$20,000 for three months? Wow. That sure beats those cheapskates at NASA; they only spent $100 / day, or ~$9,000 for the three months.
This is indeed a generous amount. However, bear in mind that you'd also suffer fallout at work from taking a 3-month sabbatical, and you'll spend weeks regaining the ability to move or do anything strenuous for more than a few tens of minutes at a stretch.
The good news is that this still beats having to sit around in true zero-g, which would do even nastier things to your body (in bed you still have to exert effort to lift things with your hands, to roll over, to breathe (to some extent), etc.).
I've had a little bit of experience with lasers, and I'm pretty sure that the modulation required to accomplish this is going to be orders of magnitude higher than what is needed to burn data
Not really. All they're doing is taking advantage of the fact that a burned part of a CD looks noticeably different from a non-burned part, and selectively burning.
As there's a visible difference between used and unused sections on a normally-burned CD, I don't see why you'd need any special hardware to pattern this difference.
The ONE new feature I would like best on my computer is for it to know what I mean when I say "Stop! No! I didn't mean that!"
Here's a thought - imagine a system where you use journaling and checkpointing to track *all* changes to both filesystems and program states, and give the user the ability to roll back changes arbitrarily and to great distance.
This would definitely be useful in recovering from catastrophic user errors, and might even be implementable without having to rewrite every application in the universe (take an image of an application's processes' memory spaces, and either carefully note the state of all file descriptors (especially device handles), or wait until they're in a sane state before checkpointing).
One of the cluster job distribution tools I've come across already does this to some degree ("condor", which can be set up to do checkpointing if desired).
Also, there are no fixed limits on how much information you can store on hologram - you can always store something more, which will lower the quality of the rest of stored information, but you won't hit any fixed maximum number of bits, like with standard types of memory. Saying that it "[beats] out DVD by an order of magnitude" is totally ignoring the most fundamental features of holographic memory.
The problem is, if I don't care about the quality of the data retrieved, I could use/dev/null to store data and/dev/random to retrieve it and claim as much space as I want.
If you need to get your data back intact - i.e. with enough fidelity for you to rebuild the original data without loss - there turns out to be a hard limit to how much you can store with a holographic storage medium. The exact limit varies based on the geometry of the setup and of the holographic medium, but can be calculated. You can also measure it directly for any real system, which is presumably what the company involved did when citing storage densities for its prototype.
So, while the accessing method is very different, the storage limit for holograms scales in the same way as storage limits for other types of device (in this case, with the volume of the holographic film IIRC).
Take note of that third section: no nasty chemicals, they claim. If their claim holds, a company using this tech could make a lot of political capital from it.
The Princeton site makes no claim of this being a chemical-free process; all they use the imprinter for is patterning the etching resist, as an alternative to using a light-sensitive photoresist and exposing it to light and developing it to get the patterning. Under this scheme, virtually all of the nasty chemicals would still be present (you'd have a bit more flexibility in choosing resists, but that's just one set of chemicals out of a whole zoo that are needed).
The BBC report claims that patterns are directly stamped into the deposited material. This could be legit, or it could just be a misinterpretation of the resist stamping. Even if it is the patterning mechanism (i.e. if no resist or developing is needed), you still have nasty chemicals used when depositing layers of various substances on the substrate and when etching (which you'll still need to do - pure stamping will leave a thin layer of the undesired material in the stamped region even if most of it flows away).
In summary, I'd take claims of environmental friendliness with a large grain of salt.
Shoot, straight Floride gas. Mean enough to bond with most (all?) noble gases
Fluorine, and no - only Krypton and heavier. Helium, Neon, and Argon are inert enough that there are no stable compounds of them under normal conditions.
Without a really strong mechanism operating to separate it out and concentrate it, it's going to remain a trace impurity in other ores, and not a ball at the center of the Earth.
There is such a mechanism. Everyone agrees that the core is iron. How did that happen, when the Earth coalesced from random rocky materials? The same way. If iron, why not uranium?
Iron is plentiful. Enough of it was present for gross gravitational effects to be enough to separate it from lighter ores within solution.
Uranium is far, far less plentiful, and so would tend to remain dissolved.
There are no "grains" to migrate, as you suggest - uranium would be mixed in as impurities on an atomic level, literally dissolved in other metals and metal oxides.
The article proposes a 5-mile sphere of uranium at the Earth's core as the source of Earth's geothermal energy.
Now, the idea of radioactive decay powering the Earth's geothermal heat generation isn't a new one - in fact, it's one of the more plausible models, as it works quite well over a very long time frame and explains the presence of helium in the mantle. However, the uranium, thorium, and other elements involved would be diffused through the core material (i.e. in solution in the liquid outer core, or as dopants in the iron crystal of the inner core). The absolute concentration of uranium in the Earth is very, very low. Without a really strong mechanism operating to separate it out and concentrate it, it's going to remain a trace impurity in other ores, and not a ball at the center of the Earth.
Secondly, I'm pretty sure that a 5-mile ball would be over the critical mass/volume envelope for an uncontrolled chain reaction of the U-235 and U-233 present in uranium ore. The fact that the Earth hasn't exploded suggests that uranium is not concentrated into a ball. Anyone with the fast-neutron cross section data care to work this out?
Now, on to other questionables.
The Earth's magnetic field is created by movement of the conducting material in the Earth's outer core. The polarity changes in the field are adequately explained by the idea that turbulence destabilizes the dynamo fluid currents every so often. A fascinating article was published about this a while back, but the citation escapes me.
Turbulence happens; it's a known and expected phenomenon. However, the article authours propose no mechanism for their magical solid-state fission reactor to turn on and off every so often to reset the dynamo currents. Thus, I consider the turbulence conjecture the more plausible.
Now, on to Jupiter. While Jupiter undoubtedly also has heavy element fission contributing to its heat, the majority of its heat is expected to come from it essentially continuing to slowly compact itself. The idea is that as hydrogen progresses from gas to liquid to metallic liquid to metallic solid state, it undergoes several exothermic phase transitions (analagous to the heat of condensation for more common substances). This provides a feedback loop that limits the rate of conversion - for example, if a lot of liquid hydrogen starts converting to liquid metallic hydrogen, the boundary layer heats up, which makes it less favourable for the conversion to continue. The rate of conversion for some of these phases is expected to be slow enough for Jupiter not to have reached its final equilibrium composition. If the conversion is still going on, then as it's exothermic, it could indeed explain heat generation in Jupiter.
A similar mechanism involving crystallization of iron was proposed as a source of Earth's geothermal energy, though this is less convincing as the amounts of matter involved are small enough that Earth should have reached equilibrium long ago.
In summary, the "mysteries" that the article attempts to invoke compact reactors to solve are already adequately explained without the need for such an implausible mechanism.
1st) I have read that the radioactivity of spent fuel rods is so great, that the lethal dose of gamma rays would occur in a matter of hours to anyone withing a good (10yards) area. I hope those bomb makers are fast...
Drop it in a lead suitcase, or a swimming pool, or down a hole in your yard. All you need is a lot of matter between you and the radioactives.
Or just spend 20 minutes duct-taping the bomb, radioactives, and tamping materials together, and then stay a good ways away from the radioactives. Terrorists generally don't care what happens to themselves as long as the goal gets accomplished.
2nd) Ohhh.... so contaminating an area with low-grade nuclear material with half lives around 30 days is going to kill us all...
This elegantly displays your degree of reading comprehension.
[Hint: "The actual health effects of the contamination would be next to nil."]
3rd) Saying a large bomb blowing some nuclear material for blocks would cause more fear and expense then a biological or nerve gas attack is obviously using very simple logic.
Have you ever raised the topic of nuclear contamination in a random group of people and listened to them talk it over for the next 10 minutes?
People know nothing about radioactivity. They just know that Radiation Is Bad. Bad, Bad, Bad. Any application of actual facts or common sense fails to have any impact.
Try this some time.
In summary, I believe that the dirty-bomb scare tactic would work quite well.
I'm no nuclear weapons engineer, but everything I've read says dirty bombs,
- Do less damage, to people and things, than a plain old-fashioned bomb filled with nails.
- Can be cleaned up (for contaminated humans, at least) by stripping and washing yourself with a garden hose.
- Cost so much more than a standard terrorist bomb to make, and being less effective (if you discount the hype and resulting fear), that we should hope the terrorists waste their resources on it instead of something more dangerous.
If you manage to steal any of the spent fuel that's lying around, or even a medium-sized shipment of medical isotopes, you have enough to contaminate a good chunk of the core of a major city. While harder to acquire than a few bags of fertilizer, it's by no means prohibitively hard.
The actual health effects of the contamination would be next to nil. But the goal of terrorism is exactly that - terror. North America is full of people who run around screaming about nuclear reactors which release less radiation than the concrete in their basements. People would go *nuts* if a dirty bomb raised background radiation by *any* detectable amount.
Not even a nerve gas attack would cause that much mayhem. It would be the perfect attack.
Nevermind the fact that lawsuits over alleged health problems from the infinitesimally higher exposure would drag on for decades.
I would even the steep price tag more or less justifiable, considering the impress-your-friends factor. People spend more on PDAs. But... well, what good is a replica light saber if you can't saber duel with yer buddies? The specs mention that the plasma lamp is encased in a virtually indestructible polycarbonate (actually, it reads "polycarbonite," which is either a typo or a clever pun) housing.
It's the same stuff CDs are made of, and those are hard enough to break (try some time). I think it would survive dueling (I'd worry more about the mounting point than the blade itself).
These aren't plasma tubes (that was a different light sabre manufacturer, who used glass tube blades and was featured here a year or two ago). The light sabres on this site use an electroluminescent coating on the inside of the tube like the kind in the "indiglo" watches (probably exactly the same kind, as the authour uses the word "indiglo" when describing it).
So there are no high voltages and no vacuum chambers involved in making your light sabre look pretty:).
I'd phone the seller and ask if these can stand up to dueling before trying it with a $370 sword, though.
I wonder if no one noticed the little line on top that says, may 1995. If this technology is that old, how come it isnt on the market yet?
Because you'd need a cryogenically cooled detector and even wierder detector materials than you have to use for thermal IR.
A camera that detects sub-millimetre waves (the proper name for THz-range EM) is even more of a pain to build than one of the good, expensive thermal IR cameras, so unless you have an application where a thermal IR camera or X-ray system or low-power impulse radar system won't work, you aren't going to sell any.
This market is apparently small enough that nobody's mass-produced sub-millimetre range imaging systems commercially yet.
"an Earth-sized planet has a gravity well deep enough to hold an inhospitably thick atmosphere. Only some quirks of Earth's formation and evolution..."
and "Earth-like planets do seem to be the best place to look for non-microbal life"
Vacuum is even less hospitable to life than a thick atmosphere:).
As you correctly point out, a large moon may be an additional requirement.
A very good article on this can be found here [spacedaily.com]. Although this is a slightly different advantage that the moon gave the earth, ie the landmass..
While I agree with the article's assertation that plate techtonics are needed for a hospitable environment, I think its logic is suspect when discussing the moon's role in the formation of our own.
The thickness of the crust is relatively insensitive to mass being magically added or removed - it's a result of the rate of heat generation in the core and the thermal properties of the mantle. As the core's heat conducts outwards, you get a temperature gradient set up. The outer surface of the planet will be at or near the blackbody temperature needed to radiate this heat into space at the rate it's generated; the lower boundary of the crust is at the point where temperature has increased enough for rock to be pliable (not necessarily molten, for the upper mantle).
If you were to take the moon apart and coat the earth with it, the thickness of the crust wouldn't change - you'd get the lower parts of it being absorbed into the mantle.
Plate techtonics are the result of the mantle's equivalent of climate. As there's a heat gradient in the mantle, convection currents are set up that move material around. As the Earth is spinning, you get a complicated pattern of currents set up analogous to the "trade winds" in the atmosphere. These mantle currents drag bits of the solidified crust with them, resulting in the plate motions we're all familiar with. As long as the crust is thin enough to be moved, this will occur (and I established above that its thickness is fairly insensitive to more or less mass being added, as long as the Earth's radius doesn't change by a substantial fraction).
Lastly, the article implies that the moon was formed from ablated crust material. This is not strictly true. The original impact (of a Mars-sized body) would have disrupted both the crust and the mantle, ejecting a vast amount of material, most of which either permanently escaped or fell back to the Earth. Only a relatively small amount stayed in a stable orbit and coalesced into the moon. The Earth had to re-form its crust from scratch after this event - so the post-moon crust would have had pretty much the same characteristics as the pre-moon crust.
In summary, I think that it's the Earth's gross size and rate of core heat generation that determine whether or not it has plate techtonics, not the presence or formation of the moon.
Interesting. Could you elaborate on this? (which quirks? how does the moon fit in to this?
If I understand correctly, the moon's influence stripped off much of Earth's early atmosphere (which would otherwise have ended up Venus-like). It also keeps Earth's axis from wobbling too much.
You'd have to ask someone else for the details, though; this isn't my area of expertise.
i don't get the thrust of the article focusing on finding earth-sized planets. is there some theory that necessitates a planet be our size to foster life? if so, why?
Planets smaller than Earth will tend to lose their atmospheres over time (e.g. Mars, Mercury).
Planets larger than Earth will tend to have super-thick atmospheres with very hostile environments (e.g. the smaller gas giants, and Venus). Notice Venus in this list - an Earth-sized planet has a gravity well deep enough to hold an inhospitably thick atmosphere. Only some quirks of Earth's formation and evolution (mainly the presence of the moon) give us an atmosphere thin enough to let our type of climate and our type of life exist.
Life could exist deep underground in a much wider range of planets, but this would be microbes and not much else.
Life could potentially exist in oceans under the frozen crust of smaller worlds (e.g. Europa), but would likely be less interesting than life on Earth-like worlds, due to a much smaller energy throughput. These worlds would also have to have a substantial source of heat (either radioactive, like Earth's, or tidal, from being a satellite of a larger planet) to avoid freezing solid. Larger worlds will probably have enough geothermal energy to churn up their oceans, making stable life-bearing layers less likely.
So, Earth-like planets do seem to be the best place to look for non-microbal life:).
Aren't the Coriolis force and the gyroscopic effect somehow related to "gravito-magnetic" forces ?
No, they're just consequences of Newton's laws of motion.
Coriolis effect is the result of you (or a thrown object) trying to move in a straight line while your point of view rotates.
Gyroscopic effects are the result of conservation of momentum in the flywheel (to change the axis of rotation, you have to apply a torque that makes up for the change in angular momentum).
The resulting expulsion of magnetic fields is called the Meissner effect. Another consequence of this is that currents can not flow in the bulk of a superconductor, but only at the surface. This is why superconducting wires are always finely threaded, to increase the surface area per weight. All of this is quite different from a normal conductor, even in the limit of zero resistance. It is all a direct consequence of the existence of a macroscopic, coherent quantum state.
My point is that you *do* see effects like this in conventional conductors as resistance approaches zero (i.e. in practice when you're at high enough frequency for reactive effects to dominate resistance). An ordinary conductor will very happily reflect/exclude applied oscillating magnetic fields by setting up opposed currents, and for the same reason you get "skin effect" for high frequency currents.
The underlying mechanisms in a superconductor are different, which causes interesting effects in the transition region (magnetic flux bundles penetrating the superconductor in regions of local breakdown, which AFAIK does not happen with conventional conductors). However, I do not recall any mention of the proposed measured effects being tied to phenomena that were exclusive to superconductors.
Hence, my question. If gravitation couples to EM, you sure as heck *should* see some interaction between gravity waves and ordinary conductors, especially since gravity waves would be coupled with an oscillating EM field.
This is the way it's done! Black Holes were nothing more than a theory with mathematical arguments that "seem(ed) to be correct", until CHANDRA started supplying experimental evidence. General Relativity was a theory with mathermatical aruments that "seem(ed) to be correct", until we managed to observe light bending around the mass of the sun.
Not completely true. While many additional predictions of both SR and GR were tested after the theories were proposed, part of the argument for them was that they also explained a lot of existing observations known to disagree with Newtonian mechanics.
Precession of the orbit of Mercury was one of these. Lack of the Ether Wind was another (C appeared constant independent of motion).
A model which explains previously-confusing existing results in addition to making predictions is a lot more promising than one which just proposes new results outside the domain we've already looked at (though both are of course potentially useful).
Superconductors seem to be the material of choice for antigravity claims nowadays. But if these effects are real, why don't we see them with normal conductors?
Even at relatively low frequencies, the reactance of, say, copper or aluminum by far dominates its resistance. This is how things like transformers and motors work. Most of the effects claimed do not seem to require perfectly resistance-free current flow, so why, in a century or more of electrical experimentation, weren't they found long ago, and why are none of these experimenters claiming results with ordinary conducting materials?
The hotter you want to heat something in this manner, the more energy you'll have to add, exponentially; the hotter the planet is then it "should" be, the faster the heat will leave.
Nit-pick: This isn't exponential. The earth's energy loss due to radiative emission is proportional to the fourth power of the temperature. So, the power input you need to (constantly) maintain to raise the earth's temperature by a given amount is:
dP = a[(T + t)^4 - T^4]
...Where T is the usual average temperature of the Earth, and t is the amount you want to raise it by, in degrees Kelvin. "a" is a proportionality constant equal to P0 / T4, where P0 is the solar power absorbed by the Earth (about 1.3e17 W).
Assuming your change is much smaller than the absolute temperature (around 300 degrees K), this is a roughly linear relation with respect to t:
The problem with VHS degradation over time has nothing to do with the data format on the tape. The problem is with the medium itself: flexible magnetic storage.
On the contrary, data format matters a lot, as it tells you how sensitive the content will be to medium degradation.
A (binary) digital tape - one with two levels of data per sample - can tolerate far more noise than an analog tape that stores a large number of levels per sample. Error correction codes can be applied to digital data, which allows you to correct one (or several) corrupted bits per code in the data stream. Analog encoding doesn't let you do this. In many other ways, digital encoding lets you map content space into signal space so that you can have large amounts of signal noise/degradation without the content degrading much.
Digital encoding also lets you reconstruct _perfectly_ the original content when only moderate degradation has occurred - letting you copy a worn tape on to a pristine one with no content loss. This isn't possible with analog video encoding.
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Last time I checked, absence of gravity didnt mean absence of mass. In order to move a mass you need a force. Inertia is still there.
True, but you can get away with applying much less force (and moving more slowly as a result).
Also, you don't need to exert effort to keep your body in the same position (as you would to some extent for most positions on Earth).
$20,000 for three months? Wow. That sure beats those cheapskates at NASA; they only spent $100 / day, or ~$9,000 for the three months.
This is indeed a generous amount. However, bear in mind that you'd also suffer fallout at work from taking a 3-month sabbatical, and you'll spend weeks regaining the ability to move or do anything strenuous for more than a few tens of minutes at a stretch.
The good news is that this still beats having to sit around in true zero-g, which would do even nastier things to your body (in bed you still have to exert effort to lift things with your hands, to roll over, to breathe (to some extent), etc.).
I've had a little bit of experience with lasers, and I'm pretty sure that the modulation required to accomplish this is going to be orders of magnitude higher than what is needed to burn data
Not really. All they're doing is taking advantage of the fact that a burned part of a CD looks noticeably different from a non-burned part, and selectively burning.
As there's a visible difference between used and unused sections on a normally-burned CD, I don't see why you'd need any special hardware to pattern this difference.
AOL stamped their logo by similar methods into a wave of CDs a while back.
I was keeping a few as extra-pretty coasters, but they were thrown out behind my back...
The ONE new feature I would like best on my computer is for it to know what I mean when I say "Stop! No! I didn't mean that!"
Here's a thought - imagine a system where you use journaling and checkpointing to track *all* changes to both filesystems and program states, and give the user the ability to roll back changes arbitrarily and to great distance.
This would definitely be useful in recovering from catastrophic user errors, and might even be implementable without having to rewrite every application in the universe (take an image of an application's processes' memory spaces, and either carefully note the state of all file descriptors (especially device handles), or wait until they're in a sane state before checkpointing).
One of the cluster job distribution tools I've come across already does this to some degree ("condor", which can be set up to do checkpointing if desired).
Also, there are no fixed limits on how much information you can store on hologram - you can always store something more, which will lower the quality of the rest of stored information, but you won't hit any fixed maximum number of bits, like with standard types of memory. Saying that it "[beats] out DVD by an order of magnitude" is totally ignoring the most fundamental features of holographic memory.
/dev/null to store data and /dev/random to retrieve it and claim as much space as I want.
The problem is, if I don't care about the quality of the data retrieved, I could use
If you need to get your data back intact - i.e. with enough fidelity for you to rebuild the original data without loss - there turns out to be a hard limit to how much you can store with a holographic storage medium. The exact limit varies based on the geometry of the setup and of the holographic medium, but can be calculated. You can also measure it directly for any real system, which is presumably what the company involved did when citing storage densities for its prototype.
So, while the accessing method is very different, the storage limit for holograms scales in the same way as storage limits for other types of device (in this case, with the volume of the holographic film IIRC).
Take note of that third section: no nasty chemicals, they claim. If their claim holds, a company using this tech could make a lot of political capital from it.
The Princeton site makes no claim of this being a chemical-free process; all they use the imprinter for is patterning the etching resist, as an alternative to using a light-sensitive photoresist and exposing it to light and developing it to get the patterning. Under this scheme, virtually all of the nasty chemicals would still be present (you'd have a bit more flexibility in choosing resists, but that's just one set of chemicals out of a whole zoo that are needed).
The BBC report claims that patterns are directly stamped into the deposited material. This could be legit, or it could just be a misinterpretation of the resist stamping. Even if it is the patterning mechanism (i.e. if no resist or developing is needed), you still have nasty chemicals used when depositing layers of various substances on the substrate and when etching (which you'll still need to do - pure stamping will leave a thin layer of the undesired material in the stamped region even if most of it flows away).
In summary, I'd take claims of environmental friendliness with a large grain of salt.
Shoot, straight Floride gas. Mean enough to bond with most (all?) noble gases
Fluorine, and no - only Krypton and heavier. Helium, Neon, and Argon are inert enough that there are no stable compounds of them under normal conditions.
Without a really strong mechanism operating to separate it out and concentrate it, it's going to remain a trace impurity in other ores, and not a ball at the center of the Earth.
There is such a mechanism. Everyone agrees that the core is iron. How did that happen, when the Earth coalesced from random rocky materials? The same way. If iron, why not uranium?
Iron is plentiful. Enough of it was present for gross gravitational effects to be enough to separate it from lighter ores within solution.
Uranium is far, far less plentiful, and so would tend to remain dissolved.
There are no "grains" to migrate, as you suggest - uranium would be mixed in as impurities on an atomic level, literally dissolved in other metals and metal oxides.
Man, is this article bad.
The article proposes a 5-mile sphere of uranium at the Earth's core as the source of Earth's geothermal energy.
Now, the idea of radioactive decay powering the Earth's geothermal heat generation isn't a new one - in fact, it's one of the more plausible models, as it works quite well over a very long time frame and explains the presence of helium in the mantle. However, the uranium, thorium, and other elements involved would be diffused through the core material (i.e. in solution in the liquid outer core, or as dopants in the iron crystal of the inner core). The absolute concentration of uranium in the Earth is very, very low. Without a really strong mechanism operating to separate it out and concentrate it, it's going to remain a trace impurity in other ores, and not a ball at the center of the Earth.
Secondly, I'm pretty sure that a 5-mile ball would be over the critical mass/volume envelope for an uncontrolled chain reaction of the U-235 and U-233 present in uranium ore. The fact that the Earth hasn't exploded suggests that uranium is not concentrated into a ball. Anyone with the fast-neutron cross section data care to work this out?
Now, on to other questionables.
The Earth's magnetic field is created by movement of the conducting material in the Earth's outer core. The polarity changes in the field are adequately explained by the idea that turbulence destabilizes the dynamo fluid currents every so often. A fascinating article was published about this a while back, but the citation escapes me.
Turbulence happens; it's a known and expected phenomenon. However, the article authours propose no mechanism for their magical solid-state fission reactor to turn on and off every so often to reset the dynamo currents. Thus, I consider the turbulence conjecture the more plausible.
Now, on to Jupiter. While Jupiter undoubtedly also has heavy element fission contributing to its heat, the majority of its heat is expected to come from it essentially continuing to slowly compact itself. The idea is that as hydrogen progresses from gas to liquid to metallic liquid to metallic solid state, it undergoes several exothermic phase transitions (analagous to the heat of condensation for more common substances). This provides a feedback loop that limits the rate of conversion - for example, if a lot of liquid hydrogen starts converting to liquid metallic hydrogen, the boundary layer heats up, which makes it less favourable for the conversion to continue. The rate of conversion for some of these phases is expected to be slow enough for Jupiter not to have reached its final equilibrium composition. If the conversion is still going on, then as it's exothermic, it could indeed explain heat generation in Jupiter.
A similar mechanism involving crystallization of iron was proposed as a source of Earth's geothermal energy, though this is less convincing as the amounts of matter involved are small enough that Earth should have reached equilibrium long ago.
In summary, the "mysteries" that the article attempts to invoke compact reactors to solve are already adequately explained without the need for such an implausible mechanism.
I don't know, have you ever brought it up with a bunch of people?
Yes.
Like I said, try it yourself before flaming me.
1st) I have read that the radioactivity of spent fuel rods is so great, that the lethal dose of gamma rays would occur in a matter of hours to anyone withing a good (10yards) area. I hope those bomb makers are fast...
Drop it in a lead suitcase, or a swimming pool, or down a hole in your yard. All you need is a lot of matter between you and the radioactives.
Or just spend 20 minutes duct-taping the bomb, radioactives, and tamping materials together, and then stay a good ways away from the radioactives. Terrorists generally don't care what happens to themselves as long as the goal gets accomplished.
2nd) Ohhh.... so contaminating an area with low-grade nuclear material with half lives around 30 days is going to kill us all...
This elegantly displays your degree of reading comprehension.
[Hint: "The actual health effects of the contamination would be next to nil."]
3rd) Saying a large bomb blowing some nuclear material for blocks would cause more fear and expense then a biological or nerve gas attack is obviously using very simple logic.
Have you ever raised the topic of nuclear contamination in a random group of people and listened to them talk it over for the next 10 minutes?
People know nothing about radioactivity. They just know that Radiation Is Bad. Bad, Bad, Bad. Any application of actual facts or common sense fails to have any impact.
Try this some time.
In summary, I believe that the dirty-bomb scare tactic would work quite well.
I'm no nuclear weapons engineer, but everything I've read says dirty bombs,
- Do less damage, to people and things, than a plain old-fashioned bomb filled with nails.
- Can be cleaned up (for contaminated humans, at least) by stripping and washing yourself with a garden hose.
- Cost so much more than a standard terrorist bomb to make, and being less effective (if you discount the hype and resulting fear), that we should hope the terrorists waste their resources on it instead of something more dangerous.
If you manage to steal any of the spent fuel that's lying around, or even a medium-sized shipment of medical isotopes, you have enough to contaminate a good chunk of the core of a major city. While harder to acquire than a few bags of fertilizer, it's by no means prohibitively hard.
The actual health effects of the contamination would be next to nil. But the goal of terrorism is exactly that - terror. North America is full of people who run around screaming about nuclear reactors which release less radiation than the concrete in their basements. People would go *nuts* if a dirty bomb raised background radiation by *any* detectable amount.
Not even a nerve gas attack would cause that much mayhem. It would be the perfect attack.
Nevermind the fact that lawsuits over alleged health problems from the infinitesimally higher exposure would drag on for decades.
I would even the steep price tag more or less justifiable, considering the impress-your-friends factor. People spend more on PDAs. But... well, what good is a replica light saber if you can't saber duel with yer buddies? The specs mention that the plasma lamp is encased in a virtually indestructible polycarbonate (actually, it reads "polycarbonite," which is either a typo or a clever pun) housing.
:).
It's the same stuff CDs are made of, and those are hard enough to break (try some time). I think it would survive dueling (I'd worry more about the mounting point than the blade itself).
These aren't plasma tubes (that was a different light sabre manufacturer, who used glass tube blades and was featured here a year or two ago). The light sabres on this site use an electroluminescent coating on the inside of the tube like the kind in the "indiglo" watches (probably exactly the same kind, as the authour uses the word "indiglo" when describing it).
So there are no high voltages and no vacuum chambers involved in making your light sabre look pretty
I'd phone the seller and ask if these can stand up to dueling before trying it with a $370 sword, though.
I wonder if no one noticed the little line on top that says, may 1995. If this technology is that old, how come it isnt on the market yet?
Because you'd need a cryogenically cooled detector and even wierder detector materials than you have to use for thermal IR.
A camera that detects sub-millimetre waves (the proper name for THz-range EM) is even more of a pain to build than one of the good, expensive thermal IR cameras, so unless you have an application where a thermal IR camera or X-ray system or low-power impulse radar system won't work, you aren't going to sell any.
This market is apparently small enough that nobody's mass-produced sub-millimetre range imaging systems commercially yet.
You contradict yourself:
:).
"an Earth-sized planet has a gravity well deep enough to hold an inhospitably thick atmosphere. Only some quirks of Earth's formation and evolution..."
and "Earth-like planets do seem to be the best place to look for non-microbal life"
Vacuum is even less hospitable to life than a thick atmosphere
As you correctly point out, a large moon may be an additional requirement.
A very good article on this can be found here [spacedaily.com]. Although this is a slightly different advantage that the moon gave the earth, ie the landmass..
While I agree with the article's assertation that plate techtonics are needed for a hospitable environment, I think its logic is suspect when discussing the moon's role in the formation of our own.
The thickness of the crust is relatively insensitive to mass being magically added or removed - it's a result of the rate of heat generation in the core and the thermal properties of the mantle. As the core's heat conducts outwards, you get a temperature gradient set up. The outer surface of the planet will be at or near the blackbody temperature needed to radiate this heat into space at the rate it's generated; the lower boundary of the crust is at the point where temperature has increased enough for rock to be pliable (not necessarily molten, for the upper mantle).
If you were to take the moon apart and coat the earth with it, the thickness of the crust wouldn't change - you'd get the lower parts of it being absorbed into the mantle.
Plate techtonics are the result of the mantle's equivalent of climate. As there's a heat gradient in the mantle, convection currents are set up that move material around. As the Earth is spinning, you get a complicated pattern of currents set up analogous to the "trade winds" in the atmosphere. These mantle currents drag bits of the solidified crust with them, resulting in the plate motions we're all familiar with. As long as the crust is thin enough to be moved, this will occur (and I established above that its thickness is fairly insensitive to more or less mass being added, as long as the Earth's radius doesn't change by a substantial fraction).
Lastly, the article implies that the moon was formed from ablated crust material. This is not strictly true. The original impact (of a Mars-sized body) would have disrupted both the crust and the mantle, ejecting a vast amount of material, most of which either permanently escaped or fell back to the Earth. Only a relatively small amount stayed in a stable orbit and coalesced into the moon. The Earth had to re-form its crust from scratch after this event - so the post-moon crust would have had pretty much the same characteristics as the pre-moon crust.
In summary, I think that it's the Earth's gross size and rate of core heat generation that determine whether or not it has plate techtonics, not the presence or formation of the moon.
Interesting. Could you elaborate on this? (which quirks? how does the moon fit in to this?
If I understand correctly, the moon's influence stripped off much of Earth's early atmosphere (which would otherwise have ended up Venus-like). It also keeps Earth's axis from wobbling too much.
You'd have to ask someone else for the details, though; this isn't my area of expertise.
i don't get the thrust of the article focusing on finding earth-sized planets. is there some theory that necessitates a planet be our size to foster life? if so, why?
:).
Planets smaller than Earth will tend to lose their atmospheres over time (e.g. Mars, Mercury).
Planets larger than Earth will tend to have super-thick atmospheres with very hostile environments (e.g. the smaller gas giants, and Venus). Notice Venus in this list - an Earth-sized planet has a gravity well deep enough to hold an inhospitably thick atmosphere. Only some quirks of Earth's formation and evolution (mainly the presence of the moon) give us an atmosphere thin enough to let our type of climate and our type of life exist.
Life could exist deep underground in a much wider range of planets, but this would be microbes and not much else.
Life could potentially exist in oceans under the frozen crust of smaller worlds (e.g. Europa), but would likely be less interesting than life on Earth-like worlds, due to a much smaller energy throughput. These worlds would also have to have a substantial source of heat (either radioactive, like Earth's, or tidal, from being a satellite of a larger planet) to avoid freezing solid. Larger worlds will probably have enough geothermal energy to churn up their oceans, making stable life-bearing layers less likely.
So, Earth-like planets do seem to be the best place to look for non-microbal life
Aren't the Coriolis force and the gyroscopic effect somehow related to "gravito-magnetic" forces ?
No, they're just consequences of Newton's laws of motion.
Coriolis effect is the result of you (or a thrown object) trying to move in a straight line while your point of view rotates.
Gyroscopic effects are the result of conservation of momentum in the flywheel (to change the axis of rotation, you have to apply a torque that makes up for the change in angular momentum).
The resulting expulsion of magnetic fields is called the Meissner effect. Another consequence of this is that currents can not flow in the bulk of a superconductor, but only at the surface. This is why superconducting wires are always finely threaded, to increase the surface area per weight. All of this is quite different from a normal conductor, even in the limit of zero resistance. It is all a direct consequence of the existence of a macroscopic, coherent quantum state.
My point is that you *do* see effects like this in conventional conductors as resistance approaches zero (i.e. in practice when you're at high enough frequency for reactive effects to dominate resistance). An ordinary conductor will very happily reflect/exclude applied oscillating magnetic fields by setting up opposed currents, and for the same reason you get "skin effect" for high frequency currents.
The underlying mechanisms in a superconductor are different, which causes interesting effects in the transition region (magnetic flux bundles penetrating the superconductor in regions of local breakdown, which AFAIK does not happen with conventional conductors). However, I do not recall any mention of the proposed measured effects being tied to phenomena that were exclusive to superconductors.
Hence, my question. If gravitation couples to EM, you sure as heck *should* see some interaction between gravity waves and ordinary conductors, especially since gravity waves would be coupled with an oscillating EM field.
This is the way it's done! Black Holes were nothing more than a theory with mathematical arguments that "seem(ed) to be correct", until CHANDRA started supplying experimental evidence. General Relativity was a theory with mathermatical aruments that "seem(ed) to be correct", until we managed to observe light bending around the mass of the sun.
Not completely true. While many additional predictions of both SR and GR were tested after the theories were proposed, part of the argument for them was that they also explained a lot of existing observations known to disagree with Newtonian mechanics.
Precession of the orbit of Mercury was one of these. Lack of the Ether Wind was another (C appeared constant independent of motion).
A model which explains previously-confusing existing results in addition to making predictions is a lot more promising than one which just proposes new results outside the domain we've already looked at (though both are of course potentially useful).
Superconductors seem to be the material of choice for antigravity claims nowadays. But if these effects are real, why don't we see them with normal conductors?
Even at relatively low frequencies, the reactance of, say, copper or aluminum by far dominates its resistance. This is how things like transformers and motors work. Most of the effects claimed do not seem to require perfectly resistance-free current flow, so why, in a century or more of electrical experimentation, weren't they found long ago, and why are none of these experimenters claiming results with ordinary conducting materials?
The hotter you want to heat something in this manner, the more energy you'll have to add, exponentially; the hotter the planet is then it "should" be, the faster the heat will leave.
Nit-pick: This isn't exponential. The earth's energy loss due to radiative emission is proportional to the fourth power of the temperature. So, the power input you need to (constantly) maintain to raise the earth's temperature by a given amount is:
dP = a[(T + t)^4 - T^4]
...Where T is the usual average temperature of the Earth, and t is the amount you want to raise it by, in degrees Kelvin. "a" is a proportionality constant equal to P0 / T4, where P0 is the solar power absorbed by the Earth (about 1.3e17 W).
Assuming your change is much smaller than the absolute temperature (around 300 degrees K), this is a roughly linear relation with respect to t:
a[4T^3 * t]
or
P0 * 4t/T
The problem with VHS degradation over time has nothing to do with the data format on the tape. The problem is with the medium itself: flexible magnetic storage.
On the contrary, data format matters a lot, as it tells you how sensitive the content will be to medium degradation.
A (binary) digital tape - one with two levels of data per sample - can tolerate far more noise than an analog tape that stores a large number of levels per sample. Error correction codes can be applied to digital data, which allows you to correct one (or several) corrupted bits per code in the data stream. Analog encoding doesn't let you do this. In many other ways, digital encoding lets you map content space into signal space so that you can have large amounts of signal noise/degradation without the content degrading much.
Digital encoding also lets you reconstruct _perfectly_ the original content when only moderate degradation has occurred - letting you copy a worn tape on to a pristine one with no content loss. This isn't possible with analog video encoding.
So, data format does matter.