But we're talking about a space station in earth orbit - which means that we're dealing with mostly high-energy protons and electrons (unless it's a *really* far out orbit).
Van Ellen particles are relatively low energy compared to what's coming in as cosmic rays, but I'd have to look up detailed numbers to comment much further on shielding.
The main thing that was bothering me about your previous post was that you were implying (perhaps unintentionally) that it's primarily the hydrogen that does the shielding, which is emphatically not the case (high-Z materials have more electrons to interact with and a larger nuclear scattering cross-section for most things, though I understand your point that it's not _desirable_ to scatter off of high-Z nuclei). If I've misunderstood your intention, my bad.
Googling duraluminum didn't help in discussing its suceptability to fatigue compared with regular aluminum, or say, steel.
Googling for "fatigue strength" and "aluminum" brough up a nice list of aluminum alloys. 2024 and 5052 have especially good fatigue properties compared to other aluminum alloys (though I'd need more googling to compare vs. steel). 2024 has copper as the primary additive, which meshes with what I recall of duraluminum (though I'm not sure if that's the actual alloy used; just that duraluminum is likely a 2000-series alloy).
Even in space, there are some serious risks, aggrivated by the fact that temperatures are so low and since you have such dramatic thermal cycling.
For a craft far from Earth, you typically make the shell thermally conducting enough that you don't get a large heat gradient across the craft for precisely these reasons. Spinning the craft also helps. LEO craft have problems because they usually pass through Earth's shadow on a regular basis. A Mars craft wouldn't suffer these difficulties (could keep an orbit perpendicular to the planet/sun axis when stationkeeping).
Admittedly, the proposed hotel is in LEO.
On a different topic - finally figured out why your name was ringing a bell. We'd had a discussion about asteroid mining in 2001, that was eventually moved to email. My address has since changed (twice, actually). It is good to see that you are still interested in space. My own space interests have tended towards medium-term future prospects instead of present ones (ran numbers for fusion craft a while back; conclusion: very hard to build useful magnetic confinement ones).
There's another real advantage to this method that hasn't been mentioned yet: radiation shielding. If you build your station out of plastic instead of aluminum, you'll get far better radiation shielding (it's the hydrogen atoms that do the best job!).
Depends on the type of radiation being shielded against. High-Z is better for gamma shielding (and shielding against secondary x-rays from other types of radiation, though using low-Z reduces the amount of this). You also have a bulk disadvantage with low-Z materials (though in space, it's weight and not bulk that matters, so you're stuck no matter what).
Furthermore, aluminum is a kind of nasty metal to use in extreme circumstances because as it warps, it stiffens and eventually will break (metal fatigue).
Aluminum itself has very low fatigue strength, but in practice aluminum alloys with better characteristics are used. Google for "duraluminum", an alloy commonly used for aircraft, for one example.
For space uses, the cost of launch dominates over the cost of materials, so you can afford to use as expensive an alloy or composite as you like in the structure. Materials problems typically occur due to design oversight (e.g. carbon composites being etched away by the atmosphere), as opposed to cheap materials being used.
Inflatable stations are still an interesting idea, though. If I recall correctly, the "Cosmos" solar sail was going to be inflatable, to save on mass (a rigid craft would have to be sturdy enough to survive launch, requiring extra mass).
However the i960CA and its followon the i960CF were pretty slick. The i960 had 32 general purpose registers, and a processor-defined function call sequence that always placed a set of 16 on the stack ("caller-owned") and left a set of 16 alone ("args , temp & return values"). The i960CA cached the top 4, 6 or 8 stack frames in on-chip static memory with a 128-bit pathway to the main register set. This gave it amazing function calling and interrupt service performance.
The UltraSparc did this as well (slightly different register layout, but same idea). I'm not sure when this was introduced (UltraSparc or earlier); anyone out there have a timeframe for Sun's implementation vs. Intel's?
The improvements that the 80486 brought was essentially a built-in FPU unit and faster clock speeds.
If I understand correctly, it was also the first x86 chip that had pipelining. This is why the "clock cycles" entries in that handy "xt-through-486" assembly reference booklet went from "5" to "1" for a whole bunch of instructions (instructions still took several cycles, but that latency was masked as long as dependencies didn't cause a stall).
Pipelining has been around for far longer than that, but it was a very significant x86 milestone.
You're promising not to reply to my posts, now please STOP DOING IT.
Fine. _I'll_ reply.
Gravastars are an interesting idea, but they:
a) Propose modifications to physics (the phase transition that gives rise to a different type of space in the interior).
and
b) Attempt to solve a problem that doesn't necessarily exist (embodiment of entropy in black holes, which string theory takes a fairly good stab at explaining).
Thus, I'm skeptical of claims that gravastars exist, barring observations supporting their existance or wider acceptance by the scientific community.
At least in the paper I've managed to dig up so far, they acknowledge many othe potential models of how black holes work, and suggest types of observations that would help determine whether their model is accurate (i.e., they don't claim it's the One True Model off the bat). This is one of the hallmarks of good science.
Observations to look for are gravity-wave signatures of resonance modes in the stiff shell surrounding the gravastar, and optical signatures of impacting matter interacting with this shell. The first should be possible when we get sufficiently sensitive gravity wave detectors online, and the second should be possible from observations of accretion disks in known black hole/other star binary pairs once Mazur and Mottola have worked through the math to figure out what the observational signatures should _be_. Thirdly, if you could get close enough to take good measurements, you'd be able to distinguish between gravastar-type black holes and Hawking-Bekenstein black holes by different radiation signatures coming off of them, but that requires being right next to the hole and having instruments sensitive enough to detect very faint, low-frequency thermal radiation.
In summary, claiming that the gravastar model _is_ what black holes are is very, very premature.
The primary limitation on even arbitrarily sophisticated nanotechnology which could prevent a runaway grey goo reaction is the lack of a sufficient source of energy. A nanomachine wouldn't be able to get much energy out of eating inorganic matter such as rocks because, aside from a few exceptions (coal, for example) it's mostly well-oxidized and sitting in a free-energy minimum.
It would instead get its energy from sunlight and distribute it electrically within itself. Catalyzed electrochemical reactions would break down silica-based minerals to provide more building materials.
This wouldn't allow transformation of the earth in the blink of an eye, but you'd still get rapid progress (picture nano-lichen that spreads across rock in a layer that grows thicker as underlying rock is digested). Heat of formation of SiO2 is about 14 MJ/kg, and it weighs about 2.6 T/m^3, for a decomposition energy of about 37 GJ/m^3. A perfectly efficient nanoswarm would eat into a rock face at a rate of about 0.1 m/year (given a solar duty cycle on the order of 10%). A realistic upper bound to system efficiency is on the order of 10%, giving about 1 cm/year.
So, areas could be actively protected against nano-infestation without much trouble (even with something as simple as a layer of paint), but unattended rock mass could be converted to nano-powder quickly enough to cause serious environmental problems in some situations (mountain rockfaces above the tree line sift nano-sand down on top of vegetation below, choking out plant life and lowering the tree line; lather, rinse, repeat, until what was a mountain range and foothill network becomes a desert).
This all assumes silicon-based nanomachines. Carbon-based nanomachines are more attractive from a construction point of view.
I consider disaster scenarios like this unlikely (among other things, the "desert" produced in the scenario above would quickly be seeded with vegetation, which would choke off its power supply). But, they're fun to think about.
One storage method that will work in many places is water, on a hill. About 10 cubic meters of water 1000 ft up stores about 1 MWh of energy.
It turns out that whoever provided you that figure made a rather grave math error.
1000 feet is about 300 metres. Gravitational potential energy near Earth's surface is 10 J/kg*m, so you get 3kJ/kg. Using 10 cubic metres gives you about 10T of water, or 10,000 kg. This gives you 30 MJ of stored energy - about 8.3 kW*h.
It looks like your source confused feet and metres, and then wrote MW*h when they meant MJ.
Practical gravitational power storage would require a huge resovoir (think "hydroelectric plant that you can run forwards or in reverse"). The basin size needed for, say, a day's worth of power storage for Ontario would be roughly the size of one of the Great Lakes. It is questionable that the construction of such a resovoir could ever be practical.
Add this to the logical fallacies. How do you think the grocery store refrigerates your food before you buy it? Now, how much would refrigerated goods cost to you (the average Joe) if refrigeration costs doubled?
You might even notice other goods and services increase in cost. It's silly to think that the cost of electricity is only reflected in your electricity bill.
You can get accurate values by looking at population and total power generation capacity in an area, getting the total per capita power consumption, and then multiplying that by the change in cost.
Up here (Ontario, Canada), we use an average of about 5 kW/person, for all forms of electricity consumption (personal, industrial, etc). That's about 44,000 kWh/year, or $2,200 Cdn/year in real energy cost (at $0.05/kWh; it's actually slightly less than this).
The cost of electricity could double, and while it would be annoying as heck, it wouldn't be catastrophic. Multiply by a factor of 10, and you're in catastrophe territory.
don't be foolish. Any idiot will just tell you to run everything on Hydrogen, which you can make from the electricity. So in a way, everything could be nuclear powered.
Hydrogen turns out to be a bad choice, due to storage problems (tends to diffuse out through most materials, and even at very high pressure can't be stored at a density that gives energy-per-volume comparable to fossil fuels).
A better choice is to use methane or methanol, either of which can be synthesized directly (burning hydrogen and CO2 for methane, partially burning methane and oxygen for methanol). They can both be stored at liquid densities (though methane has to be cryogenically cooled for that), can both still be used in fuel cells (reforming cells), and can both be used in conventional engines (gas turbines for methane, and either turbines or modified internal combustion engines for methanol).
I doubt that military vehicles, let alone aircraft, would use hydrogen as fuel, due to the large high-pressure storage tanks required. Methane might be practical, though picky. Methanol would be practical without problems.
Also, nuclear plants don't take up the *enormous* amount of space that wind or solar generation would require (a factor conveniently ignored by anti-nuclear activists).
Actually, solar isn't that bad. Energy density at this distance from the sun is high enough that the solar plant area required to power a given population is much less than the farmland area required to feed them, even with relatively low generation efficiencies.
The real problems are cost (even concentrating mirrors aren't free), and power storage and transport (you need to either hold a week's worth of power in reserve in case of bad weather, or hold a night's worth but always be able to draw power from somewhere with good weather). Concentrator-based heat plants area already cheap enough that they're being built as pilot projects. Thin-film photovoltaics continue to approach economic usefulness (and will probably surpass heat-engine based systems, due to conversion losses going from heat to electrical energy). Fuel cell technology is already mature enough that we could build power storage plants, but it requires enough of an outlay that we won't until we have to (or until voters force a tax break for reformer-based fuel cell plants that can generate power from fossil fuels before being switched over for power storage).
In summary, I think that solar power is the most practical of the renewable power source options, and will eventually be adopted as the price of fossil fuels creeps up (it's unlikely to run out overnight - we'll just move to less accessible/costlier sources until alternatives gain marketshare). Fission power, in North America at least, has political problems that will likely make it unattractive.
I mean things like shooting the payload from a cannon or something..
The main problem is that any reasonable gun size requires thousands of Gs acceleration. That eliminates most cargo options (so you still have to use another launcher type for much of your cargo).
You're also limited by the atmosphere. While you *could* try to build a 1000-km long human-rated mass driver, you'd be plowing through the atmosphere at Mach Silly for most of the acceleration distance, and for hundreds of kilometres after launch (you're launching at a very shallow angle).
Techniques that try to deliver energy remotely while using atmosphere or carried mass as reaction mass run into the same problems as scramjets (for the first case) and conventional rockets (for the second case), in addition to requiring a large number of expensive installations for laser launchers or what-have-you.
Techniques that involve climbing up or being scooped up by an orbiting object require better materials than we can currently manufacture in useful quantities. In 30-50 years, this may change, but it's not a sure thing yet.
In summary, while there has been and still is a lot of research about fuel-free launch schemes, none of them are practical at this time.
As long as we need 100*X pounds of fuel to launch X pounds into space, space travel will remain uneconomical for most purposes.
Not true. Your cargo to craft (mostly fuel) mass ratio is 1:100 at worst. For a fuel as cheap as gasoline (and liquid oxygen is about this cheap in bulk), you get around $100/kg. Not cheap as dirt, but hardly cost-prohibitive. It's the vehicle itself and the facilities that drive the cost.
The problem is that right now the vehicles and the support facilities cost a _lot_ to build and maintain and staff and insure. This is where most of the money goes. Better materials and mature designs will reduce vehicle costs, which will help increase volume, which will further reduce costs from mass production and facility management scaling for at least a little while, but the cycle proceeds slowly. Give it time.
The last big experiment (reusable vehicles to save on vehicle costs) failed, due to increased complexity (for all designs), difficulty and expense of between-flight overhauls (for the shuttle), and difficulty meeting craft requirements with existing materials (all reusable craft, but especially SSTO craft). Now the focus seems to have shifted on reducing costs for disposable vehicles. We'll see in a couple of decades how this turns out.
Your point stands? It doesn't have a leg to stand on.
Let me spell this out for you.
A data transfer bottleneck makes interferometry suck just as much as it makes light-gathering suck, because in both cases you're throwing away most of your data.
An effective increase in signal-gathering capability by the factor of 30 you quote gives an increase in ability to distinguish signal from noise of about 5.5 (signal goes up as N, noise goes up as root N). This is piddling compared to the fact that, being no longer data-limited, you can take all of the interferometry measurements you like instead of having to play duty-cycle and array subset games to get around the network limitations.
The article focused on photon-collecting capability. Good for it. Doesn't change the validity of my statements.
If you RTFAs you should have noticed numerous references to the increased sensitivity of the new system in addition to the increased resolution.
Unless they are linking thousands of telescopes, they are getting one *hell* of a lot larger boost in resolution than they are in light-gathering power by linking telescopes. S:N improves as the square root of light-gathering power, further reducing the resulting improvement in sensitivity.
Development of technology is amazing. I read somewhere a long time ago about and engineer (I think) who said his mother (I think) was afraid that we will lose control over the computers in a near future. His reponse was that this was very unlikely to happen, but he did believe that we already have lost control over development and technology advancements.
Once we can reliably produce computers that are smarter than we are, it's only a matter of time before they dominate society's workings. This isn't necessarily a bad thing, but there's no guarantee we'll particularly like the resulting state of affairs either. It could also just as easily end up being us who are the computers (using AI technology to enhance our own thinking as readily as we build self-contained thinking machines). Whether we'd still count as "human" under these conditions is a matter of philosophy, not science.
Very murky waters, and very difficult to predict which of the myriad of possibilities will actually happen.
Re. technology development, we're definitely at a point where if something would be useful or even just interesting to do, someone will do it (look at human cloning). The resources required for research are readily available, and there is no practical way to establish ironclad control over all research in the world at this time. Couple this with national competitiveness, and you get relatively unhindered development. This may eventually change through any of several methods (we reach a brick wall where all research is expensive [unlikely], we finish researching everything that has a practical/commercial application [unlikely any time soon], we unify under a global government that can and does restrict research [unlikely any time soon]). Combine this with some technologies that drastically lower the bar to research and development (like nanotech, if it can work as well as hoped), and you get this state of affairs continuing or even getting more extreme.
It will be interesting to see how it all works out.
Along those lines - how long until we have a telescope that can see far out/back enough that we can "see" the events even closer to da big boom?
There is a hard limit to how far back we can see - the point at which light and matter decoupled (when the whole universe was a plasma, it was opaque; when atoms formed, it became transparent). We can already see to this boundary in some bands. The cosmic microwave background, for instance, is the severely redshifted thermal radiation from this decoupling. Optically, if I remember correctly deep-field pictures went back a bit over 10 billion years, and the decoupling happened around 13 billion (or about 300k years after the big bang). So we're relatively close, but observation gets a lot more difficult at high redshifts (less energy reaches us, and there may not be bright, compact galaxies to see - though this itself would be a useful measurement to make).
An astrophysicist/cosmologist can give you more detailed answers on this than I can.
...(or how far out) will they be able to spy with this puppy?
The ability to see great distances requires a large number of photons to be collected (to pick up faint signals and better separate signal from noise), which requires a large aperture area. They're not getting that here, so they won't be able to see much farther.
What they _do_ get by using radio telescopes in tandem is a much larger effective aperture _diameter_, which lets them resolve finer details. What was once a blob or a point source of radio waves, now resolves into jets from an active galaxy, or what-have-you.
This doesn't require a fiber link (they're using microwave links to exchange data between the Merlin telescopes now), but a fiber link lets them transfer more data and so do the data processing a bit more efficiently. Same telescope array, better throughput (so more of the captured data can actually be analyzed).
I find it very interesting that we've come so far in the understanding of space, but we still have but scratched the surface. I would love to be able to hibernate for say 100 years, and then find out where we're at in technology, space flight and exploration.
For telescopes, you won't have to wait more than 50 years, tops. Optical intereferometric telescopes have been built that do much the same kind of thing that these radio telescopes do (huge effective aperture diameter from many smaller telescopes, letting you see relatively bright objects in fantastic resolution). Space-based ones are in the planning stages now, and will be launched well within your lifetime. This will allow us to do detailed surveys of nearby solar systems.
A sun-orbiting array of radio telescopes would also be useful, for similar goals (and to make really accurate maps of our own galaxy's interior, and give a better idea of the structure of nearby galaxies). No idea if anything like this is on the drawing board just yet. If anything, it'd be much easier than an optical array.
Technology-wise, we're likely to have mature materials and fabrication technology 100-150 years from now, either through nanotech or through more conventional synthesis techniques. That will let us build just about anything we want to that's within the theoretical limits of materials built from ordinary matter. We'll also likely have true AI. Whether the world looks like an updated version of our current one, or whether we go through a Vinge-style singularity into a very different type of world, is something our grandchildren will find out (I'd like to live that long, but I'm not going to bet on it just yet).
I think hydrogen may have potential in that application. It's a reasonably efficient way to move energy around. You have to use some kind of energy to produce the hydrogen, and it would be far better to do it with solar than with fossil fuels.
Solar cells are actually very good for this purpose, as electricity is produced directly, as opposed to having to be converted from another energy form (like heat, in the case of a coal or oil fired power plant).
You can produce hydrogen from fossil fuels fairly efficiently by "reforming", though. What this essentially does is strip hydrogen off of hydrogen-rich hydrocarbons, giving you carbon-rich hydrocarbons and hydrogen gas. The hydrocarbons can still be burned in a suitably tuned power plant, and the hydrogen gas can be used in fuel cells.
If you're using a fuel cell for storage, as opposed to generation, though, you'd just keep the water produced when you feed hydrogen and oxygen in it, and break that down to get your source gases back out (though you'd probably dump the oxygen instead of storing it, since you can pull more out of the atmosphere easily).
The real problem with hydrogen as a storage medium is difficulty storing it at any reasonable density (cheaply - we can't afford palladium storage cells, and they're horribly heavy anyways).
Or it might be a way to bridge the energy gap in ethanol (either for combustion or in fuel cells), where currently you have to burn an amount of fossil fuels to produce the ethanol, some say more than you get out.
You'll always use more feedstock than you get ethanol out, so I assume you're talking about power spent converting the feedstock to ethanol.
I actually think that alcohol makes a better storage medium than hydrogen, because it's easy to store, can be burned in internal combustion engines, and can be reformed (see above) and used fairly efficiently as a fuel for fuel cells. The only catch is that it's annoying to synthesize. Methane can be synthesized relatively efficiently, and you can partially burn it to produce methanol, but that's still not very efficient.
Probably efficient enough for many applications, though (you don't care much if your notebook takes twice as much power to charge as you get stored in the battery, even if you do care for things like your car, and even more so for a city's "week of bad weather" power reserve).
At the moment I'm more worried about being in thrall to a rather unstable part of the world for oil than I am about the atmosphere's CO2 load, but it is also pretty scary.
I'm somewhat puzzled by this situation, as it appears to be one of choice as opposed to necessity. Here in Canada, we could get all the oil we'd need for quite some time from Alberta, and there are enough offshore natural gas reserves to satisfy that demand as well. Last I heard, the gas reserves off the US's coasts were *huge*. We'd see a price increase switching to local supplies (maybe even a hefty one), but nothing that would bring western society crashing down.
After those ran out, a century or two down the road, Canada has enough uranium to last us indefinitely, and the political will to use it for power. The US would need a creative political gimmick to be able to use it now, but a century is more than enough time for public opinion to change. Even without a breakthrough in power production, I don't see any serious problems.
All those green freaks don't realize we generate 10x the pollution making solar cells as we do generating the same amount of electricity for grid-use.
This turns out to no longer be true. Look up thin-film cells, which are both cheap and low materials use.
Re:Will this work with other materials?
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Solar Cells Get Boost
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· Score: 3, Informative
I simply don't know enough about the physics, but... can this be applied with the other developments like multi-band gap improvements?
I'm on shaky ground here, but I think the answer is likely "no". The idea behind this technique is that you can use surplus energy from a photon absorption event to release a second electron, while the point of split bandgap cells is that you can absorb light with less surplus energy (more deposited in a useful manner into the first electron).
Ask a semiconductor physicist to get the correct answer:).
So if you really want to know what's going on you need to discover how efferent lead selenium solar cell's are and what it takes to mass produce lead selenium nanocrystals in a cheep long lasting solar cell.
Nanocrystal films would typically be grown by chemical vapour deposition (chemical constituents react as a gas at low pressure, seed crystals grow in-flight, and grow further after being deposited).
The problem is that it's very hard to produce crystals that small (they tend to keep growing after being deposited, because the source materials are still present - this is how you normally do CVD, actually). You also have difficulty producing a narrow range of sizes, because that requires that the growing environment of each crystal be identical.
Still an interesting discovery, though. The fabrication problems will eventually be solved.
What's especially interesting is looking at what happens when you fabricate oher types of semiconductor microstructure or nanostructure by more conventional techniques. As the size of a feature shrinks, you can no longer pretend it's near-infinite in extent when figuring out what the energy levels are within the crystal. This has already been used to alter the properties of silicon (fabricating LEDs in silicon, which normally emits very poorly due to having an indirect bandgap). Quantum wells, wires, and dots are an extreme case of this (dimensions comparable to a few electron wavelengths). When lithographic feature sizes start approaching this range, lots of new devices will be possible in mass-market chips that are only possible now if you have an e-beam lithography setup handy.
W/ regards to our models of interactions and and extrapolations from the big bang to the present day and nuclear synthesis models, the impression I get whenever I see them is that they are vaguely phenomonalogical. They don't seem to me to be the equivalent of say.. maxwells equations but closer to say mathematical biology / population biology models (perhaps this isn't fair). Is it possible that these models may be wrong in some manner to give mostly regular matter or are there spectral techniques to estimate the mass of baryonic matter? That is perhaps its just all "invisible" planet line or brown dwarf (?) like baryonic matter floating around not emitting ( absorbing) radiation because of the vastness of space and thus invisible and "dark?"
What we do is look at objects that we can relatively easily observe that we think are a good representation of primordial matter. In practice, this means interstellar gas clouds which haven't yet coalesced into stars, and very old stars of types that have little mixing between inner and outer layers (lots of these in globular clusters). This gives the ratio between elements in a more or less primordial sample of _baryonic_ matter.
From these ratios and the physics of fusion, we derive estimates for the amount of matter that's not baryonic (in the astronomical sense, not the particle physics sense). Until very recently this wasn't directly observable at all.
Actually btw since we are talking about H/He ratios since many galaxies, solar systems etc spin. I could imagine some centrifugal motion pushing the H out towards the edges (where we aren't getting the same measurements)
All of the material is in orbit, with cetripetal and gravitational forces in balance, so you don't get fractioning due to spinning.
In the solar system, we did get fractioning, but that was due to completely different mechanisms that don't apply to the galaxy (short version is that the sun blew anything light away from it).
i got the impression neutrino's mass limit was too low really to be anywhere close to any % within the 95 %
This is correct. It's just one component out of at least two and probably more.
These sound like very good criteria. The funny thing is that when I attempt to apply them to this guy I still don't know what to make of him. Are these respectable journals that he claims to have some of his papers published in? I am curious what you think of this whole deal.
A google search for "hydrino" brings up a fair bit of commentary on the topic.
The technical paper reads like crackpot material. He takes great pains to pooh-pooh current interpretations of quantum mechanics of electrons, and restates many times that it's "just a theory based on unprovables". That raises a rather large red flag.
More importantly, two problems with his scenario crop up:
If a lower-energy ground state of hydrogen existed, all hydrogen would already be at that ground state. The fact that we don't observe this (or, indeed, any natually occurring hydrogen in the "hydrino" state) puts the whole concept in question, as the proposed transition is very favourable energetically (so the resulting hydrino would form whenever it could and would be very stable).
Much as with cold fusion, this claimed effect has widespread enough practical applications that you'd get a *huge* amount of investment and R&D happening on it if a significant number of people thought it was real or even _might_ be real. The fact that they've failed to convince most of the scientific community raises a red flag.
I suspect that their proposed changes to quantum mechanics turn out to have very obvious effects on other systems involving electrons (like, say, semiconductors) that are easily shown to not be present, but I don't have the math background to grind through their claims and the materials equations to check this.
A list of skeptical responses to Blacklight Power's claims can be found at http://www.phact.org/e/blp.htm. As these pages set out to debunk the claims, you can argue that they are biased. However, they do make a good attempt to provide reasonable evidence/demonstration.
Summary: Almost certainly a quack. May or may not be a scam for investment money.
W/ regards to emissions, are we absolutely positive there aren't any methods by which absorption along the path from the object to us can throw off the measurements?
The short answer is "no". We know what this kind of spectrum looks like, and the measured spectra look exactly right. Absorption makes notches in the spectrum or attenuates parts of it, but doesn't change the overall shape much.
W/ regards to the 2nd statement, my understanding is that the "other argument" is something along the lines of we can work out how much baryonic matter is there from looking at (i think) nuclear synthesis and atomic element ratios (He/H) in the current universe. This estimate gives us some value like 0.05 % of the universe is baryonic and the rest of it is "dark matter"
My problem w/ this second argument for dark matter is that it seems much more plausible to me at least that our nuclear synthesis estimates are wrong or that our assumptions about what the He/H ratio is is wrong than inventing new set of matter that is supposed to be 95% of the universe.
We have great confidence in our models of nuclear interactions, because we've been able to test them directly for quite some time now. The measured ratios of H and He (and Li, which was also produced in the big bang nucleosynthesis period) are consistent in old star populations everywhere we check, and because all we need is light (to take spectral measurements with), we can check out to quite an impressive distance indeed.
The only variables have to do with the density and temperature and rate of expansion of the early universe. We can place quite strong limits on these by seeing what values are consistent with the resulting universe we see. It turns out that you only get a consistent answer if there's lots of mass that doesn't interact via EM. As this is consistent with other observations that point to a lot of missing mass (galactic rotation and the flatness problem), the conclusion drawn is that non-baryonic dark matter does indeed exist.
In summary, the case for dark matter comes from many independent observation approaches that are based on well-understood physics. That any given one of them might be wrong is possible, but with them all pointing in the same direction, dark matter looks like the best explanation.
We already even know what some of it is (neutrinos have mass and don't interact via EM).
"dark energy" comprises 70% of the matter-energy of the universe, yet we don't have theory for it, and we don't have a clue what it is.
Scalar fields left over from the inflationary period (several scenarios to choose from).
The cosmological constant, which may or may not be a special case of such a field.
The two fundamental theories of physics, General Relativity and the Standard Model of Quantum Mechanics, are fundamentally irreconcilable.
String theory and loop quantum gravity both reconcile them. Consequences are still being worked out, but there have been some fascinating conclusions drawn about black holes.
There is still no organizing principal for the zoo of fundamental particles.
Standard model pruned the zoo from hundreds to dozens. Symmetries among the particles reduce the number of unrelated variables even further. String theory makes these symmetries more explicit, but they're there in the standard model without string theory. Hard to get much simpler than "all fundamental particles are vibration modes of the same type of string", though.
There is still no organizing principal for the zoo of fundamental physical constants.
Last I heard, there were about 14 that were actually fundamental (could not be derived from others). I wouldn't call that a "zoo". If you take string theory at face value, some of these actually derive from circumstance (the size of various rolled-up dimensions). Indeed, with suggestions that some of the fundamental constants have shifted with time, a circumstantial source looks more plausible.
Sure, there are shake-ups down the pipe, but to call the current system as glaringly broken as the Ptolemaic model is throwing things a bit far. If anything, the really big shake-ups have already happened (standard model unified particle physics, and string theory and LQG have both made great strides in unifying classical and quantum mechanics). Next main events will be improvements in understanding of whichever unified theory prevails (or both, if they turn out to be equivalent), as opposed to tossing out a lot of what's currently taken as fact. Rather than looking at it as the overturning of the Ptolemaic system, look at it as being analogous to the refinement of the Copernican model into the solar system model we use today.
Slashdot Mirror
Van Ellen
Van Allen
Note to self: Proofread more.
But we're talking about a space station in earth orbit - which means that we're dealing with mostly high-energy protons and electrons (unless it's a *really* far out orbit).
Van Ellen particles are relatively low energy compared to what's coming in as cosmic rays, but I'd have to look up detailed numbers to comment much further on shielding.
The main thing that was bothering me about your previous post was that you were implying (perhaps unintentionally) that it's primarily the hydrogen that does the shielding, which is emphatically not the case (high-Z materials have more electrons to interact with and a larger nuclear scattering cross-section for most things, though I understand your point that it's not _desirable_ to scatter off of high-Z nuclei). If I've misunderstood your intention, my bad.
Googling duraluminum didn't help in discussing its suceptability to fatigue compared with regular aluminum, or say, steel.
Googling for "fatigue strength" and "aluminum" brough up a nice list of aluminum alloys. 2024 and 5052 have especially good fatigue properties compared to other aluminum alloys (though I'd need more googling to compare vs. steel). 2024 has copper as the primary additive, which meshes with what I recall of duraluminum (though I'm not sure if that's the actual alloy used; just that duraluminum is likely a 2000-series alloy).
Even in space, there are some serious risks, aggrivated by the fact that temperatures are so low and since you have such dramatic thermal cycling.
For a craft far from Earth, you typically make the shell thermally conducting enough that you don't get a large heat gradient across the craft for precisely these reasons. Spinning the craft also helps. LEO craft have problems because they usually pass through Earth's shadow on a regular basis. A Mars craft wouldn't suffer these difficulties (could keep an orbit perpendicular to the planet/sun axis when stationkeeping).
Admittedly, the proposed hotel is in LEO.
On a different topic - finally figured out why your name was ringing a bell. We'd had a discussion about asteroid mining in 2001, that was eventually moved to email. My address has since changed (twice, actually). It is good to see that you are still interested in space. My own space interests have tended towards medium-term future prospects instead of present ones (ran numbers for fusion craft a while back; conclusion: very hard to build useful magnetic confinement ones).
There's another real advantage to this method that hasn't been mentioned yet: radiation shielding. If you build your station out of plastic instead of aluminum, you'll get far better radiation shielding (it's the hydrogen atoms that do the best job!).
Depends on the type of radiation being shielded against. High-Z is better for gamma shielding (and shielding against secondary x-rays from other types of radiation, though using low-Z reduces the amount of this). You also have a bulk disadvantage with low-Z materials (though in space, it's weight and not bulk that matters, so you're stuck no matter what).
Furthermore, aluminum is a kind of nasty metal to use in extreme circumstances because as it warps, it stiffens and eventually will break (metal fatigue).
Aluminum itself has very low fatigue strength, but in practice aluminum alloys with better characteristics are used. Google for "duraluminum", an alloy commonly used for aircraft, for one example.
For space uses, the cost of launch dominates over the cost of materials, so you can afford to use as expensive an alloy or composite as you like in the structure. Materials problems typically occur due to design oversight (e.g. carbon composites being etched away by the atmosphere), as opposed to cheap materials being used.
Inflatable stations are still an interesting idea, though. If I recall correctly, the "Cosmos" solar sail was going to be inflatable, to save on mass (a rigid craft would have to be sturdy enough to survive launch, requiring extra mass).
However the i960CA and its followon the i960CF were pretty slick. The i960 had 32 general purpose registers, and a processor-defined function call sequence that always placed a set of 16 on the stack ("caller-owned") and left a set of 16 alone ("args , temp & return values"). The i960CA cached the top 4, 6 or 8 stack frames in on-chip static memory with a 128-bit pathway to the main register set. This gave it amazing function calling and interrupt service performance.
The UltraSparc did this as well (slightly different register layout, but same idea). I'm not sure when this was introduced (UltraSparc or earlier); anyone out there have a timeframe for Sun's implementation vs. Intel's?
The improvements that the 80486 brought was essentially a built-in FPU unit and faster clock speeds.
If I understand correctly, it was also the first x86 chip that had pipelining. This is why the "clock cycles" entries in that handy "xt-through-486" assembly reference booklet went from "5" to "1" for a whole bunch of instructions (instructions still took several cycles, but that latency was masked as long as dependencies didn't cause a stall).
Pipelining has been around for far longer than that, but it was a very significant x86 milestone.
You're promising not to reply to my posts, now please STOP DOING IT.
Fine. _I'll_ reply.
Gravastars are an interesting idea, but they:
a) Propose modifications to physics (the phase transition that gives rise to a different type of space in the interior).
and
b) Attempt to solve a problem that doesn't necessarily exist (embodiment of entropy in black holes, which string theory takes a fairly good stab at explaining).
Thus, I'm skeptical of claims that gravastars exist, barring observations supporting their existance or wider acceptance by the scientific community.
At least in the paper I've managed to dig up so far, they acknowledge many othe potential models of how black holes work, and suggest types of observations that would help determine whether their model is accurate (i.e., they don't claim it's the One True Model off the bat). This is one of the hallmarks of good science.
Observations to look for are gravity-wave signatures of resonance modes in the stiff shell surrounding the gravastar, and optical signatures of impacting matter interacting with this shell. The first should be possible when we get sufficiently sensitive gravity wave detectors online, and the second should be possible from observations of accretion disks in known black hole/other star binary pairs once Mazur and Mottola have worked through the math to figure out what the observational signatures should _be_. Thirdly, if you could get close enough to take good measurements, you'd be able to distinguish between gravastar-type black holes and Hawking-Bekenstein black holes by different radiation signatures coming off of them, but that requires being right next to the hole and having instruments sensitive enough to detect very faint, low-frequency thermal radiation.
In summary, claiming that the gravastar model _is_ what black holes are is very, very premature.
The primary limitation on even arbitrarily sophisticated nanotechnology which could prevent a runaway grey goo reaction is the lack of a sufficient source of energy. A nanomachine wouldn't be able to get much energy out of eating inorganic matter such as rocks because, aside from a few exceptions (coal, for example) it's mostly well-oxidized and sitting in a free-energy minimum.
It would instead get its energy from sunlight and distribute it electrically within itself. Catalyzed electrochemical reactions would break down silica-based minerals to provide more building materials.
This wouldn't allow transformation of the earth in the blink of an eye, but you'd still get rapid progress (picture nano-lichen that spreads across rock in a layer that grows thicker as underlying rock is digested). Heat of formation of SiO2 is about 14 MJ/kg, and it weighs about 2.6 T/m^3, for a decomposition energy of about 37 GJ/m^3. A perfectly efficient nanoswarm would eat into a rock face at a rate of about 0.1 m/year (given a solar duty cycle on the order of 10%). A realistic upper bound to system efficiency is on the order of 10%, giving about 1 cm/year.
So, areas could be actively protected against nano-infestation without much trouble (even with something as simple as a layer of paint), but unattended rock mass could be converted to nano-powder quickly enough to cause serious environmental problems in some situations (mountain rockfaces above the tree line sift nano-sand down on top of vegetation below, choking out plant life and lowering the tree line; lather, rinse, repeat, until what was a mountain range and foothill network becomes a desert).
This all assumes silicon-based nanomachines. Carbon-based nanomachines are more attractive from a construction point of view.
I consider disaster scenarios like this unlikely (among other things, the "desert" produced in the scenario above would quickly be seeded with vegetation, which would choke off its power supply). But, they're fun to think about.
One storage method that will work in many places is water, on a hill. About 10 cubic meters of water 1000 ft up stores about 1 MWh of energy.
It turns out that whoever provided you that figure made a rather grave math error.
1000 feet is about 300 metres. Gravitational potential energy near Earth's surface is 10 J/kg*m, so you get 3kJ/kg. Using 10 cubic metres gives you about 10T of water, or 10,000 kg. This gives you 30 MJ of stored energy - about 8.3 kW*h.
It looks like your source confused feet and metres, and then wrote MW*h when they meant MJ.
Practical gravitational power storage would require a huge resovoir (think "hydroelectric plant that you can run forwards or in reverse"). The basin size needed for, say, a day's worth of power storage for Ontario would be roughly the size of one of the Great Lakes. It is questionable that the construction of such a resovoir could ever be practical.
Add this to the logical fallacies. How do you think the grocery store refrigerates your food before you buy it? Now, how much would refrigerated goods cost to you (the average Joe) if refrigeration costs doubled?
You might even notice other goods and services increase in cost. It's silly to think that the cost of electricity is only reflected in your electricity bill.
You can get accurate values by looking at population and total power generation capacity in an area, getting the total per capita power consumption, and then multiplying that by the change in cost.
Up here (Ontario, Canada), we use an average of about 5 kW/person, for all forms of electricity consumption (personal, industrial, etc). That's about 44,000 kWh/year, or $2,200 Cdn/year in real energy cost (at $0.05/kWh; it's actually slightly less than this).
The cost of electricity could double, and while it would be annoying as heck, it wouldn't be catastrophic. Multiply by a factor of 10, and you're in catastrophe territory.
don't be foolish. Any idiot will just tell you to run everything on Hydrogen, which you can make from the electricity. So in a way, everything could be nuclear powered.
Hydrogen turns out to be a bad choice, due to storage problems (tends to diffuse out through most materials, and even at very high pressure can't be stored at a density that gives energy-per-volume comparable to fossil fuels).
A better choice is to use methane or methanol, either of which can be synthesized directly (burning hydrogen and CO2 for methane, partially burning methane and oxygen for methanol). They can both be stored at liquid densities (though methane has to be cryogenically cooled for that), can both still be used in fuel cells (reforming cells), and can both be used in conventional engines (gas turbines for methane, and either turbines or modified internal combustion engines for methanol).
I doubt that military vehicles, let alone aircraft, would use hydrogen as fuel, due to the large high-pressure storage tanks required. Methane might be practical, though picky. Methanol would be practical without problems.
Also, nuclear plants don't take up the *enormous* amount of space that wind or solar generation would require (a factor conveniently ignored by anti-nuclear activists).
Actually, solar isn't that bad. Energy density at this distance from the sun is high enough that the solar plant area required to power a given population is much less than the farmland area required to feed them, even with relatively low generation efficiencies.
The real problems are cost (even concentrating mirrors aren't free), and power storage and transport (you need to either hold a week's worth of power in reserve in case of bad weather, or hold a night's worth but always be able to draw power from somewhere with good weather). Concentrator-based heat plants area already cheap enough that they're being built as pilot projects. Thin-film photovoltaics continue to approach economic usefulness (and will probably surpass heat-engine based systems, due to conversion losses going from heat to electrical energy). Fuel cell technology is already mature enough that we could build power storage plants, but it requires enough of an outlay that we won't until we have to (or until voters force a tax break for reformer-based fuel cell plants that can generate power from fossil fuels before being switched over for power storage).
In summary, I think that solar power is the most practical of the renewable power source options, and will eventually be adopted as the price of fossil fuels creeps up (it's unlikely to run out overnight - we'll just move to less accessible/costlier sources until alternatives gain marketshare). Fission power, in North America at least, has political problems that will likely make it unattractive.
Is anyone researching fuel free launches?
I mean things like shooting the payload from a cannon or something..
The main problem is that any reasonable gun size requires thousands of Gs acceleration. That eliminates most cargo options (so you still have to use another launcher type for much of your cargo).
You're also limited by the atmosphere. While you *could* try to build a 1000-km long human-rated mass driver, you'd be plowing through the atmosphere at Mach Silly for most of the acceleration distance, and for hundreds of kilometres after launch (you're launching at a very shallow angle).
Techniques that try to deliver energy remotely while using atmosphere or carried mass as reaction mass run into the same problems as scramjets (for the first case) and conventional rockets (for the second case), in addition to requiring a large number of expensive installations for laser launchers or what-have-you.
Techniques that involve climbing up or being scooped up by an orbiting object require better materials than we can currently manufacture in useful quantities. In 30-50 years, this may change, but it's not a sure thing yet.
In summary, while there has been and still is a lot of research about fuel-free launch schemes, none of them are practical at this time.
As long as we need 100*X pounds of fuel to launch X pounds into space, space travel will remain uneconomical for most purposes.
Not true. Your cargo to craft (mostly fuel) mass ratio is 1:100 at worst. For a fuel as cheap as gasoline (and liquid oxygen is about this cheap in bulk), you get around $100/kg. Not cheap as dirt, but hardly cost-prohibitive. It's the vehicle itself and the facilities that drive the cost.
The problem is that right now the vehicles and the support facilities cost a _lot_ to build and maintain and staff and insure. This is where most of the money goes. Better materials and mature designs will reduce vehicle costs, which will help increase volume, which will further reduce costs from mass production and facility management scaling for at least a little while, but the cycle proceeds slowly. Give it time.
The last big experiment (reusable vehicles to save on vehicle costs) failed, due to increased complexity (for all designs), difficulty and expense of between-flight overhauls (for the shuttle), and difficulty meeting craft requirements with existing materials (all reusable craft, but especially SSTO craft). Now the focus seems to have shifted on reducing costs for disposable vehicles. We'll see in a couple of decades how this turns out.
Your point stands? It doesn't have a leg to stand on.
Let me spell this out for you.
A data transfer bottleneck makes interferometry suck just as much as it makes light-gathering suck, because in both cases you're throwing away most of your data.
An effective increase in signal-gathering capability by the factor of 30 you quote gives an increase in ability to distinguish signal from noise of about 5.5 (signal goes up as N, noise goes up as root N). This is piddling compared to the fact that, being no longer data-limited, you can take all of the interferometry measurements you like instead of having to play duty-cycle and array subset games to get around the network limitations.
The article focused on photon-collecting capability. Good for it. Doesn't change the validity of my statements.
Does this make things clearer?
If you RTFAs you should have noticed numerous references to the increased sensitivity of the new system in addition to the increased resolution.
Unless they are linking thousands of telescopes, they are getting one *hell* of a lot larger boost in resolution than they are in light-gathering power by linking telescopes. S:N improves as the square root of light-gathering power, further reducing the resulting improvement in sensitivity.
My point stands. Have a nice day.
Rather than call it a "network of telescopes" or an array, call it by it's name, an interferometer.
:).
Calling it a "phased antenna array" is perfectly valid. Just depends on whether you're talking to an astronomer or an electrical engineer
Also, I believe you're overestimating the technical savvy of most slashdot readers. Know thy audience.
Development of technology is amazing. I read somewhere a long time ago about and engineer (I think) who said his mother (I think) was afraid that we will lose control over the computers in a near future. His reponse was that this was very unlikely to happen, but he did believe that we already have lost control over development and technology advancements.
Once we can reliably produce computers that are smarter than we are, it's only a matter of time before they dominate society's workings. This isn't necessarily a bad thing, but there's no guarantee we'll particularly like the resulting state of affairs either. It could also just as easily end up being us who are the computers (using AI technology to enhance our own thinking as readily as we build self-contained thinking machines). Whether we'd still count as "human" under these conditions is a matter of philosophy, not science.
Very murky waters, and very difficult to predict which of the myriad of possibilities will actually happen.
Re. technology development, we're definitely at a point where if something would be useful or even just interesting to do, someone will do it (look at human cloning). The resources required for research are readily available, and there is no practical way to establish ironclad control over all research in the world at this time. Couple this with national competitiveness, and you get relatively unhindered development. This may eventually change through any of several methods (we reach a brick wall where all research is expensive [unlikely], we finish researching everything that has a practical/commercial application [unlikely any time soon], we unify under a global government that can and does restrict research [unlikely any time soon]). Combine this with some technologies that drastically lower the bar to research and development (like nanotech, if it can work as well as hoped), and you get this state of affairs continuing or even getting more extreme.
It will be interesting to see how it all works out.
Along those lines - how long until we have a telescope that can see far out/back enough that we can "see" the events even closer to da big boom?
There is a hard limit to how far back we can see - the point at which light and matter decoupled (when the whole universe was a plasma, it was opaque; when atoms formed, it became transparent). We can already see to this boundary in some bands. The cosmic microwave background, for instance, is the severely redshifted thermal radiation from this decoupling. Optically, if I remember correctly deep-field pictures went back a bit over 10 billion years, and the decoupling happened around 13 billion (or about 300k years after the big bang). So we're relatively close, but observation gets a lot more difficult at high redshifts (less energy reaches us, and there may not be bright, compact galaxies to see - though this itself would be a useful measurement to make).
An astrophysicist/cosmologist can give you more detailed answers on this than I can.
...(or how far out) will they be able to spy with this puppy?
The ability to see great distances requires a large number of photons to be collected (to pick up faint signals and better separate signal from noise), which requires a large aperture area. They're not getting that here, so they won't be able to see much farther.
What they _do_ get by using radio telescopes in tandem is a much larger effective aperture _diameter_, which lets them resolve finer details. What was once a blob or a point source of radio waves, now resolves into jets from an active galaxy, or what-have-you.
This doesn't require a fiber link (they're using microwave links to exchange data between the Merlin telescopes now), but a fiber link lets them transfer more data and so do the data processing a bit more efficiently. Same telescope array, better throughput (so more of the captured data can actually be analyzed).
I find it very interesting that we've come so far in the understanding of space, but we still have but scratched the surface. I would love to be able to hibernate for say 100 years, and then find out where we're at in technology, space flight and exploration.
For telescopes, you won't have to wait more than 50 years, tops. Optical intereferometric telescopes have been built that do much the same kind of thing that these radio telescopes do (huge effective aperture diameter from many smaller telescopes, letting you see relatively bright objects in fantastic resolution). Space-based ones are in the planning stages now, and will be launched well within your lifetime. This will allow us to do detailed surveys of nearby solar systems.
A sun-orbiting array of radio telescopes would also be useful, for similar goals (and to make really accurate maps of our own galaxy's interior, and give a better idea of the structure of nearby galaxies). No idea if anything like this is on the drawing board just yet. If anything, it'd be much easier than an optical array.
Technology-wise, we're likely to have mature materials and fabrication technology 100-150 years from now, either through nanotech or through more conventional synthesis techniques. That will let us build just about anything we want to that's within the theoretical limits of materials built from ordinary matter. We'll also likely have true AI. Whether the world looks like an updated version of our current one, or whether we go through a Vinge-style singularity into a very different type of world, is something our grandchildren will find out (I'd like to live that long, but I'm not going to bet on it just yet).
I think hydrogen may have potential in that application. It's a reasonably efficient way to move energy around. You have to use some kind of energy to produce the hydrogen, and it would be far better to do it with solar than with fossil fuels.
Solar cells are actually very good for this purpose, as electricity is produced directly, as opposed to having to be converted from another energy form (like heat, in the case of a coal or oil fired power plant).
You can produce hydrogen from fossil fuels fairly efficiently by "reforming", though. What this essentially does is strip hydrogen off of hydrogen-rich hydrocarbons, giving you carbon-rich hydrocarbons and hydrogen gas. The hydrocarbons can still be burned in a suitably tuned power plant, and the hydrogen gas can be used in fuel cells.
If you're using a fuel cell for storage, as opposed to generation, though, you'd just keep the water produced when you feed hydrogen and oxygen in it, and break that down to get your source gases back out (though you'd probably dump the oxygen instead of storing it, since you can pull more out of the atmosphere easily).
The real problem with hydrogen as a storage medium is difficulty storing it at any reasonable density (cheaply - we can't afford palladium storage cells, and they're horribly heavy anyways).
Or it might be a way to bridge the energy gap in ethanol (either for combustion or in fuel cells), where currently you have to burn an amount of fossil fuels to produce the ethanol, some say more than you get out.
You'll always use more feedstock than you get ethanol out, so I assume you're talking about power spent converting the feedstock to ethanol.
I actually think that alcohol makes a better storage medium than hydrogen, because it's easy to store, can be burned in internal combustion engines, and can be reformed (see above) and used fairly efficiently as a fuel for fuel cells. The only catch is that it's annoying to synthesize. Methane can be synthesized relatively efficiently, and you can partially burn it to produce methanol, but that's still not very efficient.
Probably efficient enough for many applications, though (you don't care much if your notebook takes twice as much power to charge as you get stored in the battery, even if you do care for things like your car, and even more so for a city's "week of bad weather" power reserve).
At the moment I'm more worried about being in thrall to a rather unstable part of the world for oil than I am about the atmosphere's CO2 load, but it is also pretty scary.
I'm somewhat puzzled by this situation, as it appears to be one of choice as opposed to necessity. Here in Canada, we could get all the oil we'd need for quite some time from Alberta, and there are enough offshore natural gas reserves to satisfy that demand as well. Last I heard, the gas reserves off the US's coasts were *huge*. We'd see a price increase switching to local supplies (maybe even a hefty one), but nothing that would bring western society crashing down.
After those ran out, a century or two down the road, Canada has enough uranium to last us indefinitely, and the political will to use it for power. The US would need a creative political gimmick to be able to use it now, but a century is more than enough time for public opinion to change. Even without a breakthrough in power production, I don't see any serious problems.
All those green freaks don't realize we generate 10x the pollution making solar cells as we do generating the same amount of electricity for grid-use.
This turns out to no longer be true. Look up thin-film cells, which are both cheap and low materials use.
I simply don't know enough about the physics, but... can this be applied with the other developments like multi-band gap improvements?
:).
I'm on shaky ground here, but I think the answer is likely "no". The idea behind this technique is that you can use surplus energy from a photon absorption event to release a second electron, while the point of split bandgap cells is that you can absorb light with less surplus energy (more deposited in a useful manner into the first electron).
Ask a semiconductor physicist to get the correct answer
So if you really want to know what's going on you need to discover how efferent lead selenium solar cell's are and what it takes to mass produce lead selenium nanocrystals in a cheep long lasting solar cell.
Nanocrystal films would typically be grown by chemical vapour deposition (chemical constituents react as a gas at low pressure, seed crystals grow in-flight, and grow further after being deposited).
The problem is that it's very hard to produce crystals that small (they tend to keep growing after being deposited, because the source materials are still present - this is how you normally do CVD, actually). You also have difficulty producing a narrow range of sizes, because that requires that the growing environment of each crystal be identical.
Still an interesting discovery, though. The fabrication problems will eventually be solved.
What's especially interesting is looking at what happens when you fabricate oher types of semiconductor microstructure or nanostructure by more conventional techniques. As the size of a feature shrinks, you can no longer pretend it's near-infinite in extent when figuring out what the energy levels are within the crystal. This has already been used to alter the properties of silicon (fabricating LEDs in silicon, which normally emits very poorly due to having an indirect bandgap). Quantum wells, wires, and dots are an extreme case of this (dimensions comparable to a few electron wavelengths). When lithographic feature sizes start approaching this range, lots of new devices will be possible in mass-market chips that are only possible now if you have an e-beam lithography setup handy.
W/ regards to our models of interactions and and extrapolations from the big bang to the present day and nuclear synthesis models, the impression I get whenever I see them is that they are vaguely phenomonalogical. They don't seem to me to be the equivalent of say.. maxwells equations but closer to say mathematical biology / population biology models (perhaps this isn't fair). Is it possible that these models may be wrong in some manner to give mostly regular matter or are there spectral techniques to estimate the mass of baryonic matter? That is perhaps its just all "invisible" planet line or brown dwarf (?) like baryonic matter floating around not emitting ( absorbing) radiation because of the vastness of space and thus invisible and "dark?"
What we do is look at objects that we can relatively easily observe that we think are a good representation of primordial matter. In practice, this means interstellar gas clouds which haven't yet coalesced into stars, and very old stars of types that have little mixing between inner and outer layers (lots of these in globular clusters). This gives the ratio between elements in a more or less primordial sample of _baryonic_ matter.
From these ratios and the physics of fusion, we derive estimates for the amount of matter that's not baryonic (in the astronomical sense, not the particle physics sense). Until very recently this wasn't directly observable at all.
Actually btw since we are talking about H/He ratios since many galaxies, solar systems etc spin. I could imagine some centrifugal motion pushing the H out towards the edges (where we aren't getting the same measurements)
All of the material is in orbit, with cetripetal and gravitational forces in balance, so you don't get fractioning due to spinning.
In the solar system, we did get fractioning, but that was due to completely different mechanisms that don't apply to the galaxy (short version is that the sun blew anything light away from it).
i got the impression neutrino's mass limit was too low really to be anywhere close to any % within the 95 %
This is correct. It's just one component out of at least two and probably more.
A google search for "hydrino" brings up a fair bit of commentary on the topic.
The technical paper reads like crackpot material. He takes great pains to pooh-pooh current interpretations of quantum mechanics of electrons, and restates many times that it's "just a theory based on unprovables". That raises a rather large red flag.
More importantly, two problems with his scenario crop up:
I suspect that their proposed changes to quantum mechanics turn out to have very obvious effects on other systems involving electrons (like, say, semiconductors) that are easily shown to not be present, but I don't have the math background to grind through their claims and the materials equations to check this.
A list of skeptical responses to Blacklight Power's claims can be found at http://www.phact.org/e/blp.htm. As these pages set out to debunk the claims, you can argue that they are biased. However, they do make a good attempt to provide reasonable evidence/demonstration.
Summary: Almost certainly a quack. May or may not be a scam for investment money.
W/ regards to emissions, are we absolutely positive there aren't any methods by which absorption along the path from the object to us can throw off the measurements?
The short answer is "no". We know what this kind of spectrum looks like, and the measured spectra look exactly right. Absorption makes notches in the spectrum or attenuates parts of it, but doesn't change the overall shape much.
W/ regards to the 2nd statement, my understanding is that the "other argument" is something along the lines of we can work out how much baryonic matter is there from looking at (i think) nuclear synthesis and atomic element ratios (He/H) in the current universe. This estimate gives us some value like 0.05 % of the universe is baryonic and the rest of it is "dark matter"
My problem w/ this second argument for dark matter is that it seems much more plausible to me at least that our nuclear synthesis estimates are wrong or that our assumptions about what the He/H ratio is is wrong than inventing new set of matter that is supposed to be 95% of the universe.
We have great confidence in our models of nuclear interactions, because we've been able to test them directly for quite some time now. The measured ratios of H and He (and Li, which was also produced in the big bang nucleosynthesis period) are consistent in old star populations everywhere we check, and because all we need is light (to take spectral measurements with), we can check out to quite an impressive distance indeed.
The only variables have to do with the density and temperature and rate of expansion of the early universe. We can place quite strong limits on these by seeing what values are consistent with the resulting universe we see. It turns out that you only get a consistent answer if there's lots of mass that doesn't interact via EM. As this is consistent with other observations that point to a lot of missing mass (galactic rotation and the flatness problem), the conclusion drawn is that non-baryonic dark matter does indeed exist.
In summary, the case for dark matter comes from many independent observation approaches that are based on well-understood physics. That any given one of them might be wrong is possible, but with them all pointing in the same direction, dark matter looks like the best explanation.
We already even know what some of it is (neutrinos have mass and don't interact via EM).
"dark energy" comprises 70% of the matter-energy of the universe, yet we don't have theory for it, and we don't have a clue what it is.
Scalar fields left over from the inflationary period (several scenarios to choose from).
The cosmological constant, which may or may not be a special case of such a field.
The two fundamental theories of physics, General Relativity and the Standard Model of Quantum Mechanics, are fundamentally irreconcilable.
String theory and loop quantum gravity both reconcile them. Consequences are still being worked out, but there have been some fascinating conclusions drawn about black holes.
There is still no organizing principal for the zoo of fundamental particles.
Standard model pruned the zoo from hundreds to dozens. Symmetries among the particles reduce the number of unrelated variables even further. String theory makes these symmetries more explicit, but they're there in the standard model without string theory. Hard to get much simpler than "all fundamental particles are vibration modes of the same type of string", though.
There is still no organizing principal for the zoo of fundamental physical constants.
Last I heard, there were about 14 that were actually fundamental (could not be derived from others). I wouldn't call that a "zoo". If you take string theory at face value, some of these actually derive from circumstance (the size of various rolled-up dimensions). Indeed, with suggestions that some of the fundamental constants have shifted with time, a circumstantial source looks more plausible.
Sure, there are shake-ups down the pipe, but to call the current system as glaringly broken as the Ptolemaic model is throwing things a bit far. If anything, the really big shake-ups have already happened (standard model unified particle physics, and string theory and LQG have both made great strides in unifying classical and quantum mechanics). Next main events will be improvements in understanding of whichever unified theory prevails (or both, if they turn out to be equivalent), as opposed to tossing out a lot of what's currently taken as fact. Rather than looking at it as the overturning of the Ptolemaic system, look at it as being analogous to the refinement of the Copernican model into the solar system model we use today.