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Comment by ChuckMcM | Hacker News Reader

Nice explanation, does it bother anyone else that you could set up a bunch of antennas such that they could create a lethal 1 cm ball of energy anywhere in the space they can see? Sure they think about powering devices but what about a couple of Watt-Seconds of energy appearing in your frontal lobes? If Perlman can do that its kind of the ultimate 'border' fence is it not?

(I'm tempted to write, "All you would need is an unscrupulous engineer to develop a targeting system ...")

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First of all, your body would likely screw up the interference patterns enough that it wouldn't be a "ball of energy" in the center of the person - it would likely mostly diffusely heat them.

Second, the amount of power to burn a person is many orders of magnitude higher than needed to receive a signal. The transmitters would have to be extraordinarily powerful. I can only see this happening if they plan on making a wireless power transmission service.

Also, a 1cm ball is extremely optimistic, given that LTE frequences have several cm wavelengths. It would also require an enormous number of pCell transmitters to concentrate their transmission into such an area. For communications though, even concentrating into a 20m ball would be a huge improvement over existing technology, so I don't know if there is incentive to place more antennas than required for that.

> Second, the amount of power to burn a person is many orders of magnitude higher than needed to receive a signal.

And how does it compare to the power needed to make a car run? Did you look at the patents in the end?

Have no doubt that we'll increase the frequency untill we can focus it in a few cm sphere. The market will demand that.

I just replied to another thread with this exact same thought, then looked down to see yours. And yes, it is scary... If I understand it correctly, the targeting system just consists of normal receivers hacked to offset their targeting feedback by a distance that would park the energy ball inside the victim.

In any of the applications where this is deployed broadly, that is, where we cover our cities in transmitters, then we'll have effectively given over this remote kill capability to anyone who can do trilateration.

You would basically already do that with mobiles. When people use for talking they keep them <1cm from their head. And while 70mph is indeed great speed people sometimes take high speed trains (200mph) or don't turn off their mobile on an airplane (~300mph in vicinity of ground)

Tin foil hat? (Ok, maybe a Faraday cage hat.)

If this kind of technology were to fall into the wrong hands would we even know? Would it appear as though the victims had a heart attack or stroke?

You would know, if you did this to someones brain it would have lesions and damage. Although you would have to give them an MRI to find it. It would appear as if they had died of a stroke.

The first question that comes to mind is this: how can we defend ourselves from being brain burnt?

Funniest part about that is that a foil hat might very well prevent it from forming in the brain.

That is the funny part, and it would work. If you wore conductive clothing you could create a faraday cage around yourself thus preventing RF energy from crossing that boundary.

On a related note, discussing this offline with some friends they pointed out that the pCell system is getting feedback from the phone about its signal strength, and your body wouldn't be giving that feedback, so you would have to have something tied into the pCell on your person (or not move). Your phone could work for that. The question then is how far away from the phone can the energy be localized while the feedback from the phone would still be accurate enough. That I don't know.

Yea that's one thing I'm not sure about is how easily one could create it without that feedback. I'm sure it'd be possible but certainly more difficult.

You can already cause injuries with phased array radars, right?

Yes (per the guidelines the Navy issues on working around the Aegis system), but not quite like this. Per the discussion about phased array in the article the amount of power you need to do that is many times the amount of powered that gets delivered. This technique allows you to create such an interference node without any excess power from any single source.

What seems to me a more realistic concern is that you could create a beam of energy that would be lethal to an individual device. Brains are typically a lot more durable to EM radiation than electronics.

And more generally, it seems like relying on coordinating devices you don't physically own opens you up to all sorts of new kinds of DoS attack.

Actually if they could make it that small wouldn't it also be useful for surgery? Imagine non invasive surgery.

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