The Big Dipper

[ruby_silver]

Hi I'm new here and have a question. As I was browsing the gallery of photos I noticed <br />http://www.space.com/php/popup/imagegallery/noad_middle.php?imgid=3029&gid=228<br />this image. Now, I live in India (10 N and 70 E) and the Big Dipper appears to be upside down with the handle to the right instead of the left. My question is - why? Since both of the images are taken in the Northern hemisphere, shouldn't they be identical?

 

[igorsboss]

<font color="yellow">Why?</font><br />The local time of day of the observations differ by about 12 hours.<br /><br />If you observe the big dipper yourself for 12 hours, you will notice that it rotates by 180 degrees about the North pole. For example, observe it at 6PM, then again at 6 AM.<br /><br />Since the photo was taken at roughly 40N 90W, and you are at 10N 70E, I need to mention the longitude difference....<br /><br />If two observers observe the big dipper at the same lattitude and the same local time, it will look the same, regardless of lattitude.<br /><br />Local time is defined here as the time of day such that the sun is due south at 12:00 Noon. (Each observer has their own idea of "local time".) Wall clock time is a decent approximation to local time.<br /><br />If the two observers are 90+70=160 degrees of longitude apart, your local times will differ by about 14 hours at the same instant. No wonder you don't agree about the orientation...<br />

 

[ruby_silver]

Wow, thank you so much for the answers! They make a lot of sense!