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In what could potentially be one of the most, or least, significant actions of his term in office, President Trump Tuesday signed an Executive Order requiring federal agencies to strengthen critical infrastructure against ElectroMagnetic Pulse (EMP) attacks.
EMPs occur for a variety of natural and man-made reasons including, most notably, Nuclear Explosions and Coronal Mass Ejections (CMEs), either of which could potentially take out entire sections of the country's electrical grid and other infrastructure and capabilities, requiring require years or decades to recover from.
Members and supporters of the decommissioned US Commission to Assess the Threat to the United States from Electromagnetic Pulse have long warned of the possibility of an EMP attack, with some individuals, such as Peter Pry, who previously led the congressional EMP commission, asserting that an EMP attack on America could kill off 90% of the US population.
This is because a man-made EMP has the advantage of being highly asymmetrical. A small country able to pull one off would cause potentially massive disruption to a large tech dependent country such as the United States.
Past EMP related coverage here, here and here
(Score: 4, Informative) by Anonymous Coward on Friday March 29 2019, @12:01PM (3 children)
that's not an EMP!
I'll be pedantic in the following.
an EMP is a pulse: basically a discontinuity in the electromagnetic field. technically you can decompose it into a short superposition of frequencies, from long radio up to visible and/or beyond (it probably depends on the source), but essentially it's just a big sudden change in the electromagnetic field.
any change in the surrounding magnetic field induces currents in electrical conductors, that grow with the size of the conductor.
the electric grid is vulnerable because it's made from very long conductors.
this is why you're not allowed to put copper wires/aluminium foil in the microwave: big currents are induced in them and bad things happen.
if the moon is glowing red it means there's a large amount of radiation coming from the sun, or hot matter from a big enough coronal mass ejection has hit it.
large amount of radiation is a sustained high amplitude electromagnetic wave (not a pulse). you may liken it to many EMPs one after the other if the amplitude is high enough, and it can certainly cause the same effects that an EMP can cause, but it's much worse than an EMP.
sustained high radiation acts on nonconducting materials, not just conductors.
this is why you can put regular food in the microwave and it still heats up.
(Score: 0) by Anonymous Coward on Friday March 29 2019, @04:27PM (1 child)
Really? You're not allowed to? Who says?
Pretty much the worst thing that can happen by sticking aluminium foil in the microwave is that you'll make a bit of ozone in the microwave. Ozone is a bit nasty so it's probably a good idea to do this in a well ventilated area and don't stick your head in the microwave immediately afterwards. Probably wise not to use the same microwave oven you use for food preparation.
It's recommended to also put a glass of water in the microwave which acts as a dummy load so less power is reflected back into the magnetron, which should extend its lifetime.
Microwave ovens don't really work on this principle. Microwave ovens do not present particularly high energy radiation.
Regular food heats up in a microwave oven because regular food contains polar molecules. Such molecules will tend to rotate in order to line up their imbalanced charge with an applied electric field. A microwave oven presents a continuously changing electric field, which causes these molecules to vibrate. This effect is what causes the energy transfer and thus heats up the food.
(Score: 2) by Immerman on Friday March 29 2019, @06:19PM
> You're not allowed to? Who says?
The same people who say you're not allowed to put anchovies in ice cream, I'm sure.
Fire and explosion can also result, which can rapidly become a much bigger problem if you're not in the room at the time. I once saw someone unthinkingly heat food on a plate with gilded trim. The gilding was vaporized and shattered the plate. I'd be surprised if nothing more toxic than ozone was produced in the process, and the microwave was never quite the same.
Of course, you can also use a normal microwave oven to melt blocks of aluminum for casting, but you want to modify it to survive the temperatures and currents generated first, and operate it in a well-ventilated and fire-resistant area, just in case.
As for normal heating - my understanding is that the primary mechanism of heating is the absorption of microwave photons by (primarily) water and oil molecules, rather than their mechanical agitation by a changing electrostatic field.
(Score: 0) by Anonymous Coward on Friday March 29 2019, @11:06PM
Radiation doesn't "come from the sun". That is like saying the sun revolves around the earth, totally wrong reference frame.
The speed of light is zero (photons do not age), the rest of the universe moves around the radiation at the speed of gravity/matter: c.