This thread is about the movie The Core, but since it’s really a science question I decided to put it here instead of Cafe Society. I’m not looking for opinions on the quality of the movie or whether Hilary Swank is sexy or not.
The Core is based on the following scenario: The planet earth has a solid iron-nickel inner core, spinning around inside an outer core of molten, liquid iron-nickel, inside a thick rock mantle. The spinning of the inner core, relative to the rest of the planet, is what creates the earth’s magnetic field. At the beginning of the movie, the inner core has stopped spinning. As a result, the magnetic field is fading. This means the end of the world, because the magnetic field protects the earth’s surface from solar and cosmic radiation, and without it, we’ll all die. Our heros have to travel to the core in a black-box-technology ship to try to start the core spinning again with carefully placed nuclear bombs.
So, here’s what I want to know (scientifically speaking):
Is the earth’s magnetic field really produced by the spinning of the inner core? If so, how fast does the core spin? And in what direction – with the direction of the earth’s rotation, or against it? Does it spin on the same axis the earth spins on? I know the earth’s north and south magnetic poles don’t exactly match with the spin poles – is that because the core’s spin pole doesn’t match with the planet’s spin pole?
Could the inner core stop spinning, or dramatically change its spin, without causing massive earthquakes here on the surface?
If we lost the earth’s magnetic field, how dangerous would that be? Does it really protect us from radiation? How do the astronauts manage when they travel outside the field? I presume both their ships and their suits have some kind of radiation shielding.
Do you think Hilary Swank is really sexy? I think she looks like a younger Julia Roberts.
The interviewed scientist says that if the dynamo that generates the field stopped it would take on order of a billion years for the field to die, but he doesn’t explain why.
It is probably because the currents that generate the field have also magnetized materials like iron in the earth. This is like if you wrap an iron nail with a current-carrying wire for a while and then shut of the current, the nail continues to be magnetic for some time.
But what would happen if the field really did disappear? Speculation aside, we do know from geological signatures that the field has reversed many times in the earth’s history. It is reasonably to suppose that these reversals take place over thousands of years and so there must have been significant periods of middle time in which the field was negligible. These periods do NOT correlate with mass extinctions, so it is probably not something to worry about.
Okay, here’s a related question: If a celestial body has no liquid center, but is one solid piece, so there’s nothing to internally spin, does it lack a magnetic field? Earth’s moon, for instance. I don’t think there’s any molten magma inside the moon, and there never was. Does the moon have a magnetic field?
Saturn , Neptune and Uranus have smaller fields.
The reversal of the Earth’s field happens every million years or so, perhaps taking a thousand years of less (I think)
There isn’t a good mechanism that explains how this reversal happens, or even how the Earth’s field is generated.
Perhaps it is a switch between coherent rotation anad chaotic rotation at a specific depth - (just guessing here) but the core doesn’t - can’t - stop spinning.
Possiblty there might be an increase in radiation during the transition period, perhaps causing environmental stress, but these events haven’t been linked with actual extinctions.
At the very least the northern lights would be affected.
I would think some of the charged particles from the sun would rain straight down onto the planet, disrupting communications and overloading HT lines.