[ganzuul]

I remain in awe that we trust the very cheapest plastic under repeat load and thermal cycling to form a -40dB seal, turning 700W into 70mW. Also, it seems that the outer metal shell of the device forms an active part of the circuit, so if it isn't plugged into a grounded outlet it sits at lethal potential. Then there is beryllium oxide in the thing...

I kind of doubt an independent inventor could bring this to market with today's startup climate.

[jodrellblank]

> "I kind of doubt an independent inventor could bring this to market with today's startup climate."

Especially the kind of inventor who created microwaves for experiments with reanimating frozen hamsters, cough James Lovelock.

(Tom Scott's video "I promise this story about microwaves is interesting" which includes a brief interview with James Lovelock last year at age 101 - https://www.youtube.com/watch?v=2tdiKTSdE9Y )

[dhdc]

A faraday cage does not require grounding to work, but its still recommanded to properly ground microwaves.

Also, unless your electrician had a catastrophic fuck up, the metal cage will never be at live voltage, with or without grounding.

[ganzuul]

The specific scenario I have in mind is a student living on their own for the first time, cooking with a microwave in their room. Many catastrophic fuckups that we were quick to forget took place during this phase in life.

You might take apart a microwave oven and discover that there are actually several pieces of sheet metal in them. Expensive ones connect them by staked wires. The capacitor is usually rated for 2000 volts and it packs quite a punch.

[dhdc]

How does a student living on their own has to do with anything about microwaves having "lethal potentials"? And what does the high-voltage capacitor has to do with sheet metals?

I'm sorry, but I really cannot follow your logic here.

[ganzuul]

Have you ever looked inside a very dirty computer? It's quite simple.

[KennyBlanken]

> I remain in awe that we trust the very cheapest plastic under repeat load and thermal cycling to form a -40dB seal, turning 700W into 70mW

It's the metal grid in the window (with holes smaller than the wavelength of the microwaves), and the metal shell of the cavity, not any "plastic." The same reason the metal grid works is why there doesn't need to be a perfect door seal. As long as as the gap is smaller than the wavelength of the microwaves, it's fine.

> Also, it seems that the outer metal shell of the device forms an active part of the circuit, so if it isn't plugged into a grounded outlet it sits at lethal potential.

The shell doesn't sink RF, it reflects it. GFCI outlets (required in many areas for kitchen outlets) trip at 5mA differential between hot and neutral. No appliance is designed to sink current into ground unless there's an electrical fault.

> Then there is beryllium oxide in the thing...

Beryllium oxide hasn't been used in microwaves for a long time, and it presents zero risk unless the magnetron is smashed.

Recommended reading for you:

https://www.dannyguo.com/blog/my-seatbelt-rule-for-judgment/

https://www.psychologytoday.com/us/basics/dunning-kruger-eff...

Edit: They can interfere with WiFi because a microwave could leak a tenth of a percent of its nameplate power and it would overpower your access point by anywhere from 1x to 10x. Access points can, on certain bands, have radios up to ~1W, but 125-250mW is much more common.

It would also be completely harmless even if you were standing inches away from whatever the source of the leak was. Microwave RF energy only becomes dangerous when it is strong enough to heat up parts of your body that cannot cool themselves quickly due to having little/no bloodflow, like your eyes.

You could put a parabolic antenna on your home wifi AP and standing in that beam would expose you to more RF energy than your microwave.

I don't know why HN suddenly has a "DANGERS OF MICROWAVE OVENS!" boner this week...this is I think at least the second article on the subject of the 'dangers' of microwave ovens.

Regarding "the door gap is a long line" - that would be relevant if the beam were aimed parallel (or close to parallel) with the gap...

[NikolaNovak]

Am I wrong in ignorant understanding that if some radiation leaked, its' effect would largely be about heating affected body parts, which presumably you'd feel as, you know, heat; as opposed to some magical or teryfing "thing"?

In other words, why is microwave leaking worse than e. G. My oven leaking heat? Is potential small amount of microwave radiation In some specific way worse than feeling the heat when you open the oven after baking? I know radiation is a scary term but what is the real actual scientific documented risk here?

I know some pregnant families paid more money for microwave tests than their microwave costs and it never felt legit but I could be wrong.

[manwe150]

IR radiation is stopped very easily, eg by dead skin cells. Higher energy radiation, eg microwaves, can penetrate much deeper into your body and start causing damage to living tissues.

[MertsA]

On the contrary, IR penetrates past the dermis. Also, IR is much much higher energy than microwaves although both are non-ionizing radiation and will only result in heating. The amount of heating you get from the sun spread over a square meter is close enough to the power output of a microwave. Even with the lower attenuation to 2.4GHz vs 240THz the peak heating is still occurring on the surface. You'll probably notice if you're being heated with a couple hundred watts of power. If you don't notice then you're absorbing so little power that there's no chance of any injury. You'd need to raise the temperature of your organs by at least 10 degrees to cause any organ damage and your skin temperature would be so high by that point that you'd already have burns and any sane person will instinctively move away from the heat source causing them pain.

It would take far too long to heat up hot enough to cause more than skin burns and nobody would ever stand there long enough to even get a skin burn to begin with. Any sink presents a much more serious risk of injury than a broken microwave. A hair dryer is more dangerous.

It seems like you might be extrapolating the speed of heating some piece of food and assuming it could possibly heat someone outside of the microwave at the same rate. It can't. The only reason small things heat up quickly is because in a closed microwave the walls reflect the microwave energy many many times before it's eventually absorbed by the food. It's a high Q factor resonant chamber. Effectively when there's little energy being absorbed or escaping the intensity of the microwave radiation is multiplied many times over until the energy being absorbed is equal to the energy being put in. If the door is removed it's just going to bounce out and you get none of the massive jump in intensity that you get with the door closed and only a small 1/2 lb of food inside.

[manwe150]

https://en.m.wikipedia.org/wiki/Microwave_burn

[MertsA]

I'd suggest looking at the section on Adults and Microwave ovens. Over many cases of people being exposed to an open and operating microwave oven the only injuries were burns close to the surface and peripheral neuropathy from placing their hands inside the oven getting a substantial portion of the total power on a small area. The more serious injuries on that page were a result of much more powerful and more intense microwave sources at different frequency bands. If you stick your head into a high powered waveguide, you're going to have a bad time.

In fairness I was surprised to learn that nerve cells absorb a fair bit more than skin and fat leading to quicker nerve damage. All things considered though, I stand by my statements, hot water at a sink presents a much bigger risk given the frequency of exposure and the risk of burns.

[Retric]

> The same reason the metal grid works is why there doesn't need to be a perfect door seal. As long as as the gap is smaller than the wavelength of the microwaves, it's fine.

The issue is the gap in a door normally forms a long line.

The fact they interfere with WiFi should make it obvious the average microwaves faraday cage is far from perfect.

[dhdc]

The point of a microwave to have a faraday cage is not for preventing interference with wifi; the cage is there for preventing the microwave microwaving the user. At an average power of 1000W, even a thousand-fold attenuation (-30dB) means 1 watt/30dBm leaks out, minuscule for humans but enough to saturate typical wifi receivers.

[Retric]

The cage was originally there to make them more efficient, spraying microwaves into the room would mean you food takes a lot longer to cook.

Anyway, I don’t recall all the details but 1W from a microwave is probably an underestimate.

WiFi uses multiple separate frequencies and outside of what a microwave should be producing. So it’s significantly more energy to block it than you might think especially when the hub is closer to the device than the microwave.

PS: To be clear this is still a trivial amount of energy, just annoying when reheating food blocks WiFi.

[ganzuul]

> A Federal standard (21 CFR 1030.10) limits the amount of microwaves that can leak from an oven throughout its lifetime to 5 milliwatts (mW) of microwave radiation per square centimeter at approximately 2 inches from the oven surface.

So you were off by a factor of 200, and you can see that my referencing -40dB of attenuation was an underestimate. I do wonder what details it was that you thought you might recall.

Quite disappointed by HN standards of self-moderation yet again.

[Retric]

You’re way off, that’s 5 milliwatts per square cm times the surface area.

A 1 foot cube, has 6 faces of ~30 cm * 30 cm or 5,400 cm2. 5,400cm2 * 5mw = 27 watts. Of course 2 inches from the surface is a significantly larger box.

Of course that’s a legal maximum, most devices should be well below it.