Q & A: Earth's magnetic shield

I have heard that the magnetic poles of earth sometimes inexplicably reverse themselves every 70 to 150,000 years. This magnetic field sheilds us from the suns solar wind which could stip our planet of atmosphere and water as well as irradiate all living and otherwise things on earth.
During the transitional phase of pole flip I understand the earth would be exposed to the suns deadly solar wind because of the shift in the angle of the magnetic sheild to the solar wind. My question is could it be possible to build an artificial magnetic sheild on earth to protect ....say a house. Would it have to be an electro magnet or could any non electric magnet work?
What kind of strength and distance would this field have to be between us and the partical stream ?
- Clyde (age 43)
sudbury,ontario,Canada

I wouldn’t say the switching is completely inexplicable. People have done a decent job of modelling the dynamic processes that keep the Earth magnetic, including occasional reversals. By the way, I’ve heard that the signs indicate that the next reversal is coming in a few thousand years.
The consequences are not as dire as you fear. These events have happened many times without drastically wiping out life. Research is going on to see if the effects of the extra radiation have had a major impact on biology. Obviously, it would be a problem for people alive during the reversal.

A much more immediate problem arises from our own activities, which are already creating a huge "extinction event" of the sort seen every hundred million years or so, not the sort of piddling problem that may happen every hundred thousand years or so.

Assuming our descendants survive global warming, etc, then they probably will not have extraordinary problems with the extra radiation. Most of these charged particles (the only types deflected by the magnetic field) can be easily stopped by walls or even clothes.

Mike W.

p.s.
Yes, in principle one can build a magnetically shielded house but it would be ungainly to say the least and really not worth the while since, as Mike hinted, the protons in the solar wind loose almost all of their energy traversing the earth's atmosphere. 
A more dire circumstance would be if the earth's magnetic field did not reverse itself but simply died out to zero and stayed there.  Then over the course of long time, millions or billions of years, the solar wind erodes the atmosphere.   An example is the planet mars which has essentially zero magnetic field. The atmospheric pressure of mars is about one tenth that of the earth.

LeeH

(published on 10/22/2007)

So Mike W., please tell us the names of any reputable scientists you know who are predicting that we will not survive the warming of the planet by a few degrees.

And could you please write a short essay of what, in your opinion, if anything, was wrong with how the Catholic Church lied to people about science, in order to promote a belief system that was contrary to the best science of the day.
- Bob
Berkeley, CA, US

Wow, that's a pretty intense reaction to the phrase "assuming our descendants survive global warming etc...". In fact, I think that assumption is highly probable. As I've written elsewhere on this site (http://van.physics.uiuc.edu/qa/listing.php?id=830), we're a very adaptable species which means that we are likely to survive quite a bit of change. However, the vast majority of species die without leaving descendants, so I didn't want to just assume beyond a doubt that we would survive no matter what happens. Hence my cautious caveat, which you manage to interpret as a lying assertion that we would probably not survive! I shouldn't be too mad, my wife always warns me to write so that no one could possibly misunderstand.

So what are the scientific accounts that make it a little hard to be completely confident? One possible worst-case warming scenario (which I think I’d read shortly before posting that answer)  is discussed in a recent Scientific American article by Peter Ward: http://www.sciam.com/article.cfm?articleID=00037A5D-A938-150E-A93883414B7F0000
He makes a case, not by any means proven, that the biggest mass extinctions were caused by extreme climate events inducing major changes in atmospheric chemistry. The best science of this day on this question includes large uncertainties, and it would not be honest to pretend to a degree of certainty which is not justified.

Mike W.

(published on 08/24/07)