Google Dance

Google Dance
The name Google Dance is a term used to describe the index update of the Google search engine. It's the period when Google is rebuilding its rankings, and results fluctuate widely for a 3 to 5 day period. It can be identified by significant movement in search results and especially by Google's cache of all indexed pages reflecting the status of Google's last spidering.

Approximately once a month, Google update their index by recalculating the Page ranks of each of the web pages that they have crawled. The period during the update is known as the Google dance.

Because of the nature of Page Rank, the calculations need to be performed about 40 times and, because the index is so large, the calculations take several days to complete. During this period, the search results fluctuate; sometimes minute-by minute. It is because of these fluctuations that the term, Google Dance, was coined. The dance usually takes place sometime during the last third of each month.

Google has two other servers that can be used for searching. The search results on them also change during the monthly update and they are part of the Google dance.

Checking the Google Dance

Until January 2004, Google had 12 main www servers online, which were as follows:

www-ex.google.com - (where you get when you type www.google.com)
www-sj.google.com - (which can also be accessed at www2.google.com)
www-va.google.com - (which can also be accessed at www3.google.com)
www-dc.google.com
www-ab.google.com
www-in.google.com
www-zu.google.com
www-cw.google.com
www-fi.google.com - found in May 2003.
www-gv.google.com - found in August 2003.
www-gv2.google.com - found in September 2003.
www-kr.google.com - found in October 2003.
At some point in January, these servers stopped accepting connections, and the only servers easy to connect to be:

www.google.com
www2.google.com
www3.google.com