Not on any chip or motherboard I've seen offered for sale. It was going to be introduced with the Hammer/Opteron chipset.
But the other architectural improvements are going to make x86-64 a must-have for people LONG before the 4GB barrier being shattered will matter to the majority of computer users. Those extra registers will mean an instant performance improvement for everyone as soon as apps are recompiled to take advantage of them. They'll boost throughput quite a bit for video encoding/playback, same for 3D gaming.
3D gaming is primarily limited by your graphics card. Has been for quite some time.
Multimedia already uses the SSE vector register set, and so won't get much of a performance boost.
Add to that the fact that register renaming has been making register count less of an issue for years, and the strength of this benefit looks smaller and smaller.
It'll still _help_, but don't expect a larger register set to give a _vast_ performance boost.
Except that spread-spectrum transmissions can actually Transmit BELOW the noise-floor, so therefore can also Receive data BELOW the noise floor.
They transmit below the noise floor of narrow-band transmissions with the same data rate. All you're doing is switching from frequency space to code space. The noise floor is still there, it just looks different.
Do all the code division multiplexing you want - detector sensitivity still limits what you can stuff into a given region of the spectrum, with the math described in my original post. Whether you're doing it by having a thousand 1-kHz signals in separate bands or a thousand 1-MHz spread-spectrum signals in the same band is immaterial.
When the world of personal computing was young, and new compression utilities seemed to be coming out every week, every so often you'd hear someone claim that they'd achived the holy grail - written a compression program that could compress its own output, or compress arbitrary files 100x, or perform some other impossibility. Wise people didn't believe them, because information theory strongly limits your ability to compress arbitrary data.
In recent years, we've started hearing similar claims about the spectrum. Remember when impulse-based signal transmission was going to give us limitless bandwidth? This is more of the same.
First, I'll explain the limits to transmission bandwidth. Then, I'll explain how Mr. Lessig is planning to get around them. Finally, I'll explain why it doesn't work.
The spectrum, at the location of any given broadcast transmitter or broadcast receiver, is limited. The bandwidth - range of frequencies - available is fundamentally limited by the receiver's sampling rate (or frequency cutoff, for analog signals). There is no way to get around this, short of using more of the spectrum (by having a higher frequency cutoff). In the past, it was difficult to access even this much, due to the nature of the electronics used (response wasn't perfect, filtering wasn't perfect), but modern electronics are much better (as Mr. Lessig points out in his radio airplane example). The bandwidth limit, however, remains.
The amount of information you can transmit within a given region of the spectrum doesn't depend solely on the bandwidth - it depends on both the bandwidth and the fidelity of your sampling within the band of interest (how many levels you can decode without noise if you're quantizing, or what your signal-to-noise ratio is if you're using a fully analog system or a digital system with very high fidelity). The number of bits of information you can stuff into a spectrum region per second is the log to the base 2 of the number of levels you can reliably distinguish from each other.
This limit applies to any limited-bandwidth signal, regardless of the encoding scheme used. Use spread-spectrum transmission to smear a narrow-band signal over a wider region of the spectrum, and the limit just tells you how many signals you can broadcast this way before the noise floor swamps all signals. The mention of spread-spectrum transmission in the article is a red herring - it doesn't gain you data capacity (it's used for other reasons).
If your system is purely a broadcasting one - sending in all directions, receiving in all directions, no wormholes or relays - this is the best you can do.
You can improve the situation somewhat by trying to beamcast messages instead of broadcasting them. However, this still has problems. Firstly, your "beam" is really a cone. Secondly, your transmitter/receiver is larger, as you need a dish or a carefully shaped antenna or a large array of antennas and some signal processing to get direction-selectivity. Both are caused by diffraction limits related to the wavelengths of the signals being used - a fundamental process that can't be avoided. Thus, while it's used for transmitters (take a look at a cell tower some time), it's not practical for receivers. Either way, you end up with a fixed, finite gain in capacity, as the narrowness of a transmitter's beam can't be made smaller than a certain amount without requiring an extremely large transmitter.
So what about the idea of having short-range transmitters/receivers, and relaying between them? Well, this works to some extent. However, you must have a non-broadcast backbone. Solely relying on the short-range units for signal relaying bogs down very quickly. Consider an area with transceivers uniformly distributed in it, with source and destination points for any given communication chosen at random. Draw a line through the middle of the region. With N transceivers, the number of signals crossing the boundary goes up as O(N), but the number of nodes on the boundary that can do
If you define the universe as everything related to the Big Bang, then we couldn't we conceivably interact with other universes? A part of our universe could already be interacting with a "nearby" universe resulting from another big bang or some previous collision of universes(it's effects would only travel 1ft/ns, light very slow on the cosmic scale, or if you're trying to make fast processors, but that's another discussion.)
You seem to be missing the point of my original statement - there is no larger space in which our universe and other universes exist. "Space" is only defined within our universe.
If you MUD, think of the universe as being an ungodly-huge number of nodes (each of planck radius) connected by links. The fact that any given MUD is finite or has recognizable geometry doesn't mean you'll suddenly have a collision between PernMUSH and KillEverythingMUD.
In summary, there is nothing accessable for our universe to interact with, in the simplest scenario.
If inflationary bubbles are embedded in a larger space, then you just have disjoint regions of the same universe. Inflationary bubbles could collide in this scenario; the results would involve the flow of vast amounts of energy, and the intersection region would probably be moving faster than light (no visible effect, just sudden engulfing).
However, as both inflationary bubbles would be part of the same universe, several components of the physics of each bubble would be the same. How many, no-one's sure.
I personally don't think the embedded-bubble scenario is as plausible, because it postulates more complex behavior for the scalar field (a metastable vacuum state must exist (local minimum) above the global minimum).
A different dimension. Maybe another alternate universe. Our donut may be one of many other donuts. As far as 4th-dimensional creatures like us our concerned, if you could look from 'outside' our universe, everything could look like a big blob within a dark void
As the donut (or sphere or what-have-you) represents space itself, the concept of something "outside" it doesn't really work. Only relationships between different parts of the universe are defined. Treating the universe as the surface of some object is just a trick to make it easier to visualize (otherwise it would just be a set of functions defining relationships between points).
Some of the inflationary models put the universe we can interact with within a larger space, but that just gives us disjoint parts of one larger universe. Much like the event horizon of a black hole, the interface between them would represent a boundary across which interaction and information flow is restricted, and different space/time coordinate systems would be used inside and outside them. (The inflationary bubble looks like an infinite space from the inside and an expanding bubble from the outside; all points on the boundary look like they're at the beginning of time from the inside.)
So, no Voyager-esque bright expanding shell or external vantage point in the simplest scenario, and something a bit different from what you're probably envisioning in the various inflationary models that posit bubbles within larger spaces.
Why do we even assume a simple symmetrical shape? For example, what is to stop universe from being Klein bottle shaped? Or perhaps the universe is a hypersphere, but has dimples like a golf ball. I'm really curious.
If the universe began as a point object (planck-scale sized) and was extremely uniform to begin with, then this uniformity would be reflected in its shape later in life.
OTOH, some of the newer ideas about scalar fields and self-replicating universes would give a contorted, infinitely complex shape on a large scale (imbalances would magnify themselves).
The simplest answer is "because it makes the math easier" (cue mathematician/physicist/engineer jokes...).
no, In Canada, Co-ops are not paid. In Canada internships are paid...
High school co-op != university co-op. The latter is an internship, for all practical purposes.
At the University of Toronto, it goes for 12-16 months once instead of multiple places in 4-month stints, which has both benefits and drawbacks vs. the Waterloo method (you can work on bigger projects and learn more, but if you get a bad employer, you're stuck with them).
Balogna. The result of burning garbage doesn't necessarily have to be CO2. Plasma burners yield H20 after they are finished processing the H2 and CO that come out.
If you have carbon going in, you have carbon going out.
Burn it in an oxygen-poor environment or play reforming games, and you get the carbon out as tar or particulate carbon instead of CO2 (mostly), but it still comes out.
Plasma burners or other high-temperature incinerators are also *extremely* expensive to run compared to more mundane incinerators. They're used for PCBs and other difficult-to-decompose hazardous wastes, and not much else.
Of course, we've known this for years. Anyone who tells you otherwise is an environmentalist who refuses to accept the facts. The amount of money it costs to take a piece of plastic, paper, glass or whatever and recycle it into another one is more than the cost to create that item from unrecycled material.
The problem is the source of unrecycled material. While we have no shortage of things like metals, and while fossil fuel reserves are large, I know that here in Canada we're converting forests to wood pulp at an alarming rate, and my understanding is that the US has already mostly finished this process and is importing from us.
When the forests run out - easily within my lifetime - we'll either be stuck farming trees for lumber and wood pulp, with a manyfold increase in lumber and paper costs, or have to use recycled paper (paying more than we do now, but less than we would with tree farming as the sole source of supply).
Personally, I'd rather we used steel and concrete for building and recycle paper and keep the forests. But that's just me.
We'd still have to farm trees, as recycling would never be perfectly efficient and some applications (like food wrappings) need to be made from new material, but we'd stand some chance of halting the full-scale deforestation that's going on now.
Lastly, if we think that recycling technology will ever get better in the future, it's best to get people into the habit *now*, so that we aren't stuck trying to retrain the populace down the road.
It's always a race. For example, if we don't come up with a method to crack 2,048 public key encryption, someone else will. You can't assume it could only happen by perfecting a quantum computer; someone could find a way to calculate products of primes quicker. The point is, it's not a matter of if, it's when.
[I'm assuming you're talking about RSA, as you're mentioning products of primes.]
The universe, however, feels no need to bow to human ingenuity. By what reasoning do you conclude that a non-quantum polynomial-time factoring approach exists?
Non-polynomial of *any* speed doesn't help you, if the person making the key was smart enough to add a few extra bits. Exponential problems are nasty that way.
A more intelligent approach is to say that a polynomimal- or near-polynomial time factoring algorithm *might* exist, and try to assess the chance of it a) existing and b) being discovered given an assumed amount of effort for a time window of interest. Remember, the NSA's been working on it for quite some time, with no apparent results yet.
A _wiser_ approach, given the apparent security of the encryption itself, is to look at other vulnerabilities of the system you're trying to protect.
Use the excess power during the day to move mass against the moon's gravitational field and harvest that potential energy during the night.
This would require extremely large amounts of mass for most practical distances. Power to weight ratio is very poor; even very modest temperature elevations store an amount of power comparable to lifting the same mass many kilometres in the air. Carnot efficiency is as good as we want it to be, as space is our heat-sink (though we get better throughput sinking by conduction to ground instead of radiation to space).
The only reason gravitational storage is used at all on Earth is that water is a very convenient and abundant storage medium and nature often provides large resovoirs for us. On the moon, we'd be trucking bricks up a convenient mountain and still be getting lousy power storage.
Leave the Earth, think on Moon! Nobody needs shields there, nor compactness. Reactor can be made without any of the usual safeguards.
Electronics and ionizing radiation do not play well together, unless you plan to build your computers out of vacuum tubes. The reactor housing itself also degrades at a rate proportional to the amount of radiation it receives.
Lastly, the plumbing, turbines, and radiators for a high-power closed-loop plant will weigh far more than the shielding. You only get a tiny high-power plant if your working fluid is free and all you're trying to do is heat it up (c.f. NERVA and the nuclear aircraft experiments).
Well, it depends if you want thermal energy, or electrical energy. If it's mostly thermal and some mechanical, a nuke is very efficient and you can fit it in 4 tons or less, shielding and all.
You need electrical if you want to have closed-loop smelting, as at some point you have to electrolyze either the ore itself (in the case of aluminum) or some derivative of the material you're smelting with (e.g. Fe2O3 + C -> Fe + CO2, CO2 + H2 -> H2O + CH4, CH4 + O2 + shennanigans -> H2O + mostly C, H2O + electricity -> H2 and O2 to repeat the process).
I also strongly suspect that the amount of heat needed by heat-driven industry is beyond that available from a reactor it's practical to lift. If the moon is to produce a useful amount of material for space projects, final power requirements would be gigawatts at minimum.
A smaller plant might jump-start the smelting, but packing a lot of thin-film cells on mylar instead would probably give comparable or better power density during the day and cause far fewer hassles getting approval for the mission.
But, and this is a very important but, since all humans live on one planet right now we are playing for all the marbles. I'd rather not take any chance that can be eleminated. If we had self-sufficient colonies elsewhere I wouldn't worry about something unlikely to happen, but we don't.
Sure, I'll agree with this, but it doesn't have relation to the "we should move all industry to space" argument. Space colonization will happen as an inevitability - all it requires is a small group scraping together the minimum resources required, and the barrier to entry is (slowly) going down. Moving industry to space is an entirely different matter.
Re: Resources. At this point I think you are a bit like a person in the early 20th century telling me that automobiles are pointless because we will always have enough horses. It is certainly true that we have resources not yet exploited However these resources are inherently limited. Large yes, but infinate no.
Sufficiently close to infinite for all practical purposes. Energy dumped into the climate engine is on the order of 1e16 to 1e17 watts. Terrestrial power consumption is about 1e13 watts. If we want to go nuclear, crust abundance of thorium is about 6 ppm by weight. This gives about 3e11 tonnes in accessible regions of the Earth's crust. Assuming 1 MeV per particle potential energy and a capture efficiency of 10%, we have about 1.3e15 moles, or 8e38 particles, or 8e43 eV, or about 1.6e25 joules - enough for about 50,000 years. Even dividing this by the fraction of accessible thorium that's easily extracted, we have plenty of time to build up our solar heat engines or invest in future technologies like fusion.
As for materials, the crustal abundance of just about *anything* gives more than we could ever need within easy reach. The earth could be populated at standing-room-only and we'd *still* be limited by energy and not matter.
It is absolutely true that at the moment it is cheaper to build on Earth. In the early 20th century it was cheaper to use horses, yet you may have noticed that we use cars today. Technology will improve, that's a given.
Technology is limited by physics, and physics decrees that we're stuck in a 60 MJ/kg potential well. Even with a space elevator with a magical transport system capable of arbitrary volume, it would cost a non-trivial amount to lift material out of the gravity well (low, but non-trivial; think of it as an export tarrif, and you're in the right ballpark). In practice, I'm skeptical of ground to orbit costs ever being anywhere close to the theoretical minimum - the rate of cargo transfer along a space tether is sharply limited, and the tether has to amortize its construction and maintenance costs over its maintenance lifetime. Moving things down along a tether and from other orbits to the top of the tether in the first place will cost more than zero, which gives an added cost that ground-based industry doesn't have (both still need ground transport, so the tether has no advantage there either). I do not believe that it's intrinsically cheaper to produce any material object in space than on Earth, so there's no savings to offset this added cost.
As for energy, you have transport losses, and you have the the microwave beam problem unless you have a power cable running along the elevator, and you have the cost of maintaining a huge structure if you're generating based on solar power. On Earth, you can let the climate engine concentrate solar power for you.
In summary, I don't see how space-based industry or power generation will have an advantage at *any* level of technology, if the market is on Earth.
As for room, most of the real-estate you mention is undesireable in the extreme. Additionally, we require more than living space. We need space for farms and ranches to grow our food. We need space for factories to build our computers. We need space for...
Re-read my message. And then dig out that atlas I suggested - one which has maps of land use. Industry and population centres take up almost no area - human sprawl is almost all farmland. This will never, ever be moved to space, because it's easier to build a giant farm-factory on Earth than it is to lift one into orbit and bring the produce back down, if space becomes a limitation.
If we need more space, it will be for farmland, not anything else.
Fossil fuels are inherently limited, no arguing that there are oil fields yet untapped, but eventually we will run out.
The climate engine will run out when the sun burns out, at which point we will have bigger problems than a lack of electricity. Fossil fuels will be used until scarcity and/or cost of clean-up makes alternatives like nuclear and widespread hydroelectric or solar heat-engine generation cheaper. Running out will be a gradual process of increasing cost of extraction, not a cliff.
Again, at the moment, building an orbital power collector is prohibitively expensive. But the moment will pass.
This is a perfect example of the assumption you're making that I just don't get. Why is it cheaper to build a big solar collector in space than it is to build the same solar collector on Earth? Or to build a power station that uses the land, air, and sea to do the collection for you? Any scenario that brings construction cost down in space is likely to bring it down on Earth too (ultra-tensile cable materials let you build much thinner panels or reflectors on Earth, for instance).
You seem fixated on a space-based solution without looking at any of the alternatives.
The moon's crust is largely silicates, and with thin films even a relatively small smelter/purification plant will get you an impressive acreage in solar collectors.
Plenty of silicon dioxide, not much hydrogen or carbon. Hardly any, in fact, and you kinda need them to manufacture solar cells.
How so?
You'll certainly use many chemicals in the smelting, but the final product is nearly-pure silicon on an arbitrary substrate (glass works fine). Chemicals used in smelting will be recycled in as close to a closed-loop scheme as possible, because they have to be imported from Earth.
The cells themselves contain silicon with trace amounts of phosphorus and arsenic for dopants, and aluminum for wiring. Not a lot of hydrogen or carbon there.
Manufacturing aluminium takes a lot of energy, 20 kWh for a single kilo. Where are you going to get all that power, since you can't manufacture solar cells?
From solar cells, which we _can_ manufacture, or from the partially-built heat engine, or from the smaller power source of whatever type that powers the initial smelter.
Remember, one (1) square metre of lunar surface can smelt a kilo per Earth day by your calculations. Even with 5% efficient power generation, the collector area required is about the size of your living room. One kilo of aluminum gives at least one square metre of mirror area, or can coat a much larger area of glass mirror. Growth rate is fast.
You'd be better off importing a submarine-style nuclear reactor from Earth.
Nope. The power to weight ratio is too lousy to run your entire industry off of this or any other power source transported from Earth. You'd probably send a few RTEGs to run control electronics during lunar night, but that's about it.
This "lunar day" is not the length of a day on the moon. It is the interval between the moon occupying the same position in the sky on successive days for an observer on Earth (one Earth day, plus adjustment for the moon moving along its orbit).
The moon is tidally locked to Earth, and rotates once per orbit (about 28 Earth days).
One of the things we can get from space that does not occur naturaly on Earth is Iridium. We know that it has myriad uses, but we simply don't have much of it because it is not native to Earth.
Sure it's native to Earth. It's just about as rare as the other metals in the same region of the periodic table (little things like platium, palladium, and so forth).
We don't have enough to mass-produce things out of it (just like you're not likely to build a kitchen table out of platinum for every family on your continent), but we've had ample opportunity to _research _ it.
You're probably thinking about the K-T boundary thing from geology. What they found was a layer _rich_ in iridium, and containing specific isotope ratios that were not associated with terrestrial deposits. Asteroids are most definitely not the *only* source.
On a more pragmatic note some industry MUST be located off planet for safety reasons. Research into nano-scale assemblers is an excellent idea -- as long as a mistake can't turn the planet into grey goo. Orbital facilities seem ideally suited for this.
Life has had billions of years to spend working on improvements to self-replicators, and has not yet produced "grey goo". I am not convinced that it's possible to produce self-replicators much more efficient than the ones that already exist (if it was possible, why haven't they formed and outstripped the existing ones?).
Even if you assume a drastically improved self-replicator is possible, it still has to get its energy from somewhere. Even sucking up all available solar and checmical energy from a local area gives a strongly limited growth rate. You'd get something closer to grey mould than the all-devouring goo scenario. Not only do you have to put in the initial energy to convert material from stably-bound checmical forms to something you can use, but you have to keep putting in energy to maintain your highly-ordered, higher-energy constructs against natural decay (you can smelt rust into iron, but it doesn't take long to start turning into rust again).
In summary, I don't think grey goo is a risk we have to worry much about.
Finally, there aren't many other games in town. Terrestrial industry is already facing large problems of overcrowding, pollution, and energy shortage. If we limit ourselves to terrestrial industry it is literally impossible to build a car for every person in China due to a lack of energy and raw materials.
We appear to be operating in different universes. Given enough time, China can produce any amount of cars. Given sufficient industry, it can build those cars quickly enough to finish building them before the first cars stop running them. Whether it currently has the required industry is immaterial - it can build it.
We have vast deposits of fossil fuels in the ground and under the ocean. We have enough easily accessible uranium in the world to power a first-world civilization for centuries. We have enough thorium and other materials to breed new nuclear fuel for thousands of years.
We have a giant fusion plant in the sky that won't burn out for several _billion_ years. Large-scale solar production via heat plant is practical; it's just more expensive than current production methods, so it isn't done. We already tap it indirectly in the form of the climate engine; hydroelectric power stems from this source and is widely used (let the oceans be our solar panels and the rains our cabling). Energy won't be a problem - and this is just using existing, well-proven technology.
In summary, I see no shortage of either power or industrial capacity on Earth.
Space allows us to generate huge amounts of power, has raw materials that are accessable without harming any environment, etc.
We simply don't have the room here on Earth for enough industry to provide first-world luxury for all humans
Now I know we're operating in different realities.
What makes you think a space-based solar generator will be more economical to build than a ground- or ocean-based one? What makes you think bombarding the earth with material from the moon won't have an environmental impact? (Remember the last couple of big volcanic eruptions? Dust matters.) What makes you think that giant microwave beams dumping heat comparable to the entire power production of earth cause less environmental harm than hydroelectric dams or fission plants? What makes you think it's economical to mine material on the moon or from asteroids at all, if the target market is terrestrial?
Materials and power from space are only easily accessible to other things in space. Planets are *huge* treasure-troves of material and power - the only reason we wouldn't *export* to space is that our gravity well makes material transport expensive.
As for room... Take a look at an atlas some time. Most of the space used by humans is farmland. You're not moving that to space. If you were at the point where you were considering it, you'd instead just build in-building farms on Earth - it would be similarly expensive, and shipping would be easier. In practice, we'll just move our consumption down the food chain and find a way to make algae and bacteria cultures taste good.
Space taken up by industry and population are negligeable by comparison.
The exception is the lumber industry. When natural forests are used up, or are preserved by law, forestry will finally shift to being a conventional farming industry, and the price of lumber will change appropriately. Materials use will shift a bit towards metal and concrete in response.
As for the fundamental resources available... We're sitting on a big ball of aluminosilicates. We have enough material for *anything*.
In summary, there is no shortage of power or materials on earth, and per-capita industrial production can be adapted at will by building up industry. In most cases, moving production of anything to space will cost _more_ and have worse environmental effects.
Preservation of the environment is a political issue. I agree that it's important, but I don't think space is an answer, for reasons mentioned above. It'll happen when the standard of living of all people is high enough that they devote thought to things like empathy with animals and appreciation of nature, and have enough personal comfort that they don't mind making some sacrifices to keep the cute animals and pretty wilderness intact.
People lower down the comfort chain will only care about food, shelter, and making their lot in life less unpleasant.
Hopefully the Chinese will send automated mining equipment which creates other robotic units that use the materials available on the moon to create [...] [...] Provided they can create the robot-factory and manage all the other programming, any country which could play that kind of golf shouldn't have any problem creating a free-form smelter which would use solar power to perform an on-the-fly smelting operation and extract the minerals from their efforts later.
I keep seeing this proposal come up, and it keeps looking funny.
Sending people to live on the moon is an expensive proposition, so I can definitely see heavy automation or even complete remote control from Earth, but building a self-replicating, self-maintaining factory/foundry is really, *really* difficult.
It isn't for lack of applications that we haven't built these already. Think of what could be done if you had even a relatively inefficient self-replicator that could sustain itself from materials it found in its environment - after the initial (and probably large) investment in the first factory, running costs are zero (or rather, are taken out of the factory's ability to do other work, rather than out of the external economy). Build one of these and turn it loose, and you can build as big an industrial base as you want, which can then produce just about any kind of structure or other large-scale project you want, and mine and smelt as much common material as you can sell or use.
The fact that nobody's managed to do this yet strongly suggests that it's non-trivial.
I'm not holding my breath. It'll happen eventually, but we'll have to shrink a self-sustaining industrial complex from the size of a continent's industry to the size of a large factory and replace all of the flesh-and-blood components handling the hard control problems.
So we need a power supply. What do we have on the moon to supply energy? not much. [...] If the moon can't supply itself with enough energy to mine, what's the point?
Not much? On the contrary, we have 1 kW/m^2 of delicious solar energy shining down. Solar panels can be (and are now, for a price) manufactured using thin films of silicon. The moon's crust is largely silicates, and with thin films even a relatively small smelter/purification plant will get you an impressive acreage in solar collectors.
Or just extract aluminum from the crust (which is also plentiful), and build reflectors for a heat engine. With no air, scattering isn't much of a problem. With low gravity, no wind, and no seismic disturbances, large structures aren't much of a problem either. Build as big a heat plant as you want and tap the heat gradient to run your smelter and all the machinery you need for mining.
The moon can most definitely supply itself with enough energy to mine. The only catch is that you either have to stop at night or have enough power storage to run through the 20 or so days of darkness and twilight. Power storage in batteries is a joke (for industrial-scale storage). Power storage in fuel cells would work, but would require vast amounts of hydrogen, which is not abundant on the moon. Power storage using a heat resovoir might work, as you have almost no conduction through materials if you hang the resovoir off cables (no air, remember), but radiative heat transfer will limit the amount of power you can store.
So, unless you want to haul far too much hydrogen or build power cables and thermoelectric plants around a latitude circle, you're stuck shutting down mining for two thirds of the month.
It's still quite useful, though. If you want to build anything in space, the Earth is the last place you'd want to haul material from. Launching from the moon's shallow gravity well is very easy (and with no air, you can use any of a variety of mass driver designs to accelerate cargo electrially for energy cost close to the theoretical minimum).
Lunar mining also lets you build just about anything else you want on the moon itself.
In summary, if you assume you want to build anything substantial orbiting Earth or the moon or on the surface of the moon, the moon is the place to get materials.
Not really. The hazards are about identical- the lithium reactor can still melt down,
While the lithium blanket can certainly melt, this does not in any way resemble the catastrophic runaway reaction that is called "meltdown" in a fission reactor. It's caused by inductive heating from the same currents used to heat the plasma. If anything, your reactor would stall if the blanket melted or boiled off, as you'd be losing more neutrons (as opposed to breeding more tritium from neutrons impacting the blanket).
Re. fission, all tritium breeding from the lithium blanket is far into the sub-critical regime. If a runaway fission cascade in lithium were possible, we'd have bigger problems than unstable fusion reactors to worry about (fission reactors and weapons would be a lot easier to build, for one).
The tritium-tritium reaction is a different beast though; that's potentially pretty clean, and pretty safe
Um, no. It's dirtier than D+D or D+T (more neutrons for the likely reaction paths; you get 4He + 2n in the best case, and you don't just get the best case).
The way they've designed the system, they can produce a total of 1.8 MegaJoule in laser power that all starts from piddly lasers in the nano-joule range.
So, for about $5's worth of electricity and lots of huge slabs of perfect laser glass and crystal, they can more than break even.
To get a 1.8 MJ laser beam, you need to put a minimum of 1.8 MJ into the gain media. The amount of energy in the initiating pulse is irrelevant - it still takes power to amplify it.
In practice, you need to put much more energy than this in. Typical non-semiconductor solid-state lasers have wall-plug efficiencies in the 0.1%-5% range.
Theoretically, NIF will generate about 500 TeraWatts of laser power.
...Over a few picoseconds.
Inertial confinement fusion works by dumping a lot of energy (1.8 MJ, in this case) into the target in a very short time. Of course power figures are huge. They're also not relevant. The real question is, do you get more energy out of the pellet (from fusion) than you dumped in.
So far, inertial confinement fusion is nowhere close to breakeven. The energy from ICF is also a lot harder to capture than from magnetically confined fusion, as in the former you're pretty much stuck with heating an ordinary material and running a heat engine. With MCF, you can at least in principle run the hot plasma into some kind of MHD generation scheme, though in practice the fact that some of your fusion energy ends up in neutron and gamma emission make this less efficient than it could be.
In summary, you have been distracted by the shiny numbers and are't looking at the real characteristics of the machine.
Re:Contamination of Mars et at. with terrestrial l
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New Hope for Life on Mars
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· Score: 2, Informative
I'm sure they will discover life on Mars in the near future - and discover later that they brought it themselves with their space vehicle.
All Mars craft to date have been sterilized to prevent exactly this kind of contamination.
There was a Russian space shuttle. From http://liftoff.msfc.nasa.gov/rsa/buran.html [nasa.gov]:
My point was that it forced the USSR to play catch-up. Much as with the moon race, it was intended to show that the USA would not be dominated by the USSR's early lead in space technology.
It succeeded, at least in the short term. Long-term results are debatable, but it gave another bragging point to the US in the cold war.
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HyperTransport - Don't Athlons already have this? (i.e. it's nothing new)
Not on any chip or motherboard I've seen offered for sale. It was going to be introduced with the Hammer/Opteron chipset.
But the other architectural improvements are going to make x86-64 a must-have for people LONG before the 4GB barrier being shattered will matter to the majority of computer users. Those extra registers will mean an instant performance improvement for everyone as soon as apps are recompiled to take advantage of them. They'll boost throughput quite a bit for video encoding/playback, same for 3D gaming.
3D gaming is primarily limited by your graphics card. Has been for quite some time.
Multimedia already uses the SSE vector register set, and so won't get much of a performance boost.
Add to that the fact that register renaming has been making register count less of an issue for years, and the strength of this benefit looks smaller and smaller.
It'll still _help_, but don't expect a larger register set to give a _vast_ performance boost.
it IS possible to have unlimited users on the same frequency band, but the Throughput for the system will be necessarily reduced
And this is why I distinguished between "data rate" and "bandwidth". HTH.
Except that spread-spectrum transmissions can actually Transmit BELOW the noise-floor, so therefore can also Receive data BELOW the noise floor.
They transmit below the noise floor of narrow-band transmissions with the same data rate. All you're doing is switching from frequency space to code space. The noise floor is still there, it just looks different.
Do all the code division multiplexing you want - detector sensitivity still limits what you can stuff into a given region of the spectrum, with the math described in my original post. Whether you're doing it by having a thousand 1-kHz signals in separate bands or a thousand 1-MHz spread-spectrum signals in the same band is immaterial.
When the world of personal computing was young, and new compression utilities seemed to be coming out every week, every so often you'd hear someone claim that they'd achived the holy grail - written a compression program that could compress its own output, or compress arbitrary files 100x, or perform some other impossibility. Wise people didn't believe them, because information theory strongly limits your ability to compress arbitrary data.
In recent years, we've started hearing similar claims about the spectrum. Remember when impulse-based signal transmission was going to give us limitless bandwidth? This is more of the same.
First, I'll explain the limits to transmission bandwidth. Then, I'll explain how Mr. Lessig is planning to get around them. Finally, I'll explain why it doesn't work.
The spectrum, at the location of any given broadcast transmitter or broadcast receiver, is limited. The bandwidth - range of frequencies - available is fundamentally limited by the receiver's sampling rate (or frequency cutoff, for analog signals). There is no way to get around this, short of using more of the spectrum (by having a higher frequency cutoff). In the past, it was difficult to access even this much, due to the nature of the electronics used (response wasn't perfect, filtering wasn't perfect), but modern electronics are much better (as Mr. Lessig points out in his radio airplane example). The bandwidth limit, however, remains.
The amount of information you can transmit within a given region of the spectrum doesn't depend solely on the bandwidth - it depends on both the bandwidth and the fidelity of your sampling within the band of interest (how many levels you can decode without noise if you're quantizing, or what your signal-to-noise ratio is if you're using a fully analog system or a digital system with very high fidelity). The number of bits of information you can stuff into a spectrum region per second is the log to the base 2 of the number of levels you can reliably distinguish from each other.
This limit applies to any limited-bandwidth signal, regardless of the encoding scheme used. Use spread-spectrum transmission to smear a narrow-band signal over a wider region of the spectrum, and the limit just tells you how many signals you can broadcast this way before the noise floor swamps all signals. The mention of spread-spectrum transmission in the article is a red herring - it doesn't gain you data capacity (it's used for other reasons).
If your system is purely a broadcasting one - sending in all directions, receiving in all directions, no wormholes or relays - this is the best you can do.
You can improve the situation somewhat by trying to beamcast messages instead of broadcasting them. However, this still has problems. Firstly, your "beam" is really a cone. Secondly, your transmitter/receiver is larger, as you need a dish or a carefully shaped antenna or a large array of antennas and some signal processing to get direction-selectivity. Both are caused by diffraction limits related to the wavelengths of the signals being used - a fundamental process that can't be avoided. Thus, while it's used for transmitters (take a look at a cell tower some time), it's not practical for receivers. Either way, you end up with a fixed, finite gain in capacity, as the narrowness of a transmitter's beam can't be made smaller than a certain amount without requiring an extremely large transmitter.
So what about the idea of having short-range transmitters/receivers, and relaying between them? Well, this works to some extent. However, you must have a non-broadcast backbone. Solely relying on the short-range units for signal relaying bogs down very quickly. Consider an area with transceivers uniformly distributed in it, with source and destination points for any given communication chosen at random. Draw a line through the middle of the region. With N transceivers, the number of signals crossing the boundary goes up as O(N), but the number of nodes on the boundary that can do
If you define the universe as everything related to the Big Bang, then we couldn't we conceivably interact with other universes? A part of our universe could already be interacting with a "nearby" universe resulting from another big bang or some previous collision of universes(it's effects would only travel 1ft/ns, light very slow on the cosmic scale, or if you're trying to make fast processors, but that's another discussion.)
You seem to be missing the point of my original statement - there is no larger space in which our universe and other universes exist. "Space" is only defined within our universe.
If you MUD, think of the universe as being an ungodly-huge number of nodes (each of planck radius) connected by links. The fact that any given MUD is finite or has recognizable geometry doesn't mean you'll suddenly have a collision between PernMUSH and KillEverythingMUD.
In summary, there is nothing accessable for our universe to interact with, in the simplest scenario.
If inflationary bubbles are embedded in a larger space, then you just have disjoint regions of the same universe. Inflationary bubbles could collide in this scenario; the results would involve the flow of vast amounts of energy, and the intersection region would probably be moving faster than light (no visible effect, just sudden engulfing).
However, as both inflationary bubbles would be part of the same universe, several components of the physics of each bubble would be the same. How many, no-one's sure.
I personally don't think the embedded-bubble scenario is as plausible, because it postulates more complex behavior for the scalar field (a metastable vacuum state must exist (local minimum) above the global minimum).
A different dimension. Maybe another alternate universe. Our donut may be one of many other donuts. As far as 4th-dimensional creatures like us our concerned, if you could look from 'outside' our universe, everything could look like a big blob within a dark void
As the donut (or sphere or what-have-you) represents space itself, the concept of something "outside" it doesn't really work. Only relationships between different parts of the universe are defined. Treating the universe as the surface of some object is just a trick to make it easier to visualize (otherwise it would just be a set of functions defining relationships between points).
Some of the inflationary models put the universe we can interact with within a larger space, but that just gives us disjoint parts of one larger universe. Much like the event horizon of a black hole, the interface between them would represent a boundary across which interaction and information flow is restricted, and different space/time coordinate systems would be used inside and outside them. (The inflationary bubble looks like an infinite space from the inside and an expanding bubble from the outside; all points on the boundary look like they're at the beginning of time from the inside.)
So, no Voyager-esque bright expanding shell or external vantage point in the simplest scenario, and something a bit different from what you're probably envisioning in the various inflationary models that posit bubbles within larger spaces.
Why do we even assume a simple symmetrical shape? For example, what is to stop universe from being Klein bottle shaped? Or perhaps the universe is a hypersphere, but has dimples like a golf ball. I'm really curious.
If the universe began as a point object (planck-scale sized) and was extremely uniform to begin with, then this uniformity would be reflected in its shape later in life.
OTOH, some of the newer ideas about scalar fields and self-replicating universes would give a contorted, infinitely complex shape on a large scale (imbalances would magnify themselves).
The simplest answer is "because it makes the math easier" (cue mathematician/physicist/engineer jokes...).
no, In Canada, Co-ops are not paid.
In Canada internships are paid...
High school co-op != university co-op. The latter is an internship, for all practical purposes.
At the University of Toronto, it goes for 12-16 months once instead of multiple places in 4-month stints, which has both benefits and drawbacks vs. the Waterloo method (you can work on bigger projects and learn more, but if you get a bad employer, you're stuck with them).
Balogna. The result of burning garbage doesn't necessarily have to be CO2. Plasma burners yield H20 after they are finished processing the H2 and CO that come out.
If you have carbon going in, you have carbon going out.
Burn it in an oxygen-poor environment or play reforming games, and you get the carbon out as tar or particulate carbon instead of CO2 (mostly), but it still comes out.
Plasma burners or other high-temperature incinerators are also *extremely* expensive to run compared to more mundane incinerators. They're used for PCBs and other difficult-to-decompose hazardous wastes, and not much else.
Of course, we've known this for years. Anyone who tells you otherwise is an environmentalist who refuses to accept the facts. The amount of money it costs to take a piece of plastic, paper, glass or whatever and recycle it into another one is more than the cost to create that item from unrecycled material.
The problem is the source of unrecycled material. While we have no shortage of things like metals, and while fossil fuel reserves are large, I know that here in Canada we're converting forests to wood pulp at an alarming rate, and my understanding is that the US has already mostly finished this process and is importing from us.
When the forests run out - easily within my lifetime - we'll either be stuck farming trees for lumber and wood pulp, with a manyfold increase in lumber and paper costs, or have to use recycled paper (paying more than we do now, but less than we would with tree farming as the sole source of supply).
Personally, I'd rather we used steel and concrete for building and recycle paper and keep the forests. But that's just me.
We'd still have to farm trees, as recycling would never be perfectly efficient and some applications (like food wrappings) need to be made from new material, but we'd stand some chance of halting the full-scale deforestation that's going on now.
Lastly, if we think that recycling technology will ever get better in the future, it's best to get people into the habit *now*, so that we aren't stuck trying to retrain the populace down the road.
It's always a race. For example, if we don't come up with a method to crack 2,048 public key encryption, someone else will. You can't assume it could only happen by perfecting a quantum computer; someone could find a way to calculate products of primes quicker. The point is, it's not a matter of if, it's when.
[I'm assuming you're talking about RSA, as you're mentioning products of primes.]
The universe, however, feels no need to bow to human ingenuity. By what reasoning do you conclude that a non-quantum polynomial-time factoring approach exists?
Non-polynomial of *any* speed doesn't help you, if the person making the key was smart enough to add a few extra bits. Exponential problems are nasty that way.
A more intelligent approach is to say that a polynomimal- or near-polynomial time factoring algorithm *might* exist, and try to assess the chance of it a) existing and b) being discovered given an assumed amount of effort for a time window of interest. Remember, the NSA's been working on it for quite some time, with no apparent results yet.
A _wiser_ approach, given the apparent security of the encryption itself, is to look at other vulnerabilities of the system you're trying to protect.
Use the excess power during the day to move mass against the moon's gravitational field and harvest that potential energy during the night.
This would require extremely large amounts of mass for most practical distances. Power to weight ratio is very poor; even very modest temperature elevations store an amount of power comparable to lifting the same mass many kilometres in the air. Carnot efficiency is as good as we want it to be, as space is our heat-sink (though we get better throughput sinking by conduction to ground instead of radiation to space).
The only reason gravitational storage is used at all on Earth is that water is a very convenient and abundant storage medium and nature often provides large resovoirs for us. On the moon, we'd be trucking bricks up a convenient mountain and still be getting lousy power storage.
Leave the Earth, think on Moon! Nobody needs shields there, nor compactness. Reactor can be made without any of the usual safeguards.
Electronics and ionizing radiation do not play well together, unless you plan to build your computers out of vacuum tubes. The reactor housing itself also degrades at a rate proportional to the amount of radiation it receives.
Lastly, the plumbing, turbines, and radiators for a high-power closed-loop plant will weigh far more than the shielding. You only get a tiny high-power plant if your working fluid is free and all you're trying to do is heat it up (c.f. NERVA and the nuclear aircraft experiments).
Well, it depends if you want thermal energy, or electrical energy. If it's mostly thermal and some mechanical, a nuke is very efficient and you can fit it in 4 tons or less, shielding and all.
You need electrical if you want to have closed-loop smelting, as at some point you have to electrolyze either the ore itself (in the case of aluminum) or some derivative of the material you're smelting with (e.g. Fe2O3 + C -> Fe + CO2, CO2 + H2 -> H2O + CH4, CH4 + O2 + shennanigans -> H2O + mostly C, H2O + electricity -> H2 and O2 to repeat the process).
I also strongly suspect that the amount of heat needed by heat-driven industry is beyond that available from a reactor it's practical to lift. If the moon is to produce a useful amount of material for space projects, final power requirements would be gigawatts at minimum.
A smaller plant might jump-start the smelting, but packing a lot of thin-film cells on mylar instead would probably give comparable or better power density during the day and cause far fewer hassles getting approval for the mission.
But, and this is a very important but, since all humans live on one planet right now we are playing for all the marbles. I'd rather not take any chance that can be eleminated. If we had self-sufficient colonies elsewhere I wouldn't worry about something unlikely to happen, but we don't.
Sure, I'll agree with this, but it doesn't have relation to the "we should move all industry to space" argument. Space colonization will happen as an inevitability - all it requires is a small group scraping together the minimum resources required, and the barrier to entry is (slowly) going down. Moving industry to space is an entirely different matter.
Re: Resources. At this point I think you are a bit like a person in the early 20th century telling me that automobiles are pointless because we will always have enough horses. It is certainly true that we have resources not yet exploited However these resources are inherently limited. Large yes, but infinate no.
Sufficiently close to infinite for all practical purposes. Energy dumped into the climate engine is on the order of 1e16 to 1e17 watts. Terrestrial power consumption is about 1e13 watts. If we want to go nuclear, crust abundance of thorium is about 6 ppm by weight. This gives about 3e11 tonnes in accessible regions of the Earth's crust. Assuming 1 MeV per particle potential energy and a capture efficiency of 10%, we have about 1.3e15 moles, or 8e38 particles, or 8e43 eV, or about 1.6e25 joules - enough for about 50,000 years. Even dividing this by the fraction of accessible thorium that's easily extracted, we have plenty of time to build up our solar heat engines or invest in future technologies like fusion.
As for materials, the crustal abundance of just about *anything* gives more than we could ever need within easy reach. The earth could be populated at standing-room-only and we'd *still* be limited by energy and not matter.
It is absolutely true that at the moment it is cheaper to build on Earth. In the early 20th century it was cheaper to use horses, yet you may have noticed that we use cars today. Technology will improve, that's a given.
Technology is limited by physics, and physics decrees that we're stuck in a 60 MJ/kg potential well. Even with a space elevator with a magical transport system capable of arbitrary volume, it would cost a non-trivial amount to lift material out of the gravity well (low, but non-trivial; think of it as an export tarrif, and you're in the right ballpark). In practice, I'm skeptical of ground to orbit costs ever being anywhere close to the theoretical minimum - the rate of cargo transfer along a space tether is sharply limited, and the tether has to amortize its construction and maintenance costs over its maintenance lifetime. Moving things down along a tether and from other orbits to the top of the tether in the first place will cost more than zero, which gives an added cost that ground-based industry doesn't have (both still need ground transport, so the tether has no advantage there either). I do not believe that it's intrinsically cheaper to produce any material object in space than on Earth, so there's no savings to offset this added cost.
As for energy, you have transport losses, and you have the the microwave beam problem unless you have a power cable running along the elevator, and you have the cost of maintaining a huge structure if you're generating based on solar power. On Earth, you can let the climate engine concentrate solar power for you.
In summary, I don't see how space-based industry or power generation will have an advantage at *any* level of technology, if the market is on Earth.
As for room, most of the real-estate you mention is undesireable in the extreme. Additionally, we require more than living space. We need space for farms and ranches to grow our food. We need space for factories to build our computers. We need space for...
Re-read my message. And then dig out that atlas I suggested - one which has maps of land use. Industry and population centres take up almost no area - human sprawl is almost all farmland. This will never, ever be moved to space, because it's easier to build a giant farm-factory on Earth than it is to lift one into orbit and bring the produce back down, if space becomes a limitation.
If we need more space, it will be for farmland, not anything else.
Fossil fuels are inherently limited, no arguing that there are oil fields yet untapped, but eventually we will run out.
The climate engine will run out when the sun burns out, at which point we will have bigger problems than a lack of electricity. Fossil fuels will be used until scarcity and/or cost of clean-up makes alternatives like nuclear and widespread hydroelectric or solar heat-engine generation cheaper. Running out will be a gradual process of increasing cost of extraction, not a cliff.
Again, at the moment, building an orbital power collector is prohibitively expensive. But the moment will pass.
This is a perfect example of the assumption you're making that I just don't get. Why is it cheaper to build a big solar collector in space than it is to build the same solar collector on Earth? Or to build a power station that uses the land, air, and sea to do the collection for you? Any scenario that brings construction cost down in space is likely to bring it down on Earth too (ultra-tensile cable materials let you build much thinner panels or reflectors on Earth, for instance).
You seem fixated on a space-based solution without looking at any of the alternatives.
The moon's crust is largely silicates, and with thin films even a relatively small smelter/purification plant will get you an impressive acreage in solar collectors.
Plenty of silicon dioxide, not much hydrogen or carbon. Hardly any, in fact, and you kinda need them to manufacture solar cells.
How so?
You'll certainly use many chemicals in the smelting, but the final product is nearly-pure silicon on an arbitrary substrate (glass works fine). Chemicals used in smelting will be recycled in as close to a closed-loop scheme as possible, because they have to be imported from Earth.
The cells themselves contain silicon with trace amounts of phosphorus and arsenic for dopants, and aluminum for wiring. Not a lot of hydrogen or carbon there.
Manufacturing aluminium takes a lot of energy, 20 kWh for a single kilo. Where are you going to get all that power, since you can't manufacture solar cells?
From solar cells, which we _can_ manufacture, or from the partially-built heat engine, or from the smaller power source of whatever type that powers the initial smelter.
Remember, one (1) square metre of lunar surface can smelt a kilo per Earth day by your calculations. Even with 5% efficient power generation, the collector area required is about the size of your living room. One kilo of aluminum gives at least one square metre of mirror area, or can coat a much larger area of glass mirror. Growth rate is fast.
You'd be better off importing a submarine-style nuclear reactor from Earth.
Nope. The power to weight ratio is too lousy to run your entire industry off of this or any other power source transported from Earth. You'd probably send a few RTEGs to run control electronics during lunar night, but that's about it.
The lunar day is 24 hours, 50 minutes.
This "lunar day" is not the length of a day on the moon. It is the interval between the moon occupying the same position in the sky on successive days for an observer on Earth (one Earth day, plus adjustment for the moon moving along its orbit).
The moon is tidally locked to Earth, and rotates once per orbit (about 28 Earth days).
One of the things we can get from space that does not occur naturaly on Earth is Iridium. We know that it has myriad uses, but we simply don't have much of it because it is not native to Earth.
Sure it's native to Earth. It's just about as rare as the other metals in the same region of the periodic table (little things like platium, palladium, and so forth).
We don't have enough to mass-produce things out of it (just like you're not likely to build a kitchen table out of platinum for every family on your continent), but we've had ample opportunity to _research _ it.
You're probably thinking about the K-T boundary thing from geology. What they found was a layer _rich_ in iridium, and containing specific isotope ratios that were not associated with terrestrial deposits. Asteroids are most definitely not the *only* source.
On a more pragmatic note some industry MUST be located off planet for safety reasons. Research into nano-scale assemblers is an excellent idea -- as long as a mistake can't turn the planet into grey goo. Orbital facilities seem ideally suited for this.
Life has had billions of years to spend working on improvements to self-replicators, and has not yet produced "grey goo". I am not convinced that it's possible to produce self-replicators much more efficient than the ones that already exist (if it was possible, why haven't they formed and outstripped the existing ones?).
Even if you assume a drastically improved self-replicator is possible, it still has to get its energy from somewhere. Even sucking up all available solar and checmical energy from a local area gives a strongly limited growth rate. You'd get something closer to grey mould than the all-devouring goo scenario. Not only do you have to put in the initial energy to convert material from stably-bound checmical forms to something you can use, but you have to keep putting in energy to maintain your highly-ordered, higher-energy constructs against natural decay (you can smelt rust into iron, but it doesn't take long to start turning into rust again).
In summary, I don't think grey goo is a risk we have to worry much about.
Finally, there aren't many other games in town. Terrestrial industry is already facing large problems of overcrowding, pollution, and energy shortage. If we limit ourselves to terrestrial industry it is literally impossible to build a car for every person in China due to a lack of energy and raw materials.
We appear to be operating in different universes. Given enough time, China can produce any amount of cars. Given sufficient industry, it can build those cars quickly enough to finish building them before the first cars stop running them. Whether it currently has the required industry is immaterial - it can build it.
We have vast deposits of fossil fuels in the ground and under the ocean. We have enough easily accessible uranium in the world to power a first-world civilization for centuries. We have enough thorium and other materials to breed new nuclear fuel for thousands of years.
We have a giant fusion plant in the sky that won't burn out for several _billion_ years. Large-scale solar production via heat plant is practical; it's just more expensive than current production methods, so it isn't done. We already tap it indirectly in the form of the climate engine; hydroelectric power stems from this source and is widely used (let the oceans be our solar panels and the rains our cabling). Energy won't be a problem - and this is just using existing, well-proven technology.
In summary, I see no shortage of either power or industrial capacity on Earth.
Space allows us to generate huge amounts of power, has raw materials that are accessable without harming any environment, etc.
We simply don't have the room here on Earth for enough industry to provide first-world luxury for all humans
Now I know we're operating in different realities.
What makes you think a space-based solar generator will be more economical to build than a ground- or ocean-based one? What makes you think bombarding the earth with material from the moon won't have an environmental impact? (Remember the last couple of big volcanic eruptions? Dust matters.) What makes you think that giant microwave beams dumping heat comparable to the entire power production of earth cause less environmental harm than hydroelectric dams or fission plants? What makes you think it's economical to mine material on the moon or from asteroids at all, if the target market is terrestrial?
Materials and power from space are only easily accessible to other things in space. Planets are *huge* treasure-troves of material and power - the only reason we wouldn't *export* to space is that our gravity well makes material transport expensive.
As for room... Take a look at an atlas some time. Most of the space used by humans is farmland. You're not moving that to space. If you were at the point where you were considering it, you'd instead just build in-building farms on Earth - it would be similarly expensive, and shipping would be easier. In practice, we'll just move our consumption down the food chain and find a way to make algae and bacteria cultures taste good.
Space taken up by industry and population are negligeable by comparison.
The exception is the lumber industry. When natural forests are used up, or are preserved by law, forestry will finally shift to being a conventional farming industry, and the price of lumber will change appropriately. Materials use will shift a bit towards metal and concrete in response.
As for the fundamental resources available... We're sitting on a big ball of aluminosilicates. We have enough material for *anything*.
In summary, there is no shortage of power or materials on earth, and per-capita industrial production can be adapted at will by building up industry. In most cases, moving production of anything to space will cost _more_ and have worse environmental effects.
Preservation of the environment is a political issue. I agree that it's important, but I don't think space is an answer, for reasons mentioned above. It'll happen when the standard of living of all people is high enough that they devote thought to things like empathy with animals and appreciation of nature, and have enough personal comfort that they don't mind making some sacrifices to keep the cute animals and pretty wilderness intact.
People lower down the comfort chain will only care about food, shelter, and making their lot in life less unpleasant.
Hopefully the Chinese will send automated mining equipment which creates other robotic units that use the materials available on the moon to create [...]
[...]
Provided they can create the robot-factory and manage all the other programming, any country which could play that kind of golf shouldn't have any problem creating a free-form smelter which would use solar power to perform an on-the-fly smelting operation and extract the minerals from their efforts later.
I keep seeing this proposal come up, and it keeps looking funny.
Sending people to live on the moon is an expensive proposition, so I can definitely see heavy automation or even complete remote control from Earth, but building a self-replicating, self-maintaining factory/foundry is really, *really* difficult.
It isn't for lack of applications that we haven't built these already. Think of what could be done if you had even a relatively inefficient self-replicator that could sustain itself from materials it found in its environment - after the initial (and probably large) investment in the first factory, running costs are zero (or rather, are taken out of the factory's ability to do other work, rather than out of the external economy). Build one of these and turn it loose, and you can build as big an industrial base as you want, which can then produce just about any kind of structure or other large-scale project you want, and mine and smelt as much common material as you can sell or use.
The fact that nobody's managed to do this yet strongly suggests that it's non-trivial.
I'm not holding my breath. It'll happen eventually, but we'll have to shrink a self-sustaining industrial complex from the size of a continent's industry to the size of a large factory and replace all of the flesh-and-blood components handling the hard control problems.
So we need a power supply. What do we have on the moon to supply energy? not much.
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If the moon can't supply itself with enough energy to mine, what's the point?
Not much? On the contrary, we have 1 kW/m^2 of delicious solar energy shining down. Solar panels can be (and are now, for a price) manufactured using thin films of silicon. The moon's crust is largely silicates, and with thin films even a relatively small smelter/purification plant will get you an impressive acreage in solar collectors.
Or just extract aluminum from the crust (which is also plentiful), and build reflectors for a heat engine. With no air, scattering isn't much of a problem. With low gravity, no wind, and no seismic disturbances, large structures aren't much of a problem either. Build as big a heat plant as you want and tap the heat gradient to run your smelter and all the machinery you need for mining.
The moon can most definitely supply itself with enough energy to mine. The only catch is that you either have to stop at night or have enough power storage to run through the 20 or so days of darkness and twilight. Power storage in batteries is a joke (for industrial-scale storage). Power storage in fuel cells would work, but would require vast amounts of hydrogen, which is not abundant on the moon. Power storage using a heat resovoir might work, as you have almost no conduction through materials if you hang the resovoir off cables (no air, remember), but radiative heat transfer will limit the amount of power you can store.
So, unless you want to haul far too much hydrogen or build power cables and thermoelectric plants around a latitude circle, you're stuck shutting down mining for two thirds of the month.
It's still quite useful, though. If you want to build anything in space, the Earth is the last place you'd want to haul material from. Launching from the moon's shallow gravity well is very easy (and with no air, you can use any of a variety of mass driver designs to accelerate cargo electrially for energy cost close to the theoretical minimum).
Lunar mining also lets you build just about anything else you want on the moon itself.
In summary, if you assume you want to build anything substantial orbiting Earth or the moon or on the surface of the moon, the moon is the place to get materials.
Not really. The hazards are about identical- the lithium reactor can still melt down,
While the lithium blanket can certainly melt, this does not in any way resemble the catastrophic runaway reaction that is called "meltdown" in a fission reactor. It's caused by inductive heating from the same currents used to heat the plasma. If anything, your reactor would stall if the blanket melted or boiled off, as you'd be losing more neutrons (as opposed to breeding more tritium from neutrons impacting the blanket).
Re. fission, all tritium breeding from the lithium blanket is far into the sub-critical regime. If a runaway fission cascade in lithium were possible, we'd have bigger problems than unstable fusion reactors to worry about (fission reactors and weapons would be a lot easier to build, for one).
The tritium-tritium reaction is a different beast though; that's potentially pretty clean, and pretty safe
Um, no. It's dirtier than D+D or D+T (more neutrons for the likely reaction paths; you get 4He + 2n in the best case, and you don't just get the best case).
The way they've designed the system, they can produce a total of 1.8 MegaJoule in laser power that all starts from piddly lasers in the nano-joule range.
...Over a few picoseconds.
So, for about $5's worth of electricity and lots of huge slabs of perfect laser glass and crystal, they can more than break even.
To get a 1.8 MJ laser beam, you need to put a minimum of 1.8 MJ into the gain media. The amount of energy in the initiating pulse is irrelevant - it still takes power to amplify it.
In practice, you need to put much more energy than this in. Typical non-semiconductor solid-state lasers have wall-plug efficiencies in the 0.1%-5% range.
Theoretically, NIF will generate about 500 TeraWatts of laser power.
Inertial confinement fusion works by dumping a lot of energy (1.8 MJ, in this case) into the target in a very short time. Of course power figures are huge. They're also not relevant. The real question is, do you get more energy out of the pellet (from fusion) than you dumped in.
So far, inertial confinement fusion is nowhere close to breakeven. The energy from ICF is also a lot harder to capture than from magnetically confined fusion, as in the former you're pretty much stuck with heating an ordinary material and running a heat engine. With MCF, you can at least in principle run the hot plasma into some kind of MHD generation scheme, though in practice the fact that some of your fusion energy ends up in neutron and gamma emission make this less efficient than it could be.
In summary, you have been distracted by the shiny numbers and are't looking at the real characteristics of the machine.
I'm sure they will discover life on Mars in the near future - and discover later that they brought it themselves with their space vehicle.
All Mars craft to date have been sterilized to prevent exactly this kind of contamination.
It showed technological superiority over the USSR
There was a Russian space shuttle. From http://liftoff.msfc.nasa.gov/rsa/buran.html [nasa.gov]:
My point was that it forced the USSR to play catch-up. Much as with the moon race, it was intended to show that the USA would not be dominated by the USSR's early lead in space technology.
It succeeded, at least in the short term. Long-term results are debatable, but it gave another bragging point to the US in the cold war.