Astronomy Picture of the Day Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer. 2002 November 25 The Earth's Magnetic Field Credit & Copyright: Gary A. Glatzmaier (UCSC) Explanation: Why does the Earth have a magnetic field? The electrical conductivity of the molten plasma of the Earth's core should be able to damp the current magnetic field in only thousands of years. Yet our five billion year old Earth clearly causes magnets to point to (defined) north. The mystery is still being...