The Case of Earth's Incredible Shrinking Field

Naval logs reveal a weird history

3 min read

Earth’s magnetic field has been monitored carefully since the 1830s, when the German polymath Karl Friedrich Gauss invented a way to measure its intensity. Since then, the field has decayed at the ­startling rate of about 5 percent per century [see photo, "Tangled Story"]. Has Earth’s field been in a spiral of decay for longer than that? Or do we happen to live in a period when the decline is particularly striking?

Now British geophysicist David Gubbins and his colleagues have an answer from the most unlikely quarter: data hidden in the logbooks of ships that navigated the planet’s oceans in the 16th, 17th, and 18th centuries. The results have allowed Gubbins to build a remarkable picture of the behavior of Earth’s magnetic field in the centuries before detailed measurements were possible.

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Top Tech 2023: A Special Report

These two dozen technical projects should make significant advances in the coming year

2 min read
Top Tech 2023: A Special Report
Edmon DeHaro

Each January, the editors of IEEE Spectrum offer up some predictions about technical developments we expect to be in the news over the coming year. You’ll find a couple dozen of those described in the following special report. Of course, the number of things we could have written about is far higher, so we had to be selective in picking which projects to feature. And we’re not ashamed to admit, gee-whiz appeal often shaped our choices.

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