The Core

I've just finished watching the DVD of "The Core" and wasn't too impressed by its physics. Phil Plait has a Bad Astronomy review of the film which discusses most of the problems. The most obvious is the premise for the whole film; the core of the Earth stops spinning causing all sorts of problems with Earth's magnetic field.

Now they don't say if it stops spinning completely or just relative to the crust. Either way, that means that a ball of iron the size of Mars just suddenly comes to a stop. Where does all that rotational energy go? Incidentally, it seems that the core takes only slightly less than one day to rotate 360° and so its motion relative to the crust is not as great as you might imagine. According to the Harvard Gazette it takes between 120 and 360 years for the core to 'lap' the crust which works out at about half a mile a day difference. Pretty slow really.

They also have 'beams of microwaves from outer space' which cause havoc in San Fransisco by destroying the Golden Gate bridge. These 'beams' are apparently let in by the collapsing magnetic field. Microwaves are just part of the electromagnetic spectrum - like light and radio waves - and are not kept away by magnetic fields. However, the Earth's magnetic field does keep out lots of charged particles such as high energy protons (usually found with neutrons in the centre of atoms). They tend to get focussed towards the Earth's poles and are what causes the northern and southern lights. Microwaves do reach us from space all the time although most of them are absorbed by water vapour and oxygen in the atmosphere. This fact is well known to astronomers who try to observe the cosmic microwave background radiation (CMB) at microwave frequencies. To get around the problem of absorption they have to find very high and dry sites (Tenerife, Chile or Antartica) or go into space. So losing our magnetic field doesn't cause dangerous 'beams' of microwaves and we probably wouldn't suffer too much from cosmic rays (protons and alpha particles) as the atmosphere does a pretty good job of stopping them too.

I did watch some of the extra features on the DVD which were quite interesting though. I like to see how special effects sequences are built up and there is one section where they describe simulating thousands of pigeons going crazy in Trafalgar square. They start hurling themselves at buildings (the pigeons not the special effects people) and passers by like 'pigeons of death'. However, the Director points out that one of the pigeons is in fact a fish and sure enough if you watch the scene there it is!

Posted in astro blog by Stuart on Sunday 23rd May 2004 (00:58 UTC) | Permalink
[an error occurred while processing this directive]
[an error occurred while processing this directive]