Irradiation of hand-written mail would sterilize
anything passing through the irradiator and leave
no radioactive residue. It would
mean an end to sending live things (I've traded
sourdough via email) and radiation sensitive items
like electronic parts or film would have to be
marked specially or sent another way -- but
routine irradiation would make it much, much harder to sneak live anything into someone's mail.
We just ordered Sprint's ION service -- due in our house in
two weeks. It's 8Mbits down/ 1Mbit up, rolled
in with local phone service and $0.07/minute
long distance -- all for $100/month. If they can make it work at that rate, it'll eat DSL's lunch.
Cringely didn't seem to notice that, two years after their initial announcements, Sprint has finally rolled out their service. Based on the web site and hype, it seems to (finally) be everything they promised back in 1999.
I don't have the service yet -- so I can't comment on how good it is -- but I'll post something when it's installed.
There have been other TLDs in operation in
limited subsets of the 'Net for some time.
Check out OpenNIC's site for a host of information about an internet namespace that's administered democratically. (There are several such namespaces, many of which are coalescing into a large, collaborative space run by the people,
for the people. OpenNIC is particularly well
run.)
The new ICANN standards actually conflict with pre-existing namespaces (such as.biz).
All you have to do is point your DNS server into
the OpenNIC tree...
The legal basis for restrictive EULAs is that you have to make a copy of the software (in your computer's RAM) in order to use it. Copying is prohibited without explicit permission, and so, therefore, is use. Therefore the companies can ask you to sign whatever argument they want before allowing you to use the software. If the license is non-transferable then, sure, you can sell the source CD for the software -- but the poor schnook who buys it from you doesn't have a license to copy it, so he can't use it.
Yep, I know it sounds stupid (and means, for example, that online documentation has more restrictions than the exact same information printed on paper). But there are federal legal precedents for that interpretaiton. Check out, for example, MAI vs. Peak Computer, from 1993.
No, there's no need to agree to the GPL before incorporating the code into your own work: copyright law forbids you from incorporating and copying the code without permission from the author. The GPL grants you that permission.
If you didn't agree to the GPL (or get permission from the copyright holder in some other way), you're not allowed to make copies. Not because of the GPL itself but because that's how copyright works.
The reason why shrink-wrap licenses are prevalent for more conventional SW is that they take away rights that you would otherwise have (if you didn't agree to the license). The GPL does none of that -- it only grants you rights that you wouldn't normally have. Sigh.
We were looking at images of the solar corona. It's a distributed object with faint gradations in intensity. The biggest problem we had in general with compression was that cosmic ray spikes and stars in the field of view tended to cause "ringing" with JPEG and similar Fourier-type compression schemes.
I figured 0.33 MB per frame because 640x480 is about a half-megapixel, and you'd probably be happy binning it down to 320x240 (more typical of VHS video), yielding an eighth of a megapixel.
Putting in three color planes takes you back
up to something like a third of a megapixel. Eight bits per color plane gives you a third of
a megabyte. (Note that that's not really a good
way to think about it -- usually there's a LOT more information in the luminance signal [the RGB common mode] than in the hue and saturation signals -- so you might need fewer initial bits...)
Our 50:1 figure came from a single, noisy image plane with the criterion that 99% of the pixels had to be within 1 DN (12 bit DN) of the original value, after compression and restoral. The test image on which we applied 50:1 compression was from the TRACE satellite -- click the link for some sample images.
80% (factor of five) compression is unreasonably
inefficient. Even without frame-to-frame similarities, wavelet image compression schemes can achieve 50x compression with no visible degradation (I know, I did experiments last year as part of a spacecraft proposal effort). That's a factor of 10 from your figures -- 1.9 seconds per frame. Using the similarities between frames, it's not unreasonable to think that another factor-of-10 applies (MPEG achieves factor-of-100
compression where JPEG only gets factor-of-10), bringing the frame count up to 10/second.
Last year I did some work on image compression
using wavelet transforms. We were able to get
50:1 compression on scientific image data, with
12-bit dynamic range. That compression ratio was
without any use of interframe similarities --
a movie compression algorithm could probably
get another 20:1 compression without much trouble.
At 30 fps, 0.33 MB per frame, that's 10 MB of
image data per second. Compressed 1000 to one,
you're only talking about 10 kilobytes
per second. If you're willing to suffer with
less dynamic range around spike bits of data,
it's not unreasonable to think that another
factor of four could come out of that, giving 2.5
kB/sec or 20 kbps -- leaving 8kbps for the sound.
There is at least one specific example of prior art for
this patent. It is the SolarSoft distribution system developed by Sam Freeland out at Lockheed-Martin, to distribute solar physics related software across the internet. It uses a web interface to generate a script that runs on the client's machine, pulling pre-configured software across the internet and then updating it regularly.
The initial problem with the Eros rendezvous wasn't a navigational issue. It was a problem with the spacecraft rocket motor not switching off! Deep Impact won't have such a long final
burn -- just midcourse corrections, where there's
plenty of time to fix any problems.
I work with scientific spacecraft, and I'm
still always surprised at the precision with which we can determine distances and positions of distant objects. SOHO is a million miles from Earth, and its radial position is known to within a few centimeters.
Barring egregious mismanagement, it's not that hard to
hit celestial bodies -- we have the right tools for the job!
Hmmm... Would it slosh the oceans? perhaps.
The easiest way to figure it is that inert objects in LEO have several times the specific
energy of gasoline at the surface. (that is to say, the kinetic energy of a pound of gasoline
in orbit exceeds its latent chemical energy by
a factor of something like two). The tower's latent energy is greater because most of it is in a higher orbit than LEO -- but not more than a factor of two greater (LEO is halfway to Earth escape, energetically speaking). Gasoline and
TNT are comparable.
Hmmm.... Typical mass: suppose it's a tapered
pyramid a hundred meters across at the top and
pointy at the bottom, 50,000 km long. Density is
(of course) 1. That's 1/4 * 50,000 * 104 tonnes, or about 1011
tonnes. Impact would be equivalent to a few
thousand 100-megaton warheads. Well, OK, so that's a lot of energy. Just how much is it?
Ruining civilization would require sloshing the
water pretty high -- a reasonable estimate is, say, enough to lift 1% of the ocean 100m. The
Pacific Ocean's mass is something like (1 tonne/m3) * (10km) * (2000km * 5000km),
or 1017 tonnes -- an equivalent energy
to lifting the 1011 tonnes of the
station 105km. So, yup, everything's
in the right ballpark.
There's certainly not enough energy in the elevator to slosh "the entire Pacific and Atlantic across the continents, wiping out our entire civilization in one stroke" -- but there's probably enough to (briefly) flood the great plains with salt water.
Ch. expl. was caused by well-known Xe-135 effect
on
Fission in a Box
·
· Score: 2
I am a licensed nuclear reactor operator (though
my license isn't current). If I recall right,
Chernobyl blew up
not because of incomplete simulation, but because
boneheaded operators flouted well-known reactor
physics.
Chernobyl was operated at high
power levels (normal operation) and then shut down
for about eight hours while engineers mucked with
the console, then brought back up to critical condition. The basic problem is that nuclear
reactors are not like cars. When you shut 'em
off, they don't just lie dormant until you switch
them back on again.
When you operate a reactor, one of the fission
products decays (half-life eight hours) into Xe-135, which absorbs neutrons strongly. That has the same effect as inserting a bit of control rod into the reactor, and as the reactor comes up to equilibrium levels of Xe, you have to pull out bits of actual control rod in order to compensate. The
equilibrium level of Xe 135 in the core is determined
by the balance between production (which depends
on your average power level over the last eight
hours) and destruction (which depends on your power
level now) of the Xe.
When you turn off the reactor, you stop destroying the Xenon. It builds up in the reactor
core, effectively shutting down the reactor by
greater and greater margin until, about eight hours
later, it reaches a peak level and begins to decay
again.
The operators on the day of the accident found
that they had to pull large amounts of extra rod
out of the reactor core (because of the Xe-135,
though they didn't pause to think about it).
When they brought the reactor critical, the
Xe-135 was quickly destroyed by the neutrons
in the core, removing the extra damping effect
and making the reaction run away.
Even then, "SCRAM trips" (emergency shutoff safeguards) in the console would have
saved the day except that they had almost all been
disabled to test a single particular one.
The real problem with nuclear power isn't the
"normal" waste disposal problem. It's the incredible, abject, deep stupidity of the bottom
1% of nuclear plant workers. You can engineer
around physics, toxicity, and radiation -- but
you can't engineer around foolish people. I
was finally convinced of this truism by the
insanely stupid people in Japan, who made their
own critical assembly out of dissolved uranium
(by doubling the uranium batch size for faster
processing) -- other examples may be found
in the nuclear plant lore here in the U.S.
Heh, just what I get for shootin from the hip. I described materials with positive but sub-1 index of refraction. This stuff has negative index and is really new.
I'm not entirely sure what's new here -- negative
indices of refraction are not as uncommon as the article would have you believe.
The big deal is the difference between two different kinds of speeds of a wave. The wave's
group speed is the speed at which the wave
energy moves. What determines refractive index is the how a material influence waves' phase speed, an entirely different beast.
Phase speed is the speed at which wavefronts move through the medium, and it isn't limited by the speed of light. A techie example of a phase
speed is the speed at which text scrolls across a rolling LED sign (we've all seen them). You can make the text scroll as fast as you like, in principle, because individual LEDs don't have to communicate with one another -- they just turn on and off at set times. You can even make the text scroll faster than light!
Phase speed and group speed are the same in nondispersive media (that is to say, when all wavelengths are propagating at the same speed). In air and vacuum and the like, that's approximately true. But in a dispersive medium, where propagation speed depends on wavelength, they differ. An example of dispersive wave propagation is the motion of ripples on the surface of water. If you throw a stone into water and watch the individual ripples move, each tiny ripple forms behind and overtakes the overall ring of ripples, growing to a large size in the middle and then shrinking again as it gets away from the pack. The tiny individual ripples are following the phase speed, but the energy only propagates across the water as fast as the overall ring of ripples.
How is this related to negative index of refraction? Most materials reduce the phase speed of light, and hence have a positive index of refraction. But spatially coherent structures can have the opposite effect and raise the phase speed above C.
You see the effect in microwave waveguides (pipes for steering radio waves) and in radio scattering
through of coherent arrays of antennae. You also get it, albeit with much shorter wavelengths, in crystallography -- most crystals have a negative index of refraction for X-rays, as the crystal planes form waveguides for the short wavelengths.
To be honest, from the Reuters writeup I don't know what the big deal is or why UCSD issued a press release at all. Clearly we're not getting the whole story.
/. presses about to fall over (too slanted!)
on
New Linux Worm
·
· Score: 3
Why is it that whenever a M$ product get attacked by malware it's becase of crappy security in the OS, but
when linux gets attacked it's because the OS has
"finally arrived"?
Hmmmm...
English is not the primary language everywhere within 7 hours of Houston. Spanish is a hugely popular indigenous tongue throughout America. To avoid learning Spanish is to deny
the very existence of a large sector of the
Texan population.
The rub is that this problem -- that Internet users might save their digital stream and thereby
copy the music -- is exactly the same problem that
is faced by broadcasters! As a teenager, I certainly took great delight in compiling off-the-air cassettes of all my favorite songs.
What's different? As near as I can tell, nada.
Sorry to say, I'm just not buying this. Ever taken
a long-exposure color photograph by moonlight?
Colors come out normal. Similarly, ever looked at
moon rock? It's about as close to neutral grey as
a rock can get.
Actually, that's not quite right. RGB space works because most people have three main broadband color receptors. And, yes, the primary
colors have to be red, green, and blue (more on that later).
Sure, the
dyes each represent vectors in
the full infinite-dimensional spectral space, and
not simply particular wavelengths -- but so
long as they're linearly independent (i.e. you
can't generate the spectrum of any one dye out
of a weighted sum of the other dyes' spectra),
they're useful for distinguishing color.
The primary additive colors (R, G, and B)
are determined by the spectra of the dyes. You
can't pick any set of primary colors you want --
the color wheel was discovered experimentally long
before we knew the cellular biology to do direct
experiments on the human eye. The primary subtractive colors (C, M, Y) are made by subtracting the corresponding (R, G, or B) from
white light -- cyan light has G and B components,
but no R.
When you get into detailed color vision, things
(as always) get more complex. It turns out that
there are no precise primary colors that everyone
can agree on, because not everyone uses the same
dyes in his cones! There are slight variations
across the population, so that the R, G, and B
primary colors correspond to different pieces of
spectrum depending on who's looking.
Because of the overlap of (for example) the
R and G spectra, it's not normal possible to generate
a pure R signal in the human retina with any single wavelength of visible light. But we're
wired to do the linear decomposition ourselves:
in effect, the differential gain is really high
between the R and G "raw" channels coming out of
our retinas. Cool, eh? As laser pointing
becomes more accurate, we ought to be able to
stimulate directly our individual cones -- one day
somone could perceive "superred" by directly stimulating only the red cones in his fovea.
I wonder how different it would look than the
more common red?
There's a really interesting overview article
on color vision in the Feynman Lectures, volume I.
It includes typical spectra for R, G, and B dyes.
If I recall right, R and G are actually rather
similar spectrally, with somewhat broad humps in the long end of the spectrum, while the B dye has a very different spectrum with a sharp peak near the short end of blue.
The rods in your eye have a fourth photosensitive
dye beyond the usual (R,G,B) sets -- rhodopsin.
They're not ``wired'' the same way as regular (R,G,B)
cones are, so they don't contribute as strongly to
color vision -- but they do contribute. Why, for example, do stage managers use blue light to
signify darkness in the theater? Because rhodopsin
responds more to blue light than to red light. At
night, when we're seeing mainly with our rods,
we see mainly blue things. (as an experiment,
take a swatch of blue cloth and a swatch of red
cloth (of about equal darkness) out into moonlight. The blue cloth will
appear lightly shaded and the red will appear darker, because your rods are more sensitive to the blue light.
There might be colors (shades of blue and violet) that can be distinguished at twilight but
not in bright sunlight because of the importance
of rods to vision in the reduced light. I keep meaning to go check, but haven't.
That's pretty though-provoking, but I don't think that Star Wars would get as soundly thrashed as the current round of sci-fi nasties.
Aside from providing us with some actual character, plot, and theme, a story must remain
internally consistent in order for us (or for me,
anyway) to suspend disbelief.
By incorporating situations that are known to current physics and whose solutions are known (or at least obvious), Red Planet incorporates some of reality into its own storyline. By muffing the physics, or by having its characters and organizations make mistakes that ordinary
geeks can see through, or by lacking any sort of
motivation for the crisis-of-the-minute, RP sabotages the disbelief of its own audience. More importantly, the story isn't good enough to offset the egregious errors in the physics. When the physics is lousy, and the story sucks, and the acting is terrible, there's not much left except
some cool eye-candy.
SW billed itself as a fairy tale ("A long time ago, in a galaxy far, far away...") and hence
had much more latitude with the magic spacedrives
and gravity generators and such. That series
also seems to remain consistent within its own
set of rules (which, admittedly, it can make up as it goes!). More importantly, the first three movies actually had good stories to tell. The stories and characters were interesting in their own right, if a bit stereotyped, and the plots were focused and made a bit of sense. That's why
SW didn't suck.
The loads of scientific/engineering problems would
have been OK, if it weren't for the ham-handed
treatment of the humans and the horrifyingly banal
friendly-drone-turned-monstrous subplot. The plot
itself read like a parody of the worst of Star Trek: random crises thrown into the plot with gibberish technobabble explanations and no particular technical accuracy, plot justification,
or human value.
At least the producers of Battlefield Earth had an excuse -- they're $cientologists.
Technical errors which are too glaring to ignore:
Why try to terraform mars if the Earth is
dying? Why not try to terraform Earth? (Even if all the best ecosystems crash, terraforming Earth
is bound to be a lot easier than terraforming another world).
Why the big ship?
Why the 1-woman, 6-horny-guy crew? 0%, 50%,
and 100% seem like much better F/crew ratios for a
yearlong mission, than the 18% they flew.
Spacecraft with gravity-feed plumbing?
Centrifugal gravity with razor-straight floors? (at least 2001 had a nice curved hallway in the station interior)
Solar flares that make the whole spacecraft shake? And that with no warning at all from
Earth? (it should be hours after the flare that
the first protons arrive; and days after that when the solar wind shock wave arrives. Neither have enough power to shake the spacecraft!)
Why did they have to visit the planet to find
out that the GIGANTIC GREEN PATCHES they expected
weren't there?
What, no O2 spectroscopy from Hubble?
Why didn't they have radio contact with the Hab computers?
The effing radios in their effing suits can't
reach the station, but a tiny 100mw radio can
reach the Earth?
No O2 sensors on the lander? Come on folks, they're cheap! Most modern *cars* have O2 sensors in their exhaust systems. Instead people have
to asphyxiate in their own suits to discover
they can breathe outside?
The captain has to tell Houston that there
are people on the surface, moments after they tell her to tune in the surface signal?
The effing mystery storm
The effing exploding explorer-robot-turned-Terminator
Too many problems to count with the Russian
probe
The direction and screenplay sucked, sucked, sucked, and it didn't even swallow. Wooden characters; gratuitous ham-handed
sex; subplots that are introduced and forgotten in
seconds; dumb, stereotyped, dumbass dialog;
inexplicable choices for the crew (come on, are
these really the best and brightest? Or did NASA
just wander down to the nearest pool hall and
pick up a few buffoons to head to Mars?);
horrible flashbacks; random inexplicable crises;
and feeble attempts at heroics are just a few
of the more egregious problems with the directing.
Yuck.
My friends and I snuck into "Best of Show"
immediately afterward. Much better movie (albeit
with no special effects)! We laughed our asses off.
Interesting case (and I'm sorry I missed it the
first time around, on the 25th). The issue
here seems to be the nature of web publication:
once you sell thousands of copies of a book, they're gone -- but web publication requires
constant input from you. The problem is that the
law is meant to address things that are made and
distributed once, but read many times; while web
documents are (in common use) distributed once
per perusal.
Weisstein certainly wouldn't be in this predicament if his website were being sold in book form: it predates the contract with CRC, and he
says that it is
not derived from that work (in fact, it's more likely that the reverse is true). Why should
his website be treated any differently than any
other former publication?
The press release compared the energy density of the new batteries to that of lead-acid cells. It wasn't clear whether they were referring to the energy density by volume or by mass. (My guess is by mass, which is more favorable to them because lead is so effing dense).
Lead-acid isn't all that great for mass density, so don't expect greatly increased range from electric vehicles. The main advantages are that (A) the plastic can probably (eventually) be made cheaper than the lead, and (B) it can be charged quickly (provided that mega-amp charging
cables for cars become common, which is another
story...)
Slashdot Mirror
Irradiation of hand-written mail would sterilize anything passing through the irradiator and leave no radioactive residue. It would mean an end to sending live things (I've traded sourdough via email) and radiation sensitive items like electronic parts or film would have to be marked specially or sent another way -- but routine irradiation would make it much, much harder to sneak live anything into someone's mail.
Cringely didn't seem to notice that, two years after their initial announcements, Sprint has finally rolled out their service. Based on the web site and hype, it seems to (finally) be everything they promised back in 1999.
I don't have the service yet -- so I can't comment on how good it is -- but I'll post something when it's installed.
There have been other TLDs in operation in
.biz).
limited subsets of the 'Net for some time.
Check out OpenNIC's site for a host of information about an internet namespace that's administered democratically. (There are several such namespaces, many of which are coalescing into a large, collaborative space run by the people,
for the people. OpenNIC is particularly well
run.)
The new ICANN standards actually conflict with pre-existing namespaces (such as
All you have to do is point your DNS server into
the OpenNIC tree...
Yep, I know it sounds stupid (and means, for example, that online documentation has more restrictions than the exact same information printed on paper). But there are federal legal precedents for that interpretaiton. Check out, for example, MAI vs. Peak Computer, from 1993.
IANAL.
No, there's no need to agree to the GPL before incorporating the code into your own work: copyright law forbids you from incorporating and copying the code without permission from the author. The GPL grants you that permission.
If you didn't agree to the GPL (or get permission from the copyright holder in some other way), you're not allowed to make copies. Not because of the GPL itself but because that's how copyright works.
The reason why shrink-wrap licenses are prevalent for more conventional SW is that they take away rights that you would otherwise have (if you didn't agree to the license). The GPL does none of that -- it only grants you rights that you wouldn't normally have. Sigh.
We were looking at images of the solar corona. It's a distributed object with faint gradations in intensity. The biggest problem we had in general with compression was that cosmic ray spikes and stars in the field of view tended to cause "ringing" with JPEG and similar Fourier-type compression schemes.
I figured 0.33 MB per frame because 640x480 is about a half-megapixel, and you'd probably be happy binning it down to 320x240 (more typical of VHS video), yielding an eighth of a megapixel.
Putting in three color planes takes you back
up to something like a third of a megapixel. Eight bits per color plane gives you a third of
a megabyte. (Note that that's not really a good
way to think about it -- usually there's a LOT more information in the luminance signal [the RGB common mode] than in the hue and saturation signals -- so you might need fewer initial bits...)
Our 50:1 figure came from a single, noisy image plane with the criterion that 99% of the pixels had to be within 1 DN (12 bit DN) of the original value, after compression and restoral. The test image on which we applied 50:1 compression was from the TRACE satellite -- click the link for some sample images.
80% (factor of five) compression is unreasonably
inefficient. Even without frame-to-frame similarities, wavelet image compression schemes can achieve 50x compression with no visible degradation (I know, I did experiments last year as part of a spacecraft proposal effort). That's a factor of 10 from your figures -- 1.9 seconds per frame. Using the similarities between frames, it's not unreasonable to think that another factor-of-10 applies (MPEG achieves factor-of-100
compression where JPEG only gets factor-of-10), bringing the frame count up to 10/second.
Last year I did some work on image compression
using wavelet transforms. We were able to get
50:1 compression on scientific image data, with
12-bit dynamic range. That compression ratio was
without any use of interframe similarities --
a movie compression algorithm could probably
get another 20:1 compression without much trouble.
At 30 fps, 0.33 MB per frame, that's 10 MB of
image data per second. Compressed 1000 to one,
you're only talking about 10 kilobytes
per second. If you're willing to suffer with
less dynamic range around spike bits of data,
it's not unreasonable to think that another
factor of four could come out of that, giving 2.5
kB/sec or 20 kbps -- leaving 8kbps for the sound.
Solarsoft has been in use since before 1995.
I work with scientific spacecraft, and I'm still always surprised at the precision with which we can determine distances and positions of distant objects. SOHO is a million miles from Earth, and its radial position is known to within a few centimeters.
Barring egregious mismanagement, it's not that hard to hit celestial bodies -- we have the right tools for the job!
Hmmm.... Typical mass: suppose it's a tapered pyramid a hundred meters across at the top and pointy at the bottom, 50,000 km long. Density is (of course) 1. That's 1/4 * 50,000 * 104 tonnes, or about 1011 tonnes. Impact would be equivalent to a few thousand 100-megaton warheads. Well, OK, so that's a lot of energy. Just how much is it?
Ruining civilization would require sloshing the water pretty high -- a reasonable estimate is, say, enough to lift 1% of the ocean 100m. The Pacific Ocean's mass is something like (1 tonne/m3) * (10km) * (2000km * 5000km), or 1017 tonnes -- an equivalent energy to lifting the 1011 tonnes of the station 105km. So, yup, everything's in the right ballpark.
There's certainly not enough energy in the elevator to slosh "the entire Pacific and Atlantic across the continents, wiping out our entire civilization in one stroke" -- but there's probably enough to (briefly) flood the great plains with salt water.
Chernobyl was operated at high power levels (normal operation) and then shut down for about eight hours while engineers mucked with the console, then brought back up to critical condition. The basic problem is that nuclear reactors are not like cars. When you shut 'em off, they don't just lie dormant until you switch them back on again.
When you operate a reactor, one of the fission products decays (half-life eight hours) into Xe-135, which absorbs neutrons strongly. That has the same effect as inserting a bit of control rod into the reactor, and as the reactor comes up to equilibrium levels of Xe, you have to pull out bits of actual control rod in order to compensate. The equilibrium level of Xe 135 in the core is determined by the balance between production (which depends on your average power level over the last eight hours) and destruction (which depends on your power level now) of the Xe.
When you turn off the reactor, you stop destroying the Xenon. It builds up in the reactor core, effectively shutting down the reactor by greater and greater margin until, about eight hours later, it reaches a peak level and begins to decay again.
The operators on the day of the accident found that they had to pull large amounts of extra rod out of the reactor core (because of the Xe-135, though they didn't pause to think about it). When they brought the reactor critical, the Xe-135 was quickly destroyed by the neutrons in the core, removing the extra damping effect and making the reaction run away.
Even then, "SCRAM trips" (emergency shutoff safeguards) in the console would have saved the day except that they had almost all been disabled to test a single particular one.
The real problem with nuclear power isn't the "normal" waste disposal problem. It's the incredible, abject, deep stupidity of the bottom 1% of nuclear plant workers. You can engineer around physics, toxicity, and radiation -- but you can't engineer around foolish people. I was finally convinced of this truism by the insanely stupid people in Japan, who made their own critical assembly out of dissolved uranium (by doubling the uranium batch size for faster processing) -- other examples may be found in the nuclear plant lore here in the U.S.
Heh, just what I get for shootin from the hip. I described materials with positive but sub-1 index of refraction. This stuff has negative index and is really new.
The big deal is the difference between two different kinds of speeds of a wave. The wave's group speed is the speed at which the wave energy moves. What determines refractive index is the how a material influence waves' phase speed, an entirely different beast.
Phase speed is the speed at which wavefronts move through the medium, and it isn't limited by the speed of light. A techie example of a phase speed is the speed at which text scrolls across a rolling LED sign (we've all seen them). You can make the text scroll as fast as you like, in principle, because individual LEDs don't have to communicate with one another -- they just turn on and off at set times. You can even make the text scroll faster than light!
Phase speed and group speed are the same in nondispersive media (that is to say, when all wavelengths are propagating at the same speed). In air and vacuum and the like, that's approximately true. But in a dispersive medium, where propagation speed depends on wavelength, they differ. An example of dispersive wave propagation is the motion of ripples on the surface of water. If you throw a stone into water and watch the individual ripples move, each tiny ripple forms behind and overtakes the overall ring of ripples, growing to a large size in the middle and then shrinking again as it gets away from the pack. The tiny individual ripples are following the phase speed, but the energy only propagates across the water as fast as the overall ring of ripples.
How is this related to negative index of refraction? Most materials reduce the phase speed of light, and hence have a positive index of refraction. But spatially coherent structures can have the opposite effect and raise the phase speed above C. You see the effect in microwave waveguides (pipes for steering radio waves) and in radio scattering through of coherent arrays of antennae. You also get it, albeit with much shorter wavelengths, in crystallography -- most crystals have a negative index of refraction for X-rays, as the crystal planes form waveguides for the short wavelengths.
To be honest, from the Reuters writeup I don't know what the big deal is or why UCSD issued a press release at all. Clearly we're not getting the whole story.
Why is it that whenever a M$ product get attacked by malware it's becase of crappy security in the OS, but when linux gets attacked it's because the OS has "finally arrived"? Hmmmm...
Imagine my disappointment when I found a rant that's apparently about "hypocrisy", something entirely different.
English is not the primary language everywhere within 7 hours of Houston. Spanish is a hugely popular indigenous tongue throughout America. To avoid learning Spanish is to deny the very existence of a large sector of the Texan population.
The rub is that this problem -- that Internet users might save their digital stream and thereby copy the music -- is exactly the same problem that is faced by broadcasters! As a teenager, I certainly took great delight in compiling off-the-air cassettes of all my favorite songs. What's different? As near as I can tell, nada.
Sorry to say, I'm just not buying this. Ever taken a long-exposure color photograph by moonlight? Colors come out normal. Similarly, ever looked at moon rock? It's about as close to neutral grey as a rock can get.
Sure, the dyes each represent vectors in the full infinite-dimensional spectral space, and not simply particular wavelengths -- but so long as they're linearly independent (i.e. you can't generate the spectrum of any one dye out of a weighted sum of the other dyes' spectra), they're useful for distinguishing color.
The primary additive colors (R, G, and B) are determined by the spectra of the dyes. You can't pick any set of primary colors you want -- the color wheel was discovered experimentally long before we knew the cellular biology to do direct experiments on the human eye. The primary subtractive colors (C, M, Y) are made by subtracting the corresponding (R, G, or B) from white light -- cyan light has G and B components, but no R.
When you get into detailed color vision, things (as always) get more complex. It turns out that there are no precise primary colors that everyone can agree on, because not everyone uses the same dyes in his cones! There are slight variations across the population, so that the R, G, and B primary colors correspond to different pieces of spectrum depending on who's looking.
Because of the overlap of (for example) the R and G spectra, it's not normal possible to generate a pure R signal in the human retina with any single wavelength of visible light. But we're wired to do the linear decomposition ourselves: in effect, the differential gain is really high between the R and G "raw" channels coming out of our retinas. Cool, eh? As laser pointing becomes more accurate, we ought to be able to stimulate directly our individual cones -- one day somone could perceive "superred" by directly stimulating only the red cones in his fovea. I wonder how different it would look than the more common red?
There's a really interesting overview article on color vision in the Feynman Lectures, volume I. It includes typical spectra for R, G, and B dyes. If I recall right, R and G are actually rather similar spectrally, with somewhat broad humps in the long end of the spectrum, while the B dye has a very different spectrum with a sharp peak near the short end of blue.
There might be colors (shades of blue and violet) that can be distinguished at twilight but not in bright sunlight because of the importance of rods to vision in the reduced light. I keep meaning to go check, but haven't.
That's pretty though-provoking, but I don't think that Star Wars would get as soundly thrashed as the current round of sci-fi nasties.
Aside from providing us with some actual character, plot, and theme, a story must remain internally consistent in order for us (or for me, anyway) to suspend disbelief.
By incorporating situations that are known to current physics and whose solutions are known (or at least obvious), Red Planet incorporates some of reality into its own storyline. By muffing the physics, or by having its characters and organizations make mistakes that ordinary geeks can see through, or by lacking any sort of motivation for the crisis-of-the-minute, RP sabotages the disbelief of its own audience. More importantly, the story isn't good enough to offset the egregious errors in the physics. When the physics is lousy, and the story sucks, and the acting is terrible, there's not much left except some cool eye-candy. SW billed itself as a fairy tale ("A long time ago, in a galaxy far, far away...") and hence had much more latitude with the magic spacedrives and gravity generators and such. That series also seems to remain consistent within its own set of rules (which, admittedly, it can make up as it goes!). More importantly, the first three movies actually had good stories to tell. The stories and characters were interesting in their own right, if a bit stereotyped, and the plots were focused and made a bit of sense. That's why SW didn't suck.
At least the producers of Battlefield Earth had an excuse -- they're $cientologists.
Technical errors which are too glaring to ignore:
The direction and screenplay sucked, sucked, sucked, and it didn't even swallow. Wooden characters; gratuitous ham-handed sex; subplots that are introduced and forgotten in seconds; dumb, stereotyped, dumbass dialog; inexplicable choices for the crew (come on, are these really the best and brightest? Or did NASA just wander down to the nearest pool hall and pick up a few buffoons to head to Mars?); horrible flashbacks; random inexplicable crises; and feeble attempts at heroics are just a few of the more egregious problems with the directing.
Yuck.
My friends and I snuck into "Best of Show" immediately afterward. Much better movie (albeit with no special effects)! We laughed our asses off.
Weisstein certainly wouldn't be in this predicament if his website were being sold in book form: it predates the contract with CRC, and he says that it is not derived from that work (in fact, it's more likely that the reverse is true). Why should his website be treated any differently than any other former publication?
The press release compared the energy density of the new batteries to that of lead-acid cells. It wasn't clear whether they were referring to the energy density by volume or by mass. (My guess is by mass, which is more favorable to them because lead is so effing dense).
Lead-acid isn't all that great for mass density, so don't expect greatly increased range from electric vehicles. The main advantages are that (A) the plastic can probably (eventually) be made cheaper than the lead, and (B) it can be charged quickly (provided that mega-amp charging cables for cars become common, which is another story...)