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Science Technology

Terahertz Imaging:Another Way to See Through Walls 145

Posted by timothy from the transparent-society dept.
311Stylee writes: "Wow. I've never even heard of this before, but it looks genuine with a writeup on MSNBC and Space.com . Existing technology is used to measure sea temperatures through clouds via satellite, but newer cameras could be used in a huge array of applications because of their ability to see through walls, clothing, smoke and clouds. Google gets 546 hits on T-rays, inlcuding one from AT+T Bell Labs."
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Terahertz Imaging:Another Way to See Through Walls More

Terahertz Imaging:Another Way to See Through Walls

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  • Come on! This is old news. I'm looking at my monitor right now using "terahertz imaging". AKA, visible light!

    540Thz is right in the middle of the visible spectrum.
    • Quoth the article:
      Low-frequency versions of terahertz waves are known as millimeter waves, and they behave much like radio waves, Star Tiger engineers say. At higher frequencies, the terahertz waves straddle the border between radio and optical emissions.

      Visible light has wavelengths up to around 750 Nanometers. Infrared has wavelengths extending (depending on who you ask) from there up to some number of micrometers.

      At a frequency of 1 terrahertz, light has a wavelength of the speed of light (per second) / 1 trillion.

      c per second is about 300 million meters.
      300 million meters divided by 1 trillion is about 300 micrometers. A typical microwave oven uses a wavelength of about 100 micrometers. [ideafinder.com] (The link has some other helpful info about spectrum, but also some typos.)

      This IS microwave radiation.

      I don't know why they've decided to start calling them "T-Waves." I'd geuss that they're gearing up to put them into airports, and that somebody decided that they don't want to call them "microwave cameras" so that people aren't afraid of being cooked somehow.

      Incidentally, Microwave detection is not a new development; the Military has been using Microwave transmitters since the 70s. What is new about these newer cameras is their sensitivity/accuracy; previous generations of microwave cameras were not sensitive enough to image much of anything.
      • Nothing that the public see's is any sort of really new development. My father once had a very good friend in the military, on the intelligence side of things, and he once made a comment about just how far ahead the military is sometimes. He said take state-of-the-art for consumers, and multiply it by about 10. That's state of the art for government. Believe it when theytell you they could pick your licence plate with a satilite long before you knew they could.
        • My best friends dad worked for a defense contractor. They made the lenses for night vision goggles. We got to play with on of the first ever prototypes, because his dad "took" them home for the weekend.

          The problem was that these didn't have the kill when you suddenly came into contact with losta light. I was trying to spy on the hot neighbor nextdoor, when she turned on her porch light and blam! instant sun in my eyes.
        • Because we all know that the military figured out how to read your license plate looking straight down on your car.

          The thing about satellites is they really can't do much more than look almost straight down.
          • That aint true and you know it. Just use some common sense, Look at a satalite dish. Are they all angled straight up into the air? Nope. Satalites are line of site. Not just at the zenith. If it only worked with stalites at the zenith, your GPS systems wouldn't work.
        • ok if the military can spot anything anywhere why the FUCK cant they find some people in afghanistan... if they can easily sly on everyone at once why cant they seme to locate criminals... come on please take your paranoid hat off and realise that the military does indeed have some nice things but its not some incredibly overwhelming bank of nearly alien technology...
          • Because they have to know what they're looking for and where to look for it. Just because they can resolve a licenceplate on the ground doesn't mean they use the satalite for that purpose very often. I'm sure that in order for something to get resolved with that much detail, they need the object to be stationary and the weather conditions to be ideal. To resolve, and identify a person in a crag in a mountain would mostlikely require some rather ideal conditions that are most likely not present very often in afganistan.
            • what do you knopw about afghanistan??? ok first of all i know a bit about its weather and it is a mostly arid climate, so it is good conditions for satallite imagery... in fact i live in seattle where it is cloudy all the time so afghanistan is much better to spy on then me... but even then a satallite can see through clouds with out much problem... my point was not really specific to afghanistan anyway... the military operates all over the world and it has muchy difficulty keeping tabs on many of its tragets so i dont beleive that they are able to secretly track very many people domestically...
      • Close, but totally wrong.

        Microwave ovens use a frequency of 2.4 Ghz, which is no where near the Thz range.

        This stuff could be called "super-infrared", it's more like optics than it is like radio.

        • Re:Not Visible, microwaves (Score:4, Interesting)

          by dpp ( 585742 ) on Saturday June 15, 2002 @02:48PM (#3708595)

          These wavelengths have the rather ungainly "millimeter and submillimeter" label. There's "far-infrared" at about 100 microns, and this regime runs from there out to, well, about a millimeter. :-)

          I am an astronomer who works with submillimeter wavelengths at the James Clerk Maxwell Telescope (JCMT [hawaii.edu]). In this regime, we're really at the boundary between optics and radio. You can almost think of it as the boundary between whether you treat light as a wave or as a particle.

          Some of our astronomical instruments are radio-style "heterodyne" receivers which treat the light as a wave and produce spectral line information (telling you what molecules are out there and what they're doing). It's a bit like sweeping a radio dial through a range of frequencies and marking the signal strength of all the stations.

          Other detectors treat the light much more as a particle, just measuring the total amount of radiation falling onto a pixel. On the JCMT we have such an instrument called SCUBA (the Submillimeter Common User Bolometer Array). They're analogous to the CCDs used at optical and infrared wavelengths. I'm guessing that the work mentioned in the article refers to detectors of this type, but I could of course be wrong. :-)

    • No, 540 nm (Score:3, Informative)

      by pclminion ( 145572 )
      It's 540 nanometers, not 540 terahertz. speed of light = wavelength * frequency, so wavelength = speed of light / frequency = 3e8/5.4e-10 = 5.5e17 hz.

      That is, 550e15 hz. Light is around 550 petahertz.

      • You are correct it appears. That is the last time I trust a web site [techtarget.com] that "looks credible"

      • Re:No, 540 nm (Score:3, Informative)

        by dpp ( 585742 )

        Erm, but 540 nm = 540e-9 m = 5.4e-7 m, not 5.4e-10m. So, the frequency of 540 nm wavelength light is about 3e8/5.4e-7 = 5.6e14 Hz = 560 THz.

        This is roughly in the middle of visible light (400 to 700 nanometers [nasa.gov]) so light is indeed about 550 THz.

        The article's talking about stuff with a frequency down about 1 THz, though, rather than hundreds of THz (which puts you up near a petahertz).

  • So tell me why the government wants to see through my clothes?

    • Beware Sony Owners Instead... (Score:4, Interesting)

      by Chasing Amy ( 450778 ) <asdfijoaisdf@askdfjpasodf.com> on Saturday June 15, 2002 @08:41AM (#3707367) Homepage
      > So tell me why the government wants to see through my clothes?

      Interestingly enough, people can already see through your clothes--at least, if you're wearing something fairly diaphanous or skintight already, like a swimsuit, or very light-colored clothing. And all they need is an older Sony video camera with NightShot before they put special filters on to prevent the trick from working, or a newer model with modifications...

      Does anyone else recall the breif hysteria when Sony video camera owners realized that using NightShot during the day allowed them to record an image that saw partly through swimsuits and light clothes, and that became public? News broadcasts were definitely playing it up. Sony immediately announced that future video cameras would ship with filters to prevent such imagery...

      IIRC, the problem (or "bonus") was that the IR light emitted by NightShot would travel through thin or light-colored clothing before being either reflected or re-emitted (can't recall exactly how it works...), so that when captured by the lens during daylight capturing, it let one "see" through some clothing.

      There is in fact a whole genre of Internet pr0n dedicated to capturing unsuspecting females in swimsuits or thin white clothing with such cameras. The films have a greenish tinge, like looking through some Night Vision goggles, but do indeed show body outlines, nipples, pubic hair, etc.

      Now, if that can be done with a HandyCam for a few hundred dollars, you know the government with its budget can get a lot more sophisticated and see a lot more clearly...

      • Re:Beware Sony Owners Instead... (Score:1, Informative)

        by Anonymous Coward
        IIRC, the problem (or "bonus") was that the IR light emitted by NightShot would travel through thin or light-colored clothing before being either reflected or re-emitted (can't recall exactly how it works...), so that when captured by the lens during daylight capturing, it let one "see" through some clothing.

        Not quite the case. The camcorder doesn't emit infrared light, it just receives them that are emitted from the target, or anything with heat.
        • Not quite the case. The camcorder doesn't emit infrared light, it just receives them that are emitted from the target, or anything with heat.

          Got a reference to support this? It seems unlikely.

          Remember that the label "infrared" covers a large chunk of the spectrum.. The type used in remote controls, camera auto-focus, etc is just below the visible spectrum. It behaves like visible light, and can be detected with the same sensors (try pointing a TV remote at a camcorder some time; you'll probably be able to see the IR LED flashing).

          A person would have to be on fire to be emitting much infrared at these frequencies. Cameras designed to operate in this range normally have a ring of IR LEDs around the lens, or come with a similar light source.

          Those "heat vision" cameras are operating at significantly lower frequencies of "infrared", and tend to require more exotic components (e.g. chilled sensors, or lenses made out of germanium).
        • Actually it does emit IR light... if it didn't, you would not be able to view non living objects very well, as they produce no heat.

          or conversely if the camera was sensitive enough to see the heat from a table, or a wall, a person would be bright enough to flood the camera.

          just a thought.

        • It does emit ir. I tried one by going into a dark bathroom and turning it on. When pointed to a mirror you can clearly see a lightsource in the front of the camera. It is much like using a flashlight to illuminate and the filmed material strongly reflects this.
      • Does anyone else recall the breif hysteria when Sony video camera owners realized that using NightShot during the day allowed them to record an image that saw partly through swimsuits and light clothes, and that became public? News broadcasts were definitely playing it up. Sony immediately announced that future video cameras would ship with filters to prevent such imagery...

        My understanding is that CCDs are actually more sensitive to IR light than they are to visible light, so camcorders have special filters built into them to prevent the captured image from being distorted by IR light. So, seeing more IR light is just a matter of removing the filter from inside the camera.
    • "the government"
      in its most simplisticly stated form, a "government" is the group of people in a geographic area that has the most & best guns telling everyone else what to do. Everything else about government are rules they write for themselves limiting how they will go about doing what they want to everyone else, including you.
      In a democracy, anybody can join this group who wants to. Either get elected or get appointed or get hired (like an LA cop, for instance).
      Now, back to your question: Any pervert in Gov't who has a peeping-tom fetish, or a Dom sex kink in their brain, can use this to do whatever their perverted minds dream up.
      That's wy the government wants to look thru your clothes.
      Oh, yeah, and there are some minor benefits to law enforcement as well.
      • Your view is simplistic, if currently popular.

        To get elected, someone must get our votes. We can vote for putting limits on what our government can do to us. (As long as the government doesn't take away voting rights...)

        The media can expose those government officials who lie (or "do whatever their perverted minds dream up").

        The point is, I guess, that as long as the system keeps the right to vote, it is possible to put limits on what the government can do to you.
    • It doesn't matter to me. I stopped wearing Dockers long ago.

    • Why do they want to see through my clothes?

  • Lots of boats (Score:2, Funny)

    by noz ( 253073 )
    You mean they don't measure sea temperatures with lots of boats with thermometers as rudders?


  • ...Wouldn't it just be easier to install a window?

    Cheers,

  • Qinteq (Score:4, Informative)

    by 00_NOP ( 559413 ) on Saturday June 15, 2002 @08:33AM (#3707342) Homepage
    For those that don't know this company is what was formerly the Defence Evaluation and Research Agency - ie the UK military's top secret researchers.

    Following the election of Labour to power in 1997 the new government decided that the end of the cold war meant that this operation should make its own way in the commericial world. It's still government owned, at present, but will be sold off to the private sector at some time.

    In effect these are the guys that gave the world radar and much else besides, So they mean business!
    • The fact that they are very much "Q" division is a joke that is not lost on many of the people who work for them

      Yes Bond , very funny, now put the T-camera down, I want to show you theis little beauty here.."

      Brian P

    • That's only half the story...

      DERA was in fact cut in half, and the section deemed to be privatisable is now QinetiQ (minus a large amount of money for the damn silly name).

      The other half still does more secret government work. I think it may still be called DERA, but I'm not sure.
      I suspect the break up would've happened whichever party won the 97 election, since the conservatives were privatisation mad at the time.

  • how long before X10 sells these (Score:4, Funny)

    by Anonymous Coward on Saturday June 15, 2002 @08:34AM (#3707344)
    "For home security purposes - see through walls to see if there is an intruder in your bedroom, or if the baby sitter is carrying a gun under her blouse"
  • See... im NOT cheating if I remove all the walls on the map.

    And I suppose Next they'll make aimbots as well

  • Eh, it's old news... (Score:2, Interesting)

    by Anonymous Coward
    Trex Enterprises has had this for years. It's called "Passive Millimeter Sensing" and they have a product called the Passive Millimeter Camera which was doing this a while ago. Check out there web site www.trexenterprises.com
  • I'll go set up a company that produces shielded ladies' undergarment. :)

    All the perverts ogling with a T-ray gadget at women will make me filthy rich!

    • I believe its been done before. Certainly one company has made IR shielding swim suits to protect against Sony cameras [slashdot.org]. Never actually seen them on sale, only ever heard of them.

  • Half IR, Half MW (Score:5, Informative)

    by Alien54 ( 180860 ) on Saturday June 15, 2002 @08:42AM (#3707371) Journal
    This is one of those things that shares characteristics of both Infrared and Microwaves. The area of the spctrum has been called "far infrared". I can see that it has been under developed. Frrom the AT&T paper.

    The image of a slice of bacon shows different levels of T-ray transparency for lean and fatty areas. Since fat absorbs almost no T-rays, it looks white; meat absorbs roughly 25 times as many T-rays, so it looks dark.

    Many compounds changed the T-rays in characteristic ways, due to absorption or reflection. Molecules and chemical compounds, particularly in the gas phase, showed strong absorption lines that can serve as "fingerprints" of the molecules. Metals and other materials with high electrical conductivity were completely opaque to terahertz radiation.

    The T-ray imaging technique is notable in that it can distinguish between different chemical compositions inside a material even when the object looks uniform in visible light. Also, most plastics are transparent to T-rays, so it can "see" inside plastic packaging.

    I believe they use pulses to illuminate the targets, just so that you don't cook them

    • The image of a slice of bacon shows different levels of T-ray transparency for lean and fatty areas. Since fat absorbs almost no T-rays, it looks white; meat absorbs roughly 25 times as many T-rays, so it looks dark.

      Will this finally inspire most lethargic, overweight privacy-paranoid geeks to get off their asses and exercise?

  • The article seemed to want to get this technology out ASAP. But have we reasearched this field enough? Just as X rays were first thought to be harmless and a miricle of science, could these T-rays prove to be the danger we now know X-rays to be?
    • These waves get emitted by the objects themselves. Contrary to X-Rays you don't need a "light" source to image things. So it's harmless, yes. I mean, they want to watch stars with that thingy too. That would take it's time to send a signal there first and then receiving it's reflection...
      • Ok, I correct myself, there seems to be active and passive imaging... I'd say you'd have to be careful with these Rays as they could warm you up quite a bit...
    • The only way we'll know is if we start testing. As much as it sucks to be the victim of a sience device gone wrong, sometimes it's nessesary. When they were first developing x-rays, I highly doubt any person was even thinking of checking for the possibilities of cancer. They've probably check this sucker for obvious dangers, but the less obvious ones will just have to be tested in the real world.

      As proof of my point, how would anyone in the world know that having a hair dryer could make you dumb enough to use one in a shower unless some moron did so. That's why we have a warning lable.

  • its 7 years old? (Score:3, Insightful)

    by vikool ( 523319 ) <vikas@purBOYSENdue.edu minus berry> on Saturday June 15, 2002 @08:52AM (#3707392)
    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?
    *sig*
    • How do you know that it's not being used as we speak?

      Paranoia has it's own rewards..
    • 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.
    • They probably had to wait for some patent to expire.
  • I seem to recall a similar article a few years ago where they were working on a simar technology to be used for the UN-sanctioned inspections in Iraq.
  • I can see the use of seeing through stuff in the military/police, medicine and for criminals...I still fail to be able to conjure up what this will do for my recreation life. I'm not a peeping-tom so how will this help me unless I'm getting scanned by one of these by a doctor?
  • All they do is use counter-strike!!
  • I guess that over time the costs of such a technology will drop down, and it is interesting to see would it go low enough to be massively affordable. In that case, the laws for regulating it would probably be needed. That will open a completely new chapter in the laws regarding privacy.

  • Airport security and ethical problems (Score:3, Interesting)

    by theolein ( 316044 ) on Saturday June 15, 2002 @09:04AM (#3707441) Journal
    If this is practically possible (which seems strange since it's been around for seven years now) and is not some hoax, then I could see a good use of this at airport security. It seems that it would be able to detect hidden weapons such as guns, xacto knives or knitting needles better than current systems. What would really be a problem would be the security personel getting to look at all the socialy taboo areas of the human body for free. ("Hey Jim, look at those ****, get a load of that fat freak"). I think a lot of people would object. I can see the legal battles already. In the end it might be of most use to some porno director to start a kinky new branch of the business.

  • The Zen of Optics (Score:5, Funny)

    by GroovBird ( 209391 ) on Saturday June 15, 2002 @09:10AM (#3707458) Homepage Journal
    If you can see through everything, what do you see?

    Dave

    • Thank you for the Koan!

      The space.com article looks almost like a hoax. Sounds like they copied everything from a marketing pamphlet. I often see articles that discribe what some technology might be used for, and how much better than other technologies, but it never tells you what the damn thing actually does. The AT&T article is better.

      The T-Ray frequency might be suitable for computation, so i wonder if it's possible to read in T-Ray holograms in real time without a reference beam (by comparing the phase of the wave not only the intensity). It sounds like a complement to X-Ray CT and NMR.

      Even if the T-Rays passed through everything, there would be still a chance, that the refractive index depends on the medium, which leads to a phase shift.

    • You will see spam advertising "thruskirts.com".

      And there will also be a market for clothing interwoven with metallic thread.

      And anytime I see something this obvious with "practically no references in the literature" it always makes the paranoid part of me wonder how much use the [name your own TLA gov org] is already making of it.

    • Re:The Zen of Optics (Score:1, Funny)

      by Anonymous Coward
      > If you can see through everything, what do you see?

      Out Into Infinity, or at least until you rip out your eyes.

      (Cue Ray Milan in "The Man With The X-Ray Eyes")
    • I see only my eyes, staring at me.
  • Guess what kind of new high-tech sunglasses will become all the rage?
  • i use Trays all the time!
  • Next time mars or Coca-cola have a competition where you look under the cap/wrapper to see if you won a prise, they'll know that top-secret army officers can cheat
  • Concealed within his fortress, the Lord of Mordor sees all... His gaze pierces clouds, shadow, earth and... flesh...

    couldn't resist ;)
    • There's something in the movie... 'Build me an army worthy of Mordor'
      This can't be. The Palantír just allows you to gaze far away, it doesn't transport any sound. What Sauron is able to do (according to The Book) is to look upon the one who gazes at him. Pippin, for instance, looked at him and later told Gandalf that 'He just looked at me and I understood'. This happened after Isengard was laid down... oh, perhaps i shouldn't have said this.

      Moderation totals: -1 = Offtopic
  • Scans of homes using infrared technologies has been deemed illegal w/o a specific warrant.

    The same should most definitely appy to this one as well.

  • YOYODYNE LABS DISCOVERS "V-LIGHT" (Score:4, Funny)

    by herrd0kt0r ( 585718 ) on Saturday June 15, 2002 @11:06AM (#3707807)
    NEW JERSEY - YOYODYNE LABS (NYSE: YO) has done it again! First they brought you watermelons that resist squashing, now they discover a visual technology that will allow humans to differentiate between many kinds of meat.

    Using a special set of goggles, wearers are able to experience the part of the electromagnetic spectrum YO Labs is calling "visual light," or "V-light."

    "It's amazing," says one test subject, "I've never been able to appreciate bacon for what it was. With these goggles, I can differentiate the fat layer from the meat layer!"

    Scientists are saying that "V-light" technology will herald a new age. Perfect Tommy said, "It will effect a paradigm shift, the likes of which we've never seen! I know there are many concerns about privacy and stuff, but really, this technology is good. We only use our powers for good."

    Privacy advocates are calling "V-light" immoral. "The ability for people to tell the difference between, say, bacon and corned beef, is a god-given right. But I don't want people to be able to just look into my windows and see me prance around naked with a bowl of jello," says Kent Torokvei.

    But government officials are adamant: "Visual light is a new technology that will enable us to catch criminimables," President George W. Bush said. "With it, we can tell if a terrorist is wearing something trendy, or something not-so-trendy. If we pull back his shirt, we might even be able to see if he has a bomb strapped to his chest. My advisors tell me we might even be able to tell if criminals are black or white, which will aid our police officers in their policy of racial profiling!"

    "I don't give a flying wahoo what the President says," Buckaroo Banzai, head of the Hong Kong Cavaliers, said in a recent interview. "The fact of the matter is, I'm sick of biting into a slice of bacon and finding it being mostly meat. I need my fat. We can give these goggles to the poor and the malnourished, and they can use it to find fat people to eat just by LOOKING at them!"

    "Fat people are a delicious and nutritious meal. I realized that after seeing that unsquashable watermelons did nothing to do to rid the world of famine. They're easy to hunt, and they're easy to bait. This is much better than trying to smash open an unsquashable watermelon."

    And what about T-waves?

    "Terahertz waves? That thing sucks big donkey dong. The real genius is V-light. Not only can I see intimate details, but I believe the technology can be tuned to predict the future somewhat. Here. Take off your pants. Lemme tune my goggles. Ok, I can see your nuts, and I can also predict that you will never die of autoerotic asphyxiation."

  • Great... (Score:4, Funny)

    by tshak ( 173364 ) on Saturday June 15, 2002 @11:09AM (#3707821) Homepage
    Just wait unitl X10.com get's a hold of this technology!

  • Priceless (Score:3, Funny)

    by SkyLeach ( 188871 ) on Saturday June 15, 2002 @12:08PM (#3708024) Homepage
    Linux PDA of your choice: $400
    802.11 or other wireless networking card: $150
    TRay Camera springboard: $25,000
    Being the first human with a tricorder AND the fact that it run Linux: Absolutely priceless.
    • (* Being the first human with a tricorder AND the fact that it run Linux: Absolutely priceless. *)

      I am surprised you are the only one who mentioned "tricorder" (at least in a text search). The description sounds much more like a tricorder (composition analyzer) than something to see thru girls' clothes. Excerpt:

      "AT&T Bell Laboratories scientists have demonstrated an innovative imaging system that uses optics and electronics to "see" the composition of objects - just as X-rays "see through" materials to reveal denser elements inside. They can show, for example, how much fat is in a slice of bacon, how much water is in a leaf, and whether a package holds a banana or a bomb - without touching it."

      We already have X-rays to see thru things, so the uniqueness here is the "point and analyze" capabilities.

      (Unless perhaps if it can see thru things without having the emitter on one side and the receiver on the other, which is what X-rays usually require in practice.)

  • citeseer is a great thing, and this is a great T-wave overview article:
    "Recent Advances in Terahertz Imaging", Mittleman et al [nec.com]
  • I guess we don't need those Sony infrared cameras anymore for some voyeur pr0n.

  • Snow Crash! (Score:2, Insightful)

    by robj ( 18902 )
    How quickly we forget. Snow Crash had LOTS of plot elements that were all about millimeter-wave radar. It's how the robo-dog saw the world, for heaven's sake!

    "never heard of this before" -- sheesh... kids these days :-)
    • I'm going to have to start chipping out some glass knives. And wiring up a pacemaker. And buying a sidecar.
      Then we'll see how long those gargoyles last.

  • An application of astronomy technology (Score:4, Insightful)

    by dpp ( 585742 ) on Saturday June 15, 2002 @02:15PM (#3708483)

    Telescopes like the James Clerk Maxwell Telescope (JCMT [hawaii.edu]) and the Caltech Submillimeter Observatory (CSO [caltech.edu]) have been using these THz waves to do astronomical research for about 15 years.

    THz waves are in the millimeter/submillimeter regime of the electromagnetic spectrum, placing them between the far-infrared and the radio.

    Just like we use infrared light to look at things which are at roughly room temperature, we use submillimeter light - with wavelengths about 10 times longer - to look at things which are about ten times cooler, down to a few tens of Kelvin above absolute zero.

    This includes solar system bodies, comets, and clouds of interstellar gas and dust - the birthplaces of new stars. Just like in the articles, we can use submillimeter waves to see through things that entirely block visible (optical) light.

  • Whatever kind of fancy content they have on their site, it makes my Netscape 4.79 tertallly toominate before the link finishes loading. Neat trick. Are they shutting down my bowser because I won't take their cookies? What a nice way to make friends.
  • I feel like I'm missing something here. The MSNBC/Space article seems to indicate that terrahertz waves are radiated by everything, and the camera simply picks these up.
    'Scientists say T-rays are emitted by pretty much everything. They come from "the human hand, an envelope, someone with clothes on or a comet," says Geoff McBride.'

    Now the AT&T Bell Labs article, on the other hand, says nothing about objects emitting anything, it talks exclusively about generating T-rays from the recording device, and measuring their effects, similar to X-Rays.
    'They transmitted the T-rays through various objects, using an imaging system of lenses and mirrors to focus the signals and to analyze changes in the T-rays as they passed through the objects.

    They characterized the materials by measuring the amounts of distortion - from absorption, dispersion and reflection - of the T-rays passing through to a detector.'

    Are these articles talking about the same technology? Seems to be described quite differently.
    • Actually, the ATT article wasn't the best one to point to. Star Tiger's [startiger.org] website gives the details outlined in the MSNBC/Space articles. Apparently, there are naturally occurring THz frequency waves emitted from "almost everything". ATT seem more interested in an active system similar to radar, with their studies focusing on looking at the reflectance and transmissive properties of various breakfast foods.
  • Check out Star Tiger's site, which includes info about the technology discussed in the MSNBC and Space articles [startiger.org]. While the AT&T link is interesting, it's a slightly different approach to THz wave applications than what Star Tiger's doing.
  • I'm reading Games of State this weekend, and their techies had a device that worked exactly like this. The device used a laser beam pulse lasting 100 femtoseconds, or a frequency in the terahertz range, between infrared and radio waves. The book was published in 1996, and the paperback version has the description on page 147.
  • I just did some calculations powered by windows calculator. First I calculated the energy those T-Rays have. This is given by:

    E = planck*[speed of light]*frequency

    Planck's constant is 6.63e-34 J/s (check Halliday), speed of light is 3e+8 m/s and the frequency is something like 1e12 1/s which is THz frequency.
    Then you calculate the equivalent mass for this energy which is given by E=mc^2 (yes, this formula has some use) or simply make

    h*c*f = m*c*c which is h*f/c = m

    Now pick this mass and divide it my the mass of a resting eletron (=9.11e-31 kg, according to Halliday). By now you should have something around 2,4. Means, one photon of this kind has an equivalent mass of 2,4 resting electrons or one accelerated to some velocity, god know how much.

    I mean, after all, I'm not allowing anyone to scan my body with this T-Rays. It's way more dangerous than X-rays (with which I work) and Gamma-Rays (which are emitted by the sun and hardly reach us). No thanks.

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