War of the Worlds and the EM Pulse

In new Spielberg film War of the Worlds (which ALL of you should go see BTW) a large “storm” creates an EMP and takes out all metro power, cars, even Tom Cruise’s watch stops running. However, a short while later someone is seen using a camcorder, and after that working transportation is procured by replacing the solenoid in a van.

How possible is this? Generally speaking, large-scale phenomenon can be unpredictable, but could a large EMP “skip” some things? And would batteries cease to work?

Perhaps one of the local stores simply uses an old faraday cage to store things in? Or perhaps the movie was influence by some idiot actor?

One tip Bomzaway. If you are going to give away major plot points of new movies like that it’s courtesy to give people a warning. There are spoiler tags available but at the very least give some warning and then insert enough blank lines so we can’t accidentally read what comes next.

Like this.

Hollywood is notorious for ignoring scientific accuracy in films, so don’t expect anything you see on the silver screen to make sense.

That said, EMP is a different phenomenon than ionospheric disturbance. A “storm” which causes ionospheric disturbance, such as sunspot activity, will interfere with radio waves and wreak havoc with communications. An EMP, such as that produced during nuclear weapon explosions, is a short lived but very strong impulse covering the entire frequency spectrum. The important fact to realize is that electric and magnetic fields can only act upon other fields, charged particles, currents and fluxes. Any permanent damage that arises as a result of EMP is a result of the unexpected and strong change of electro-magnetic behavour causing physical damage. Accordingly, if equipment is powered off during an EMP event, the EMP will have no effect since the electric and magnetic fields will have no effect on non-charged or magnetized parts. Conversely, operating equipment may be easily damaged since a large external disturbance can change the behaviour of any electrical current or magnetic flux.

As regards your specific example, this could be explained if the camcorder was off during the EMP and only used afterward, and the solenoid on the bus was operating during it, and was sensitive to field disturbance which damaged it.

More practically, many common devices, even when not in use, employ backup batteries to maintain things like memory, time and date, EEPROM settings, etc. Just as you might damage these things by subjecting them to static discharge (handling chips without having been grounded), an EMP is likely to produce the same problems.

I can’t see an EMP being produced by a storm, though.

What if it’s raining nukes (Hallelujah)?

A large EMP would probably “skip” some things. Any metal box is going to make a natural faraday cage and protect whatever is inside. Metal buildings make natural faraday cages too, much to the annoyance of people who try to use their cell phones inside one.

The power system is probably going to go down, especially if it’s in a large metro area and especially if it’s during the summer, since in most metro areas the power system is pretty close to being overloaded in the summer anyway. You are going to have devices all ove the system tripping, and power systems aren’t that robust (just look at how many minor glitches have thrown the northeast into a blackout over the past few decades). The power may be restored to many areas fairly quickly though. Hospitals and many other buildings are going to have backup power systems that will probably still work.

A solenoid in a van is just a coil of wire with a piece of metal in the middle. I would think it would be one of the least likely components in a car or van to be damaged. The engine computer is much more sensitive to an EMP.

A camcorder is probably going to get fried, but if it was shielded by something at the time (like it was in a metal box) then it’s quite possible for it to have survived.

Automobile bodies are kind of like metal boxes, except they have holes in them. The metal will provide some shielding, but it’s not as good as having a true faraday cage. Some cars are going to be fried and some others won’t just because of the particular layout of metal in them, and their orientation with respect to the EMP.

Batteries are just little metal boxes with chemicals inside them. They aren’t affected by an EMP.

This is not true. An EMP is going to cause large voltages to be induced on conductors in equipment, regardless of whether the equipment is turned on or off at the time. These large voltages are very damaging, especially to semiconductors like computer chips, and computer chips are in darn near everything these days.