Expert: Jayendra Upadhye - 6/15/2004

Question
Hi

How long does it take the moon to travel around the earth and how do they calculate this and when was this calculation made

Thanks


Answer
Hi ilan,
The length of one lunar month (sidereal month) is 27 days 7 hours 43 minutes approximately.
This is calculated by monitoring the time taken for the moon to complete one cycle around the zodiac, taking a star as a fixed reference.
ref:
http://www.aryabhatt.com/vediclessons/vediclesson6.htm

additionally we have the symbolic month, the nodical month, the anomalistic month, each of slightly different duration.
The first accurate calculations were made by the Indian and babylonian astronomers much before the europeans!
If you find that hard to believe, but can withstand a culture shock,  please refer to the site
that describes a treatise written by aryabhatta in India wherein astronomical tables of great accuracy are detailed.
http://www.geocities.com/dipalsarvesh/aryabhatta.html
if you are still interested, you may refer to the sites
http://www.atributetohinduism.com/Hindu_Culture2.htm#Astronomy
http://www.hindunet.org/saraswati/aryan/koenraad1.html
http://www.vigyanprasar.com/dream/August2000/VPnews.htm
for detailed references.
Modern astronomers ofcourse use atomic clocks as time bases and observatories for their observations.
Jayen