Can you tell time by the Big Dipper?
My fourth grade students just read a story about the stars and constellations. It mentioned that you can tell time by using the North Star and the Big Dipper. I was perplexed and had not heard of it. Do you have any information about this?
Sure. Just like the sun, the stars rise and set; constellations near the North Star like the Big Dipper appear to circle the North Star once per day. This motion, like the sun's daily motion, is due to the Earth's rotation. Because of this motion, if you know your astronomy, then you can tell the time. When the "pointer" stars of the big dipper are directly above the North Star, it is 11:00 siderial time. When they are directly below the big dipper, it is 23:00 siderial time, etc. Unfortunately, the time told by the stars (siderial time) is slightly different than the time told by the sun (solar time), which is what we are used to using. To convert siderial time to solar time, you should add 4 minutes from the sidreial time for each day after March 21. And that's how you tell time by the stars!
Get More 'Curious?' with Our New PODCAST:
- Podcast? Subscribe? Tell me about the Ask an Astronomer Podcast
- Subscribe to our Podcast | Listen to our current Episode
- Cool! But I can't now. Send me a quick reminder now for later.
How to ask a question:
If you have a follow-up question concerning the above subject, submit it here. If you have a question about another area of astronomy, find the topic you're interested in from the archive on our site menu, or go here for help.Table 'curious.Referrers' doesn't existTable 'curious.Referrers' doesn't exist
This page has been accessed 23898 times since May 23, 2002.
Last modified: September 22, 2002 12:38:15 PM
Ask an Astronomer is hosted by the Astronomy Department at Cornell University and is produced with PHP and MySQL.
Warning: Your browser is misbehaving! This page might look ugly. (Details)