Stefan Maus on measuring magnetic north

Does a magnetic compass point to the North Pole? The answer is…. not exactly. The direction to magnetic north constantly changes.

One of you asked this question. “Does a magnetic compass point to the North Pole?” The answer is … not exactly. True north is a fixed spot on Earth’s globe. You can imagine Earth spinning, once each day, around an imaginary stick. The North Pole is the spot on Earth’s globe that marks the northern end of that imaginary stick. Magnetic north is something else. It’s related to the magnetic field surrounding Earth. A compass points to magnetic north – which is often in northern Canada. At a recent science meeting, EarthSky caught up with Stefan Maus, who studies Earth’s magnetism at the University of Colorado. He told us that magnetic north is moving at a speed of 50 kilometers – about 30 miles – every year. He said that scientists nowadays use satellites to track the changes.

Stefan Maus: They’re equipped with very sensitive magnetometers that measure the direction and strength of magnetic field.

He said scientists incorporate the measurements into magnetic field models. Many people now use this information every day, he said, while searching for directions on cell phones and GPS units.

Stefan Maus: Another example is that cameras will have magnetic field sensors, because you will want to know later not only where you took that picture, but which direction you took the picture. So now you can integrate it in Google Earth.

He said that our world’s magnetic field might influence your life more in the years ahead, as more and more personal devices are equipped with compasses. Dr. Maus said scientists have to monitor Earth’s magnetic field closely – because the way it changes is unpredictable.

Stefan Maus: When we conduct such surveys over a long time, we can see how field changes globally and study what leads to changes.

He said that there are 3 new satellites that measure magnetic fields: Ørsted, SAC-C, and Magsat.

Stefan Maus: With the new generation of magnetic satellites, we can measure the magnetic fields much more accurately. That strongly benefits devices that use the magnetic field for orientation.

Once every five years Stefan Maus and his colleagues update the three commonly used models of Earth’s magnetic field — the International Geomagnetic Reference Field (IGRF), the World Magnetic Model (WMM) and the Enhanced Magnetic Model (EMM). Maus said all the models do the same thing. They input your location, and the model — like a high-tech compass — tells you the direction of to magnetic north.

Lindsay Patterson