Without lightning, mankind would lose a hard-working "cleaner". When lightning strikes, part of the oxygen in the atmosphere is excited into ozone, and the thin ozone is not only odorless, but also absorbs most of the cosmic rays, making the surface of the earth Organisms are not harmed by excessive ultraviolet radiation. The high temperature generated during the lightning process can also kill more than 90% of bacteria and microorganisms in the atmosphere, making the air more pure and fresh and pleasant. This text mainly introduces:. ['Lightning formation mechanism.', 'The harm of cosmic rays to humans.', "Ozone's contribution to humanity.", "Lightning's protective effect on the earth."]