Terahertz waves (t-cognition)...

Discussion in 'General Science' started by cmartinez, Jun 10, 2015.

  1. cmartinez

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    I've never heard of this technology before:
    http://www.foxnews.com/tech/2015/06/09/hi-tech-ways-to-detect-mail-bomb/

    First, I'm under the impression that terahertz waves are hard to create. But what really drew my attention is:

    "Another big advantage is that terahertz waves, unlike x-rays, are safe to use in an unprotected environment."

    If this is the case, I can envision a time in which most, if not all, public places will be actively scanned using this technology coupled with face or identity recognition... a very ugly Big Brother kind of future awaits us...
     
  2. Papabravo

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    It's all crap. Terahertz wave are no more or less safe than any other type of EM radiation. It is true they are hard to produce with lumped element components, but possible with microstriplines and 0402 capacitors. Reaching high power levels is also difficult since almost everything is a parasitic attenuator. In the visible spectrum around 475 Thz., the problems change from electronic to optical.
     
  3. joeyd999

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    Perhaps you'd like to rethink this -- and edit your post accordingly. To fail to do so will damage your credibility...
     
  4. cmartinez

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    Maybe the hard part is not so much creating the waves, but detecting them in a clear and focused manner?
     
  5. Papabravo

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    I doubt that very much.
    We know that the FCC has guidelines for exposure to RF energy. The exposure limits are frequency dependent and power dependent.
    https://transition.fcc.gov/Bureaus/Engineering_Technology/Documents/bulletins/oet65/oet65.pdf
    The power thresholds for routine evaluation of RF exposure are lower for 28 MHz to 440 MHz. or high HF to UHF
    If you refer to the table on page 16 it shows that for a power of 250 watts or less no routine exposure evaluation needs to be done for the SHF and EHF bands.
    SHF is 3 to 30 GHz.
    EHF is 30 to 300 GHz.

    We also know that microwaves and infrared will cause heating in liquids and tissue at some power levels, like 1000 to 1200 watts.

    My justification for saying that the original statement was crap was the lack of a specific power level.
     
  6. cmartinez

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    ... My justification for saying that the original statement was crap was the lack of a specific power level....

    I assume that, under that criteria, all frequencies are dangerous depending on their power level?
     
  7. DickCappels

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    Just a note:

    X-Rays can cause ionization which can result a lot of damage, like causing cancer.

    THz RF is not likely to do damage at low power densities.
     
  8. wayneh

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    I was reading up on EM radiation recently and that seems to be the general approach. Non-ionizing radiation (RF, light, etc.) is a risk only because of it's ability to create heat within your tissues, literally cooking you. For instance cellphones are supposed to stay below an exposure dosage rate of 1.6W/kg (I think). That value was chosen for how it relates to the rate of temperature increase in human tissue compared to how quickly human tissue can cool itself through blood flow and so on. In other words it's all about heat, nothing else.

    Ionizing radiation (X-Rays, etc.) is a different story.
     
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  9. cmartinez

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    That was more or less my line of thought too... though I wonder if there's some sort of continuum where a certain frequency will be (to a degree) both heating and ionizing.
     
  10. nsaspook

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    There is but like most things, its complicated. We have evolved to be tolerant of the energy (sunlight) at the edge of ionizing radiation so low levels of non-ionizing radiation" usually are harmless to a healthy person.
    http://www.epa.gov/radiation/understand/ionize_nonionize.html
     
  11. wayneh

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    Yup. We have an enzyme system that accomplishes DNA repair. It's capacity is roughly enough to keep up with the rate of damage we receive from the UV in sunlight. Tanning beds are a bad idea, in my opinion, because they have UV levels far above natural exposure, and far above our ability to repair the DNA damage that occurs.

    Natural exposure to ionizing radiation beyond UV is very slight, and I'm not aware we have any protections other than the DNA repair system I just mentioned. Whatever damage we get from it doesn't prevent us from reproducing successfully, so there's no evolutionary pressure to favor those that might have superior protection.

    If we had evolved in space, we might have a way to handle gamma rays.
     
  12. cmartinez

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    o_O like a one inch thick layer of lead for skin? ... and maybe a couple of quartz crystals for corneas! :eek:
     
  13. wayneh

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    Evolution tends to be more creative!
     
  14. cmartinez

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    Maybe Wolverine's powers of regeneration then... :D
     
  15. joeyd999

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    Thus, a class of organisms called Extremeophiles.

    Edit: Radioresistance in the instant case.
     
  16. cmartinez

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  17. nsaspook

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  18. cmartinez

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  19. joeyd999

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    Nothin' a few SUVs can't fix... :D
     
  20. cmartinez

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    o_O If you say so....

    Capture.PNG
     
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