Magnetic shield that protects Earth from cosmic radiations.
Earth has a visible atmosphere that protects it from meteorites and small debris bombardment. Earth also has an invisible magnetic field that protects it from cosmic radiations called the Magnetosphere.
Planets having active magnetospheres, like the Earth, are capable of mitigating or blocking the effects of solar radiation or cosmic radiation, that also protects all living organisms from potentially detrimental and dangerous consequences.
Wikipedia, Magnetosphere, 2018.
Without this protective shield life would be impossible on Earth's surface.
[Quran 21.32] And We made the sky a protective shield and they turn away from its sign.
How could an illiterate man who lived 1400 years ago have known that Earth has a protective shield?