4 ms·

It depends on the frequency. The brain is mostly water, but there are clear differences in the dielectric constant of air, the skull (bone) and the sweet delici

It depends on the frequency. The brain is mostly water, but there are clear differences in the dielectric constant of air, the skull (bone) and the sweet delicious gray matter inside the cavity. By tuning the frequency of the waves, you can set up resonances in the cavity. For a related effect, see https://www.youtube.com/watch?v=wCrtk-pyP0I https://www.youtube.com/watch?v=wCrtk-pyP0I

xxpor 6y ago
Hm resonance inside the skull isn't something I'd considered, that's a fair point.
- CamperBob2 6y ago
  Because it's not an issue. A bag of saltwater makes a really terrible resonant cavity.
  - emmelaich 6y ago
    You'd think grapes would make a poor resonant cavity too. But you can create plasma with grapes in a microwave oven.
    - the_only_law 6y ago
      Before I act like an idiot and go do this, is there any significant safety risk or major risk to the equipment in doing this?
      - CamperBob2 6y ago
        Should be fine as long as you put a cup of water in the microwave alongside the grape. They aren't really meant to run empty, and microwaving a single grape would be basically running it empty.
    - CamperBob2 6y ago
      Yes, and that's precisely because they are so lossy. It's not a resonant effect. You're just taking advantage of the grape's cross section being roughly a quarter-wavelength at 2.4 GHz, which allows the magnetron to dump a ton of power into it. It's analogous to using a couple of forks to operate a pickle from 120V.
      - MacsHeadroom 6y ago
        >roughly a quarter length Is that not resonance?
        CamperBob2 6y ago
        The same thing would happen with an ideal resistor whose leads formed a dipole of the right length, so no.
ajsnigrutin 6y ago
Due to skin effect, most of the power is absorbed in the outer layers (skin mostly), and that causes 'warm/hot/burning' feeling, before doing anything else to your body.
- K0balt 6y ago
  That's not what the "skin effect" refers to, and penetration of tissue / heating is completely dependent on frequency.
01100011 6y ago
From the report: "Frey reported these symptoms with an RF source transmitting at 1.3GHz(which provides the greatest absorption depth into cortical tissue)..." So they are implying that not all RF is stopped by the skin and some does penetrate deep enough to reach the brain. I don't suppose it will be long until some shortsighted YouTuber tries this as the experiment would not be hard to replicate at all.

xxpor 6y ago

Hm resonance inside the skull isn't something I'd considered, that's a fair point.

CamperBob2 6y ago
Because it's not an issue. A bag of saltwater makes a really terrible resonant cavity.
- emmelaich 6y ago
  You'd think grapes would make a poor resonant cavity too. But you can create plasma with grapes in a microwave oven.
  - the_only_law 6y ago
    Before I act like an idiot and go do this, is there any significant safety risk or major risk to the equipment in doing this?
    - CamperBob2 6y ago
      Should be fine as long as you put a cup of water in the microwave alongside the grape. They aren't really meant to run empty, and microwaving a single grape would be basically running it empty.
  - CamperBob2 6y ago
    Yes, and that's precisely because they are so lossy. It's not a resonant effect. You're just taking advantage of the grape's cross section being roughly a quarter-wavelength at 2.4 GHz, which allows the magnetron to dump a ton of power into it. It's analogous to using a couple of forks to operate a pickle from 120V.
    - MacsHeadroom 6y ago
      >roughly a quarter length Is that not resonance?
      - CamperBob2 6y ago
        The same thing would happen with an ideal resistor whose leads formed a dipole of the right length, so no.

ajsnigrutin 6y ago

Due to skin effect, most of the power is absorbed in the outer layers (skin mostly), and that causes 'warm/hot/burning' feeling, before doing anything else to your body.

K0balt 6y ago
That's not what the "skin effect" refers to, and penetration of tissue / heating is completely dependent on frequency.

01100011 6y ago

From the report: "Frey reported these symptoms with an RF source transmitting at 1.3GHz(which provides the greatest absorption depth into cortical tissue)..." So they are implying that not all RF is stopped by the skin and some does penetrate deep enough to reach the brain. I don't suppose it will be long until some shortsighted YouTuber tries this as the experiment would not be hard to replicate at all.