Well, going with NiMH instead of NiCad would be a good idea, however LiIons don't handle high-discharge loads nearly as well as NiCads.
You don't have a very serious weight limit in this thing - put in a small lead/acid gel cell. That might even give you a long enough lifetime to be useful.
Isn't there another problem: it would not clean the middle of the room. The turning is triggered when it hits obstacles. Thus, it'd turn only as long as it hasn't re-oriented itself enough that it can pass the obstacle: result: you set it into the middle of the room, it heads straight to a wall, and from then on follows the walls in a circular motion around the room, leaving the middle of the room uncleaned... Or did I miss something here?
Depends on how it re-orients itself. If you can get it to bounce, as opposed to just track the wall, it'll make random passes across the room. You could do this by putting a spring and a friction mount on the rotating drive unit.
Your DNA will become increasingly damaged. Cancer will run rampant. We'll have drugs by then to keep the cancer down, but eventually your DNA will look like swiss cheese. You can't fix that, unless you can some how store a copy of your DNA somewhere with 0 radiation and copy from that on a regular basis. Failing that, you'll live to turn into a giant sack of tumors. We already know that everything (even celery) gives you cancer.
Bacteria seem to manage maintaining genetic integrity just fine. Sure, out of any population of cells, you'll get mutants, but if you can prune them, cells with intact genetic material will reproduce to fill the void.
You have the same thing happening in humans - the genetic material you pass on to your offspring was passed to you from your parents, and to them from their parents, and so forth. If nothing can compensate for mutation, then humans should have died out long ago.
The key is to actively maintain the collective quality of your genetic material by recognizing and discarding mutated DNA. There are several mechanisms in place which do this already.
I don't believe it. We are carbon based beings. Carbon eventually deteriorates(sp?).
I read once where silicon has a similar molecular structure like carbon and we were silicon based then we could live MUCH longer.
How do they go about maintaining the carbon in our bodies?
Simple carbon compounds will last indefinitely. Complex carbon compounds won't. The same applies to silicon or any other element you want to build people out of. Think of this as an effect of entropy, if you like.
You keep a person healthy forever the same way you keep a bridge in operation forever - by repairing and maintaining it.
The body's self-repair systems are good, but not good enough for an indefinite lifespan, and some parts of the body's construction were just not designed for indefinite maintenance (the lens in your eye is a good example). In order to give people a very long lifespan, we're going to have to change and extend our self-repair mechanisms to handle the problems that they miss at present, and unless we want to act out Gulliver's Travels a little too well, we're going to have to tweak our body structure too so that all parts can be maintained indefinitely (unless we want regular surgery to replace bits that stop working).
I personally think we'll achieve immortality by porting ourselves to computer systems before we solve all of the problems of biological immortality, but that's by no means a foregone conlcusion.
In summary, longevity and aging work considerably differently than you seem to be assuming.
That has to be the saddest attempt at making a competing product. It uses nothing besides some gears to move around obstacles (no circuitry), uses wipes to clean floor (which don't work well according to website author, says it barely picks up dirt and it only does on the front of wipe), moves slowly, and obviously can't clean anything besides smooth surfaces. Is there a lamest products ever list? This really deserves it.
The thing that gives me pause is that something like this could actually work, if you tweak the undercarriage to solve the "pushing dust in front" problem.
Will it clean an area as quickly as an intelligent, microprocessor-driven cleaning robot? Of course not.
What it _will_ do is random-walk all over my kitchen sweeping up dust overnight. At that price, it might even be worth it (as long as the batteries hold out; kitbashing a gel cell into it might be worthwhile).
Just because a design's simple doesn't mean it's worthless. An inefficient but cheap solution has its place.
your last statement is wrong. I don't recall any such strict condition on particle creation. Here's an example: neutron decays into a proton, an electron, and an antineutrino. No positron. Of course, I could be wrong
The "electron number" is conserved. The electron and electron neutrino have an electron number of 1, while the positron and the electron antineutrino have an electron number of -1. This is why beta decay produces the antineutrino.
A dupe bug would bring the economics of such a system crashing down.
The advantage to a system where in-game objects don't have (recognized) real value is that bugs aren't lethal to the parent company, and the game can be revised and the game database directly edited with impunity.
Make money in the game real, and suddenly the parent company has to be a lot more careful, and is a lot more liable if things go wrong (as actual damage has provably occurred to the players).
Rather than assuming some bizarre physics of gravitons where they pull something they ram into, why not take a simpler approach and assume that they push things along, just like a baseball and the milk bottle at the faire?
You appear to be using an overly-simplistic model of what force-carrying particles are.
The classical model of force involves "fields" - continuous distributions of force about their sources (e.g. an electric field that varies as the inverse square of distance from an object with charge, or a gravitational field that varies as the inverse square of distance from an object with mass).
When quantum mechanics came along, it was realized that these fields weren't continuous in all senses - disturbances in the field could only come in discrete packets. These are the force-carrying particles.
A graviton doesn't "ram into" anything. It's a moving ripple in the gravitational field of an object. The net effect of all gravitons (real and virtual) about an object with mass is to produce an attractive force on other massive objects nearby.
Similarly, a photon is a moving ripple in the electromagnetic field, with the net effect of all of the virtual photons in the vicinity of a charged object being to attract or repel other charged objects in the area.
The properties of gravitons are less certain, because it's hard to build a quantized version of Einsteinian gravity, but this is the general idea behind force-carrying particles (in force-carrying contexts, they can be thought of as the minimum (quantized) disturbance of a classical-looking field of force).
I'm no Tolkein expert, but can anyone tell me if "runes" here correspond to the actual, real world runes, that is, letters of the ancient Runic alphabet?
The runes used on the map in "The Hobbit" did use the real runic alphabet (or a close variant thereof). The Cirth described in the appendices of LOTR was comletely different, however. So the official answer is probably "no".
Firstly, you apparently have been misinformed about the definition of the word "theory".
No, I'm not. I'm simply using the colloquial form, which is neither more nor less correct than the scientific in this sense.
This is a scientific discussion. You were gratuitously abusing the term to make an argument-by-belittlement against cosmological models (which is pretty ironic given that you were trying to _support_ one).
Proposing larger spaces for embedding as a mathematical crutch is fine as long as they don't have a material effect on the observable universe, but if there's a fourth spatial direction that forces can propagate in, why do we only observe three directions?
For the same reason that we don't normally percieve the motion of our system through the galaxy, or our galaxy through the universe? We may simply not be looking in the right place, or not have been looking for a long enough time.
Different beasts - the model you favour assumes as an axiom that forces act in the extra direction. This would cause very visible effects. _Really_ visible effects - the most obvious of which being the propagation of matter through all available spatial directions unless some magical force acted to confine it.
Secondly, the motion of the stars within our galaxy is very visible as soon as you start taking spectra of stars. Likewise, the movement of our galaxy relative to the cosmic microwave background is very visible as soon as you can see the cosmic microwave background at all.
There is another very visible effect - the gravitational impact of dark matter - that this multiple membrane model is trying to explain, and is taking as part of the primary evidence for its correctness. However, the multiple membrane model requires an extra hypothesis - something enforcing confinement to a membrane despite forces acting to the contrary - while the more conventional dark matter models do not require extra hypothesis (we've seen neutrinos, and have substantial circumstantial evidence in particle physics for supersymmetric particles existing).
In summary, the model you are trying to defend has no mechanism for justifying the very unusual modifications it needs just to be compatible with _existing_ experimental evidence.
Conjecturing about the basic construction of our (immediate) cosmos is a great thing--but the further out a theorist gets, the more arrogant the assumption of knowledge is.
This is why you are actively supporting a model that makes more assumptions than usual?
Actually, the outstanding question is whether or not neutrinos have mass. If they do, then the need for Dark Matter[tm] goes away. If they don't, we still have brown dwarf stars, undiscovered planets, and the effects of elector-magnetic currents on stars still not quite 100% accounted for within the current cosmological model.
Dark Matter, as an esoteric, non-euclidian form of matter, is still, IMO, nothing more than the late 20th century equivalent of the luminiferous aether of the 19th century, and merely a convenient algorythmic placeholder, until proven otherwise.
Actually, things turn out to work a little differently.
First of all, neutrino oscillation experiments confirm pretty convincingly that neutrinos do have mass. Rough bounds on the amount of mass have already been placed. The best numbers to date say that massive neutrinos can account for some, but far from all, of the dark matter effects observed.
Second of all, brown dwarfs and other "massive compact halo objects" would be baryonic dark matter - and there are good arguments for most of the dark matter being non-baryonic. A summary of some of these arguments can be found here (it's multiple pages; follow the links).
Third of all, I have not heard a convincing argument that EM effects in stars relate to the dark matter problem. There is one reseaercher who keeps publishing papers about the galaxy acting as a dynamo, with large-scale EM effects determining structure, but many holes have been poked in this proposed model (a few came up in previous slashot articles).
There are some questions about the galactic magnetic field (why it has one as strong as it does, if I recall correctly), but the observed field has negligeable effect on the movements of stars within the galaxy.
In summary, there really does seem to be some kind of exotic dark matter present in large quantity, and we already have several candidates for components of it.
While it's common to call the universe "everything," it's really just "everything we can sense or extrapolate." There very very well might be a much much larger "macroverse" out there--but to get to this point, we're firmly out of science (which is a search for knowledge) and into theory--also known as "religion", "dreaming", and "half-assed speculation."
Firstly, you apparently have been misinformed about the definition of the word "theory". An idea that is proposed without evidence is a "conjecture". An idea that matches a lot of the available information and has no major contradictions with observations - in other words, a plausible conjecture - is a "hypothesis". To change categories a bit, a "model" is a set of equations that attempts to accurately describe the behavior of some apsect of the universe. They are often the subject of hypotheses - e.g., you could hypothesize that the "whimper version 3" model is an accurate description of the universe. The model and the hypothesis are two different types of object.
A "theory" is the last hypothesis standing after all hypothesis have been subjected to very rigorous experimental tests. If after every attempt you can make to tear it down, a given hypothesis remains the best explanation available for a phenomenon or set of observations, then it graduates to the "theory" category.
Calling "half-assed speculation" "theory" or vice-versa is very far from correct.
Now, on to the multiple membranes model. The main problem I have with it is that it supposes some higher-dimensional space in which the membranes are embedded, and supposes that interaction can occur through this space. Proposing larger spaces for embedding as a mathematical crutch is fine as long as they don't have a material effect on the observable universe, but if there's a fourth spatial direction that forces can propagate in, why do we only observe three directions? If things can be pulled and pushed across this gap, why don't particles and stars and whatnot move freely in this direction? What forces them to be bound into membranes?
This model makes a number of propositions along these lines for which simpler alternate explanations exist (e.g. for dark matter, that there are enough particles present that don't interact via EM to have substantial gravitational effect - we already have several candidates for part of this detected by other methods [the neutrino flavours]).
As far as I can tell, this multiple-membrane model gets attention because of similarities in name (and only name) to the "brane" model for superstrings (which proposes that particles are p-dimensional membranes instead of one-dimensional objects). The superstring / brane models avoid the observational problems of extra spatial dimensions by making them too small to have impact on the macroscopic world (and their microscopic impact is exactly that required to make vibrating string modes match up with the particles we observe). Completely different beasts.
Isn't the use of ugly hacks to prop up an established theory in the face of contradictory observations an indicator of a theory which needs to be chucked out en masse and reformulated in the light of a more fundamental description of physics?
Sort of.
It's actually an indication that a better model _might_ exist.
Until we have a model in-hand that works at least as well as the current one, however, there's no justification for throwing out the current model (which still works quite well as an approximation). So, calling for the current model of the universe to be chucked is a bit premature.
Another possibility is that several fundamental parameters of the universe _do_ vary with time, as a result of some mechanism which has not yet been discovered. Constants that cannot be derived from other constants and are instead set at arbitrary values are just as suspicious as "constants" that change.
So, which end are we certain will happen now - or rather, which end is the author hyping, since most scientists would still be reluctant to call this an open and shut case?
Possible scenarios include:
The Big Crunch
This fell out of favour a while back, when the need for a flat universe became apparent. In this scenario, the universe's espansion halts and it re-collapses. Once it was thought that this would involve time running backwards/entropy reversal during the crunch phase, but it was later shown that scenarios with increasing entropy also existed. There was much speculation about whether the universe would "bounce" after it crunched, forming a new expanding universe.
The Whimper, Version 1
This scenario was popular when we'd made a detailed enough survey to know that that amount of bright matter in the universe was far too low to counteract the expansion. It fell out of favour when our estimates of the amount of dark matter got better.
In this scenario, the universe keeps expanding quickly, and all matter that isn't gravitationally bound into clusters is separated by vast empty regions of space. As the universe's expansion represents the expansion of space itself, sufficiently large gravitationally bound clusters might still be disrupted, due to distances changing internally. Galaxies burn out as stars exhaust their fuel, stellar corpses eventually merge with each other and with the central black hole, which finally decays after a mind-bogglingly huge length of time.
The Flat Whimper (Version 2)
This scenario assumes that the amount of matter - light and dark - is perfectly balanced with the expansion of the universe. There was strong circumstantial evidence for a scenario like this, due to the fact that deviations from flatness amplify over time and that our universe was still _roughly_ flat - but the linchpin was a variety of models for the early universe - and the big bang - that required the universe to be flat. More detailed measurements of the amount of dark matter in the universe seemed to be consistent with this model.
In this scenario, the rate of expansion slows, approaching zero as time goes to infinity. Distance still goes to infinity as time goes to infinity, but not as rapidly. From a local point of view this looks a lot like Whimper Version 1.
Whimper Version 3 - We're Expanding Again
This model arose when evidence for dark energy was discovered by observations of distant parts of the universe. In this model, the universe started out as flat, but a weak repulsive effect comes into play that causes expansion to accelerate. The effect is small enough that we haven't diverged that greatly from flatness yet, but in the end, it'll be Whimper Version 1 all over again. This is one of the two currently plausible scenarios.
The Never-Ending Fractal Universe (Steady-State Reborn)
This model was the result of closer examination of the scalar field models used to drive inflation in the early universe. In the inflationary model - which itself was proposed to solve the problem of the universe's matter distribution being so smooth - a "scalar field" existed in the early universe that permeated space and caused vast amounts of new space to be created. In the original version of the inflationary model, this scalar field's effects died out shortly after the big bang. A later model, however, proposed that the field was not cancelled everywhere - in some regions of the universe, constructive interference would cause it to be strong enough for inflation to continue.
Thus, we have a model where the universe looks mostly like our own, except for regions where it "buds" to form new universes. This process continues forever. This is the second scenario currently considered plausible (with the scalar field taking on the role of "dark energy").
The spin in the article is misleading. What's actually happening is that the interaction cross-section between electron and neutron beams and the hydrogen in water (and in things like hexane) is lower than expected relative to the interaction cross-section with oxygen or carbon.
The conjecture about why the phenomenon occurs (entanglement of protons) is interesting, but they're going to need to find a plausible mechanism and confirm that it's happening before we really know what's going on.
Isn't this the same Steve Bennett who was planning to launch his X-prize rocket on what amounted to the same kind of engines used by the high-power model rocket community, despite the community trying to tell him that they wouldn't scale the way he wants them to? The guy who was prevented from doing further launch tests because he set the firing range he was using on fire? The guy who was ripped apart in the last three articles about him for not having an adequate understanding of what he's doing?
This does not bode well for his scheduled launch attempt.
So...were you successful in your brute-force of the Rubik's Cube? (aka Continuum Transfunctioner?)
No, which is puzzling, because it was the 2x2x2 cube, which only has about 10 million combinations (once rotations are removed). If the network of cube states has no special properties, it should take 13-15 moves to reach any possible state. I did exhaustive searches to about 21 moves, and randomized searches much deeper than that (deep enough that even if the state graph had peculiar properties, a solution should have been found).
There's obviously a bug in the program, but I haven't tracked it down yet.
And before anyone mentions that it would take less time just to look up how to solve the cube, I wrote the program for the fun of it:). I'm also trying to figure out solution techniques without looking at a cheat sheet, which is easier if I can get the cube back to a pristine starting position.
The only problem is that these "dragon chips" are about equivilent to your average pentium 2, they can't hold a candle to anything coming out of the united states. This chip may work for webstation-type things, but it will be useless for any real computing.
Unless you're doing computational fluid dynamics as your day job, you don't need a computer _even_ as fast as this.
The vast majority of computers are used for general office work. Aren't the *nix advocates the ones who have been saying that they could do on their 386s what the dx2-66/Windows crowd was doing, all of those years ago?
I do the majority of my computing on a Celeron 366. The only time I noticed slowdown on it was when I tried to brute-borce solve a Rubik's Cube.
China gets a chip that satisfies most of their needs, and can use a simple and robust architecture and implementation and save a bundle on development time. Sounds good to me.
The only thing that I'm having trouble with is the microwave background radiation. Light and matter decoupled when the universe was extremely compact - the parts emitting the background radiation we see would have been very close indeed to our location. Space must have been growing fast enough for points this close to still be moving apart at or very close to the speed of light.
Inflation stopped long before this, so it doesn't help.
On reflection, the relation you provided does give an expansion velocity between any two points that tends towards infinity as time tends towards zero. It's just a change in how I'd viewed the early universe.
Slashdot Mirror
Well, going with NiMH instead of NiCad would be a good idea, however LiIons don't handle high-discharge loads nearly as well as NiCads.
You don't have a very serious weight limit in this thing - put in a small lead/acid gel cell. That might even give you a long enough lifetime to be useful.
Isn't there another problem: it would not clean the middle of the room. The turning is triggered when it hits obstacles. Thus, it'd turn only as long as it hasn't re-oriented itself enough that it can pass the obstacle: result: you set it into the middle of the room, it heads straight to a wall, and from then on follows the walls in a circular motion around the room, leaving the middle of the room uncleaned... Or did I miss something here?
Depends on how it re-orients itself. If you can get it to bounce, as opposed to just track the wall, it'll make random passes across the room. You could do this by putting a spring and a friction mount on the rotating drive unit.
Your DNA will become increasingly damaged. Cancer will run rampant. We'll have drugs by then to keep the cancer down, but eventually your DNA will look like swiss cheese. You can't fix that, unless you can some how store a copy of your DNA somewhere with 0 radiation and copy from that on a regular basis. Failing that, you'll live to turn into a giant sack of tumors. We already know that everything (even celery) gives you cancer.
Bacteria seem to manage maintaining genetic integrity just fine. Sure, out of any population of cells, you'll get mutants, but if you can prune them, cells with intact genetic material will reproduce to fill the void.
You have the same thing happening in humans - the genetic material you pass on to your offspring was passed to you from your parents, and to them from their parents, and so forth. If nothing can compensate for mutation, then humans should have died out long ago.
The key is to actively maintain the collective quality of your genetic material by recognizing and discarding mutated DNA. There are several mechanisms in place which do this already.
I don't believe it. We are carbon based beings. Carbon eventually deteriorates(sp?).
I read once where silicon has a similar molecular structure like carbon and we were silicon based then we could live MUCH longer.
How do they go about maintaining the carbon in our bodies?
Simple carbon compounds will last indefinitely. Complex carbon compounds won't. The same applies to silicon or any other element you want to build people out of. Think of this as an effect of entropy, if you like.
You keep a person healthy forever the same way you keep a bridge in operation forever - by repairing and maintaining it.
The body's self-repair systems are good, but not good enough for an indefinite lifespan, and some parts of the body's construction were just not designed for indefinite maintenance (the lens in your eye is a good example). In order to give people a very long lifespan, we're going to have to change and extend our self-repair mechanisms to handle the problems that they miss at present, and unless we want to act out Gulliver's Travels a little too well, we're going to have to tweak our body structure too so that all parts can be maintained indefinitely (unless we want regular surgery to replace bits that stop working).
I personally think we'll achieve immortality by porting ourselves to computer systems before we solve all of the problems of biological immortality, but that's by no means a foregone conlcusion.
In summary, longevity and aging work considerably differently than you seem to be assuming.
That has to be the saddest attempt at making a competing product. It uses nothing besides some gears to move around obstacles (no circuitry), uses wipes to clean floor (which don't work well according to website author, says it barely picks up dirt and it only does on the front of wipe), moves slowly, and obviously can't clean anything besides smooth surfaces. Is there a lamest products ever list? This really deserves it.
The thing that gives me pause is that something like this could actually work, if you tweak the undercarriage to solve the "pushing dust in front" problem.
Will it clean an area as quickly as an intelligent, microprocessor-driven cleaning robot? Of course not.
What it _will_ do is random-walk all over my kitchen sweeping up dust overnight. At that price, it might even be worth it (as long as the batteries hold out; kitbashing a gel cell into it might be worthwhile).
Just because a design's simple doesn't mean it's worthless. An inefficient but cheap solution has its place.
your last statement is wrong. I don't recall any such strict condition on particle creation. Here's an example: neutron decays into a proton, an electron, and an antineutrino. No positron. Of course, I could be wrong
The "electron number" is conserved. The electron and electron neutrino have an electron number of 1, while the positron and the electron antineutrino have an electron number of -1. This is why beta decay produces the antineutrino.
A dupe bug would bring the economics of such a system crashing down.
The advantage to a system where in-game objects don't have (recognized) real value is that bugs aren't lethal to the parent company, and the game can be revised and the game database directly edited with impunity.
Make money in the game real, and suddenly the parent company has to be a lot more careful, and is a lot more liable if things go wrong (as actual damage has provably occurred to the players).
Rather than assuming some bizarre physics of gravitons where they pull something they ram into, why not take a simpler approach and assume that they push things along, just like a baseball and the milk bottle at the faire?
You appear to be using an overly-simplistic model of what force-carrying particles are.
The classical model of force involves "fields" - continuous distributions of force about their sources (e.g. an electric field that varies as the inverse square of distance from an object with charge, or a gravitational field that varies as the inverse square of distance from an object with mass).
When quantum mechanics came along, it was realized that these fields weren't continuous in all senses - disturbances in the field could only come in discrete packets. These are the force-carrying particles.
A graviton doesn't "ram into" anything. It's a moving ripple in the gravitational field of an object. The net effect of all gravitons (real and virtual) about an object with mass is to produce an attractive force on other massive objects nearby.
Similarly, a photon is a moving ripple in the electromagnetic field, with the net effect of all of the virtual photons in the vicinity of a charged object being to attract or repel other charged objects in the area.
The properties of gravitons are less certain, because it's hard to build a quantized version of Einsteinian gravity, but this is the general idea behind force-carrying particles (in force-carrying contexts, they can be thought of as the minimum (quantized) disturbance of a classical-looking field of force).
Well here's one possibility. If that's possible, anything is.
See my previous messags on this topic in the "end of the universe" article (click on my user info).
Summary: This makes improbable assumptions. When most physicists talk about "brane theory", they mean something else (a variant of string theory).
I'm no Tolkein expert, but can anyone tell me if "runes" here correspond to the actual, real world runes, that is, letters of the ancient Runic alphabet?
The runes used on the map in "The Hobbit" did use the real runic alphabet (or a close variant thereof). The Cirth described in the appendices of LOTR was comletely different, however. So the official answer is probably "no".
Firstly, you apparently have been misinformed about the definition of the word "theory".
No, I'm not. I'm simply using the colloquial form, which is neither more nor less correct than the scientific in this sense.
This is a scientific discussion. You were gratuitously abusing the term to make an argument-by-belittlement against cosmological models (which is pretty ironic given that you were trying to _support_ one).
Proposing larger spaces for embedding as a mathematical crutch is fine as long as they don't have a material effect on the observable universe, but if there's a fourth spatial direction that forces can propagate in, why do we only observe three directions?
For the same reason that we don't normally percieve the motion of our system through the galaxy, or our galaxy through the universe? We may simply not be looking in the right place, or not have been looking for a long enough time.
Different beasts - the model you favour assumes as an axiom that forces act in the extra direction. This would cause very visible effects. _Really_ visible effects - the most obvious of which being the propagation of matter through all available spatial directions unless some magical force acted to confine it.
Secondly, the motion of the stars within our galaxy is very visible as soon as you start taking spectra of stars. Likewise, the movement of our galaxy relative to the cosmic microwave background is very visible as soon as you can see the cosmic microwave background at all.
There is another very visible effect - the gravitational impact of dark matter - that this multiple membrane model is trying to explain, and is taking as part of the primary evidence for its correctness. However, the multiple membrane model requires an extra hypothesis - something enforcing confinement to a membrane despite forces acting to the contrary - while the more conventional dark matter models do not require extra hypothesis (we've seen neutrinos, and have substantial circumstantial evidence in particle physics for supersymmetric particles existing).
In summary, the model you are trying to defend has no mechanism for justifying the very unusual modifications it needs just to be compatible with _existing_ experimental evidence.
Conjecturing about the basic construction of our (immediate) cosmos is a great thing--but the further out a theorist gets, the more arrogant the assumption of knowledge is.
This is why you are actively supporting a model that makes more assumptions than usual?
Actually, the outstanding question is whether or not neutrinos have mass. If they do, then the need for Dark Matter[tm] goes away. If they don't, we still have brown dwarf stars, undiscovered planets, and the effects of elector-magnetic currents on stars still not quite 100% accounted for within the current cosmological model.
Dark Matter, as an esoteric, non-euclidian form of matter, is still, IMO, nothing more than the late 20th century equivalent of the luminiferous aether of the 19th century, and merely a convenient algorythmic placeholder, until proven otherwise.
Actually, things turn out to work a little differently.
First of all, neutrino oscillation experiments confirm pretty convincingly that neutrinos do have mass. Rough bounds on the amount of mass have already been placed. The best numbers to date say that massive neutrinos can account for some, but far from all, of the dark matter effects observed.
Second of all, brown dwarfs and other "massive compact halo objects" would be baryonic dark matter - and there are good arguments for most of the dark matter being non-baryonic. A summary of some of these arguments can be found here (it's multiple pages; follow the links).
Third of all, I have not heard a convincing argument that EM effects in stars relate to the dark matter problem. There is one reseaercher who keeps publishing papers about the galaxy acting as a dynamo, with large-scale EM effects determining structure, but many holes have been poked in this proposed model (a few came up in previous slashot articles).
There are some questions about the galactic magnetic field (why it has one as strong as it does, if I recall correctly), but the observed field has negligeable effect on the movements of stars within the galaxy.
In summary, there really does seem to be some kind of exotic dark matter present in large quantity, and we already have several candidates for components of it.
Actually, that makes the most logical sense.
While it's common to call the universe "everything," it's really just "everything we can sense or extrapolate." There very very well might be a much much larger "macroverse" out there--but to get to this point, we're firmly out of science (which is a search for knowledge) and into theory--also known as "religion", "dreaming", and "half-assed speculation."
Firstly, you apparently have been misinformed about the definition of the word "theory". An idea that is proposed without evidence is a "conjecture". An idea that matches a lot of the available information and has no major contradictions with observations - in other words, a plausible conjecture - is a "hypothesis". To change categories a bit, a "model" is a set of equations that attempts to accurately describe the behavior of some apsect of the universe. They are often the subject of hypotheses - e.g., you could hypothesize that the "whimper version 3" model is an accurate description of the universe. The model and the hypothesis are two different types of object.
A "theory" is the last hypothesis standing after all hypothesis have been subjected to very rigorous experimental tests. If after every attempt you can make to tear it down, a given hypothesis remains the best explanation available for a phenomenon or set of observations, then it graduates to the "theory" category.
Calling "half-assed speculation" "theory" or vice-versa is very far from correct.
Now, on to the multiple membranes model. The main problem I have with it is that it supposes some higher-dimensional space in which the membranes are embedded, and supposes that interaction can occur through this space. Proposing larger spaces for embedding as a mathematical crutch is fine as long as they don't have a material effect on the observable universe, but if there's a fourth spatial direction that forces can propagate in, why do we only observe three directions? If things can be pulled and pushed across this gap, why don't particles and stars and whatnot move freely in this direction? What forces them to be bound into membranes?
This model makes a number of propositions along these lines for which simpler alternate explanations exist (e.g. for dark matter, that there are enough particles present that don't interact via EM to have substantial gravitational effect - we already have several candidates for part of this detected by other methods [the neutrino flavours]).
As far as I can tell, this multiple-membrane model gets attention because of similarities in name (and only name) to the "brane" model for superstrings (which proposes that particles are p-dimensional membranes instead of one-dimensional objects). The superstring / brane models avoid the observational problems of extra spatial dimensions by making them too small to have impact on the macroscopic world (and their microscopic impact is exactly that required to make vibrating string modes match up with the particles we observe). Completely different beasts.
Isn't the use of ugly hacks to prop up an established theory in the face of contradictory observations an indicator of a theory which needs to be chucked out en masse and reformulated in the light of a more fundamental description of physics?
Sort of.
It's actually an indication that a better model _might_ exist.
Until we have a model in-hand that works at least as well as the current one, however, there's no justification for throwing out the current model (which still works quite well as an approximation). So, calling for the current model of the universe to be chucked is a bit premature.
Another possibility is that several fundamental parameters of the universe _do_ vary with time, as a result of some mechanism which has not yet been discovered. Constants that cannot be derived from other constants and are instead set at arbitrary values are just as suspicious as "constants" that change.
Possible scenarios include:
This fell out of favour a while back, when the need for a flat universe became apparent. In this scenario, the universe's espansion halts and it re-collapses. Once it was thought that this would involve time running backwards/entropy reversal during the crunch phase, but it was later shown that scenarios with increasing entropy also existed. There was much speculation about whether the universe would "bounce" after it crunched, forming a new expanding universe.
This scenario was popular when we'd made a detailed enough survey to know that that amount of bright matter in the universe was far too low to counteract the expansion. It fell out of favour when our estimates of the amount of dark matter got better.
In this scenario, the universe keeps expanding quickly, and all matter that isn't gravitationally bound into clusters is separated by vast empty regions of space. As the universe's expansion represents the expansion of space itself, sufficiently large gravitationally bound clusters might still be disrupted, due to distances changing internally. Galaxies burn out as stars exhaust their fuel, stellar corpses eventually merge with each other and with the central black hole, which finally decays after a mind-bogglingly huge length of time.
This scenario assumes that the amount of matter - light and dark - is perfectly balanced with the expansion of the universe. There was strong circumstantial evidence for a scenario like this, due to the fact that deviations from flatness amplify over time and that our universe was still _roughly_ flat - but the linchpin was a variety of models for the early universe - and the big bang - that required the universe to be flat. More detailed measurements of the amount of dark matter in the universe seemed to be consistent with this model.
In this scenario, the rate of expansion slows, approaching zero as time goes to infinity. Distance still goes to infinity as time goes to infinity, but not as rapidly. From a local point of view this looks a lot like Whimper Version 1.
This model arose when evidence for dark energy was discovered by observations of distant parts of the universe. In this model, the universe started out as flat, but a weak repulsive effect comes into play that causes expansion to accelerate. The effect is small enough that we haven't diverged that greatly from flatness yet, but in the end, it'll be Whimper Version 1 all over again. This is one of the two currently plausible scenarios.
This model was the result of closer examination of the scalar field models used to drive inflation in the early universe. In the inflationary model - which itself was proposed to solve the problem of the universe's matter distribution being so smooth - a "scalar field" existed in the early universe that permeated space and caused vast amounts of new space to be created. In the original version of the inflationary model, this scalar field's effects died out shortly after the big bang. A later model, however, proposed that the field was not cancelled everywhere - in some regions of the universe, constructive interference would cause it to be strong enough for inflation to continue.
Thus, we have a model where the universe looks mostly like our own, except for regions where it "buds" to form new universes. This process continues forever. This is the second scenario currently considered plausible (with the scalar field taking on the role of "dark energy").
This is the model proposed by
(and in things like hexane)
Whoops; they used benzene, not hexane, for the hydrocarbon test. My bad.
The spin in the article is misleading. What's actually happening is that the interaction cross-section between electron and neutron beams and the hydrogen in water (and in things like hexane) is lower than expected relative to the interaction cross-section with oxygen or carbon.
The conjecture about why the phenomenon occurs (entanglement of protons) is interesting, but they're going to need to find a plausible mechanism and confirm that it's happening before we really know what's going on.
I'd thought the name sounded familiar.
Isn't this the same Steve Bennett who was planning to launch his X-prize rocket on what amounted to the same kind of engines used by the high-power model rocket community, despite the community trying to tell him that they wouldn't scale the way he wants them to? The guy who was prevented from doing further launch tests because he set the firing range he was using on fire? The guy who was ripped apart in the last three articles about him for not having an adequate understanding of what he's doing?
This does not bode well for his scheduled launch attempt.
I doubt the use is heavy enough for maintainance to be a big issue.
Weather's a big issue. Even pressure-treated lumber wears in an annoyingly short time. The rails will also corrode.
It's a great achievement, but if its time before a major overhaul is needed is over 10 years, I'll be impressed - and this took years to build.
As long as he puts in the time, kudos to him.
So...were you successful in your brute-force of the Rubik's Cube? (aka Continuum Transfunctioner?)
:). I'm also trying to figure out solution techniques without looking at a cheat sheet, which is easier if I can get the cube back to a pristine starting position.
No, which is puzzling, because it was the 2x2x2 cube, which only has about 10 million combinations (once rotations are removed). If the network of cube states has no special properties, it should take 13-15 moves to reach any possible state. I did exhaustive searches to about 21 moves, and randomized searches much deeper than that (deep enough that even if the state graph had peculiar properties, a solution should have been found).
There's obviously a bug in the program, but I haven't tracked it down yet.
And before anyone mentions that it would take less time just to look up how to solve the cube, I wrote the program for the fun of it
The only problem is that these "dragon chips" are about equivilent to your average pentium 2, they can't hold a candle to anything coming out of the united states. This chip may work for webstation-type things, but it will be useless for any real computing.
Unless you're doing computational fluid dynamics as your day job, you don't need a computer _even_ as fast as this.
The vast majority of computers are used for general office work. Aren't the *nix advocates the ones who have been saying that they could do on their 386s what the dx2-66/Windows crowd was doing, all of those years ago?
I do the majority of my computing on a Celeron 366. The only time I noticed slowdown on it was when I tried to brute-borce solve a Rubik's Cube.
China gets a chip that satisfies most of their needs, and can use a simple and robust architecture and implementation and save a bundle on development time. Sounds good to me.
Ok, trivia time!
What is a google?
One followed by a hundred zeroes, as opposed to a googleplex, which is one followed by a google zeroes.
Ask me what the zeta function is, however, and I'd have to check a textbook...
Septillion
Sextillion (boys and girls like this one)
You have these two switched (sextillion comes before septillion). Hint: Count to ten in any of a variety of languages.
You do understand correctly (yay!).
The only thing that I'm having trouble with is the microwave background radiation. Light and matter decoupled when the universe was extremely compact - the parts emitting the background radiation we see would have been very close indeed to our location. Space must have been growing fast enough for points this close to still be moving apart at or very close to the speed of light.
Inflation stopped long before this, so it doesn't help.
On reflection, the relation you provided does give an expansion velocity between any two points that tends towards infinity as time tends towards zero. It's just a change in how I'd viewed the early universe.
ATI is in Markham, Ontario... just north of Toronto.
Right; I was thinking of Matrox. Sorry.