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Are you trying to suggest that only pretenious wankers by Macs?

Nope. Especially since I have a Powerbook along with my XP gaming box and Linux server. :)

I am saying that if you can choose between several different products, and they all present the same functionality, then other factors come into play, such as looks.

For example, any laptop would've worked for the web-surfing, email, and digital camera uploads that I need when I travel. My Powerbook is nice looking and easy to carry since it's so small (12" G4 Powerbook). The power adapter is small and packs up nicer than any other I've seen. So, I bought it for its form, since functionality was already taken care of.

Side note: while I've traveled with Dells and Thinkpads for years (the butterfly-keyboard Thinkpad was my favorite for a long time), I've never been stopped and asked about my laptop until I started carrying my Powerbook.

My server box on the other hand, is an ugly Frankenstein monster. It does its job and lives in a closet, so who cares about looks.

I think this is something the geek community forgets - that most non-geek people place looks right up alongside price and functionality.

Will a continued fraction do instead? It's just [1,2,2,2,2...].

Actually, this is a somewhat interesting question, as I don't think any BBP-type formula for sqrt(2) is yet known. Such a formula would allow the computation of specific digits of sqrt(2) without requiring storage of the others (in a particular base, not necessarily base 10, base 16 is common).

http://crd.lbl.gov/~dhbailey/dhbpapers/bbp-formula s.pdf doesn't list one, but does give such a formula for pi sqrt(2).

"because when it comes right down to it, they're safer. Sadly, the reason they're safer is they destroy anyone or anything not in an equivalent vehicle."

Actually there have been a lot of studies that have shown the opposite, for example have a look at the chart on page three of this pdf. You'll see that in this study the amount of deaths of the primary driver per million sold is higher in SUV's than large cars, midsize cars, minivans and imported luxury cars. Compact & subcompact are worse for the primary driver - obviously tin cans with a motor don't handle accidents well! Pickup trucks are the second worst and I'm suprised they're not more similar to SUV's. The worst is sports cars, possibly a combination of the historically bad handling of american sports cars and the fact that 150-200mph on a suburban road is usualy a bad idea!

Cells will fail and will need replacing from time to time, and will be expensive to do.

Most manufacturers Guarantee their panels for 20-30 years, so that is minimum life. Of course on average they will last longer. Longer than most power plants, and yes, virtually maintenance free.

home energy usage is pretty much the exact inverse of when the most solar radiation is available

In fact, the average electricity demand on the grid typically follows the sun cycles, especially in summer when electricity use peaks. The peak grid loads are typically ~40% higher at midday than the nighttime minimum. Even in the winter, when the day peaking is less pronounced (and shifted towards morning/evening), solar could address as much as 35-40% the national electricity demand even without storage. See http://currentenergy.lbl.gov/pjm/index.php for an example of demand curves.

Of course storage on the grid is important, and needs work, but we could address a HUGE amount of US electrical need without it.

However, for serious microgeneration, at the current time the only halfway practical and affordable renewable energy source is wind, which is vastly cheaper

Wind is very cheap, not halfway practical cheap, but cheap as coal cheap. Hydro is very cheap as in cheaper than coal cheap, and photovoltaics are the cheapest thing going when you don't have a 100 year old subsidized grid infrastructure. Because of that, photovoltaics is the only option in many places in the developing world, because the cost of the lines is 10 times more expensive than the coal plant that make the power. But more importantly, PV is getting exponentially cheaper to manufacture by the decade, and new low cost technologies are just starting to leak out of the lab into a marketplace near you. (However, note that demand has outstripped supply by 30% with 40%/year growth in the market for several years, even if the manufacturing is getting cheaper, it is not currently seen in the market because of high demand).

Bottom line, renewables are the cheapest things going, even without addressing the huge subsidy imbalance going to traditional fuel sources (oil, coal, nuclear, etc)

The energy to make a typical wind turbine is generated by the turbine over a period of six months - it's more like 6 years for solar.

Photovoltaics cells have an energy pay-back period ranging from 3 months for newer technologies (e.g. CIS, CdTe) to 3 years for traditional crystalline silicon. Even mainstream multi-crystal silicon has a payback period of 0.8 years. And these numbers don't even address the newer, and lower embodied energy low cost multi-junction concentrators or low temp printable cells.

So when you look at a 30 year life span, that gives PV an Energy return on investment of 10:1 for Crystal Si, 37:1 for multi-Crystal Si, and 100:1 with CIS. Compare that to typical fuels: Coal (9:1), nuclear (4:1), US oil (3:1), Mid-east oil (10:1-30:1).

Unless photo voltaic solar becomes vastly cheaper, it's simply a non-contender except for novelty value, even if you live in the desert.

A desert is not needed as solar insolation is relatively uniform throughout the US (and world). The best location in Arizona is only twice as good as the worst place in the Washington rainforest, with the majority of the US within 80% insolation of the best location in Arizona!

Even with today's "high" PV prices, PV is unique in that it is deployable on any rooftop, parking lot, or yard at the point of use. With net-metering or battery storage that means PV competes with retail energy not w

I think people focus on this a lot, or I just notice this more then other things. But it is highly overstated. There are far worse devices then a console. Check this out. Look at the listed items (the list is a bit old, consoles still showing at 1.1 W): Digital Cable Box - 23 Watts. A regular one is still over 15 W in idle. I would be far more concerned with those then I would be consoles. (I am pretty sure there are more cable boxes in the US and Worldwide then game consoles that are actually plugged in, not counting those dust collecting NES and Atari).

Actually, let us take a look at the soon to be average (if we ever get converted to digital) TV setup. Digital TV = 8.8W, Digital Cable Box = 23W, and DVD Player (don't most people have these?) 4.4W. Now, idling that is 36.2W of power usage. This is for something that is very likely more common then a console is. Power "leakage" (such a horrible word) is bad, but it is a sympton of two things:

1) Instant Gratification: Devices receiving power constantly are that much closer to being instant-on, allowing you to get to enjoying your DVDs and television programming faster. They have to keep certain things in standby modes to keep load times down.
2) Features and Adv. Functionality: You know, being able to power on devices with the remote, having time-of-day clock setups (there are a few devices that really do not need them), and external displays with time and other information on them at all times.

I am sure there are other reasons related to technology needed certain power requirements, but I really believe some of the great increases in idle power usage (cause that really is what "leakage" is) are not necessity. I am sure governments will attempt to regulate this a bit better, but we all know what a joke government regulations can turn into.

I'm not sure where your figures come from. According to this, the average American uses about 6,000kWh per year. At that rate, an extra $.04/kWh is $240 per year. Not great, but it's competitive for those with the "green" bug.

The substantial uncertainties currently present in the quantitative assessment of large-scale surface temperature changes prior to about A.D. 1600 lower our confidence in this conclusion compared to the high level of confidence we place in the Little Ice Age cooling and 20th century warming. Even less confidence can be placed in the original conclusions by Mann et al. (1999) that "the 1990s are likely the warmest decade, and 1998 the warmest year, in at least a millennium" because the uncertainties inherent in temperature reconstructions for individual years and decades are larger than those for longer time periods, and because not all of the available proxies record temperature information on such short timescales.

Ah yes, the infamous hockey stick (the chart). It was what convinced me that global warming was human-caused. Until of course I found that when you put random data into the analysis, you got a hockey stick.

What it comes down to is that more than 200 years ago we didn't have accurate temperature measurement. Everything before that is an educated guess. And the precision necessary to show a fractional degree of change is simply unattainable.

Where are the error bars on the hockey stick? It's shown as if we had exact data for the last 1000 years--which of course we don't.

Two four story cooling plants? Huh? Assuming about two football fields (115,200 sf) and 300 w/sf(1), their cooling load should only run about... 10,000 tons. Assuming they throw in good 1200-2000 ton centrifs, thats fewer than 8 chillers, each with a footprint of about 200 sf (including tube pull service space). Double it for pumps and random aux equipment, and it still doesn't add up to a 4 story building (one of them must be the cooling towers).

That better be a 4 story cooling tower with a 4 story thermal storage tank charged by the cooling towers at night. If Google is honestly putting in 4 stories of electrical cooling equipment, they need to talk to someone stat - before dropping 6 MW onto Oregon's grid that could be avoided by cashing in on waterside economizing and a tank (using towers, assuming that thermal pollution of the Columbia is not an option). Hell, if you want to go cutting edge use the waste heat from the racks to run an adsorption chiller or something. OK, that's a bit silly, but theoretically possible (and despite the ghetto website - the translation from the manufacturer's native tounge isn't so hot - there are adsorption chillers installed in at least one critical facility I know of).

Comeon google, don't be evil. Go and design an actually efficient datacenter for once. Talk to the local boys at LBNL. They can help. If that thing ends up full of CRAC units with those hideously inefficient fans and no airside economizer (equivalent to opening the windows for the 70% of the time outside air is cool enough to condition the space)(with proper humidity lockouts, computers don't melt in filtered outside air you know), you are evil. EVIL!

1. And for that they better have a very tight hot aisle/cold aisle setup, or some very non-google'esqe custom/complex water cooling (coils on the racks would be doable, and possibly flexible enough for Google to go for, probably in a cheaper custom buy than commercial systems). I've never measured 100 w/sf (although close is becoming common), nevermind 300 w/sf, and have only designed for 150 w/sf with 300 w/sf expansion potential once; that involved a 4' raised floor for a supercomputer center, but it might be possible overhead with very good air management. So, 300 w/sf average over the entire space, not just one rack footprint, is a reasonable max load guesstimate.

Found the urls. Take a look at these, they may help:

The Original method for enriching Uranium, and the easiest to build for a nation who wants to do so was the Calutron.

...Methods of enrichment? Well, shit...I guess the Calutron has to go back into the closet. Since it was used long before there were any reactors, and uses low tech methods, Iraq would never use one.

What you say is true, but HP and Varian were in Silicon Valley as second-generation startups.

The first generation was the Federal Telegraph Company, founded by Cyril Elwell in the winter of 1909-1910 (originally as the Poulsen Wireless Telephone and Telegraph Company). Never heard of it? It was built to commercialize the arc (not spark) transmitter developed by Valdemar Poulsen, and by 1918 had succeeded in building and operating 1-megawatt continuous-wave radio transmitters.

Elwell was not only a Stanford graduate, he got his first financing for the company from Stanford faculty members, including the president of the university. So it can truly be said that Stanford itself acted as the first venture capitalist for the Valley.

Like the startups to follow, Federal people often left to do great things:

--Since it needed receivers to go with its transmitters, Federal hired a man from New York to develop a receiver for it, and set him up in a laboratory in the bay area. There, Lee DeForest would invent the triode vacuum tube (valve).

--To transfer the arc transmitter technology from Denmark to the Valley, Poulsen sent some of his employees with the equipment. One quickly became disillusioned with Federal, but liked the Valley, and started working with speakers. Soon thereafter, Peter Jensen formed his own company, Magnavox. Jensen's name lives on today in several lines of audio products.

--Leonard Fuller, longtime chief engineer of Federal, eventually ended up on the Berkeley faculty. The story goes that one day during the Great Depression, he was sitting in the faculty cafeteria when Ernest O. Lawrence was complaining that his cyclotron research was limited by the size of magnetic pole pieces he could obtain. Fuller realized that the 1-megawatt arc transmitter Federal had designed had very, very large magnetic pole pieces and, as they were too heavy (80 tons) to scrap, several had been sitting unused in a Valley warehouse since the end of World War I. A donation was quickly arranged, and the unused Federal components came to play a significant part in the development of large particle accelerators.

Correct, and that's only for Single Precision. For double precision, it drops to 14.6 GFLOP/s. See this paper.

Having been to the 8,000ft level of Homestake, I'll confess, it is spooky! Radios would be nice.

However, deeeeeep mines (gold in Homestake's case) are probably vastly out numbered by 'shallow' coal mines in the Eastern US.

As a side note, /.'ers should help lobby to turn the now defunct Homestake into one heck of a laboratory...

http://neutrino.lbl.gov/Homestake/LOI/
http://www.state.sd.us/homestake/
http://en.wikipedia.org/wiki/Homestake_Mine_(South _Dakota)

Well, I'd like to understand how you think Java is "designed for scalability". In my experience, it scales up poorly: its garbage collector is limited, object allocation has a huge overhead compared to other systems, and its libraries (e.g., collection libraries) don't work well for big collections. It seems to me Java fails already in some pretty elementary areas of scalability.

Sorry, but this is obviously nonsense, because scalability is the primary reason why major corporations use Java. E-Bay is one of the highest traffic sites on the web, and they use J2EE.

So who am I to believe about this - you or E-Bay, or most major banks, or stock exchanges handling hundreds of millions of transactions each day on J2EE?

Come on, be concrete. What does "one of the primary languages" mean?

I don't know - why don't you ask them?

A lot of places are using Java for research in parallel computing (and Edinburgh may be one of them); it's convenient for research because Java fails to address many of icky details of numerical computing (eg. structs, multidimensional arrays, efficient genericity, machine floating point, efficient error handling, extra precision, ...). But most major Java numerics efforts (including Java Grande, which Edinburgh's EPCC prominently refers to) died about three years ago when it became clear that Sun wasn't going to fix Java for numerical computing. If there is any life left in numerical Java, I'd like to hear about it. As far as I can tell, Sun never even bothered to implement their multidimensional array proposal.

You are right that Java is not well-designed for coding numerical work - it is syntactically awful for that (even so, that has not put me off), but this is not the point. This was an illustration of Java performance; that it is no longer the sluggish poor relation to C it used to be.

Java numeric work is still active - just because one project or site dies, does not mean things are over. There are now commercial numeric packages in Java such JSML, and open source packages like colt:

"There is a perception by many that the Java language is unsuited for such work. However, recent trends in its evolution suggest that it may soon be a major player in performance sensitive scientific and technical computing. For example, IBM Watson's Ninja project showed that Java can indeed perform BLAS matrix computations up to 90% as fast as optimized Fortran. "

"The latest stable Colt release breaks the 1.9 Gflop/s barrier on JDK ibm-1.4.1, RedHat 9.0, 2x IntelXeon@2.8 GHz."

So, who do we believe? IBM, CERN or you?

Well, for the kind of client you have in mind, so would I, because it's easy to sell to their management, because they have the money to pay a premium for Java and Oracle, and because they can easily pay for it. Hey, if they insist and they pay, we'll write in assembly language. But for my own company, I wouldn't dream of using Java and Oracle--it's way too expensive and development is way too slow.

Sorry, but I don't sell to management. I sell to the technical experts of the company who understand IT. You can ignore my point if you wish, but to have a platform you can trust matters - you can't (yet?) trust Mono for robust commercial server apps. Some of the companies may soon grow to the point where they will need clustered services. Mono simply doesn't provide that on Linux. J2EE does. This is not a management choice - it is a serious technical one.

The Mono developers agree about this - so who do I believe about this - you or them?

To say that development in Java and Oracle is expensive and slow is just utter rubbish. You can develop with Java and Oracle for free, and there is no reason why development in Java should be any slower than with your favourite language - C#.

Yes, isn't it great? I think the J2EE standard is really holding back Java. Oh, in the short term, a "standard" gives man

[...] The question is what to do about it. We can: (1) Totally ignore it. (2) Put our entire economy on hold.

3)Or anything in between.(my emphasis)

4)To determine what we should do requires a lot more information than we actually have. (my emphasis) [...]

Well ... option 1) is what the US have been doing for the past 10 years or so. Satisfied with the results? Option 2) has been cited all along to argue that it made no sense to a) find out if there really was a danger, b) why actually doing anything about it was out of the question anyway, and c) all this talk about climate was a load of bunkum purveyed by starry eyed doo-gooders and jealous pinko's out to rob us of our economic leadership anyway.

So I'm very pleased to see that the poster actually caught on to option 3) "anything in-between", despite the traditional catch-all excuse for doing nothing voiced in the same breath under 4). Tradition is hard to shake off, I know, but it can be very misplaced. There may be lots of residual questions relating the connection between global warming and catastrophic climate change, but why would we want to wait until all the t's are crossed and all the i's are dotted? What would that gain us? At most it would tell us that some measures would be unnecessary, allowing us to save some effort and some money. Great, but is that worth the risk of missing out on a hard or soft window of opportunity w.r.t. climate change? Personally I think not, but that's just my opinion.

I put it to you that being as energy-efficient as feasible is the obvious thing to do. It may not be a total solution, but it helps. Let others (e.g. the government) worry about the large-scale issues (after all that's what they're paid for) ... but make sure that they _do_ worry about it and don't pass it off as "counter to our economic interest". But being a little more energy-efficient is something that all of us can do, starting today. Both at an individual and at a national level. Not just because it would reduce CO2 emissions that would otherwise take place, and hence contribute to one of the probable causes of global warming, but also because our main energy source, mineral oil, is an increasingly scarce resource. And one which (in my personal opinion) currently is way too cheap in the US.

The only additional information you'd need is: how do I identify and implement measures that make sense from an economic, practical, and technical point of view?

On an individual level there are lots things (ranging from small to ambitious) that can be done in and about the home. Home-owners, renters, and small businesses can find detailed information on how to save energy (and money) here: http://hes.lbl.gov/hes/vh.shtml.

There are government subsidies (see http://www.dsireusa.org/) for energy-saving measures, that can reduce the financial burden of implementing energy-saving measures for businesses and individuals.

What more information would you need to get started?

I forget the name of the C++ library and it's past 5 o'clock here so everyone has left. We have moved on to the Colt http://dsd.lbl.gov/~hoschek/colt/index.html matrix library.

Actually I don't recycle my own poop the local water company does extracting methane initially and then passed over to farmers who spread it over thier fields.

California has a fair bit of coastline perhaps some turbines might be located offshore. maybe geothermal energy is a possibilty too. Biodediesil and sugar producing crops should grow well in california. I don't live in california but i would guess air conditioning is a fair proportion of energy use.

http://www.oksolar.com/solar_home_systems/
might be of interest to you.

Myself I went for the easier option
http://www.npower.com/At_home/Juice-clean_and_gree n.html

My electricity is generated by renewables.
hybrid cars seem to be a combination of expensive and still not that fuel efficient.

cars like the renault megane claim over 60 miles to an imperial gallon (4.454 litres) US gallon is 3.785 litres
runnning a 1.5 litre diesil engine. when your paying around 96p close to $1.75 a litre fuel efficiency becomes important.

As for energy use
http://www.calvert-henderson.com/energy.htm
shows that american energy use per person is twice that for western european nations such as the UK.

however this page shows california to be quite energy efficient for an american state
http://www.lbl.gov/Science-Articles/Archive/energy -myths1.html

most uk homes are not very energy efficient however I can tell you that this room is lit by a 15 watt energy saving bulb which equates to the same as a 60 watt bulb. I do have 20 watt bulbs which equate to 100 watt bulbs. They last longer too.

If you could reduce your own energy use then you could save yourself money and get better returns on your states windfarms.

http://www.earthscan.co.uk/news/article/mps/UAN/42 8/v/3/sp/332749698941328167358

reports on many projects including some in california.

I don't know if you have the equivilent of npower juice in california but if you have the choice of supplier choosing one which is prepared to use renewables to generate your electricity will help and you can be part of the solution.

I am doing research into the pondoromotive force at the moment work goes slow because my Uni has nothing that can produce the effect. Hell, we can't even make our damn buckyballs.

My boss asked me one day what options were available for automatic CD replication, which ran through completing however many CD copies as requested, with as little human intervention as possible. After we got direction from higher, we were able to have this CD replication system installed, albeit slightly modified. It works so well, that it's definitely one of the coolest purchases we've made.

• galaxy rotation curves (you're right that this alone doesn't tell us about the universe's energy budget, just that of galaxies)
• gravitational lensing (a surprisingly independent measure of the stuff in galaxies and galaxy clusters)
• structure formation (you need more matter than the visible amount for the structure we see to form quickly enough)
• the cosmic microwave background (the shape of the first two peaks of its spectrum tells us about matter and dark matter densities)

I am intrigued by who this guy is though. He doesn't really seem to be on the radar - very little info to be got from Google. I think he is not a physics prof.
Some sleuthing turned up the following:
1) He's an MIT graduate.
2) He a (very) few published papers on the idea in his slides.
3) He worked for a company called Affymetrix that makes gene microarrays.
4) One of the physics faculty at Penn State, who works on carbon nanotubes, is called Alexander Mayer, but reading his CV, I think this is not the same person.
5) There's some personal info here from a housing ad he posted on a berkely lab page.

OAKLAND HILLS home, furn bdrm & ba avail for visiting scholar, euro style decor, lge closet, desk/computer workstation, DSL, lge secluded patio on 1/3 acre with stunning view, lge liv room, close to trails & Chabot observatory, 36" telescope for use, secure storage, close to pub trans, exc kitchen, share home w/ single, straight professional male homeowner, age 38 w/ no pets, $1,200/mo incl util on a month-to-month basis, pref pros in astrophysics/physics/math, Alex, amayer@alum.mit.edu

That's about all I can find.

Prof. Muller from the UC Berkeley physics dept. is into this theory. He has a webpage devoted to it. Others in the dept. regard him as a bit of a crank for his interests, but he's not a total crackpot.

Looks like a rip off of an OnLamp article from a few months ago, and not a very good one at that! At least the OnLamp article explained how to tweak a few more OS's and the math was correct. And just to add insult to injury the article on OnLamp was written by one of those Berkeley guys ;-)

Lawrence and His Laboratory

Where do you think the unit of measurement came from? I visited my brother at MIT in '88 or '89, when the bridge (and the Smootlines) had been rebuilt... I thought it was the best thing about MIT (I learned differently later). on the origin of the Smoot.

A study by Lawrence Berkeley National Laboratory found that several compact and mid-size models, such as the Volkswagen Jetta or the Toyota Camry, have significantly lower rates of driver death than almost any SUV. For several SUVs, such as the Jeep Grand Cherokee, the Ford Expedition, the GMC Jimmy, and the Toyota 4-Runner, the driver risk is more than 50% greater than for the Camry.

In a separate study, Tom Wenzel at LBL found that there was very poor correlation between vehicle weight and driver safety.

A study by Lawrence Berkeley National Laboratory found that several compact and mid-size models, such as the Volkswagen Jetta or the Toyota Camry, have significantly lower rates of driver death than almost any SUV. For several SUVs, such as the Jeep Grand Cherokee, the Ford Expedition, the GMC Jimmy, and the Toyota 4-Runner, the driver risk is more than 50% greater than for the Camry.

In a separate study, Tom Wenzel at LBL found that there was very poor correlation between vehicle weight and driver safety.

They should be honored that Pokemon was chosen as a name. Naming new and increasingly harder to find genes and protiens after cartoon or video game characters is a recent but honored tradition in the scientific community. A tradition very similar to the compas system of naming electrophoretic blots. The lawyers have demonstrated their lack of vision and absolute cluelessness for a culture they could live 100 lifetimes and still not understand. Don't believe me? Just ask Sonic Hedghog.

NASA also had a need for bigger rockets, and plans to go higher than 100km. According to Professor Richard A. Muller, in his: http://muller.lbl.gov/teaching/Physics10/PffP.html class, getting from 100km to 200km requires ~33 times as much energy. Something the Spaceship One, is not nearly capable of!

Magnetic field reversals coincide with mass surface life extinctions, I'll bet it won't do us any good if it happens in our lifetime.

Not true (the mass surface extinction part). Sediment layers have shown that magnetic field reversals happen relatively frequently (compared to extinctions). This site has several theories but there's a graph near the bottom showing reversal rate, with some periods hitting as high as 12 reversals per 2 million years. How many mass extinctions were there in the last two million years?

Now, there is a question raised in the article over whether magnetic field reversals may be linked to epic-scale eruptions/lava flows that have been related to mass extinctions, but the graph suggests it's more of a slight shiver before the earthquake, rather than the final blow itself.

Actually, you shouldn't use it on ducts. You might have better luck using it on a duck.

regrettably a recent study has shown that the one thing that 'duct' tape is really not good for, is repairing ducts... (heating ducts anyway, the glue melts)

It's apparently good for warts though

But if you have a low intensity of gamma radiation, i.e. a low number of photons, then you have ipso facto a low intensity of energy production. The number of gammas is directly proportional to the number of distintegrations. That sounds like it just won't do if you want a compact source of lots of energy.

I think you have a misunderstanding of radioisotopes. Sr90, for example, is another common isotope used in RTGs. It produces no Gamma radiation to speak of. Of course, it may produce gamma farther down the decay chain (radioisotopes usually go through being a few different elements before reaching a stable state), but in its initial decay it's perfectly safe. I wish I still had the link that showed all the decay states. According to the EPA website, however, Sr-90 decays next into Y-90 which (if I'm reading this page correctly) produces a fraction of 1% of its radiation as Gamma rays.

But if you have a low intensity of gamma radiation, i.e. a low number of photons, then you have ipso facto a low intensity of energy production. The number of gammas is directly proportional to the number of distintegrations. That sounds like it just won't do if you want a compact source of lots of energy.

I think you have a misunderstanding of radioisotopes. Sr90, for example, is another common isotope used in RTGs. It produces no Gamma radiation to speak of. Of course, it may produce gamma farther down the decay chain (radioisotopes usually go through being a few different elements before reaching a stable state), but in its initial decay it's perfectly safe. I wish I still had the link that showed all the decay states. According to the EPA website, however, Sr-90 decays next into Y-90 which (if I'm reading this page correctly) produces a fraction of 1% of its radiation as Gamma rays.

Er, I believe all energy from radioactive decay, other than what's in the kinetic energy of ejected particles, comes out as gammas. I don't think there are any radioactive decay schema that don't involve gamma radiation. That's just how the nuclear energy levels are spaced. I could be wrong, but it seems to me asking for a nuclear reaction that doesn't generate gamma photons is like asking for a chemical reaction that doesn't generate infrared photons (i.e. heat).

(Pu-238 produces a host of gammas and X-rays, so far as I can tell.)

I don't see how shaping the isotope helps your shielding problem. You've got radiation leaving every surface of the isotope. You need a certain thickness of shielding over that, determined by the frequency of the emitted photons (I'm assuming very thin shielding will do for the emitted particles). How can shaping the isotope help?

I'm not meaning to criticize, I'm just raising a few questions. I'm no expert. For all I know they have easy answers.

Still, it would be nice to have some major shakeup in physics... there really haven't been any in my lifetime.

How old are you?
Inflation as a solution to cosmic microwave anisotropy

Problems with General Relativity: Dark Matter?

Dark Energy. 90% of everything.

Pioneer anomaly.

Every year, in every field, we answer more and more questions. However, every answer raises many more questions. We are still exploring our ignorance, but we know more about it every day. What are you doing to help?

Recent advances have made 50+% efficiency look more doable. For example, this group is working on techniques that could theoretically yield 56%.

http://www.lbl.gov/msd/PIs/Walukiewicz/04/04_1_3ba nd.pdf

What ever happened to the "huge" discovery 3 years ago of the large bandgap of InGaN which is convieniently tuned to the solar spectrum. They were claiming a theoretical efficiency of >50% in a single dual junction cell, 70% for multilayer junctions! Then......nothing. Not a single thing. Haven't heard a word about it since. wtf.

I'm sure all of you that complain about this Intel system using 400W when an AMD system would use perhaps 200W are also energy conscious in other ways, right?

You turn on power saving nodes (Intel's Speedstep, AMD's Cool n Quiet)?
You use 55W fluorescent torchiere lamps instead of 300W halogen ones, right?

http://www.lbl.gov/Science-Articles/Archive/torchi ere-SMUD.html

You could easily save as much power on lighting in your house as you do on computing costs.

Don't forget the smoot!

Making up some magic phenomena for explaining the difference between such a broken model and reality is just bad science. Once they got some believers, this "dark matter" can be used to "explain" all sorts of other phenomena with an appropriate amount of hand waving.

Actually, the best evidence for dark matter and dark energy come from the study of type Ib supernovae and the bizarre observation that the more distant they are the faster they are accelerating away. Check it out here.

Fermi also said that at a time when we were constantly discovering new mesons and baryons and QCD had not yet been developed to put it all together yet.

These days we know that mesons are baryons are not fundamental. Remembering the names of the fundamental particles really isn't that hard and it's worth your time:

Six kinds of quarks: up, down, strange, charm, top, bottom
Six kinds of leptons: electron, muon, tau, electron neutrino, muon neutrino, tau neutrino
Force carriers: photon, W+, W-, Z0, gluon

That's it for the standard model. Most people will agree that the graviton should be added to the list of force carriers, although nobody has observed one yet. There's also the Higgs (or possibly a family of Higgs particles), which hopefully the LHC will either observe or disprove. Then you start getting into stranger possibilities like supersymmetry (which is reasonably well supported by theory) and various whack-job theories (which aren't).

Since you never see bare quarks (a subject of last year's Nobel Prize, I believe) it's worthwhile to know some of the more common baryons (for instance, protons and neutrons) and mesons (learn your pions...and maybe kaons). But trying to memorize them all is pretty pointless, as you can have a lot of different combinations of quarks (especially when you start talking about excited states). Check the Particle Data Group (http://pdg.lbl.gov/) if you need to look up info on a particular particle.

It is very easy to setup a Linux HPC cluster. There are several projects out there for example:

http://www.rocksclusters.org/ (Rocks guys do a great job of simplifying the process. I highly recommend this one if you are new to Linux Clusters)

http://warewulf.lbl.gov/pmwiki/ - Warewulf cluster toolkit. Not as easy to use as Rocks but some very cool features and very flexible for different kinds of Linux Clusters.

http://oscar.openclustergroup.org/ - Oscar Toolkit is popular as well. I can't comment on it much since I haven't tried it.

There are other cluster solutions, i.e. http://warewulf.lbl.gov/pmwiki/

But you can also roll your own. I did mine with Fedora by taking a fresh Fedora install, duplicating the common parts into a common NFS share, duplicating the distinct parts into a template and subsequent node NFS shares, compiled a custom NFSroot Fedora kernel, then setup a DHCP and TFTP server for the diskless nodes to PXE boot from.

burnin

There are other cluster solutions, i.e. http://warewulf.lbl.gov/pmwiki/

But you can also roll your own. I did mine with Fedora by taking a fresh Fedora install, duplicating the common parts into a common NFS share, duplicating the distinct parts into a template and subsequent node NFS shares, compiled a custom NFSroot Fedora kernel, then setup a DHCP and TFTP server for the diskless nodes to PXE boot from.

burnin

Would you, perchance, have seen a study that actually for once addresses bremsstrahlung doses with more than a passing mention? Every time I see a study on radiation exposure for a Mars mission, after long detailed calculations on what would be needed to meet minimal health standards, there's usually a couple of lines to the effect of "These calculations do not include the effect of bremsstrahlung radiation, which can be expected to significantly increase the total radiation dosage." All of the studies I've seen use incredibly simplistic models (often a 1d radiation source impacting perpendicularly to a one or two layer shield).

GEANT is pretty good at this, and it's not hard to use. It would be easy for NASA or whoever to do some quick & dirty studies with it with some simple material model for what an interplanetary spacecraft might look like. If they haven't done this, they ought to.

And btw, I don't think it makes much sense to talk about 'bremsstrahlung doses'. Brem from a particle as energetic as a cosmic ray can easily have enough energy of its own to pair produce... and those particles in turn may also brem, etc.

This is called an electromagnetic cascade. And it doesn't necessarily start with a bremsstrahlung photon. Figure 2 in the fine article shows a hadronic part of a cosmic ray shower, which happens to include a pi0. The pi0 secondary has a very short life, and so will decay into two photons before it travels an appreciable distance. These photons will probably be energetic enough to produce the same kind of electromagnetic cascade that high energy bremsstrahlung would. This is why I personally would talk about doses due to electromagnetic showers in general, rather than bremsstrahlung. There is no logical separation.

Just in case you don't already know all this -- look at figure 27.17 on page 22 of this review article. This shows the expected amount of energy deposited for a shower caused by a (30 GeV) electron as a function of material depth. Of course the location of the maximum depends on the energy of the impinging particle.

So TFA is effectively saying: if the design of spaceships requires that astronauts have to sit to the left of the maximum for high energy cosmic rays, and if this is the main source of radiation for astronauts, then it would be good to move the astronauts as far left of the maximum as possible. I.e., use a material for the walls of the spacecraft that is thin in terms of radiation lengths.

To estimate the actual dose you expect the astronauts to get, then you need a reasonably detailed simulation. To accurately estimate the actual health effects is more difficult. But high energy cosmic rays are the main problem, then the basic optimizing principle is pretty clear.

I very seriously doubt that 10% of current electricity usage in the US is used to power computers, even if the additional air conditioning power requirements were included. See http://enews.lbl.gov/Science-Articles/Archive/net- energy-studies.html

It's also Carbon, something regularly used for resistors (prior to film resistors.) Seems resistance and heat will be some kind of issue.

Actually, carbon nanotubes are as conductive as copper...here's a nice resource .