RocketMan on 4/3/2009 at 17:06
I can't be sure without doing some research but somehow that doesn't agree with my gut feel. Electromagnetic induction is completely reversible/symmetric and if a fluid flow of ions (electricity) can create a field (which it can) then the opposite should be true as well.
Displacer on 4/3/2009 at 18:38
Quick and dirty explanation:
Conductors move electrons along a path. Nerves use ions, they have gates in them that let sodium and potassium ions in and out of the cell body. In a nerve pulse gates open at the start of the nerve and pump 3 sodium ions out, and 2 potassium ions in. This results in a positive charge near the gate outside the cell and a negative charge inside the cell. The gates open one after another along the nerve which results in the charge moving along the nerve path. Magnetism inducts energy by moving electrons along the conductor, it does not affect cell gates or ions.
If you want to see the whole affair look (
http://www.biologymad.com/NervousSystem/nerveimpulses.htm) here
RocketMan on 5/3/2009 at 01:03
Thanks for the read, that's really cool. It raises the question with me of how our reflexes are so rapid if we have to wait for a chain reaction of chemical processes to propagate an electrical potential down a line of neurons but I didn't really read the article in it's entirity either.
I think despite this model for ion transport in the body, I still think we are susceptible to the effects of EM fields. It's not really the structure of the conductor or the manner in which charge/potential is developed. Rather it is a fundamental rule that all charged entities, be they ions, electrons or even quarks must communicate the 4 universal forces but particularly the EM force. It's a quantum relationship that depends on nothing else. The fact that we have electrolytic pathways in our bodies means that charge has a few directional pathways to follow when under the influence of an external force or potential. I think a sufficiently strong EM field could definitely disrupt or bias some charge in our bodies. There is certainly an abundant supply of charged particles to participate. The question is, would the effect be coherent and would it be something that causes us harm or would it be random or perhaps benign?
Coming back to system shock, if you recall in ss1 there was a screen distortion effect that came with using emp grenades. This was very likely due to the implants installed in the protagonist but I think it's commendable that they put that in, even though you were still mostly human. SS2 would be that much cooler to me personally if the purely EM weapons had more than a zero effect on biological targets even if it was so much as a light spasm.
Zygoptera on 5/3/2009 at 21:03
Our reflexes are actually quite slow- if you compare them to mechanical equivalents- but in a context where you are primarily competing with other biological entities their speed is fine.
IIRC the reason for metals being effected by EMP is basically the same as why they make such good conductors- they have a pool of 'free' electrons. In contrast, while many solutions (including biological ones) are mildly conductive as well, that is due to charged ions, and there are no 'free' electrons.
You may find it helps to think in terms of mass, or impedance/ resistance. Even the lightest ion has 1000x the mass of an electron, and most of the biologically relevant ones have 30,000+, and even the most conductive biological solutions have resistances far higher than those found in metals.
Disclaimer: Biologist, not physicist.
Al_B on 5/3/2009 at 22:17
I'll start with the disclaimer: I'm an engineer, not a biologist - so this may be off base, but it's what I understand of the subject. All clarifications welcomed.
At sufficiently high frequencies (e.g. X-Ray) an EM field can be damaging because it can cause ionisation - changing the properties of the body chemistry. It may not be practical as a weapon, but it could cause long-term damage.
Low frequency EM fields are far more likely to cause thermal damage particularly if they're at a fairly high power and at a frequency which is resonant with the human body.
There's quite a bit of research at the moment into Terahertz frequencies as these are high enough not to cause heating problems but low enough to still be classed as non-ionising.
In any case, although you could probably construct an EM weapon, it wouldn't really qualify as a 'pulse' weapon and wouldn't work by disrupting neurological communications.
RocketMan on 6/3/2009 at 03:21
Quote Posted by Zygoptera
Our reflexes are actually quite slow- if you compare them to mechanical equivalents- but in a context where you are primarily competing with other biological entities their speed is fine.
IIRC the reason for metals being effected by EMP is basically the same as why they make such good conductors- they have a pool of 'free' electrons. In contrast, while many solutions (including biological ones) are mildly conductive as well, that is due to charged ions, and there are no 'free' electrons.
You may find it helps to think in terms of mass, or impedance/ resistance. Even the lightest ion has 1000x the mass of an electron, and most of the biologically relevant ones have 30,000+, and even the most conductive biological solutions have resistances far higher than those found in metals.
Disclaimer: Biologist, not physicist.
I hadn't considered the inertia of the charged particles. I find your arguement very convincing. If it's still possible to affect humans with an EM field it must be at a very high magnitude.
How abundant are H+ ions in the body? They must be comparitively light (still way heavier than electrons granted)
Al_B: A fellow engineer :D
Yeah man, try standing next to a radio tower for 5 minutes :P I would not want to be that guy!
Displacer on 6/3/2009 at 04:09
Well I wasn't going to continue with this, but I forgot to explain how conductors work.
Using copper as an example, and a wire 1 copper atom in diameter, the way conductors work is at the start of the wire the magnetic field slaps an electron off the first atom, this hits the next atom in the wire and knocks an electron off of it into the next atom and so on down the length of the wire. This is how electric in a conductor works as Zygoptera posted.
Nerves do not use electrons, they use ions of potassium an sodium. I forget which one is which but one of them is positively charged, the other negatively. By pumping out more of one ion than another, the surface is now charged in the area of the ion gate. The next gate opens and so on and the charge is moved down the nerve length. No electrons are involved hence the nerve is not affected by the magnetic field.
You don't need an EMP to prove this anyway. The magnetic field in a MRI is massive, and you walk away unharmed from it.
An EMP Can kill though, if you have a pacemaker for instance.
Zygoptera on 6/3/2009 at 06:09
Quote Posted by RocketMan
How abundant are H+ ions in the body?
H<sup>+</sup> ions do not exist in a practical sense. It's more H<sub>3</sub>O<sup>+</sup>, or even more properly
n water molecules sharing a charge. In any case they are present at very low concentrations as blood's pH is not far off 7.
Quote Posted by Displacer
Nerves do not use electrons, they use ions of potassium an sodium. I forget which one is which but one of them is positively charged, the other negatively.
They're both positively charged, it's the 3:2 ratio of the positive ions flowing through the gate and the membrane's impermeability to negative ions (primarily chloride) which generates the electric potential.
Displacer on 6/3/2009 at 11:51
That's what I get for posting late at night, I already had stated the ion imbalance during a nerve pulse, guess I should read my own posts...
RocketMan on 6/3/2009 at 17:06
Quote Posted by Zygoptera
H<sup>+</sup> ions do not exist in a practical sense. It's more H<sub>3</sub>O<sup>+</sup>, or even more properly
n water molecules sharing a charge. In any case they are present at very low concentrations as blood's pH is not far off 7.
[\QUOTE]
What about acids like HCL? I thought (from my distant chem classes) that when acids dissosciate they for H+ and CL- (or whatever the formula is for the acid in question)? I think stomach acid is HCL isn't it?
