If you've been to the movies lately, you know how incredibly realistic today's special effects are. They can make just about anything you can imagine look like it really happened. Powerful computers and 3D software can create massive explosions, alien invasions and imaginary space battles that look totally real. They can make exact replicas of real cities and then show them being destroyed in all sorts of ways. Thanks to this technology, there's a whole category of movies about natural disasters big enough to destroy Earth.

So could the disasters we see on the big screen really happen that way? Let's see …

The Core
In the movie The Core, the Earth's core suddenly stops rotating. This unleashes harmful microwave rays that collapse bridges, interrupt radar systems, and even generate super-electrical storms. How likely is it that the core would suddenly stop?

The Earth's core is essentially a huge ball of iron. It's about 4,350 miles across, roughly the size of the planet Mars. In its rotations, it generates a massive amount of energy -- the same amount that comes blasting out of the sun in about a minute and a half. Getting the core to stop would require the same amount of energy that keeps it going. In the movie, they get it moving again with a big explosion. In reality, it would have to be an explosion hundreds of millions of times more powerful than all of the nuclear weapons that exist today put together. Something like this is highly unlikely to occur in nature. If it did, the rotation of the Earth's core would be the least of our worries.

The main reason the movie shows the core stopping is to create a situation where the Earth's magnetic field goes away. This is what causes "deadly microwaves" to be released on the world. In fact, the movie's writers didn't need to do all that. The Earth's magnetic field really has reversed several times in history on its own, without the core losing its spin. When the magnetic field reverses, the North Pole becomes the South Pole, and there is a period in between where there's no magnetic field at all. This happens every several hundred thousand years. Scientists aren't sure why it happens.

Let's say for the sake of argument that the core did stop spinning, and that we all weren't wiped out in the process. What about the harmful microwave rays we see in the movie? The microwaves they're talking about in the movie are the same kind a microwave oven uses to cook food. They are weaker than the light we see with, and are dispersed rather than concentrated like a laser. On their own, they can't do much of anything.

The other problem with this scenario is that the Earth's magnetism doesn't affect microwaves coming to Earth. From a scientific perspective, this movie got it all wrong.