magnetic-field

In 2017, NASA deliberately destroyed the Cassini spacecraft by plunging it into Saturn. Before it died, it made 22 passes through a region no spacecraft had ever entered — the 2,000-kilometer gap between Saturn and its innermost rings. The data it collected upended what scientists thought they knew about the rings' age, mass, and origin, and revealed a magnetic field so perfectly symmetrical it has no right to exist.

In 1896, Pieter Zeeman placed sodium flame between magnet poles and watched spectral lines split. The experiment revealed the electron's charge-to-mass ratio and earned the 1902 Nobel Prize in Physics.

Radioactive decay provides Earth's internal heat, drives plate tectonics, and powers the magnetic field. If it stopped, Earth would cool, tectonics would cease, the magnetic field would die, and life would face increased radiation. Over billions of years, Earth would become a cold, geologically dead world.

Earth's magnetic field has reversed polarity hundreds of times in the past 200 million years — and it could happen again. During the transition, the field weakens, more cosmic radiation reaches the surface, and compasses spin uselessly. But it isn't the apocalypse some claim.

Every 11 years or so, the Sun's magnetic activity rises and falls in a cycle that astronomers have tracked since Galileo's era. The solar cycle sets how many sunspots, flares, and coronal mass ejections occur, and it shapes space weather at Earth.

Earth spins at 1,674 km/h at the equator. If it suddenly stopped, supersonic winds would devastate the surface. If it slowed gradually, the consequences are still severe — a 6-month day, ocean redistribution, and a collapsing magnetic field.

A magnetar is a neutron star with the strongest magnetic field known — lethal from 1,000 km away. Here is how magnetars form, why they erupt in giant flares, and how one was caught producing a fast radio burst in 2020.