(Forbes) – NASA claimed the magnetic shield is weakening at 5% per decade, so what percentage is left as of today? originally appeared on Quora: the place to gain and share knowledge, empowering people to learn from others and better understand the world. It’s well established that in modern times, the axial dipole component of Earth’s main magnetic field is decreasing by approximately 5% per century. Recently, scientists using the SWARM satellite announced that their data indicate a decay rate ten times faster, or

5% per decade. The trouble is, you don’t have to go into space to measure the earth’s magnetic field. We can and have done that right here on the ground, and we know what the magnetic field is. We also know what it has been in the past from direct evidence—magnetic fields trapped in lavas and other geomagnetic deposits, in pottery, all sorts of things. The strength of Earth’s main magnetic field is currently about 29.5 microteslas, down 5 microteslas, or 14 percent from its strength three centuries ago. READ MORE

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