Want to read Slashdot from your mobile device? Point it at m.slashdot.org and keep reading!

 



Forgot your password?
typodupeerror
Compare cell phone plans using Wirefly's innovative plan comparison tool ×

Comment Re:I don't get it (Score 1) 130

It's like this. A dedicated construction robot eats sunlight, and breathes vacuum, or air, or H2 gas, or N2 or O2 gas as you ask. It, like honey badger, just don't care, as long as its batteries have time enough to recharge before its work shift. It can stay up in space for months or years without its bones deteriorating. Properly engineered, it is likely to survive all but the worst solar storms by just powering down and waking up again afterwards. It might even be able to repair itself, or if there were two, repair each other. And finally, if it "dies" for some reason the only loss is money -- no grieving relatives or national flag at half mast.

Also, there is little reason for a crew to be there before they are needed, and they might only end up being needed to move into the space habitat once it is constructed. I'm not religious about whether humans should or should not go into space -- I grew up reading Heinlein, Asimov, etc and think it would be lovely if they did, but then I learned physics and a certain amount of economics and a whole lot of computer science and programming and all I can say now is that robots make a whole lot more economic sense unless or until we are ready to make a serious commitment, such as building a large, permanent, 50's sci-fi style rotating space station at a lagrange point or in geosync orbit and sending people up to LIVE there, or LIVE on the moon. And that commitment would be extraordinarily expensive, and we haven't even taken care of business down here on Earth, such as ending world hunger and poverty and war so we can get on with trans-global progress and space.

Ten years ago, maybe, the possibility of robots doing all of the work might have still been fantasy, but at this point between AI robots and remote controlled drone robots, I doubt that there is much we cannot accomplish in space without risking human lives or spending the incredibly large multiplier on the amount of money required to do ANYTHING we want to do in space.

So at the very least I imagine it will end up making a lot more sense to build nearly everything with robots, even if humans do eventually come in to do their human "time for human judgement and creativity" thing, do things that are difficult to impossible to do remotely. And it isn't clear how large a set that will, ultimately, end up being. Even colonizing the stars seems a lot more likely to take place by sending our genetic instructions and raw materials and building an ecosystem from the ground up using robots as opposed to physically sending humans between the stars. We could afford to do ten colony starships of the former kind for one of the latter, if not more, and either way the original humans that leave the earth are not going to be the ones that first set foot on a planet circling another star...

rgb

Comment Re:I don't get it (Score 1) 130

Sure, pressure tested with HYDROGEN. Believe me, anything that holds hydrogen at 68 atmospheres should hold O2 at less than 1 (given the huge difference in molecular size), but yes, this is absolutely one of the design issues as the SV tank was designed to be loaded and then vent to hold the design pressure until launch, not hold H2 inside for weeks. Another one is that the tank itself only is structurally rigid enough to survive launch BECAUSE it is loaded with an enormous internal pressure, which makes the walls essentially rigid. OTOH even 1 atmosphere exerts 10^5 newtons per square meter, which seems enough to ensure substantial structural rigidity against far, far smaller thrusts. But still has to worry about whether or not it will substantially deform or rip if rorqued or dinged with an atmosphere inside and vacuum outside and somebody kicks a wall or hits it with a hammer or punctures it with a micrometeor, whether hydrogen embrittlement will occur in the comparatively short time it is loaded with hydrogen under pressure, whether (loaded) it can sustain unevenly applied end forces or torques, and so on. One might have to reinforce it on the inside with erector set circular beams and hang a lightweight interior shield to protect the outer shell and hide ductwork and facilities -- or not.

That is, I'm not arguing with you -- I AGREE that there is a lot of work to do on the subject, which is why I think the money being invested by NASA is well-spent. My only point is that there are some good reasons to think that it will be optimally cost beneficial to go this way rather than, as suggested by the top comment I replied to, a foregone conclusion that it is not going to work or turn out to be the best way to go. As many posters have noted, just because NASA opted at least partway out on this scheme with a Saturn V that happened to be available when a moon shot was cancelled doesn't mean that it has been properly researched or provisionally engineered with all of the things we've learned in materials science and electronics in the meantime.

rgb

Comment Re:I don't get it (Score 1) 130

I'd think that evacuating the remaining fuel would be the least difficult problem imaginable to solve. As you say, hard vacuum. It's only tricky if you want to recover it (as both O2 and H2 might have some value of their own in space). Beyond that, pretty much any simple valve will work as long as you bleed it off slowly and watch out for Unintended Consequences (like thrust or vacuum refrigeration of the interior from adiabatic expansion).

As you say, not a new concept. But it is a far cry from try to re-engineer a Saturn V tank "on the fly" to become a space lab and designing a replacement for the Saturn V on the same general scale and with a similar but updated structure DEVOTED to putting up a modular space habitat in stable orbit (say, geosync) or at a lagrange point, or DEVOTED to putting together a similarly modular deep space exploration vehicle to travel to mars or even the moon.

If you are engineering a "Saturn VI" workhorse for these purposes, the entire second stage fuel system would be redesigned to facilitate the reuse of the tanks as part of the payload, and the payload would be, in fact, the rest of the required support system in some sort of snap-together modular approach. The tanks would probably have either completely removable ends or would have ends with large (say 2m out of 3 or 4) ports with a standardized sealable interconnect. I'm guessing (open and closed) interior ductwork would be built in (ultimately ported as needed inside and/or into the standarized interconnect). Some interior facilities might be preinstalled on the ground and capable of handling LOX or LH temperatures at high pressure. Some would await orbital assembly. But all the orbital work would likely be snap together stuff, not "this work requires a team of skilled laborers to install" stuff.

I'd expect assembly to be something like:

    a) Shoot up the rocket, retaining the second stage instead of separating it; No humans needed. In fact, there would be no third stage -- what was the second and third stage of the SV would be all payload for the SVI.
    b) In the desired orbit, bleed any remaining fuel or recover it into a much smaller tank, whichever makes more sense. No humans needed.
    c) Robotically disassemble the outer shell as needed (which might be little or none). Remove all unusable hardware associated with its use as a propulsion system -- the actual rocket motor, fuel pumps, wiring and plumbing. Save what is (designed to be) incorporated into the new function (e.g. exterior wiring might well find new life as interior wiring if it was modular and movable, ditto pipes and perhaps some pumps). Probably save the rest as a "scrap pile" that could be used as a supply of raw metal that can be resmelted with a solar mirror in space, or not, whichever ends up making the most sense.
    d) Robotically disassemble the "payload" on top of the tank, take off the top of the tank, and hook it onto a modular unit (possibly engineered to be a "collar" that fits onto the top of the tank) containing life support, power, an airlock or flexible interconnect designed to connect a series or parallel combination of tanks. STILL no humans needed to render the habitat at least marginally inhabitable
    e) Finally, send up a crew (or deploy the crew that is already there in a growing structure) to do any final interior installations that the robots couldn't handle, fix problems, test everything thoroughly, and integrate the unit into a multiunit modular space station.
    f) Along with any needed crew (rotation), periodically send up life support supplies -- fuel, air water, food -- and any tools and hardware needed. But I'd assume that one could send up and self-assemble many living/workspace modules that are then both inhabited and finished off or (re)furnished by one crew and supply shipment.
    g) Once "enough" of them are assembled and interconnected at the desired orbital point, it would be simple enough to ship up the hardware needed to hook them together into a ring (with anywhere from 10 to 30 modules) and spin the whole thing up to get pseudogravity. Build vertical port(s) into the tank as well as the end ports and add a diffuser and exterior reflector, and you've got your hydroponics section for replenishing air and water (and maybe even food?) or you can hook them together sideways as well as endwise. Or just run LED lighting down the middle run off of the solar collectors and keep them sealed and opaque.

For a Mars mission, you'd ship them up into orbit WITH leftover fuel and one way or another refuel them (turn N-1 tanks into new habitat for the station, use the fuel to refill 1 tank out of the number of required mission fuel tanks, or use a comet). The mission would leave Earth with everybody living in the tiniest cabin imaginable, but once the primary burn was over the emptied fuel tanks would be converted into living habitat for the long, tedious trip. This is ultimately why they are investigating this -- you could imagine, maybe, shooting up empty habitats that weren't also fuel tanks (and sometimes, for some things, you might have to do this as well anyway). But for a Mars mission, you absolutely need the space and cannot afford to have that space be part of the bare payload. You probably leave half of your habitat in Mars orbit ("Mars station") at the other end and play the same trick on the way back -- take off with everybody packed into the smallest possible launch compartment, burn all but enough fuel to brake only that launch compartment back on the Earth end, move into the emptied space, and throw that space away (en route to the sun or deep space) for the final braking down into Earth orbit again on the return.

Obviously one would need repurposible second stage tanks to be robust, proven technology by this point in time, so it is very much worth the investment now to see how to design them and start building smaller scale prototypes.

No comment on whether humans need to go to Mars in person or whether (given robots smart enough to do the needed assembly) we couldn't just use robots to go to Mars in the first place, as we are doing now. Robots don't need "empty" pressurized space to stay sane. But if we are going to go into space IN HUMAN PERSON, we'd better master this particular technology, because humans need at least a few cubic meters of volume per person in order to live someplace for any extended period of time, and shipping EMPTY pressurizable volumes into space is needlessly expensive.

Comment Re:I don't get it (Score 4, Insightful) 130

The article intro above actually explains this, if you read it. The fuel in this tank is BURNED, getting the payload into orbit. In the Apollo mission days, the payload was e.g. a third stage that went to the moon and back, as these are BIG rockets. In the past, the second stage tanks would be "thrown away" and allowed to reenter and burn up, but that's slightly insane given the roughly 32 MJ/kg direct energy cost (multiplied by a few orders of magnitude) of lifting anything at all into orbit.

The reasoning is then as follows: We've gotten this great big cylindrical chunk of pressure-tested metal -- remember, it held liquid hydrogen at HIGH pressure securely through a launch exerting many g's of acceleration -- into orbit. It already cost us millions of dollars to build, and tens of millions to get it into orbit as a SIDE EFFECT of lifting this other, really big payload. Let's not waste it!

So, what can we do with it? Well, given that it is roughly the size and even the shape of a good sized mobile home or the living volume of early submarines, making it into pressurized living space is an obvious choice. It is pressure tested at many times the 0.5-1.0 atm pressure differential needed to sustain human life in space. It is made of high quality, carefully x-rayed, stress-tested metal (because NASA would be insane to fire a rocket into space with humans on board with anything less holding in the fuel of the rocket). The metal has been carefully crafted and annealed to be able to handle liquid hydrogen temperatures without becoming brittle, so it is also proofed against your concerns with heat -- humans cannot tolerate any temperatures this metal is unlikely to be perfectly capable of withstanding, and besides, shielding it from sunlight is a matter of wrapping it in a reflective mylar blanket that weighs almost nothing and can easily be shipped up as part of the conversion kit.

As for radiation shielding -- that I don't know about, but I very much doubt that it is an issue. If the Earth gets hit dead on with a solar flare, I don't think there is anything we could reasonably put humans inside in orbit that would be "safe". It's not clear that being on the Earth's surface inside the atmosphere would be "safe". If the metal that the container was made of wasn't adequate as shielding during such an event -- I'm pretty sure it would be perfectly good most of the time -- and we had something better (but smaller and more expensive) then humans could retreat into the latter as a "shelter" to wait out the storm.

Life support machinery and furniture for the interior of the tank turned into habitat is a small fraction of the weight of the whole thing, and weight into orbit costs like gold.

Now let's compare costs. Suppose you used the Atlas to launch an Earth-built space habitat directly into space as to you suggest, and just wasted the second stage tank as usual. It costs you one launch to get the habitat into space, and the interior volume is almost certainly going to be smaller than the second stage tank volume. Now suppose that you take the empty tank and just hook it onto the habitat you just launched (which already has all of the life support machinery, radiation tolerance etc that you are worried about. Voila! You've more than doubled your available habitat volume in space at (almost) zero additional marginal cost! EVEN if it isn't AS safe as the primary habitat in the event of a solar storm, well, astronauts can always retreat into the primary habitat during such a storm and still use the tank as room for experiments, hydroponics, their ping pong table, room to spread out in to avoid going nuts.

The last question is: What do you have to do to the tank to FACILITATE this so that it isn't being done on an ad hoc basis? As you say, certain pieces of work are way cheaper on Earth than they will be in orbit. Should we build the tank out of slightly different metals so it IS a better radiation shield? Should we pre-install ductwork for ventilation and wiring and liquid management (water and sewage and hydroponics) while it is still down here on Earth? Will any of this compromise its function as a fuel tank (almost certainly not, up to SOME point, but what is that point)? Can we design it so that converting it in orbit is a matter of removing this big plate here, mating a now-exposed sealing ring to a matching ring on a modular component, hooking up "life support" in a daisy chain or fastening it onto the outside and connecting it up, and then just moving in? Remember, this is where human creative design can really shine -- maybe we can ship the furniture and hardware needed to complete a standard conversion INSIDE the tank or INSIDE the otherwise wasted interior volume of the primary payload. That's the whole point of the study. Who knows, maybe they WILL conclude that it isn't cost-efficient or feasible, as this is a feasibility study and if we knew the answer, why bother with the study? But the reason for the investment is clear -- $65 million is chicken feed compared to the potential cost benefit of saving a SINGLE launch of a SINGLE Earth-built habitat into space.

No matter how you slice it, using the tank very likely nearly doubles the USABLE mass you've just lifted into orbit, and if we cleverly re-engineer the tank to be BOTH a tank AND a habitat shell, we can probably reduce the third stage "payload" to be nothing more than the pre-fabricated, modular support hardware. It is almost certain, note well, that this is going to be the MOST cost-efficient way to get ANY pressurizable living volume into space. In a possibly mythical Mars mission, maybe we'll end up using it again first as a -- fuel tank -- refuelled from a comet head we've grabbed and towed in and kept on ice for that purpose. Then as the tanks empty along the way, they become living space for the crew. Maybe they can be daisy chained together to make an actual space habitat in the form or a large rotating ring with "gravity", a design that dates back to early science fiction, after being towed (say) to a Lagrange point using a solar sail (free transport, once you make it into orbit, if you're not in a hurry). The point is that worked metal in space is worth its weight in gold (or in any event costs almost its weight in gold to get it there. Don't waste it.

To quote Robert A. Heinlein (loosely) "Once you are in orbit, you're halfway to anywhere" -- which energetically is precisely true.

rgb

Comment Re:Physical Review Letters (Score 1) 240

Wisdom. I've gotten higher on the math tree than you, perhaps, but I have students who can do math effortlessly that takes me a great deal of effort indeed. And you CANNOT do physics without real math. It's just the way it is. Real math starting with calculus, which Newton invented so that he could invent physics, and continuing on through number theory, set theory, group theory, geometry at many levels, and very, very advanced calculus, calculus so difficult that we can't solve it so discussions are about the best way to approximate a solution.

I get (for reasons that I cannot really explain but no doubt are some sort of karmic burden predestined for all time) lots of people who write me with their own special "unified theory of everything" -- and got them way back when the means of communication were paper letters or phone calls or email on networks like "bitnet" that nobody under 30 has even heard of -- and they are invariably filled with nifty diagrams, platonic ideals, bullshit from one end to the other that is all geometric and compelling to its creator, and have absolutely no relationship to anything one can measure and predict nothing at all. They aren't even accurately descriptive.

No way through but to pay your dues first. And your dues, in physics, nowadays takes years even for super-geniuses who really have a chance at having the critical insight to take things to the next level. There just isn't any low-hanging fruit left. Most of the people who invent theories of everything without doing the work needed to understand the real difficulty of the problem they claim to solve just by being naturally clever, themselves, simply have enormous personality disorders (or worse) such as chronic narcissism, bipolar disorder, schizophrenia, grandiosity. And then there are the spiritualist whackos, who think that crystals produce "energy" without actually understanding what crystals, or energy, actually are. They come up with elaborate theories as well that make physics into a kind of elective magic that one can evade by using runes on specialized charts, according to the stars or deities or demons that REALLY drive everything.

Sigh.

Comment Re:Physical Review Letters (Score 1) 240

Not an argument from me, this is really the point I was making. Gravity waves we observe are the moral equivalent of the classical EM waves emitted by a radio. Sure, somewhere in there there are photons, but they are in a state or mixed state that utterly obscures their quantum nature (and there I actually did a fair bit of work upon a time and have a PR paper on nonlinear quantum optics in the master equation/langevin approach).

So, without trying to unify quantum field theory -- which is what coming up with the right theory of gravitation is all about -- that somehow also is consistent with general relativity, the original question I responded to was whether or not "standing gravitational waves" were responsible for the alteration of ordinary 1/r^2 gravitation OR the excess mass creating ordinary 1/r^2 gravitation. All I then did was point out that it seems unlikely, even without a detailed theory, on the grounds of similar phenomena in the EM field where the "weak" component is more or less irrelevant to the opposition of super-weak gravity -- a point I make every three or four months to a new crop of introductory physics students btw. It takes an entire planet to pull us down with our weight. It takes the combination of electrostatic force and the Pauli exclusion principle to oppose that weight with a thin skin of structured charged particles (where nuclear and electroweak are important on the inside of atoms, but the actual force managing the repulsion is all fermionic electrons).

That doesn't make it impossible. The EM force is modified at short range by (quantum) virtual pair production and the polarization of the vacuum. One can imagine, at least that the vacuum is polarizable in some way to gravitation, although it is a bit difficult given that we are only aware of a single "pole". At least some phenomena in EM also alter measurably when one makes bound states out of things, creating bands of states instead of "ideal" sharp lines -- I'm not sure how that would apply to gravitation as gravitational bound states are the moral equivalent of purely classical EM orbits but without the strong radiation of energy that was predicted by Maxwell and that was part of the downfall of Newtonian mechanics. Sure, the moon presumably radiates away gravitational energy every time it orbits the earth, but the effect is so miniscule that it is overwhelmed by tidal coupling that drives the moon AWAY from the earth every year by a few cm, the exact opposite of a radiation spiral.

So I simply repeat -- if somebody wants to explain the cosmological galactic orbital anomaly data that gives rise to the dark matter hypothesis using "gravitational standing waves" instead, they have their work cut out for them. Starting with reading at least some of the hundreds of papers out there (usually a focused search and skimming of the abstracts can eliminate 90% or more of them, of course) and in many cases starting even earlier by getting University degrees in some mix of (serious) math and physics. I am a theoretical physicist, I'm pretty good at math and can do pages of algebra towards a goal and so on, and I'm still a bit intimidated by the gravity people. Differential geometry just for starters, maybe topology, general relativity, and of course the full course in math and physics through quantum field theory are your OPENERS, and then things really get difficult. Makes me tired just thinking about it;-)

rgb

Comment But what about Donald Trump... (Score 1) 132

After all, hinting that gun owners might take matters into their own hands IF Hillary is elected (the time ordering and meaning of his sentences was very clear) sounds like promoting anarchy, treason, and terrorism to me.

Also, if he asserts that Obama is the "founder of ISIS" then he has to acknowledge that he wanted to "found ISIS" in exactly the same way as he clearly an unequivocally stated in TWO CNN interviews. So let's call him -- by his own standards -- a "co-founder of ISIS".

One can then work one's way down through whether or not calling for a "wall" to be built between the US and Mexico, prohibiting immigration of all Muslims, etc counts as "promoting terrorism" in the same sense that drawing Mohammed having relations with a camel or insulting whole swaths of the US population by calling them rapists and thieves might promote, rather than extinguish, acts of terror-level violence.

No? Political speech and hence protected? Then precisely what IS the difference between this sort of twittering and public speaking and expressing extreme annoyance at the United States in general and Trump in particular?

Comment Re:this is a good thing, but not enough... (Score 1) 64

I disagree. There is a whole world of "public", and a lot of them don't have access to a University library. And no, science should not be confined to the cloistered halls of academe. You simply don't know who might come up with a new discovery or objection to a published work, or who might be inspired by one to invent something new. In addition to US citizens that paid for the research, there are young people in India, China, Africa who will only have the opportunity to read real scientific papers if they are open access. Do we WANT to keep the rest of the world in a state of non-participatory ignorance? Is that the kind of world we want to live in?

I would say no. And I agree, journals have a useful purpose, or even many useful purposes. But still, paywalled journals are, IMO, doomed. I think they'll be lucky if they get a year of grace from the granting agencies on the one hand, and nearly everybody puts their own work up on the web anyway -- it's just hard to find it and difficult to see if it actually made it through the refereeing process in the form posted without being able to access the actual published article.

The internet is not through evolving. We'll see where this ends up. If we live long enough...;-)

Comment Re:this is a good thing, but not enough... (Score 1) 64

This is not true. In fact, it is not true by law, and was not true by law then. You simply haven't tried. The DATA is readily available from NASA funded research (and often the papers are/were too). The real problem, as I said, is that the old way the journals ran from the invention of the proceedings of the royal society to the present has been dead for at least five years, but nobody knows how to keep the journals (a desirable thing, believe me) and their refereeing and editorial process alive without the money Universities kick back for subscriptions. If everything is free on the web, there are no subscription fees and the journals die. If the journals die, it is as disastrous a consequence as trying to run the US with only a president and congress and no supreme court.

Yes, there are alternatives to paid journals, including some online/free ones, but they ultimately rely on humans contributing time (or to put it another way, having their living paid for some other way). That's not bad, but you can see why there could be problems with this approach as well. It remains to be seen what will work and not introduce even more sources of bias than there are in the current system (which is not above reproach -- gatekeeping and worse abound in at least some journals).

BTW, I'm not a fan of a lot of what passes for climate science or NASA GISS, but you do NASA in general a disservice if you think that GISS was somehow exempted from the law. Or if you think that everybody in NASA GISS are members of a vast conspiracy and not intellectually honest. James Hansen, for example is not everybody, even if he should have been replaced before he even started as head of GISS, or at worst the first time he spoke ex cathedra predicting 5 meter SLR. In my opinion.

rgb

Comment this is a good thing, but not enough... (Score 4, Interesting) 64

I actually had the privilege of advising the govt to do this a few years ago, so it is nice that it is happening. But even then, NASA was progressive and required open access to data and more from their supported publications. This is a notch up.

The problem is that it needs to be mandated across all journals, and the journals then will face a major problem -- how will they survive when one no longer needs to buy journal subscriptions to fund the journals? Government support isn't a good answer for lots of reasons. But what answer IS a good answer?

I don't know, but they'd better find it soon, because the Internet has made old-style journals largely obsolete and the public will no longer tolerate not being able to read the research they, after all, ultimately paid for. It is my profound hope that the NSF and other major agencies follow suit immediately. We'll see if e.g. Physical Review can survive it and deal with what comes either way.

Comment Re: Physical Review Letters (Score 1) 240

Again, I have to say this feels like a complete non-sequitor. I'm not sure exactly what you are trying to suggest with your assertion of "ample discussion and explanation of time theology" and how the "same arguments... were answered so long ago". When I google "time theology" (which I wasn't even aware was a reasonable "subject" of hermeneutics, if one imagines that making stuff up so that it all works out is somehow either a subject or reasonable) I get several hits but they do not illuminate your statement. I can't even tell if you are arguing that the Bible is "true" (for some meaning of the word true that is not, in fact, the meaning of the word true) or if you are commiserating the fact that people continue to defend the Bible as being true in spite of the fact that an eight year old child could tell that it was all made up if they weren't brainwashed to think otherwise from when they really were too young to know any better.

But then to jump to physics -- which has a completely different standard for establishing probable truth, one you can actually learn about if you read e.g. E.T. Jaynes' "Probability Theory, the Logic of Science" or "The Algebra of Probable Inference" by Richard Cox (or you are welcome to take a pass at http://www.phy.duke.edu/~rgb/a... if you don't mind an eternally not quite finished book that makes the same argument, possibly more broadly) -- physics as a subject actually doesn't have that many "arguers" about things that are well explained by consistent theories plus evidence. Not within the discipline. This is in part because there is something approximating an objective standard for determining when something is (probably) true, (probably) false, or (most definitely) not really resolved yet one way or another. People may well have all sorts of fun in the middle area, but it isn't because of any misuse of faith, it is more a matter of placing your bets as to how experiments will eventually work out to resolve the issue, with both sides knowing that it is a BET and not to be taken seriously (that is, as truth) without experimental evidence to back it.

On /., of course, LOTS of people argue about physics, but most of them aren't physicists, and the ones that are are trying to correct people's egregiously lacking understanding of the physics of what they are arguing about. Which is the point I was making above, BTW. If you take a theory where the idea of standing waves is fairly well understood both mathematically and physically, and try to imagine how to make it explain the galactic rotation data, it is at the very least not easy to see how to proceed. This is a concrete statement, and if you disagree, feel free to actually post your way of proceeding. It wasn't argument, as I'm neither asserting that there is or isn't a fifth force, dark matter, monopoles, a useful standing wave theory of gravitational waves, or for that matter a meaningful "time theology" whatever that might be -- I'm just pointing out that using the terms in their usual sense it isn't easy to see how to explain the galactic data using standing gravitational waves, or even to see how (necessarily monochromatic and coherent) standing gravitational waves could come about.

The place where physicists DO argue is at conferences and workshops, usually where they disagree about some aspect or another of mathematics or experiment in an area of physics that is not yet resolved into probable/accepted provisional truth. I've been in the middle of one of those and it wasn't pretty. How CAN one explain things like conditional convergence of series to somebody that already ought to know it? But in the end, the mathematics and sound reason usually win, because (unlike time theology) there is actually a unique answer and we have an objective method for homing in on it.

rgb

Comment Re:Physical Review Letters (Score 2) 240

Oh, dear, I you misunderstand the nature of evidence and theory, sir or madam. One does not usually "refute" a hypothesis in physics, and absence of evidence is not sufficient evidence of absence. The best that can be said for or against fifth force theories in physics is that there is little sound evidence to support any specific one of them. At the same time, there is AMPLE evidence that our knowledge of physics is incomplete, and there are large scale, clearly visible phenomena (like the galactic rotational anomaly and other cosmological observations) that strongly suggest that there is indeed SOME sort of additional force or interaction present beyond the four we know of, as we cannot (so far) see any way to explain what we see within the confines of those theories.

Is it a "fifth force"? Is it "dark matter" and/or "dark energy"? Well, if it is the latter, it IS a fifth force, at least, unless somebody manages to come up with a particle outside of the existing elementary particle zoo that doesn't couple to any of the forces but e.g. gravity itself. However, physical particles usually couple to the physical forces in some way so a completely new particle is not unlikely to be associated with a completely new force.

The point is that I don't BELIEVE in such a thing -- few physicists do -- in the absence of evidence to support such a belief. I think the theory of magnetic monopoles is absolutely lovely -- they would fill a tremendous gap in our knowledge of physics, they would symmetrize Maxwell's Equations in a way they are begging to be symmetrized in, they would explain the quantization of charge -- but I, like most physicists, will only BELIEVE in monopoles when somebody reproducibly puts salt on the metaphorical tail of not one, but a steady stream of monopole observations. Ditto the Higgs particle. Ditto "trans-luminal neutrinos". Experimental evidence talks, theoretical bullshit walks -- or more reasonably, waits in the wings as a plausible hypotheses not yet supported until experiments are performed that increase the probability that they are correct (incorrectly stated as "confirm" them, just as a lack of evidence or negative evidence doesn't necessarily "refute" them).

I don't quite get your point about the Bible, either. Yes, the Bible is bullshit, with pretty much ever line of its supernaturalism refuted by ordinary common sense and all of the evidence worthy of the name we've ever collected. (To provide an interesting metaphor -- suppose all four gospels reported Jesus as saying "I have seen the magnetic monopole in my water turned into wine." Would any reasonable person then conclude that monopoles are proven to exist beyond any reasonable doubt based on a single, 2000 year old observation of them reported as hearsay by individuals who were not there and who reported nothing of the experimental method used, the error bars, the controls against fraud perpetrated just so one could get tenure... bearing in mind that turning H_2O lacking carbon and nitrogen into a complex of ETOH and lots of flavorings and particulate matter made up of proteins and hydrocarbons is even more ludicrous than observing a monopole without any visible apparatus or method) Quite a lot of its supposed history is unsupported by actual archeological evidence -- it is more in the category of "legend" shading over into "myth" than it is "history". But belief in the absurd in the context of the Bible is in no way comparable to the process of formulating hypotheses and searching for corroboratory evidence in cutting edge physics. Even theorists who propose the theories usually know better than to "believe" in them -- they do the work in the hope that experiments will be done (guided by their work, perhaps) that validate their hypotheses or correct them and give them new insight.

Our knowledge of the Universe is known to be incomplete. It is then just a matter of common sense that we should work to complete it, and that work involves proposing new ways it might be completed, and then seeing if they pan out. Some of the proposals might require a complete rewrite of ALL of our existing, evidence supported beliefs -- it's happened before, it could happen again. That's just the way the game is played. Faith -- as opposed to plausible, consistent, evidence supported belief -- has nothing to do with it.

rgb

Comment Re:Physical Review Letters (Score 2) 240

Maybe. But I think you'd have your work cut out for you to show it. And you'd have to explain at some point why e.g. the Coulomb interaction doesn't demonstrate it as a direct augmentation of Coulomb interactions and meso-scale deviation from 1/r^2 form with its much greater (and hence easier to observe) interaction strength.

Standing waves in EM fields (where we can easily observe them in e.g. lasers, Fabry-Perot interferometers, etc) require reflectors at both sides of a cavity. They arise out of solutions to a wave equation with specified boundary conditions on surface(s) bounding a volume. We do not USUALLY observe them as steady state phenomena between individual pairs of particles or objects, in part because the objects would scatter an incoming wave, not reflect it back in the direction that would (eventually, after a retarded time) be the location of the source. The scattering results in incoherence. It is very difficult to see how a linear wave theory could give rise to an effectively nonlinear resonant alteration of gravity with large numbers of incoherent sources in any of the usual models of dispersion or resonant interaction, let alone one that has the right properties to explain the observations.

So, if you are a math/physics/field theory uber-geek (I'm not, I'm just a humble ordinary physicist and this is over my pay grade:-) you could always give it a try and try to build some sort of model of your hypothesis, after doing enough research that you can establish how to even start, but as I said, my intuition based on a fairly detailed knowledge of ordinary EM waves is that -- probably not worth the time. One MIGHT argue that a dense galactic center (or a black hole at the center) could form a kind of effective "boundary" for such a wave, but the increasingly dispersed stars and other matter surrounding the galaxy do not seem to be good candidates for a second boundary.

If you want an idea that seems MORE likely to be fruitful, imagine that the black hole is radiating quantized gravity waves in all directions, and that those outgoing waves, as they pass physical matter, stimulate the coherent emission of more gravity waves in the one-pass phenomenon (observed and actually exploited in E&M) known as "coherence brightening". We actually observe coherence brightening in astrophysics, IIRC, when light from a distant source passes through excited stardust (that is, for example, ionized by nearby stars.

But this still doesn't quite work for me -- for one thing what "excites" stars so that they can add energy to a gravitational wave (which has to carry energy, after all)? Why doesn't the surrounding matter act more like a dielectric and SCREEN the gravitational field, if anything? It's hard to know how to even begin to build a theory of gravity per se that could explain the galactic rotational anomaly, and I think many very competent people have tried and continue to try.

rgb

Comment One of many reasons to stop worrying... (Score 1) 254

...and wait for technology to catch up. At some point cost efficient storage has the capability, as TFA notes, to dramatically alter the utility and (especially) the cost-efficiency of intermittent renewable sources. The other critical point is energy transportation -- moving e.g. PV solar energy from Arizona or Texas to Maine without dropping half of it along the way. In the meantime, can we stop panicking and wasting huge amounts of money IMPLEMENTING immature technologies while they are -- immature?

rgb

Slashdot Top Deals

The test of intelligent tinkering is to save all the parts. -- Aldo Leopold

Working...