A Tear in Earth's Magnetic Field?

The Breakdown takes on The Core

In keeping with our movie physics theme of the past few weeks, it seems appropriate to take a look at the trailer from the action "science" disaster film The Core. As with Armageddon and its deadly asteroid, The Core starts with an interesting premise -- the possible disappearance of the Earth's magnetic field.

The magnetic field shields the majority of the atmosphere from incoming charged particles (electrons and protons), redirecting them along the field lines towards the magnetic poles.

We can forgive the film for presenting an exaggerated view of the resulting cataclysmic natural disasters. It is really just an old-fashioned disaster movie, after all. However, don't be fooled by the realistic-sounding scientific explanations, which more often than not are just plain incorrect -- sometimes even when they have no effect on the plot. For example, at one point Dr. Keyes (Aaron Eckhardt) explains to his geophysics class that as a wave passes from one medium to another its frequency changes. Not true. It's the wavelength that changes. A small detail? Maybe. But how hard is it to at least look that one up?

Once The Core gets cooking, we can actually find so many outlandish scientific absurdities that it leaves our head spinning (even if the Earth's core has stopped, as it does in the movie). It's entertaining to pick them out on your own, and anyway we don't have time here for a comprehensive list.

However, as an example, pay attention to what the world-famous geophysicist Dr. Zimski (Stanley Tucci) is saying about 45 seconds into the trailer, in his explanation to the military leaders of the free world. Zimski informs us that when the magnetic field collapses we will "literally be cooked by microwaves"! (In fact, later in the film we are treated to a glimpse of how deadly these microwaves can be when they fry the Golden Gate Bridge through a "tear" in the magnetic field.) It has the ring of plausibility. Microwave ovens do a pretty good job of heating up last week's leftover chicken wings, after all.

But the interesting thing about microwaves is that they are a form of electromagnetic radiation, just like visible light. Electromagnetic radiation has no charge! The Earth's magnetic field shields the atmosphere from charged particles. It has no effect on electromagnetic radiation. If the Earth's magnetic field disappeared tomorrow, there would be absolutely no difference in the amount of microwave radiation impinging on the surface of the Earth. You wouldn't be cooked any more than you are now when you go outside on a sunny day.

Because this is a major plot device, we just thought it might be worth pointing out.

Adam Weiner is the author of Don't Try This at Home! The Physics of Hollywood Movies.