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You define a free agent as someone who believes the illusion you choose. If 'you' is nothing more than a collection of parts evolved to optimize certain environmental accidents then what is choice other then a series of electrical signals that terminate in tissue stimulation.

How else would you define freedom? Remember, it should be testable (at least in theory) for it to be a meaningful characteristic rather than just an invisible, arbitrary ideal. The fact that there's nothing magic or supernatural about chemistry and biology doesn't mean that conscious beings can't experience free will. And there's nothing to say that a supernatural cause of consciousness would make free will any more legitimate - it would just be adding yet another suspect cause. And, if my experience of free will is indistinguishable from "true" free will, why should I care? If there's no way, even in principle, to tell between real freedom and illusory freedom, the distinction seems to be meaningless.

Isn't it good enough to have complete predictability if you had complete knowledge?

Yes, it would be, that's how I intended my definition to be interpreted. The thing is, quantum mechanics shows conclusively that we cannot have complete knowledge OR predictability.

The uncertainty principle speaks to our ability to observe, it does not mean the information does not exist.

That's incorrect. The information truly doesn't exist. A particle's position becomes less defined when it's momentum is measured very precisely, and vice-versa. Read up on EPR some time. It was a thought experiment that showed the fundamental absurdity of quantum mechanics - the math suggested particles didn't have properties in the intervals between being measured. The idea was that this was such an absurd claim that it would discredit quantum mechanics. Unfortunately for Einstein, later work (like Bell's Theorem and associated experiments) showed that the absurd conclusions of EPR were correct - so rather than discredit QM, Einstein gave us one of the best examples of how deeply non-intuitive the world is, and it was in fact the final death of the deterministic Newtonian worldview for physicists.

Quantum mechanics experiments tell us that the information truly does not exist - there are "no hidden variables". Heisenberg uncertainty more or less puts a constraint on even the knowledge of god himself. Here's a good discussion on the subject: https://www.physicsforums.com/...

As some posters in this thread on Physics Forums pointed out in http://physicsforums.com/threa... , this result is a bad fit of the data and contradicts other experiments like the Planck satellite results.

The unreferenced Wikipedia page is wrong. They forgot about the gear ratio between the wheels and engines. Gearing trades RPM for torque. See a discussion here.

..over on physicforums.

https://www.physicsforums.com/...

perhaps someone will invent the refrigeration laser

Every test performed on GR has shown it to be correct.

Including the description of velocity addition at velocities close to c.

Basically particles with mass are unable to reach c.

I don't mind the "what if" questions, but they do need to be grounded on some established knowledge to some extent.

There is a simple reason this is controversial. Any Electromagnetic drive that produces more than 3.34 nanoNewtons per Watt by EM emission is a demonstration of new physics that is not included in our amazingly successful theory of quantum electrodynamics (QED). (The simple calculation is here: https://www.physicsforums.com/... They use a reflecting mirror, so an emitting craft would have half the force.) QED has been very precisely corroborated, sometimes to more than 10 digits (see https://en.wikipedia.org/wiki/... ). Claims of macroscopic objects that violate quantum electrodynamics simply have an extremely high prior probability of being false. (Just like claims of perpetual motion etc.). It doesn't mean we know a priori that they are false. By all means, do the experiments more precisely. But this is a claim that requires extraordinary proof because if it is true it will upset a lot of what we have good reason to think we understand about how the universe works.

Um ... both of those were more than a thousand years ago.

I'm surprised you didn't mention the 1192 event. (Note that there's rebuttal to some things mentioned in that paper.)

Why not use a thin layer of biodegradable oil as has been proposed to weaken hurricanes? That would prevent evaporation and cost a lot less, I'd imagine. I doubt the oil would cause problems since the water is likely drained from below the surface. The only downside is the possible damage to wildlife.

AC transformer PF is 1.0. AC Transformer efficiency is generally between 95%-99%. See a novice primer at https://www.physicsforums.com/....

I stand corrected. I was pulling stuff out of distant memory, based on a comment saying power transformer efficiency was AT LEAST 80%.

So my point that the GGP was full of it is even more true.

AC transformer PF is 1.0. AC Transformer efficiency is generally between 95%-99%. See a novice primer at https://www.physicsforums.com/....

Won't something think of the Moon?!

Podcasts: pick up a used ipod and subscribe to the astronomy related podcasts.

Kindle: get a used kindle that has the bubble-type keyboard, and let it read books and papers to you. The keyboard lets you start/stop the reader without looking, for in the car use. Download Calibre application and convert online/document resources and copy them to the kindle. You are not stuck with just Amazon eBooks, but many of them are good.

When online use an RSS reader and connecty to the publications feeds: e.g. http://iopscience.iop.org/ http://arxiv.org/ http://www.physicsforums.com/ http://prl.aps.org/ http://phys.org/ http://physics.stackexchange.c... http://prd.aps.org/ and many blogs!

People can go to the zoo and encounter all sorts of species they never anticipated. Where can they experience quantum mechanics?

Aha! Finally an excuse to post this link: Double-slit experiment at home (1). Thank God for technological advancements to allow for cheap laser pens. :)

There are two sorts of solar sail, those that work off photons (and, no, you don't need a mirror, since you can't afford the extra mass) and those that work off ionized particles being emitted from the sun. Ionized particles have much more momentum and are generally considered superior.

A solar sail that is 50 Km in diameter, attached to a 5 Kg probe, would accelerate that probe to 25% light speed by the time you reached the edge of the solar system.

If you built a car whose headlights could accelerate the car in reverse with photonic pressure, the headlights would vaporize a considerable chunk of the planet in front of you. You can do the calculation yourself. The equations are at http://www.physicsforums.com/s...

Let's math: Assuming that the miles high pyramid uses free sun power to melt sand and we only need PV to power lifting the glass blocks The great pyramid of giza is 455' tall and has 10^12 joules of potential energy (http://what-if.xkcd.com/95/) A 2 mile high pyramid with the same dimensions is about 12x taller if you scale up the pyramid by 12, that's 12^4x more energy (using this formula: http://www.physicsforums.com/s...) 12^4*10^12 joules=2e16 joules = 5e9 kWh wholesale price of electricity is 5 cents per kWh 5e9 kWh * .05 dollars/kWh = 250,000,000 dollars This could easily triple depending on motor losses and other energy costs. So you could make your giant pyramid with "free" energy or you could sell the energy on the open market for almost a billion dollars

Not so much.

Yes, I have seen that. The wave aspects of QM are not mysterious since some fluids can satisfy similar differential equations (there was a fluid dynamics formulation of QM in 1920s, Madelung's QM).

The strange predictions of non-local behaviors arise only from the QM Measurement Theory (QM-MT; it dates to 1920s Dirac, Heisenberg, von Neumann) which includes postulate about non-local state collapse of composite system.

The Quantum Electrodynamics has its own, newer and rigorously derived measurement theory (QED-MT) developed by Glauber in 1965 which doesn't postulate such remote field collapse, but only non-controversial local collapse, while deriving from QED dynamical equations the behavior of the composite system measurement. That theory doesn't predict non-local behaviors since all dynamics is described via local differential equations, which in Heisenberg picture look just like Maxwell equations, except that operators (matrices) not scalars are field variables. The Quantum Optics is based on QED-MT since it agrees better with what they observe. See this post and discussion explaining the difference between the QM-MT and QED-MT.

This is not the non-local collapse which some QM physicists (mystical school of thought) believe in. Everything in this experiment is local, the two superposed wave components which collapse into one are fully overlapped. Hence it is no more mysterious than your radio antenna collapsing superposed waves of thousands of radio stations striking it, into one component, that of a station you tuned in.

The real controversy is about existence of non-local collapse i.e. when two components and detectors are "far apart" (at space like distance), so that detection by detector D1 (supposedly) instantly collapses the remote field component causing the remote detector D2 to fail to detect it. Most recent experiment claiming to demonstrate such phenomenon with photon on a beam splitter actually cheated (see discussion here). In that claim they basically tweaked the timings on two coincidence circuits well out of manufacturer's specs so that they could never trigger D1 and D2 simultaneously.

Non-local collapse, which was never demonstrated empirically, does not follow from the Quantum Field Theory (discussion here) but is merely a hypothesis in the QM "measurement theory", which is the speculative, soft and fuzzy, part of the theory that has been debated among physicists, philosophers and mystics for nearly a century without getting anywhere so far.

This is not the non-local collapse which some QM physicists (mystical school of thought) believe in. Everything in this experiment is local, the two superposed wave components which collapse into one are fully overlapped. Hence it is no more mysterious than your radio antenna collapsing superposed waves of thousands of radio stations striking it, into one component, that of a station you tuned in.

The real controversy is about existence of non-local collapse i.e. when two components and detectors are "far apart" (at space like distance), so that detection by detector D1 (supposedly) instantly collapses the remote field component causing the remote detector D2 to fail to detect it. Most recent experiment claiming to demonstrate such phenomenon with photon on a beam splitter actually cheated (see discussion here). In that claim they basically tweaked the timings on two coincidence circuits well out of manufacturer's specs so that they could never trigger D1 and D2 simultaneously.

Non-local collapse, which was never demonstrated empirically, does not follow from the Quantum Field Theory (discussion here) but is merely a hypothesis in the QM "measurement theory", which is the speculative, soft and fuzzy, part of the theory that has been debated among physicists, philosophers and mystics for nearly a century without getting anywhere so far.

The elephant in the room that no one is really talking about is that Silicon doesn't really scale past 5 GHz. While it is possible to get a CPU to run at 100 GHz (yes, GHz) unfortunately
  a) you can't afford it, and
  b) can't afford to cool it.

It is going to be quite a while (decades) before (Silicon-)germanium are ubiquitous enough. The jury* is still out if graphene will pan out. Time will tell...

> It all comes down to both AMD and Intel building chips that are just so insanely powerful that folks can't come up with enough useful work for them to do, certainly not enough to max 'em out.

Yeah we can, but the market is extremely narrow. I would rather take a 100 GHz machine with 1 core, then a 1 GHz machine with 1000 cores. Not every problem can be parallelized !

There are tons of applications and algorithms that will bog ANY GHz machine; ALSO partially due to the problem of dog-slow-RAM which is an order-of-10 magnitude slower then the CPU's native L2 cache speed.

Us graphics guys (and I would imagine the AI) guys want/need 100 Ghz + 10,000 core machines for real time processing (we already work with a 2,000 core GPU! i.e. Scientific/Math computing via nVidia CUDA.) The rest of the general public doesn't give a fuck about GHz, cores, and slow bottlenecks like hard drives / memory speeds.

* http://www.physicsforums.com/showthread.php?t=564490

Graphene is where silicon was in 1948 (the first transistor used Germanium BTW): basically nice in theory and very promising but many practical issues existing that prevented even lab prototype devices from being made. It wasn't even possible to make a reliable silicon transistor until the mid-to-late-1950s.

Will graphene be practical in only 10 years? It's a long shot because of current infrastructure and technologies: ...

PS - This is a good read - but my FTL expectations down: http://www.physicsforums.com/showthread.php?t=231008

Yes, the ice trapped in the turkey quickly turns to water then steam. This steam takes up a lot more volume causing displacement of the oil. Now you have hot oil incorporated with steam and air escaping its container, some of this oil forms a vapor could which is ignited by the oil that runs down the side in to the gas flame. The oil doesn't auto-ignite, the gas flame does that.

That depends. Are we talking about the inertial mass, or the gravitational mass? They may be numerically equal, but that doesn't mean they are the same thing.

They are the same thing. If they weren't, general relativity wouldn't work.

Although I hate to take sides in these types of theoretical musings, just because we think it's the same today, doesn't mean it's really the same. Many people already suspect that generally relativity is an approximation (like the newtonian approximation before it) and that when you get to the planck scale something else is likely gonna happen. Consider that people once thought that by applying a constant force, you could accelerate arbitrarily "fast", but the universe didn't turn out to work that way.

If it turns out that a mass's resistance to acceleration is a scalar field effect (one of the possible Higgs-boson mass models), it seems to me that gravity got a whole lot more complicated since it has to interact with particles the same relative way to yield exactly the same equivalent mass.

That depends. Are we talking about the inertial mass, or the gravitational mass? They may be numerically equal, but that doesn't mean they are the same thing.

They are the same thing. If they weren't, general relativity wouldn't work.

Not a dumb question at all. If you're actually interested in discussing this sort of thing, one place to go is PhysicsForums. Here's a thread and paper on this topic. The general consensus is that annihilation events should be visible if a lot of the universe were made out of antimatter, but we don't seem to find any. (My very very unpolished view is that matter and antimatter were produced in slightly differing amounts for some reason during the universe's formation and the vast majority of both annihilated each other over time, leaving only a sliver of leftover, regular matter.)

Here's Bill Nye's response to WattsUp's experiment, explaining why they failed to reproduce results that have been successfully reproduced over and over and over again by other scientists, organizations, and amateurs.

What's sad is that the AGW skeptics give so much link-love to this bungled demonstration, that the other experiments get pushed down in the google results. AGW Skeptics are a lot like evolution-deniers in this regard, who also push anti-evolution nonsense to the top of all google results. It must be nice to have so much free time to promote this propaganda, while real science is so careful, nuanced, and time-consuming it gets lost in the politics.

I attended SC11 (sc11.supercomputing.org) last year. FORTRAN is still the work horse of (large-scale) numerical computing. C/C++ are popular. So are MATLAB and R. They was even a NumPy tutorial and some sessions on emerging languages like Chapel. But FORTRAN was king.

I thought this was an interesting thread about FORTRAN v. C -- http://www.physicsforums.com/showthread.php?t=169974

Off-topic:When it came to programming, the general drift of the conference was not toward new languages, but toward adding meta-information, vis-a-vi compiler directives.

A discussion of the refrigeration laser in Brin's novel "Sundiver" is at the Physics Forum here.

Brin's science fiction writing, by the way, is very good. He's won all the big awards in the field (Hugo, Nebula, Locus), at least in part because he knows his material (B.S. Astrophysics, MSEE, Ph.D in Space Sciences, various post-doctoral honors, NASA exobiologist) . He also has some interesting ideas on sociology and politics, though not all of what he proposes is practical. His website is at davidbrin.com.

The enemy would be terrified by the noise, but I suspect wouldn't risk much from the gun, as a projectile exiting the barrel (or whatever passes for a barrel in a railgun) at 5000 mph instantly vaporizes when it hits the atmosphere.

You're thinking of Santa.

My experience from BS, MS, and PhD were pretty rough. I always felt I was learning a bunch of prescriptions: do this to get that. It would often take me years of self study to pin down the history of what I had learned, from good texts and references. A decade after finishing school, I finally felt I had tracked down all that had mystified me. I finally put together a syllabus of the miniminal set of physics ideas and math methods, references and key literature for students, from sophomore to postgraduate to study on their own and make their school experience better. I posted a short version (document at http://www.physicsforums.com/showthread.php?t=540829&highlight=aalaniz ) more for the physics major, and, SCROLL down, a long document for STEM majors. I hope this helps. Alex Alaniz

1. Reactor 1's cooling system likely failed due to the quake, not the failure of the backup diesels. This opinion is based on analysis of the remaining sensors, that indicated the reactor was having problems even while the battery-powered cooling was still running. The existing plumbing and wiring had been embrittled from 4 decades of operation in a quake zone and proximity to, well, a nuclear reactor.

No, reactor 1 failed first probably because an employee mistakenly shutted the isolation condenser system (a passive cooling system) http://www.physicsforums.com/showthread.php?p=3572578#post3572578

2. Design flaw and hardware failure: locating the backup diesel generators in a basement under the reactors, such that they were guaranteed to flood if water entered the area.

Reactor buildings are relatively waterproof, the failure of the diesel generator was due to the fact that they were located in the turbine buildings. For the more recent reactors 5 and 6, the diesel generators were located inside the reactor building and were not flooded.

3. Design flaw: locating the spent fuel pools directly above the reactors in the same buildings, such that if the reactor had a little problem (hydrogen explosion, or moderated prompt criticality), said fuel would get blown sky-high, which it did in the reactor 3 explosion.

No, the spent fuel pools are not located above the reactors, and I cannot remember any report of used fluel rods being blown in the air due to the hydrogen explosions.

4. Design flaw: no externally located terminals for "connect portable generators HERE", and no rationalization of Japan's two different electrical standards (it's a fucking nuclear power plant that will blow up if not cooled, so support both standards, guys).

Nothing to do with Japan having 50hz / 60hz zones. The problem was that all the electric panels were flooded (they should have installed them at a safer place).

5. Management failure: All reactors should have been flooded with seawater immediately after the quake, as soon as the situation on the ground at the site became clear. This might have averted the hydrogen explosion by keeping the reactors cool enough to not oxidize the zirconium fuel-rod cladding. Local personnel correctly identified the situation, remote management denied permission to flood the reactors with seawater (because that basically ends the reactor's productive life). Eventually a local guy did so anyways.

How do you inject seawater in reactors without working pumps ? The response to the accident was delayed because the roads were unpracticable due to the earthquake and the tsunami, even the power plant was a field of debris where it was nearly impossible to drive a vehicle.

The radius of the observable universe is about 14Gly, not 14Gpc

The radius of the observable universe is about 46 Gly. http://physicsforums.com/showthread.php?t=506987

Does this mean that we're in a Godel Universe, and that closed timelike loops are possible?

No. The Godel metric has rotation and closed timelike curves, but not all cosmological solutions that have rotation have CTCs. The Godel universe is not consistent with observation. For descriptions of some cosmological models that have rotation but no CTCs, see the references here: http://physicsforums.com/showthread.php?t=506988

So we still can't say objectively that the universe is spinning.

No, if this result is correct then we can say the universe is spinning. FAQ

Although, this outwards acceleration could possibly explain the expansion of the universe (instead of "dark energy").

The upper bounds on the universe's rate of rotation are such that it cannot have any significant contribution to the universe's expansion. (See the references in the FAQ link above.)

If the universe spins... what is it spinning in? "Space"?

Does space therefore exist outside the universe (other than in some theoretical brane)?

http://physicsforums.com/showthread.php?t=506988

The actual paper is here: http://arxiv.org/abs/1104.2815

Here is a FAQ entry about rotation of the universe and how general relativity would describe it: http://www.physicsforums.com/showthread.php?t=506988

There's nothing intrinsically wrong with the idea. It's perfectly consistent with all the known laws of physics. There is in fact no well-established physical principle that should make non-rotation any more likely than rotation. There are other techniques for detecting rotation of the universe (see the references in the FAQ entry); their claim would become much more convincing if it could be confirmed by one of those techniques. If it's right, then it probably implies that inflation was an incorrect theory; I believe that in cosmological models that include both rotation and inflation, the angular velocity dies out exponentially, so it should be unobservably small today.

Yeah, if anyone knows a way I can search the Google index for sequences like ">>" please let me know!

I know I have seen this topic treated in books, but cannot find anything. I did find the following two links, however:
http://stackoverflow.com/questions/2711780/question-about-char-input
http://www.physicsforums.com/archive/index.php/t-8093.html

Some old memories come up from jmorris42's post recommending Relativity; The Special and the General Theory. I read that when I was in junior-high, did a book-report on it (I wish I had the book report to read now), and phoned the university to ask some anonymous physics professor questions about it. I haven't looked at it since, so I can't really judge how accessible it was.

I would say that Steven Weinberg's "Gravitation and Cosmology" was the most accessible book that I studied at university.

A book that tried to be accessible, but was all over the map was Misner, Thorne, and Wheeler's "Gravitation". If you just go through and pick and choose sections, it's probably good too.

Here's others's opinions at physics forums

You'll have to decide what you mean by "understanding" the theory. There are many different levels of understanding and only you can decide what you are comfortable with, and what level of understanding meets your needs.

A tube mic preamp can be much cleaner and musical with less THD than any amplifier on a chip.

[Citation needed]

I'm sorry I don't have a citation to support the GP's claim, but I have heard something to the effect of even- vs. odd-ordered harmonics. Distortion due to even-order harmonics (tube) is subjectively more pleasing than distortion due to odd-order harmonics. Thus, even with worse THD, tube amplification may still sound "cleaner and [more] musical". See this general discussion on harmonics.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

The Japan Earthquake thread in the nuclear engineering forum at physicsforums.com has become a more reliable and timely source of information on the stricken reactors at Fukushima than mainstream news sources, according to commenters posting from Japan. The latest news:Japan's Nuclear and Industrial Safety Agency says air may be leaking from theNo 2 and No 3 reactors at the Fukushima Daiichi power plant.Another example, as of March 30, 11 AM JST: Radioactive iodine 3,355 times legal limit found in seawater near plant. Another from March 30: IAEA Confirms Very High Levels of Radiation Far From Reactors.

April 11, 2011. The Japanese government's nuclear safety agency has decided to raise the crisis level of the Fukushima Daiichi power plant accident from 5 to 7, the worst on the international scale. Also, see this post from the physics forum. In each case, the news was available on physicsforums.com before publication in the mainstream press.

Let's hope that the Japanese government does not suppress this essential source of information.

Neutron embrittlement.

http://www.physicsforums.com/showthread.php?t=96256

Wikipedia lacks an article for this. This is another thing that is dealt with much better in newer plants that it was in the '70s. There was a lot of reserve in the design because neutron embrittlement as not well understood, but eventually that safety margin will be used up.

Another reason to scrap old plants and build new ones, assuming we are going to stay with nuclear power.

Thanks for the links, I'll check those out. OOI, was the 1/1000 ratio for the "survival" rate or for the "survive AND walk away" rate (and what's the other value very roughly)? I know it's all very much guesswork, but even an "off-by-an-order-of-magnitude" margin-of-error would still prove interesting :)

A while back, I wrote about surviving such a fall by carrying a 3-5 metre pole, maybe made of carbon-fibre or stronger. Not something you're likely to have on you, but in theory, and with a lot of skill and practise, one could use it all the time to save oneself. You would clench the pole as the pole hits the ground to allow for a massive (but less so than concrete!) deceleration at the last moment, as you slid down the pole. See this thread for details, and let me know what you think if you like: http://www.physicsforums.com/showthread.php?t=314044

Does anyone else think sometimes that physicists are just coming up with crazier and crazier ideas just to see what we'll buy?

While I agree it is a bit mind boggling to think about, it seems that several different approaches to Quantum Gravity predict this phenomena of dimensional reduction at small scales (high energy). Thus it's not just a whack idea they've thrown out there.

I couldn't find the thread I had in mind, but this has been discussed several times at the Physics Forums board, see for example this thread:

Those who read in this forum are probably aware of the remarkable coincidence that three actively pursued approaches seem to agree on a contraction of dimensionality at microscopic scale. In all three (Loop, Triangulations, and UV-Safety) the microscopic geometry seems to become fractal-like and the spacetime dimensionality goes from 4D down to around 2D at very small scale.

Yes, it does apply. Laser light is subject to the inverse square law like any other light.

Not according to posts (below), summarizing:

The inverse square law applies to light radiated in all directions. The reduction in intensity is because the same amount of light is covering an ever expanding area. With a laser, you're sending the light in a straight line (theoretically, at least). The light beam covers the same amount of area 10 miles from its source as it did when it first left the laser.

The inverse square law applies only to isotropic light sources. A laser is highly directional and thus does not obey the inverse square law.

http://www.physicsforums.com/showthread.php?t=37462
http://www.diyphotography.net/the-inverse-square-law-cheat-sheet-myth-basted
http://www.teachersdomain.org/resource/ket08.sci.phys.mfw.ketinverse/
http://www.scienceforums.net/topic/9586-laser-and-inverse-square-law/

Basically Google "+laser" +"inverse square"...