To the scientific professionals, a theoretical ?

The rotation of the Earth is caused by angular momentum, not polarity.

Polarity has switched in the past. Rotation hasn't. A sudden change of rotation would not only require tremendous amounts of energy (as you have to accelerate the entire mass of the Earth) but would cause widespread devastation to the surface.

We know rotation hasn't changed because we can't make energy from nothing. Where would the energy needed come from?

It would actually be a calamity not seen since the impact that created our moon, perhaps beyond that. The entire surface would probably melt from the acceleration, and our atmosphere would probably be stripped completely. The Earth would never sustain life again.

And for clarification, the polarity isn't caused by the Earth's rotation either. It's caused by ionized particles in the mantle.

Earth has a rotational kinetic energy of 2.138×10^29 J. This Wikipedia article walks through the calculation. The whole world's nuclear arsenal is about 5 gigatons of TNT. One gigaton of TNT is 4.184 x 10^18 joules. So all the nuclear weapons in the world have about 2.092 x 10^19 joules worth of energy. That's one ten-billionth of the energy the spinning Earth has. Sort of a cool fact.

Polarity shifts every million years or less. If it caused a calamity every time, there would be no life developed beyond single cell organisms. If there is any danger from polarity shifts, it's from solar radiation and not a change in rotation.

Here's an article on the topic.

Quote:

Originally Posted by Happy Camper 

If the polarity of the earth flips, does the rotation also reverse?

No.

Quote:

Originally Posted by Head Injury 

Polarity shifts every million years or less. If it caused a calamity every time, there would be no life developed beyond single cell organisms. If there is any danger from polarity shifts, it's from solar radiation and not a change in rotation.

 

Here's an article on the topic.

Exactly.  I can think of some animals (sea turtles, for example) that navigate using the magnetic field, and they might have problems and/or go extinct, but most of the risk would come from the weakened magnetic field as it realigns.  The purpose of the Earth's magnetic field is to direct charged solar radiation around the planet, and with a weaker magnetic field, more of that radiation will get through.  It will not mean the end of all life on Earth though.

Also, compasses probably won't work right for a while.

arguably rotation does change.

rather the frame of refference reverses hence the manner by which we define rotation has changed.  really im just being an arse but i cant decide if the op is too though.

Quote:

Originally Posted by mark2410 

arguably rotation does change.

 

rather the frame of refference reverses hence the manner by which we define rotation has changed.  really im just being an arse but i cant decide if the op is too though.

The frame of reference only changes if you describe the Earth's rotation as "eastward," and even then it only changes with respect to magnetic north.  As it is, magnetic north != true north, though only by a few degrees depending on location.  A polarity reversal would just make the difference between magnetic north and true north roughly 180 degrees.