Giving out light and heat, the star we call the sun is the source of life on Earth. But this fusion reaction at the center of our solar system also produces space weather that could wipe out the atmosphere and rob the planet of the air we breathe. A complex and dynamic bubble known as the magnetosphere — where magnetic fields produced within Earth rise to meet cosmic radiation, charged particles and fireballs hurled by powerful solar winds — protects the planet against most harmful effects from the sun. Some get through, throwing off power grids, satellites on orbit and radio communications. Some create the stunning atmospheric auroras that trace changes in the magnetic fields near Earth’s poles. Here are some numbers that help explain this lifesaving shield.
4.2 billion
Years since the window started closing for life to take root across the Martian surface. That’s when solar winds began scouring away the carbon dioxide-dominated atmosphere that had kept Mars relatively warm and enabled the presence of liquid surface water. It’s also when the first microbes were developing within the atmosphere of Earth.
6 to 10
How far the magnetosphere reaches out past the sun-facing side of Earth as measured in multiples of the planet’s radius, a total of up to 63,780 kilometers. On the night side, the tail can stretch far past the moon — to some 60 Earth radii. The magnetosphere’s layered shape has been likened to the symbol of Marvel comics superhero Spiderman.
1963
Debut of Magneto as the fickle friend-foe of the X-Men team of mutants in their first Marvel comics appearance. Magneto is said to create his own, personal magnetosphere bubble, using Earth’s polarity as a battery.
3,000
Kilometers beneath Earth’s surface where you’ll find the outer core, an ocean of superheated, swirling liquid iron that acts as a spinning conductor inside a dynamo to help generate the magnetic field.
86
Degrees longitude where the magnetic North Pole currently lies. It’s not the same as the geographic North Pole — which is always on the 90th meridian — but shifts with changes in the magnetic field.
40
Kilometers that the magnetic North Pole moves each year, in a north-northwest direction.
790,000
Years since Earth’s north-south magnetic poles flipped. We’re overdue; the shift historically happens every 200,000 to 300,000 years. Slow degradation of the protective magnetic field precedes this phenomenon and is now underway, some scientists say. A slow return to strength follows. By comparison, the poles of the sun flip every 11 years, the length of a solar cycle.
32
Number of audio speakers at a square in Copenhagen, Denmark, through which the music of the magnetosphere was played during a special October 2022 event. Generated from 100,000 years of data gathered by the European Space Agency’s Swarm satellite constellation, the sound — described as the stuff of nightmares by the ESA — resembles wind, tinkling glass and boards scraping on boards. The soundtrack reaches a crescendo when Earth’s poles nearly reversed in a geomagnetic storm some 42,000 years ago.
60 to 400
Kilometers altitude where auroras form near the poles as the northern lights or aurora borealis and southern lights or aurora australis. They occur when high-energy particles from solar flares collide in the upper atmosphere and descend along the lines of the magnetic fields. Green lights show oxygen struck at a certain altitude, red or blue lights show nitrogen.
Sources: NASA, National Oceanic and Atmospheric Administration, European Space Agency, Royal Belgian Institute for Space Aeronomy, Royal Museums Greenwich