I'd like to give you a short but fascinating lesson in astronomy. Ancient civilizations have all tried to keep a record of the moon's orbit around the earth. What you may not know is that in Jewish law, this is a most fundamental topic of study. Each new moon will be the beginning of a new Jewish month, which will affect when we celebrate the holidays.
We cannotcelebrate Jewish holidays without the study of astronomy! Interestingly, this mitzvah (of studying the astronomy, anticipating the new moon and setting the calendar) is the very first mitzvah we were given as a Jewish nation - which happens to be in this week's Torah portion.
Wait till the end, you will like this.
The Talmud (written 1700 years ago) is a compilation of conversations regariding Jewish law, tradition and rulings. It records the Jewish tradition, that the synodic (visible) orbit of the moon around the earth is "29.5 days + 793 parts of an hour". Our system divides each hour by 1080 (which is divisible by many numbers, making it easy to use in all the mathematical equations).
So 793/1080 of an hour is 0.7342 of an hour. We need to know how much of a day it is, so we can add it on to the 29.5 days mentioned earlier, and get an exact calculation of the orbit.
So we divide 0.734259/24 which comes out to 0.03059. So 793 parts of an hour is 0.03059 of a full day. Let's add it to 29.5, and we have 29.53059.
I will not tell you what our super-modern technology with it's sophisticated equipment and instruments have measured. I just invite you to click here and ask Google.
Shabbat Shalom! Come over for Shabbat dinner tomorrow for more discussion on this topic.
Rabbi Mendy and Sara Alevsky
Shabbat at Chabad: Friday, 1/23 - 7:00 PM at Chabad. For directions and a map click here.