Google Search Algorithm Models Cancer Spread

The equations Google employs to predict the Web pages users visit has inspired a new way to track the spread of cancer cells throughout the body.

“Each of the sites where a spreading, or “metastatic,” tumor could show up are analogous to Web pages,” said Paul Newton, a mathematician at the University of Southern California, who has been working with cancer specialists at the Scripps Research Institute.

Google ranks Web pages by the likelihood that an individual would end up visiting each one randomly. These predictions are based on the trends of millions of users across the Web. Google uses something called the "steady state distribution" to calculate the probability of someone visiting a page.

“You have millions of people wandering the Web, [and] Google would like to know what proportion are visiting any given Web page at a given time,” Newton explained.

“It occurred to me that steady state distribution is equivalent to the metastatic tumor distribution that shows up in the autopsy datasets.”