The collapse of the earth's magnetic field, which both guards the planet and guides many of its creatures, appears to have started in earnest about 150 years ago, the NY TIMES is planning to report on Page Ones Tuesday. Science reporter Bill Broad has filed a report, according to newsroom sources, which explores how: 'The field's strength has waned 10 percent to 15 percent so far and this deterioration has accelerated of late, increasing debate over whether it portends a reversal of the lines of magnetic force that normally envelop the earth." Broad explains: "During a reversal, the main field...