Terahertz waves (t-cognition)...

Thread Starter

cmartinez

Joined Jan 17, 2007
8,220
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...
 

Papabravo

Joined Feb 24, 2006
21,159
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.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
8,220
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.
Maybe the hard part is not so much creating the waves, but detecting them in a clear and focused manner?
 

Papabravo

Joined Feb 24, 2006
21,159
Perhaps you'd like to rethink this -- and edit your post accordingly. To fail to do so will damage your credibility...
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.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
8,220
... 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?
 

DickCappels

Joined Aug 21, 2008
10,152
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.
 

wayneh

Joined Sep 9, 2010
17,496
I assume that, under that criteria, all frequencies are dangerous depending on their power level?
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.
 

Thread Starter

cmartinez

Joined Jan 17, 2007
8,220
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.
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.
 

nsaspook

Joined Aug 27, 2009
13,087
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.
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
 

wayneh

Joined Sep 9, 2010
17,496
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.
 

joeyd999

Joined Jun 6, 2011
5,237
Scientists estimate that the ocean is 60 miles thick, which is about 10 times deeper than Earth's oceans. But unlike our salty waters, Ganymede's ocean is buried under 95 miles of ice.
Nothin' a few SUVs can't fix... :D
 
Top