The name “Google Dance” is often used to describe the index update of the Google search engine. Google’s index update occurs on average once per month. 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. But the update does not proceed as a switch from one index to another at one point in time. In fact, it takes several days to complete the index update. During this period, the old and the new index alternate on www.google.com. At an early stage, the results from the new index occur sporadically. But later on, they appear more frequently. Google dances.