In 312 AD, the (soon-to-be) Roman Emperor Constantine converted to Christianity and eased the long-standing persecution of Christians by the Empire.
Now, a team of geologists believes they've discovered the cause of Constantine's conversion. A meteor that impacted in central Italy. From the article, here is the historian Eusebius' contemporary (to Constantine, that is) account of the cause:
“...while he was thus praying with fervent entreaty, a most marvellous sign appeared to him from heaven, the account of which it might have been hard to believe had it been related by any other person.
“...about noon, when the day was already beginning to decline, he saw with his own eyes the trophy of a cross of light in the heavens, above the Sun, and bearing the inscription 'conquer by this'.”