I don't get this. Maybe I'm missing something obvious.
Why would the moon have a significantly greater meteoroid flux than low earth orbit? Yes gravity bends trajectories inward, but the difference in gravitational force at 150 miles versus on the surface is less than 10% on earth, which has a much stronger field to begin with.
In fact, I'm inclined to think the danger in low earth orbit is higher. In addition to yanking more objects in close, the increased gravity means they're moving faster and thus can do more damage. Plus there's space junk, both charted and uncharted.
So solar activity is a logical concern, but I think people are getting overly hyped about the meteor impacts, perhaps because of the recent study finding rates of noticeable impacts are 3-4 times what they were previously thought to be.
The one difference I do see is that in LEO, a miss is as good as a mile, while on the moon, you get "splash damage."
In addition to the obvious fact that we already have built an orbiting habitat, reading NASA's lunar architecture study report makes some advantages of a lunar habitat obvious. Of course, statements like, "With an orbital platform, materials that make it out of the Earth's gravitational pull are right where they need to be," show the author doesn't really know what he's talking about. There's also long-standing fallacy that an LEO stopoff at a space station is inherently better for exploration, and the irrelevancy of comments about mining Helium-3 when we haven't even mastered D-T fusion yet.
For those not familiar with the study, it basically looked at a variety of approaches for returning to the moon, based on the capabilities of the Orion capsule, Ares launch systems, and Lunar Surface Access Module designs and recommended the best one.
The conclusion they reached was that the most sustainable approach was to start by landing several missions in the same location in a nearly permanantly lit region near one of the poles (avoids the problematic 14-day night). Each mission would be brief, but leave behind equipment that could be used by the next. The somewhat modular concept for the LSAM (likened to a lunar pickup truck) means it could easily bring different payloads down on each mission. After 5 missions, there would be enough equipment to support extended visits, and begin research into In-Situ Resource Utilization and other long term experiments; things you flat out can not do on the ISS.
The beauty of an outpost with the capability to be permanently manned on the moon is threefold:
1.) It doesn't need to be constantly manned, or even constantly maintained. Unlike the ISS, which at the least needs periodic orbital boosts and constant power to it's orientation control gyros, you can simply "winterize" a lunar outpost and leave it for a while. If you have budget constraints or some other program setback and have to abandon it for a time, it just sits there waiting for you to come back. The ISS deals with gravity just as a lunar outpost would, but the lunar outpost actually turns it into an asset.
2.) It enables long term investigation of a piece of lunar soil, and does not interfere with exploring other parts. NASA recognizes that the LRO may find other interesting sites on the moon to send manned missions to, and the proposed architecture still supports that. At the same time, they can get an in depth look at lunar geology and practice techniques that will hopefully be used in a Mars mission.
3.) It provides a wide range of options for contributions. A criticism of the ISS is that it has been constantly hamstringed as nations, including the US, have been slow to contribute pieces...all while it continues consuming resources. The US would develop the launchers capable of putting large payloads on the surface and create an infrastructure that can support a human presence, then welcome contributions from partner nations in the form of equipment, experiments, and astronauts above and beyond the basic goals as they see fit to contribute. Among the many possible contributions NASA has identified are ISRU experiments, alternate power sources, astronomy equipment (a radio telescope would have find effectively unprecedented low level of noise), and a pressurized rover for long distance EVA's.
Of course, the author did get right the concerns over the fact that the moon is much harder to get to than the ISS, and there are more things that can go wrong getting there and back, but so many more of his criticisms are off base. Even the concern about meteoroids strikes me as wrong. I can think of no reason why the moon should encounter a greater meteoroid flux than the earth (a noted threat to the ISS), and in fact, might even be safer for the lack of space junk.
The US has built two space stations. The Russians have built three, counting their ISS contributions. Private industry is even getting in on the game (Bigelow). Honestly, how long should we wait before re-extending our presence to the moon? How much more does low-earth orbit really stand to contribute to our understanding of how to go places in our solar system?
Actually, I think a better question would be why use air?
Air has oxygen and water vapor in it, both of which react with a wide variety of materials in the right conditions. Water also condenses (obviously) well above the temperature on Titan, and oxygen boils right around the surface temperature at the ambient pressure. Condensed fluids are useless dead weight, and at the cost per pound of an interplanetary probe, dead weight is not cool. Realistically, NASA would probably choose a non-reactive, pure gas like helium or nitrogen specifically for this reason. Nitrogen has a nice feature in that the Titan atmosphere is 98% N2 (only 1.6% CH4, actually), so the difference in partial pressure inside and outside the envelope is almost neglible, and it won't leak very fast at all.
Any heat generated inside the envelope would decrease the density of a given volume and pressure, so you can achieve some buoyancy. Nitrogen or air, the latter being a worse case, are already at or above the density of Titan atmosphere, so they would need to stay significantly warmer than the outside environment to produce significant lift. The warmer it is, the faster it loses heat, meaning it needs either more insulation than just a pressure envelope, or a bigger reactor to supply more heat. Either means more weight which means more lift needed. All this time you're also increasing the launch weight from Earth. Just warming it to get more lift is a catch 22 of sorts.
So you come out far ahead if you can contain hydrogen or helium, which have 1/14 to 1/7* the density respectively at a given T and P. Because of the greater lifting effectiveness, you don't need as large of an envelope which means lower launch mass. Of course, these gasses could still certainly benefit to a degree with the power supply contained inside the envelope, and you could probably save even a tiny bit more mass in that scheme...or add more scientific payload.
The downside is that hydrogen and helium are non-polar particles with extremely small radii, so they have a serious tendency to leak out of their containers. Thus the envelope may have to be thicker to effectively contain them, which is another weight tradeoff. I couldn't make a firm conclusion off the bat, but I'd be willing to bet that helium or hydrogen still come out clearly on top.
* Diatomic hydrogen has a molecular mass 1/14 that of diatomic nitrogen. Helium may have an atomic weight 4 times as much as hydrogen, but it is mono-atomic in it's natural state, so the density is only twice that of hydrogen gas.
There's this theory that the power level is less important than the frequency.
This is true. That's why you worry about X-rays and not hues of green. However, it's definitely not as simple as frequency, either. I'm almost positive (I should google it, but I'm too lazy) there have been studies showing cancers develop in cells in a petri dish exposed to cell phone frequencies and power levels, but obviously those don't directly translate to cancer in people.
Various frequencies are absorbed preferentially by various materials. X-rays tend to pass straight through body tissue. At the opposite end of the spectrum, VLF does, too. The microwave frequencies used by cell phones are (I'm told) almost entirely absorbed by the outermost layers of skin, which are dead and thus can not develop cancer. Levels deep inside the body are so low that the odds of a codon flop should be almost infinitessimal.
This points to, but admittedly does not prove, the conclusion that cell phones are safe. My take on it is if the people who carry theirs on them 24/7 and talk for an hour or more a day don't show a clear correlation, I'm not going to worry about it when I carry mine less than a quarter of the day and talk an average of 2-3 minutes.
Charge: 0
Mass: between 10^-6 and 10^-2 eV/c^2
Spin: 1/2???
Not knowing is killing me. Do we not know the spin, or did it just for some reason get left out of both the physorg article and the wikipedia article? The Wikipedia article does say something about a fermionic superpartner called the axino, from which I would infer the axion is a fermion and axino a boson, but it doesn't explicitly say.
I find your comment very insightful, but I have slightly different thoughts on a few minor points.
While I do personally believe exactly the sort of subtle influence you mention is occurring in the various fields of acedemia, I also do believe deliberate political actions are being taken to selectively choose or suppress scientific research on both sides of the table. However, these must be limited, or it would become much more obvious. Therefore, I suspect the BBC will find some isolated incidents of rejected grants, lost data, etc. For example, we've already seen the incident in NASA where some mid-level managers marginalized Dr. Hansen's research that was indicative of global warming. I suspect cases in the opposite direction will appear, too.
I think there's more to the subtle elements of bias you mention, too. There is not only the confusion of researchers with a wide array of expertise contributing conflicting data from their perspectives, there's also the possibility of scientists defining themselves into a finding. For example, if a scientist accepts a grant to characterize the effect of ozone depletion on climate models, they may get so focused on determining the scale of the effect that they misinterpret the data or the model as showing an effect when there actually is none. I can think of several instances from my own engineering experience where I've done this and later discovered the error when the applied solution did fix the problem. It's a matter of finding exactly what you expect, instead of what's really there, like Columbus "exploring" the East Indies when in fact he was in San Salvador.
Also, I wanted to add a comment about that assumed 7 temperature increase by 2100. Most reports on climate modeling I've seen show effects ranging from no change to a increase of 4-5 on the extreme end. I believe the most widely accepted models predict a 1 rise. The exaggeration is worse than you suspect. And perhaps I'm missing something, but doesn't 7 polar bear populations declining or unknown leave 13 populations stable or growing?
Lastly, I like your example illustrating assumptions about cause, but I wanted to add that referring to Al Gore in global warming discussions is like referring to Sen. Ted "the tube" Stevens in internet discussions.
This is like requiring shoppers at Walmart to pay a fee for stolen merchandise. That's only going to encourage further theft (gee, I already paid for it...it's not like I'm getting a five finger discount), and it's ridiculous from the start.
Wow, I had no idea that Microsoft cut that shady deal. Now the Universal seems to have quite literally declared they should have a right to both have their cake and eat it, too. They want you to both pay for the music and pay for not paying for it.
I don't own a media player, but now I know that if I ever get one, it won't be a Zune.
Mods, show the parent some love. I thought this was so obvious it hurt, but halfway through the discussion, this is the first time I've seen this comment:
The issue isn't a general decline in craftsmanship; its a decline in the willingness of people to pay a premium for well crafted items. I don't remember exactly, but I think I paid between £40-50 for mine, which in 2006 dollars would be aroun $150. Naturally, I expect a $150 umbrella to last longer than one I bought from a street hawker for $10 during a rain squall.
The submitted article is also an apples and oranges comparision. Tell me sir, does your IBM XT fit in your pocket, operate for days at a time without external power, and make phone calls? Also, is your 20 year old desktop a clamshell design, has it been repeatedly dropped while you try to take drunk pictures of your friends with it, and how many total hours of use does it have compared to your phone? Perhaps a better comparison then would be your shiny new smart razor versus a circa 1995 flip phone. Not that I don't expect a somewhat similar results from that comparison, because of the point the parent made.
If durability is important to you, it has to be one of your criteria when you're shopping. It doesn't just happen. It's the same old engineering adage: Cheap, strong, capable - Pick two.
Manufacturer's generally do still make durable products if you're willing to pay a little bit more or lose some features. A clamshell presents an obvious failure point. If you want lightweight or slim, you can bet there's going to some tradeoffs in body design. If durability is really high on your list, you'd better be reading reviews or looking for items that are designed with durability in mind, like Nextel's military-spec'd phones.
Tune in next week for our kitchen special: Why do Plastic Sporks Break? - A comparison of picnic flatware to cast iron frying pans.
You need an artificial heat source in the laptop, and the cold sink is the outside environment. As mentioned in the article, the heat source would most likely be a very small burner operating at a few hundred degrees. The high temperature seems to concern a lot of people, especially those who had their sony batteries explode on them, but it is technically feasible.
However, laptops get hot enough just from their chips operating and batteries discharging at 80% or so efficiency. Trade the battery for a thermal-electic chip operating at 20% efficiency and you'll find yourself with a lot more heat to dissipate.
Since I'm not intimately familiar with their principles of operation, I'm curious how this is different from a Seeback (reverse Peltier) device. Googling around a little bit, it seems most Seeback devices achieve around 5-10% efficiency, while the article claims up to 20% efficiency, so it seems they may be slightly different physical effects. Anybody care to enlighten us?
True to some extent, but not in the practical sense. None of the old fusion power timeline estimates (most were more or less guesses, actually) really reflected the difficulty and complexity of sustaining a burning plasma. There seems to have been a natural tendency to think it was only one step up in difficulty from sustaining a fission chain reaction. In reality, that is far from a trivial challenge. In the last 25 years, researchers have invested a lot of effort learning how to heat the plasma, deliver fuel, deal with heat and neutron bombardment, and confine the plasma so it doesn't fizzle out.
ITER will finally take all these lessons and apply them to create the first truly sustained (or "burning"...ie (Q - losses) > 1) fusion reaction. From there the crew will still have to learn how to operate it on a continuous basis, applying all of the above challenges to long term experiments, and if all goes according to plan, provide a testbed for integrating a Tokamak core into a functioning powerplant.
In light of all this, I'm skeptical that fusion power prospects could have reallistically gotten more than 10 years ahead of where they are today even with more abundant funding (and according to the current ITER project timeline, the reactor will achieve first plasma late in 2016, so that's where we might be today). Of course, it doesn't help that a disappointing portion of the ITER news over the last 10 years has been the debate over whether to build it in Japan or France.
The lack of motivation still frustrates me though. The $12 billion cost of ITER is roughly the value that the US produces in raw coal every 4 months, yet we backed out of our 10% committment in 1999 until jumping back on the wagon in 2003. Throwing money at the challenges won't make them go away, but it could sure expedite solving some of them. I can only hope that once ITER starts operating (assuming no insurmountable challenges are then found), people will really see the potential of the Tokamak design and waste no time converting what we know into the design of the first generation of fusion power plants.
What if the entry plan for the Mars Climate Observer had been reviewed publicly? Don't you think there's a chance someone would have noticed the metric conversion issue and saved the project?
Honestly...no. Have you ever tried to calculate an interplanetary trajectory? It's not a 1 page exercise. It's big, calculus heavy project with a lot of parameters (masses, forces, velocities, previous actions, and even dates are all important) that involves a lot of number crunching. There's a reason that it took 11 years and 15 missions from the first attempted Mars mission in 1960 until the first successful orbit of Mars. Heck, in 1965, just hitting Mars like the climate orbiter did would've been considered a huge success.
Actually spotting a mismatch of units like that in the volumes of derived equations (where the problem actually lay), documentation, computer source code, and part specifications as someone not intimately familiar with the project would be ridiculously lucky. While there's no denying that NASA made a preventable mistake, it's hardly as obvious as it sounds.
I considered submitting the same space.com article, but you beat me to it. I think you should've focused much more in your summary on the response to the accusations (particularly the fact that the current design estimates have the Orion 10-15% lighter than the max allowed, and that the max allowed is something like 15% less than what the Ares 1 can orbit.
Really the original article could be much better summed up as "NASA engineer lays the smackdown on ignorant armchair critics" than "Constellation Battles the Blogosphere."
Frankly though, unsubstantiated claims ("I heard it from a friend at Lockheed" is not a verifiable source) on a blog (not exactly reputable either) shouldn't be worthy of a response. Apparently this guy finally touched a nerve with an engineering manager over at NASA.
Your points are true, and in fact all measurements are at some level just approximations (eg: you read a ruler measurement as 6 inches, when it is actually 6.13 inches, or you calculate a trip time based on as-the-crow-flies distance instead of road distance).
So yes, assuming the underlying theories are correct, this could be a good measurement. We don't for certain know that general relativity and quantum mechanics are correct, but currently there is almost no scientific dissent on their validity. Those theories are probably the most relevant to your point, and from my limited knowledge, I haven't been able to poke any major holes in their method. If those theories are wrong, mistaking the spin rates of these black holes is definitely one of the more trivial implications.
Of course, now that they've published their paper, their work is pretty open to criticism from some people much more intimately knowledgable about the subject. Their work has implications for several other research projects, such as LIGO, so I suspect quite a few people will be reviewing it with interest.
That is true. However, this is currently our best estimate, and the theory applied is pretty well-respected. It may be interesting to know that this finding supports a 1997 suggestion that this particular black hole spins very close to its maximum. The 1997 paper attempted to explain in theory the x-ray jets this black hole emits by suggesting it spins. In contrast, this new paper actually documents an attempt to measure the spin.
Anyway, assuming the theory is correct, their method sounds pretty plausible to me (also assuming I'm understanding the paper and article right).
Basically, the size of a black hole event horizon depends mainly on its mass. However, if the black hole is spinning (most or all are believed to due to conservation of momentum), the event horizon contracts due to frame dragging.
Of course, we can't directly see the event horizon to measure it like we can measure the sun's radius. These black holes are far too distant to resolve. But, matter falling into the black hole is heated up due to friction. Just before it passes the event horizon, it gets so hot it emits x-rays that are detectable from earth.
The clever part is that the energy of the x-rays is correlated to the emitting particle's radius from the center of the black hole, since as particles spiral in further, they heat up more and more. So if you know the mass and can measure the highest frequency of the emissions, you can calculate the rate of spin. Of course, finding the mass and measuring those x-rays is not at all trivial, and the final step of calculating the spin probably took the 6 researchers who published the paper a year or so worth of work.
It sounds theoretically feasible, but technically a nightmare. If a meteor knocked a hole in your bag (pretty likely over time), you would suddenly have a second jet, and you didn't get to pick which way it's pointed, so it's effectively uncontrolled. It might hit the earth instead of orbiting. If it broke apart due to the warming, your bag is completely history.
Plus, when was the last time somebody wrapped something that big? It would probably take hundreds of thousands of pounds of plastic, plus some sort of machine that to lay it all down. And you'd need nozzles. If you want to control it, you can't just cut a hole and call it good. And you have to the center of mass precisely, which would change as material is jettisoned, or it tumbles.
Also, you're talking about a lot of momentum change here, from a low impulse thruster. Comets move fast through the inner solar system. It would take a lot of mass and a long time to swing it into a useful orbit.
Probably a better idea is to land a couple solar or nuclear powered mass drivers on the comet that would actively launch material in the opposite direction you wanted to accellerate the main mass. It's still a major leap beyond what we can technically and economically accomplish right now...except perhaps if we found ourselves absolutely needing to and we had enough time.
All astronauts are given a budget for allowable total exposure to radiation (I'm not sure if it's broken down by approximate wavelength or not) over their lifetimes, and also for rate of exposure over shorter time periods. These are correlated to estimated increased risk of developing cancer over their life. For example, an astronaut is allowed something like 6 months of contiguous duty on the ISS and up to 1.5 years over their life. I'm not sure if those are the actual numbers, but they're in the ballpark.
Being much less protected on the moon, the times are shorter. Obviously, shielding would affect the numbers. So if you spent most of your time a few meters underground, you could stay longer.
Not offtopic, but shows misperceptions
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The Web Is 16 Today
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· Score: 4, Insightful
Then why have I been online since 1987?
People really should try to be more clear what they are talking about. The story submission isn't, and "internet" and "world wide web" are somewhat ambiguous terms.
Most of us know that distributed networking goes back to the 60's or so, with ARPAnet. In fact, according to wikipedia (I feel a slight tinge of irony looking these details up), our beloved TCP/IP began taking shape in the early 70's and ARPAnet began using TCP/IP in 1983. Meanwhile, services like Compuserve began offering private dial-up networks, and augmented them with email in 1979. Usenet popped up at the same time. The BBS's started popping up in short succession.
So all this was in place by 1990 when Tim coined the term world wide web and created the first browser, but it is the experience of browsing inter(hyper)linked files that defines most people's understanding of the internet. I suppose it's fitting to consider the start of this, if any one event, as the birth of the world wide web.
I'd really like to see a more general timeline, showing the major steps forward from the first electronic computers, first networked computers, ARPAnet, Compuserve et al, TCP/IP, DNS (did DNS already exist when CERN posted their first page?), etc...along with brief descriptions of how each came to be, and maybe some way of conveying how these technologies all converged to create the internet we have today. Most "histories" of the internet I've seen are pretty scattered and it's hard to get a grasp of how things really came together. The wikipedia article, for example, barely discusses DNS and the sections aren't really tied together into a "big picture" of the internet.
Contrary to the above comment by grolaw, which suggests that we actually do like killing people for the fun of it, it is somewhat difficult, which means it's expensive.
Simply cooling the air to the mercury condensation temperature does not remove it from the exhaust. The microscopic particles will continue to float in the air stream. You have to actually capture it, while letting the huge volumes of exhaust through. There is actually no technology at the present time for accomplishing this to high purities in a coal plant. However, there are several tested methods that should be adaptable, so the EPA has given power companies a timeline to develop those methods into feasible technology. I don't know all the details, but the first stage came into effect a couple years ago based on existing technology, and I think the next stage will in 2009 or 2010.
The commercials lately are because power companies have been trying to get licensed to build quite a few new plants accross the US and are getting blocked politically. The opposition is largely not based on the actual analysis of how much of various pollutants are contributed by coal compared to other generation methods or the relative costs, but merely on the false notion that even modern coal plants are horribly dirty. The power companies need these plants to be able to supply the amount of power that is being demanded, either due to increased demand or retirement of old plants. Of course, any replacement plants can be expected to be significantly cleaner than the retired plants.
The power companies are sold on coal because of it's low cost (even with advanced emissions controls), reliability, and low supply volatility. The coal companies basically have customers lined up, but they can't sell anything more to them until the misinformation about coal is sufficiently cleared up to get the plants built. Yes, I admit it's spun a little bit, but previously the voters have only been hearing the other side of the issue, which has been spun a lot.
The emissions reduction is based on particulates released, not CO2. However, you've probably noticed several of the commercials have even promised zero CO2 plants. They are referring to a $1 billion DOE pilot project to build a super-high efficiency (co-generation) coal plant that contains and sequesters all of its produced CO2. This project was approved just a year or two ago.
The Mars Global Surveyor completed its primary 5 year mission in 2001. Of course, the hardest part of the mission was just getting there, so it was no surprise that it continued operating for additional 5 years, during which it has continued to be quite productive. Typically, space probes are operated until they no longer have fuel to manuever with, but it's always been an accepted possibility that a terminal condition could develop. For example, the Pathfinder lander's solar panels became coated with dust to the point that it could no longer power it's electronics.
In the face of some extraordinary long term successes like the Mars rovers and the Voyagers, it's easy to have high expectations for other missions, but the fact remains that MGS did it's job and then some. Frankly, I have good hopes that NASA will be able to resolve the issue, as it did previously with the rovers and in several other examples, but there's no shame if they can't.
Sir Ian McKellen, having made millions of dollars as a big name actor, is in a much better position financially to purchase the large area of solar panels needed to power his house with an excess of juice than the average person. If you will re-read the grandparent's post, you will see he is not countering the feasibility claims of solar PV cells. He is commenting on the financial reality.
In southern California, where your map shows a square meter of panel area can generate 6 kW-hours per day on average, photo-voltaics are just reaching the break even point. If I remember right, this assumes a 20 year service life and no need for energy storage. You stay connected to the grid to cover low-production times and recoup some of the cost when you're making an excess. You're still tied, albeit to a lesser degree, to traditional methods of power generation. I don't know if the if the break-even analysis includes reduced output due to degradation or not.
In Michigan, which only receives about 4 kW-hours per day, you'd only get a 2/3 of your investment back over the 20 years. In in an over-simplified nutshell, if you invest $20,000 in a solar system, you can expect to have spent $6300 more for your electricity over 20 years than just buying off the grid alone. This assumes all other factors are equal, which they're not. In California, the highest demand times are during they daytime in the summer (air conditioning), when solar power is most plentiful. In Michigan, demand increases during the winter (heating), and is presumably highest either in the morning or evening. I don't know what the regional costs of electricity are, but that's a factor, too.
One other cost that no one seems to take into account is maintenance. The power company takes care of grid and plant maintenance, which is already factored into your bill. With solar power, you're responsible for your own cells. Being solid state devices, that should just entail cleaning them a couple times a year, but it is extra time for you (money if you're lazy), and if they're damaged in a storm, you eat the cost.
Don't get me wrong, I'd love to cover my roof in Portland with solar cells, but unlike a lot of big-name actors, I haven't been cursed with more money than I know what to do with.
My point about size is that different people use cameras different, and this is actually evolving as the available cameras change. In fact, it's not that it's really a PITA, but the fact that it can be more convenient makes that a priority feature. If you genuinely want pictures and it's the only way, you'll gladly dangle a bulky camera around your neck or stuff it in a back pack. If you have the option of a camera that can fit in your pocket and not get in the way of collecting beads at Mardi Gras, that feature becomes a high priority, as long as it still has the other features you need. Furthermore, for the more casual photographers, like Joe Schmoe next door, the pictures never had enough value from the beginning to justify carrying around a large camera, but if it's pocketable, the cost/benefit ratio changes. That's a large part of why camera phones are so popular, despite their horrible picture quality.
10 years ago you go to Disneyland or Mardi Gras or a party with friends and you see a bunch of people with fanny packs carrying around film PAS cameras, and a handful of SLR fans. Now almost everybody brings along a compact digicam. You'll probably still see some people with SLR's, because they taking good pictures is part of the fun, but for the rest the camera can get in the way of the fun.
I like to take a camera with me when mountain biking, but I would bring an SLR, despite the myriad of tricky, low-light shots I've had fail to turn out on my compact, because I would spend too much space in my bag and too much time worrying about breaking it to be worth it.
Actually, the article was surprisingly fair (at least for the cliche "ten reasons you should..." genre). It began with an up front admission that DSLR was overkill for a lot of people. And any photographer should realize that while gaining some very handy features with a dSLR, they are losing another one that may very well cause them to leave their $1000 investment sitting on a shelf collecting dust: portability. SLR's aren't exactly ungainly, but they definitely aren't pocketable.
The one point the author should have emphasized is that compact digicams are mainly for taking pictures for the sake of memories. SLR's are mainly for taking pictures for the sake of pictures. Naturally, your mileage may vary.
FYI, Saudi Arabia is the 19th highest CO2 emitter in the world, but is not obligated under Kyoto to reduce emissions like the US would be, because it is a "developing nation." In fact, it's emissions grew by 40% from 1993 to 2003.
The threat is not really the Saudi or Iranian (I hope) governments killing us with nuclear bombs. The threat is either them losing a few and someone else killing us with them, or more likely, them all killing each other (the greenies who. It's been quietly discussed for quite a few years that if one country over there developed a nuclear weapons program, others may very well follow suit so they can at least hide behind M.A.D. It happened right after WWII with NATO and the USSR, and we went "holy crap" and stepped back a bit. It happened just a couple years ago in India, followed by Pakistan in short order, and they went "holy crap" and stepped back a bit. It happened in Israel in the 60's, but for the most part their neighbors didn't have the resources to follow suit immediately, and thank goodness when the Iraqis tried in 1986, the Israelis eliminated the concern. If that hornet's nest of sectarian and political tension we call the Middle East actually does follow through in the development of nuclear weapons, they might very easily say "jihad" instead of "holy crap."
The main reason it would cost $300 is because it would take almost that much investment to actually produce that can of tuna. A tuna boat spending a month at sea and bringing back 10% of the fish they currently do means the cost jumps almost 10 fold (fixed cost of operating the boat stays constant, variable cost of canning the tuna is relatively small).
Supply and demand affect price, but price also affects demand. If after all those factors are combined you're not beating the ROI you can make elsewhere, you're better off investing yourself in another endeavor.
Slashdot Mirror
I don't get this. Maybe I'm missing something obvious.
Why would the moon have a significantly greater meteoroid flux than low earth orbit? Yes gravity bends trajectories inward, but the difference in gravitational force at 150 miles versus on the surface is less than 10% on earth, which has a much stronger field to begin with.
In fact, I'm inclined to think the danger in low earth orbit is higher. In addition to yanking more objects in close, the increased gravity means they're moving faster and thus can do more damage. Plus there's space junk, both charted and uncharted.
So solar activity is a logical concern, but I think people are getting overly hyped about the meteor impacts, perhaps because of the recent study finding rates of noticeable impacts are 3-4 times what they were previously thought to be.
The one difference I do see is that in LEO, a miss is as good as a mile, while on the moon, you get "splash damage."
In addition to the obvious fact that we already have built an orbiting habitat, reading NASA's lunar architecture study report makes some advantages of a lunar habitat obvious. Of course, statements like, "With an orbital platform, materials that make it out of the Earth's gravitational pull are right where they need to be," show the author doesn't really know what he's talking about. There's also long-standing fallacy that an LEO stopoff at a space station is inherently better for exploration, and the irrelevancy of comments about mining Helium-3 when we haven't even mastered D-T fusion yet.
For those not familiar with the study, it basically looked at a variety of approaches for returning to the moon, based on the capabilities of the Orion capsule, Ares launch systems, and Lunar Surface Access Module designs and recommended the best one.
The conclusion they reached was that the most sustainable approach was to start by landing several missions in the same location in a nearly permanantly lit region near one of the poles (avoids the problematic 14-day night). Each mission would be brief, but leave behind equipment that could be used by the next. The somewhat modular concept for the LSAM (likened to a lunar pickup truck) means it could easily bring different payloads down on each mission. After 5 missions, there would be enough equipment to support extended visits, and begin research into In-Situ Resource Utilization and other long term experiments; things you flat out can not do on the ISS.
The beauty of an outpost with the capability to be permanently manned on the moon is threefold:
1.) It doesn't need to be constantly manned, or even constantly maintained. Unlike the ISS, which at the least needs periodic orbital boosts and constant power to it's orientation control gyros, you can simply "winterize" a lunar outpost and leave it for a while. If you have budget constraints or some other program setback and have to abandon it for a time, it just sits there waiting for you to come back. The ISS deals with gravity just as a lunar outpost would, but the lunar outpost actually turns it into an asset.
2.) It enables long term investigation of a piece of lunar soil, and does not interfere with exploring other parts. NASA recognizes that the LRO may find other interesting sites on the moon to send manned missions to, and the proposed architecture still supports that. At the same time, they can get an in depth look at lunar geology and practice techniques that will hopefully be used in a Mars mission.
3.) It provides a wide range of options for contributions. A criticism of the ISS is that it has been constantly hamstringed as nations, including the US, have been slow to contribute pieces...all while it continues consuming resources. The US would develop the launchers capable of putting large payloads on the surface and create an infrastructure that can support a human presence, then welcome contributions from partner nations in the form of equipment, experiments, and astronauts above and beyond the basic goals as they see fit to contribute. Among the many possible contributions NASA has identified are ISRU experiments, alternate power sources, astronomy equipment (a radio telescope would have find effectively unprecedented low level of noise), and a pressurized rover for long distance EVA's.
Of course, the author did get right the concerns over the fact that the moon is much harder to get to than the ISS, and there are more things that can go wrong getting there and back, but so many more of his criticisms are off base. Even the concern about meteoroids strikes me as wrong. I can think of no reason why the moon should encounter a greater meteoroid flux than the earth (a noted threat to the ISS), and in fact, might even be safer for the lack of space junk.
The US has built two space stations. The Russians have built three, counting their ISS contributions. Private industry is even getting in on the game (Bigelow). Honestly, how long should we wait before re-extending our presence to the moon? How much more does low-earth orbit really stand to contribute to our understanding of how to go places in our solar system?
Actually, I think a better question would be why use air?
Air has oxygen and water vapor in it, both of which react with a wide variety of materials in the right conditions. Water also condenses (obviously) well above the temperature on Titan, and oxygen boils right around the surface temperature at the ambient pressure. Condensed fluids are useless dead weight, and at the cost per pound of an interplanetary probe, dead weight is not cool. Realistically, NASA would probably choose a non-reactive, pure gas like helium or nitrogen specifically for this reason. Nitrogen has a nice feature in that the Titan atmosphere is 98% N2 (only 1.6% CH4, actually), so the difference in partial pressure inside and outside the envelope is almost neglible, and it won't leak very fast at all.
Any heat generated inside the envelope would decrease the density of a given volume and pressure, so you can achieve some buoyancy. Nitrogen or air, the latter being a worse case, are already at or above the density of Titan atmosphere, so they would need to stay significantly warmer than the outside environment to produce significant lift. The warmer it is, the faster it loses heat, meaning it needs either more insulation than just a pressure envelope, or a bigger reactor to supply more heat. Either means more weight which means more lift needed. All this time you're also increasing the launch weight from Earth. Just warming it to get more lift is a catch 22 of sorts.
So you come out far ahead if you can contain hydrogen or helium, which have 1/14 to 1/7* the density respectively at a given T and P. Because of the greater lifting effectiveness, you don't need as large of an envelope which means lower launch mass. Of course, these gasses could still certainly benefit to a degree with the power supply contained inside the envelope, and you could probably save even a tiny bit more mass in that scheme...or add more scientific payload.
The downside is that hydrogen and helium are non-polar particles with extremely small radii, so they have a serious tendency to leak out of their containers. Thus the envelope may have to be thicker to effectively contain them, which is another weight tradeoff. I couldn't make a firm conclusion off the bat, but I'd be willing to bet that helium or hydrogen still come out clearly on top. * Diatomic hydrogen has a molecular mass 1/14 that of diatomic nitrogen. Helium may have an atomic weight 4 times as much as hydrogen, but it is mono-atomic in it's natural state, so the density is only twice that of hydrogen gas.
This is true. That's why you worry about X-rays and not hues of green. However, it's definitely not as simple as frequency, either. I'm almost positive (I should google it, but I'm too lazy) there have been studies showing cancers develop in cells in a petri dish exposed to cell phone frequencies and power levels, but obviously those don't directly translate to cancer in people.
Various frequencies are absorbed preferentially by various materials. X-rays tend to pass straight through body tissue. At the opposite end of the spectrum, VLF does, too. The microwave frequencies used by cell phones are (I'm told) almost entirely absorbed by the outermost layers of skin, which are dead and thus can not develop cancer. Levels deep inside the body are so low that the odds of a codon flop should be almost infinitessimal.
This points to, but admittedly does not prove, the conclusion that cell phones are safe. My take on it is if the people who carry theirs on them 24/7 and talk for an hour or more a day don't show a clear correlation, I'm not going to worry about it when I carry mine less than a quarter of the day and talk an average of 2-3 minutes.
Charge: 0
Mass: between 10^-6 and 10^-2 eV/c^2
Spin: 1/2???
Not knowing is killing me. Do we not know the spin, or did it just for some reason get left out of both the physorg article and the wikipedia article? The Wikipedia article does say something about a fermionic superpartner called the axino, from which I would infer the axion is a fermion and axino a boson, but it doesn't explicitly say.
I find your comment very insightful, but I have slightly different thoughts on a few minor points.
While I do personally believe exactly the sort of subtle influence you mention is occurring in the various fields of acedemia, I also do believe deliberate political actions are being taken to selectively choose or suppress scientific research on both sides of the table. However, these must be limited, or it would become much more obvious. Therefore, I suspect the BBC will find some isolated incidents of rejected grants, lost data, etc. For example, we've already seen the incident in NASA where some mid-level managers marginalized Dr. Hansen's research that was indicative of global warming. I suspect cases in the opposite direction will appear, too. I think there's more to the subtle elements of bias you mention, too. There is not only the confusion of researchers with a wide array of expertise contributing conflicting data from their perspectives, there's also the possibility of scientists defining themselves into a finding. For example, if a scientist accepts a grant to characterize the effect of ozone depletion on climate models, they may get so focused on determining the scale of the effect that they misinterpret the data or the model as showing an effect when there actually is none. I can think of several instances from my own engineering experience where I've done this and later discovered the error when the applied solution did fix the problem. It's a matter of finding exactly what you expect, instead of what's really there, like Columbus "exploring" the East Indies when in fact he was in San Salvador.
Also, I wanted to add a comment about that assumed 7 temperature increase by 2100. Most reports on climate modeling I've seen show effects ranging from no change to a increase of 4-5 on the extreme end. I believe the most widely accepted models predict a 1 rise. The exaggeration is worse than you suspect. And perhaps I'm missing something, but doesn't 7 polar bear populations declining or unknown leave 13 populations stable or growing?
Lastly, I like your example illustrating assumptions about cause, but I wanted to add that referring to Al Gore in global warming discussions is like referring to Sen. Ted "the tube" Stevens in internet discussions.
This is like requiring shoppers at Walmart to pay a fee for stolen merchandise. That's only going to encourage further theft (gee, I already paid for it...it's not like I'm getting a five finger discount), and it's ridiculous from the start.
Wow, I had no idea that Microsoft cut that shady deal. Now the Universal seems to have quite literally declared they should have a right to both have their cake and eat it, too. They want you to both pay for the music and pay for not paying for it.
I don't own a media player, but now I know that if I ever get one, it won't be a Zune.
Mods, show the parent some love. I thought this was so obvious it hurt, but halfway through the discussion, this is the first time I've seen this comment:
The submitted article is also an apples and oranges comparision. Tell me sir, does your IBM XT fit in your pocket, operate for days at a time without external power, and make phone calls? Also, is your 20 year old desktop a clamshell design, has it been repeatedly dropped while you try to take drunk pictures of your friends with it, and how many total hours of use does it have compared to your phone? Perhaps a better comparison then would be your shiny new smart razor versus a circa 1995 flip phone. Not that I don't expect a somewhat similar results from that comparison, because of the point the parent made.
If durability is important to you, it has to be one of your criteria when you're shopping. It doesn't just happen. It's the same old engineering adage: Cheap, strong, capable - Pick two.
Manufacturer's generally do still make durable products if you're willing to pay a little bit more or lose some features. A clamshell presents an obvious failure point. If you want lightweight or slim, you can bet there's going to some tradeoffs in body design. If durability is really high on your list, you'd better be reading reviews or looking for items that are designed with durability in mind, like Nextel's military-spec'd phones.
Tune in next week for our kitchen special: Why do Plastic Sporks Break? - A comparison of picnic flatware to cast iron frying pans.
You need an artificial heat source in the laptop, and the cold sink is the outside environment. As mentioned in the article, the heat source would most likely be a very small burner operating at a few hundred degrees. The high temperature seems to concern a lot of people, especially those who had their sony batteries explode on them, but it is technically feasible.
However, laptops get hot enough just from their chips operating and batteries discharging at 80% or so efficiency. Trade the battery for a thermal-electic chip operating at 20% efficiency and you'll find yourself with a lot more heat to dissipate.
Since I'm not intimately familiar with their principles of operation, I'm curious how this is different from a Seeback (reverse Peltier) device. Googling around a little bit, it seems most Seeback devices achieve around 5-10% efficiency, while the article claims up to 20% efficiency, so it seems they may be slightly different physical effects. Anybody care to enlighten us?
True to some extent, but not in the practical sense. None of the old fusion power timeline estimates (most were more or less guesses, actually) really reflected the difficulty and complexity of sustaining a burning plasma. There seems to have been a natural tendency to think it was only one step up in difficulty from sustaining a fission chain reaction. In reality, that is far from a trivial challenge. In the last 25 years, researchers have invested a lot of effort learning how to heat the plasma, deliver fuel, deal with heat and neutron bombardment, and confine the plasma so it doesn't fizzle out.
ITER will finally take all these lessons and apply them to create the first truly sustained (or "burning"...ie (Q - losses) > 1) fusion reaction. From there the crew will still have to learn how to operate it on a continuous basis, applying all of the above challenges to long term experiments, and if all goes according to plan, provide a testbed for integrating a Tokamak core into a functioning powerplant.
In light of all this, I'm skeptical that fusion power prospects could have reallistically gotten more than 10 years ahead of where they are today even with more abundant funding (and according to the current ITER project timeline, the reactor will achieve first plasma late in 2016, so that's where we might be today). Of course, it doesn't help that a disappointing portion of the ITER news over the last 10 years has been the debate over whether to build it in Japan or France.
The lack of motivation still frustrates me though. The $12 billion cost of ITER is roughly the value that the US produces in raw coal every 4 months, yet we backed out of our 10% committment in 1999 until jumping back on the wagon in 2003. Throwing money at the challenges won't make them go away, but it could sure expedite solving some of them. I can only hope that once ITER starts operating (assuming no insurmountable challenges are then found), people will really see the potential of the Tokamak design and waste no time converting what we know into the design of the first generation of fusion power plants.
Actually spotting a mismatch of units like that in the volumes of derived equations (where the problem actually lay), documentation, computer source code, and part specifications as someone not intimately familiar with the project would be ridiculously lucky. While there's no denying that NASA made a preventable mistake, it's hardly as obvious as it sounds.
Read more about what actually happened, then you can comment on it.
I considered submitting the same space.com article, but you beat me to it. I think you should've focused much more in your summary on the response to the accusations (particularly the fact that the current design estimates have the Orion 10-15% lighter than the max allowed, and that the max allowed is something like 15% less than what the Ares 1 can orbit.
Really the original article could be much better summed up as "NASA engineer lays the smackdown on ignorant armchair critics" than "Constellation Battles the Blogosphere."
Frankly though, unsubstantiated claims ("I heard it from a friend at Lockheed" is not a verifiable source) on a blog (not exactly reputable either) shouldn't be worthy of a response. Apparently this guy finally touched a nerve with an engineering manager over at NASA.
Your points are true, and in fact all measurements are at some level just approximations (eg: you read a ruler measurement as 6 inches, when it is actually 6.13 inches, or you calculate a trip time based on as-the-crow-flies distance instead of road distance).
So yes, assuming the underlying theories are correct, this could be a good measurement. We don't for certain know that general relativity and quantum mechanics are correct, but currently there is almost no scientific dissent on their validity. Those theories are probably the most relevant to your point, and from my limited knowledge, I haven't been able to poke any major holes in their method. If those theories are wrong, mistaking the spin rates of these black holes is definitely one of the more trivial implications.
Of course, now that they've published their paper, their work is pretty open to criticism from some people much more intimately knowledgable about the subject. Their work has implications for several other research projects, such as LIGO, so I suspect quite a few people will be reviewing it with interest.
That is true. However, this is currently our best estimate, and the theory applied is pretty well-respected. It may be interesting to know that this finding supports a 1997 suggestion that this particular black hole spins very close to its maximum. The 1997 paper attempted to explain in theory the x-ray jets this black hole emits by suggesting it spins. In contrast, this new paper actually documents an attempt to measure the spin.
Anyway, assuming the theory is correct, their method sounds pretty plausible to me (also assuming I'm understanding the paper and article right).
Basically, the size of a black hole event horizon depends mainly on its mass. However, if the black hole is spinning (most or all are believed to due to conservation of momentum), the event horizon contracts due to frame dragging.
Of course, we can't directly see the event horizon to measure it like we can measure the sun's radius. These black holes are far too distant to resolve. But, matter falling into the black hole is heated up due to friction. Just before it passes the event horizon, it gets so hot it emits x-rays that are detectable from earth.
The clever part is that the energy of the x-rays is correlated to the emitting particle's radius from the center of the black hole, since as particles spiral in further, they heat up more and more. So if you know the mass and can measure the highest frequency of the emissions, you can calculate the rate of spin. Of course, finding the mass and measuring those x-rays is not at all trivial, and the final step of calculating the spin probably took the 6 researchers who published the paper a year or so worth of work.
It sounds theoretically feasible, but technically a nightmare. If a meteor knocked a hole in your bag (pretty likely over time), you would suddenly have a second jet, and you didn't get to pick which way it's pointed, so it's effectively uncontrolled. It might hit the earth instead of orbiting. If it broke apart due to the warming, your bag is completely history.
Plus, when was the last time somebody wrapped something that big? It would probably take hundreds of thousands of pounds of plastic, plus some sort of machine that to lay it all down. And you'd need nozzles. If you want to control it, you can't just cut a hole and call it good. And you have to the center of mass precisely, which would change as material is jettisoned, or it tumbles.
Also, you're talking about a lot of momentum change here, from a low impulse thruster. Comets move fast through the inner solar system. It would take a lot of mass and a long time to swing it into a useful orbit.
Probably a better idea is to land a couple solar or nuclear powered mass drivers on the comet that would actively launch material in the opposite direction you wanted to accellerate the main mass. It's still a major leap beyond what we can technically and economically accomplish right now...except perhaps if we found ourselves absolutely needing to and we had enough time.
All astronauts are given a budget for allowable total exposure to radiation (I'm not sure if it's broken down by approximate wavelength or not) over their lifetimes, and also for rate of exposure over shorter time periods. These are correlated to estimated increased risk of developing cancer over their life. For example, an astronaut is allowed something like 6 months of contiguous duty on the ISS and up to 1.5 years over their life. I'm not sure if those are the actual numbers, but they're in the ballpark.
Being much less protected on the moon, the times are shorter. Obviously, shielding would affect the numbers. So if you spent most of your time a few meters underground, you could stay longer.
Most of us know that distributed networking goes back to the 60's or so, with ARPAnet. In fact, according to wikipedia (I feel a slight tinge of irony looking these details up), our beloved TCP/IP began taking shape in the early 70's and ARPAnet began using TCP/IP in 1983. Meanwhile, services like Compuserve began offering private dial-up networks, and augmented them with email in 1979. Usenet popped up at the same time. The BBS's started popping up in short succession.
So all this was in place by 1990 when Tim coined the term world wide web and created the first browser, but it is the experience of browsing inter(hyper)linked files that defines most people's understanding of the internet. I suppose it's fitting to consider the start of this, if any one event, as the birth of the world wide web.
I'd really like to see a more general timeline, showing the major steps forward from the first electronic computers, first networked computers, ARPAnet, Compuserve et al, TCP/IP, DNS (did DNS already exist when CERN posted their first page?), etc...along with brief descriptions of how each came to be, and maybe some way of conveying how these technologies all converged to create the internet we have today. Most "histories" of the internet I've seen are pretty scattered and it's hard to get a grasp of how things really came together. The wikipedia article, for example, barely discusses DNS and the sections aren't really tied together into a "big picture" of the internet.
Contrary to the above comment by grolaw, which suggests that we actually do like killing people for the fun of it, it is somewhat difficult, which means it's expensive.
Simply cooling the air to the mercury condensation temperature does not remove it from the exhaust. The microscopic particles will continue to float in the air stream. You have to actually capture it, while letting the huge volumes of exhaust through. There is actually no technology at the present time for accomplishing this to high purities in a coal plant. However, there are several tested methods that should be adaptable, so the EPA has given power companies a timeline to develop those methods into feasible technology. I don't know all the details, but the first stage came into effect a couple years ago based on existing technology, and I think the next stage will in 2009 or 2010.
The commercials lately are because power companies have been trying to get licensed to build quite a few new plants accross the US and are getting blocked politically. The opposition is largely not based on the actual analysis of how much of various pollutants are contributed by coal compared to other generation methods or the relative costs, but merely on the false notion that even modern coal plants are horribly dirty. The power companies need these plants to be able to supply the amount of power that is being demanded, either due to increased demand or retirement of old plants. Of course, any replacement plants can be expected to be significantly cleaner than the retired plants.
The power companies are sold on coal because of it's low cost (even with advanced emissions controls), reliability, and low supply volatility. The coal companies basically have customers lined up, but they can't sell anything more to them until the misinformation about coal is sufficiently cleared up to get the plants built. Yes, I admit it's spun a little bit, but previously the voters have only been hearing the other side of the issue, which has been spun a lot.
The emissions reduction is based on particulates released, not CO2. However, you've probably noticed several of the commercials have even promised zero CO2 plants. They are referring to a $1 billion DOE pilot project to build a super-high efficiency (co-generation) coal plant that contains and sequesters all of its produced CO2. This project was approved just a year or two ago.
The Mars Global Surveyor completed its primary 5 year mission in 2001. Of course, the hardest part of the mission was just getting there, so it was no surprise that it continued operating for additional 5 years, during which it has continued to be quite productive. Typically, space probes are operated until they no longer have fuel to manuever with, but it's always been an accepted possibility that a terminal condition could develop. For example, the Pathfinder lander's solar panels became coated with dust to the point that it could no longer power it's electronics.
In the face of some extraordinary long term successes like the Mars rovers and the Voyagers, it's easy to have high expectations for other missions, but the fact remains that MGS did it's job and then some. Frankly, I have good hopes that NASA will be able to resolve the issue, as it did previously with the rovers and in several other examples, but there's no shame if they can't.
Sir Ian McKellen, having made millions of dollars as a big name actor, is in a much better position financially to purchase the large area of solar panels needed to power his house with an excess of juice than the average person. If you will re-read the grandparent's post, you will see he is not countering the feasibility claims of solar PV cells. He is commenting on the financial reality.
In southern California, where your map shows a square meter of panel area can generate 6 kW-hours per day on average, photo-voltaics are just reaching the break even point. If I remember right, this assumes a 20 year service life and no need for energy storage. You stay connected to the grid to cover low-production times and recoup some of the cost when you're making an excess. You're still tied, albeit to a lesser degree, to traditional methods of power generation. I don't know if the if the break-even analysis includes reduced output due to degradation or not.
In Michigan, which only receives about 4 kW-hours per day, you'd only get a 2/3 of your investment back over the 20 years. In in an over-simplified nutshell, if you invest $20,000 in a solar system, you can expect to have spent $6300 more for your electricity over 20 years than just buying off the grid alone. This assumes all other factors are equal, which they're not. In California, the highest demand times are during they daytime in the summer (air conditioning), when solar power is most plentiful. In Michigan, demand increases during the winter (heating), and is presumably highest either in the morning or evening. I don't know what the regional costs of electricity are, but that's a factor, too.
One other cost that no one seems to take into account is maintenance. The power company takes care of grid and plant maintenance, which is already factored into your bill. With solar power, you're responsible for your own cells. Being solid state devices, that should just entail cleaning them a couple times a year, but it is extra time for you (money if you're lazy), and if they're damaged in a storm, you eat the cost.
Don't get me wrong, I'd love to cover my roof in Portland with solar cells, but unlike a lot of big-name actors, I haven't been cursed with more money than I know what to do with.
My point about size is that different people use cameras different, and this is actually evolving as the available cameras change. In fact, it's not that it's really a PITA, but the fact that it can be more convenient makes that a priority feature. If you genuinely want pictures and it's the only way, you'll gladly dangle a bulky camera around your neck or stuff it in a back pack. If you have the option of a camera that can fit in your pocket and not get in the way of collecting beads at Mardi Gras, that feature becomes a high priority, as long as it still has the other features you need. Furthermore, for the more casual photographers, like Joe Schmoe next door, the pictures never had enough value from the beginning to justify carrying around a large camera, but if it's pocketable, the cost/benefit ratio changes. That's a large part of why camera phones are so popular, despite their horrible picture quality.
10 years ago you go to Disneyland or Mardi Gras or a party with friends and you see a bunch of people with fanny packs carrying around film PAS cameras, and a handful of SLR fans. Now almost everybody brings along a compact digicam. You'll probably still see some people with SLR's, because they taking good pictures is part of the fun, but for the rest the camera can get in the way of the fun.
I like to take a camera with me when mountain biking, but I would bring an SLR, despite the myriad of tricky, low-light shots I've had fail to turn out on my compact, because I would spend too much space in my bag and too much time worrying about breaking it to be worth it.
Actually, the article was surprisingly fair (at least for the cliche "ten reasons you should..." genre). It began with an up front admission that DSLR was overkill for a lot of people. And any photographer should realize that while gaining some very handy features with a dSLR, they are losing another one that may very well cause them to leave their $1000 investment sitting on a shelf collecting dust: portability. SLR's aren't exactly ungainly, but they definitely aren't pocketable.
The one point the author should have emphasized is that compact digicams are mainly for taking pictures for the sake of memories. SLR's are mainly for taking pictures for the sake of pictures. Naturally, your mileage may vary.
FYI, Saudi Arabia is the 19th highest CO2 emitter in the world, but is not obligated under Kyoto to reduce emissions like the US would be, because it is a "developing nation." In fact, it's emissions grew by 40% from 1993 to 2003.
The threat is not really the Saudi or Iranian (I hope) governments killing us with nuclear bombs. The threat is either them losing a few and someone else killing us with them, or more likely, them all killing each other (the greenies who. It's been quietly discussed for quite a few years that if one country over there developed a nuclear weapons program, others may very well follow suit so they can at least hide behind M.A.D. It happened right after WWII with NATO and the USSR, and we went "holy crap" and stepped back a bit. It happened just a couple years ago in India, followed by Pakistan in short order, and they went "holy crap" and stepped back a bit. It happened in Israel in the 60's, but for the most part their neighbors didn't have the resources to follow suit immediately, and thank goodness when the Iraqis tried in 1986, the Israelis eliminated the concern. If that hornet's nest of sectarian and political tension we call the Middle East actually does follow through in the development of nuclear weapons, they might very easily say "jihad" instead of "holy crap."
The main reason it would cost $300 is because it would take almost that much investment to actually produce that can of tuna. A tuna boat spending a month at sea and bringing back 10% of the fish they currently do means the cost jumps almost 10 fold (fixed cost of operating the boat stays constant, variable cost of canning the tuna is relatively small).
Supply and demand affect price, but price also affects demand. If after all those factors are combined you're not beating the ROI you can make elsewhere, you're better off investing yourself in another endeavor.