"The theory really is that in every multiverse where the LHC works correctly, the multiverse is destroyed by the abominable bosons. We are all riding through a series of universes in which the LHC repeatedly fails to work."
But that semi-sophistry could apply to any conservation law or forbidden transition:
Put on your spooky voice and say "The creation of a particle in a configuration which violated conservation of momentum would cause such a Disturbance In the Force that it would wipe out the whole of the Universe, so we are sailing in a sea of universes selected from the Master Multiverse for which only momentum-conserving outcomes just happened to take place".
More reasonably, physicists say, "Some transitions are forbidden due to conservation laws" and there are observable consequences. This is normal physics.
Would the present hypothetical Higgs case be any different?
I think that some of the theory may be taken seriously but I agree with you, "causality", or any other law-of-physics-violating principle doesn't necessarily create large macroscopic effects. Things can just not happen which would otherwise happen.
This isn't too obscure, it's part of the laws of physics.
After all, why do we have to generate a certain beam energy to make certain particles (non-virtually)? Because if you don't then you violate a mass-energy condition.
And what about particles coming out "here, in this direction" but none coming out "there, in that direction"? Conservation of momentum rule.
Then other transitions ("matrix elements") can be forbidden because, e.g. they don't conserve charge*spin*time invariance or something like that.
When you don't observe particles that would violate it, does it happen because all the detectors on that axis blow their tubes? No, the particles simply fail to come out in that configuration and fail to cause a signal.
One also has to consider the statistical mechanics. Consider all the potential states of the wavefunctions which uphold state-transition-forbidding-law-Z (the proposed theory is an unusual one of these). Which are thermodynamically most probable? The human-scale catastrophic outcomes written about require immense statistical-mechanical coincidences, even if they are technically valid solutions to the state-transition-forbidding-law-Z.
If the theory has some validity, it seems that the observations will turn out to work the way all other similar particle physics experiments work: no direct isolated particles come out at the energy that we'd expect them too, even though other relationships & statistics of stuff we do observe suggests a mass-energy which is obtainable.
Other laws of physics appear to prevent unbound quarks from shooting off. When people tried to make a quark-generating machine, did Nature arrange it so that it blew up? No, instead we got mesons and other quark-containing stuff flying off---but no free quarks, even though we have evidence indirectly that there are quarks with certain mass, charge and other quantum numbers.
I think it's pretty likely the original authors (who are actual serious scientists and not cranks) thought of this. It could be a good trick, to make romantically outlandish predictions. The consequences are then that their particle theory gets put near the top of the (very, very long list) for being tested when the LHC data finally start streaming in.
In Slashdot notation:
Problem: you have a radical particle theory. But so does every other string and particle theorist out there, so almost all will get ignored and never tested.
1. Propose science-fiction-style consequences and make outlandishly provocative predictions, like failure of LHC. 2. LHC scientists get offended, run LHC successfully and test the boring computations that THEY did on your stupid theory to show that LHC won't blow up. 3. It's true! Relativistic causality issues in Higgs interactions results in newly confirmed conservation law! 4. Win Nobel Prize! 5. Profit!
Re:ah yes, anti-perl tirades are refreshing
on
Coders At Work
·
· Score: 1
Fortran, as in am modern Fortran like Fortran 95, is [b]not[/b] a terrible programming language for physics problems.
For some of those problems, it's better than almost all alternatives. I like it much much better than perl.
It's suited to its domain at least as well, and is far less idiosyncratic.
As applied in statistical modeling it is a process which selects the model which fits the data the best. Thus it it makes me irate as my understanding is in opposition with its classical use.
In fact it isn't. The classical practice is selecting the model which fits the data the best, known as "model selection".
Ensemble methods do little "yes/no" model selection and instead make predictions from weighted combinations of many base predictors. To make a prediction, you need to score many or all of the base models and combine their outputs.
The use isn't incommensurate with musical connotation.
"There's a lot of argument over why ensemble techniques work well in general, when using them on well-posed statistical problems."
My opinion:
1) It's a form of regularization & noise averaging. Different classes of estimators have different systematic errors and proper averaging almost always performs better than any single estimator. In more limited contexts, e.g. parametric estimators with variable numbers of free parameters (small compared to # of data points) this is well established in Bayesian contexts. It's like regularization in the sense that the averaging will exclude the howlers---occasional idiosyncratic screw-ups from any single estimator, phenomena that tend to happen with under-regularized estimators.
2) "But in the collaborative filtering case, they work well at least in part because there's not a canonical way of posing the problem statistically that's also tractable--- there are instead multiple ways to view the problem, which expose different information. Aggregating those views is a pretty straightforward way of getting more information."
If the thing to be predicted also includes the unknown parameter of "exactly how are the judges going to define the performance metric", then similarly averaging over different possibilities is a good risk-minimization strategy.
In practice (knowing how people watch movies and what netflix cares about)the statistical setting of Netflix seems to be this:
There is an unknown distribution of draw tuples of (movies, people, ratings). (in practice, "date-of-rating" and"date-of-movie" turn out to be additional useful data).
You have observed a large number of these tuples already.
Then, given a number of draws for (movies, person, ratings) where person is fixed, predict the the rating given (new_movie, same_person).
The asymmetry is natural because movies and people are not interchangable: movies do not have opinions about people.
I don't consider Netflix to be very ill-posed statistically.
[quote]NASA is not only smaller than the U.S. Air Force's space program, it is also smaller than the National Security Agency's space program as well. [/quote]
You mean, National Reconaissance Office and Defense Mapping Agency.
People forget that the Apollo project killed off the much more reasonable X-plane [wikipedia.org] development, one of which by 1962 was already flying at an altitude of sixty miles. Progression to space travel was seen as the logical next step.
Except for that pesky lack of oxidizer up there.
More realistically, development of the rocket programs was sublimated competition with the USSR on ICBM technology.
Given how far back the USA started in rocketry and hence ICBMs in the 50's, proving the ability to put a large mass exactly at the right point at the right moment with all the ancillary communication networks indicated that the USA also had the ability to put a large mass at the right point at the right moment 100 meters away from ground zero.
Of course, upon examination by other people (Also, sadly, smarter than I am), it turns out the underlying logic of Bell's Theorem applies equally to these other forms of mathematics, that they can't reproduce the actual results of QED any better than any other deterministic theory, and the universe is still irritatingly non-deterministic at a fundamental level.
I swear, it's the mathematical equivalent of intelligent design.
Yes indeed, but not the way you think.
Orthodox QM is more like 'intelligent design'---as in there's some Mystery In Which Thou Art Not Allowed To Further Explore, It Just Was The Word
Determinstic physical evolution in a state space is how the rest of physics has always worked. The assumption of "magical genie putting the rand in the random", at not really-well-times which depend on the observer's reference frame.
Bell's inequality also has to have some kinds of assumptions which may be experimentally untrue.
I'd much rather keep Hilbertspaceness (a real mystery in itself) plus fractal geometry (even in functional space) if the laws of physics turn back into deterministic, nonlocal, realism.
Palmer is certainly knowledgable about dynamical systems:
"The Invariant Set Hypothesis proposes that states of physical reality belong to, and are governed by, a non-computable fractal subset I of state space, invariant under the action of some subordinate deterministic causal dynamics D. The Invariant Set Hypothesis is motivated by key results in nonlinear dynamical-systems theory, and black-hole thermodynamics."
(This isn't unsuprising as he works at ECMWF, European Centre for Medium-Range Weather forecasts. Contemporary climate & weather researchers know all about nonlinear dynamical systems.)
In classical physics, the asymptotic distribution of states (where in state space a 'thing' could be) is known as the 'invariant set'.
The "action of a deterministic dynamics" means integrating forward the equations of motion. In some cases, e.g. if you have a chaotic system, you end up with a 'strange attractor', with strange meaning fractal, non integer dimension.
(Simple determinsitic motion, like a stable orbit of a (assumed point mass) planet has an invariant set of a closed ellipse in state space.)
It is also possible to have fractal invariant sets without chaos ('strange non-chaotic attractors').
The paper itself is far from a complete worked out theory, it is at the stage of "here is an interesting suggestion to work on".
It could turn out to be quite wrong---as in predict things that we know are experimentally untrue. It could turn out to be neat idea but useless, or best yet, it could produce new frac
If it turned out to be quite real and useful, it would vindicate Einstein over Bohr on QM.
I've heard Leon Lederman wanted to call it the "goddamn particle" because dealing with was turning out to be such a bitch, but the book publisher made him change the title.
"Which is how does a device that stores an electrical charge (a battery) via magnetism not go dead based simply on inductive coupling with nearby metals?"
Firstly, inductive coupling requires time dependent magnetic fields and probably realistically macroscopically reinforcing ones so that the field strength is appreciable at a distance.
And then it could be locally thermodynamically stable, like opposing domains on a ferromagnetic surface, like a hard drive.
Hard drives wont to spontaneously erase themselves to 'all zero' over human lifetimes.
The global lowest energy state is "all spins pointing the same way".
I disagree. "Writing software properly" apparently means taking on a huge burden for simple operations.
Quoting T'so:
"The final solution, is we need properly written applications and desktop libraries. The proper way of doing this sort of thing is not to have hundreds of tiny files in private ~/.gnome2* and ~/.kde2* directories. Instead, the answer is to use a proper small database like sqllite for application registries, but fixed up so that it allocates and releases space for its database in chunks, and that it uses fdatawrite() instead of fsync() to guarantee that data is written on disk. If sqllite had been properly written so that it grabbed new space for its database storage in chunks of 16k or 64k, and released space when it was no longer needed in similar large chunks via truncate(), and if it used fdatasync() instead of fsync(), the performance problems with FireFox 3 wouldn't have taken place."
In other words, if the programmer took on the burden of tons of work and complexity in order to replicate lots of the functionality of the file system and make it not the file system's problem, then it wouldn't be my problem.
I personally think it should be perfectly OK to read and write hundreds of tiny files. Even thousands.
File systems are nice. That's what Unix is about.
I don't think programmers ought to be required to treat them like a pouty flake: "in some cases, depending on the whims of the kernel and entirely invisible moods, or the way the disk is mounted that you have no control over, stuff might or might not work."
Nuclear experiments in 1855? Surely you joke. Nobody in 1855 knew what a nucleus was, or was even convinced about the atomic theory of matter.
In fact, nuclear fission was discovered in 1938, and large scale full production systems were operating by 1945 (Hanford), with commercial utility turn-on by mid 1950's.
Nuclear fusion was discovered in early 30's, I think, before fission.
The reason why nuclear fission went from discovery to exploitation immediately, and fusion is still really hard, is due to the laws of physics.
Specifically:
1) neutrons have charge zero, but nuclei don't. 2) strong force is very short range
These will never change.
And yes, the original poster is right, NIF isn't helping much for energy production.
Fission/fusion hybrids and burning actinides are stupendously good ideas.
But why a complex ICF with so many fundamental engineering issues in the way (fuel delivery, cycling drive)----instead of the ICF in the middle, a continuously operating tokamak or whatever can provide, today, squillions of fast neutrons. There are problems making it substantially over unity electrical output versus input but if you let the fission take care of the energy production, magnetic confinement reactors are generations ahead of ICF in producing massive neutron fluxes.
Fueling and drive are far easier (i.e. gas transfer and microwave magnetrons, 1940's technology) than yet to be mastered ICF technology.
"The only ones that come close in ability to provide a large amount of energy are fission and solar, and they have the disadvantages, respectively, of long-lived actinide waste, and massive land use."
Long-lived actinide waste is not an immutable issue with nuclear fission.
Nearly all of the long-lived actinide waste can be burnt up by fast neutrons, whether from fission reactors, fusion reactors or particle accelerators.
The physics is known, but the engineering details (i.e. what makes the most sense given $$$$) aren't yet.
On the other hand, massive land use and capital costs are immutable problems with solar because of the energy density of the solar flux at the Earth's surface.
Unfortunately, National Ignition Facility has nothing to do with energy production and everything to do with nuclear weaponry.
In reality, it is a physical simulation of the tough part of nuclear weapons design, the transfer of photon radiation to the thermonuclear secondary. There are extremely complex and exotic fluid dynamics. These results are used to calibrate the simulation codes for nuclear weapons, which are all about thermodynamics & radiation transfer, and not about nuclear physics.
For energy production research they probably wouldn't have used lasers (far too inefficient vs charged particle beams, but particle beams create less weapon-like conditions) and would have concentrated far more on the engineering aspects of power production.
The even sadder reality is that if it had been designed for energy production research it would never have been funded.
"I don't see any problem with the leaders of North Korea or Iran deciding that 80% of their population had to be sacrificed. I think that is a decision they could easily make. So MAD doesn't work for them at all."
North Korea's leaders might be happy with sacrificing 80% of its population, but only if they got to choose, as they usually do on such matters.
This isn't true any more---since probably mid 60's 70's.
Most modern nuclear weapons (e.g. those deployed by the USA), gain a major fraction of their design yield from fission of U-238 in the secondary, maybe 50%.
The actual push for 'clean' weapons stopped after above-ground tests were eliminated by treaty.
A significant amount of the dangerous fallout is direct fission products and remnants of the warhead case itself. The fallout for a modern 400kt warhead would be say 15-20x that of Nagasaki, as you have 200kt of fission product vs 10kt.
Yes, a dozen or two kg of fully fissioned uranium (modern weapons get probably 80% of the potential nuclear energy from fission & fusion fuel) really does make a huge load of nasty fallout.
Slashdot Mirror
It doesn't matter where the urging comes from since it's not like the CEO can tell that you've followed his suggestion or not.
In many circumstances where the government asks people to comment (e.g. changes to SEC rules), all comments, along with names are made public.
So yes, they probably can tell.
"The theory really is that in every multiverse where the LHC works correctly, the multiverse is destroyed by the abominable bosons. We are all riding through a series of universes in which the LHC repeatedly fails to work."
But that semi-sophistry could apply to any conservation law or forbidden transition:
Put on your spooky voice and say "The creation of a particle in a configuration which violated conservation of momentum would cause such a Disturbance In the Force that it would wipe out the whole of the Universe, so we are sailing in a sea of universes selected from the Master Multiverse for which only momentum-conserving outcomes just happened to take place".
More reasonably, physicists say, "Some transitions are forbidden due to conservation laws" and there are observable consequences. This is normal physics.
Would the present hypothetical Higgs case be any different?
I think that some of the theory may be taken seriously but I agree with you, "causality", or any other law-of-physics-violating principle doesn't necessarily create large macroscopic effects. Things can just not happen which would otherwise happen.
This isn't too obscure, it's part of the laws of physics.
After all, why do we have to generate a certain beam energy to make certain particles (non-virtually)? Because if you don't then you violate a mass-energy condition.
And what about particles coming out "here, in this direction" but none coming out "there, in that direction"? Conservation of momentum rule.
Then other transitions ("matrix elements") can be forbidden because, e.g. they don't conserve charge*spin*time invariance or something like that.
When you don't observe particles that would violate it, does it happen because all the detectors on that axis blow their tubes? No, the particles simply fail to come out in that configuration and fail to cause a signal.
One also has to consider the statistical mechanics. Consider all the potential states of the wavefunctions which uphold state-transition-forbidding-law-Z (the proposed theory is an unusual one of these). Which are thermodynamically most probable? The human-scale catastrophic outcomes written about require immense statistical-mechanical coincidences, even if they are technically valid solutions to the state-transition-forbidding-law-Z.
If the theory has some validity, it seems that the observations will turn out to work the way all other similar particle physics experiments work: no direct isolated particles come out at the energy that we'd expect them too, even though other relationships & statistics of stuff we do observe suggests a mass-energy which is obtainable.
Other laws of physics appear to prevent unbound quarks from shooting off. When people tried to make a quark-generating machine, did Nature arrange it so that it blew up? No, instead we got mesons and other quark-containing stuff flying off---but no free quarks, even though we have evidence indirectly that there are quarks with certain mass, charge and other quantum numbers.
I think it's pretty likely the original authors (who are actual serious scientists and not cranks) thought of this. It could be a good trick, to make romantically outlandish predictions. The consequences are then that their particle theory gets put near the top of the (very, very long list) for being
tested when the LHC data finally start streaming in.
In Slashdot notation:
Problem: you have a radical particle theory. But so does every other string and particle theorist out there, so almost all will get ignored and never tested.
1. Propose science-fiction-style consequences and make outlandishly provocative predictions, like failure of LHC.
2. LHC scientists get offended, run LHC successfully and test the boring computations that THEY did on your stupid theory to show that LHC won't blow up.
3. It's true! Relativistic causality issues in Higgs interactions results in newly confirmed conservation law!
4. Win Nobel Prize!
5. Profit!
Fortran, as in am modern Fortran like Fortran 95, is [b]not[/b] a terrible programming language for physics problems.
For some of those problems, it's better than almost all alternatives. I like it much much better than perl.
It's suited to its domain at least as well, and is far less idiosyncratic.
As applied in statistical modeling it is a process which selects the model which fits the data the best. Thus it it makes me irate as my understanding is in opposition with its classical use.
In fact it isn't. The classical practice is selecting the model which fits the data the best, known as "model selection".
Ensemble methods do little "yes/no" model selection and instead make predictions from weighted combinations of many base predictors. To make a prediction, you need to score many or all of the base models and combine their outputs.
The use isn't incommensurate with musical connotation.
Algorithms produce better results working in committees, unlike you.
"There's a lot of argument over why ensemble techniques work well in general, when using them on well-posed statistical problems."
My opinion:
1) It's a form of regularization & noise averaging. Different classes of estimators have different systematic errors and proper averaging almost always performs better than any single estimator. In more limited contexts, e.g. parametric estimators with variable numbers of free parameters (small compared to # of data points) this is well established in Bayesian contexts. It's like regularization in the sense that the averaging will exclude the howlers---occasional idiosyncratic screw-ups from any single estimator, phenomena that tend to happen with under-regularized estimators.
2) "But in the collaborative filtering case, they work well at least in part because there's not a canonical way of posing the problem statistically that's also tractable--- there are instead multiple ways to view the problem, which expose different information. Aggregating those views is a pretty straightforward way of getting more information."
If the thing to be predicted also includes the unknown parameter of "exactly how are the judges going to define the performance metric", then similarly averaging over different possibilities is a good risk-minimization strategy.
In practice (knowing how people watch movies and what netflix cares about)the statistical setting of Netflix seems to be this:
There is an unknown distribution of draw tuples of (movies, people, ratings). (in practice, "date-of-rating" and"date-of-movie" turn out to be additional useful data).
You have observed a large number of these tuples already.
Then, given a number of draws for (movies, person, ratings) where person is fixed, predict the the rating given (new_movie, same_person).
The asymmetry is natural because movies and people are not interchangable: movies do not have opinions about people.
I don't consider Netflix to be very ill-posed statistically.
[quote]NASA is not only smaller than the U.S. Air Force's space program, it is also smaller than the National Security Agency's space program as well. [/quote]
You mean, National Reconaissance Office and Defense Mapping Agency.
"warp drive" is now being used in some speculative General Relatvity research papers about, well, warp drive.
In fact the term is so well known from Star Trek that there really isn't any other good word to describe it, and it is scientifically description.
Of course Gene Roddenberry knew what GR had to say about such things from the get go.
People forget that the Apollo project killed off the much more reasonable X-plane [wikipedia.org] development, one of which by 1962 was already flying at an altitude of sixty miles. Progression to space travel was seen as the logical next step.
Except for that pesky lack of oxidizer up there.
More realistically, development of the rocket programs was sublimated competition with the USSR on ICBM technology.
Given how far back the USA started in rocketry and hence ICBMs in the 50's, proving the ability to put a large mass exactly at the right point at the right moment with all the ancillary communication networks indicated that the USA also had the ability to put a large mass at the right point at the right moment 100 meters away from ground zero.
Of course, upon examination by other people (Also, sadly, smarter than I am), it turns out the underlying logic of Bell's Theorem applies equally to these other forms of mathematics, that they can't reproduce the actual results of QED any better than any other deterministic theory, and the universe is still irritatingly non-deterministic at a fundamental level.
I swear, it's the mathematical equivalent of intelligent design.
Yes indeed, but not the way you think.
Orthodox QM is more like 'intelligent design'---as in there's some Mystery In Which Thou Art Not Allowed To Further Explore, It Just Was The Word
Determinstic physical evolution in a state space is how the rest of physics has always worked. The assumption of "magical genie putting the rand in the random", at not really-well-times which depend on the observer's reference frame.
Bell's inequality also has to have some kinds of assumptions which may be experimentally untrue.
I'd much rather keep Hilbertspaceness (a real mystery in itself) plus fractal geometry (even in functional space) if the laws of physics turn back into deterministic, nonlocal, realism.
Palmer is certainly knowledgable about dynamical systems:
"The Invariant Set Hypothesis proposes that states of physical reality belong to, and are governed by, a non-computable fractal subset I of state space, invariant under the action of some subordinate deterministic causal dynamics D. The Invariant Set Hypothesis is motivated by key results in nonlinear dynamical-systems theory, and black-hole thermodynamics."
(This isn't unsuprising as he works at ECMWF, European Centre for Medium-Range Weather forecasts. Contemporary climate & weather researchers know all about nonlinear dynamical systems.)
In classical physics, the asymptotic distribution of states (where in state space a 'thing' could be) is known as the 'invariant set'.
The "action of a deterministic dynamics" means integrating forward the equations of motion. In some cases, e.g. if you have a chaotic system, you end up with a 'strange attractor', with strange meaning fractal, non integer dimension.
(Simple determinsitic motion, like a stable orbit of a (assumed point mass) planet has an invariant set of a closed ellipse in state space.)
It is also possible to have fractal invariant sets without chaos ('strange non-chaotic attractors').
The paper itself is far from a complete worked out theory, it is at the stage of "here is an interesting suggestion to work on".
It could turn out to be quite wrong---as in predict things that we know are experimentally untrue. It could turn out to be neat idea but useless, or best yet, it could produce new frac
If it turned out to be quite real and useful, it would vindicate Einstein over Bohr on QM.
A serious question:
can the LHC be run at less than maximum energy in order to get the best distributions of backgrounds vs particle number for the particular experiment?
I've heard Leon Lederman wanted to call it the "goddamn particle" because dealing with was turning out to be such a bitch, but the book publisher made him change the title.
"Which is how does a device that stores an electrical charge (a battery) via magnetism not go dead based simply on inductive coupling with nearby metals?"
Firstly, inductive coupling requires time dependent magnetic fields and probably realistically macroscopically reinforcing ones so that the field strength is appreciable at a distance.
And then it could be locally thermodynamically stable, like opposing domains on a ferromagnetic surface, like a hard drive.
Hard drives wont to spontaneously erase themselves to 'all zero' over human lifetimes.
The global lowest energy state is "all spins pointing the same way".
I disagree. "Writing software properly" apparently means taking on a huge burden for simple operations.
Quoting T'so:
"The final solution, is we need properly written applications and desktop libraries. The proper way of doing this sort of thing is not to have hundreds of tiny files in private ~/.gnome2* and ~/.kde2* directories. Instead, the answer is to use a proper small database like sqllite for application registries, but fixed up so that it allocates and releases space for its database in chunks, and that it uses fdatawrite() instead of fsync() to guarantee that data is written on disk. If sqllite had been properly written so that it grabbed new space for its database storage in chunks of 16k or 64k, and released space when it was no longer needed in similar large chunks via truncate(), and if it used fdatasync() instead of fsync(), the performance problems with FireFox 3 wouldn't have taken place."
In other words, if the programmer took on the burden of tons of work and complexity in order to replicate lots of the functionality of the file system and make it not the file system's problem, then it wouldn't be my problem.
I personally think it should be perfectly OK to read and write hundreds of tiny files. Even thousands.
File systems are nice. That's what Unix is about.
I don't think programmers ought to be required to treat them like a pouty flake: "in some cases, depending on the whims of the kernel and entirely invisible moods, or the way the disk is mounted that you have no control over, stuff might or might not work."
Pure science wouldn't ever get that large amount of funding (at least in the USA---CERN is the one worldwide exception, as that is pure science).
Most of of the scientific results from NIF will have only one value: designing and maintaining thermonuclear weapons.
And those that don't, are very "dual-use" so they will be nearly as classified as results from actual nuclear weapons tests.
Nuclear experiments in 1855? Surely you joke. Nobody in 1855 knew what a nucleus was, or was even convinced about the atomic theory of matter.
In fact, nuclear fission was discovered in 1938, and large scale full production systems were operating by 1945 (Hanford), with commercial utility turn-on by mid 1950's.
Nuclear fusion was discovered in early 30's, I think, before fission.
The reason why nuclear fission went from discovery to exploitation immediately, and fusion is still really hard, is due to the laws of physics.
Specifically:
1) neutrons have charge zero, but nuclei don't.
2) strong force is very short range
These will never change.
And yes, the original poster is right, NIF isn't helping much for energy production.
I think LIFE is merely the political cover story.
Fission/fusion hybrids and burning actinides are stupendously good ideas.
But why a complex ICF with so many fundamental engineering issues in the way (fuel delivery, cycling drive)----instead of the ICF in the middle, a continuously operating tokamak or whatever can provide, today, squillions of fast neutrons. There are problems making it substantially over unity electrical output versus input but if you let the fission take care of the energy production, magnetic confinement reactors are generations ahead of ICF in producing massive neutron fluxes.
Fueling and drive are far easier (i.e. gas transfer and microwave magnetrons, 1940's technology) than yet to be mastered ICF technology.
"The only ones that come close in ability to provide a large amount of energy are fission and solar, and they have the disadvantages, respectively, of long-lived actinide waste, and massive land use."
Long-lived actinide waste is not an immutable issue with nuclear fission.
Nearly all of the long-lived actinide waste can be burnt up by fast neutrons, whether from fission reactors, fusion reactors or particle accelerators.
The physics is known, but the engineering details (i.e. what makes the most sense given $$$$) aren't yet.
On the other hand, massive land use and capital costs are immutable problems with solar because of the energy density of the solar flux at the Earth's surface.
Apologies for the self followup, but the evidence for the above is publicly available:
"NIF is a program of the U.S. Department of Energy's National Nuclear Security Administration. "
https://lasers.llnl.gov/
NNSA is the section of DOE which operates the production and analysis of nuclear weapons.
Unfortunately, National Ignition Facility has nothing to do with energy production and everything to do with nuclear weaponry.
In reality, it is a physical simulation of the tough part of nuclear weapons design, the transfer of photon radiation to the thermonuclear secondary. There are extremely complex and exotic fluid dynamics. These results are used to calibrate the simulation codes for nuclear weapons, which are all about thermodynamics & radiation transfer, and not about nuclear physics.
For energy production research they probably wouldn't have used lasers (far too inefficient vs charged particle beams, but particle beams create less weapon-like conditions) and would have concentrated far more on the engineering aspects of power production.
The even sadder reality is that if it had been designed for energy production research it would never have been funded.
"I don't see any problem with the leaders of North Korea or Iran deciding that 80% of their population had to be sacrificed. I think that is a decision they could easily make. So MAD doesn't work for them at all."
North Korea's leaders might be happy with sacrificing 80% of its population, but only if they got to choose, as they usually do on such matters.
Fallout patterns might not be so agreeable.
"Air-burst nukes are already relatively clean."
This isn't true any more---since probably mid 60's 70's.
Most modern nuclear weapons (e.g. those deployed by the USA), gain a major fraction of their design yield from fission of U-238 in the secondary, maybe 50%.
The actual push for 'clean' weapons stopped after above-ground tests were eliminated by treaty.
A significant amount of the dangerous fallout is direct fission products and remnants of the warhead case itself. The fallout for a modern 400kt warhead would be say 15-20x that of Nagasaki, as you have 200kt of fission product vs 10kt.
Yes, a dozen or two kg of fully fissioned uranium (modern weapons get probably 80% of the potential nuclear energy from fission & fusion fuel) really does make a huge load of nasty fallout.
Working together in some bloated international bureaucracy got us the ISS. The competitive race approach and twenty times the money got us Apollo.
Fixed that for you.