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Comment by username3 | Hacker News Reader

What if you’re around 105-420 people with cellphones radiating 1 watt each?

They can't get close enough to you to matter. The way to think of this is to imagine a bubble around each person's phone. Just like a bubble gum bubble, the bigger it gets, the thinner it gets. So if its dark pink when it is emerging from your lips, it is transparent by the time it is 6" in diameter.

The energy of the cell phone transmitter is spread out further and further as you move way, and because the 'bubble' is both taller and wider, each meter (about 3') you step away from the phone, the signal is 1/distance^2 less powerful. So 2 meters away, 1/4 as powerful, three meters, 1/9th etc.

I like the Tokyo subway image, and others have gone to the trouble of computing people densities[1], if you take their number of 7 people per square meter as a good maximum, then 100 people divide into 7 person groups and you get a box that is about 4 meters on a side (12' x 12'). You're only getting 10% of the energy from the phones that are 3 meters away.

[1] http://www.elsi.jp/en/blog/2015/11/blog1126.html

Again, the energy falls off with the square of the distance, so unless those hundreds of people have very long arms and decide to press their phone against you...

Not trying to be a troll -- Tokyo subways come to mind.

1 watt corresponds to an in-use phone. Heavy data use. Even a call has much lower power. Unless the phone is actively doing something, the cell pings are very brief and use very little power.

You're discounting the fact that cell phones are more used for data than for talking and data is always being transmitted, especially with apps that run in the background.

Nah, the amount of power used for data is just also low when not being actively used. I'm sure some people update over 4G, but not many.

But how many people use their phones for data while holding them against their heads? (Not to mention in a shielded cubicle?)

And how many can even get service in a crowded subway?

most. offline people doing podcasts and games probably don't emmit much less.

Even then, how many people can be within touching distance? 10? 20 if they’re making a real effort? So let’s say 20 within a meter, and let’s say they’re all actively using their cell phones... it’s going to be significantly less than 20 watts, so still nowhere close. If a few hundred people beyond that are using their phones it will add an asymptotically diminishing amount of energy, so you’re never going to come close to the exposure these rodents experienced.

Also, when my phone is in my pocket I'm exposed to 50% of the radiation in one small spot vs. let's say 10% of the antenna's radiation spread across the whole body of the rat. Hopefully they tuned the power in their experiment to account for that.

No, when they talk about watts per kilogram I am pretty sure that they mean these were absorbed. Like they literally built 21 big microwaves, 7 for mice and 14 for rats, and then turned them on: it's no different than your microwave at home, the waves bounce around the walls until they find some water to call home. They're presumably not concerned with any microwaves that escaped the resonator.

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