Some historians of religion have taught that Hanukkah is another ancient celebration of the winter solstice. However, the winter solstice can also co-occur with the full moon (yielding a bright, moonlit night.) Hanukkah is different. Hanukkah too, occurs near the winter solstice (when the nights are the longest), but it also begins on the 25th day of the lunar month and ends at the time of the new moon, a sliver of light. With each night of Hanukkah, with the waning of the moon, the nights get darker and darker. And as the darkness descends with each progressive night, we light one more candle against the darkness.
-Rabbi Richard Jacobs