Q. when exactly does the next millennium begin?

A. The third millennium, according to the Gregorian calendar, begins on Jan. 1, 2001. But the way people count time varies from culture to culture. Other calendars operate on different times. For example, the Jewish calendar has a different new year, and different months. The Jewish calendar, according to tradition, is based on when the world is thought to have been created. During the Middle Ages, the date of creation was figured. In the Jewish calendar, the year is 5754, which puts it in the sixth millennium. The Muslim calendar is different, as is the Chinese calendar.

Q. How did the study of chemistry start?

A. The study of chemistry began in ancient times when people began to learn about fermenting foods to make beer and wine. The use of heat to cook food was also part of the process. The study continued over the years and became more sophisticatedd. By 1661, the English chemist Robert Boyle had published the Sceptical Chy-mist. However, the French chemist Antoine Laurent Lavoisier, born in 1743, is thought of as the chief founder of modern chemistry. He invented the term "oxygen" and divided chemical substances such as sulfur, carbon and phosphorous.