The Sun-god was delighted to see his son and promised Phaethon anything he requested in the way of proving to his friends that Apollo was his father. Phaethon thought for a while and finally said that he wanted permission to drive the Sun-chariot across the sky for one day. Apollo was shocked and tried to convince his son that it was a very dangerous thing to do and the boy would reconsider his request. Phaethon refused to change his mind, so there was nothing for Apollo to do but keep his word. Phaethon was inexperienced in driving a chariot and it did not take the horses long to realize that an unsure hand was on the reins. First they bolted high up in the sky, far higher than they usually did, in their eagerness to rise above the eastern horizon and reach the top of the great sky dome. It was here that they scorched a great streak across the sky, a streak that became the Milky Way. Meanwhile, Earth's surface became cold because the Sun-chariot was too high in the sky. Next the horses plunged to close to Earth. As they crossed Africa they scorched the ground, creating a great desert and drying up rivers, lakes, and watering holes. Horrified, Phaethon saw ahead a great scorpion (Scorpius) in the sky. Its mighty tail flashed and stung the lead horse. Up went the chariot again, even more wildly than before. Poor Phaethon now realized his foolishness, that he should have listened to his father's warning. Zeus, King of the Gods, decided that it was time to stop this rash youth from causing more destruction. He hurled a thunderbolt at Phaethon, killing the boy instantly and sending his smoldering body tumbling down to Earth. The horses returned to their stable and Phaethon's body eventually fell into the Eridanus River and sank to the bottom. Phaethon had a very devoted friend, Cycnus, the Musician-king of the Ligurians. On hearing of Phaeton's fate, Cycnus plunged into the Eridanus and swam back and forth, diving repeatedly to try to find the body of his friend. His motions through the water made him look like a swan searching for food. Apollo took pity on Cycnus, who died of grief, and raised him to stardom, where he became the constellation Cygnus the Swan.
Phaethon was the son of Clymene, whose husband was the Egyptian King Merops. One day Phaethon's mother told him that Merops was not his father, that his real father was the Sun-god Apollo. When Phaethon boasted to his fiends that his real father was a powerful god, his friends teased him and said that he was not telling that truth. Hurt, Phaethon questioned his mother, who told him: "Go to the Sun-god and ask him yourself if you doubt my word."