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This should confuse a few people. Group velocity (the apparent speed of a collection of waves - aka wave packet) can go faster than the phase velocity (the speed of a given wave making up a wave-packet).

Physicsweb
American Institute of Physics

Sure as hell confuses me.

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Then they start talking about amplification in optic fibres, but the zero of intensity at the start of a pulse can't go faster than 299792458m/s so it can't carry information (and other such misleading things)...
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The biggest problem seems to be that the energy source available seems to be the light energy from a couple hundred watt lamp.

That's OK, the original did have pics in the linked article.

(Granted, this story has more focus on the actual use, not the original discovery, but you wouldn't know that from the slashdot article)

And I found myself amused by the sentence:
"tests focusing on multiple hits from .50 caliber rounds and improvised explosive devices are in the works. "
So just how long does it take our military to Improvise some Explosive Devices? Or scare up more than 1 .50 cal round? You'd think when they were testing out that one, they might have brought a whole box full.

http://physicsweb.org/articles/news/8/8/9

Nice clickable picture of transparent aluminum here - dated August 2004.

Isn't this the same thing from last year?

http://physicsweb.org/articles/news/8/8/9

The paper itself suggests that observing the waves from such an event would have to wait until the "second generation" LIGOs. I assume by that it means advanced LIGO, which isn't scheduled to start taking measurements until 2013, so don't hold your breath :-). Even so, LIGO is an amazing project - the sensitivities required are enormous, (to quote the LIGO website: "These changes are minute: just 10-16 centimeters, or one-hundred-millionth the diameter of a hydrogen atom over the 4 kilometer length of the arm"), and the payoffs for theory and astronomy are potentially huge.

As to whether gravity is a wave, that's generally agreed (as someone else pointed out, measurements of binary pulsars show this). However, the exact details of general relativity in the strong field regime - that is, near black holes, neutron stars, etc - hasn't been well tested, and there are potentially modifications of general relativity which would give the same predictions for the weak field case (eg, the solar system), but would differ for strong fields. Physics World has a nice article on it.

How about 100 GB of storage capacity for the cost of a memory card ? Magnetic microchips used in cell phones could make them fully functional video cameras. In addition, the chips are non-volatile, so startup lag will become a not-so-fond memory. They use much less power than electronic chips. They can be made much smaller, possibly as small as a few atoms. The examples they have already fabricated "use no silicon and require no multilayer processing and so can be manufactured at very low cost on flexible substrates, while offering non-volatility, radiation hardness and several hundreds of MHz of bandwidth" . They're talking about plastic chips. Pretty impressive.

The technology, which is still being developed, can be classified as "nanotech" and is called "magnetic domain-wall logic" and is based on spintronics. Lots of folks are working on this because many believe that spintronics will allow for great advances in areas from quantum computing to DNA based molecular electronic devices. This particular development is important because it represents the first actual construction of logic gates, which are the basis of computing. So far the group has produced a "NOT gate" and a "11-stage serial shift register / digital frequency divider" in a 200nm design rule. They have also demonstrated the transfer of magnetic information without the use of magnetic fields. This paves the way for hybrid chips with both electronic and spintronic components. Such "3D chips" could contain many times the amount of information possible with current electronic chips. They will run cooler, with short "nanowire" pathways, and have the potential to surpass the performance of silicon chips. Moore's Law marches on.

billy - wonder if the "$100 laptop" guys have their phone number?

http://physicsweb.org/articles/news/8/8/9

They've had it for a year...

I am not sure it's related, but there was a video of carbon nanotubes being in the presence of a camera flash, ending in sparks and fire...

Lightning can be quite bright, much moreso than a camera flash, and if lightning were to strike anywhere near the elevator... lack of hilarity ensues.

Ah yes, here it is. April of 2002: Link 1 - Link 2

These look cool, they're supposed to oscillate to the several 10's of gigahertz.
http://physicsweb.org/articles/news/9/9/9/1

ITER will cost about $10 billion to build with a running cost of about $4 billion over 20 years (although that seems a little low to me). With what it will cost to play on the moon we could build 10 fusion reactors and probably crack that particular technology.

Really? I heard it would be made with aggregated diamond nanorods... (http://physicsweb.org/articles/news/9/8/16/1?rss= 2.0)

Well, you jest, but it's not far from something I happened across yesterday...

This article outlines an idea of how to store up to 5Mb in a fingernail, using lasers. I think maybe they're a little over-optimistic with the idea of storing biometric info there though.

No Flash Photography of the nanotubes please.

More information of hidden black holes and their discovery.

I'm not pretending to have a very good grasp on how this all works, but it seems like these guys have developed some pretty precise control over where the nanotubes get placed by using DNA. Kinda takes 'organic computing' to a whole different level, doesn't it.

The image in the article is a composite of a Scanning Tunnelling Microscopy (STM) image and the cut-out area where they show a computer model showing the structure of the carbon nanotube as it lays on the semiconductor surface. Image

what the hell does it mean though ?

http://physicsweb.org/objects/news/9/8/2/050802.jp g

"(which doesn't exist in this part of the galazy) "

Not sure which "galazy" you live in, but in the my galaxy, we have this :

http://physicsweb.org/articles/news/8/2/1

http://physicsweb.org/articles/news/9/7/4/1

5 megabits can be etched into your fingernail.

A nice writeup is here.

This says it better than I can.

While crying and moaning about dupes and rejected submissions isn't exactly constructive criticism, I have to voice my disappointment with the Slashdot editors, especially Timothy, on this one.

I feel particularly annoyed about this news bit. Why is that? Well, I happened to submit this story early tuesday morning (about 10 am GMT / 6 am EST) and it got rejected. It happens and as such is not a big deal. But the following is imho rather embarrassing.

Not only was this news piece accepted and posted on Slashdot later as someone elses submission, it was actually accepted & posted twice (becoming yet another infamous Slashdot dupe). And in this case the poster of the dupe was no other than Timothy, who rejected my submission.

It seems he initially didn't think this particular news was important and rejected my submission. I knew it was an important bit of news to anyone who follows physics and nuclear stuff, a category which many slashdotters fall into. Potentially and on the long run this could be important news to everyone on the planet who uses electricity.

Anyway, the next day Timothy seems to have decided that a less comprehensive and informative submission on the same subject is worth posting, and as icing on the cake, he does it without even bothering to check the site's own news from yesterday (the already posted story was actually still on the frontpage!) thus creating a dupe story.

Only on Slashdot do you find editors who don't even read their own site's frontpage when posting a news story (to avoid dupes), nor remember that they rejected the very same story yesterday. We're all human and mistakes happen. And I'm sure the editors get swamped by a huge number of submissions, which probably aren't exactly a joy to wade through trying to pick the worthy ones.

However, these sort of things seem to happen a bit more often than they could or should. Perhaps the editors could put a little more time and effort into the process, since many of the previous, similar mistakes seem rather easily avoided (at least to a /. reader like myself).

Ps. Here's my original Slashdot submission about this story just for reference (with a forgotten BBC link added):

After 18 months of wrangling over the construction site of the ITER (International Thermonuclear Experimental Reactor) the participants (China, EU, Japan, Russia, South Korea and USA) finally agreed upon Cadarache in France over Rokkasho-Mura in Japan. Japan withdrew its bid after getting a concessions package deal. The 10 billion ($12bn) project will be the 2nd most expensive joint scientific project after the ISS and hopefully a gateway to a commercial fusion reactor prototype. Construction should begin this year and be completed in 2015.

What this article is talking about is the discovery of superfluidity in a fermi gas-ie, flow without resistance. More information can be found about it from physicsweb

What this article is talking about is the discovery of superfluidity in a fermi gas-ie, flow without resistance. More information can be found about it from physicsweb

Sorry for jumping on you like that. Fishbach must have been misquoted by the journalist because that is a blatantly false statement. Although the Casimir effect calculations above absolute 0 do take into account radiation, that is a correcting factor, not the effect itself. For a lay explanation of the Casimir effect, see this article on Physics Web.

uhhh, string theory is either the theory of everything or the theory of nothing. That's the first thing you learn if you ever take any courses on it or read any of the papers or books on it. So in short you have never studied it nor even looked into it. I don't see how you can make the claim that you do.

Here is a quote you can find from simply googling it.

"String theory is either a theory of everything - which automatically unites gravity with the other three forces in nature - or a theory of nothing, but finding the correct form of the theory is like searching for a needle in a stupendous haystack"

This is the link http://physicsweb.org/articles/world/16/11/8/1

I did not say it was the theory of nothing I said it might be. Which is a totally correct statement

I fail to see why you concluded that any reference frame used for FTL must be backwards in time compared to our own, as light does not travel instantaneously, therefore it is hypothetically possible for something to move faster than light without traveling backwards in time.

See my other comment. It is possible to travel faster than light without moving backwards in time in a given reference frame; it is not possible to travel faster than light in one reference frame without moving backwards in time in some other frame.

Actually, I believe some laboratories have managed to accellerate light to faster than its normal speed, though I can't be bothered to dig up any articles on it.

I assume you're talking about the experiments here. Those showed a "group velocity" faster than light, but not faster than light transmission of mass/energy or information and so no problems with causality (and no utility for FTL travel).

And yes, FTL is often used for ambiance, as, quite frankly, it's rather difficult to have a multi-world society without FTL, as mere communications would take decades at the least, and interstellar trade would be pretty much nonexistant.

"Difficult" is just a dismissive way of saying "would make a fascinating story". See the first books of the "Rissa and Tregare" series by FM Busby for my favorite examples.

Besides, how many writers out there are really capable of describing a civilization fully utilizing a hundred billion stars? Not nearly as many as the number of writers who think they're up to it and are mistaken. Look at the universe-shrinking cameos in the Star Wars prequels: from watching the movies, you'd think Chewbacca was the only Wookie in the galaxy, not one out of a billion.

Of course, the easiest way to have a multi-world society without putting those worlds decades and centuries apart is to put them around the same star. It's ironic that people who think we need FTL to make space small enough to write about don't realize just how big space really is. There is enough free-falling raw material and solar power to support quintillions of people in this solar system alone - surely that's enough for a few interesting stories here too. ;-)

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan./p

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan./p

The original Physics World article contains a lot more information, including a (modern) schematic of 'some sort of a nuclear device' (not the same as the drawing reproduced by the BBC, and not a full scale atomic bomb) that one of the authors claims was actually tested by the Germans in 1945, supposedly killing 'several hundred prisoners of war and concentration-camp inmates'.

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan./p

The original Physics World article contains a lot more information, including a (modern) schematic of 'some sort of a nuclear device' (not the same as the drawing reproduced by the BBC, and not a full scale atomic bomb) that one of the authors claims was actually tested by the Germans in 1945, supposedly killing 'several hundred prisoners of war and concentration-camp inmates'.

The original Physics World article contains a lot more information, including a (modern) schematic of 'some sort of a nuclear device' (not the same as the drawing reproduced by the BBC, and not a full scale atomic bomb) that one of the authors claims was actually tested by the Germans in 1945, supposedly killing 'several hundred prisoners of war and concentration-camp inmates'.

The original Physics World article contains a lot more information, including a (modern) schematic of 'some sort of a nuclear device' (not the same as the drawing reproduced by the BBC, and not a full scale atomic bomb) that one of the authors claims was actually tested by the Germans in 1945, supposedly killing 'several hundred prisoners of war and concentration-camp inmates'.

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan./p

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan./p

Also, the associated article states that the bomb appears to be a hybrid fission/fusion device, which was far more advanced than the two fission-only devices used on Japan.

The original Physics World article contains a lot more information, including a (modern) schematic of 'some sort of a nuclear device' (not the same as the drawing reproduced by the BBC, and not a full scale atomic bomb) that one of the authors claims was actually tested by the Germans in 1945, supposedly killing 'several hundred prisoners of war and concentration-camp inmates'.

f=c/lambda

Now wack your sig generator amplitude up and watch your saber glowing green light. Wave around to impress the ladies. Fair enough, 500-600THz is a bit of a stretch in terms of technology... but we're getting there.

(I'm the same AC as the grandparent post.)

Do you have a source for this? Everything I've read on the web says otherwise. For example, this one:

On the fundamental side, a perfect metallic nanotube should be a ballistic conductor: in other words, every electron injected into the nanotube at one end should come out the other end. Although a ballistic conductor does have some resistance, this resistance is independent of its length, which means that Ohm's law does not apply. Indeed, only a superconductor (which has no electrical resistance whatsoever) is a better conductor.

Two years later Sheng et al demonstrated superconductivity in carbon nanotubes. The experiment was conducted below 20K and the data collected was consistent with the Bardeen-Cooper-Schreiffer (BCS) theory of superconductivity.

For practical applications one wants the superconducting phenomenon to occur at much higher temperature. A material becomes superconducting when its electrons pair up. Normally such negatively charged particles would repel each other, but in a positively charged crystal structure, vibrations called phonons help them get together. In carbon nanotubes, the frequency of these vibrations is very high, which, in theory at least, means superconductivity at higher temperatures.

Two years later Sheng et al demonstrated superconductivity in carbon nanotubes. The experiment was conducted below 20K and the data collected was consistent with the Bardeen-Cooper-Schreiffer (BCS) theory of superconductivity.

For practical applications one wants the superconducting phenomenon to occur at much higher temperature. A material becomes superconducting when its electrons pair up. Normally such negatively charged particles would repel each other, but in a positively charged crystal structure, vibrations called phonons help them get together. In carbon nanotubes, the frequency of these vibrations is very high, which, in theory at least, means superconductivity at higher temperatures.

Some materials have negative refraction.

Which I believe means light travels faster than C through them.

It seems somewhat muddled and misleading to me. Read this (note: Java applet) and this instead.

It's funny how one of the linked articles refers back to this site they way this site refers to it. It's like when you have a mirror and you face it towards another mirror...

...only, Slashdot has never been "physicswebbed"...

With the volatility of crude oil the way it is (heck, it's gone up over 5% today!) for no logical reason (they cite "unseasonably cold weather in the northeast US and Britain" - winter is always cold, and our reserves are higher than they were last year - go figure), any other alternatives that don't require a huge infrastructure change are welcome. Producing "petroleum" from waste is potentially a great way to reduce the volatility of crude oil.

It does nothing, though, to address the issues of using a carbon-based energy currency and the CO2 byproducts from that. It's definitely a novel idea, and the sooner we develop alternatives the better (it's a whole lot more difficult to develop alternatives when your reserves are depleted due to increased periodic costs - i.e., higher cost for crude oil).

* As my physics prof put it: "The first law says the best you can do is break even, and the second law says you can't even come close."

It just has to be the humans, doesn't it!?

One thing I hate about this is how much they (anyone waving this flag) ignore (intentionally) external influences on earth. Look at this quote:

Using modelling techniques, the Finnish team was able to extend data on solar activity back to 850 AD. The researchers found that there has been a sharp increase in the number of sunspots since the beginning of the 20th century. They calculated that the average number was about 30 per year between 850 and 1900, and then increased to 60 between 1900 and 1944, and is now at its highest ever value of 76. ( Source)

Remember the Little Ice Age. Why did it happen? Lower solar output. Today, higher solar output. Hmmm, notice any corralation?

I'm not ignoring the fact that we could be influencing the global climate, but what we are doing might only be 0.1% compared to external inputs to the system.

Hawking presented his solution to the 17th International Conference on General Relativity and Gravitation in Dublin. ...
Hawking also dismisses his previous suggestion that the information might have leaked into a different "Baby" universe. "The information remains firmly in our universe," he told the conference. "I am sorry to disappoint science fiction fans, but if information is preserved, there is no possibility of using black holes to travel to other universes. If you jump into a black hole, your mass energy will be returned to our universe, but in a mangled form which contains the information about what you were like, but in an unrecognisable state.

Read that paragraph. It's not an oxymoron.