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Re: [Phys-L] Finally shark mag. sensing proved.

Not so much insensitivity, but rather polarization of his sense electrodes according to this mil-spec MIT paper  (Historical section) which also offers a way to avoid such effects - with an induction MHD concept  ~ offering an overall efficiency of 70 - 85% (!!) but only in 1 MW + drives (!!)

Notice how every symbol used was listed in a prefatory dictionary page? An object lesson for physics students everywhere.
About the separation of cations from anions, I recall an interesting demonstration where the inverse and opposite movements of charges could be witnessed where such charge carriers were associated with a color. The interface was seen to move slowly along a tube due to the differential velocity of those ions.
Brian W
On Thursday, May 6, 2021, 11:53:40 PM CDT, bernard cleyet via Phys-l <> wrote:

On 2021/May/06, at 20:58, Brian Whatcott < <>> wrote:

Interesting! I may have mentioned visiting a researcher at MBL, Woods Hole long ago. He rigged a shark tank and found that his shark subjects had an exquisitely sensitive electric field sense. The kind that might prove helpful in locating fish. I don't think he connected that result to an (unsuccessful) experiment that Faraday ran in the Thames, to measure the electric filed at either side of a bridge there due to the tidal current. A direct magnetic sense seems more plausible than mapping the electrical effect of ocean currents in the geomagnetic field, certainly.
    On Thursday, May 6, 2021, 06:37:44 PM CDT, bernard cleyet < <>> wrote: 

probably his detector was too insensitive.  Surely an effect w/ the rapidly flowing brine. 

bc  …  never thought of it,  but reminded of magnetohydrodynamic drive. 

OTOH,  what’s the separation of the cat and an ions? 
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