<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I watched a very interesting show on History the other night. It was about the end of earth, on December 21, 2012. And they bring up all this prophet stuff, then they get to the "black hole" in our galaxy that may "shift polarities" of earth.. What do you all think of this? <br /> Posted by Cassini12</DIV></p><p>This is very popular nonsense that you hear thrown about a lot nowadays. I assume that by "shift polarities" they're refering to the magnetic field of the Earth shifting polarities? There is absolutely no evidence that this is tied to the magnetic field of the Galactic center black hole, nor would you expect it to be. The magnetic field in the center of the galaxy is exceedingly weak (at most 10 milligauss, but probably more like 10 micro-gauss which is about 100,000 times weaker than the magnetic field of the Earth - see
http://adsabs.harvard.edu/abs/2005astro.ph..5244L ). In any case, how could they predict its occurence to within the accuracy of one day? In the past I've heard it said that the reversing of the Earth's polarities would be caused by the Earth passing through the midplane of the Galaxy on Dec. 21, 2012. This is nonesense. The solar system is currently about 8 +- 4 parsecs ( 26 +- 13 light years) *above* the Galactic midplane and is moving *away* from the midplane - see
http://adsabs.harvard.edu.ezp1.harvard.edu/abs/1997ESASP.402..721H ). Even if the solar system were to cross the midplane on Dec. 21, 2012, (which it won't) and the ambient interstellar magnetic field were exceedingly strong (which it isn't), there's really no reason why crossing the midplane of the Galaxy would flip the Earth's magnetic field. I'm guessing that whoever came up with this idea is picturing that the Earth is acting like a bar magnet in the interstellar magnetic field (which it isn't), but in that case the Earth would continue to stay aligned with the interstellar magnetic field as it moved past the midplane without flipping. Finally, even if the Earth's polarity switched on that date, there's no reason to think that it would be catastrophic for life on Earth. Such events have happened in the past (though not due to the Galactic black hole or whatnot), and life continued. To be sure it wouldn't go unnoticed, but I don't see why it would cause the end of the earth. </p><p>As a final note, there's no reason to ever give credence to any sort of "prophecy" - prophecy="making stuff up". Sure sometimes people get it right, usually by making the prophecy extremely vague, or by predicting something that isn't that unlikely to occur in any event, such as that someone in the USA will win a lottery in the next month, or that someone in an audience of a few hundred people has a loved one who is battling cancer. After the fact people will selectively parse through the prophecies and highlight the correct ones without telling you the statistical significance of finding that number of correct "prophecies" out of the total sample that was parsed to find them, and without telling you about the innumerable incorrect ones. A much better way to make predictions is to base them on evidence. </p> <div class="Discussion_UserSignature"> </div>
A video made by me about space and the loneliness in the universe
NASA's Voyager 1 spacecraft finally phones home after 5 months of no contact
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