In The Days of the Comet by HG Wells

In the Days of the Comet is a HG Wells novel that employs the vapors of a comet to bring about a profound and lasting transformation in the attitudes and perspectives of humankind.

As the Comet hurtles toward earth, mankind is too busy hating, scheming and killing to care but when the comet passes so close that the tail passes i the atmosphere, everyone becomesd profoundly different than they were before.