Ellis Davidson has given a superb account of the northern myths and we refer the reader to her book for details. Perhaps the following extract dealing with Ragnarok, the end of the world, reveals clearly enough the history of comets as we now understand it.
"There Loki must lie until Ragnarok, the time of the destruction of the gods. Thisfearful time will be ushered in by many portents. First there will be great wars through the world, and a time of strife and hatred between men. The bonds of kinship will hold them no longer, and they will commit appalling deeds of murder and incest. There will also be a period of bitter cold, when a terrible pursuing wolf catches the sun and devours her; the moon too is swallowed up, and the stars will fall from the sky. The mountains will crash into fragments as the whole earth shakes and trembles, and the World Tree quivers in the tumult. Now all fettered monsters break loose. The wolf Fenrir advances, his great gaping jaws filling the gap between earth and sky, while the serpent emerges from the sea, blowing out poison. The sea rises to engulf the land, and on the flood the ship Naglfar is launched, a vessel made from the nails of dead men. It carries a crew of giants, with Loki as their steersman. From the fiery realm of Muspell, [the south?] Surt and his following ride out with shining swords, and the bridge Bifrost is shattered beneath their wei ght. His forces join the frost-giants on the plain of Vigrid, and there the last battle will be fought between this mighty host and the gods.