Life in the galaxy seems to be exceedingly rare. So rare that we’ve only ever detected life on one planet: Earth, the one you’re probably reading this from. The expansive universe poses several challenges for burgeoning life forms, and Earth has a unique environment that protects and shelters the millions of living things that crawl on its surface.
Chief among these protections is the magnetosphere. Also called Earth’s magnetic field, the magnetosphere is a magnetic energy field that envelops the entire planet. It’s so wide-ranging that it makes compasses all over the planet point straight to magnetic north. And, as luck would have it, it’s an incredible line of defense against some of life’s most significant threats in the universe.
There are many stars out there in the galaxy; many have died since humanity first hit the scene. When some types of stars die, they let off a catastrophic amount of radiation in all directions. In a few cases, these radiation explosions can be very tight beams called gamma-ray bursts. As far as life on a planet’s surface is concerned, a gamma-ray burst is a cosmic death ray.
If a populated planet gets hit with a gamma-ray burst that isn’t deflected by a magnetic field, life on that planet will wither and die. The high-velocity particles in the blast would shred the DNA of living things on the planet’s surface, resulting in radiation sickness and the end of most life on that planet.
The forces of gravity and hydrostatic equilibrium cause planets to separate into layers based on their composition. In Earth’s case, the innermost segment of the Earth is a molten metal core of nickel and iron. That big swirling ball of metal is spinning along with the planet itself, and that spinning movement generates Earth’s very own magnetic field.
This is all fortuitous for humans and birds and everything else on the planet’s surface. In the (admittedly unlikely) event that Earth gets caught in the crossfire of a gamma-ray burst, the magnetosphere would absorb the worst effects. Likewise, solar flares from our sun aren’t lethal to us, thanks to the magnetosphere.
So, your best friend and guardian angel, beneath your feet all along without your knowledge, is the planet’s metallic core. It’s spinning all the time, generating a force field that keeps you safe. How’s that for the planet giving back to you?