance, when authors of cosmology books for laypersons construct analogies to the expansion of space and the resulting increasing separation of the galaxies, they use things like a loaf of raisin bread expanding in the oven. But that analogy is flawed: the raisin bread has space surrounding it into which it can expand (not to mention a "center"), while no such thing exists for the universe.
A better analogy in that it gets rid of the embedded center is to give up our 3D universe, and instead consider the 2D surface of an inflating balloon. Dots (galaxies) painted on the balloon's surface are all getting farther and farther apart from each other on the surface of the balloon (in space), but no place on the surface of the balloon (no location in the Universe) can be called the center of the expansion (the one place from which things started expanding apart). But this analogy is a bad one, as well. It makes an assumption about the topology of the universe (that it loops around on itself, or is "closed"); the Universe may be that way, but it need not be.
More importantly, this analogy requires the existence of a 3rd dimension (the radial direction) separate from the 2D surface of the balloon; a change in the position of the surface of the balloon with time in that radial direction describes the expansion. But the Big Bang model doesn't require such a hidden dimension which is driving the expansion.
There just isn't something from our day-to-day lives which provides a decent analogy to the expansion of the Universe. It has to be understood on its own terms, without recourse to simple visualization. Not that this is uncommon in physics since the beginning of the 20th Century; for instance, quantum mechanics describes phenomena which are difficult to impossible to describe in terms of how things work in our common sense, everyday world.
In the end, it comes down to a quote from (I think) Feynman (although he was talking about quantum mechanics at the time): "I don't know how to describe it in terms of something you're more familiar with, because I don't understand it in terms of something you're more familiar with."
The NASA page on this quotes a redshift of 2.38.
Do they say how they got it? Did they take full spectra from all these objects? Are some of them Lyman break galaxies? Are any of the redshifts photometric rather than spectroscopic?
Actually, the most straightforward explanation is that galaxies form differently than we think. Considering we have no evidence to the contrary (all we have are simulations), and we do have a fair amount of evidence on the value of the Hubble constant, and therefore an estimate of the age of the Universe, the theory that requires the least changes in the current model would be that galaxies form quicker, and differently, than current theory allows.
I can't make up my mind whether this is the most straightforward explanation or not. It's true that we have very little observational data about galaxy formation. And I don't put too much stock into the semi-empirical galaxy formation models (e.g. the Kauffman et. al. stuff); too many ways to tweak them. But at the same time, you're constrained in what you can do in the Universe before decoupling by anisotropy observations, while the tiny value of the Compton y-parameter in the CBR constrains pushing stuff around by energy imput after decoupling.
I want to think that this is just some outlier, or simply a redshift-space distortion, or something like that. But I'm sure that someone somewhere has already done a calculation of the statistics of peaks in Gaussian random fields to show that it'd be ridiculously improbable even as an outlier (in the first case), or that the growing mode at that redshift should still be so small that enough organized large-scale mass to induce sufficient peculiar velocities necessary to produce such a redshift-space distortion through infall would again be absurdly improbable (in the second case).
As any good evolutionist knows , after the "Big Bang" all the matter in the universe, which had been compressed (through forces and mechanisms unknowable) into a very tiny ball, exploded outward (spherically, with planar tendencies) with tremendous force.
This observation of thousands of galaxies SO FAR OUT from the assumed center of the "Big Bang"
(snip)
Your criticisms would carry more weight if they demonstrated that you understood the relativistic hot Big Bang model at all. The Big Bang model does not presume any very tiny ball, it does not presume that the universal state of high density and temperature that existed long ago occurred because of compression from outside forces, it does not presume a "spherical with planar tendencies" explosion, or indeed any explosion at all.
Take some time and learn about the model.
Seriously. Even if at the end, you think it's complete crap, you still should learn what it is. You cannot criticize it effectively if you don't know what the model actually says. And, as your post indiciates, you don't know what the model actually says.
The point isn't so much that you individually are able to add those features. The point is that if it's a sorely-needed feature, anybody can add that feature. And all the users benefit from it.
No, that's a point; it's not the point. Put another way, what you've written above is a very good argument why free software is a good thing. But saying "free software is a good thing" is very different from saying "nobody should use any software which is non-free, ever" -- a point of view that RMS, and many others, advance, and which is put forward in the op-ed he wrote which is the focus of this article. And that's what we've been discussing in this little sub-thread. My claim is that for many users and organizations, that attitude cannot be acted upon without significant financial sacrifice. And consequently, to expect people/organizations to eschew proprietary software requires that the importance of the freedom to modify software be made so clear that the sacrifice seems worth it. Up to now, that hasn't happened.
> not for something as seemingly esoteric as free software
This is your most salient point.
I agree. I just wanted to deal with the others before getting to that point, in order to boil the situation down to "sometimes, dedication to freedom = going without something; are free software advocates able to influence people's opinions on whether free software is worth the sacrifice?"
The stuff about paying for development... if you can afford several hundred dollars for a Photoshop license, you can afford to contribute to a development fund which will work with a programmer to get certain plug-ins written for the GIMP (or to rewrite the internals, or whatever). Obviously Photoshop did not start out as the program it is now, and it was only the act of people paying for it that allowed it to progress. I think worrying about how the software will get developed is a straw man.
I don't. You're correct that someone who purchases a Photoshop license could instead contribute that money to a development fund, or advertise a feature bounty, or whatever. And maybe in the process, that person can get the featues added to the GIMP that they need . ..in a month. Certainly not by later that afternoon, by which time a morning purchase of Photoshop can be installed; or probably not by a week later, when the presentation to the client is to take place. So the issue of not being able to do the work one's hypothetical client desires is still present.
Which brings us to the issue of persuading people that free software matters -- that "going without," with the potential sacrifices that may entail, is worth it. As you say,
Americans, lately, don't seem wedded to a lot of more obvious forms of freedom. But even if we can find someone who will agree that basic human rights are important, we still need some persuasive arguments about the need for free software.
and I agree with this wholeheartedly. Regarding your Diebold example, I actually keep copies of such news stories on file so that I can show them to people I think worth making an effort to persuade.
If you have a free software but it isn't working well and doesn't do what you exactly need, no matter: you can just fix it because you have the source code. But if you don't know how to program, you can ask some friend of your to do it. If you don't have a programmer friend, you can hire someone to do it. That's all the beauty.
And it sounds great in principle. It's in practice that it runs into trouble. Imagine, for instance, that I'm a freelance graphic designer, or do 3D visualization work, or whatever. And imagine that there are features of Photoshop or Quark or Maya or AVS that aren't available to me in the Gimp or Sodipodi or Blender or OpenDX or whatever (actually, I think the latter two are open source but not free software, but anyway). The suggestion above would be to roll up my sleeves and program in those features. But, in our example, I can't: I'm not a programmer. Nor do I have the time to become one and do that work when all my time is spent doing the actual work for which I get paid.
So then the second answer is to ask a programmer friend. But, even assuming I have said programmer friend, and assuming that programmer friend doesn't have something he/she would rather be doing, these aren't trivial enhancements we're talking about and such functionality will take a while.
So then the next suggestion above is to hire someone. With what money? And how can I justify spending ten times or more the cost of some proprietary software package hiring programmers to improve (or create) a free software competitor? Especially when my hypothetical freelance business probably isn't exactly rolling in the dough.
Well, RMS would say that the justification for spending that money to improve free software options is a dedication to freedom. And if it's really not possible to spend that money on that purpose, because I simply don't have it, then dedication to freedom demands foregoing that proprietary option, and simply doing without that feature set. But in my hypothetical case, that means doing without that client, or that income. So much for my hypothetical business; time to find another way to feed my kids.
My example is contrived, of course. For many (most? dunno.) users of proprietary software, free software alternatives exist that will do everything they want, and do it well. But for many others, that's not true. And telling those users to simply forego doing what they want or need to do as a stand for a cause is a very big request. Of course, people have sacrificed their economic health, and much more, for the cause of freedom before. But not for something as seemingly esoteric as free software; rather, it's been the freedoms accompanying equality of race or gender or religious background under the law.
Until RMS can persuade people that the freedom to modify the software one uses is as important as the freedom to work in the field of your choice without being held back by race or gender or religion, people and businesses are going to have a tough time justifying sacrificing their financial security for that freedom.
Oh, and it shouldn't matter, but just in case it does: I don't have any propriety software installed on my machine, and very little open-source-but-not-free-software stuff as well. I'm not making this post because I don't believe in free software; rather, because I don't think some free software advocates really realize just what big a thing they're asking people to do, and consequently how large a burden of justifying it they have.
I wonder why nobody is talking about a lunar-based telescope. It seems that would give you the best of both worlds: pretty much no atmospheric interference, but with a modicum of gravity so a human crew could be there for extended periods.
Am I just crazy to suggest such a thing?
No, you're not crazy to suggest such a thing; you're crazy for saying that nobody is talking about it, hehe.
Seriously, it does get discussed in the astrophysics community, and there are people who are enthusiastic about it. In the end, it comes down to what you want to spend your money on. Right now, high redshift optical and IR observations are not as limited by atmospheric distortion as they are by the ability to collect a lot of light, which in turn is limited by the collecting area of the telescope. Building your telescope on the Moon wouldn't appreciably change the collecting area required.
With a fixed pot of funds, and the incredible expense of safely lifting the components of a large telescope to the moon, assembling the telescope there, and then operating/maintaining it, the maximum size of your telescope just got a lot smaller. Is what you gain in image resolution by going to the moon worth what you lose in what, and how far away, you can see? Right now, so much of the interesting optical and IR observations are aperture limited, and so most observers' answer to that question is no.
No. The keep adding & adding to the same limited project so the project grows to a 16 Billion monster is bogus.
That's fine. With that, I even agree.
I think there are a lot of fair targets at which to point fingers here. One is, as you suggest above, the way in which the project as a whole became what it did. If in the 80's someone had put the Big Dig (in its current scope) in front of me and made the case for it, I'm sure I would have supported it at some figure (but probably not $16B); I think a strong case can be made for it. But the way in which it developed from its original, much more modest origins, in such a fashion as to make saying "no, that's it" difficult each time, was just wrong.
Then, there's those responsible for the project's duration stretching out so far: from those who kept goosing the scope of the project larger, as above, to those agencies who committed to funding levels in a given year only to not actually provide them, to those responsible for the project management, to the unions who obtained job security for members in the length of the project.
And then, of course, massive corruption in the project management itself (James Kerasiotes, where are you now?).
And all of this, unfortunately but understandably, causes people to forget the good the project does. I've lived for extended periods in Boston, Chicago, Detroit, Louisville, Seattle, SF/Oakland, and Washington, D.C., and I've never seen any stretch of highway as awful in its realization as I-93 through Boston, or any inner city as mucked up by a highway running through it.
The original budge was about 2.5 Billion. They spent 16-18 Billion.
That sir is the very definition of absurd.
Again, the original budget was for the Ted Williams tunnel only, as well as some small improvements to the existing highway system. The two biggest features of the project -- the Central Artery tunnel and the bridge -- weren't proposed in that original budget.
You can fairly say that the project, as a whole, wasn't a worthwhile one. Or, you can fairly say that it would have been a worthwhile one if it had been accomplished for a lot less money. Or, you can say "the original project, at $2.5B, would have been worth it; but the much larger project wouldn't have been even as a more sensible price." All those example statements would have been fair. But to just throw out the $2.5B and $16B figures without context is bogus.
But, that man (saddam) ordered the gasing that killed 5,000 civilians of his own people.
In this comment of yours, you linked to a BBC
story about the gassing of the Kurds in
Halabja. You may be interested to know that
despite the public statements of our President and other major figures of his administration, the U.S. intelligence community suspects that it was Iranian gas that killed the Kurds in Halabja.
See the piece written in the New York Times on January 31, 2003 by Stephen Pelletiere, who wrote:
The accusation that Iraq has used chemical weapons against its own citizens is a familiar part of the debate. The piece of hard evidence most frequently brought up concerns the gassing of Iraqi Kurds at the town of Halabja in March 1988, near the end of the eight-year Iran-Iraq war. President Bush himself has cited Iraq's "gassing its own people," specifically at Halabja, as a reason to topple Saddam Hussein.
But the truth is, all we know for certain is that Kurds were bombarded with poison gas that day at Halabja. We cannot say with any certainty that Iraqi chemical weapons killed the Kurds. This is not the only distortion in the Halabja story.
I am in a position to know because, as the Central Intelligence Agency's senior political analyst on Iraq during the Iran-Iraq war, and as a professor at the Army War College from 1988 to 2000, I was privy to much of the classified material that flowed through Washington having to do with the Persian Gulf. In addition, I headed a 1991 Army investigation into how the Iraqis would fight a war against the United States; the classified version of the report went into great detail on the Halabja affair.
This much about the gassing at Halabja we undoubtedly know: it came about in the course of a battle between Iraqis and Iranians. Iraq used chemical weapons to try to kill Iranians who had seized the town, which is in northern Iraq not far from the Iranian border. The Kurdish civilians who died had the misfortune to be caught up in that exchange. But they were not Iraq's main target.
And the story gets murkier: immediately after the battle, the United States Defense Intelligence Agency investigated and produced a classified report, which it circulated within the intelligence community on a need-to-know basis. That study asserted that it was Iranian gas that killed the Kurds, not Iraqi gas.
The agency did find that each side used gas against the other in the battle around Halabja. The condition of the dead Kurds' bodies, however, indicated they had been killed with a blood agent -- that is, a cyanide-based gas -- which Iran was known to use. The Iraqis, who are thought to have used mustard gas in the battle, are not known to have possessed blood agents at the time.
These facts have long been in the public domain but, extraordinarily, as often as the Halabja affair is cited, they are rarely mentioned. A much-discussed article in The New Yorker last March did not make reference to the Defense Intelligence Agency report or consider that Iranian gas might have killed the Kurds. On the rare occasions the report is brought up, there is usually speculation, with no proof, that it was skewed out of American political favoritism toward Iraq in its war against Iran.
I am not trying to rehabilitate the character of Saddam Hussein. He has much to answer for in the area of human rights abuses. But accusing him of gassing his own people at Halabja as an act of genocide is not correct, because as far as the information we have goes, all of the cases where gas was used involved battles. These were tragedies of war. There may be justifications for invading Iraq, but Halabja is not one of them.
The piece goes on from there. I encourage you to read it.
However, for one, that's only QED, not quantum mechanics in general. It's not like QCD is well tested - at all.
Fair enough -- although, in the case of QCD, the reason for being poorly tested is the difficulty in extracting good predictions out of the theory
(although the lattice gauge simulation folks have been promising much better ones for a long time now). The idea I was reaching for was that, to the extent that we currently extract testable predictions, QM was much better tested than GR.
But then you reminded me that . . .
Certain portions of GR - for instance, the equivalence principle - have been tested ridiculously accurate - 1 part in 10^12, or something like that. Plus, if memory serves, the binary pulsar measurement was ridiculously good in agreement.
. ..which is embarassing because I really should have remembered the binary pulsar observations. I was thinking in terms of perihelion precession and all that stuff and completely forgot about that. Duh.
What if the issue is not so much that the higher dimensions can't be resolved as that we just don't know how to do that yet.
Oh, absolutely; I'd hoped that I'd communicated that possibility in my post. It's quite possible that we just haven't yet been clever enough. Certainly that's the opinion of most string theorists; however beautiful the theory may be, they are physicists and they do want what they're doing to have some relevance to the real world. I hope string theory is right; I think it's cool. But if you're not a string theorist, but have been following string theory over its lifetime, it's hard to be enthusiastic at this point; the string theory community has been saying "observational predictions are right around the corner" for a long time now. That doesn't make them wrong; but, again, it's hard to be enthusiastic.
I heard Greene on NPR's Science Friday He says that some recent work on the theory predicts some effects which may be testable in a few years by the newest generation of "atom smashers" currently under construction at CERN and elsewhere.
We may get to that "falsifiable" stage relatively soon...
Unfortunately, I'm not so optimistic. At least, not in general.
To explain why . ..in string theories, one of the things that has to be explained can be oversimplistically described as "where are all the other spatial dimensions now?" Why are three spatial dimensions macroscopic (effectively, observable by us) and all the others not? In the very early universe/at extremely high energies, all the dimensions should have been equal; but somehow, three of them expanded into the universe we know while the others stayed small. How this is done mathematically is referred to as "compactification" (and for anyone out there who's a math graduate, it's the same compactification of manifolds as you encountered in topology).
Some string theories have, as a result of the compactification, one of the compactified dimensions actually being comparatively large, with a characteristic scale of about a millimeter or a micron or something like that. These "one large dimension" models look like they would have observable consequences for experiments at accessible particle accelerator energies; and so it's possible that such models could be falsified. But that's not the same as falsifying string theory; it's only the possibility of falsifying a class of models within string theory.
It's unfortunate that the article describes GR and QM as being "equally accurate." Presumably that helps dramatize the conflict -- if they're equally accurate, there's no reason to decide whether one of them is a better approximation of reality than the other. That helps the "crisis," as they call it, seem more like a crisis.
But in actuality, of our theories of the four forces, GR is the least well-tested of the four. It seems particularly inappropriate to compare the accuracy of predictions of GR to those of QM, since the predictions of QM have been tested to many more decimal places than those of GR (I think the theoretical prediction of the Lamb shift has been confirmed to something like 8 significant figures now). That's not indicative of a flaw in GR at all -- it merely reflects the fact that doing experimental/observational studies of gravity are really, really hard. But since GR hasn't been examined as well, we can't say that its predictions are equally accurate.
> In order to be taken seriously -- indeed, to even be considered scientific
> -- a physical theory should be falsifiable.
Unless, of course, it happens to be _true_.
I'm not sure whether you meant this reply as a joke or not; the moderation suggests so, and perhaps my humor detector is even worse-off than it usually is. But it seems possible to me that your reply is serious, so (being both a physicist and an educator) I can't help myself . . .
Perhaps the most widely misunderstood property of modern science is that no proposition, no scientific theory, is ever proved to be absolutely true. No matter how much evidence you accumulate in favor of some theory or model, there's always the possibility that next week someone's going to come up with an experimental or observational result that requires that theory's revision or even outright rejection. Scientific theories can only be proven false; they can never be proved true.
"Yeah, yeah," you might be saying, "but I wasn't talking about whether theories can be proved true or not; I was talking about whether or not a theory actually is true. After all, even if we can't ever know with 100% certainty that a particular theory is true, it may still be true." Yes, indeed. But that's irrelevant to my original point, the one to which you replied. Since we cannot ever know with certainty whether any theory we put forward is absolutely true, and thus any theory is always subject to scrutiny, our requirement that the theory be falsifiable -- that it be possible to conceive of an experimental or observational result which would rule the theory out -- still stands.
The thing I find funny about critics of string theory is their objection to the idea that there can be multiple dimensions beyond the three dimensions people can perceive.
Who fits that description, though? I know lots and lots of theorists in elementary particles and fields who are critics of string theory, but not for that reason. Indeed, it'd be odd if so, since mainstream particle theorists have been building models incorporating additional "dimensions" since the 1950s (e.g. isospin models in particle and nuclear physics).
The real criticism of string theory is much more fundamental. In order to be taken seriously -- indeed, to even be considered scientific -- a physical theory should be falsifiable. There should be some experiment I can do or observation I can make where, if it doesn't come out the way the theory says, then the theory is wrong. But since string theory describes the nature of things at energies around the Planck scale -- 19 orders of magnitude greater than the mass of the proton,
or 16 orders of magnitude higher than the best particle accelerators we've built -- how do you test the theory? String theorists say that they simply haven't been clever enough yet to figure out how to make unique predictions at potentially experimentally accessible energies, but that they will be; and maybe they're right. I hope they're right, because string theory is beautiful in a lot of ways (at one point, I wanted to do string theory). But they've been saying that for 20 years now, since Green (no relation), Schwarz and Witten's stuff.
Slashdot Mirror
> and whose to say that the Universe doesn't oscillate?
That possibility is still definitely on the table, but it's losing support.
It has almost no support in the mainstream cosmological community, and hasn't for quite a while.
A universe that slows, stops, and falls back in a "Big Crunch" is a negative curvature universe. A universe that expands infinitely is a positive curvature universe. Between them you have a precise zero-point, a "flat" zero curvature universe where the expansion rate slows infinitely close to zero.
Actually, this is backwards. Traditionally, it's been positively curved universes that recollapse, while negatively curved universes converge towards a free expansion where the expansion scales linearly with time (that is, as the age of the Universe doubles, everything expands by a factor of two). So that's backwards. But also, in that traditional view, flat universes expand infinitely as well; they simply asymptotically approach (but never quite reach) an end to the expansion (I think you were trying to say that, but I wanted to make it clear).
But importantly, this view has neglected the possibility of a nonzero vacuum energy, or cosmological constant. That's why I used the adverb "traditionally" above -- traditionally, we've assumed there to be no vacuum energy, and set the cosmological constant to zero. We now have significant observational evidence that this was wrong. In the presence of a cosmological constant, it's no longer possible to simply say "negative curvature = expands forever, zero curvature = expands forever but asymptotically approaches stopping, positive curvature = recollapse." Those simple relations between curvature and fate no longer hold if there's a cosmological constant. It's true that the energy content of the Universe drives the time-evolution of its expansion; it's also true that the energy content of the Universe determines its curvature. But the presence of a cosmological constant changes the Friedmann equations in such a way that that simplistic correlation between curvature and how the expansion will proceed no longer holds true. This is illustrated by the apparent situation with our own Universe (see below).
There are very strong theoretical reasons to think that the universe has exactly zero curvature - precisely on the balancing point. On the other hand recent observations seem to suggest accelerating expansion, possibly runaway positive curvature taht would eventually rip apart everything - the Earth, atoms, even protons.
Actually, we have strong observational evidence that the Universe is flat (that is, has zero curvature), from observations of the primary anisotropies in the cosmic microwave background. At the same time, you're correct that recent observations indicate an acceleration to the expansion. But this is not contradictory when a vacuum energy exists. In fact, a vacuum energy is the only way to get an accelerating expansion; a negative curvature universe with no cosmological constant does expand infinitely, but that expansion does not accelerate.
OK, here's a batch more response. I hope this is interesting . . .
The temperature of the cosmic background radiation was a retrodiction, not a prediction. Alpher and Herman got the closest, with a prediction of 5 Kelvins, but what you don't often hear is that the prediction was later adjusted to 28 Kelvins.
This is pretty commonly brought up by proponents of alternative cosmologies. I've had discussions with proponents of several in the past, and this frequently gets mentioned. It's unfortunate, because most people realize that this is pretty much a red herring. No prediction of the cosmic microwave background's blackbody temperature prior to the CMBR's discovery was ever thought very likely correct, since making the prediction required as mathematical input other cosmological parameters which had not yet been measured with any precision at all. The mere existence of the microwave background, and that it should be so uniform and such an incredibly good blackbody (at this point, the best blackbody ever observed anywhere) were the real predictions; and their success actually is pretty impressive -- more impressive than they might seem at first glance.
To elaborate . . .we know what temperature the background radiation would have had to be at at the time of decoupling/recombination, just because of atomic physics. In order to predict what the temperature is now, one has to know how much the Universe has expanded since then. How do you know that? How do you
know how much the Universe has expanded since recombination? (phrased differently, how do we know what the redshift of the surface of last scattering is?) We
know it now from the current microwave background temperature; but that's of course pretty useless if what you're trying to do is predict the current CMBR temperature. Well, there are ways you can guess. For instance, if you think
you know that the Universe is flat, and that the contribution from vacuum energy is zero; and presuming you know what the Hubble constant is now; and presuming
you know what the energy density of the Universe in matter is now; and given the fact that you know what the radiation energy density had to have been at recombination (because you know what its temperature had to be, from atomic physics);
from these things, you can calculate what the microwave background temperature now ought to be.
How well do you think those things were known then?
And suggesting that that implies a mark against the Big Bang model makes no logical sense. It would be analogous to the following: suppose I'm building a circuit from scratch, having first designed it using what I know of circuit theory from classical electromagnetism. I build it, and my circuit doesn't work as I expected. I then learn that the dielectric constant I'd assumed for a material I used in my homemade capacitors was wrong, and consequently I'd figured them to have a different capacitance than what they actually had when I built them . . .so of course my circuit didn't work like I thought it would. Apparently, the people who find fault with early guesses at the current CMBR temperature would conclude that the failure of my circuit indicates that circuit theory is incorrect;
but that's false. Like circuit theory, the Big Bang model establishes mathematical relationships between physical parameters of the system it describes. Put the wrong values into the equations, and you'll get wrong values out, which then
won't match subsequent observations. Of course, with what we know now of the cosmological parameters, everything is perfectly consistent, without any tweaking
of the Big Bang model whatsoever.
It is the mere existence of the microwave background -- its omnidirectional uniformity and amazing blackbody spectrum -- that is the prediction of interest. And contrary to assertions from people, these are extremely hard to contrive in other ways. Such alternative sources for the CMBR typically involve a local origin, in
First of all, thanks for coming in with some specifics. Not that I agree with them, but at least now there are things which are not vaguaries to which I can respond.
Unfortunately, responding adequately is going to take a lot of time and a lot of space. I don't know who's still reading this at this point, but I'm going to have to do this over several replies and over time. I hope that's OK.
The "flat universe" case gives a Hubble constant of 65 km/s/Mpc (megaparsec). This amounts to an age of the universe of ~10 billion years. This is one of the "age paradoxes" that have led to some of the more interesting revisions and proposed revisions.
No, this is a false representation of things. It is not the case that an assumption of a flat universe requires a Hubble parameter of 65 km/s/Mpc; it is not the case that a flat universe with a Hubble parameter of 65 km/s/Mpc necessarily indicates an age of 10 Gyr. There was an "age problem" at one point -- a discrepancy between the age of some of the oldest objects in the Universe (globular clusters) with the age of the Universe inferred from its expansion -- but that problem has been resolved, and without any revision to the Big Bang model at all.
To elaborate:
In the Big Bang model, estimating the age of the Universe through the expansion is possible because the age is functionally related to three things: the Hubble parameter; the large-scale geometry of space (the curvature), induced by the mean energy density; and the relative contributions to the mean energy density from components which scale differently with the expansion of the Universe (e.g. radiation, which scales inversely with the fourth power of the expansion; matter, which scales inversely with the third power of the expansion, and vacuum energy/cosmological constant, which does not change with the expansion). Knowledge of all of these things is required to make a prediction of the age of the Universe from the expansion.
It's true that through the 80's and much of the 90's, there was a perception that there was an age problem: globular cluster ages were suggesting you needed the Universe to have been around for as much as 15 Gyr; requiring an expansion age at least that long seemed (based on what we knew of the other parameters) to require a Hubble parameter as low as 50 km/s/Mpc, which observations did not favor. But in the last 7-8 years, three observational results have occurred which have caused the age problem to disappear. Note that I said observational; no adjustment of the Big Bang model was involved at all.
The first observational result was the lowering of globular cluster ages estimated from observations. This occurred for a number of reasons, the most significant of which was the recalibration of the distance ladder that came from better parallax distance measures to local reference stars from the Hipparcos satellite. Hipparcos observations determined that local reference stars were about 10% farther away than previously thought; this increased the distances to globular clusters, and therefore the luminosities of main sequence turnoff on their HR diagrams. By the summer of 1998, the globular cluster folks were going to conferences quoting maximum ages of just above 13 Gyr.
The second observational result was the lowering of estimates of the Hubble parameter that also came from recalibrations of the distance ladder, which in turn came from two things: the Hipparcos results mentioned previously; and the excellent observations of Cepheid variables that were the main objective of the Hubble Key Project. These brought the observed value of the Hubble parameter down from its previously favored value of around 75 km/s/Mpc or so to values of 65-67 km/s/Mpc, increasing ages estimated through the expansion by 11-15%. These two results dealt with much of the discrepancy between the two ages, but did not resolve it completely.
The third observational result was a dramatic improvement in the determination of th
Well, the BB story has gone along for so much time... some new data whacks it, ok... small nudge and it's consistent.
Can you give an example?
Some new research threatens boatloads of papers, ok... mop it under the rug.
Can you give an example?
Average, uninitiated scientists can't make heads or tails of the nasty slew of hypotherical particles and their family relations (that HAS to be true because it fits the model!)... oh, they're just ignorant.
The Big Bang model makes no predictions whatsoever about the existence of any hypothetical particles, let alone a "nasty slew." The only particles required to be present for the Big Bang model to make accurate predictions are those expected to still be relativistic at the time of Big Bang Nucleosynthesis: namely, the three families of baryons and leptons that we've already detected in experiments here on Earth. In fact, when the BBN calculations were first done, it was discovered that the predictions only made sense if there were three or fewer families of fundamental particles. At that time, we only knew of two for sure. We've since discovered the third in particle accelerators, and measurements of the decay width of the Z0 particle 13 years ago confirmed that no more than three such families could exist. So, contrary to your statement, the Big Bang model not only doesn't predict a "nasty slew of hypothetical particles," but at this point it doesn't predict any hypothetical particles at all, and indeed sets a limit on how many light ones can exist.
It looks to me like you don't know what the Big Bang model actually says. And it looks to me like you don't know what's not the Big Bang model -- that is, what are other ideas that are taken seriously as part of the standard cosmology but are not part of the Big Bang model itself because they deal with cosmological topics that the Big Bang model does not directly address.
Hmm, I've grocked EM and some quantum physics (the basics: Schroedinger, Fermi and the avg undergraduate stuff in a Solid State Phy course) and never got the Alice in Wonderland feeling.
Really? Wow. One of the reasons I loved quantum so much, through undergrad and grad school, was how something that seemed so "Alice in Wonderland"-y to me could be so solidly borne out by experiment. I mean, tunnelling through potential barriers? Come on. But amazingly enough, the answers come out right.
You might argue that modern cosmology can account for all the data (or just give it enough time and it will) but anyone can shoehorn a dataset in a model... just add some epicycles, a nudge here, a constant there... it'll all fit.
But can you give me some examples of how this has gone on, with respect to the Big Bang model?
Our cosmological understanding has undergone a tremendous amount of change in the last 20-25 years, as cosmology has gone from a data-starved science to a data-rich one. Lots of ideas have been put forward, "tweaked" (as you say), shot down, resuscitated, etc. None of that has to do with the Big Bang model. People have definitely tried to massage pet theories when data has come in that didn't quite fit (the topological defect folks -- cosmic strings, etc. -- come to mind); but those theories were not the Big Bang model.
It really seems to me like you don't know, of the set of ideas that make up the standard cosmology and those additional ideas that are taken seriously but not yet fully accepted, what's part of the Big Bang model and what isn't. The popular press carries some of the blame for this -- the phrase "the Big Bang model" is all the cosmology most newspaper science writers know, so when results have challenged cosmological orthodoxy, they've sometimes been described as challenges to the Big Bang model, even though in actuality they've typically said nothing whatsoever one way or the other about the Big Bang model.
So, I just wished these guys p
> Yes, and no: depending on who you talk to, and the definition of Universe.
> The best one I can come up with is "all space which is connected (in a
> mathematical sense) and includes me at the present time". In that sense,
> regions of black holes are another Universe, for instance.
>
> There are other statements like "the Universe is everything that can be observed",
> which is a much more limiting definition (fundamentally, there's a ton of
> spacetime outside all of humanity's forward and backward light cones), or "the
> Universe is everything", which, well, pretty much occludes all "outside"-ness,
> because as soon as you find something outside, it's not outside. Oookay.
Is it meaningful to talk about the portions of the universe that are outside our light cones as being mathematically connected to us? You can say that they were, but not that they are. There's no such thing as an instantaneous "now" snapshot of the universe, just a snapshot of the current surface of the backwards light cone. In practice, "everything that I can observe" and "everything that is connected to me" refer to the same thing.
I shouldn't speak for the poster to whom you were replying, but I'm pretty sure that he was using the phrase "mathematically connected" in a topological sense, rather than referring to causal connection. If one meant connected in a causal sense, then you're absolutely correct that that means the backwards light cone by definition, and therefore means what I can observe. But you can also talk about the topology of space, and whether the Universe is simply connected, connected, etc. I think that's how it was meant; and that definition is different from what's observable.
It's just yet-another-inconsistency in the n-th hack to the BB theory introduced to clean up previous gripes.
Can you be more specific? What's the inconsistency here, with what is it inconsistent, and how does that inconsistency speak to the Big Bang model as a whole, specifically? I'm not saying you're wrong (yet); I just can't address your statement directly because it's too vague.
There are without question unsolved problems in cosmology (thank heavens; otherwise, cosmologists would have little to do). I'm interested in your careful argument as to why those problems cannot be solved in the context of the Big Bang model, and therefore falsify it. To me, it seems like you're saying "Since we don't understand how tornadoes form, it's time to realize that the `spherical Earth' model is a failure." That analogy probably seems silly to you, since we have lots of evidence to support the idea of a (nearly) spherical Earth. But we have lots of evidence that supports the Big Bang model as well, including non-trivial advance predictions borne out by subsequent observation.
The Big Bang model will be falsified if and when a prediction it makes is shown to be false. But that hasn't happened here: the Big Bang model does not make predictions about the specifics of the mass distribution or galaxy formation. Those are topics of importance in cosmology, but they do not directly speak to the veracity of the Big Bang model. Only if the general constraints the Big Bang model places upon galaxy formation are such that these observations should be impossible is there a problem for the Big Bang. Nobody's shown this to be true.
It is true that these observations, if correct, pose a challenge to the standard cosmological model. But there's more to the standard cosmological model than just the Big Bang model.
> This surprise has nothing to do with distance from the "center" of the big bang,
> since there is no center
I've heard this before, and although I don't disagree with it, I've never been able to wrap my brain around it. It seems to me that any explosion has a center, or a point of origin. Even one that expands out into "nothing" like the Big Bang did/is.
This is, unfortunately, a flaw in the name of the model. It conjures up the idea of an explosion of material into surrounding empty space, which is not what the Big Bang model describes. The expansion of the Universe is an expansion of space itself. The galaxies grow farther apart not because they are moving away from each other through space, but because space itself is expanding between them.
Not that that necessarily makes things easier for you. Fundamentally, this points out a failure of one of our most useful way of understanding thimgs: to relate them to things we already understand, or with which we are already familiar. For instance, when authors of cosmology books for laypersons construct analogies to the expansion of space and the resulting increasing separation of the galaxies, they use things like a loaf of raisin bread expanding in the oven. But that analogy is flawed: the raisin bread has space surrounding it into which it can expand (not to mention a "center"), while no such thing exists for the universe.
A better analogy in that it gets rid of the embedded center is to give up our 3D universe, and instead consider the 2D surface of an inflating balloon. Dots (galaxies) painted on the balloon's surface are all getting farther and farther apart from each other on the surface of the balloon (in space), but no place on the surface of the balloon (no location in the Universe) can be called the center of the expansion (the one place from which things started expanding apart). But this analogy is a bad one, as well. It makes an assumption about the topology of the universe (that it loops around on itself, or is "closed"); the Universe may be that way, but it need not be. More importantly, this analogy requires the existence of a 3rd dimension (the radial direction) separate from the 2D surface of the balloon; a change in the position of the surface of the balloon with time in that radial direction describes the expansion. But the Big Bang model doesn't require such a hidden dimension which is driving the expansion.
There just isn't something from our day-to-day lives which provides a decent analogy to the expansion of the Universe. It has to be understood on its own terms, without recourse to simple visualization. Not that this is uncommon in physics since the beginning of the 20th Century; for instance, quantum mechanics describes phenomena which are difficult to impossible to describe in terms of how things work in our common sense, everyday world. In the end, it comes down to a quote from (I think) Feynman (although he was talking about quantum mechanics at the time): "I don't know how to describe it in terms of something you're more familiar with, because I don't understand it in terms of something you're more familiar with."
The NASA page on this quotes a redshift of 2.38. Do they say how they got it? Did they take full spectra from all these objects? Are some of them Lyman break galaxies? Are any of the redshifts photometric rather than spectroscopic?
Actually, the most straightforward explanation is that galaxies form differently than we think. Considering we have no evidence to the contrary (all we have are simulations), and we do have a fair amount of evidence on the value of the Hubble constant, and therefore an estimate of the age of the Universe, the theory that requires the least changes in the current model would be that galaxies form quicker, and differently, than current theory allows.
I can't make up my mind whether this is the most straightforward explanation or not. It's true that we have very little observational data about galaxy formation. And I don't put too much stock into the semi-empirical galaxy formation models (e.g. the Kauffman et. al. stuff); too many ways to tweak them. But at the same time, you're constrained in what you can do in the Universe before decoupling by anisotropy observations, while the tiny value of the Compton y-parameter in the CBR constrains pushing stuff around by energy imput after decoupling.
I want to think that this is just some outlier, or simply a redshift-space distortion, or something like that. But I'm sure that someone somewhere has already done a calculation of the statistics of peaks in Gaussian random fields to show that it'd be ridiculously improbable even as an outlier (in the first case), or that the growing mode at that redshift should still be so small that enough organized large-scale mass to induce sufficient peculiar velocities necessary to produce such a redshift-space distortion through infall would again be absurdly improbable (in the second case).
As any good evolutionist knows , after the "Big Bang" all the matter in the universe, which had been compressed (through forces and mechanisms unknowable) into a very tiny ball, exploded outward (spherically, with planar tendencies) with tremendous force.
This observation of thousands of galaxies SO FAR OUT from the assumed center of the "Big Bang"
(snip)
Your criticisms would carry more weight if they demonstrated that you understood the relativistic hot Big Bang model at all. The Big Bang model does not presume any very tiny ball, it does not presume that the universal state of high density and temperature that existed long ago occurred because of compression from outside forces, it does not presume a "spherical with planar tendencies" explosion, or indeed any explosion at all.
Take some time and learn about the model. Seriously. Even if at the end, you think it's complete crap, you still should learn what it is. You cannot criticize it effectively if you don't know what the model actually says. And, as your post indiciates, you don't know what the model actually says.
The point isn't so much that you individually are able to add those features. The point is that if it's a sorely-needed feature, anybody can add that feature. And all the users benefit from it.
No, that's a point; it's not the point. Put another way, what you've written above is a very good argument why free software is a good thing. But saying "free software is a good thing" is very different from saying "nobody should use any software which is non-free, ever" -- a point of view that RMS, and many others, advance, and which is put forward in the op-ed he wrote which is the focus of this article. And that's what we've been discussing in this little sub-thread. My claim is that for many users and organizations, that attitude cannot be acted upon without significant financial sacrifice. And consequently, to expect people/organizations to eschew proprietary software requires that the importance of the freedom to modify software be made so clear that the sacrifice seems worth it. Up to now, that hasn't happened.
> not for something as seemingly esoteric as free software
This is your most salient point.
I agree. I just wanted to deal with the others before getting to that point, in order to boil the situation down to "sometimes, dedication to freedom = going without something; are free software advocates able to influence people's opinions on whether free software is worth the sacrifice?"
The stuff about paying for development... if you can afford several hundred dollars for a Photoshop license, you can afford to contribute to a development fund which will work with a programmer to get certain plug-ins written for the GIMP (or to rewrite the internals, or whatever). Obviously Photoshop did not start out as the program it is now, and it was only the act of people paying for it that allowed it to progress. I think worrying about how the software will get developed is a straw man.
I don't. You're correct that someone who purchases a Photoshop license could instead contribute that money to a development fund, or advertise a feature bounty, or whatever. And maybe in the process, that person can get the featues added to the GIMP that they need . . .in a month. Certainly not by later that afternoon, by which time a morning purchase of Photoshop can be installed; or probably not by a week later, when the presentation to the client is to take place. So the issue of not being able to do the work one's hypothetical client desires is still present.
Which brings us to the issue of persuading people that free software matters -- that "going without," with the potential sacrifices that may entail, is worth it. As you say,
Americans, lately, don't seem wedded to a lot of more obvious forms of freedom. But even if we can find someone who will agree that basic human rights are important, we still need some persuasive arguments about the need for free software.
and I agree with this wholeheartedly. Regarding your Diebold example, I actually keep copies of such news stories on file so that I can show them to people I think worth making an effort to persuade.
If you have a free software but it isn't working well and doesn't do what you exactly need, no matter: you can just fix it because you have the source code. But if you don't know how to program, you can ask some friend of your to do it. If you don't have a programmer friend, you can hire someone to do it. That's all the beauty.
And it sounds great in principle. It's in practice that it runs into trouble. Imagine, for instance, that I'm a freelance graphic designer, or do 3D visualization work, or whatever. And imagine that there are features of Photoshop or Quark or Maya or AVS that aren't available to me in the Gimp or Sodipodi or Blender or OpenDX or whatever (actually, I think the latter two are open source but not free software, but anyway). The suggestion above would be to roll up my sleeves and program in those features. But, in our example, I can't: I'm not a programmer. Nor do I have the time to become one and do that work when all my time is spent doing the actual work for which I get paid.
So then the second answer is to ask a programmer friend. But, even assuming I have said programmer friend, and assuming that programmer friend doesn't have something he/she would rather be doing, these aren't trivial enhancements we're talking about and such functionality will take a while.
So then the next suggestion above is to hire someone. With what money? And how can I justify spending ten times or more the cost of some proprietary software package hiring programmers to improve (or create) a free software competitor? Especially when my hypothetical freelance business probably isn't exactly rolling in the dough.
Well, RMS would say that the justification for spending that money to improve free software options is a dedication to freedom. And if it's really not possible to spend that money on that purpose, because I simply don't have it, then dedication to freedom demands foregoing that proprietary option, and simply doing without that feature set. But in my hypothetical case, that means doing without that client, or that income. So much for my hypothetical business; time to find another way to feed my kids.
My example is contrived, of course. For many (most? dunno.) users of proprietary software, free software alternatives exist that will do everything they want, and do it well. But for many others, that's not true. And telling those users to simply forego doing what they want or need to do as a stand for a cause is a very big request. Of course, people have sacrificed their economic health, and much more, for the cause of freedom before. But not for something as seemingly esoteric as free software; rather, it's been the freedoms accompanying equality of race or gender or religious background under the law.
Until RMS can persuade people that the freedom to modify the software one uses is as important as the freedom to work in the field of your choice without being held back by race or gender or religion, people and businesses are going to have a tough time justifying sacrificing their financial security for that freedom.
Oh, and it shouldn't matter, but just in case it does: I don't have any propriety software installed on my machine, and very little open-source-but-not-free-software stuff as well. I'm not making this post because I don't believe in free software; rather, because I don't think some free software advocates really realize just what big a thing they're asking people to do, and consequently how large a burden of justifying it they have.
I wonder why nobody is talking about a lunar-based telescope. It seems that would give you the best of both worlds: pretty much no atmospheric interference, but with a modicum of gravity so a human crew could be there for extended periods.
Am I just crazy to suggest such a thing?
No, you're not crazy to suggest such a thing; you're crazy for saying that nobody is talking about it, hehe.
Seriously, it does get discussed in the astrophysics community, and there are people who are enthusiastic about it. In the end, it comes down to what you want to spend your money on. Right now, high redshift optical and IR observations are not as limited by atmospheric distortion as they are by the ability to collect a lot of light, which in turn is limited by the collecting area of the telescope. Building your telescope on the Moon wouldn't appreciably change the collecting area required.
With a fixed pot of funds, and the incredible expense of safely lifting the components of a large telescope to the moon, assembling the telescope there, and then operating/maintaining it, the maximum size of your telescope just got a lot smaller. Is what you gain in image resolution by going to the moon worth what you lose in what, and how far away, you can see? Right now, so much of the interesting optical and IR observations are aperture limited, and so most observers' answer to that question is no.
No. The keep adding & adding to the same limited project so the project grows to a 16 Billion monster is bogus.
That's fine. With that, I even agree.
I think there are a lot of fair targets at which to point fingers here. One is, as you suggest above, the way in which the project as a whole became what it did. If in the 80's someone had put the Big Dig (in its current scope) in front of me and made the case for it, I'm sure I would have supported it at some figure (but probably not $16B); I think a strong case can be made for it. But the way in which it developed from its original, much more modest origins, in such a fashion as to make saying "no, that's it" difficult each time, was just wrong.
Then, there's those responsible for the project's duration stretching out so far: from those who kept goosing the scope of the project larger, as above, to those agencies who committed to funding levels in a given year only to not actually provide them, to those responsible for the project management, to the unions who obtained job security for members in the length of the project.
And then, of course, massive corruption in the project management itself (James Kerasiotes, where are you now?).
And all of this, unfortunately but understandably, causes people to forget the good the project does. I've lived for extended periods in Boston, Chicago, Detroit, Louisville, Seattle, SF/Oakland, and Washington, D.C., and I've never seen any stretch of highway as awful in its realization as I-93 through Boston, or any inner city as mucked up by a highway running through it.
The original budge was about 2.5 Billion. They spent 16-18 Billion.
That sir is the very definition of absurd.
Again, the original budget was for the Ted Williams tunnel only, as well as some small improvements to the existing highway system. The two biggest features of the project -- the Central Artery tunnel and the bridge -- weren't proposed in that original budget.
You can fairly say that the project, as a whole, wasn't a worthwhile one. Or, you can fairly say that it would have been a worthwhile one if it had been accomplished for a lot less money. Or, you can say "the original project, at $2.5B, would have been worth it; but the much larger project wouldn't have been even as a more sensible price." All those example statements would have been fair. But to just throw out the $2.5B and $16B figures without context is bogus.
But, that man (saddam) ordered the gasing that killed 5,000 civilians of his own people.
In this comment of yours, you linked to a BBC story about the gassing of the Kurds in Halabja. You may be interested to know that despite the public statements of our President and other major figures of his administration, the U.S. intelligence community suspects that it was Iranian gas that killed the Kurds in Halabja. See the piece written in the New York Times on January 31, 2003 by Stephen Pelletiere, who wrote:
The piece goes on from there. I encourage you to read it.
Do we have the money to fund this?
Of course not.
We need to do it but I don't know if we can afford it.
We need to do it at some point. Do we need to do it right now? Of course not.
Well, I don't know how to tell what songs will be popular. But, obviously, this topic is popular.
Oof.
However, for one, that's only QED, not quantum mechanics in general. It's not like QCD is well tested - at all.
Fair enough -- although, in the case of QCD, the reason for being poorly tested is the difficulty in extracting good predictions out of the theory (although the lattice gauge simulation folks have been promising much better ones for a long time now). The idea I was reaching for was that, to the extent that we currently extract testable predictions, QM was much better tested than GR.
But then you reminded me that . . .
Certain portions of GR - for instance, the equivalence principle - have been tested ridiculously accurate - 1 part in 10^12, or something like that. Plus, if memory serves, the binary pulsar measurement was ridiculously good in agreement.
. . .which is embarassing because I really should have remembered the binary pulsar observations. I was thinking in terms of perihelion precession and all that stuff and completely forgot about that. Duh.
What if the issue is not so much that the higher dimensions can't be resolved as that we just don't know how to do that yet.
Oh, absolutely; I'd hoped that I'd communicated that possibility in my post. It's quite possible that we just haven't yet been clever enough. Certainly that's the opinion of most string theorists; however beautiful the theory may be, they are physicists and they do want what they're doing to have some relevance to the real world. I hope string theory is right; I think it's cool. But if you're not a string theorist, but have been following string theory over its lifetime, it's hard to be enthusiastic at this point; the string theory community has been saying "observational predictions are right around the corner" for a long time now. That doesn't make them wrong; but, again, it's hard to be enthusiastic.
I heard Greene on NPR's Science Friday He says that some recent work on the theory predicts some effects which may be testable in a few years by the newest generation of "atom smashers" currently under construction at CERN and elsewhere.
We may get to that "falsifiable" stage relatively soon...
Unfortunately, I'm not so optimistic. At least, not in general.
To explain why . . .in string theories, one of the things that has to be explained can be oversimplistically described as "where are all the other spatial dimensions now?" Why are three spatial dimensions macroscopic (effectively, observable by us) and all the others not? In the very early universe/at extremely high energies, all the dimensions should have been equal; but somehow, three of them expanded into the universe we know while the others stayed small. How this is done mathematically is referred to as "compactification" (and for anyone out there who's a math graduate, it's the same compactification of manifolds as you encountered in topology).
Some string theories have, as a result of the compactification, one of the compactified dimensions actually being comparatively large, with a characteristic scale of about a millimeter or a micron or something like that. These "one large dimension" models look like they would have observable consequences for experiments at accessible particle accelerator energies; and so it's possible that such models could be falsified. But that's not the same as falsifying string theory; it's only the possibility of falsifying a class of models within string theory.
It's unfortunate that the article describes GR and QM as being "equally accurate." Presumably that helps dramatize the conflict -- if they're equally accurate, there's no reason to decide whether one of them is a better approximation of reality than the other. That helps the "crisis," as they call it, seem more like a crisis.
But in actuality, of our theories of the four forces, GR is the least well-tested of the four. It seems particularly inappropriate to compare the accuracy of predictions of GR to those of QM, since the predictions of QM have been tested to many more decimal places than those of GR (I think the theoretical prediction of the Lamb shift has been confirmed to something like 8 significant figures now). That's not indicative of a flaw in GR at all -- it merely reflects the fact that doing experimental/observational studies of gravity are really, really hard. But since GR hasn't been examined as well, we can't say that its predictions are equally accurate.
> In order to be taken seriously -- indeed, to even be considered scientific
> -- a physical theory should be falsifiable.
Unless, of course, it happens to be _true_.
I'm not sure whether you meant this reply as a joke or not; the moderation suggests so, and perhaps my humor detector is even worse-off than it usually is. But it seems possible to me that your reply is serious, so (being both a physicist and an educator) I can't help myself . . .
Perhaps the most widely misunderstood property of modern science is that no proposition, no scientific theory, is ever proved to be absolutely true. No matter how much evidence you accumulate in favor of some theory or model, there's always the possibility that next week someone's going to come up with an experimental or observational result that requires that theory's revision or even outright rejection. Scientific theories can only be proven false; they can never be proved true.
"Yeah, yeah," you might be saying, "but I wasn't talking about whether theories can be proved true or not; I was talking about whether or not a theory actually is true. After all, even if we can't ever know with 100% certainty that a particular theory is true, it may still be true." Yes, indeed. But that's irrelevant to my original point, the one to which you replied. Since we cannot ever know with certainty whether any theory we put forward is absolutely true, and thus any theory is always subject to scrutiny, our requirement that the theory be falsifiable -- that it be possible to conceive of an experimental or observational result which would rule the theory out -- still stands.
The thing I find funny about critics of string theory is their objection to the idea that there can be multiple dimensions beyond the three dimensions people can perceive.
Who fits that description, though? I know lots and lots of theorists in elementary particles and fields who are critics of string theory, but not for that reason. Indeed, it'd be odd if so, since mainstream particle theorists have been building models incorporating additional "dimensions" since the 1950s (e.g. isospin models in particle and nuclear physics).
The real criticism of string theory is much more fundamental. In order to be taken seriously -- indeed, to even be considered scientific -- a physical theory should be falsifiable. There should be some experiment I can do or observation I can make where, if it doesn't come out the way the theory says, then the theory is wrong. But since string theory describes the nature of things at energies around the Planck scale -- 19 orders of magnitude greater than the mass of the proton, or 16 orders of magnitude higher than the best particle accelerators we've built -- how do you test the theory? String theorists say that they simply haven't been clever enough yet to figure out how to make unique predictions at potentially experimentally accessible energies, but that they will be; and maybe they're right. I hope they're right, because string theory is beautiful in a lot of ways (at one point, I wanted to do string theory). But they've been saying that for 20 years now, since Green (no relation), Schwarz and Witten's stuff.