The core tomorrow

[drifter god]

well besides the fact that this movie might be completely unreal, anyone think it'll will be interesting just to watch, i did hear that the special effects are going to be top notch, and it might be fun just to see

[RogueIce]

Even if a 1 gigaton uncontrolled explosion could set the core spinning again (it can't), it wouldn't set the core spinning at the exact same rate it was before, anyway. The inner core comprises about 2% of the Earth's overall mass, which pegs it at around 1.2E23 kg. The Earth's core rotates somewhere between 0.02 and 3 degrees per year. Just for estimation's sake, we'll call it 1 degree per year. That equates to 3.17E-8 degrees per second, or about 5.5E-10 rad/s.

The moment of inertia of a uniform sphere rotating about its center is

I = (2/5)mr^2,

where m is the mass and r is the radius. The radius of the inner core is about 2.6E6 m. So, its moment of inertia is 3.2E35 kg?m^2. Angular momentum is given by

p = Iw,

where w is the angular velocity. Thus, the total angular momentum of the Earth's core is 1.76E26 kg?m^2/s. This is the total amount of momentum that would have to be imparted in order to both stop the Earth's core from spinning (which is the problem in the first place, but no one mentioned where this huge amount of angular momentum traveling in the vector opposite the core's momentum vector comes from ... oh yeah, earthquakes snicker).

1 gigaton is about 4.2E18 J of energy. This is a large amount of energy, to be sure, but it's nowhere near enough to get the Earth's core spinning again at the same rate it was before. The linear momentum of an explosion is given by

p = U/c,

where U is the total energy and c is the speed of light. Even if all the linear momentum of the explosion was collected into a single torque and applied toward getting the Earth's core spinning again (which is can't be; 50% of it will inevitably be radiated away from the core entirely because explosions are omni-directional), that torque would have to move faster than the speed of light in order to generate the required change in angular momentum.

Of course, that's an overly simplistic explanation. But you should get an idea of what would be required to set the core spinning at the exact same rate it was. A nuclear blast won't do it.

However, the characters state that they are going to use a "nukular" blast to get the core going. While the exact properties of "nukular" weapons are unknown, it is certain that nuclear weapons will not get the job done, and that 1 gigaton of anything won't be enough.

Could this be why movies don't try to explain it, they just do whatever?

That would be like, Star Treking the movie (hell, ikt'd be a movie in and of itself!).

Still, set Logic Mode to Off for a moment. Who here thinks it might just be entertaining to watch? Like an action flick: damned if there's a plot, but fun to watch anyway.

[Durandal]

I suppose you could rationalize it by saying the bomb was going to blow up the technobabble that stopped the core from spinning in the first place. Where the momentum of quadrillions of tons of spinning liquid iron went and how it comes back is totally beyond me, though.

Momentum doesn't just disappear and reappear like that. The only conceivable way I could think of to stop the core from spinning would be to literally compress the rest of the Earth inward so that it has a braking effect on the core. Needless to say, we wouldn't even be around to try and fix it if something like that happened.

[Durandal]

Could this be why movies don't try to explain it, they just do whatever?

According to trailers, some weapon that creates earthquakes stopped the core from spinning.

That would be like, Star Treking the movie (hell, ikt'd be a movie in and of itself!).

No, Star Trek movies (the more recent ones) try and explain everything in poorly-chosen technobabble terminology.

Still, set Logic Mode to Off for a moment. Who here thinks it might just be entertaining to watch? Like an action flick: damned if there's a plot, but fun to watch anyway.

All I needed to see was the trailer to know that it's a contrived piece of shit. You've got two clichés right off the bat: the eccentric scientist who's created a ship which can survive temperatures and pressures high enough to crush and melt anything but the most exotic forms of matter and hasn't seen fit to inform the rest of the scientific community of it, and you've got the nerdy hacker kid whose skillz are über-1337 to such a degree that he can control the flow of information through the entire internet by himself. Then Our Heroes must do something involving a giant explosion with "nukular" weapons and save the day.

No, I don't think I'll be wasting $7.50 on that.

[RedImperator]

Momentum doesn't just disappear and reappear like that. The only conceivable way I could think of to stop the core from spinning would be to literally compress the rest of the Earth inward so that it has a braking effect on the core. Needless to say, we wouldn't even be around to try and fix it if something like that happened.

I know that. That's why my solution was imperfect. They could have just dropped a technobabble to the core which causes earthquakes and giant lightening storms that went berzerk and they had to go down and blow it up, but that would have made too much sense. In the plot of The Core, you're witnessing a miracle: they managed to overthink it and underthink it at the same time.